Fact-checked by Grok 2 weeks ago

Chemical process

A chemical process is a sequence of operations that converts one or more starting materials, known as reactants, into desired products through chemical reactions, often combined with physical steps such as mixing, heating, or separation, utilizing specialized equipment and controlled conditions to achieve efficient transformation on scales ranging from laboratory to industrial.^[1]^[2] In essence, chemical processes distinguish themselves from purely physical processes by involving the breaking and forming of chemical bonds, resulting in the creation of new substances with different molecular structures, as evidenced by observable changes like color shifts, gas evolution, or temperature variations.^[2]^[3] These processes adhere to the law of conservation of mass, ensuring that the total mass of reactants equals that of products, with no matter created or destroyed during the transformation.^[2] Chemical processes are broadly categorized into batch and continuous types; batch processes handle materials in discrete sequences within a single unit of equipment, suitable for small-scale or variable production, while continuous processes maintain steady material flow through interconnected units for high-volume, uninterrupted output.^[1] They operate under steady-state conditions, where variables like temperature and flow rates remain constant, or unsteady-state conditions involving time-dependent changes, and typically incorporate unit operations such as reactors for reactions, heat exchangers for energy transfer, and separators for product isolation.^[1] The applications of chemical processes span numerous industries, including the production of pharmaceuticals, where they enable the synthesis of active ingredients through scalable reaction sequences; petrochemical manufacturing, converting feedstocks like crude oil into fuels and plastics; and materials fabrication, involving etching, cleaning, and deposition for semiconductors and devices.^[4]^[5]^[6] In environmental contexts, they facilitate processes like carbon dioxide conversion to methanol for fuels and sustainable feedstocks.^[5] Chemical processes underpin modern society by enabling the creation of essential goods, from everyday items like preserved foods and synthetic fabrics to advanced technologies, while the chemical industry itself ranks as the third-largest source of industrial greenhouse gas emissions and the largest industrial energy consumer, driving ongoing innovations in efficiency, sustainability, and electrification to mitigate environmental impacts.^[7]^[8]^[9]

Definition and Fundamentals

Definition and Scope

A chemical process is defined as a method involving one or more steps that convert starting materials, or raw materials, into desired products through chemical reactions, physical transformations, or biological changes, utilizing specific equipment, systems, and operating conditions to facilitate the conversion.^[1] This encompasses the integration of unit operations—such as reactors for reactions, mixers for blending, and separators for isolation—within a cohesive framework to achieve efficient production.^[1] In the context of chemical engineering, chemical processes distinguish themselves from pure laboratory synthesis by emphasizing large-scale implementation, where processes are designed for industrial viability rather than small-batch experimentation.^[10] The scope of chemical processes extends to the design, operation, and optimization of systems that handle the transformation of molecular structures into usable commodities, often spanning multiple interconnected steps to ensure product purity and yield.^[11] This includes both reactive steps, where chemical bonds are formed or broken, and non-reactive unit operations that support overall efficiency, such as heating, cooling, or filtration.^[1] Unlike isolated chemical reactions studied in basic chemistry, chemical processes in engineering incorporate broader system integration, accounting for interactions between components to produce outputs at commercial volumes.^[10] Key characteristics of chemical processes include the fundamental involvement of mass and energy transfer, which govern the movement of materials and heat throughout the system to drive transformations.^[1] Scalability is essential, as processes must be adaptable from laboratory prototypes to industrial facilities, where factors like flow rates and heat exchange can vary significantly with size.^[10] Economic viability further defines their scope, requiring designs that balance production costs, energy efficiency, and resource use to ensure profitability in real-world applications.^[10] These processes are governed by thermodynamic principles that dictate feasibility and efficiency, though detailed analysis falls under specialized kinetic and energetic frameworks.^[11] Representative examples within this scope include the conversion of petroleum feedstocks into fuels through distillation and cracking operations, which integrate physical separations with catalytic reactions to yield gasoline and diesel.^[10] Similarly, the synthesis of pharmaceuticals, such as antibiotics via fermentation followed by purification, exemplifies how chemical processes combine biological reactions with downstream unit operations to produce high-purity therapeutic agents at scale.^[10]

Historical Development

The origins of chemical processes trace back to ancient civilizations, where rudimentary techniques laid the groundwork for later developments. Fermentation, one of the earliest known processes, was utilized as far back as approximately 5000 BCE for producing beer in Mesopotamia and around 7000 BCE for mixed fermented beverages in ancient China, relying on natural microorganisms to convert sugars into alcohol and carbon dioxide.^[12]^[13]^[14] Distillation emerged around 3500 BCE in Mesopotamia, with archaeological evidence of apparatus used to separate liquids, initially for perfumes and essential oils rather than alcohol.^[15] Proto-alchemical practices in ancient Mesopotamia and Egypt, dating back to around 2000 BCE, involved techniques such as smelting, alloying, and early distillation to purify materials. Alchemy as a systematic discipline emerged in Hellenistic Egypt around the 3rd century CE, influencing Greek philosophy and later developments in metallurgy and pharmacology.^[16] The Industrial Revolution catalyzed the shift from artisanal to large-scale chemical production. In 1746, John Roebuck developed the lead chamber process for sulfuric acid manufacturing, replacing inefficient glass globe methods pioneered by Joshua Ward in the 1740s and enabling cost-effective production for dyes, fertilizers, and explosives.^[17] This was followed in 1791 by Nicolas Leblanc's invention of the Leblanc process, which converted common salt into soda ash (sodium carbonate) through a series of reactions involving sulfuric acid and limestone, revolutionizing industries like glassmaking and soap production despite its environmental drawbacks.^[18] The 20th century brought transformative advancements in scale and efficiency. The Haber-Bosch process, developed by Fritz Haber in 1909 and industrially scaled by Carl Bosch at BASF in 1913, synthesized ammonia from nitrogen and hydrogen under high pressure and temperature, addressing global fertilizer needs and supporting agriculture for billions.^[19] Post-1920s, petrochemical processes emerged with the first commercial production of isopropyl alcohol from petroleum in 1920 at Standard Oil's Bayway plant, followed by ethylene cracking, fueling the growth of plastics, synthetic rubbers, and detergents from abundant oil feedstocks.^[20] The 1940s marked the rise of continuous processing, exemplified by wartime innovations like fluidized-bed catalytic cracking for gasoline and petrochemicals, which replaced batch methods with steady-state operations for higher throughput and reliability.^[21] Key figures shaped chemical engineering as a discipline. George E. Davis, often called the father of chemical engineering, published A Handbook of Chemical Engineering in 1901, formalizing the field through systematic analysis of industrial practices.^[22] Davis introduced the unit operations concept, breaking down complex processes into fundamental steps like distillation and filtration, which became central to education and design.^[23]

Core Principles

Thermodynamic and Kinetic Bases

The thermodynamic foundations of chemical processes are rooted in the first and second laws of thermodynamics, which govern energy conservation and the directionality of spontaneous changes, respectively. The first law states that energy is conserved in any process, expressed as the change in internal energy ΔU equaling the heat added to the system q plus the work done on the system w, or ΔU = q + w. This principle ensures that energy transformations in chemical processes, such as heat absorption or release during reactions, maintain overall balance without creation or destruction of energy. The second law introduces entropy S as a measure of disorder, asserting that for any spontaneous process in an isolated system, the total entropy increases, ΔS > 0, which dictates the feasibility and efficiency of processes like mixing or heat transfer in industrial operations.^[24]^[25] Central to assessing process spontaneity at constant temperature and pressure is the Gibbs free energy G, defined by the relation ΔG = ΔH - TΔS, where ΔH is the enthalpy change (reflecting heat content at constant pressure), T is the absolute temperature, and ΔS is the entropy change. A negative ΔG (ΔG < 0) indicates a spontaneous process under these conditions, as it represents the maximum reversible work available from the system, guiding the prediction of reaction favorability in chemical engineering designs. Enthalpy and entropy contributions often compete: exothermic reactions (ΔH < 0) favor spontaneity, while increased disorder (ΔS > 0) enhances it, particularly at higher temperatures.^[26]^[27] Phase equilibria in chemical processes describe the distribution of components between phases, such as liquid-vapor or gas-liquid interfaces, essential for operations involving distillation or absorption. For ideal solutions, Raoult's law posits that the partial vapor pressure of a component i is proportional to its mole fraction x_i in the liquid phase, given by P_i = x_i P_i^sat, where P_i^sat is the saturation vapor pressure of pure i; this assumes no intermolecular interactions beyond those in the pure components, enabling ideal behavior predictions for binary mixtures like benzene-toluene. Deviations occur in non-ideal systems, but Raoult's law provides a baseline for equilibrium calculations in process simulations.^[28] For dilute gas-liquid systems, Henry's law complements Raoult's by relating the solubility of a gas to its partial pressure, expressed as C = k_H P, where C is the concentration in the liquid, P is the partial pressure, and k_H is the Henry's law constant (specific to the gas-solvent pair and temperature). This law applies when the solute is sparingly soluble, as in oxygen dissolution in water, and is crucial for processes like gas absorption towers where equilibrium drives mass transfer rates. The constant k_H decreases with temperature for most gases, reflecting reduced solubility at higher temperatures.^[29] Chemical kinetics underpins the rate at which processes occur, distinct from thermodynamic spontaneity by focusing on timescales. Reaction rates are typically expressed through rate laws, where for an elementary reaction, the rate is proportional to the product of reactant concentrations raised to their stoichiometric coefficients, such as rate = k [A]^m [B]^n for a reaction mA + nB → products; here, k is the rate constant, dependent on temperature and mechanism. Elementary reactions represent single-step collisions, with rate laws directly mirroring molecularity, unlike complex mechanisms requiring experimental determination.^[30] The temperature dependence of the rate constant is captured by the Arrhenius equation:

k = A e^{-E_a / RT}

where A is the pre-exponential factor (related to collision frequency and orientation), E_a is the activation energy (the minimum energy barrier for effective collisions), R is the gas constant, and T is temperature in Kelvin. Higher E_a values slow reactions at a given temperature, as fewer molecules surmount the barrier; for instance, doubling temperature often increases rates by factors of 2-4 for typical E_a around 50 kJ/mol. Activation energy quantifies kinetic barriers, influencing process selectivity and yields.^[31] Catalysts accelerate chemical processes by lowering the activation energy E_a through alternative pathways, without being consumed, thereby increasing rates while preserving thermodynamics. Homogeneous catalysts operate in the same phase as reactants (e.g., acid catalysts in solution), offering uniform interaction but complicating separation; they reduce E_a by stabilizing transition states via coordination or proton transfer. Heterogeneous catalysts, typically solids contacting fluid reactants (e.g., platinum in automotive exhausts), function at interfaces, lowering E_a through adsorption that weakens bonds; their surface area and porosity enhance efficacy, though mass transfer limitations can arise. Both types boost industrial efficiency, with heterogeneous forms dominating large-scale processes due to easier recovery.^[32]^[33]

Stoichiometry and Material Balance

Stoichiometry forms the foundation for quantifying the relationships between reactants and products in chemical processes, ensuring that chemical equations are balanced according to the law of conservation of mass. Stoichiometric coefficients represent the relative molar amounts of substances involved in a reaction, derived by balancing the equation to equalize atoms on both sides. For instance, in the combustion of octane, the balanced equation is \ce{C8H18 + 12.5 O2 -> 8 CO2 + 9 H2O}, where the coefficients indicate that 1 mole of octane reacts with 12.5 moles of oxygen to produce 8 moles of carbon dioxide and 9 moles of water.^[34] These coefficients enable the calculation of required input quantities and expected outputs, critical for process design and efficiency.^[35] Material balances in chemical processes apply the principle of mass conservation, tracking the flow of mass through systems to predict performance and optimize operations. The general material balance equation for a system is:

\text{Input} + \text{Generation} = \text{Output} + \text{Consumption} + \text{Accumulation}

where input and output refer to mass flows entering and leaving the system, generation and consumption account for mass created or depleted by reactions, and accumulation represents changes in inventory over time.^[36] In steady-state processes, such as continuous reactors operating at constant conditions, accumulation is zero, simplifying the equation to \text{Input} + \text{Generation} = \text{Output} + \text{Consumption}.^[37] This framework allows engineers to solve for unknown stream compositions or flow rates, ensuring no mass is unaccounted for in the process.^[36] Yield and selectivity are key metrics for evaluating the efficiency of chemical reactions within processes, distinguishing between overall conversion and the preference for desired products. Yield is defined as the ratio of the actual amount of desired product obtained to the theoretical maximum based on the limiting reactant, often expressed as a percentage. Selectivity measures the fraction of converted reactants that form the desired product versus byproducts, calculated as the moles of desired product divided by the total moles of products from the reaction.^[38] These metrics guide process improvements by highlighting inefficiencies, such as side reactions that reduce selectivity. Atom economy extends these concepts by assessing the incorporation of reactant atoms into the final product, promoting greener process design. Introduced by Barry Trost, atom economy is the percentage of reactant atoms present in the desired product, calculated as \frac{\text{molecular weight of desired product}}{\sum \text{molecular weights of all products}} \times 100.^[39] High atom economy indicates minimal waste from unused atoms, contrasting with traditional yield which ignores byproducts.^[39] For example, in ideal addition reactions, atom economy approaches 100%, while substitution reactions often yield lower values due to discarded atoms.^[39] The E-factor complements atom economy by quantifying waste generation, defined as the mass of waste produced per mass of desired product. Developed by Roger Sheldon, the E-factor is calculated as \frac{\text{total waste mass}}{\text{product mass}}, encompassing all byproducts, solvents, and auxiliary materials.^[40] Lower E-factors signify more sustainable processes; for bulk chemicals, typical values are below 1, while fine chemicals may exceed 25 due to complex syntheses.^[40] This metric has driven industry-wide reductions in waste through process intensification and catalyst improvements.^[40] Recycle streams are integral to material balances in closed-loop chemical processes, where unreacted materials or byproducts are returned to earlier stages to enhance resource utilization. In balance calculations, recycle flows are treated as internal streams that augment inputs without adding to fresh feed, requiring iterative solutions or overall system balances to determine flow rates.^[41] For a reactor with recycle, the material balance around the entire system equates fresh feed plus recycle to products plus purge, preventing accumulation of inerts.^[42] This approach improves yield and selectivity by maximizing reactant exposure, common in ammonia synthesis where unreacted gases are recycled to achieve near-complete conversion.^[42]

Types of Processes

Batch Processes

Batch processes in chemical engineering involve the production of finite quantities of material, known as batches, through a predefined sequence of discrete operations that convert raw materials into final products.^[43] These processes are characterized by their intermittent nature, operating under unsteady-state conditions where reactants are charged into a reactor, allowed to react over a specified time, and then discharged, with distinct phases including charging, reacting, and emptying.^[44] Fixed-volume reactors are typically employed, enabling sequential steps that facilitate precise control over reaction conditions such as temperature, pressure, and mixing, making them suitable for small-scale or variable production demands.^[45] Key advantages of batch processes include their flexibility in handling multiple recipes or product variations using the same equipment, which is ideal for custom or low-volume manufacturing, and their ability to achieve high conversions through extended reaction times.^[44] They also offer easier cleaning between runs and simpler implementation for reactions prone to side products, as each batch can be isolated and monitored individually.^[43] However, disadvantages encompass significant downtime for charging, discharging, and cleaning, which reduces overall productivity; higher labor requirements due to manual oversight; and challenges in scaling to large volumes without efficiency losses.^[44] Compared to continuous processes, batch operations are less suited for high-throughput steady-state production but excel in adaptability.^[43] Common equipment for batch processes includes stirred-tank reactors, often equipped with jackets or coils for heating and cooling to maintain precise thermal control during reaction cycles.^[44] These vessels may incorporate agitators for uniform mixing, ports for adding reactants or removing products, and sometimes autoclave designs for high-pressure applications exceeding 5,000 psi.^[44] Ancillary components such as pumps, valves, and fermentors support the sequential operations, ensuring safe handling of materials in pharmaceutical or fine chemical settings.^[43] Representative examples of batch processes include the synthesis of pharmaceuticals, where reactors facilitate steps like crystallization and purification for active ingredients, allowing rapid adaptation to new formulations under patent constraints.^[43] In polymer production, batch reactors are used for specialty resins, enabling customization of molecular weight and properties through controlled polymerization cycles.^[46] Other applications encompass fine chemical manufacturing, such as dyes or agrochemicals, and biotech processes like fermentation for antibiotics, all benefiting from the discrete control inherent to batch methods.^[43]

Continuous and Semi-Continuous Processes

Continuous processes in chemical engineering involve the uninterrupted flow of reactants into a system and the continuous withdrawal of products, enabling steady-state operation where key variables such as temperature, pressure, and concentrations remain constant over time.^[1] This mode contrasts with discrete operations by minimizing downtime and allowing for prolonged, efficient production without periodic shutdowns for loading or unloading.^[47] In steady-state conditions, the input and output rates balance, supporting scalable industrial applications where material flows through multiple unit operations sequentially.^[1] Semi-continuous processes blend elements of continuous and batch systems, featuring ongoing reaction with periodic interventions, such as the addition of feeds or removal of products.^[48] A prominent example is fed-batch fermentation, where nutrients are intermittently supplied to a bioreactor to sustain microbial growth while avoiding substrate inhibition, with the volume increasing over the cycle until harvesting occurs at the end.^[49] This approach achieves higher yields in biotechnological applications by maintaining optimal conditions dynamically, though it operates transiently rather than at full steady state.^[49] Continuous and semi-continuous processes offer advantages including elevated throughput for large-scale production, enhanced automation for precise control, and uniform product quality due to stable operating conditions.^[50] These benefits make them ideal for bulk chemicals, where uninterrupted operation reduces labor and variability compared to batch methods.^[47] However, they require substantial upfront capital for specialized equipment and infrastructure, and offer limited flexibility for switching product formulations without major reconfiguration.^[50] Key equipment for continuous processes includes the continuous stirred-tank reactor (CSTR), which maintains perfect mixing and uniform conditions throughout the vessel under steady-state flow, ideal for reactions needing consistent exposure to reactants.^[51] In contrast, the plug flow reactor (PFR) facilitates axial progression of reactants with minimal back-mixing, simulating a series of infinitesimal batch reactions in steady-state operation for processes requiring concentration gradients.^[51] Representative examples include petroleum refining, where crude oil undergoes continuous thermal and catalytic operations like cracking and distillation to yield fuels and petrochemicals on a massive scale.^[52] Similarly, the Haber-Bosch process synthesizes ammonia continuously by circulating nitrogen and hydrogen over an iron catalyst in a high-pressure loop, recycling unreacted gases, with the process accounting for approximately 90% of global ammonia production as of 2025.^[53]^[54]

Unit Operations

Transport Phenomena

Transport phenomena encompass the fundamental mechanisms governing the transfer of momentum, heat, and mass within chemical processes, serving as the cornerstone for designing reactors, heat exchangers, and separation equipment in chemical engineering. These processes describe how fluids move, how temperature gradients drive energy flow, and how concentration differences lead to species migration, all of which are essential for predicting system behavior under various operating conditions. The unified framework of transport phenomena, pioneered in the mid-20th century, integrates these transfers through analogous mathematical descriptions, enabling engineers to scale laboratory findings to industrial applications. Momentum transfer, or the study of fluid dynamics, is central to understanding flow patterns in pipes, pumps, and stirred vessels used in chemical processing. The Navier-Stokes equations provide the governing partial differential equations for viscous, incompressible flow, simplifying to the form \rho \left( \frac{\partial \mathbf{v}}{\partial t} + \mathbf{v} \cdot \nabla \mathbf{v} \right) = -\nabla p + \mu \nabla^2 \mathbf{v} + \mathbf{f} under typical assumptions of Newtonian fluids and negligible body forces, where \rho is density, \mathbf{v} is velocity, p is pressure, \mu is viscosity, and \mathbf{f} represents external forces. For steady, fully developed laminar flow in a circular pipe, these reduce to the Hagen-Poiseuille equation, yielding a parabolic velocity profile with maximum velocity at the centerline. In turbulent regimes, which dominate many industrial flows, eddy diffusion enhances momentum transport beyond molecular viscosity. The Reynolds number, defined as \mathrm{Re} = \frac{\rho v d}{\mu}, where v is average velocity and d is characteristic length, quantifies the transition from laminar (\mathrm{Re} < 2100) to turbulent flow (\mathrm{Re} > 4000) in pipes, guiding equipment sizing to minimize pressure drops and ensure uniform mixing.^[55] Heat transfer in chemical processes involves conduction through solids or stagnant fluids, convection in flowing systems, and radiation in high-temperature operations, with conduction and convection being primary in most unit operations. Fourier's law describes steady-state conduction as the heat flux q = -k \frac{dT}{dx}, where k is the thermal conductivity and \frac{dT}{dx} is the temperature gradient, originally derived for isotropic materials in 1822.^[56] Convection, driven by fluid motion, follows Newton's law of cooling, stating that the convective heat flux is q = h (T_s - T_\infty), with h as the convective heat transfer coefficient and T_s, T_\infty as surface and bulk fluid temperatures, respectively; this empirical relation holds for low temperature differences and was formalized in heat transfer contexts from Newton's early 1701 observations.^[57] In composite systems like heat exchanger walls, the overall heat transfer coefficient U combines these effects via \frac{1}{U} = \frac{1}{h_i} + \frac{\Delta x}{k} + \frac{1}{h_o}, where subscripts i and o denote inside and outside, enabling calculation of total heat duty Q = U A \Delta T_m for design purposes. Mass transfer governs the diffusion and convection of species in separations and reactions, crucial for processes like distillation and absorption. Fick's first law posits that the diffusive flux J = -D \frac{dc}{dx} is proportional to the concentration gradient \frac{dc}{dx}, with D as the diffusion coefficient, analogous to Fourier's law and established in 1855 for dilute solutions.^[58] Fick's second law extends this to unsteady diffusion: \frac{\partial c}{\partial t} = D \frac{\partial^2 c}{\partial x^2}, describing concentration evolution over time in batch systems. In convective mass transfer, such as gas-liquid contacting, the flux is N = k_c (c_s - c_b), where k_c is the mass transfer coefficient and c_s, c_b are surface and bulk concentrations; these coefficients, determined experimentally or via correlations, are vital for sizing packed columns in separations.^[59] The interrelations among momentum, heat, and mass transfer arise from their shared dependence on fluid velocity and boundary layers, formalized through analogies that link their dimensionless coefficients. The Chilton-Colburn analogy, developed in 1934, equates the Stanton numbers for heat and mass transfer to the friction factor: j_H = \frac{h}{\rho v c_p} \mathrm{Pr}^{2/3} = j_M = \frac{k_c}{v} \mathrm{Sc}^{2/3} = \frac{f}{2}, where \mathrm{Pr} is the Prandtl number, \mathrm{Sc} is the Schmidt number, and f is the Fanning friction factor; this relation, valid for turbulent pipe and boundary layer flows, allows prediction of one transfer rate from measurements of another, reducing experimental needs in process design.

Separation and Purification Operations

Separation and purification operations constitute a cornerstone of chemical engineering, enabling the isolation of target products from complex mixtures by leveraging differences in phase behavior, solubility, and surface affinity. These processes are integral to industries such as petrochemicals, pharmaceuticals, and food production, where achieving high purity is critical for product quality and downstream processing efficiency. Unlike reactive operations, they focus on physical separations without altering molecular structure, often guided by equilibrium thermodynamics and mass transfer rates. Distillation stands as the predominant technique for separating liquid mixtures based on vapor-liquid equilibrium (VLE), exploiting variations in component volatilities to produce streams enriched in lighter or heavier fractions. VLE principles dictate that at equilibrium, the vapor composition is richer in more volatile components than the liquid, as described by phase rules and activity coefficient models for non-ideal systems.^[60] For binary mixtures, the McCabe-Thiele method offers a graphical framework for column design, plotting the equilibrium curve against operating lines for the rectifying and stripping sections to visually determine the minimum and actual number of theoretical trays needed for specified separations.^[61] This approach assumes constant molar overflow and ideal stage efficiency, facilitating rapid assessment of design parameters like feed location. The reflux ratio, defined as the moles of condensed vapor returned to the column per mole of distillate product, directly influences separation sharpness; increasing it steepens the operating line, enhancing purity but elevating energy demands for vaporization and condensation.^[61] Liquid-liquid extraction provides an alternative for thermally sensitive or close-boiling mixtures, relying on partitioning of the solute between two immiscible phases to achieve selective transfer. The underlying liquid-liquid partitioning follows the Nernst distribution law, which posits that at equilibrium, the solute concentration ratio between the organic and aqueous phases remains constant, independent of initial solute amount, for dilute solutions.^[62] This ratio, known as the distribution coefficient D = \frac{C_{\text{organic}}}{C_{\text{aqueous}}}, quantifies selectivity and guides process feasibility. Solvent selection hinges on maximizing D for the target solute while minimizing co-extraction of impurities and ensuring phase disengagement; immiscible solvents like hexane for non-polar solutes or ethyl acetate for moderately polar ones are chosen based on empirical D values and mutual solubility data.^[63] Filtration and centrifugation address solid-liquid separations by mechanically isolating suspended solids from slurries, crucial for clarifying liquids or recovering solids in processes like crystallization or precipitation. In filtration, the slurry is forced through a porous medium under pressure or vacuum, depositing a permeable cake that retains solids while filtrate passes through; cake filtration theory models this as flow through a gradually thickening resistance layer. Developed by Ruth in 1935, the theory integrates Darcy's law to express filtration rate as inversely proportional to cake thickness and specific resistance \alpha, with permeability k = 1/(\rho_s (1 - \epsilon) \alpha) characterizing the cake's void structure and compressibility, where \rho_s is solid density and \epsilon is porosity. Centrifugation enhances this by substituting centrifugal acceleration \omega^2 r (where \omega is angular velocity and r radius) for gravity, promoting rapid sedimentation of denser solids toward the bowl wall in continuous decanters or batch machines, ideal for high-solids slurries.^[64] Adsorption and chromatography exploit surface interactions to separate solutes via reversible binding to a stationary phase, offering high selectivity for trace impurities or complex mixtures. In adsorption, molecules adhere to heterogeneous solid surfaces through physical or chemical forces until sites saturate, with equilibrium described by isotherms that relate uptake to concentration. The Langmuir isotherm models monolayer adsorption on uniform sites, expressed as

q = \frac{q_m K C}{1 + K C}

where q is adsorbed amount, q_m maximum capacity, K affinity constant, and C equilibrium concentration; derived by Langmuir in 1918, it assumes no adsorbate interactions and site independence, fitting well for gas-solid or liquid-solid systems like activated carbon purification.^[65] Chromatography builds on this by percolating a mobile phase through an adsorbent bed, eluting components at rates inversely proportional to their surface affinity, enabling preparative or analytical resolutions in techniques like affinity or ion-exchange variants.^[66]

Design and Modeling

Process Flow and Simulation

Block flow diagrams (BFDs) provide a high-level overview of chemical processes, representing major unit operations or sections of a plant as simple blocks connected by material streams. These diagrams simplify the basic structure of a system, using rectangles or blocks for equipment and straight lines with arrows to indicate flow directions, typically from left to right. BFDs are essential in the early stages of process design to compare alternatives, outline overall material balances, and communicate concepts to non-specialists, serving as a precursor to more detailed representations. For instance, in benzene production from toluene and hydrogen, a BFD might depict feed streams entering a reactor block, followed by separation blocks, without specifying internal equipment details.^[67]^[68] Process flow diagrams (PFDs) build upon BFDs by offering a more detailed mapping of the process, illustrating the sequence of equipment, piping, and control instruments. Standard symbols standardize representation: pumps are shown as circles with internal triangles, reactors as vertical cylinders, and heat exchangers as paired horizontal lines or ovals. Streams are numbered and annotated with key parameters, including mass or molar flow rates (e.g., kg/h or kmol/h), compositions (e.g., mole fractions of components like hydrogen or methane), temperatures (°C), and pressures (bar), enabling material and energy balance calculations. PFDs exclude minor details like valve sizes but focus on major flows to guide engineering design and operation.^[69]^[70] Simulation software facilitates the modeling of these flow diagrams by solving interconnected unit operations numerically. Aspen Plus, a leading tool for steady-state simulation, enables the construction of flowsheets for chemical processes, incorporating thermodynamic models to predict behavior under constant conditions, such as in bulk chemical production. It supports rigorous calculations for reactors, separators, and streams, integrating economic and energy analyses. Similarly, Aspen HYSYS specializes in oil and gas applications but extends to general processes, offering intuitive interfaces for steady-state modeling of dynamic-like systems through hybrid AI models. Both tools primarily employ sequential modular approaches, where unit operations are solved iteratively in sequence, with convergence achieved via methods like Wegstein or Broyden for recycle loops to ensure stable solutions. Equation-oriented methods, solving all equations simultaneously, are also available for complex flowsheets to improve efficiency.^[71]^[72]^[73] Integration in process flows links unit operations through features like recycle loops and heat exchangers to enhance efficiency and close material balances. Recycle loops return streams (e.g., unreacted feed from a separator back to a reactor) to upstream units, represented in PFDs by backward arrows, requiring iterative convergence in simulations to resolve interdependent calculations. Heat exchangers, depicted as dedicated symbols, transfer heat between process streams or utilities, often integrated within loops to preheat feeds and minimize energy use; for example, column bottoms may heat incoming streams before recycling. This connectivity demands careful initial estimates, such as pressure drops of 0.3-0.7 bar, to aid simulator convergence and reflect real plant interactions.^[74]^[69]

Scale-Up and Optimization

Scale-up in chemical engineering involves translating laboratory-developed processes to larger, industrial-scale operations while preserving performance characteristics such as reaction rates, yields, and product quality. This transition requires careful application of similarity principles to account for changes in physical phenomena like fluid dynamics and heat transfer, which behave differently at varying scales due to nonlinear relationships in equipment geometry and operating conditions. Successful scale-up minimizes risks of inefficiencies or failures by integrating experimental data, modeling, and iterative testing across development stages. Geometric similarity ensures that all linear dimensions of the process equipment are scaled proportionally, maintaining ratios such as length-to-diameter (L/d) between lab and production scales; this is foundational for consistent spatial flow patterns in reactors and mixers. Kinematic similarity extends this by requiring identical velocity profiles and streamlines, typically achieved by matching the Reynolds number (Re = ρ v L / μ, where ρ is density, v is velocity, L is characteristic length, and μ is viscosity), which governs the transition between laminar and turbulent flow regimes critical in mixing and pipe flow applications. Dynamic similarity balances forces such as inertia, viscosity, and gravity, often through dimensionless groups like the Froude number (Fr = v² / (g L)) for gravity-influenced processes such as bubble columns, ensuring equivalent power inputs and transfer rates across scales. In practice, full similarity across all three is rarely attainable simultaneously due to conflicting requirements, such as fixed catalyst particle sizes in packed-bed reactors that violate geometric scaling.^[75] Dimensionless numbers facilitate scale-up by providing scale-invariant correlations for key phenomena; for instance, the Power number (N_p = P / (ρ N³ D⁵), where P is power, N is rotational speed, and D is impeller diameter) is used in agitated vessels to maintain consistent mixing energy input per unit volume under turbulent conditions (Re > 10,000), allowing prediction of power requirements for larger tanks without exhaustive retesting. These numbers, derived from Buckingham's Pi theorem, enable engineers to extrapolate lab data to production scales for operations like emulsification and heat exchange, where the Nusselt number (Nu = h D / k, with h as heat transfer coefficient and k as thermal conductivity) correlates convective heat transfer to flow conditions.^[76] Optimization techniques refine scaled processes by systematically adjusting variables to meet performance goals. Objective functions quantify trade-offs, such as minimizing total annualized costs (capital plus operating) or maximizing yield, often formulated as linear or nonlinear expressions; for example, in reactor design, yield might be optimized as a function of reactant ratios to achieve up to 88.8% conversion under material balance constraints. Linear programming (LP) addresses problems with linear objectives and constraints using methods like the simplex algorithm, which iteratively navigates feasible regions to find optimal solutions at vertices, as applied in refinery blending to maximize profit from crude allocation subject to supply and demand limits. For multivariable, nonlinear challenges like heat exchanger networks, genetic algorithms employ evolutionary principles—population initialization, crossover, and mutation—to explore global optima, outperforming gradient-based methods in nonconvex landscapes such as batch scheduling or separation sequence synthesis.^[77] Challenges in scale-up arise primarily from heat and mass transfer limitations, as surface area-to-volume ratios decrease with size, reducing cooling efficiency and leading to hotspots or incomplete reactions; for instance, a 500-fold volume increase can alter exotherm management, necessitating enhanced agitation or staged cooling to maintain kinetics. Mass transfer rates similarly decline, impacting multiphase reactions where diffusion paths lengthen, often requiring Reynolds number adjustments to sustain turbulence. These issues are addressed through piloting stages: bench-scale experiments (e.g., in beakers) validate basic chemistry and properties; pilot-scale facilities (1-1000 times lab volume) integrate unit operations for process simulation and hazard identification; and full-scale demonstration confirms economic viability before commercial rollout, with each stage building data for refinement.^[78]^[79]^[80] Economic optimization balances capital costs (e.g., equipment fabrication, estimated at $251 million for a mid-sized plant) against operating costs (e.g., $117 million annually for raw materials and utilities), using net present value (NPV) to evaluate long-term profitability. NPV is calculated as the sum of discounted cash flows over the project life: NPV = Σ [ (Revenue - Costs - Depreciation) / (1 + r)^t ] - Initial Investment, where r is the minimum acceptable rate of return (e.g., 12%) and t is time in years; positive NPV indicates viability, as seen in process designs yielding $18.65 million annual profit after sensitivity analysis on variables like utility consumption. This approach prioritizes configurations that minimize equivalent annual operating costs while maximizing returns, guiding decisions in areas like insulation thickness or reactor sizing.^[81]^[77]

Safety and Sustainability

Risk Assessment and Control

Risk assessment in chemical processes involves systematic methods to identify potential hazards and evaluate their likelihood and consequences, ensuring proactive mitigation to prevent accidents. One primary technique is the Hazard and Operability Study (HAZOP), a structured qualitative method that examines process deviations using guide words such as "no," "more," or "less" applied to parameters like flow, temperature, and pressure during team-based reviews of piping and instrumentation diagrams (P&IDs).^[82] Developed in the 1970s by Imperial Chemical Industries (ICI), HAZOP helps uncover operability issues and safety risks early in design or operation.^[83] Complementing HAZOP, Fault Tree Analysis (FTA) employs a deductive, top-down graphical approach to model the logical pathways leading to a specific undesired event, such as a reactor overpressure, using Boolean logic gates to quantify failure probabilities.^[84] FTA is particularly valuable in chemical plants for tracing root causes from component failures to system-level risks, often integrated with quantitative risk assessments.^[85] Inherent safety principles prioritize eliminating or reducing hazards at the source rather than relying on add-on controls, fundamentally altering process design to enhance safety. The core principles, as articulated by Trevor Kletz, include minimize, which reduces the quantities of hazardous materials or the scale of operations; substitute, replacing toxic or reactive substances with less dangerous alternatives, such as using water-based solvents instead of flammable organics; and moderate, operating under less severe conditions like lower temperatures or pressures to limit reaction energies.^[86] These principles guide engineers to avoid hazards inherently, for instance, by miniaturizing equipment inventories to limit potential release volumes.^[87] Control measures in chemical processes implement engineered safeguards to detect and respond to deviations, maintaining operations within safe limits. Safety Instrumentation Systems (SIS) consist of independent sensors, logic solvers, and actuators that monitor critical parameters and automatically initiate protective actions, such as isolating a vessel, to achieve a safe state.^[88] Pressure relief valves serve as passive devices that open at preset thresholds to vent excess pressure, preventing vessel rupture in scenarios like thermal expansion or runaway reactions.^[89] Emergency shutdown systems (ESD) provide rapid, automated isolation of process sections by closing valves or stopping equipment upon detecting abnormalities, minimizing escalation of incidents like leaks or fires.^[90] Historical incidents underscore the critical need for robust risk assessment and controls. The 1984 Bhopal disaster at a Union Carbide pesticide plant in India resulted from a process failure involving water ingress into a methyl isocyanate (MIC) storage tank, leading to an exothermic reaction and the release of approximately 40 tons of toxic gas that killed over 3,800 people immediately; inadequate hazard identification, such as unaddressed refrigeration system failures and poor maintenance of safety interlocks, exacerbated the runaway reaction.^[91] Similarly, the 1974 Flixborough explosion at a Nypro UK chemical plant occurred due to a ruptured 20-inch temporary bypass pipe in a cyclohexane oxidation process, releasing a massive vapor cloud that ignited, killing 28 and injuring 36; the failure stemmed from insufficient engineering analysis of the modification and lack of pressure relief capacity, highlighting deficiencies in change management and operability studies.^[92] These events have driven widespread adoption of HAZOP and inherent safety in industry standards.

Environmental and Regulatory Aspects

Chemical processes generate significant environmental impacts, including air emissions, wastewater discharge, and greenhouse gas (GHG) releases, necessitating robust pollution control measures to minimize ecological harm. Emission standards regulate the release of volatile organic compounds (VOCs), particulate matter, and hazardous air pollutants from chemical manufacturing facilities, often enforced through permitting systems that require technologies like scrubbers, catalytic converters, and vapor recovery units to capture and treat effluents before discharge. In wastewater management, the activated sludge process serves as a widely adopted biological treatment method, where aerobic microorganisms in an aeration basin degrade organic pollutants from chemical effluents, achieving up to 90% removal of biochemical oxygen demand (BOD) under optimal conditions, followed by clarification to separate treated water from sludge. GHG mitigation strategies in the chemical sector focus on process optimizations such as energy efficiency improvements, carbon capture and storage (CCS), and feedstock shifts to renewables, which have contributed to reductions in industry-wide emissions intensity.^[93] Regulatory frameworks worldwide impose stringent requirements on chemical processes to safeguard human health and the environment. In the European Union, the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) regulation, effective from June 1, 2007, mandates that manufacturers and importers register substances produced or imported in volumes over one tonne annually, evaluate their risks, and seek authorization for those of very high concern, thereby promoting safer chemical alternatives.^[94] In the United States, the Toxic Substances Control Act (TSCA) of 1976 empowers the Environmental Protection Agency (EPA) to assess and control chemical substances posing unreasonable risks, requiring pre-manufacture notices for new chemicals and ongoing reporting for existing ones to track potential environmental hazards. The Clean Air Act, through its 1990 amendments, established national ambient air quality standards and introduced market-based programs like cap-and-trade for acid rain precursors, significantly curbing sulfur dioxide emissions from chemical plants by over 90% since implementation.^[95] Sustainability metrics provide quantitative tools to evaluate the environmental performance of chemical processes across their lifecycle. Life cycle assessment (LCA), standardized by ISO 14040:2006, systematically analyzes impacts from raw material extraction to end-of-life disposal, encompassing categories like resource depletion, emissions, and toxicity to inform process improvements.^[96] Carbon footprint calculations, often aligned with GHG Protocol methodologies, quantify total GHG emissions associated with a chemical product or process in CO2-equivalent units, incorporating Scope 1 (direct), Scope 2 (energy-related), and Scope 3 (supply chain) emissions; for instance, the chemical industry guideline recommends using allocation methods for multi-product facilities to attribute emissions accurately. Green chemistry principles integrate environmental considerations into process design to reduce inherent hazards. The 12 principles, outlined by Paul Anastas and John Warner in 1998, emphasize prevention of waste, atom economy to maximize incorporation of reactants, use of less hazardous syntheses and materials, and design for energy efficiency and safer degradation.^[97] Applied to chemical processes, these principles guide innovations such as solvent-free reactions and catalytic systems, which have lowered waste generation in pharmaceutical manufacturing in adopting firms. The principles also promote renewable feedstocks and real-time pollution prevention, fostering inherently safer and more sustainable industrial practices.^[97]

Applications and Research

Industrial Implementations

In the petrochemical industry, chemical processes such as cracking and reforming are essential for converting crude oil fractions into valuable fuels and feedstocks. Fluid catalytic cracking (FCC) is a key process that breaks down heavy gas oils into lighter hydrocarbons, primarily gasoline, using a fluidized bed of zeolite catalysts at temperatures around 500–550°C and pressures near atmospheric. This carbon-rejection method produces approximately 30–50% gasoline yield from the feed, along with olefins and cycle oils, and accounts for a significant portion of global gasoline production in refineries.^[98]^[99] Catalytic reforming complements cracking by upgrading low-octane naphtha into high-octane reformate through dehydrogenation, isomerization, and cyclization reactions over platinum-based catalysts at 450–520°C and 10–35 bar, yielding hydrogen as a byproduct for further refinery use. These processes often operate continuously to maximize efficiency and throughput in large-scale plants.^[100]^[101] In the pharmaceutical sector, multi-step synthesis routes enable the production of active ingredients like aspirin (acetylsalicylic acid) through acetylation of salicylic acid. Industrially, this involves reacting salicylic acid with acetic anhydride in the presence of a catalyst such as sulfuric acid, typically in a solvent like toluene, at controlled temperatures to form the ester while minimizing side reactions; the mixture is then quenched with water to precipitate the product, followed by filtration, washing, and drying.^[102]^[103] This batch or semi-continuous process yields high-purity aspirin at scales of thousands of kilograms per run, with global production of approximately 60,000 metric tons annually (as of 2024) to meet demand for analgesics and anti-inflammatory drugs.^[104] The food and beverage industry relies on fermentation and enzymatic processes to transform raw materials into consumable products. Fermentation for ethanol production involves yeast-mediated conversion of sugars from biomass like corn or sugarcane into ethanol and carbon dioxide under anaerobic conditions at 30–35°C, typically in large fermenters holding up to 500,000 liters, achieving titers of 10–15% ethanol before distillation. This process, central to biofuel and beverage manufacturing, utilizes strains of Saccharomyces cerevisiae and produces over 100 billion liters of ethanol yearly worldwide.^[105]^[106] Enzymatic processing enhances efficiency in applications such as starch hydrolysis using amylases to produce glucose syrups or lactose breakdown with β-galactosidases in dairy for low-lactose milk, operating at mild conditions (40–60°C, pH 4–7) to improve texture, flavor, and shelf life without harsh chemicals.^[107]^[108] Polymer production exemplifies addition polymerization, particularly for polyethylene via Ziegler-Natta catalysis. This process polymerizes ethylene monomer using titanium-based catalysts supported on magnesium chloride, activated by triethylaluminum, at 80–150°C and 10–50 bar in slurry or gas-phase reactors, forming linear high-density polyethylene (HDPE) chains with molecular weights exceeding 100,000 g/mol and minimal branching for applications in packaging and pipes. Discovered in the 1950s, Ziegler-Natta systems enable stereoregular polymerization, producing over 80 million tons of polyethylene annually with high catalyst efficiency (up to 10,000 kg polymer per gram catalyst).^[109]^[110]^[111] In the semiconductor industry, chemical processes are essential for fabricating electronic devices and integrated circuits. Chemical vapor deposition (CVD) deposits thin films of materials such as silicon dioxide or metals onto wafers using gaseous precursors like silane or tetraethyl orthosilicate at temperatures of 300–800°C under low-pressure or vacuum conditions. Wet etching uses chemical solutions, including hydrofluoric acid or buffered oxide etchants, to selectively remove layers and define circuit patterns with nanoscale precision. These unit operations, often integrated in cleanroom environments, enable the production of advanced microchips critical for computing and consumer electronics.^[112]^[113]

Current Research Directions

Current research in chemical processes emphasizes process intensification techniques to enhance efficiency, reduce energy consumption, and minimize waste. Microreactors, which operate at small scales with high surface-to-volume ratios, enable precise control over reaction conditions, leading to improved selectivity and safety in exothermic reactions such as hydrogenation and polymerization.^[114] Reactive distillation integrates reaction and separation in a single unit, achieving up to 30% energy savings compared to traditional sequential processes for esterification and etherification, while reducing capital costs through equipment consolidation.^[115] Advancements in bioprocesses are driven by biotechnology integration, particularly through CRISPR-Cas9 gene editing to engineer microbes for sustainable fuel production. CRISPR-edited microorganisms, such as Escherichia coli and Saccharomyces cerevisiae, have been optimized to convert lignocellulosic biomass into biofuels like ethanol and butanol, with yields improved by 20-50% via targeted metabolic pathway enhancements.^[116] These engineered strains address limitations in substrate utilization and product tolerance, facilitating scalable bioconversion processes that align with renewable feedstocks.^[117] Digital twins and artificial intelligence (AI) are transforming chemical process optimization and predictive maintenance. Digital twins create virtual replicas of physical processes, enabling real-time simulation and scenario testing in the chemical industry, which has reduced downtime by up to 15% in polymerization plants through anomaly detection.^[118] Machine learning algorithms, integrated with these twins, predict equipment failures and optimize parameters like temperature and flow rates, achieving 10-25% improvements in energy efficiency for distillation and reactor operations.^[119] Key challenges in current research include the electrification of chemical processes and advancing circular economy approaches. Electrification via plasma catalysis offers a pathway to replace fossil fuel-based heating with renewable electricity, enabling direct synthesis of ammonia and methanol at lower temperatures, though scalability and catalyst stability remain barriers due to plasma-induced degradation.^[120] Post-2020 initiatives, such as the European Green Deal, promote circularity in the chemical sector by emphasizing waste valorization and recycling, with technologies like advanced catalysis recovering 70-90% of plastic monomers, yet requiring policy incentives to overcome economic hurdles.^[121]

References

[1]
Process Fundamentals — Introduction to Chemical and Biological ...
A chemical process is a combination of steps in which starting materials are converted into desired products using systems, equipment, and conditions that ...
[2]
What is a Chemical ? | Nuclear Regulatory Commission
More generally, a chemical reaction can be understood as the process by which one or more substances change to produce one or more different substances.
[3]
What is the difference between a chemical process and a physical ...
Sep 24, 2013 · Some chemistry teachers like to define a chemical process as any process that involves a chemical reaction and all other processes as physical ...
[4]
Chemical Process Development in the Pharmaceutical Industry in ...
Mar 27, 2025 · Chemical process development is a critical component in the development process for active pharmaceutical ingredients (APIs).
[5]
Chemical process more efficiently converts carbon dioxide to ... - NSF
Jun 25, 2025 · Chemical process more efficiently converts carbon dioxide to methanol, a chemical used in manufacturing and a potential fuel. A new catalytic ...
[6]
Chemical processing - LNF Wiki
Chemical processing is widely used in device fabrication, for cleaning, etching, electroplating, patterning or other types of processing.
[7]
Everyday Things Made Possible Through Chemistry | New Jersey ...
Mar 5, 2024 · Chemistry plays a vital role in extending the shelf life of our food, enhancing food safety, and reducing waste. The canned soup in your cabinet ...
[8]
To decarbonize the chemical industry, electrify it | MIT News
Jan 31, 2023 · The chemical industry is the world's largest industrial energy consumer and the third-largest source of industrial emissions, according to ...
[9]
1 Introduction | The Importance of Chemical Research to the U.S. ...
In short, chemistry has contributed significantly to everyday lives of people everywhere and is critical to the nation's economic prosperity, human health, food ...
[10]
What is chemical engineering? - University of Toledo
Chemical engineers invent, develop, design, operate, and manage processes. We make products that meet society's needs.
[11]
Department of Chemical Engineering | MIT Course Catalog
Chemical engineering encompasses the translation of molecular information into discovery of new products and processes. It involves molecular transformations— ...Missing: definition | Show results with:definition
[12]
Fermentation: Humanity's Oldest Biotechnological Tool
Oct 18, 2021 · The history of fermentation starts as far back as 10,000 B.C.E., when the first human civilization emerged in a region called the fertile ...
[13]
(PDF) Distillation – from Bronze Age till today - ResearchGate
The first distillation apparatus found in Mesopotamia (today´s Iraq) comes from the period 3500 BC. A part of distillation apparatus from Spišský Štvrtok ( ...<|separator|>
[14]
The Secrets of Alchemy | Science History Institute
Jan 30, 2013 · The book surveys the history of alchemy from its origins in late antiquity to the present day. It focuses on a few representative characters and ideas.
[15]
[PDF] OLEUM Section: Concentrated Sulfuric Acid
It was soon superseded by the lead chamber process, invented by John Roebuck in 1746 and since improved by many others. The contact process was originally.
[16]
A revolutionary casualty | Feature - Chemistry World
Oct 30, 2006 · In 1789 Nicolas Leblanc was lauded for developing an industrial process that turned salt into soda. Then the French revolution stripped him ...
[17]
Introduction to Ammonia Production - AIChE
The first commercial ammonia plant based on the Haber-Bosch process was built by BASF at Oppau, Germany. The plant went on-stream on Sept. 9, 1913, with a ...<|separator|>
[18]
A timeline of chemical manufacturing - ICIS
May 12, 2008 · 1920 Isopropyl alcohol produced at Standard Oil's Bayway, New Jersey, US, plant is the first commercial petrochemical. 1920s Cellulose acetate, ...
[19]
[PDF] The End of the Chemical Century? Organizational Capabilities and ...
The chemical industry's stability ended due to generic capabilities, technology changes, and a lack of dynamic strategy, leading to overcapacity and new ...Missing: continuous | Show results with:continuous
[20]
George E Davis – Meet the Daddy - Features - The Chemical Engineer
Mar 1, 2012 · Davis is the author of the seminal A Handbook of Chemical Engineering, published in 1901. In it, he defines the attributes and functions of the chemical ...Missing: textbook | Show results with:textbook
[21]
History of Chemical Engineering - ACS Publications
George E. Davis invented the essential unit operation concept and wrote the first textbook on chemical engineering in 1901. Norman Swindin was his only pupil ...
[22]
Energy, Enthalpy, and the First Law of Thermodynamics
First law: Energy is conserved; it can be neither created nor destroyed. Second law: In an isolated system, natural processes are spontaneous when they lead to ...
[23]
10.4 First law of thermodynamics – Chemistry Fundamentals
This is one version of the first law of thermodynamics, and it shows that the internal energy of a system changes through heat flow into or out of the system.
[24]
13.7: The Gibbs Free Energy - Chemistry LibreTexts
May 13, 2023 · Both ΔH and TΔS are temperature dependent, but the lines have opposite slopes and cross at 373.15 K at 1 atm, where ΔH = TΔS. Because ΔG = ΔH − ...
[25]
16.4 Free Energy - Chemistry 2e | OpenStax
Feb 14, 2019 · By the end of this section, you will be able to: Define Gibbs free energy, and describe its relation to spontaneity; Calculate free energy ...
[26]
Raoult's Law - Chemistry LibreTexts
Jan 29, 2023 · Ideal solutions satisfy Raoult's Law. · In an ideal solution, it takes exactly the same amount of energy for a solvent molecule to break away ...
[27]
Henry's Law - Chemistry LibreTexts
Jan 29, 2023 · Henry's law only works if the molecules are at equilibrium. · Henry's law does not work for gases at high pressures (e.g., N 2 ⁢ ( g ) at high ...Key differences between... · Example 1 · Solution · Example 2
[28]
4.6: Activation Energy and Rate - Chemistry LibreTexts
Jul 12, 2019 · At a given temperature, the higher the Ea, the slower the reaction. The fraction of orientations that result in a reaction is the steric factor.
[29]
6.2.3.1: Arrhenius Equation - Chemistry LibreTexts
Feb 13, 2024 · k : Chemical reaction rate constant. In unit of s-1(for 1st order ... Use the equation k = Ae-Ea/RT. 12 = 15e-Ea/(8.314)(22). Ea = 40.82J ...
[30]
Catalysis | PNNL
Lowering the activation energy allows the reaction to occur more often at a given temperature, increasing the rate of the reaction. Catalysis can be generally ...
[31]
Catalysis – Introductory Chemistry
Catalysts are chemical compounds that increase the rate of a reaction by lowering the activation energy required to reach the transition state.62 Catalysis · Types Of Catalysts · Enzyme Catalysis
[32]
Stoichiometry and Balancing Reactions - Chemistry LibreTexts
Jun 30, 2023 · Stoichiometry is a section of chemistry that involves using relationships between reactants and/or products in a chemical reaction to determine desired ...
[33]
[PDF] Chemical Process Calculations - BIET
Principle of Stoichiometry. Stoichiometry is the basic tools for chemical process calculation. In chemical reactions, the mass and volumetric relationships ...
[34]
Material Balances — Introduction to Chemical and Biological ...
Under these conditions, our material balance equation becomes. Rate that Rate that mass enters = mass leaves the system the system. Consider the following ...
[35]
[PDF] Chapter 4 MATERIAL BALANCES AND APPLICATIONS - KFUPM
Material balances apply the law of conservation of mass, where total input equals total output, and are used to calculate mass flow rates.
[36]
Conversion, Selectivity, Yield for a multiple reaction - ChemEnggCalc
Sep 30, 2024 · In chemical reaction engineering, conversion, selectivity, and yield are essential metrics that help evaluate the efficiency and effectiveness of chemical ...Selectivity – Meaning and... · Instantaneous Selectivity · Overall Selectivity
[37]
[PDF] Cleaning Up With Atom Economy - American Chemical Society
Atom economy is an important development beyond the traditionally taught concept of percent yield. Barry Trost, from Stanford University, published the concept.
[38]
The E Factor: fifteen years on - Green Chemistry (RSC Publishing)
The purpose of this perspective is to review the effect that the E Factor concept has had over the last fifteen years on developments in the (fine) chemical ...
[39]
recycle-mass-balances-example-problems - LearnChemE
Example Problem 1: In an evaporative crystallization process, 400 kg/h of a 15 wt% KCl/85 wt% H 2 O feed is mixed with recycle and fed to an evaporator.
[40]
Chemical Engineering > Material Balances > Recycle Processes
Recycle processes involve redirecting a portion of the output stream from a process unit back to its input. This technique is employed for several reasons.
[41]
Batch Process - an overview | ScienceDirect Topics
Some examples of batch processes are beverage processing, biotech products manufacturing, dairy processing, food processing, pharmaceutical formulations and ...
[42]
Batch - Visual Encyclopedia of Chemical Engineering Equipment
Apr 4, 2022 · Batch reactors are simple, closed systems where reactants are placed inside, allowed to react, and then products are removed. They operate ...Missing: definition | Show results with:definition
[43]
Reactors - processdesign
Feb 22, 2016 · Batch processes are suitable for small-scale production (less than 1,000,000 lb/yr) and for processes where several different products or grades ...Missing: definition characteristics
[44]
1 – Polymer Production
Apr 14, 2022 · Batch reactors are typically used for all other consumer orders, as they allow for special orders and polymer modification. Continuous Polymer ...
[45]
Control of Processes
Apr 15, 2022 · In a batch process, a fixed quantity of raw material is converted to a batch of the product, with definite beginning and endpoints. In a ...Missing: characteristics | Show results with:characteristics
[46]
1.6 – Types of Processes — project1 1.0 documentation
### Summary of Semi-Batch Processes
[47]
Fed-Batch Mode - an overview | ScienceDirect Topics
Fed-batch mode involves intermittently adding nutrients to a reaction vessel, supplying substrate in batches, and removing product after the reaction cycle.
[48]
[PDF] comparison of batch versus continuous process in the - OAKTrust
Aug 21, 2017 · Continuous process is widely applied in petro-chemical and bulk chemical industry for its high production rate, automated operation and ...<|separator|>
[49]
[PDF] Reactor Design | Rosen Review
May 11, 2014 · 1.3 Continuous-Flow Reactors. 1.3.1 Continuous-Stirred Tank Reactor (CSTR). • CSTRs are operated at steady state (accumulation = 0) and are ...
[50]
[PDF] Refining - The University of Texas at Dallas
Refining is the process of converting crude to usable products. Refining operations are continuous processes ... process 36% of the crude oil; top 10 process 77%.
[51]
Haber-Bosch Process - an overview | ScienceDirect Topics
The Haber–Bosch process is a well-developed ammonia synthesis technology with the first-generation heterogeneous catalytic system for the main industrial ...
[52]
The Reynolds Number: A Journey from Its Origin to Modern ... - MDPI
The Reynolds number (Re) is a dimensionless number relating inertial and viscous forces, used to characterize flow as laminar or turbulent.
[53]
Fourier's heat conduction equation: History, influence, and ...
Feb 1, 1999 · This equation was formulated at the beginning of the nineteenth century by one of the most gifted scholars of modern science, Joseph Fourier of ...
[54]
Newton's law of cooling: Contemporary Physics
The second part of the paper is an attempt to reconstruct Newton's transient cooling experiment using modern knowledge of heat transfer. ... Citation & references.
[55]
The origin and present status of Fick's diffusion law - ACS Publications
This article is cited by 81 publications. Nirman Chakraborty, Adi Harchol, Beatriz Costa Arnold, Kusha Sharma, Diksha Prabhu Gaonkar, Azhar Abu-Hariri, ...
[56]
Methodologies for Predicting the Mass Transfer Performance of ...
This review summarizes the various methods implemented with computational fluid dynamics (CFD) to predict mass transfer in structured packings.
[57]
[PDF] Phase Equilibria In Chemical Engineering Walas 1985
Distillation, the most widespread industrial separation technique, relies heavily on accurate vapor-liquid equilibrium data. Walas's detailed treatment of ...
[58]
Graphical Design of Fractionating Columns - ACS Publications
Article June 1, 1925. Graphical ... From graphical to model‐based distillation column design: A McCabe‐Thiele‐inspired mathematical programming approach.Missing: original | Show results with:original
[59]
Solvent Extraction - an overview | ScienceDirect Topics
These studies show that the distribution coefficient increases using mixed solvents with stronger solvation of the proton and more complete dissociation into ...
[60]
Solvent Screening for Separation Processes Using Machine ...
The optimal extractant solvent should exhibit a high distribution coefficient, low mutual solubility, low toxicity, high chemical stability, and low cost. (2) ...
[61]
Centrifugation - an overview | ScienceDirect Topics
Centrifugation is defined as a separation technique that utilizes centrifugal force to separate components of a mixture based on their size and density, ...Missing: authoritative | Show results with:authoritative
[62]
THE ADSORPTION OF GASES ON PLANE SURFACES OF GLASS ...
Article September 1, 1918. THE ADSORPTION OF GASES ON PLANE SURFACES OF GLASS, MICA AND PLATINUM. Click to copy article linkArticle link copied! Irving Langmuir.
[63]
Adsorption Chromatography - an overview | ScienceDirect Topics
Adsorption chromatography (AC) is chromatographic separation due to energetic interactions between the solute and the surface of the porous packings.
[64]
Block Flow Diagram - processdesign
Mar 1, 2015 · A block flow diagram (BFD) is a drawing of a chemical processes used to simplify and understand the basic structure of a system.Overview · Uses · Models
[65]
Diagrams for Understanding Chemical Processes - InformIT
Jul 3, 2012 · A Block Flow Diagram (BFD) uses blocks representing equipment or unit operations connected by input/output streams, showing process functions, ...
[66]
Process flow diagram - processdesign
Mar 2, 2015 · For process equipment, there are a few standard symbols that should be recognized by chemical engineers. Typically, these symbols correlate ...Overview · Process Topology · Stream Information · Equipment Information
[67]
181 Process Flow Diagram (PFD) Symbols for Engineers
Flow chart symbols use different shapes to represent different components, such as equipment, valves, instruments, and piping flow.Process Flow Diagram... · Miscellaneous PFD Symbols · General PFD Symbols
[68]
Aspen Plus | Leading Process Simulation Software - AspenTech
Aspen Plus advances the performance of chemical processes using the best-in-class simulation software for bulk chemicals, specialty chemicals and pharmaceutical ...Missing: state | Show results with:state
[69]
Aspen HYSYS | Leading Process Simulation Software for Oil & Gas | AspenTech
### Overview of Aspen HYSYS for Process Simulation
[70]
[PDF] Process Simulators
Select the convergence method and run simulation. In general 3, 5, and 7 cause the most problems. Process Simulators – p.6/10. Page 23. Selecting Thermodynamic ...
[71]
Heat exchanger - processdesign
Feb 19, 2016 · Heat exchangers are necessary process units that are part of any detailed process flow diagram. Process streams commonly interact through heat exchangers.
[72]
Dimensional Analysis and Scale-up in Chemical Engineering
On the one hand, treatises on dimensional analysis, the theory of similarity and scale-up methods included in common, run-of-the-mill textbooks on chemical ...
[73]
Power Number - an overview | ScienceDirect Topics
The power number is defined as a dimensionless number used to scale up agitation tanks, calculated using the formula $ N_p = \frac{P}{\rho N^3 D^5} $, where ...
[74]
None
Below is a merged summary of the optimization techniques in chemical processes, consolidating all information from the provided segments into a comprehensive response. To retain maximum detail and ensure clarity, I will use a structured format with tables where appropriate, followed by a narrative summary. The response avoids redundancy while preserving all key points, examples, and URLs.
[75]
8 Key Challenges To Pilot Plant Scale-Up - EPIC Systems Group
A thorough thermodynamic analysis is necessary for successful pilot plant scale-up due to the sensitivity of chemical reactions to heat gain and heat loss.
[76]
Guide of Pilot Plant Scale-Up Techniques - Adesis
May 28, 2024 · Learn more about the fundamental aspects of pilot scale-up, key considerations in process optimization, and common challenges.
[77]
Rules of Thumb: Scale-up - Features - The Chemical Engineer
Oct 26, 2023 · Mixing under laminar conditions yields dimensionless mixing times in the order of 100–1,000. ... For turbulent mixing we know that the power ...
[78]
[PDF] A Practical Guide to Chemical Process Optimization - eGrove
These variables can be continuous or discrete, the former meaning any value over a continuous range while the latter meaning specific values. Page 11. 7.
[79]
Hazard and Operability Study (HAZOP) - SAFEChE: Process Safety
A HAZOP study is a structured analysis in process design to identify potential process safety incidents that a facility is vulnerable to.
[80]
[PDF] Risk Assessment 9. HAZOP - NTNU
A Hazard and Operability (HAZOP) study is a structured and systematic examination of a planned or existing process or operation in order to identify.
[81]
[PDF] NUREG-0492, "Fault Tree Handbook".
*For an actual example of a fault tree analysis applied to a major nuclear safety system see. U.S. Nuclear Regulatory Commission, "Reactor Safety Study-An ...
[82]
Fault Tree Analysis (FTA) - Gexcon Consulting
Fault Tree Analysis (FTA) is a method used in high-hazard industries to identify root causes of system failures using a visual diagram-based framework.
[83]
[PDF] Inherently Safer Design: The Fundamentals - AIChE
Build safety into your process by substituting less-hazardous materials and chemistry, minimizing inventories and equipment sizes, moderating operating ...
[84]
Inherent Safety (Process Safety) - an overview | ScienceDirect Topics
Further, Professor Kletz proposed four key inherent safety principles: minimization, substitution, moderation, and simplification (Kletz, 1985). The application ...
[85]
Safety Instrumentation Systems - AIChE
A safety instrumented system (SIS) takes automated action to keep a plant in a safe state, or to put it into a safe state, when abnormal conditions are present.
[86]
Pressure Control & Relief
Apr 15, 2022 · They enhance process safety by relieving fluids, thus lowering operating pressure, and protecting other equipment from corrosive and toxic ...
[87]
Emergency Shutdown (ESD) | ITI Group
Our emergency shutdown systems are designed to minimise the consequences of emergency situations in hazardous environments such as a chemical release, fire, or ...
[88]
2 Bhopal and Chemical Process Safety | The Use and Storage of ...
Autopsies performed on 300 victims of the disaster showed lesions that were severely necrotized on the upper respiratory tract lining, the lung capillaries, ...
[89]
[PDF] Safety under scrutiny — Flixborough 1974 - IChemE
A significant underlying cause was the poor culture surrounding process safety at Flixborough which was systemic throughout the chemicals industry. Safety ...
[90]
Energy & Greenhouse Gas Emissions - American Chemistry Council
Oct 30, 2024 · Natural gas is the largest source of fuel and power for the chemical industry. The chemical industry purchases electricity and some steam ...<|separator|>
[91]
REACH Regulation - Environment - European Commission
REACH is the main EU law to protect human health and the environment from the risks that can be posed by chemicals.Access to European Union law · 1907/2006 - EN · Chemicals
[92]
1990 Clean Air Act Amendment Summary | US EPA
In 1989, President George W. Bush proposed revisions to the Clean Air Act designed to curb acid rain, urban air pollution, and toxic air emissions.
[93]
ISO 14040:2006 - Life cycle assessment
ISO 14040:2006 describes the principles and framework for life cycle assessment (LCA) including: definition of the goal and scope of the LCA.
[94]
12 Principles of Green Chemistry - American Chemical Society
Developed by Paul Anastas and John Warner in Green Chemistry: Theory and Practice (1998), the following list outlines a framework for making a greener chemical ...
[95]
Fluid catalytic cracking is an important step in producing gasoline - EIA
Dec 11, 2012 · Fluid catalytic cracking (FCC) is a chemical process using a catalyst to break down gas oil into smaller molecules, including gasoline, using ...
[96]
Fluid Catalytic Cracking (FCC) Process Modeling, Simulation, and ...
This paper focuses on the fluid catalytic cracking (FCC) process and reviews recent developments in its modeling, monitoring, control, and optimization.
[97]
Catalytic reforming boosts octane for gasoline blending - EIA
Apr 9, 2013 · The process turns straight-chain hydrocarbons into cyclic compounds while removing hydrogen. The cyclic compounds have a much higher octane ...
[98]
Chemistry of Catalytic Reforming | FSC 432: Petroleum Refining
The reforming reactions produce large quantities of hydrogen, and one should remember that the dehydrogenation catalysts used in reforming can also catalyze ...
[99]
The Manufacture of Aspirin - NJIT
As you read through this page, you will be asked to make a choice between the two methods of aspirin production which were presented earlier.
[100]
Salicylic Acid (Aspirin) - StatPearls - NCBI Bookshelf
In the 1800s, the Heyden Chemical Company was the first to mass-produce salicylic acid commercially. It was not until 1899 when a modified version named ...Salicylic Acid (aspirin) · Administration · Toxicity
[101]
6.3b How Corn is Processed to Make Ethanol | EGEE 439
Fermentation: The sugars are fermented by yeast, producing ethanol and CO₂ as byproducts. · Centrifugation: The remaining solids are separated to yield ...
[102]
[PDF] Xylose Fermentation to Ethanol: A Review - NREL
The composition of the nitrogen source affects the rate of ethanol production and the ethanol selectivity during anaerobic fermentation of xylose by Pa.
[103]
Enzymes in Food Processing: A Condensed Overview on Strategies ...
This paper aims to provide an updated and succinct overview on the applications of enzymes in the food sector, and of progresses made
[104]
Enzyme Immobilization on Nanomaterials for Food Processing ...
Aug 13, 2025 · Enzymes such as lactase, amylase, xylanase, glucose oxidase, lipase, β-galactosidase, and many more are commonly used in the food industry (14).
[105]
Insight into the Synthesis Process of an Industrial Ziegler–Natta ...
Dec 21, 2018 · We fully characterize a single-step catalyst preparation process, which comprises a reactive precipitation of a MgCl 2 -supported Ziegler–Natta catalyst.Introduction · Materials and Methods · Results and Discussion · Author Information
[106]
Electrophilic Addition to Alkenes EA13. Ziegler-Natta Polymerization
In Ziegler-Natta polymerization, monomers are treated with a catalyst, such as a mixture of titanium chloride (or related compounds, like oxovanadium chloride) ...
[107]
The Influence of Ziegler-Natta and Metallocene Catalysts on ...
The discovery of Ziegler-Natta catalysts gave a new dimension to the world of polymers. For more than five decades remarkable progress in catalytic olefin ...
[108]
(PDF) Recent Advances in Microreactors, Membrane Reactors, and ...
Mar 9, 2025 · ArticlePDF Available. Recent Advances in Microreactors, Membrane Reactors, and Oscillatory Flow Reactors for Process Intensification: Review.
[109]
Recent Advances in Reactive Distillation - MDPI
Oct 26, 2023 · Reactive distillation (RD) is a process intensification technology that has successfully enhanced chemical manufacturing [5]. The most recent ...
[110]
Advances in engineered microbes for sustainable biofuel production
Dec 15, 2024 · The recent advances in engineered microbes focus on the optimization of metabolic pathways, CRISPR/Cas9, Gene Editing and modular engineering.
[111]
CRISPR edited microbes and their industrial potential review
Mar 10, 2021 · The organisms modified by this CRISPR/Cas9 involved a huge diversity of targeting vectors including bacteria, yeast, fungi, algae (cyanobacteria ...
[112]
Digital twin in the chemical industry: A review - IET Journals - Wiley
Dec 11, 2024 · Adopting digital twin technology in the chemical industry is reshaping process optimisation, operational efficiency, and safety management.
[113]
Advancing chemical engineering technology with artificial intelligence
Sep 24, 2025 · This review provides a unique perspective on artificial intelligence's role as a catalyst for chemical engineering's evolution.2. Chemical Process Control · 2.2 Digital Twin · 3. Ai-Driven Industrial...
[114]
Perspectives and Emerging Trends in Plasma Catalysis
Electrification of chemical production requires the development of innovative solutions, with plasma catalysis being among them. This perspective summarizes ...
[115]
The Chemical sector in transition: Technological developments and ...
This paper explores the transition from linear production methods to a Circular Economy in the chemical industry through a literature review of recent ...