Reference product: acrolein [kg]
Location: RER - Europe
The process “acrolein, at plant, RER” is modelled for the production of acrolein from propene in Europe. Raw materials are modelled with a stoechiometric calculation. Emissions are estimated. Energy consumptions, infrastructure and transports are calculated with standard values.
The first process for acrolein production was commercialized by Degussa in 1942. It was based on the vapor-phase condensation of acetaldehyde and formaldehyde, catalyzed by sodium silicate on silica supports at 300 – 320 °C. This method prevailed until 1959, when Shell began producing acrolein by the vapor-phase oxidation of propene over a cuprous oxide catalyst. The catalyst performance in this process was very poor. In 1957 Standard Oil of Ohio (Sohio) discovered the bismuth molybdate catalyst system, which yielded a fairly good selectivity but still a low propene conversion.
The major byproducts of this reaction are acrylic acid and carbon oxides in addition to minor products such as acetaldehyde, acetic acid, formaldehyde, and polyacrolein.
Catalysts for the Oxidation of Propene
The discovery that propene could be oxidized rather selectively to acrolein over copper(I) oxide marked the beginning of the current process of catalytic alkene oxidation to aldehydes over metal oxide catalysts. However, low conversion of propene (20 %) per pass, significant recycle of unreacted propene, and low acrolein selectivities were reported for this catalyst. Modern catalysts are multicomponent metal oxide systems.
The optimization of the multicomponent catalyst system, to obtain a more selective and also active system with a high space time yield, is still a challenge.
However, acrolein yields depend not only on the chemical compositions of these catalysts, but also on their physical properties, such as shape, porosity, pore-size distribution, and specific surface area, as well as on the reaction conditions and construction of the reactor.
At present the maximum acrolein yield at high propene conversions (up to 98 %) using commercial catalysts is approximately 83 to 90 % with acrylic acid yields of 5 – 10 %. In commercial plants the catalysts are employed at reaction temperatures of 300 – 400 °C, contact times of 1.5 – 3.5 s, and propene concentrations of 5 – 10 vol % of the feed gas at inlet pressures of 150 – 250 kPa. The catalysts have lifetimes of up to ten years, after which they generally have to be replaced. The main reasons for a catalyst change are a reduced economy of the process that is mostly caused by a too low product yield or an increased pressure drop in the reactor.
The reactor is usually operated at 300 – 400 °C with a conversion rate of propene of up to 98 % and inlet pressures of 150 – 250 kPa. The reactor effluent is quenched at the exit to prevent subsequent reactions of acrolein. The reaction gas is then scrubbed with water or water/solvent mixtures in a first column (b) to remove acrylic acid, polymeric compounds, and traces of acetic acid. Byproduct acrylic acid can be recovered from the bottoms and purified; acrylic acid usually forms in 5 to 10 mol % yield based on propene.
The gas is then passed to an absorber (c) where an aqueous solution of acrolein is obtained by absorbing the gas in cold water. Part of the off-gas from the absorber can be used as inert gas for the reactor because it contains only noncondensable components, such as unreacted propene, carbon oxides, oxygen, and nitrogen. The rest is purged as waste gas after it passes through a combustion system.
The aqueous solution of acrolein is sent to a desorption column (d), where it is stripped to give crude acrolein; the bottom stream from this column is cooled and reused as an absorbent. The crude acrolein is distilled to remove low-boiling byproducts, such as acetaldehyde, and heavy ends; acrolein is then obtained as a 96 % pure product that contains only traces of acetaldhyde. Sometimes crude acrolein is used directly. To minimize polymerization, the whole system is stabilized by, e.g., hydroquinone.
Selectivity and yield are in the main focus in heterogeneous oxidation catalysis, because the cost of feed materials on the basis of oil escalates. New catalyst materials improve energy and raw materials efficiency and reduce CO2 formation and emission. Novel approaches to achieve this goal are using oxide nanocatalyst preparation to tune the nature of the active center, oxidant selection to avoid overoxidation, and catalyst arrangement to take advantage of the reaction mechanistic features. An alternative route to acrolein is indicated by numerous publications dealing with the conversion of propane over Mo-V-Te-X-O catalysts. Actually, new catalysts on the basis of Mo-P-Te-O/SiO2 and Mo-V-Te/SiO2 (and MCM 41) show the selective formation of acrolein from propane. However, thermodynamic considerations revealed the limitation of propane as feedstock for the one step synthesis of acrolein. The two stage process based on a first dehydrogenation step of propane to propene followed by a conventional unit for the oxidation of propene to acrolein (PDH-process). The first stage, the dehydrogenation of propane to propene is already commercial available: UOP (Oleflex-Process), ABB Lummus Global (Catofin-Process), Linde (Linde-Process), Snamprogetti/Yarsintez (Fluidized Bed Dehydrogenation-3-Process). In these technical processes, conversions of 30 to 60 % and selectivity to propene of 90 % are obtained. Important side reactions are cracking and hydrogenolysis of propane and propene. Coke deposits on the catalysts necessitate the regeneration of the catalyst. The total amount of propene that is produced by PDH is about 2 % of the total global amount. The oxidative dehydrogenation of propane (ODH process) is still in the development and has not yet led to a commercial process. However, the direct combination of propane dehydrogenation and selective oxidation of propene to acrolein has not yet been commercialized.
The MTP process (Methanol to Propene) that was developed by Lurgi uses methanol as feedstock for propene. The zeolite-based catalyst for the fixed bed process was developed by Südchemie AG. This technology increases the basis of the raw materials and is the latest example for the increasing relevance of methanol as basis for the chemical production of the future. It is planned to use methanol from a MegaMethanol plant that is sent to an adiabatic DME prereactor where, methanol is converted to DME and water. A methanol, water, DME stream is routed to the MTP® reactor. DME and methanol is converted by more than 99% with propylene as main product.
Acrolein (CH2CHCHO; CAS 107-02-8, propenal, acrylaldehyde), the simplest unsaturated aldehyde, is a colourless, volatile, toxic, and lacrimatory liquid with a powerful odour. Acrolein is a useful chemical intermediate used for the production of numerous chemical products. It is used commercially as a very effective broad-spectrum biocide in very low concentrations of approximately 10 ppm. For example, it is applied to control the growth of aquatic weeds in irrigation waterways or of algae and mollusks in recirculating water systems. Of particular importance is the use of acrolein as a biocide in oil-field brines; it increases the efficiency of oil-field water flooding and is useful in brine disposal operations. Furthermore, it is used in oil-field waters to scavenge malodorous hydrogen sulfide completely.
Frischknecht R., Jungbluth N., Althaus H.-J., Doka G., Dones R., Heck T., Hellweg S., Hischier R., Nemecek T., Rebitzer G. and Spielmann M. (2007) Overview and Methodology. Final report ecoinvent v2.0 No. 1. Swiss Centre for Life Cycle Inventories, Dübendorf, CH, retrieved from: www.ecoinvent.org.
Gendorf (2000) Umwelterklärung 2000, Werk Gendorf. Werk Gendorf, Burgkirchen as pdf-File under: http://www.gendorf.de/pdf/umwelterklaerung2000.pdf
Dietrich Arntz, Achim Fischer, Mathias Höpp, Sylvia Jacobi, Jörg Sauer, Takashi Ohara, Takahisa Sato, Noboru Shimizu, Helmut Schwind: Acrolein and Methacrolein. Published online: 2000. In: Ullmann's Encyclopedia of Industrial Chemistry, Seventh Edition, 2004 Electronic Release (ed. Fiedler E., Grossmann G., Kersebohm D., Weiss G. and Witte C.). 7 th Electronic Release Edition. Wiley InterScience, New York, Online-Version under: DOI: 10.1002/14356007.a01_149.pub2
[This dataset has been generated using the system model “Allocation at the point of substitution" (APOS). A system model describes how activity datasets are linked to form product systems. The APOS model subdivides multi-output activities by physical properties, economic, mass or other properties allocation. By-products of treatment processes are considered to be part of the waste-producing system and are allocated together. Markets in this model include all activities in proportion to their current production volume.
Version 3 of the ecoinvent database offers three system models to choose from. For more information, please visit: https://www.ecoinvent.org/database/system-models-in-ecoinvent-3/system-models-in-ecoinvent-3.html)]
reaction of propene with ammonia