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Propylene oxide

Propylene oxide, also known as 1,2-epoxypropane or methyloxirane, is an organic compound with the chemical formula C₃H₆O and a molecular weight of 58.08 g/mol.^[1] It is a colorless, volatile liquid with an ethereal odor, characterized by a three-membered epoxide ring structure featuring a methyl group attached to one of the carbon atoms.^[1] Physically, it has a boiling point of 34.2 °C, a melting point of -112 °C, and a density of 0.859 g/cm³ at 20 °C, making it highly flammable with a flash point of -37 °C.^[1] Propylene oxide is primarily produced industrially through three main processes: the chlorohydrin process, which involves the reaction of propylene with hypochlorous acid followed by treatment with a base like calcium or sodium hydroxide; the indirect oxidation (peroxidation) process using propylene and an organic hydroperoxide; and the hydrogen peroxide process, a more recent direct oxidation method.^[1] In the United States, annual production has historically been significant, with estimates exceeding 1.7 billion pounds in the early 1980s; as of 2023, it exceeds 3.5 billion pounds annually, though emissions have decreased over time due to improved controls.^[2]^[3] Propylene oxide does not occur naturally on Earth and is produced almost entirely synthetically.^[4] As a key chemical intermediate, propylene oxide is predominantly used in the manufacture of polyether polyols (about 70% of usage), which serve as building blocks for polyurethane foams, elastomers, and coatings; propylene glycols (20%), employed in antifreeze, pharmaceuticals, and food additives; and glycol ethers (10%), utilized in solvents and cleaners.^[4] It also functions as a fumigant for foodstuffs like dried fruits and nuts, as well as for medical equipment sterilization, and finds minor applications in herbicides, lubricants, surfactants, and detergents.^[5] Globally, it supports diverse industries including construction, automotive, and personal care products.^[4] Propylene oxide exhibits notable toxicity, acting as an irritant to the eyes, skin, and respiratory tract, with potential for central nervous system depression at high exposures.^[5] It is classified as a possible human carcinogen (IARC Group 2B) based on sufficient evidence of tumors in experimental animals, such as forestomach and nasal cavity cancers in rodents, though evidence in humans is inadequate.^[4] Environmentally, it persists moderately in air (half-life 3-20 days) and water (11.6 days at pH 7), with low chronic toxicity to aquatic life.^[4] Regulatory limits include an OSHA permissible exposure limit of 100 ppm and a TLV of 2 ppm, reflecting its hazardous air pollutant status under U.S. EPA guidelines.^[1]^[6]

Properties

Physical properties

Propylene oxide has the molecular formula C₃H₆O and a structural formula consisting of a three-membered chiral epoxide ring with a methyl group attached to one of the carbon atoms, specifically as 2-methyloxirane.^[1] It appears as a clear, colorless volatile liquid with an ethereal odor.^[1] Key physical properties of propylene oxide are summarized in the following table:

Property	Value	Conditions
Boiling point	34.2 °C (93.6 °F)	-
Melting point	−112.1 °C (−169.8 °F)	-
Density	0.830 g/cm³	20 °C
Flash point	−37 °C (−35 °F)	-
Vapor pressure	59 kPa	20 °C
Solubility in water	410 g/L (41 wt%)	20 °C

^[1]^[7]^[8] The refractive index is 1.366 at 20 °C, and the dynamic viscosity is 0.28 mPa·s at 25 °C.^[9]^[1] Thermodynamic properties include a heat of vaporization of 28.3 kJ/mol and a liquid specific heat capacity of approximately 2.14 J/g·K.^[8]

Chemical properties

Propylene oxide is an unsymmetrical epoxide characterized by a three-membered ring in which an oxygen atom is bonded to a methylene group and a methyl-substituted carbon, imparting significant ring strain due to the compressed bond angles of approximately 60°—far from the tetrahedral ideal of 109.5°—and a total strain energy of about 27 kcal/mol.^[10] The molecule features a chiral center at the substituted ring carbon, existing as (R)- and (S)-enantiomers, though commercial propylene oxide is produced as a racemic mixture. Pure enantiomers exhibit specific rotations of [α]_D +13.5° for the (R)-form and -13.5° for the (S)-form when measured neat.^[4]^[11] As a cyclic ether, propylene oxide displays weak basicity, with the pK_a of its protonated conjugate acid around -2.4, attributable to the electron density on the strained ring oxygen that facilitates protonation but resists deprotonation.^[12] Characteristic spectroscopic features confirm the epoxide functionality: infrared spectroscopy reveals a prominent absorption at approximately 1250 cm^-1 due to the symmetric ring breathing mode. In ¹H NMR, the methyl protons appear at δ 1.3 ppm, while the ring methylene and methine protons resonate between δ 2.5 and 2.8 ppm. The ¹³C NMR spectrum shows the methyl carbon at δ 19 ppm and the ring carbons at δ 45 ppm (methylene) and δ 51 ppm (methine).^[13]^[14]^[15] Propylene oxide maintains thermal stability up to 200°C under neutral conditions but is prone to exothermic polymerization when exposed to acidic or basic catalysts, driven by the relief of ring strain.^[16]^[17]

Production

Chlorohydrin route

The chlorohydrin route represents the traditional industrial method for synthesizing propylene oxide, developed in the early 20th century and widely adopted due to its reliance on readily available chlorine. In this process, propylene reacts with hypochlorous acid (generated in situ from chlorine and water) to form a mixture of chlorohydrin isomers, primarily 1-chloro-2-propanol. This intermediate then undergoes dehydrochlorination using calcium hydroxide (lime) as the base, yielding propylene oxide along with calcium chloride as a byproduct. The overall process operates in aqueous phases, requiring multiple separation steps to isolate the product from salt-laden effluents.^[4] The key reactions are as follows: First, chlorohydrination: \ce{C3H6 + HOCl -> C3H7OCl} Followed by saponification: \ce{C3H7OCl + Ca(OH)2 -> C3H6O + CaCl2 + H2O} These steps typically achieve overall yields of 90-95% based on propylene, though the process is energy-intensive owing to the need for chlorine production, distillation, and wastewater treatment. Economically, it co-produces approximately 2 tons of calcium chloride salt per ton of propylene oxide, posing significant disposal challenges in regions without integrated salt utilization.^[18] Historically, the chlorohydrin route dominated global production, accounting for about 45% of propylene oxide capacity in the mid-2000s, particularly in areas with low-cost chlorine access such as parts of Asia and North America.^[19] As of 2025, it accounts for approximately 33-46% of global capacity, though its share has declined with the rise of less wasteful alternatives; it remains viable where chlorine is inexpensive, representing around 35-45% of output in certain markets. Key implementations include Dow Chemical's facility in Freeport, Texas, which integrated chlor-alkali production for feedstock supply until its scheduled closure by the end of 2025. Post-2010 optimizations by major operators, such as enhanced brine recycling and reduced wastewater volumes, have improved environmental performance while maintaining competitiveness.^[20]^[21]^[22]^[23]^[24]

Copoxidation route

The copoxidation route, also known as the hydroperoxide process, involves the epoxidation of propylene using organic hydroperoxides such as tert-butyl hydroperoxide or ethylbenzene hydroperoxide, catalyzed by soluble molybdenum compounds. In this method, propylene reacts with the hydroperoxide to form propylene oxide and the corresponding alcohol as a coproduct, typically tert-butanol or 1-phenylethanol, respectively. The general reaction is represented as:

\mathrm{C_3H_6 + ROOH \rightarrow C_3H_6O + ROH}

where R denotes tert-butyl or 1-phenylethyl groups.^[25]^[18] This process was introduced in 1969 through a collaboration between Halcon International and ARCO Chemical, marking a significant advancement in propylene oxide synthesis by integrating the production of valuable coproducts. As of 2025, copoxidation routes account for approximately 40% of global propylene oxide capacity, combining the propylene oxide/styrene monomer (PO/SM), propylene oxide/tert-butyl alcohol (PO/TBA), and propylene oxide/cumene (PO/Cumene) variants.^[26]^[27]^[28] Compared to the chlorohydrin route, the copoxidation process offers higher atom economy, minimizing waste by avoiding salt byproducts and generating marketable alcohols used as solvents, fuels, or chemical intermediates. Major industrial implementations include LyondellBasell's PO/SM technology, which coproduces styrene, and Shell's PO/TBA process, which yields tert-butanol. Recent expansions in Asia, such as Tianjin Petrochemical's 150,000-ton/year cumene hydroperoxide-based plant commissioned in late 2023, underscore ongoing growth in this route.^[25]^[29]^[30]

Hydrogen peroxide route

The hydrogen peroxide to propylene oxide (HPPO) process represents a direct epoxidation method for producing propylene oxide from propylene and hydrogen peroxide, catalyzed by titanium-silicalite-1 (TS-1), a zeolite-like material, yielding only water as a byproduct. The reaction proceeds as follows:

\mathrm{C_3H_6 + H_2O_2 \rightarrow C_3H_6O + H_2O}

This process typically operates in a fixed-bed reactor under mild conditions, with hydrogen peroxide often dissolved in methanol as a solvent to facilitate the reaction, achieving high propylene conversion and selectivity.^[31]^[32] Developed jointly by Dow and BASF, the HPPO process was first commercialized in 2008 with a 300,000 metric tons per year plant at BASF's facility in Antwerp, Belgium, marking a significant advancement in sustainable propylene oxide production. As of 2025, HPPO accounts for approximately 33% of global propylene oxide capacity, reflecting its rapid adoption due to environmental advantages over traditional routes.^[31]^[28] Key advantages of the HPPO process include hydrogen peroxide selectivity exceeding 99%, minimizing waste generation and eliminating salt or organic coproducts common in other methods, which reduces wastewater by 70-80% and energy consumption by 35% compared to the chlorohydrin route. It also integrates seamlessly with on-site hydrogen peroxide production via the anthraquinone process, enhancing overall efficiency and reducing transportation needs.^[31]^[33] Recent developments underscore HPPO's growth, with Evonik and thyssenkrupp Uhde licensing technology for multiple plants in Asia, including the world's first industrial-scale facility in Ulsan, South Korea (2008, 100,000 tons per year), a 300,000 tons per year plant in Jilin, China (2014), and a new complex in Zibo, China (2023, 240,000 tons per year). While bio-based hydrogen peroxide pilots are emerging in China to further green the process, no large-scale integrations with HPPO have been commercialized as of 2025.^[34]^[35]^[36]

Reactions

Ring-opening reactions

Propylene oxide, as an unsymmetrical epoxide, exhibits characteristic ring-opening reactivity driven by the strain in its three-membered ring. Under basic conditions, nucleophiles attack the less substituted (terminal) carbon via an SN2-like mechanism, resulting in inversion of configuration at that site and formation of the anti addition product. This regioselectivity arises because the transition state minimizes steric hindrance at the primary carbon. In acidic conditions, protonation of the oxygen enhances the electrophilicity of the epoxide, shifting the nucleophilic attack to the more substituted (secondary) carbon, which develops partial positive charge more readily, akin to an SN1 pathway with neighboring-group participation. These mechanistic differences allow selective control over product regiochemistry in synthetic transformations.^[37] A prominent example is the hydrolysis of propylene oxide to produce propylene glycol (1,2-propanediol), typically conducted under acidic conditions to favor attack at the secondary carbon. The reaction proceeds as follows:

\ce{C3H6O + H2O ->[H+] CH3CH(OH)CH2OH}

Industrially, this process uses excess water and achieves yields of over 90%, with the primary product being the 1,2-diol and minor higher glycols as byproducts.^[38] Alcoholysis involves the reaction of propylene oxide with alcohols in the presence of base, such as NaOH, yielding β-hydroxy ethers. For instance, with methanol, the nucleophilic attack occurs at the less substituted carbon under basic conditions, producing 1-methoxy-2-propanol as the major isomer. The general reaction is:

\ce{C3H6O + ROH ->[base] CH3CH(OH)CH2OR}

This transformation is catalyzed efficiently by solid bases like MgO, with mechanisms involving surface-bound alkoxide intermediates.^[39] Aminolysis reactions with amines, including ammonia, lead to β-amino alcohols. Reaction with ammonia under controlled conditions yields isopropanolamine (1-amino-2-propanol) via nucleophilic ring opening at the terminal carbon. These processes are sequential, producing mono-, di-, and tri-substituted products depending on amine excess and conditions.^[40] Anionic polymerization of propylene oxide, initiated by potassium hydroxide (KOH), produces polyether polyols used in polyurethane foams. The mechanism begins with deprotonation of an initiator alcohol (e.g., water or polyol) by OH⁻ to form an alkoxide, which attacks the less substituted carbon of propylene oxide in an SN2 manner, opening the ring and generating a new alkoxide chain end. Propagation occurs through repeated nucleophilic attacks by this alkoxide on additional monomer units, leading to chain growth with head-to-tail linkages and secondary hydroxyl end groups. Termination can involve protonation or end-capping agents, yielding polymers with molecular weights controlled by monomer-to-initiator ratio. This process typically operates at 70–120 °C in bulk, with KOH providing high activity but potential for side reactions like chain transfer.^[17]

Rearrangement and oxidation reactions

Propylene oxide can undergo thermal rearrangement in the gas phase at temperatures between 250 and 300°C when passed over alumina catalysts, yielding allyl alcohol as the major product and propionaldehyde as a minor product. This process exploits the inherent ring strain in the epoxide structure to facilitate skeletal isomerization without nucleophilic addition. The primary reaction pathway is depicted by the equation:

\ce{C3H6O ->[Al2O3][250-300^\circ C] CH2=CHCH2OH}

Selectivity toward allyl alcohol exceeds 60-80% under optimized conditions, with the minor propionaldehyde formation arising from competing hydrogen migration pathways.^[41]^[42] Acid-catalyzed isomerization of propylene oxide proceeds via protonation of the epoxide oxygen by protic acids (H⁺) or coordination with Lewis acids, leading to ring opening and subsequent 1,2-hydride shift to form either acetone or propanal. Acetone is favored on stronger acid sites due to migration from the substituted carbon, while propanal predominates on milder acidic surfaces through terminal carbon involvement. These transformations occur at lower temperatures (100-200°C) compared to thermal routes and are mediated by catalysts such as metal phosphates or zeolites, with quantum chemical calculations confirming single-transition-state mechanisms for each product.^[42]^[43] Hydrogenolysis of propylene oxide over nickel catalysts, such as Raney nickel or supported Ni variants, effects reductive ring opening to yield primarily 1-propanol, with minor 2-propanol depending on reaction conditions like hydrogen pressure and temperature (typically 100-200°C). The nickel surface promotes selective cleavage at the less substituted C-O bond, favoring anti-Markovnikov alcohol formation, and this method offers high regioselectivity compared to platinum-based systems.^[44] Photochemical reactions of propylene oxide under UV irradiation (e.g., 185 nm) induce ring opening via radical intermediates, generating propanal and acetone as primary products through C-O bond homolysis and subsequent hydrogen abstraction. However, radical yields remain low due to rapid recombination and competing isomerization channels, limiting practical applications. Reactive force field simulations confirm the radical-mediated pathways but highlight inefficient quantum yields under standard conditions.^[45] In laboratory settings, small-scale conversions of propylene oxide to aldehydes, such as propionaldehyde, are achieved via controlled isomerization over chromia-tungstia catalysts at mild temperatures, providing a route for synthetic intermediates without large-scale optimization. These niche transformations emphasize the epoxide's versatility for targeted organic synthesis.^[46]

Uses

Major industrial uses

Propylene oxide (PO) is predominantly utilized in the production of polyether polyols, which account for approximately 60-70% of global PO consumption.^[47] These polyols are synthesized through the ring-opening reaction of PO with water or glycols, serving as key building blocks for polyurethane products such as flexible and rigid foams used in furniture, bedding, insulation, and automotive components, as well as adhesives and sealants.^[4] Global consumption of polyether polyols reached over 9.8 million metric tons in 2023.^[48] A significant portion, about 20-30% of PO production, is directed toward propylene glycol (PG) via hydrolysis processes that yield high-purity products suitable for diverse applications.^[47] PG finds widespread use as an antifreeze in automotive coolants, a humectant and solvent in food additives, and a carrier in pharmaceuticals, with USP-grade variants produced under stringent purification to meet regulatory standards for medical and consumable uses.^[49] Annual global production of PG approximates 2 million tons as of recent estimates.^[50] Propylene glycol ethers, formed by the etherification of PO with alcohols, represent another major industrial outlet, serving as versatile solvents in formulations for paints, coatings, and industrial cleaners.^[4] Examples include dipropylene glycol monomethyl ether, valued for its low toxicity and effective solvency in water-based systems.^[51] The overall PO market was valued at approximately USD 22 billion in 2024, with demand expected to grow at a compound annual growth rate (CAGR) of around 5% through 2033, fueled by rising needs in construction for insulation materials and automotive for lightweight components.^[52]

Niche and specialized uses

Propylene oxide serves as an EPA-approved fumigant for sterilizing raw almonds and other nuts, with approval for post-harvest treatment established in the mid-2000s to reduce microbial contamination such as bacteria, yeasts, and molds.^[53] The process involves exposing nutmeats to propylene oxide vapor, which penetrates shells and kills insects and pathogens effectively due to its volatility, leaving residues below the EPA tolerance of 10 ppm for tree nuts and processed nutmeats, often dissipating to less than 1 ppm shortly after treatment.^[54]^[55] In electron microscopy, propylene oxide acts as a transitional solvent during tissue preparation, facilitating dehydration after fixation and enabling resin infiltration to preserve cellular ultrastructure for high-resolution imaging.^[56] It is typically employed in graded concentrations, including 1-3% solutions in protocols to stabilize samples without distorting fine details, replacing more hazardous alternatives in some modern workflows.^[57] Propylene oxide is utilized as a fuel component in thermobaric weapons, such as fuel-air explosives, where it aerosolizes to create a high-pressure blast wave enhanced by its rapid combustion properties.^[58] The U.S. military has incorporated such systems since the 1990s, leveraging propylene oxide's ability to form explosive vapor clouds in munitions for increased destructive radius. (Note: The 2023 Fuel journal article references historical military applications.) Beyond these, propylene oxide functions as a sterilant for medical devices, applied in gas-phase processes to eliminate microorganisms on heat-sensitive equipment like immunoadsorbents without residue buildup.^[59] It also serves as an intermediate in synthesizing nonionic surfactants, such as alcohol ethoxylates modified with propylene oxide segments to improve solubility and performance in formulations.^[60] Additionally, it acts as a racing fuel additive to boost oxygen content and power output by up to 8%, though its use is restricted in many sanctioned events due to regulatory prohibitions on performance enhancers.^[61]^[62] In recent developments, bio-based propylene oxide derived from renewable feedstocks has entered pilot-scale production in the 2020s for applications in sustainable polymers, including polyols for polyurethane foams, with market projections indicating growth from USD 0.8 billion in 2024 to USD 2.1 billion by 2034 driven by environmental demands.^[63]

Safety and health effects

Toxicity and carcinogenicity

Propylene oxide is an irritant to the eyes, skin, and respiratory tract upon acute exposure, causing symptoms such as redness, tearing, coughing, and pulmonary edema in severe cases. In animal studies, the 4-hour inhalation LC50 in rats is approximately 4000 ppm, while the oral LD50 in rats ranges from 382 to 587 mg/kg body weight.^[5]^[64] Chronic exposure to propylene oxide leads to genotoxic effects through its action as a direct alkylating agent, forming adducts with DNA nucleophiles such as guanine, which can result in mutations. It is classified as a Group 2B carcinogen (possibly carcinogenic to humans) by the International Agency for Research on Cancer, based on sufficient evidence from animal studies but inadequate evidence in humans. In rodents, inhalation exposure at 500 ppm induced forestomach tumors, primarily squamous-cell carcinomas, while lower levels around 300 ppm were associated with increased mammary gland tumors in female rats; subcutaneous or oral administration also produced local tumors at the site of contact. Although no clear causal link to cancer has been established in humans, limited occupational studies suggest a potential association with leukemia, though confounding factors like co-exposure to other chemicals limit conclusions.^[64]^[65] Occupational exposure limits for propylene oxide include an OSHA permissible exposure limit (PEL) of 100 ppm as an 8-hour time-weighted average; NIOSH classifies it as a potential occupational carcinogen with no numerical REL, recommending reduction to the lowest feasible level; and an ACGIH TLV of 2 ppm as an 8-hour TWA, reflecting its carcinogenic potential. In vivo, propylene oxide is rapidly metabolized primarily to propylene glycol, a less toxic compound, via epoxide hydrolase and glutathione conjugation, which mitigates some systemic effects. Regarding reproductive and developmental toxicity, animal inhalation studies in rats showed no adverse effects on fetuses at exposure levels up to 300 ppm, but increased fetal resorptions occurred at 500 ppm alongside maternal toxicity; in vitro assays indicate weak mutagenic potential, though no strong evidence of heritable genetic damage exists.^[66]^[67]^[5]^[68]

Flammability and exposure risks

Propylene oxide is classified as a Class IA flammable liquid due to its low flash point of -35°F (-37°C) and boiling point below 100°F (38°C), making it highly susceptible to ignition.^[67] Its autoignition temperature is 465°C (869°F), and it forms explosive vapor-air mixtures over a wide range of 2.3-36% by volume.^[1] The National Fire Protection Association (NFPA) rates it as 3 for health hazards, 4 for flammability, and 2 for instability, indicating severe fire risks and potential for violent polymerization under heat or contamination.^[66] Vapors of propylene oxide are heavier than air and can travel considerable distances to ignition sources, leading to flash fires or explosions; additionally, static electricity poses a significant ignition risk during transfer and handling operations.^[69] To mitigate these hazards, storage should occur in cool, well-ventilated areas under an inert nitrogen blanket to prevent polymerization, using explosion-proof equipment and grounded containers to eliminate static discharge.^[70] Non-sparking tools and bonding/grounding procedures are essential during handling to avoid sparks.^[1] Primary exposure routes for propylene oxide are inhalation of vapors and dermal absorption through skin contact, as it is readily absorbed and can cause acute irritation or burns.^[67] Personal protective equipment (PPE) includes full-face respirators with organic vapor cartridges or self-contained breathing apparatus for airborne exposures above permissible limits, along with chemical-resistant suits made of butyl rubber or Teflon, gloves, and goggles to prevent skin and eye contact.^[70] A notable historical incident occurred on July 5, 1990, at the ARCO Chemical plant in Channelview, Texas, where a runaway polymerization reaction in a propylene oxide production unit led to an explosion that killed 17 workers and injured five others, highlighting the dangers of inadequate temperature control and contaminant management.

Environmental aspects

Emissions and persistence

Propylene oxide is released into the environment primarily through fugitive emissions during its industrial production and use, with significant contributions from the chlorohydrin process where it appears in wastewater streams alongside chlorinated byproducts. Fugitive emissions, arising from leaks in equipment such as valves, pumps, and storage tanks, are estimated at 0.1–1 kg per metric ton of propylene oxide produced, based on industry emission factors for organic chemicals in petrochemical facilities. In the chlorohydrin route, which accounts for a substantial portion of global production, wastewater treatment releases additional propylene oxide, contributing to aquatic discharges. As of 2024, global production was approximately 10.1 million metric tons, with projections for growth to 10.6 million in 2025.^[71] Annual environmental releases are estimated at 0.1–1 kg per metric ton produced, leading to totals in the thousands of metric tons globally, though actual amounts have decreased due to improved controls.^[31] In the atmosphere, propylene oxide exists predominantly in the vapor phase due to its volatility and undergoes degradation mainly through reaction with photochemically produced hydroxyl (OH) radicals, with an estimated half-life of 10–20 days under typical tropospheric conditions. Photolysis contributes to its breakdown, yielding products such as formaldehyde and methyl radicals, though this pathway is secondary to OH-initiated oxidation. The primary degradation mechanism involves ring-opening by OH, leading to oxygenated intermediates that further react to form compounds like acetaldehyde and peroxyacetyl nitrate (PAN). These processes limit long-range atmospheric transport, as the compound does not persist beyond regional scales.^[4]^[72]^[73] In aqueous environments such as water bodies and soil pore water, propylene oxide hydrolyzes rapidly to propylene glycol via acid- or base-catalyzed ring-opening, with a half-life of approximately 11.6 days at pH 7 and 25°C; this rate accelerates at more extreme pH values, dropping to about 6–12 days.^[4] The hydrolysis product, propylene glycol, is biodegradable and non-toxic at environmental concentrations. In soil, propylene oxide exhibits high mobility due to its low adsorption potential but degrades similarly through hydrolysis and microbial activity. Its octanol-water partition coefficient (log Kow) of 0.03 indicates negligible bioaccumulation potential in aquatic organisms, as it preferentially remains in the water phase rather than partitioning into lipids.^[74]^[75] Overall, propylene oxide demonstrates low environmental persistence owing to its reactivity and volatility, characterized by a Henry's law constant of approximately 7 × 10^{-5} atm·m³/mol, which facilitates rapid evaporation from water surfaces. It does not meet criteria for persistent, bioaccumulative, and toxic (PBT) substances, as its degradation half-lives are short and bioaccumulation factor is minimal. Recent shifts toward the hydrogen peroxide-based propylene oxide (HPPO) process have reduced emissions of chlorinated byproducts and wastewater volumes by 70–80% compared to traditional routes, improving local air and water quality. A October 2025 report faulted the EPA for underassessing risks in Cancer Alley, highlighting volatile organic compound concerns near petrochemical plants including those producing epoxides like propylene oxide, prompting enhanced monitoring efforts.^[76]^[31]^[77]

Regulations and sustainability

Propylene oxide is regulated under the U.S. Environmental Protection Agency's Toxic Substances Control Act (TSCA) as an active chemical substance subject to testing requirements and risk evaluations.^[78] It is also listed as a hazardous air pollutant (HAP) under the Clean Air Act, where emissions are controlled to limit volatile organic compounds (VOCs) from industrial sources, including wastewater and equipment leaks in production facilities.^[79] In 2025, the EPA received a petition to establish tolerances for residues of propylene oxide on various dried vegetables and spices, aiming to set permissible levels for its use as a fumigant in food processing.^[80] The EPA has classified propylene oxide as a probable human carcinogen (Group B2), influencing its regulatory scrutiny for environmental and health risks.^[5] In the European Union, emission controls for propylene oxide production emphasize best available techniques (BAT) to minimize waste gas releases, with typical post-treatment emission levels for propylene oxide maintained below 0.5 mg/m³ in modern plants.^[81] BAT reference documents require integrated management of diffuse VOC emissions and wastewater to reduce overall environmental impact from chemical manufacturing.^[82] Under the Clean Air Act in the U.S., VOC emission standards apply to synthetic organic chemical manufacturing, including controls on storage, handling, and flaring to prevent releases during propylene oxide synthesis. Sustainability efforts in propylene oxide production are shifting toward low-carbon methods, such as the hydrogen peroxide to propylene oxide (HPPO) process using green hydrogen peroxide derived from renewable energy sources, which produces only water as a byproduct and significantly cuts waste compared to traditional routes.^[83] Bio-based processes utilizing bio-propylene from renewable feedstocks like glycerol or bio-ethanol are also emerging to lower the carbon footprint of the supply chain.^[83] The global market for low-carbon propylene oxide is projected to grow at a compound annual growth rate (CAGR) of 6.3% through 2034, driven by demand for eco-friendly alternatives in polyurethanes and glycols.^[83] Global initiatives include the EU Emissions Trading System (ETS), which mandates a 62% reduction in covered emissions by 2030 compared to 2005 levels, applying to propylene oxide facilities through carbon pricing on greenhouse gas releases.^[84] Major producers like LyondellBasell have pledged carbon neutrality by 2050, with interim targets for a 42% absolute reduction in Scope 1 and 2 emissions by 2030, supporting broader industry transitions via renewable energy integration.^[85] Challenges persist with legacy waste from the chlorohydrin process, which generates substantial calcium chloride solids and polluted wastewater, complicating remediation in older sites.^[86] Additionally, proposed 2025 EPA rollbacks on chemical risk assessment procedures and petrochemical emission standards are under review, potentially easing controls on VOCs and HAPs from production.^[87]

Occurrence

Extraterrestrial detection

Propylene oxide (CH₃CHCH₂O) was first detected in the interstellar medium in 2016 toward the Sagittarius B2 North (Sgr B2(N)) molecular cloud complex near the Galactic center, marking the initial identification of a chiral molecule in space.^[88] The detection was achieved through radio observations using the Green Bank Telescope (GBT) in West Virginia and the Parkes radio telescope in Australia, revealing absorption features from low-energy rotational transitions of the molecule.^[88] These transitions, observed primarily in the 12–14 GHz frequency range (e.g., the 2_{1,1}–2_{0,2} line at approximately 12.8 GHz), indicated a cold molecular environment with an excitation temperature of about 5 K.^[88] The derived column density was approximately 1 × 10^{13} cm^{-2}, consistent with a low-abundance species in an extended, quiescent envelope surrounding the region's massive protostellar clusters.^[88] Spectral analysis confirmed the presence of both enantiomers—(R)-propylene oxide and (S)-propylene oxide—in equal proportions, forming a racemic mixture with no detectable enantiomeric excess.^[88] This observation was supported by laboratory spectra of the individual enantiomers, which showed indistinguishable rotational signatures under the telescope's resolution, precluding differentiation of any potential asymmetry.^[88] Proposed formation pathways for interstellar propylene oxide include gas-phase ion-molecule reactions, such as the addition of hydroxyl (OH) radicals to propene (C₃H₆), though kinetic barriers and low efficiencies in cold environments limit this route's viability.^[89] More favorable mechanisms involve ice-mantle chemistry on dust grains, where suprathermal atomic oxygen atoms react with adsorbed propene in interstellar ices, potentially driven by cosmic ray-induced radiolysis or UV photolysis.^[90] These surface reactions yield racemic propylene oxide, aligning with the observed equal enantiomer distribution and offering insights into prebiotic chirality emergence.^[90] The detection holds significant implications for astrobiology, as propylene oxide represents a complex organic molecule capable of forming in non-terrestrial conditions, bridging simple interstellar chemistry to potential precursors of life's building blocks.^[91] However, the lack of enantiomeric excess challenges hypotheses of cosmic origins for biomolecular homochirality, suggesting that any preferential handedness in life's molecules may arise later, perhaps on planetary surfaces or via amplification mechanisms.^[91] Follow-up observations in the 2020s, including targeted searches in cold dark clouds like TMC-1, have yielded negative results for propylene oxide, consistent with its preferential association with warmer, more chemically active regions like Sgr B2(N).^[91] Astrochemical models predict fractional abundances of propylene oxide relative to H₂ on the order of 10^{-11} in such environments, aiding in the interpretation of non-detections and guiding future surveys for chiral species.^[92]

Terrestrial traces

Propylene oxide is not known to occur as a natural product and has no known biogenic sources on Earth. It forms transiently in the atmosphere through the oxidation of hydrocarbons during combustion processes, such as in vehicle exhaust and other fossil fuel burning activities.^[93] Trace detections of propylene oxide have been reported in urban air at low concentrations attributable to emissions from vehicle exhaust and industrial activities. In tobacco smoke, concentrations range from 0.65 to 0.93 µg per cigarette in reference cigarettes analyzed by gas chromatography-mass spectrometry.^[2] In food, minor residues of propylene oxide occur in some spices, processed nuts, and cocoa powder following fumigation treatments, though it is not endogenous to these products. It degrades rapidly to propylene glycol in moist environments. In the United States, regulatory tolerances for residues of the fumigant propylene oxide (measured as propylene oxide) are set at 300 ppm for nutmeats (except peanuts) and dried spices (group 19), and 200 ppm for cocoa powder (cacao bean).^[5]^[54] Environmentally, propylene oxide has been detected in groundwater near industrial facilities at concentrations below 1 µg/L, where it degrades quickly via hydrolysis with a half-life of approximately 12 days at neutral pH. No significant natural reservoirs exist, and it is absent in pristine ecosystems, such as remote forests and oceans, underscoring its anthropogenic origin.^[93]^[5]

References

[1]
Propylene Oxide
Summary of each segment:
[2]
[PDF] Propylene Oxide - OSHA
The estimated U.S. production of propylene oxide in 1980 was 1,767 million pounds. It is used primarily as an intermediate for the manufacture of polyether.
[3]
Propylene Oxide - Some Industrial Chemicals - NCBI Bookshelf
Propylene oxide is used primarily to produce polyether polyols, propylene glycols and propylene glycol ethers. It is certified for use as a package fumigant for ...<|control11|><|separator|>
[4]
[PDF] Propylene oxide - U.S. Environmental Protection Agency
Propylene oxide has been observed to cause tumors at or near the site of administration in rodents, causing forestomach tumors following ingestion via gavage ( ...
[5]
[PDF] 1998-01-29 Propylene Oxide As A Federal Hazardous Air Pollutant ...
Propylene oxide is a federal hazardous air pollutant and was identified as a toxic air contaminant in April 1993 under AB 2728. CAS Registry Number: 75-56-9.
[6]
ICSC 0192 - PROPYLENE OXIDE
Relative density (water = 1): 0.83. Solubility in water, g/100ml at 20°C: 40. Vapour pressure, kPa at 20°C: 59. Relative vapour density (air = 1): 2.0. Relative ...Missing: refractive index specific
[7]
Propylene oxide
### Summary of Propylene Oxide Data from NIST Chemistry WebBook
[8]
75-56-9(Propylene oxide) Product Description - ChemicalBook
Boiling point: 34 °C(lit.) ; Density, 0.83 g/mL at 25 °C(lit.) ; vapor density, 2 (vs air) ; vapor pressure, 29.43 psi ( 55 °C) ; refractive index, n 20/D 1.366(lit ...
[9]
Epoxides - The Outlier Of The Ether Family - Master Organic Chemistry
Jan 26, 2015 · The interior bond angles of epoxides are about 60°. Contrast that with the “ideal” bond angle of 109.5° for tetrahedral carbon, and you'll ...Missing: propylene | Show results with:propylene<|control11|><|separator|>
[10]
https://www.masterorganicchemistry.com/2015/01/26/epoxides-the-outlier-of-the-ether-family/
[11]
[PDF] pka-compilation-williams.pdf - Organic Chemistry Data
Apr 7, 2022 · Itaconic (1-Propene-2-3-dicarboxylic acid). 3.85, 5.45. 2. Chloromaleic. 1.72, 3.86. 2. Provided by the ACS, Organic Division. Updated 4/7/2022.
[12]
Epoxides and Ethers - ScienceDirect
The vapor-phase IR bands near 1269, 839, and 959 cm-1 are assigned as ring breathing, symmetric ring deformation, and antisymmetric ring deformation, ...
[13]
Propylene oxide(75-56-9) 1H NMR spectrum - ChemicalBook
ChemicalBook Provide Propylene oxide(75-56-9) 1H NMR,IR2,MS,IR3,IR,1H NMR,Raman,ESR,13C NMR,Spectrum.
[14]
Propylene oxide(75-56-9) 13C NMR spectrum - ChemicalBook
Shift(ppm) A 2.979 B 2.745 C 2.427 D 1.316. Hz ppm Int. 278.50 3.110 32 ... Jinan Qinmu Fine Chemical Co.,Ltd. TopScience Biochemical · Hubei xin bonus ...Missing: shifts | Show results with:shifts
[15]
Study on the reaction mechanism of the propylene oxide ...
The studies shows that the propylene oxide rearrangement involves thermal and catalytic transformation above 200 °C.
[16]
Polymerization of Ethylene Oxide, Propylene Oxide, and Other ...
Dec 29, 2015 · They are active in the temperature range 0 °C – 50 °C. This is unusual, considering that alkaline earth carbonates and oxides require much ...
[17]
[PDF] Development of New Propylene Oxide Process
The new PO process uses a titanium epoxidation catalyst with cumene as oxygen carrier, producing higher yields and less byproducts than conventional methods.
[18]
Propylene Oxide Routes Take Off - C&EN
Oct 9, 2006 · The oldest route, the chlorohydrin process, uses chlorine and propylene to produce propylene chlorohydrin as an intermediate. This process, ...Missing: 2000s | Show results with:2000s<|control11|><|separator|>
[19]
Olin to shut diaphragm chloralkali capacity that serves Dow's ... - ICIS
Dec 12, 2024 · Olin plans to shut down its diaphragm-grade chloralkali capacity in Freeport, Texas, that provides feedstock to Dow's propylene oxide (PO) unit.
[20]
Methods and systems to form propylene chlorohydrin and propylene ...
[86] In the traditional chlorohydrin process, the PCH may be formed through the addition of hypochlorous acid (HOC1) to the propylene. The HOC1 may itself be ...
[21]
The Production of Propene Oxide: Catalytic Processes and Recent ...
This paper discusses the existing processes used for the production of propene oxide the chlorohydrin and hydroperoxide processes and their advantages and ...
[22]
Equistar Chemicals, LP -- Company History
With Halcon International it forged a joint venture in 1966 called Oxirane Chemical Company, which used a Halcon-developed process to produce propylene oxide.Missing: introduction | Show results with:introduction
[23]
Process Data set: Propylene oxide production; technology mix
May 13, 2017 · The production process modelled in this dataset is a mix of five production processes: the chlorohydrin process (41%), the propylene oxide ...
[24]
Technology (M): Lyondellbasell PO/SM - ppPLUS
Mar 13, 2025 · The POSM process was originally developed by ARCO Chemical Company as part of its innovations in propylene oxide production. ARCO Chemical was a ...<|control11|><|separator|>
[25]
Propylene oxide new capacity of 1.52 million tons in 2023-2024 ...
The 150000-ton/year CHP propylene oxide (CHPPO) plant of Tianjin Petrochemical Company was successfully started at one time and successfully produced qualified ...Missing: Asia | Show results with:Asia
[26]
Presidential Green Chemistry Challenge: 2010 Greener Synthetic ...
Oct 8, 2025 · Dow and BASF have jointly developed a new route to make propylene oxide with hydrogen peroxide that eliminates most of the waste and greatly reduces water and ...
[27]
[PDF] The new HPPO Process for Propylene Oxide - Aidic
The HPPO process uses hydrogen peroxide and a TS-1 zeolite catalyst in a tubular reactor with methanol to produce propylene oxide.
[28]
How Propylene Oxide is Undergoing a Green Transformation?
Oct 9, 2025 · For example, the chlorohydrin process consumes 5 tons of chlorine ... tons of calcium chloride waste residue for every ton of propylene oxide ...Missing: salt | Show results with:salt
[29]
Hydrogen Peroxide to Propylene Oxide (HPPO) Process
The production of wastewater is reduced by 70-80%, and energy use is reduced by 35%. This process has high yields and only produces water as a byproduct.
[30]
HPPO Technology - Evonik Active Oxygens
The capacity of this first-of-its-kind HPPO plant was then increased to 130,000 metric tons of propylene oxide per year. SKC uses the capacity for further ...
[31]
Sustainable production of propylene oxide begins at new HPPO ...
Sep 5, 2023 · Operations have begun at leading chemical producer Qixiang Tengda's new propylene oxide complex in Zibo City, China, using technology from Evonik and ...Missing: Asia | Show results with:Asia
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Green H2O2 Production, Olefin Oxidation & Ammoximation Bases
This review overviews China's unique green chemical technologies for H 2 O 2 production and hydrocarbon oxidation/ammoximation with the global market share ...<|control11|><|separator|>
[33]
Opening of Epoxides With Acid - Master Organic Chemistry
Feb 2, 2015 · Epoxides can undergo ring-opening with nucleophiles under acidic conditions. · In this reaction, the epoxide oxygen is protonated first, making ...
[34]
US2623909A - Hydrolysis of 1, 2-propylene oxide ... - Google Patents
92% of the 1,2-propylene oxide is hydrolyzed and converted to glycols of which 88.5% is 1,2-propylene glycol and 11.5% dipropylene glycol. Example II 100 parts ...
[35]
The mechanism for the synthesis of 1-methoxy-2-propanol from ...
The addition of propylene oxide with methanol was carried out over solid bases and a detailed mechanism of the reaction over MgO was investigated by using ...
[36]
Alkanolamines from Olefin Oxides and Ammonia - Wiley Online Library
Isopropanolamines, NH3-n (CH2CHOHCH3)n (mono-, di-, and tri-), result from the reaction of ammonia with propylene oxide. Secondary butanolamines, NH3-n (CH2 ...Missing: aminolysis | Show results with:aminolysis
[37]
Catalytic production of allyl alcohol from propylene oxide
The catalytic conversion of propylene oxide to allyl alcohol is conducted at a temperature range of 250 to 550 C., in which the narrow range of 300 to 400 C. is ...Missing: thermal | Show results with:thermal
[38]
Isomerization of Propylene Oxide. Quantum Chemical Calculations ...
The potential energy profiles of the isomerization of propylene oxide to acetone, propanal, and allyl alcohol contain one transition state each, indicating ...
[39]
The Isomerization of Propylene Oxide on Metal Oxides and Silica ...
The main products of the reaction were propionaldehyde, acetone, allyl alcohol,. 1-propanol, and acrolein. Propionaldehyde and acetone are produced on acidic ...Missing: propanal | Show results with:propanal
[40]
Promoter effects in the Pt-catalysed oxidation of propylene glycol
Oxidation of propylene glycol towards pyruvic acid proceeds via two pathways, one via hydroxyacetone, the second via lactic acid. Experiments, performed under ...
[41]
Hydrogenation of Epoxides to Anti‐Markovnikov Alcohols over a ...
Dec 19, 2022 · The supported nickel catalyst (Ni/RH) was prepared by wet impregnation of RH with Ni(NO3)2 followed by pyrolysis at 700 °C under inert ...
[42]
Investigating the Photolysis Mechanism of Propylene Oxide Using ...
Apr 21, 2025 · The results suggested that photolysis of PO under UV-CPL irradiation could contribute to chiral symmetry breaking. However, the detailed ...
[43]
Catalytic isomerization of propylene oxide to propionaldehyde ...
I have now discovered that the catalytic isomerization of propylene oxide to propionaldehyde can be conducted in the presence of a chromicoxide-tungstic oxide ...Missing: propanal | Show results with:propanal
[44]
Propylene Oxide Market size worth $ 32.56 Billion, Globally, by 2028 ...
Jan 13, 2022 · Currently, around two-thirds of PO output is utilized to make polyether polyols, with the remaining 17 percent going to propylene glycols (PG) ...
[45]
Polyether Polyols Market Size, Price and Industry Forecast, 2034
Apr 7, 2025 · The global market for Polyether Polyols reached a valuation of USD 17.6 billion in 2023, and with projected to surpass USD 29 billion by 2032, exhibiting a ...
[46]
Propylene Glycol Market Size & Share | Industry Report, 2030
Propylene glycol is manufactured from propylene oxide. The most commonly ... In May 2024, Dow announced the completion of an 80,000-ton annual propylene ...
[47]
propylene glycol market size & share analysis - Mordor Intelligence
Apr 14, 2025 · In 2024, the Propylene Glycol Market size was estimated at 4.07 million tons. The report covers the Propylene Glycol Market historical ...
[48]
What are Glycol Ethers?
P-series glycol ethers are based on reacting propylene oxide with varying chain alcohols. They are used for paints and coatings, cleaners, inks, and a variety ...
[49]
Propylene Oxide Market Size, Share and Forecast to 2033
The global propylene oxide market size reached a value of USD 22.0 Billion in 2024 and grow at a CAGR of 4.6% to reach USD 33.1 Billion by 2033.Propylene Oxide Industry... · Europe Propylene Oxide... · Competitive Landscape<|control11|><|separator|>
[50]
Almond Pasteurization Program | Almond Processing Safety
Propylene Oxide (PPO) Exposure of nuts to an EPA approved fumigant treatment that rapidly dissipates after exposure. Appropriate for conventional almonds.
[51]
40 CFR 180.491 -- Propylene oxide; tolerances for residues. - eCFR
§ 180.491 Propylene oxide; tolerances for residues. ; Nut, tree, group 14, 10.0 ; Nutmeat, processed, except peanuts, 10.0 ; Onion, dried, 6000 ; Pistachio, 10.0.
[52]
Propylene Oxide; Tolerance Actions - Federal Register
May 15, 2012 · EPA is establishing the tree nut crop group tolerance and separate tolerances on pistachio and pine nuts for both the fumigant propylene oxide ...
[53]
Propylene Oxide: To Use or Not to Use in Biological Tissue Processing
Aug 9, 2025 · Propylene oxide (1,2-epoxy propane) has long been utilized as a transitional solvent in the preparation of biological tissues.
[54]
https://www.ecfr.gov/current/title-40/chapter-I/subchapter-E/part-180/subpart-C/section-180.491
[55]
Explosion behaviors of vapor–liquid propylene oxide/air mixture ...
Propylene oxide (PO) is widely used in fuel–air explosive (FAE) and pulse detonation engines (PDE). The explosion process of PO/air mixture in a 20 L ...<|separator|>
[56]
Propylene oxide (EHC 56, 1985) - INCHEM
Propylene oxide can be produced by the chlorohydrin process or by peroxidation. In the first of these processes, 1-chloro-2- propanol and 2-chloro-1-propanol ...<|control11|><|separator|>
[57]
Nonionic surfactants containing propylene oxide
The influence of PO on surfactant properties was assessed for several alcohol ethoxylates and nonyl-phenol ethoxylates.Missing: intermediate | Show results with:intermediate<|separator|>
[58]
HPBG: The Power of Racing Fuels - Engine Builder Magazine
Additives such as propylene oxide can increase power 7 to 8% with no changes in carburetor jetting. Fuel suppliers say oxygenated fuels can typically make ...Missing: regulations | Show results with:regulations
[59]
Race Fuels | Southern Race Fules
Our propylene oxide actually increases a fuels' oxygen content and is guaranteed to work with any fuel. Sunoco Nitromethane, with a purity rating greater ...Missing: regulations | Show results with:regulations
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https://link.springer.com/article/10.1007/BF02663954
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[PDF] Report on Carcinogens, Fifteenth Edition - Propylene Oxide
Administration of propylene oxide by stomach tube caused forestomach cancer (primarily squa- mous-cell carcinoma) in female rats, and subcutaneous injection.
[62]
CIB 51: Carcinogenic Effects of Exposure to Propylene Oxide | NIOSH
Recent studies of the chronic effects of this chemical in animals have produced evidence that cancer is associated with exposure to propylene oxide.
[63]
https://www.emergenresearch.com/industry-report/bio-based-propylene-oxide-market
[64]
Propylene oxide - NIOSH Pocket Guide to Chemical Hazards - CDC
Propylene oxide ; Freezing Point. -170°F ; Solubility. 41% ; Vapor Pressure. 445 mmHg ; Ionization Potential. 9.81 eV ; Specific Gravity. 0.83.
[65]
Effects of inhalation exposure to propylene oxide on respiratory tract ...
It was concluded that the developmental toxicity of fetal death was manifested at parentally toxic exposure levels above 500 ppm, a level which seriously ...
[66]
PROPYLENE OXIDE - CAMEO Chemicals - NOAA
A clear colorless volatile liquid with an ethereal odor. Flash point -35°F. Boiling point 95°F. Density 6.9 lb./gal. Flammable over a wide range of vapor-air ...Missing: structure bond angles strain
[67]
[PDF] Propylene Oxide - LyondellBasell
Propylene oxide is a stable material that will not decompose under normal conditions of temperature and pressure. 1.4. Reactivity Hazards. Propylene oxide may ...<|control11|><|separator|>
[68]
1990 ARCO explosion - Wikipedia
An explosion at the ARCO Chemical (ACC) Channelview, Texas petrochemical plant killed 17 people and injured five others on July 5, 1990.
[69]
Summary of Emissions Associated with Propylene Oxide
------- This report has been reviewed by the Emission Standards Division of the Office of Air Quality Planning and Standards, EPA, and approved for publication.Missing: 2007 | Show results with:2007
[70]
Photooxidation of the propylene-NOx-air system studied by long ...
Measurements of the products of atmospheric photochemical reactions in laboratory studies and in ambient air-relationships between ozone and other products.
[71]
Acetaldehyde, Dioxane, Ethylene Glycol Ethers, Propylene Oxide
Propylene oxide reacts only slowly with OH, with an atmospheric half-life of 3-10 days, to yield formaldehyde, acetaldehyde, and PAN. Uncertainties in the ...
[72]
Propylene oxide | 75-56-9 - ChemicalBook
Sep 25, 2025 · Chemical/Physical. The reported hydrolysis half-life for the conversion of propylene oxide to 1,2-propanediol in water at 25 °C and pH 7 is 14.6 ...
[73]
[PDF] PROPYLENE OXIDE
If released to water, propylene oxide will hydrolyze at estimated half- life rates of 11.6 days (at pH's 7-9) and 6.6 days (at pH. 5) at 25 deg C.) ...
[74]
Propylene Oxide | CH3CHCH2O | CID 6378 - PubChem - NIH
Propylene oxide appears as a clear colorless volatile liquid with an ethereal odor. Flash point -35 °F. Boiling point 95 °F. Density 6.9 lb./gal.
[75]
EPA faulted for slighting 'Cancer Alley' risks - POLITICO Pro
Oct 6, 2025 · A new study says the agency undercounted the "unacceptably high" public health hazards of toxic air pollutants in the Louisiana industrial ...
[76]
Federal Register notice: Propylene Oxide; Testing Requirements
Jan 16, 2025 · This final rule promulgated under section 4(a) of the Toxic Substances Control Act (TSCA) requires manufacturers and processors of propylene ...
[77]
Initial List of Hazardous Air Pollutants with Modifications | US EPA
Under the Clean Air Act, EPA is required to regulate emissions of hazardous air pollutants. ... Propylene oxide. 75558, 1,2-Propylenimine (2-Methyl aziridine).
[78]
(PP 5F9175) Petition to Establish Tolerances for Propylene oxide ...
(PP 5F9175) Petition to Establish Tolerances for Propylene oxide (PPO) on Various Dried Vegetables and Spices. Created by the Environmental Protection Agency.Missing: TSCA EU REACH
[79]
All you need to know about the new WGC emission limits - Desotec
Ethylene/ propylene oxide: down to 0.5 mg/m³; ... Adsorption on activated carbon is one of the Best Available Technologies (BAT) recommended by the EU regulation.Missing: Act | Show results with:Act
[80]
[PDF] Best Available Techniques (BAT) Reference Document for Common ...
Mar 10, 2022 · Propylene oxide is generally treated with at least one waste gas treatment technique. The typical emission levels of propylene oxide after ...
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https://www.desotec.com/en/knowledge-hub/article/all-you-need-to-know-about-the-new-wgc-emission-limits
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https://eippcb.jrc.ec.europa.eu/sites/default/files/2022-03/WGC_Final_Draft_09Mar2022-B-W-Watermark.pdf
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[PDF] LyondellBasell (LYB) Climate Transition Analysis - Planet Tracker
Sep 5, 2024 · LyondellBasell aims to achieve Carbon. Neutrality by 2050, targeting a 42% reduction in Scope 1 and 2 emissions and.
[84]
The propylene oxide problem - ICIS
Jul 6, 2017 · It is highly polluting in terms of waste calcium chloride. It also needs significant amounts of chlorine. □ Second generation: Newer plants ...<|separator|>
[85]
EPA Proposes Rollbacks to Chemical Regulation
Oct 28, 2025 · A proposed rule seeks to reverse recent changes to the procedures EPA uses to conduct risk assessments of toxic chemicals.Missing: propylene oxide legacy waste emissions
[86]
Discovery of the interstellar chiral molecule propylene oxide (CH 3 ...
Jun 17, 2016 · We present the astronomical detection of a chiral molecule, propylene oxide (CH 3 CHCH 2 O), in absorption toward the Galactic center.Missing: rotation | Show results with:rotation
[87]
On the formation of propylene oxide from propylene in space - HAL
Propylene oxide is the first chiral molecule observed in the interstellar medium, and studying the thermodynamics and kinetics of formation can suggest possible ...Missing: hypotheses | Show results with:hypotheses
[88]
A Combined Experimental and Theoretical Study on the Formation ...
Jun 18, 2018 · This work reveals via a combined experimental, computational, and astrochemical modeling study that racemic propylene oxide (c-C3H6O)—the first ...<|separator|>
[89]
The quest of chirality in the interstellar medium
Replacing the -CH3 group on rigid propylene oxide by -CN, -CCH, -NH2, -OH, or -HCO gives oxirane daughter molecules whose adsorption energies divide into two ...
[90]
Collisional excitation and non-LTE modelling of interstellar chiral ...
Dec 16, 2021 · The derived column density for propylene oxide is Ntot ~ 3e12 cm-2, corresponding to a fractional abundance relative to total hydrogen of ~ 2.5e ...
[91]
[PDF] Propylene Oxide - IARC Publications
The chloride ions in salt water accelerate the chemical degra- dation to a half-life of 4.1 days (Kahlich et al., 1993). 1.4 Regulations and guidelines.Missing: fate | Show results with:fate
[92]
[PDF] PROPYLENE OXIDE, A REGISTERED FUMIGANT, A PROVEN ...
Propylene oxide for food fumigation is regulated by CFR 40 Part 185.15. It establishes a residue “tolerance” of 300 ppm for nutmeats, cocoa powder and spices.