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Raffinate

Raffinate is the stream that remains after the selective removal of one or more components from an original mixture through a separation process such as solvent extraction or adsorption.^[1] In liquid-liquid extraction, it is the liquid phase depleted of target solutes after contact with an immiscible solvent. This term, derived from the French word raffiner meaning "to refine," describes the residual phase, in contrast to the extract, which is the solvent phase enriched with the target components.^[2] In chemical engineering, raffinate plays a critical role in separation technologies, where it often represents the purified or waste stream depending on the process goals. It is commonly produced in multi-stage extraction operations to maximize component recovery. Key industrial applications include petroleum refining, where raffinates are generated during the separation of aromatic hydrocarbons like toluene from hydrocarbon mixtures; hydrometallurgy, such as in copper and uranium processing to isolate metals from leach solutions; and pharmaceutical production for isolating active compounds from natural extracts.^[3]^[4] In petrochemicals, raffinates such as C4 streams are important byproducts used in further processing. Additional uses span wastewater treatment to remove contaminants, food processing for refining vegetable oils, and nuclear fuel reprocessing to handle radioactive streams.^[3] The composition and handling of raffinate are influenced by factors like solvent selection, phase ratios, and equilibrium conditions, which determine extraction efficiency and potential downstream processing needs, such as demulsification or further purification.^[5] In sustainable practices, raffinates are increasingly valorized— for instance, recovering residual metals from mining raffinates or repurposing petrochemical raffinates as feedstocks—to minimize waste and environmental impact.^[6]

Overview

Definition

In chemical engineering, raffinate refers to the liquid or gas stream that remains after the selective removal of target solutes from an original mixture through a separation process, such as solvent extraction, where it constitutes the phase depleted of the extracted components.^[1] This stream typically retains the majority of the carrier fluid or solvent from the feed, now with a significantly reduced concentration of the targeted solutes, while the extracted solutes are concentrated in a separate phase known as the extract.^[7] The composition of the raffinate is highly dependent on the initial feed mixture and the selectivity of the separation method employed, often resulting in a purified or refined output suitable for further processing or as a byproduct.^[8] The term "raffinate" originates from the French verb "raffiner," meaning "to refine," and entered English usage in the early 20th century within the context of oil refining operations, where it described the residual liquid after solvent-based purification of petroleum fractions.^[9] This etymology reflects the process's goal of refinement through impurity removal, distinguishing raffinate from the enriched extract phase.^[10] A basic representation of raffinate formation in a separation process, such as solvent extraction, involves a feed stream entering an extractor unit, where it contacts a solvent; the output consists of the raffinate (depleted feed phase) and the extract (solvent enriched with solutes).^[7] Solvent extraction serves as one of the primary methods for generating raffinate, enabling efficient separation in industries like petrochemicals and hydrometallurgy.^[11]

Historical Development

The concept of raffinate originated in the early 20th century within solvent extraction processes in petroleum refining, where it denoted the refined liquid phase remaining after selective removal of impurities or components using a solvent. Derived from the French term "raffiner" meaning "to refine," the term emphasized the purification aspect of the process. In the 1920s, raffinate production gained prominence through the development of solvent dewaxing and deoiling methods for lubricating oils, which involved chilling feedstock mixed with solvents like benzene or naphtha to crystallize and separate wax, yielding a dewaxed oil raffinate suitable for low-temperature applications. A notable milestone occurred in 1929 when the Indian Refining Company, under the leadership of Dr. Francis X. Govers, perfected an innovative solvent-dewaxing process that enhanced efficiency in producing high-quality raffinates from petroleum stocks.^[12] The 1930s marked a significant expansion of raffinate applications in petrochemical separations, particularly for butadiene extraction to support synthetic rubber production amid rising global demand. As preparations for World War II accelerated, extractive processes were refined to isolate 1,3-butadiene from C4 hydrocarbon streams derived from petroleum cracking, leaving behind raffinate as the non-extracted residue. Research initiated in the early 1930s by chemists at Standard Oil (Jersey Standard) focused on petroleum-based butadiene routes, enabling large-scale adoption of these methods during wartime efforts to replace natural rubber supplies. Concurrently, German conglomerate I.G. Farbenindustrie played a pivotal role in advancing extractive distillation techniques for separating close-boiling hydrocarbons, which generated raffinate streams as byproducts in processes for fuels, lubricants, and synthetic materials; their innovations were critical for industrial-scale refining.^[13] By the 1950s, the petrochemical industry's growth, driven by post-war expansion of steam cracking for ethylene, led to broader utilization of raffinate from C4 streams in dedicated plants. This period saw increased standardization of raffinate outputs as feedstocks for further processing. The transition from batch to continuous operations in the 1960s further revolutionized production, allowing uninterrupted solvent extraction and distillation flows that improved yield consistency and enabled the classification of distinct raffinate types, such as those from C4 fractions.^[14]

Production Processes

Solvent Extraction

Solvent extraction is a separation technique that involves contacting a feed solution containing the target solute with an immiscible solvent, allowing the solute to partition preferentially into the solvent phase to form the extract, while the depleted feed solution becomes the raffinate.^[15] This process is widely applied in chemical engineering for purification and concentration, leveraging differences in solubility between the two liquid phases.^[16] The process typically occurs in stages: mixing, where the feed and solvent are intimately contacted to maximize interfacial area and promote mass transfer; settling, where the phases disengage under gravity or mechanical means; and separation, where the extract and raffinate streams are collected.^[15] For enhanced efficiency, countercurrent multistage operations are employed, with the feed entering at one end and the solvent at the other, allowing progressive enrichment of the extract and depletion of the raffinate across multiple equilibrium stages.^[16] An example flow diagram illustrates this as a series of mixer-settler units in a cascade, with the raffinate exiting depleted and the extract proceeding to stripping.^[15] Key parameters governing the process include the distribution coefficient K, defined as K = \frac{[\text{solute}]_{\text{extract}}}{[\text{solute}]_{\text{raffinate}}}, which quantifies the solute's partitioning between phases at equilibrium.^[16] Selectivity \alpha, given by \alpha = \frac{K_A}{K_B} for two solutes A and B, measures the solvent's ability to preferentially extract one over the other, with higher values indicating better separation.^[15] Common equipment includes mixers-settlers for batch or continuous operation with good phase disengagement; pulsed columns, which use oscillatory flow to improve contact without mechanical agitation; and centrifugal extractors, which achieve rapid separation through high g-forces, suitable for shear-sensitive systems.^[16] Factors affecting raffinate yield and overall process efficiency encompass solvent choice, such as furfural or N-methyl-2-pyrrolidone (NMP), which must exhibit high selectivity and low miscibility with the feed; temperature, which influences solubility and viscosity to optimize mass transfer rates; and pH, particularly in aqueous feeds, where adjustments can enhance solute ionization and partitioning.^[15] Optimal conditions typically balance these to achieve extraction efficiencies exceeding 90% in multistage setups.^[16]

Adsorption-Based Methods

Adsorption-based methods represent an important class of separation techniques for producing raffinate streams, particularly in gas-phase processes where impurities are selectively removed by solid adsorbents, leaving a depleted non-adsorbed fraction as the raffinate.^[17] These methods contrast with liquid-liquid extraction by relying on physical adsorption rather than chemical solubility differences, making them suitable for purifying gaseous feeds without introducing liquid phases.^[18] Pressure swing adsorption (PSA) is a prominent cyclic process in this category, where a gas mixture is fed at elevated pressure into an adsorbent bed, allowing impurities to adsorb while the less-adsorbed target gas passes through as the raffinate stream.^[19] The mechanism involves alternating high-pressure adsorption (typically 5-40 bar) to capture impurities and low-pressure (or vacuum) desorption to regenerate the adsorbent, enabling continuous operation through multiple beds in parallel or series configurations.^[20] Common regenerable adsorbents include zeolites for their high selectivity toward polar molecules like CO2 and H2O, and activated carbon for non-polar impurities such as hydrocarbons.^[21] In PSA applications for raffinate production, the process is widely used in gas purification, such as recovering high-purity hydrogen raffinate from syngas mixtures produced via steam methane reforming, achieving purities exceeding 99.9% in the non-adsorbed stream.^[22] The adsorption behavior in these systems is often modeled using the Langmuir isotherm, which describes the equilibrium fractional surface coverage \theta of the adsorbent as:

\theta = \frac{K p}{1 + K p}

where K is the adsorption equilibrium constant and p is the partial pressure of the adsorbate; this model assumes monolayer adsorption on homogeneous sites and is fundamental for predicting breakthrough curves and cycle efficiency in PSA design.^[18] Other adsorption-based variants include temperature swing adsorption (TSA), which operates at near-constant pressure but uses temperature cycles—cooling for adsorption and heating (typically 100-200°C) for desorption—to produce raffinate-like depleted streams, often applied in natural gas dehydration or VOC removal from biogas.^[23] Membrane separation complements these by providing a continuous process where a gas feed permeates selectively through a polymer or ceramic membrane, yielding a retentate stream depleted in the permeated component, analogous to a raffinate in applications like CO2 removal from natural gas.^[24] Compared to solvent extraction, adsorption-based methods like PSA and TSA offer advantages such as the absence of liquid waste streams, reduced corrosion risks, and better suitability for large-scale gas handling, with lower energy demands for regeneration in many industrial setups.^[25]

Petrochemical Types

Raffinate-1 (C4R1)

Raffinate-1, also known as C4R1, is the primary raffinate stream obtained during the extractive distillation of crude C4 fractions from steam cracking processes, where 1,3-butadiene is selectively removed using polar solvents such as dimethylformamide (DMF) or acetonitrile.^[26]^[27] This process involves feeding the mixed C4 hydrocarbons into a distillation column where the solvent enhances the relative volatility of butadiene, allowing its extraction into the bottoms while non-polar components like butenes and butanes remain in the overhead as Raffinate-1.^[28] The resulting stream serves as a key intermediate in petrochemical refining, rich in valuable olefins for further separation.^[29] The typical composition of Raffinate-1 consists of 40-50 wt% isobutylene, 30-35 wt% 2-butene (including cis- and trans-isomers), 10-15 wt% butanes (n-butane and isobutane), and 10-40 wt% 1-butene, with residual 1,3-butadiene minimized to prevent unwanted reactions.^[30]^[31] These proportions can vary slightly depending on the feedstock origin, such as naphtha or gas oil cracking, but the high isobutylene content distinguishes it as a preferred source for downstream olefin production.^[32] The low levels of saturated butanes reflect the partial hydrogenation or inert components carried over from the crude C4 feed.^[26] Physically, Raffinate-1 is a colorless liquid under pressurized conditions, exhibiting a boiling range of approximately 0-5°C and a density of about 0.62 g/cm³ at its boiling point, consistent with its mixture of low-molecular-weight hydrocarbons.^[31] These properties facilitate its handling as a liquefied gas in industrial settings, with a characteristic mild hydrocarbon odor.^[30] Purity specifications for Raffinate-1 emphasize a residual 1,3-butadiene content below 500 ppm to mitigate polymerization risks during storage and processing, ensuring stability and safety in petrochemical applications.^[33] This low butadiene threshold is achieved through efficient solvent selectivity in the extraction column, often supplemented by downstream polishing steps if needed.^[34]

Raffinate-2 (C4R2)

Raffinate-2, also known as C4R2, is generated by further processing Raffinate-1 to remove isobutylene, typically through its conversion to methyl tert-butyl ether (MTBE) via reaction with methanol or to tert-butyl alcohol (TBA) via direct hydration.^[26] This step follows the initial extraction of 1,3-butadiene from crude C4 streams in petrochemical processes.^[35] The typical composition of Raffinate-2 consists of 50-60 wt% 2-butene (a mixture of cis- and trans-isomers), 10-15 wt% 1-butene, approximately 20 wt% n-butane, and less than 5 wt% isobutylene.^[36] This results in a stream enriched in linear butenes compared to Raffinate-1, with significantly reduced branched olefin content.^[35] Raffinate-2 exhibits a narrow boiling range of -5 to 5°C, reflecting the similar volatilities of its primary C4 hydrocarbon components, and it functions as a key C4 olefin stream in downstream petrochemical operations. Depending on the production method, it may contain impurities such as residual alcohols (e.g., methanol from MTBE synthesis or TBA from hydration) or water, typically at levels below 5 wt%.^[37] These impurities can act as poisons, inhibiting active sites on catalysts used in subsequent reactions like isomerization or metathesis.^[38]

Raffinate-3 (C4R3)

Raffinate-3, denoted as C4R3, is the residual C4 hydrocarbon stream produced following the extraction of 1-butene from Raffinate-2 in petrochemical refining processes. This stream arises in the downstream processing of mixed C4 fractions from steam cracking or fluid catalytic cracking units, where sequential separations remove butadiene, isobutene, and then 1-butene to yield increasingly refined butene products. The 1-butene is removed to enrich the stream in 2-butene, making it a key intermediate in the production of higher-value olefins.^[39] The production of Raffinate-3 is achieved through superfractionation or extractive distillation of Raffinate-2. Superfractionation employs multi-stage distillation columns with high reflux ratios to separate 1-butene based on subtle boiling point differences, achieving polymer-grade purity for the extracted 1-butene while leaving Raffinate-3 as the bottoms product. Extractive distillation, alternatively, uses a polar solvent like N-methylpyrrolidone to alter relative volatilities, facilitating the selective removal of 1-butene in a more energy-efficient manner for certain feed compositions. These methods are widely adopted in industrial settings to maximize butene recovery from C4 streams.^[40]^[41] The composition of Raffinate-3 is dominated by 2-butene, typically comprising 80-90% of the stream as a mixture of cis- and trans-isomers, with n-butane accounting for 10-15% and trace levels of 1-butene (<1%). This composition reflects the depletion of linear alpha-olefins, resulting in a butene-rich raffinate suitable for further processing. Variations in percentages can occur based on the quality of the upstream Raffinate-2 and the efficiency of the separation technology employed.^[42]^[43] Key properties of Raffinate-3 include a high trans/cis-2-butene ratio, often exceeding 2:1 due to the thermodynamic stability of the trans isomer during processing, which enhances its reactivity in catalytic reactions. This makes the stream particularly suitable as a feed for polymerization processes, such as the production of polybutene-1 or other olefin polymers used in packaging and automotive applications. The low 1-butene content minimizes side reactions in downstream polymerization, improving product yield and quality.^[42]^[44] Economically, Raffinate-3 holds value as an intermediate for the high-purity butene market, where it can be further fractionated to isolate polymer-grade 2-butene or directed to alkylation units for gasoline blending. Its role in the C4 value chain supports the overall profitability of butadiene extraction plants by converting what would be a low-value residue into a feedstock for specialty chemicals, with market dynamics influenced by global demand for linear low-density polyethylene and synthetic lubricants.^[39]^[45]

Raffinate-4 (C4R4)

Raffinate-4, denoted as C4R4, represents the terminal residue in the sequential processing of C4 hydrocarbon streams derived from naphtha cracking in petrochemical facilities. This stream emerges after the exhaustive removal of unsaturated components, including 1,3-butadiene, isobutylene, 1-butene, and both cis- and trans-2-butene, leaving behind a predominantly saturated fraction.^[46] The production of Raffinate-4 occurs as a byproduct during the final stage of C4 refinement, where 2-butene is separated from Raffinate-3 (C4R3) via techniques such as fractional distillation or selective adsorption. These methods exploit differences in boiling points and adsorption affinities to isolate the remaining alkanes, yielding a stream that is largely free of olefins. In typical operations, distillation columns operate under controlled conditions to achieve high purity in the butane components, with adsorption processes using molecular sieves for enhanced selectivity when needed.^[47]^[48] Compositionally, Raffinate-4 is dominated by n-butane at 90-96%, accompanied by minor quantities of isobutane (typically 4-10%), and trace or negligible olefin content (<0.1%) resulting from the upstream extractions. This high alkane purity distinguishes it from earlier raffinates, positioning it as an olefin-depleted end product in the C4 separation cascade.^[49]^[46] As a saturated hydrocarbon mixture, Raffinate-4 exhibits properties akin to n-butane, including a boiling point of -0.5°C at standard pressure, low reactivity, and flammability suitable for fuel applications. Its density is approximately 0.578 g/cm³ at 20°C, and it remains gaseous at ambient conditions but can be liquefied under moderate pressure for storage and transport.^[50] In commercial applications, Raffinate-4 is frequently blended into liquefied petroleum gas (LPG) alongside propane and other C4 components to meet specifications for heating and automotive fuels. It also serves as a blending agent in gasoline production, where its addition helps regulate Reid vapor pressure (RVP) without significantly impacting octane ratings. Additionally, the stream acts as a feedstock for alkylation units in refineries, providing isobutane precursors (after potential isomerization) for reaction with olefins to produce high-octane alkylate.^[51]^[52]^[53]^[54]

Applications and Uses

In Petrochemicals

In petrochemical manufacturing, raffinates, particularly the C4 types derived from steam cracking processes, serve as valuable feedstocks for downstream hydrocarbon processing and chemical synthesis. These streams, obtained after selective extraction of butadiene and other olefins, enable the production of high-value intermediates and additives that enhance the overall economics of ethylene crackers.^[39] Raffinate-1 (C4R1), which consists mainly of isobutylene along with n-butenes and butanes, is commonly used as a feed for isobutylene recovery and subsequent conversion. Through catalytic dimerization, isobutylene in C4R1 is transformed into isooctene, a high-octane gasoline blending component that improves fuel performance without lead additives.^[55] Alternatively, hydration of isobutylene from C4R1 produces tert-butyl alcohol (TBA), which acts as an octane booster in gasoline or a precursor for other oxygenates. Raffinate-2 (C4R2), enriched in 1-butene and 2-butene after isobutylene removal, supports olefin production for polymer applications. 1-Butene is extracted from C4R2 and utilized as a comonomer in linear low-density polyethylene (LLDPE) manufacturing, enhancing polymer flexibility and strength in packaging and films.^[56] Additionally, 2-butene from C4R2 undergoes oxidative dehydrogenation to yield butadiene, providing an alternative route to this critical rubber precursor and closing the loop in C4 utilization.^[57] Raffinate-3 (C4R3), predominantly 2-butene and butanes following 1-butene separation, finds application in oxidation processes. It serves as a feedstock for the catalytic oxidation of butenes to maleic anhydride, a key intermediate in resins, coatings, and agricultural chemicals.^[58] Raffinate-4 (C4R4), the residual stream rich in butanes after extensive olefin removal, is employed as an alkylation feed to produce high-octane alkylate for gasoline blending or directly as fuel gas in refinery operations.^[33] Economically, C4 raffinates represent byproducts that add significant value to butadiene extraction plants by enabling diversified downstream processing, with C4 raffinate streams typically comprising over 50% of the crude C4 output from naphtha-based steam crackers. This utilization mitigates waste and supports the profitability of petrochemical complexes amid fluctuating olefin markets.^[39]

In Other Industries

In hydrometallurgy, raffinate streams arise during the solvent extraction phase of copper recovery from sulfuric acid leach solutions, where copper ions are selectively removed, leaving behind a metal-depleted acidic aqueous phase.^[59] This raffinate, often containing residual impurities like iron and sulfate, is frequently recycled to regenerate sulfuric acid for reuse in the leaching process, enhancing resource efficiency and reducing waste generation.^[60] For instance, sulfate recovery from such raffinates can achieve up to 85.9% conversion to sulfuric acid through precipitation and neutralization techniques.^[60] In the pharmaceutical industry, raffinate refers to the depleted aqueous fermentation broth remaining after organic solvent extraction of antibiotics, such as penicillin G, where the target compounds partition into the organic phase for further purification.^[61] This process, often employing countercurrent liquid-liquid extraction, effectively separates the antibiotic from impurities in the broth, with the raffinate serving as a waste stream or for additional downstream processing. Beyond these sectors, raffinate plays a role in vegetable oil refining through solvent extraction for deacidification, where the raffinate phase represents the purified, low-free-fatty-acid oil after free fatty acids are removed into the solvent extract.^[62] In nuclear fuel reprocessing, aqueous raffinate emerges as a high-level waste stream from processes like PUREX, containing fission products and minor actinides after uranium and plutonium extraction, which requires specialized treatment prior to immobilization.^[63] A notable case study involves uranium extraction from phosphoric acid or ore leachates using ion exchange resins, where the resin adsorbs uranyl ions, producing a metal-poor raffinate effluent that is typically neutralized and disposed of in engineered facilities to prevent environmental contamination.^[64] At sites like the Durita uranium mill in the United States, such raffinates from ion exchange operations have been managed through evaporation ponds and stabilization to mitigate long-term radiological risks.^[65]

Safety and Environmental Aspects

Handling and Hazards

Petrochemical C4 raffinates, such as Raffinate-1 to -4, are classified as extremely flammable gases or liquids with flash points typically below -30°C, rendering them highly susceptible to ignition and posing significant fire and explosion risks during handling and storage.^[66] Their high volatility contributes to the formation of explosive vapor clouds in air, with lower explosion limits around 1.5 vol% and upper limits up to 10 vol%, necessitating strict control of ignition sources such as sparks, open flames, and hot surfaces.^[66] According to NFPA standards, these materials receive a flammability rating of 4, indicating severe hazard, and are categorized as Class IA flammable liquids under NFPA 30 due to their low flash points and boiling ranges (typically -10°C to 5°C).^[67]^[68]^[69] Chemically, the olefin content in C4 raffinates, including residual butadiene, promotes hazardous polymerization reactions, which can be initiated or accelerated by heat, light, or contaminants like peroxides that form upon exposure to air and oxygen.^[70] This reactivity increases the risk of pressure buildup in containers, potentially leading to ruptures or explosions if not managed.^[71] Liquefied forms can also cause cryogenic burns or frostbite upon direct contact due to rapid evaporation.^[35] Safe handling requires trained personnel using closed systems and adequate ventilation to minimize vapor accumulation; all transfer operations must include electrical bonding and grounding of containers and equipment to prevent static electricity ignition.^[70] Storage should occur in cool, well-ventilated stainless steel tanks under an inert atmosphere, such as nitrogen blanketing, to inhibit oxidation and polymerization, with containers kept tightly closed and protected from sunlight and heat.^[71] Transportation follows UN 1965 classifications as liquefied hydrocarbon gas mixtures (Hazard Class 2.1), via pipelines, tank trucks, rail cars, or vessels, with measures to avoid ignition sources.^[66]^[70] Personal protective equipment includes safety glasses with side shields, chemically resistant gloves (e.g., nitrile rubber per EN ISO 374-1), flame-resistant clothing, and self-contained breathing apparatus in poorly ventilated areas or for high-exposure risks.^[66] OSHA guidelines establish exposure limits primarily for the butadiene component at 1 ppm (8-hour TWA) and 5 ppm (STEL), with an action level of 0.5 ppm, emphasizing monitoring and engineering controls to stay below these thresholds.^[70]^[35] In other contexts, such as hydrometallurgy, raffinates may be acidic solutions containing heavy metals (e.g., copper, uranium), requiring corrosion-resistant materials, pH neutralization, and precautions against toxic exposure. In nuclear reprocessing, raffinates can be radioactive, necessitating radiation shielding and specialized waste handling protocols. Pharmaceutical and food raffinates often involve residual solvents, demanding purity controls to avoid contamination.^[3]^[4]^[72]

Environmental Regulations

Petrochemical raffinates, as mixtures of C4 hydrocarbons produced in refining processes, are subject to stringent environmental regulations due to their high volatility, flammability, and potential to release volatile organic compounds (VOCs) that contribute to air pollution and photochemical smog formation. These regulations focus on emission controls, waste management, and prevention of environmental releases during production, storage, transport, and disposal. In the United States, raffinates fall under the Toxic Substances Control Act (TSCA), which requires reporting and inventory listing for petroleum-derived substances like raffinates (petroleum), sorption process (CAS 64741-85-1).^[73] Under the Resource Conservation and Recovery Act (RCRA), discarded raffinate is classified as a characteristic hazardous waste (D001) based on ignitability, given its low flash point and ability to sustain combustion. Facilities must manage raffinate waste in permitted units, with prohibitions on land disposal without prior treatment to meet toxicity and mobility standards. Additionally, VOC emissions from raffinate handling in petrochemical refineries are regulated under the Clean Air Act's New Source Performance Standards (NSPS) and National Emission Standards for Hazardous Air Pollutants (NESHAP), requiring vapor recovery systems, leak detection, and flaring controls to limit releases from storage tanks and process vents. In the European Union, raffinate substances are governed by the REACH Regulation (EC) No 1907/2006, mandating registration, evaluation, and authorization for high-volume imports or production. The Classification, Labelling and Packaging (CLP) Regulation harmonizes hazard classifications, designating certain raffinates as carcinogenic (Carc. 1B) due to trace butadiene and flammable gases (Flam. Gas 1), necessitating appropriate labeling and risk management measures.^[74] Waste raffinate is regulated under the Waste Framework Directive (2008/98/EC), which classifies it as hazardous if it exhibits highly flammable properties, prohibiting untreated disposal and requiring recycling or incineration in authorized facilities to minimize soil and water contamination. Petrochemical installations producing or using raffinate must comply with the Industrial Emissions Directive (2010/75/EU), which imposes best available techniques (BAT) reference documents for VOC emission limits, typically below 100 mg/Nm³ for point sources, and integrated pollution prevention and control (IPPC) permits. Globally, raffinate transport and storage adhere to the United Nations Recommendations on the Transport of Dangerous Goods (Model Regulations), classifying it as UN 1965 or UN 1050 (hydrocarbon gas mixture), with requirements for pressure vessels and spill containment to prevent accidental releases. These frameworks emphasize source reduction and pollution prevention, reflecting raffinate's role in broader petrochemical sustainability efforts to curb greenhouse gas emissions and ecosystem impacts. For non-petrochemical raffinates, regulations vary: hydrometallurgical raffinates are managed under mining waste directives (e.g., EU Mining Waste Directive 2006/21/EC) for metal recovery and acid mine drainage prevention; nuclear raffinates fall under IAEA standards and national atomic energy acts for radioactive waste.^[6]

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[PDF] Process Engineering and Optimization - thyssenkrupp
1). After the removal of 1, 3-butadiene from crude C4, the residual stream is termed as Raffinate 1, which contains a certain portion of isobutene.Missing: C4R1 | Show results with:C4R1
[29]
Solvent extraction of butadiene - WO2006113053A1 - Google Patents
Known solvents for this process include acetonitrile, dimethylformamide, furfural, N- methyl-2-pyrrolidone, acetone, dimethylacetamide, and the like. This ...
[30]
Enhanced process for energy efficient extraction of 1,3-butadiene ...
Jul 15, 2021 · 1,3-butadiene is an essential platform chemical for producing rubberlike polymers, which is extracted from C4 hydrocarbons that are produced ...
[31]
Raffinate 1 - Chemical Market Analytics By OPIS, a Dow Jones ...
Raffinate 1 refers to the isobutylene and butene rich stream obtained after the separation of butadiene from a steam cracker C4 rich stream.Missing: composition production properties
[32]
C4 Raffinate-1 | Dow Inc.
Produced during the steam-cracking process in the manufacture of ethylene. It is a mixture of C4 hydrocarbons and a colorless gas with a gasoline-like odor.Missing: C4R1 petrochemical
[33]
C4 Raffinate I & II - Royal Global Energy Oil, Gas, Petrochemical
The first stage of the process is to remove, by solvent extraction, the valuable butadiene which may be 40-45% of the stream. What is left is Raffinate-1.
[34]
[PDF] SAFETY DATA SHEET (SDS) C4-RAFFINATE 1. Identification
Mar 1, 2019 · Repeated exposure to. 6.25 ppm 1,3-butadiene has produced lung tumors and ovarian atrophy in females, and evidence of genetic toxicity in males ...
[35]
Relative economics of mixed C4 processing routes - DigitalRefining
A selective hydrogenation process is applied for the hydrogenation of butadiene in mixed C4 streams with a design residual of 10 to 2000 wt ppm butadiene in the ...
[36]
Grade : C4 Raffinate 1 - LG Chem On
1,3-Butadiene; ASTM; wt %; Max 1.00. Acetonitrile; ASTM; wt ppm; Max 50.0. C5'S & Heavier; ASTM; wt %; Max 0.10. DMF (or NMP); ASTM; wt ppm; Max 10.0.Missing: content | Show results with:content
[37]
[PDF] Mixed C4s Product Stewardship Summary - Shell Global
Raffinate 1 is a mixture of butenes (iso-butenes and n-butenes) with butane and residual butadiene. Raffinate 2 is produced from Raffinate 1 after iso-butenes ...Missing: composition properties<|control11|><|separator|>
[38]
Product: Raffinate-2 - ppPLUS
Dec 2, 2021 · ... Isobutylene from C4 Raffinate stream and which mainly consists of cis- or trans-2-Butene 50~60 wt%, 1-Butene 10~15 wt%, and n-Butane ~20 wt%.Missing: composition percentages
[39]
[PDF] Removal of oxygen containing compounds in a MTBE process by ...
... MTBE or TBA as impurities usually in amounts of 5 weight percent or less ... (CB-2) (plus some minor impurities including butadiene, C3's and C5's).
[40]
US8440874B2 - Olefin isomerization and metathesis catalyst
Poisons include water, CO 2, oxygenates (such as MTBE), sulfur compounds ... butene; and reactive sites for the adsorption of catalyst poisons in the feed.
[41]
Raffinate - Wikipedia
Raffinate is the liquid stream which remains after solutes from the original liquid are removed through contact with an immiscible liquid.
[42]
Special Focus: Crude C4 Market Overview
Jul 20, 2023 · Historically about 80% of the butadiene contained in global crude C4 production has been processed through extraction units to produce refined ...
[43]
Butene Production Cost Reports - Intratec.us
This study approaches 1-Butene production from raffinate-2 in the United States using a typical superfractionation process. Raffinate-3 is also generated as by- ...
[44]
Technology (M): Axens Butene-1 Superfractionation
Aug 1, 2025 · The superfractionnation technology is designed to extract high-purity, polymer-grade 1-butene from C4 raffinate streams, particularly raffinate- ...
[45]
[PDF] Effect of CsxH3ГxPW12O40 addition on the catalytic performance of ...
C4 raffinate-3 containing 57.9 wt% n-butene (1-butene (7.5 wt%)+ trans-2-butene (33.9 wt%)+cis-2-butene (16.5 wt%)) was used as a n-butene source, and air ...
[46]
[PDF] Product Safety Summary Raffinate - HubSpot
Raffinate 1 is a combination of- butenes with butane. Raffinate 2 is the hydrocarbons remaining after extraction of isobutylene. It consists of n-butenes and n- ...Missing: composition | Show results with:composition<|control11|><|separator|>
[47]
Selective hydrogenation of 1,3-butadiene in mixture with isobutene ...
Aug 9, 2025 · Butadiene is separated from this fraction by extractive distillation to produce a raffinate stream. However, the raffinate stream contains ...
[48]
C4 Raffinate Market Size, Share & Scope - Verified Market Research
Rating 5.0 (47) C4 Raffinate Market size was valued at $104.5 Bn in 2023 and is projected to reach $ 153.29 Bn by 2031, growing at a CAGR of 4.37%
[49]
Product: Raffinate-4 - ppPLUS
Dec 2, 2021 · In Naphtha cracking process, C4R4 refers to C4 residual obtained after Separation of 1,3-Butadiene, Isobutylene, 1-Butene and cis- or trans-2- ...Missing: composition | Show results with:composition
[50]
3 Processes of Separation and Transformation in C4-Chemistry
The C4-cut (raffinate II), freed from i-butene with the sulfuric acid of lower concentration, can be separated by distillation. If desired, the n-butenes can.
[51]
Process for Purification of Raffinate-2 streams - Google Patents
C4 remaining after separation of 1-butene from raffinate-2 is called raffinate-3, and the main components of raffinate-3 are trans-2-butene, cis-2-butene, n ...
[52]
Seung Hoon Oh's research works | SK Innovation and other places
A C4R4 fraction is obtained as a result of C4R3 distillation, the basic component of which is n-butane (90-96%) [134,135]. However, there is another ...
[53]
https://www.osha.gov/sites/default/files/methods/osha-pv2010.pdf
[54]
n-Butane - Chemical Market Analytics By OPIS, a Dow Jones ...
n-Butane. Back · Home | Chemical Directory | n-Butane. n ... When blended with propane and other hydrocarbons, the mixture is commercially referred to as LPG.
[55]
[PDF] Butane Blending Technical Analysis
... n-butane. With these assumptions, if butane is blended at 3 volume percent with 13.3 psi gasoline, the resultant blend RVP is around 14.9 psi. According to ...
[56]
[PDF] n-Butane Method number: PV2010 Target Concentration - OSHA
Freezing point: - 138.3 °C at 101.3 kPa (760 mmHg). Boiling point: - 0.5 °C at 101.3 kPa (760 mmHg). Flash point: - 60 °C. Autoignition point: 405 °C at 101.3 ...
[57]
Alkylation - an overview | ScienceDirect Topics
Mechanism for the alkylation of butane with butane ... raffinate stream that contains isobutane and butylene in a ratio suitable for alkylate manufacture.
[58]
[PDF] NEXOCTANE™ - Isobutylene to Premium Octane Value Component
For refinery applications NEXOCTANE™ dimerization section alone is an attractive minimum cost alternative delivering excellent blending properties of isooctene.
[59]
C₄ Fractionation - Butene-1 recovery - Axens
Butene-1 compound is a Linear Alpha-Olefin (LAO), mainly used as co-monomer in the production of poly-ethylene. Producing Butene-1, either 'on purpose' out ...
[60]
Oxidative Dehydrogenation of a C4 Raffinate‐2 towards 1,3 ...
Jul 20, 2016 · The oxidative dehydrogenation of a C4 raffinate-2 consisting of n-butane, 1-butene, and 2-butene was conducted in a two-zone fluidized bed ...
[61]
Modeling of maleic anhydride production from a mixture of n-Butane ...
Aug 6, 2025 · The aim of this work was to model the catalytic oxidation of n-butane and butenes (Raffinate II) mixture to maleic anhydride (MAN) over a ...
[62]
[PDF] The BASF Perspective - OSTI.gov
May 25, 2007 · C4. Propylene. Chemicals segment. Surfactants. Detergents. 56. Page 5. Opportunities and Challenges at the Interface between Petrochemistry and ...
[63]
Effluent valorization in copper hydrometallurgy plant - ScienceDirect
Dec 10, 2017 · During the copper extraction, the raffinate is the liquid steam which remains after copper ions from the original leachate are removed through ...
[64]
Treatment of raffinate generated via copper ore hydrometallurgical ...
Feb 15, 2020 · The raffinate generated during copper ore hydrometallurgical processing is difficult to be treated because it is strongly acidic, ...
[65]
Reactive Extraction of Penicillin G in Hollow-Fiber ... - ResearchGate
Aug 7, 2025 · ... raffinate. ... It is the purpose of this chapter to outline the general features of antibiotic purification via solvent extraction techniques as ...
[66]
Deacidification of rice bran oil by liquid–liquid extraction using a ...
Crude rice bran oil is not suitable for human consumption and must be refined, which involves dewaxing, degumming, deacidification, bleaching to improve color ...
[67]
Processing of Used Nuclear Fuel
Aug 23, 2024 · Used nuclear fuel has long been reprocessed to extract fissile materials for recycling and to reduce the volume of high-level wastes.
[68]
[PDF] Uranium Extraction Technology
This publication is one of a series of Technical Reports on uranium ore processing that have been prepared by the Division of Nuclear Fuel Cycle and Waste.
[69]
[PDF] from the durita uranium-raffinate disposal site
Feb 11, 1993 · The evaporation ponds located at the Durita disposal facility hold liquid waste from uranium and vanadium processing. Sulfuric acid leach ...
[70]
[PDF] Raffinate III - Safety data sheet
Hazard Statement: H280. Contains gas under pressure; may explode if heated. H220. Extremely flammable gas. Precautionary Statements (Prevention):. P210. Keep ...
[71]
[PDF] Material Safety Data Sheet C4 Raffinate-3
Apr 1, 2022 · 2) Signal Word: Danger. 3) Hazard Statement(s):. H220 Extremely flammable gas. H280 Contains gas under pressure; may explode if heated.Missing: C4R3 | Show results with:C4R3
[72]
Safety Data Sheet (SDS) | PDF | Dangerous Goods | Toxicity - Scribd
Signal Word : DANGER Extremely Flammable Gasses Category 1. NFPA Hazard Rating : Health = 2 Flammability = 4 Reactivity = 2 ... Common Name : C4 Raffinate-1
[73]
[PDF] Material Safety Data Sheet
C4 Raffinate-1 is extremely flammable, harmful if inhaled, may cause frostbite, anesthetic effects, and is a cancer hazard. Inhalation can cause ...
[74]
[PDF] GPS Safety Summary Raffinates - Addressee Name
Mar 23, 2016 · It is a mixture of 2-methylpropene (isobutylene), butenes, and butanes. Traces of butadiene might also be present.
[75]
Raffinates (petroleum), sorption process - Substance Details - SRS
Program & Regulatory Information. Below are the EPA applications/systems, statutes/regulations, or other sources that track or regulate this substance. This ...Missing: disposal | Show results with:disposal
[76]
Innophos Resource Conservation and Recovery Act Settlement | US EPA
No readable text found in the HTML.<|control11|><|separator|>
[77]
Substance Information - ECHA
### Summary for Raffinates (Petroleum), Solvent-Refined Light
[78]
https://echa.europa.eu/regulations/clp/understanding-clp