Production of ethylene-derived chemicals of interest, in particular acrylic acid, in combination with generation of heated steam

Abstract

A process for the manufacture of acrylic acid in combination with generation of heated steam, the process comprising subjecting a feedstock comprising ethanol of a renewable source to dehydration to produce a stream of ethylene of a renewable source, the stream of ethylene of a renewable source to mutual olefin conversion to obtain propylene of a renewable source. Further, the propylene of renewable origin is subjected to an oxidation reaction to obtain acrylic acid. At least a portion of the heat generated by the oxidation reaction is removed, and at least a portion of the heat is transferred to the water stream to generate a heated steam stream. The process provides a reaction scheme that provides acrylic acid of a renewable source while minimizing both non-renewable fossil energy input and consumption of raw materials of a renewable source.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a process for the production of an ethylene-derived chemical of interest, in particular an oxidation product of an olefin selected from ethylene and C 3-4 -olefins, in combination with the generation of heating steam.

[0002] Ethylene is the cornerstone of the modern petrochemical industry. Important ethylene derivatives (at the ends of their respective chains) include (meth)acrylic acid, (meth)acrylates, isononanol, 2-ethylhexanol, and ethylene glycol. One of the problems faced in the manufacture of chemicals and intermediates from ethylene is that the starting materials are derived from fossil fuels such as natural gas or crude oil, which are non-renewable raw materials. Steam cracking using petroleum fractions and natural gas liquids as feedstocks is the dominant method for the large-scale production of ethylene globally.

[0003] The production of ethylene and ethylene derivative compounds would benefit from replacing at least a portion of the carbonaceous raw materials of fossil origin with renewable resources such as carbonaceous materials derived from biomass. Particular attention is paid to ethanol feedstocks produced from renewable resources. This ethanol from renewable sources (also known as "bioethanol" or "hydrous fuel alcohol") can be produced in large quantities from organic waste or biomass via fermentation. Different feedstocks for the production of ethanol can be sucrose-containing feedstocks such as sugarcane, starch materials such as corn, starch, wheat, cassava, lignocellulosic biomass such as switchgrass, and / or agricultural waste.

[0004] Ethanol from renewable sources can be converted into propylene from renewable sources through a series of steps that include the dehydration of ethanol to produce ethylene from renewable sources, and subjecting the ethylene stream from renewable sources to olefin metathesis to obtain propylene from renewable sources. Olefin metathesis then includes the dimerization of ethylene to obtain n-butene; and a metathesis reaction between n-butene and ethylene to obtain propylene.

[0005] However, ethanol dehydration is a highly endothermic reaction. Moreover, the olefin conversion step and the subsequent separation of the material streams by distillation or similar methods require an energy input. Therefore, when evaluating the overall environmental benefits, the non-renewable fossil energy inputs used in the production of the renewable source feedstock and its conversion must be considered. Although it is conceivable to burn a portion of the bioethanol to generate heat energy, the bioethanol used as fuel for energy generation is no longer available as a feedstock for chemical product manufacture.

[0006] If the initial energy input can be at least partially offset by green energy recovery downstream of the process, the economic viability of the ethanol dehydrogenation and olefin conversion steps can be improved. This would allow for a reduction in energy costs through the implementation of a heat integration design (i.e., the pairing of heat release streams with heat acceptance streams within the process scope).

[0007] Many important basic chemicals are manufactured by the oxidation of olefins on selective catalysts. For example, unsaturated aldehydes and carboxylic acids are obtained by the allylic oxidation of olefins, while epoxides are obtained by the epoxidation of olefins.

[0008] Due to its highly reactive double bond and acid functional group, acrylic acid is particularly suitable as a monomer for the preparation of polymers. Of the total amount of acrylic acid monomers produced, most are esterified before polymerization, for example to form acrylate adhesives, dispersions or coatings. Only a smaller portion of the acrylic acid monomers produced are polymerized directly, for example to form superabsorbent resins. Acrylic acid is industrially produced by the heterogeneous catalytic gas-phase oxidation of propylene with molecular oxygen on a solid catalyst via acrolein in two stages.

[0009] Ethylene oxide is used as a chemical intermediate, mainly for the production of ethylene glycol, but also for the production of ethoxylates, ethanolamines, solvents and ethylene glycol ethers. It is industrially produced by the direct oxidation of ethylene with oxygen or air.

[0010] US2008 / 0312485 discloses a process for the continuous production of propylene by dehydrating ethanol obtained from biomass to obtain ethylene and reacting the ethylene with n-butene in a metathesis reaction. The n-butene is prepared by the dimerization of ethylene obtained from ethanol derived from biomass.

[0011] WO 2009 / 098268 discloses a process for dehydrating an alcohol to prepare an olefin. The alcohol can be ethanol obtainable from carbohydrates. For this purpose, a stream comprising ethanol and an inert component is contacted with a catalyst to obtain ethylene. It is shown that the ethylene can be dimerized to butene and then isomerized to isobutene, dimerized to 1-butene, isomerized to 2-butene and further converted to propylene by metathesis with ethylene, or converted to ethylene oxide and ethylene glycol. Only the experimental details of the ethanol dehydration are provided. A similar process is disclosed in WO 2011 / 089235.

[0012] WO 2009 / 098269 discloses a process for converting ethanol, which can be obtained from carbohydrates, to propylene. The ethanol is dehydrated to ethylene, and the ethylene reacts with an olefin having four or more carbon atoms to obtain propylene. A similar process is disclosed in WO2009 / 098267.

[0013] The present invention seeks to propose a reaction scheme that provides oxidation products of olefins from renewable sources while minimizing both non-renewable fossil energy input and the consumption of raw materials from renewable sources. Summary of the Invention

[0014] The present invention relates to a method for manufacturing an ethylene-derived chemical of interest in combination with the generation of heated steam, the method comprising the following steps:

[0015] a) subjecting a feedstock comprising ethanol from a renewable source to dehydration to produce an ethylene stream from a renewable source;

[0016] b) optionally, subjecting the ethylene stream from a renewable source to olefin metathesis to obtain a C 3-4 - olefin from a renewable source selected from propylene, 1-butene, and isobutene; the olefin metathesis comprising one of (i) and, if desired, (ii) and (iii):

[0017] (i) ethylene dimerization to obtain 1-butene;

[0018] (ii) a metathesis reaction between the 1-butene obtained according to (i) and ethylene to obtain propylene;

[0019] (iii) isomerizing the 1-butene obtained according to (i) to obtain isobutene; and

[0020] c) subjecting the ethylene from a renewable source or the C 3-4 - olefin from a renewable source to a chemical conversion or a series of chemical conversions to obtain the chemical of interest;

[0021] wherein at least one of these chemical conversions is an exothermic chemical reaction;

[0022] removing at least a portion of the heat generated by the exothermic chemical reaction and transferring at least a portion of the heat to a water stream to produce a heated steam stream.

[0023] In particular, the present invention relates to a method for manufacturing acrylic acid in combination with the generation of heated steam, the method comprising the following steps:

[0024] a) subjecting a feedstock comprising ethanol from a renewable source to dehydration to produce an ethylene stream from a renewable source;

[0025] b) subjecting the ethylene stream from a renewable source to olefin metathesis to obtain propylene from a renewable source; the olefin metathesis comprising (i) and (ii):

[0026] (i) ethylene dimerization to obtain 1-butene;

[0027] (ii) a metathesis reaction between the 1-butene obtained according to (i) and ethylene to obtain propylene; and

[0028] c) subjecting the propylene from a renewable source to an oxidation reaction to obtain acrylic acid; and

[0029] Remove at least a portion of the heat generated by the oxidation reaction and transfer at least a portion of the heat to a water stream to produce a heated steam stream.

[0030] Although it is beneficial to use only ethylene from renewable sources or C 3-4 -olefins from renewable sources in the chemical conversion or series of chemical conversions in step c), in the examples, ethylene from renewable sources or C 3-4 -olefins from renewable sources are blended with fossil-derived olefins, such as petroleum-derived olefins, having the same chemical structure. This can be an option for plant-wide utilization, periods of fluctuating raw material supply, and / or during the transition period to using only ethylene from renewable sources or C 3-4 -olefins from renewable sources.

[0031] According to the present invention, at least a portion of the thermal energy generated by an exothermic chemical reaction is recovered by generating a heated steam stream. Conveniently, the heated steam stream is used to provide heat to one or more heat-accepting processes. Modern industrial chemical production sites are integrated with multiple processes and equipment to produce various chemical products. A "heat-accepting process" can be any process in an industrial chemical production site that requires an input of thermal energy (typically provided by heated steam). A "heat-accepting process" can be, for example, any one or all of steps a), b)-(i), b)-(ii), and b)-(iii), but is not limited thereto. A "distributed steam network" is used for heat transfer between different processes within the site and is thus used for heat integration and efficient use. Thermal energy can generate steam through the evaporation of water, preferably in the form of steam condensate. The steam is fed into the steam network. The reaction heat can be additionally utilized to raise the steam to a high pressure level of 4 bar gauge or higher, as typically provided in steam pipelines in industrial plants. The steam can be used in equipment such as heat exchangers, steam turbines, reboilers, etc.

[0032] In an example, the heated steam stream is used to provide at least a portion of the heat consumed in at least one of steps a) and b), more specifically in at least one of steps a), b)-(i), b)-(ii), and b)-(iii). Thereby, the economic feasibility of the ethanol dehydrogenation and olefin conversion steps can be improved because less fossil energy is required for steam generation.

[0033] Unfortunately, not every type of waste heat can be used economically. Heat recovered at too low a temperature for convenient use in the plant must be treated with cooling water, thus imposing an energy penalty on the overall process. Therefore, highly exothermic chemical reactions are preferred candidates for heat recovery by generating heated steam. A reaction is considered exothermic if the standard reaction enthalpy of the reaction is negative. Preferably, the standard reaction enthalpy of the exothermic chemical reaction Less than -400 kJ / mol, more preferably in the range of -1500 to -450 kJ / mol, even more preferably in the range of -1400 to -500 kJ / mol.

[0034] Standard reaction enthalpy With the standard formation enthalpies of one or more reactants and one or more reaction products Are related by the following equation:

[0035]

[0036] "One or more reactants" means one or more chemical substances that undergo the corresponding exothermic chemical reaction.

[0037] "Reaction product" means the reaction product directly obtained from the corresponding exothermic chemical reaction. It can be the chemical of interest or the corresponding intermediate along the chemical path to the chemical of interest.

[0038] The standard formation enthalpy is the change in enthalpy during the formation of 1 mole of a substance (reactant or reaction product) from its constituent elements, where all substances are in their standard states.

[0039] All enthalpy values refer to standard conditions (25 °C and 1 bar).

[0040] In a preferred embodiment, the exothermic chemical reaction is an oxidation reaction. In the oxidation reaction, the substrate is oxidized by an oxidant, preferably molecular oxygen or air, to obtain the oxidation product of the substrate. "Substrate" can be ethylene from renewable sources or C from renewable sources 3-4- olefins (optionally blended with fossil - derived olefins having the same chemical structure) or their conversion products obtained by chemical conversion or a series of chemical conversions upstream of the oxidation reaction. The chemical conversions involved in the oxidation reaction have a selectivity of less than 100%. The yield loss itself is manifested in the over - oxidation of the substrate to form carbon oxides, especially carbon dioxide. The over - oxidation of the substrate to form carbon dioxide contributes to the exothermic nature of the oxidation reaction. A substantial proportion of the heat released is generated by the complete oxidation of the olefinic substrate, where the release of CO2 is caused by the high reaction enthalpy attributed to complete oxidation. If olefins from renewable sources are used, this complete oxidation to CO2 can be considered as the combustion of ethanol from renewable sources transferred to the oxidation reaction step. The key feature of this preferred embodiment is the specific combination of the production of olefins from renewable sources and the oxidation reaction of the corresponding olefins from renewable sources. The resulting steam can be considered "green steam" because the heat used for its generation can be attributed to the combustion of ethanol from renewable sources and thus does not require fossil resources. Of course, a certain amount of ethanol from renewable sources can also be directly burned (i.e., used as a biofuel) to generate the required heat. However, once burned, the ethanol from renewable sources can no longer be used as a starting material for chemical synthesis. This amount of ethanol from renewable sources can be saved through the specific combination according to this preferred embodiment. In other words, burning a part of the ethanol from renewable sources to generate heat is transferred to a later production step, namely the oxidation of the corresponding olefins from renewable sources, as part of the inevitable yield loss there. Thus, this embodiment combines the use of ethanol from renewable sources as a starting material for chemical synthesis and at the same time as a biofuel.

[0041] Typically, in an oxidation reaction where heat recovery is easily achieved by generating heating steam, 1 to 10 mol.-%, preferably 2 to 8 mol.-% of the substrate is over - oxidized to carbon dioxide.

[0042] By completely or partially replacing fossil ethylene and C 3-4 - olefins with their renewable - source counterparts, fossil - based carbon dioxide emissions can be reduced because the emissions caused by yield loss are at least partially based on green carbon. Thus, the resulting carbon dioxide emissions do not contribute to the greenhouse emissions at the production site. For example, in the production of acrylic acid or ethylene oxide (as further described below), carbon dioxide is formed due to the complete oxidation of propylene or ethylene, respectively. Thus, the use of propylene or ethylene from renewable sources according to the present invention prevents the formation of fossil - based carbon dioxide emissions caused by such production.

[0043] If olefins from renewable sources are used, the CO2 formed is of biogenic origin and does not contribute to the greenhouse effect. Thus, the heat released therefrom does not generate any CO2 emissions.

[0044] In a preferred embodiment of the method according to the invention, based on the total amount of CO2 released in the oxidation reaction, i.e. including both biogenic CO2 and fossil CO2, the amount of biogenic CO2 released in the oxidation reaction is in the range of 50 to 100 wt.-%, preferably 80 to 100 wt.-%.

[0045] Based on carbon isotope fingerprinting and / or 14 C(fM), biogenic CO2 can be distinguished from fossil CO2. There are three naturally occurring carbon isotopes: 12 C, 13 C and 14 C. These isotopes are present in the total carbon on earth in fractions of 0.989, 0.011 and 10-12, respectively. The isotopes 12 C and 13 C are stable, while 14 C naturally decays to 14 N, with a half-life of 5730 years. The isotope 14 C originates in the atmosphere, mainly due to neutron bombardment of 14 N ultimately caused by cosmic radiation. Due to its relatively short half-life (in geological terms), 14 C is present in fossil carbon at very low levels.

[0046] Alternatively, the ratio of fossil CO2 to biogenic CO2 can of course be evaluated based on the input of biogenic ethylene or C 3-4 -olefins and fossil ethylene or C 3-4 -olefins to the oxidation reaction.

[0047] Typically, the oxidation reaction is selected from allylic oxidation reactions and epoxidation reactions. As used herein, the term "allylic oxidation" means the oxidation of an allylic compound by replacing one or more allylic hydrogens with an oxygen or oxygen-containing group. Similarly, the term "epoxidation" means the oxidation of an olefin by adding an oxygen atom to a carbon-carbon double bond to form an epoxide ring:

[0048] Preferably, the allylic oxidation reaction is selected from the oxidation of propylene to obtain acrolein and / or acrylic acid; and the oxidation of isobutene to obtain methacrolein and / or methacrylic acid.

[0049] Preferably, the epoxidation reaction is the epoxidation of ethylene to obtain ethylene oxide.

[0050] Typically, the oxidation reaction is a heterogeneous catalytic gas-phase oxidation with molecular oxygen. The oxidizing agent can be air, oxygen or other molecular oxygen-containing gases. Air has the advantage of lower cost, but oxygen allows for a higher throughput per unit reactor volume.

[0051] The method of the present invention is preferably a continuous method. This does not exclude the presence of buffer volumes between subsequent reaction steps in the reaction route.

[0052] The expressions "renewable" or "renewable source" with respect to chemical compounds are used synonymously and mean chemical compounds containing a certain amount of renewable carbon, i.e., having a reduced carbon content of fossil origin or no carbon content of fossil origin. Renewable carbon relates to all carbon sources that avoid or replace the use of any additional fossil carbon from the lithosphere. Renewable carbon can come from the biosphere, the atmosphere or the technosphere - but not from the lithosphere. Thus, the expressions "renewable" or "renewable source" particularly include biomass-derived chemical compounds. It also includes compounds derived from waste (such as polymer residues) or from waste streams from chemical production processes.

[0053] Bioethanol is a preferred form of ethanol of renewable source, although the scope of the present invention is not limited to the use of bioethanol.

[0054] In the present invention, bioethanol refers to ethanol obtained from biomass feedstocks such as plants or non-crop feedstocks containing a carbon source that can be converted into ethanol, for example, by microbial metabolism. Typical examples of carbon sources are starch, sugars such as pentoses or hexoses, such as glucose, fructose, sucrose, xylose, arabinose, or degradation products of plants, hydrolysis products of cellulose or the juice of sugarcane, sugar beet, etc. containing a large amount of the above components.

[0055] Biomass feedstocks can be derived from several sources. Bioethanol production can be based on food crop feedstocks such as corn and sugarcane, sugarcane bagasse, cassava (first-generation biofeedstocks).

[0056] Another source of biomass feedstocks is lignocellulosic materials from agricultural crops (second-generation biofeedstocks). Potential feedstocks include agricultural residue by-products such as rice, straw (such as wheat, oat and barley straw), rice husks and corn stover. Biomass feedstocks can also be waste from the forest products industry (wood waste) and sawdust or waste specifically produced as ethanol crops. Switchgrass and elephant grass can be used as dedicated crops for conversion to ethanol.

[0057] First-generation bioethanol is produced in four basic steps:

[0058] (1) Enzymatic saccharification or hydrolysis of starch into sugars;

[0059] (2) Microbial fermentation of sugars;

[0060] (3) Purification by distillation to obtain hydrous ethanol; and

[0061] (4) Dehydration (water removal) to produce anhydrous ethanol.

[0062] The second-generation feedstock is considered a renewable and sustainable carbon source. Pretreatment of this feedstock is an essential prerequisite before subjecting it to enzymatic hydrolysis, fermentation, distillation, and dehydration. Pretreatment involves grinding and exposure to acids and heat to reduce the size of the plant fibers and hydrolyze a portion of the material to produce fermentable sugars. Saccharification utilizes enzymes to hydrolyze another portion into sugars. Finally, various sugars (pentoses and hexoses) are converted into ethanol by fermentation of bioengineered microorganisms. The production of bioethanol is well-known and carried out on an industrial scale.

[0063] Ethanol from renewable sources can also be obtained from carbonaceous waste materials such as waste from the chemical industry, garbage, and sewage sludge. The production of ethanol from waste can be accomplished by gasification into syngas and its catalytic conversion into ethanol, see for example Recent Advances in Thermo-Chemical Conversion of Biomass, 2015, pp. 213 - 250, https: / / doi.org / 10.1016 / B978-0-444-63289-0.00008-9 and Nat Commun 11, 827 (2020), https: / / doi.org / 10.1038 / s41467-020-14672-8.

[0064] Dehydration of ethanol from renewable sources

[0065] As a first step, the present invention relates to the dehydration of ethanol from renewable sources. The production of ethylene by catalytic dehydration of ethanol is a well-known method. This reaction is typically carried out at 300 °C to 400 °C and moderate pressure in the presence of a catalyst. Catalysis is reviewed in Ind&Eng Chem Research, 52, 28, 9505 - 9514 (2013), Materials 6, 101 - 115 (2013) and ACS Omega, 2, 4287 - 4296 (2017). Examples of catalysts are activated alumina or silica, phosphoric acid impregnated on coke, heteropolyacids (HPA salts), silica-alumina, molecular sieves such as zeolites of the ZSM-5 type or SAPO-11 type, other zeolites or modified zeolites of various molecular structures, with zeolites and HPA salts being preferred.

[0066] The dehydration of ethanol is described, for example, in WO 2009 / 098268, WO 2010 / 066830, WO 2009 / 070858 and the prior art discussed therein, WO 2011 / 085223 and the prior art discussed therein, US 4,234,752, US 4,396,789, US 4,529,827 and WO 2004 / 078336.

[0067] The ethanol dehydration reaction is typically carried out in the gas phase in contact with a heterogeneous catalyst bed using a fixed bed or fluidized bed reactor. For a fixed bed reactor, the operation can be isothermal (with an external heating system) or adiabatic (in the presence of a heat carrier fluid). The feedstock is vaporized and heated to the desired reaction temperature; as the reaction proceeds in the reactor, the temperature drops. Multiple reactor beds are typically used in series to maintain the temperature drop in each bed within a controllable range. The cooled effluent from each bed is further heated to bring it to the desired inlet temperature of the subsequent bed. In addition, a portion of the water is recycled together with fresh and unreacted ethanol. The presence of water helps to moderate the temperature drop in each bed.

[0068] Prior to dehydration, an ethanol feedstock from a renewable source can be sent to a pretreatment section to remove mineral contaminants which would otherwise be detrimental to the downstream catalytic reaction. The pretreatment can involve contacting the ethanol feedstock from a renewable source with cationic and / or anionic exchange resins. After a period of operation, the resins can be regenerated by passing a regenerant solution through one or more resin beds to restore their ion exchange capacity. Two sets of beds are preferably operated in parallel to maintain continuous operation. One set of resin beds is appropriately regenerated while the other set of resin beds is used for pretreatment.

[0069] In an isothermal design, the catalyst is placed inside the tubes of a shell-and-tube fixed bed reactor arranged vertically and surrounded by a shell (shell-and-tube design). A heat transfer medium (such as molten salt or oil) is circulated inside the shell to provide the required heat. Baffles can be provided on the shell side to promote heat transfer. The cooled heating medium is heated externally and recycled. Compared to an adiabatic reactor, the temperature drop on the process side can be reduced. Better control of the temperature results in an increased selectivity for ethylene formation and a reduced amount of undesired by-products. The temperature is maintained at a substantially constant level within the range of 300 °C to 350 °C. The ethanol conversion is between 98% and 99%, and the selectivity for ethylene is between 94 and 97 mol%. Due to the rate of coke deposition, the catalyst must be regenerated frequently. Depending on the type of catalyst used, the cycle life is between 3 weeks and 4 months, followed by regeneration, for example, for 3 days.

[0070] In the adiabatic design, the endothermic heat of the reaction is supplied by a preheated inert diluent such as steam. Typically, three fixed-bed reactors can be used, where an intermediate furnace is used to reheat the ethanol / steam mixed feed stream to each reactor. Feeding ethanol together with steam results in less coke formation, longer catalyst activity, and higher yields.

[0071] Another approach is the fluidized-bed approach. The fluidized-bed system provides excellent temperature control in the reactor, thus minimizing by-product formation. The heat distribution rate of the fluidized-bed operation approaches isothermal conditions. The endothermic heat of the reaction is supplied by the hot recycled silica-alumina catalyst returned from the catalyst regenerator. Therefore, no external heating of the reactor is required.

[0072] After dehydration, the reaction mixture is subjected to a separation step. A typical separation scheme includes rapidly cooling the reaction gas, for example, in a water quench tower, which separates most of the by-product water and unreacted ethanol from ethylene and other light components, which leave from the top of the quench tower, for example. In one type of separation scheme, the water-washed ethylene stream is immediately subjected to an alkali wash (e.g., in a column) to remove trace amounts of CO2. The gaseous stream can enter the compressor directly or first pass through a buffer gas holder and then enter the gas compressor. After compression, the gas is cooled by refrigeration and then passed through an adsorber with, for example, activated carbon to remove trace amounts of heavy components (e.g., C4) if they are present. Before the ethylene product leaves the plant, the adsorber is followed by a desiccant drying and dust filtration step. This separation scheme produces ethylene with a purity of 99%+. If desired, the ethylene is further purified by alkali washing and desiccant drying and fractionated in a cryogenic column to obtain the final product.

[0073] Several commercial processes developed jointly by Braskem, Koch, British Petroleum (BP), and Axens, together with Total and IFPEN (French Institute of Petroleum for Renewable Energies), are currently in operation. These processes differ, for example, in their process conditions, catalysts, and heat integration schemes employed. The process of BP (now Technip) is called Hummingbird. In this process, a heteropoly acid is used as the catalyst, and the reactor operates at 160 °C to 270 °C and 1 to 45 bar. Unreacted ethanol is recycled to the reactor. The process developed by Axens is called Atol. Two fixed-bed adiabatic reactors operating at 400 °C to 500 °C are used. The process of Koch operates with four adiabatic tubular reactors. In this process, the Syndol catalyst (main components Al2O3-MgO / SiO2), developed by American Halcon Scientific Design, Inc. in the 1980s, is employed. In the process of Braskem, the adiabatic reactor feed is largely diluted with steam. In this process, the reactor operates at 180 °C to 600 °C, preferably 300 °C to 500 °C, and at 1.9 to 19.6 bar. Alumina or silica-alumina catalysts are used. The process of Braskem is described in more detail in US 4,232,179. Process control according to the process of Braskem is particularly preferred.

[0074] Dimerization of ethylene

[0075] In one aspect, the method of the present invention relates to dimerization of ethylene according to steps b)-(i) above to obtain n-butene. Any known method can be used for dimerization of ethylene to produce n-butene. A review of dimerization and oligomerization chemistry and technology is given in Catalysis Today, Volume 14 (Issue 1), April 10, 1992.

[0076] Suitably, steps b)-(i) comprise:

[0077] - contacting the ethylene stream from the renewable source with a dimerization catalyst in a dimerization zone;

[0078] - operating the dimerization zone under conditions effective to produce an effluent stream consisting essentially of n-butene, a stream consisting essentially of heavier olefins, and optionally an unreacted ethylene stream; and

[0079] - fractionating the effluent stream to recover a stream consisting essentially of n-butene, a stream consisting essentially of heavier olefins, and optionally an ethylene stream.

[0080] The dimerization catalyst can be homogeneous or heterogeneous. Typical dimerization catalysts are titanium or nickel compounds activated with an alkylaluminum compound. Generally, the Ti(IV) valence is stabilized by choosing appropriate ligands, alkylaluminum compounds, solvent polarity, and Al / Ti ratio. Nickel compounds that can catalyze the selective production of butene are typically cationic nickel salts stabilized with phosphines and activated with an alkylaluminum compound.

[0081] In one embodiment, the oligomerization of ethylene is carried out in a liquid phase containing a nickel compound and an aluminum compound in the presence of a catalytic system. Such catalytic systems are described in documents FR 2 443 877 and FR 2794 038. Dimersol E TM The method is based on this technology and leads to the industrial production of olefins.

[0082] Thus, in one embodiment, the oligomerization of ethylene is carried out in the presence of a catalytic system comprising:

[0083] i) at least one divalent nickel compound,

[0084] ii) at least one hydrocarbyl dihaloaluminum having the formula AlRX2, where R is a hydrocarbyl group containing 1 to 12 carbon atoms, such as an alkyl, aryl, aralkyl, alkaryl, or cycloalkyl group, and X is a chlorine or bromine atom, and

[0085] iii) optionally a Bronsted organic acid.

[0086] As the divalent nickel compound, nickel carboxylate having the general formula (R 1 COO)2Ni is preferably used, where R 1 is an optionally substituted hydrocarbyl group containing up to 20 carbon atoms, such as an alkyl, cycloalkyl, alkenyl, aryl, aralkyl, or alkaryl group, preferably a hydrocarbyl group having 5 to 20 carbon atoms, preferably 6 to 18 carbon atoms. Suitable divalent nickel compounds include: chlorides, bromides, carboxylates such as octanoate, 2-ethylhexanoate, decanoate, oleate, salicylate, hydroxydecanoate, stearate, phenolates, naphthenates, and acetylacetonates. Nickel 2-ethylhexanoate is preferably used.

[0087] The hydrocarbyl dihaloaluminum compound corresponds to the formula AlRX2, where R is a hydrocarbyl group containing 1 to 12 carbon atoms, such as an alkyl, aryl, aralkyl, alkaryl, or cycloalkyl group, and X is a chlorine or bromine atom. As examples of such compounds, sesquiethylaluminum chloride, dichloroethylaluminum, dichloroisobutylaluminum, chlorodiethylaluminum, or mixtures thereof can be mentioned.

[0088] According to a preferred method, a Bronsted organic acid is used. The Bronsted acid compound corresponds to the formula HY, where Y is an organic anion, such as a carboxyl, sulfonic, or phenolic group. Having the formula R2 Halocarboxylic acids of the formula COOH (wherein R 2 is a haloalkyl) are preferred, especially those containing at least one α-halogen atom of the group —COOH and having a total of 2 to 10 carbon atoms. Preferably, haloacetic acids of the formula CX p H 3-p —COOH are used, where X is fluorine, chlorine, bromine or iodine and p is an integer from 1 to 3. By way of example, trifluoroacetic acid, difluoroacetic acid, fluoroacetic acid, trichloroacetic acid, dichloroacetic acid and chloroacetic acid may be mentioned. Arylsulphonic acids, alkylsulphonic acids and fluoroalkylsulphonic acids, as well as picric acid and nitroacetic acid may also be used. Trifluoroacetic acid is preferably used.

[0089] The three components of the catalytic formulation can be mixed in any order. However, it is preferred to first mix the nickel compound with the Bronsted organic acid and then subsequently introduce the aluminium compound. The molar ratio of the hydrocarbyl aluminium dihalide to the nickel compound, expressed as the Al / Ni ratio, is from 2 / 1 to 50 / 1, and preferably from 2 / 1 to 20 / 1. The molar ratio of the Bronsted acid to the nickel compound is from 0.25 / 1 to 10 / 1, and preferably from 0.25 / 1 to 5 / 1.

[0090] According to a preferred method, the hydrocarbyl aluminium dihalide can be rich in aluminium trihalide, the mixture of the two compounds corresponding to the formula AlR n X 3-n , where R is a hydrocarbyl group containing from 1 to 12 carbon atoms, such as an alkyl, aryl, aralkyl, alkaryl or cycloalkyl group, X is a chlorine or bromine atom and n is a number between 0 and 1. Suitable mixtures include: dichloroethylaluminium rich in aluminium chloride, the mixture having the formula AlEt 0.9 Cl 2.1 ; dichloroisobutylaluminium rich in aluminium chloride, the mixture having the formula AliBu 0.9 Cl 2.1 ; and dibromoethylaluminium rich in aluminium bromide, the mixture having the formula AlEt 0.9 Br 2.1 .

[0091] The reaction for the oligomerization of ethylene can be carried out under pressure conditions at a temperature of from -20 °C to 80 °C, preferably from 40 °C to 60 °C, such that at least most of the reagents remain in the liquid phase or the condensed phase. The pressure is generally between 0.5 and 5 MPa, preferably between 0.5 MPa and 3.5 MPa. The contact time is generally between 0.5 and 20 hours, preferably between 1 and 15 hours.

[0092] The oligomerization stage can be carried out in a reactor having one or more reaction stages in series, in which the ethylene feedstock and / or preferably a pre-conditioned catalytic composition are continuously introduced in the first stage or in the first stage and any other of these stages. At the outlet of the reactor, the catalyst can be deactivated, for example, by injecting ammonia and / or an aqueous soda solution and / or an aqueous sulfuric acid solution. Then, by a separation stage, for example, by distillation or by means of a washing cycle with caustic soda and / or water, the unconverted olefins and alkanes optionally present in the feedstock are separated from the oligomers.

[0093] The conversion per pass is generally 85% to 98%. The selectivity of the formed n-butenes is generally between 50% and 80%. The n-butenes consist of butene-2 (cis- and trans-) and butene-1.

[0094] The effluent generally contains less than 0.2% by weight of isobutene, or even less than 0.1% by weight of isobutene.

[0095] Separation of the n-butene-rich stream

[0096] The effluent obtained by ethylene dimerization is subjected to a separation stage in such a way as to obtain a fraction rich in n-butenes.

[0097] The separation can be carried out by evaporation, distillation, extractive distillation, by solvent extraction or by a combination of these techniques. These methods are known to those skilled in the art. Preferably, the separation of the effluent obtained by the oligomerization of ethylene is carried out by distillation.

[0098] Preferably, the oligomerization effluent is sent to a distillation column system comprising one or more columns which, on the one hand, make it possible to separate the n-butenes from the ethylene (which can be returned to the oligomerization reactor) and the heavier olefins having 5 and more carbon atoms.

[0099] The higher olefins can be subjected to hydrogenation in order to obtain naphtha from renewable sources. "Naphtha from renewable sources" shall mean naphtha produced from renewable sources. It is a hydrocarbon composition mainly consisting of paraffins. The molecular weight of this naphtha from renewable sources can range from hydrocarbons having 5 to 8 carbon atoms. The naphtha from renewable sources can be used as a feedstock in steam cracking to produce light olefins, dienes and aromatic compounds from renewable sources.

[0100] Thus, in the examples, step b)-(i) comprises:

[0101] - bringing the ethylene stream from renewable sources into contact with a dimerization catalyst in a dimerization zone;

[0102] - operating the dimerization zone under conditions effective to produce an effluent consisting essentially of n-butenes, a stream consisting essentially of heavier olefins, and optionally an unreacted ethylene stream;

[0103] - fractionating the effluent to recover a stream consisting essentially of n-butenes, a stream consisting essentially of heavier olefins, and optionally an ethylene stream; and

[0104] - subjecting the stream consisting essentially of heavier olefins to hydrogenation to obtain naphtha from renewable sources.

[0105] Metathesis of ethylene and n-butene

[0106] Ethylene can undergo metathesis with n-butene to produce propylene. In one aspect of the invention, step b)-(ii) includes a metathesis reaction between the n-butene obtained according to step (i) and ethylene to obtain propylene. The n-butene obtained during ethylene dimerization (i) is a mixed stream containing 1-butene and 2-butene. Basically only 2-butene reacts in the metathesis reaction, while 1-butene is substantially inert.

[0107] In one embodiment, 1-butene is removed from the mixed stream of 1-butene and 2-butene and directed elsewhere in the plant for use. Thus, in one embodiment, step b)-(ii) includes removing 1-butene from the mixed stream to obtain a 2-butene-rich stream and subjecting the 2-butene-rich stream to a metathesis reaction. The 2-butene-rich stream may contain at least 90 wt.-% 2-butene based on the total amount of n-butenes.

[0108] Alternatively, 1-butene can be converted to 2-butene by double bond isomerization. Double bond isomerization is an equilibrium-limited reaction. Therefore, it is advantageous to subject the mixed stream of n-butenes to metathesis so that 2-butene reacts with ethylene before the double bond isomerization of 1-butene. Thus, in one embodiment, the n-butene is a mixed stream containing 1-butene and 2-butene, and b)-(ii) includes

[0109] b)-(iia) subjecting the mixed stream to the metathesis reaction to obtain propylene and unreacted 1-butene;

[0110] b)-(iib) subjecting the unreacted 1-butene to double bond isomerization to obtain 2-butene; and

[0111] b)-(iic) recycling the 2-butene obtained in step b)-(iib) to step b)-(iia).

[0112] In another embodiment, 1-butene can be converted to 2-butene while the metathesis reaction is taking place. For this purpose, the metathesis catalyst and the isomerization catalyst can be physically mixed or provided as separate layers to allow the two reactions to occur simultaneously. Thus, in one embodiment, the n-butene is a mixed stream comprising 1-butene and 2-butene, and step b)-(ii) comprises passing the mixed stream through a metathesis / isomerization zone comprising both the metathesis catalyst and the isomerization catalyst. Since 2-butene is consumed by the metathesis reaction on the metathesis catalyst, the 2-butene is replenished by isomerizing 1-butene to 2-butene on the isomerization catalyst.

[0113] The reaction is carried out in the presence of a metal-based metathesis catalyst selected from tungsten, molybdenum, rhenium, niobium, tantalum, vanadium, ruthenium, rhodium, iridium, osmium, and nickel, among others. Tungsten, molybdenum, and rhenium are preferred and tungsten is particularly preferred. Typically, the tungsten catalyst is supported on silica, and molybdenum and rhenium are supported on an alumina-based support. A particularly preferred metathesis catalyst is a WO3-based catalyst, such as silica-supported WO3 in particulate form.

[0114] Suitable isomerization catalysts include magnesium-based catalysts, such as MgO-based catalysts, e.g., tableted MgO.

[0115] The metathesis is carried out under conditions effective to produce an effluent comprising propylene, unreacted ethylene, and optionally 1-butene.

[0116] The unreacted ethylene and / or unreacted n-butene can be recycled and combined with fresh ethylene and n-butene to provide the metathesis feedstock.

[0117] The reaction can be carried out at 340 °C - 375 °C, 25 - 40 bar, a weight hourly space velocity (WHSV) of 7.5 - 30 h -1 -1, and an ethylene to 2-butene molar ratio of 3:1 to 10:1.

[0118] The reactor effluent can be sent to a deethenizer to remove C2 and lighter materials. The bottom residue from the deethenizer is sent to a depropanizer. High purity, polymer grade propylene (>99.9 mol% purity) is recovered from the overhead distillate of the depropanizer. The lighter materials from the deethenizer and the heavier C 4+ materials from the depropanizer are partially recycled to the reactor. A purge stream is provided for the lighter and heavier materials to prevent the accumulation of inert substances.

[0119] It should be noted that propane is not produced during the metathesis reaction. Thus, polymer grade propylene can be produced by this method without the need for an expensive propylene-propane superfractionator.

[0120] Commercial processes for the production of polymer grade propylene by metathesis of ethylene and butene feedstocks are available from CB&I / Lummus (trade name OCT TM ) and LyondellBasell.

[0121] Propylene is oxidized to produce acrolein or acrylic acid

[0122] In one aspect of the invention, the oxidation reaction is an oxidation reaction in which propylene produces an oxidation product selected from acrolein and acrylic acid.

[0123] It is well known that acrylic acid can be produced in two stages via acrolein by the heterogeneous catalytic gas-phase oxidation of propylene with molecular oxygen at a temperature between 200 °C and 400 °C over a solid catalyst (see, for example, DE-A 19 624 31, DE-A 29 43 707, DE-C 1 205 502, EP-A 257 565, EP-A 253 409, DE-B 22 51 364, EPA 117 146, GB-C 1 450 986 and EP-A 293 224). The catalysts used are oxidation multicomponent catalysts based on oxides of elements such as molybdenum, chromium, vanadium or tellurium. The five most commonly used catalyst systems for acrolein production are cuprous oxide, uranium antimonide oxide, tin antimonide oxide, bismuth molybdate oxide and oxides based on multicomponent bismuth molybdate. The most effective catalysts for the partial oxidation of propylene to acrolein consist of multicomponent metal oxide systems. In almost every multicomponent catalyst system, bismuth molybdate acts as the main component. The following components are most commonly used as catalyst additives in catalysts based on bismuth molybdate oxide: iron, cobalt, nickel, tungsten, potassium and phosphorus. Typical catalyst supports are inert porous solids such as SiO2, Al2O3, MgO, TiO2, ZrO2, aluminosilicates, zeolites, activated carbon and ceramics.

[0124] The oxidation of propylene to acrylic acid can be carried out in one or two stages. Catalysts for heterogeneous catalytic reactions are usually multi-metal oxide materials, which usually contain heavy metal molybdates as the main component and compounds of various elements as promoters. The oxidation of propylene occurs in the first step to obtain acrolein and in the second step to obtain acrylic acid. Since these two oxidation steps may be different in their kinetics, uniform process conditions and a single catalyst usually do not result in optimal selectivity. Recently, therefore, a two-stage method with an optimal adaptation of catalyst and process variables has preferably been developed. Generally, in the first stage, propylene undergoes an exothermic reaction in the presence of molecular oxygen in a fixed-bed tubular reactor and is oxidized to acrolein. The reaction product is directly transferred to the second reactor and further oxidized to acrylic acid. The reaction gas obtained in the second stage can be condensed and acrylic acid can be separated from it by extraction and / or distillation.

[0125] The oxidation of propylene to acrolein and / or acrylic acid is highly exothermic. Therefore, the tubes of a fixed-bed tubular reactor filled with a heterogeneous catalyst are surrounded by a cooling medium (usually a salt melt, such as a eutectic mixture of KNO3 and NaNO2). The heat of reaction is released to the salt bath through the walls of the catalyst-filled tubes.

[0126] Particularly preferred multi-metal oxide materials have the formula I or II

[0127] [X 1 a X 2 b O x p [X 3 c X 4 d X 5 e X 6 f X 7 g X 2 h O y q (I)

[0128] Mo 12 Bi i X 8 k Fe l X 9 m X 10 n O z (II)

[0129] where ​​

[0130] X 1 is bismuth, tellurium, antimony, tin, and / or copper, preferably bismuth,

[0131] X 2 is molybdenum and / or tungsten,

[0132] X 3 is an alkali metal, thallium, and / or samarium, preferably potassium,

[0133] X 4 is an alkaline earth metal, nickel, cobalt, copper, manganese, zinc, tin, cadmium, and / or mercury, preferably nickel and / or cobalt,

[0134] X 5 is iron, chromium, cerium, and / or vanadium, preferably iron,

[0135] X 6 is phosphorus, arsenic, boron, and / or antimony,

[0136] X 7 is a rare earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, germanium, lead, thorium, and / or uranium, preferably silicon, aluminum, titanium, and / or zirconium,

[0137] a is from 0.01 to 8,

[0138] b is from 0.1 to 30,

[0139] c is from 0 to 4,

[0140] d is from 0 to 20,

[0141] e is from 0 to 20,

[0142] f is from 0 to 6,

[0143] g is from 0 to 15,

[0144] h is from 8 to 16,

[0145] x and y are numbers determined by the valence and the number of occurrences of the elements other than oxygen in I,

[0146] p and q are numbers such that the ratio p / q is from 0.1 to 10,

[0147] X 8 is cobalt and / or nickel, preferably cobalt,

[0148] X 9 is silicon and / or aluminum, preferably silicon,

[0149] X 10 is an alkali metal, preferably potassium, sodium, cesium, and / or rubidium, especially potassium,

[0150] i is from 0.1 to 2,

[0151] k is from 2 to 10,

[0152] l is from 0.5 to 10,

[0153] m is from 0 to 10,

[0154] n is from 0 to 0.5,

[0155] z is a number determined by the valence and the number of occurrences of the elements other than oxygen in II.

[0156] The multimetal oxide material having the formula I is known per se from EP 0 000 835 and EP 0 575 897, and the multimetal oxide material having the formula II is known per se from DE 198 55 913.

[0157] In most cases, the feed for oxidation contains a mixture of propylene, air, steam and nitrogen. Steam and nitrogen are used to help control the reactor hot spot temperature and to provide a non-flammable mixture. Advantageously, the feed composition ranges up to about 9% propylene based on moles. The gaseous mixture in the oxidation reactor remains too low in oxygen to be flammable during normal operation. The reactor start-up and shut-down procedures are also designed to avoid flammable feed mixtures.

[0158] Briefly, the process for preparing acrylic acid typically comprises the following steps:

[0159] (a) catalytic gas-phase oxidation of propylene and / or acrolein to acrylic acid to obtain a gaseous reaction product containing acrylic acid;

[0160] (b) solvent absorption of the reaction product;

[0161] (c) distilling the solvent loaded with the reaction product in a column to obtain crude acrylic acid and the solvent; and

[0162] (d) purifying the crude acrylic acid by crystallization.

[0163] Step (a) provides not pure acrylic acid but a gaseous mixture which may essentially contain, in addition to acrylic acid, unreacted acrolein and / or propylene, water vapor, carbon monoxide, carbon dioxide, nitrogen, oxygen, acetic acid, propionic acid, formaldehyde, further aldehydes and maleic anhydride.

[0164] The remaining, unabsorbed reaction gases from step (a) are further cooled such that condensable portions of its low-boiling co-components, in particular water, formaldehyde and acetic acid, can be separated by condensation. This condensate is referred to as acid water. The remaining gas stream (hereinafter referred to as the recycle gas) mainly consists of nitrogen, carbon oxides and unreacted starting materials. Preferably, the recycle gas is partially recycled as a diluent gas to the reaction stage.

[0165] In a commercial facility, the catalytic oxidation section typically consists of two tubular fixed-bed reactors operating in series. Preferably, the oxidation reactor is of the fixed-bed shell-and-tube type with a length of about 3 to 5 meters and a diameter of about 1.9 to about 3.0 centimeters. Each reactor comprises between about 15,000 and about 35,000 tubes. These tubes are filled with catalyst, and optionally a small amount of inert material at the top serving as a preheater section for the feed gas.

[0166] The reactor tubes are cooled on the shell side by a circulating coolant, which is typically molten salt. The temperature of the coolant is controlled by a heat exchanger, for example by circulating the molten salt through a steam generator that produces steam at elevated pressure. The steam is fed to the steam network.

[0167] Vaporized propylene is mixed with steam and air and fed into the first-stage reactor, where propylene is mainly converted to acrolein. The feed composition is typically about 5% to about 7% propylene, up to about 35% steam, and the balance a gaseous source of molecular oxygen, typically compressed air or a mixture of compressed air and absorber off-gas.

[0168] The preheated gas reacts exothermically on the first-stage catalyst, where the peak temperature depends on the conditions and catalyst selectivity. The conversion of propylene to carbon oxides (i.e., carbon dioxide and carbon monoxide) is more exothermic than its conversion to acrolein. At the end of the catalyst bed, the temperature of the mixture drops towards the temperature of the molten salt coolant. Since acrolein at such elevated temperatures can undergo exothermic homogeneous decomposition into carbon oxides, i.e., carbon monoxide and carbon dioxide, the first-stage reactor effluent is typically cooled to about 200 °C to about 250 °C in an inter-stage cooler to prevent homogeneous and non-selective oxidation of acrolein in the pipe leading to the second-stage reactor.

[0169] Compressed air is preferably mixed with the effluent from the first-stage reactor upstream of the second-stage oxidation reactor to provide oxygen for the oxidation reaction. The gaseous mixture rich in acrolein containing some acrylic acid is then passed into the second-stage reactor, which is similar to the first-stage reactor but filled with a catalyst designed to selectively convert acrolein into acrylic acid. The temperature of the effluent from the second-stage reactor again approaches the temperature of the salt coolant. The reaction heat is recovered as steam in an external waste heat boiler and can be further cooled to about 220 °C and / or directly quenched.

[0170] Advantageously, the oxidation operates at the lowest temperature consistent with high conversion. The conversion increases with temperature; selectivity generally only decreases with a substantial increase in temperature. The catalyst life also decreases with increasing temperature. The catalyst is designed to provide high performance under a range of operating conditions, thus allowing a gradual increase in the salt temperature during the operating life of the catalyst to maintain productivity and selectivity close to the initial levels and thus compensate for the gradual loss of catalyst activity.

[0171] The oxidation of propene to acrolein and the oxidation of acrolein to acrylic acid proceed with less than 100% selectivity and are accompanied by the combustion of propene or acrolein on the catalyst, which produces carbon monoxide and carbon dioxide, collectively referred to herein as CO x . It should be understood that since the starting propene is carbon-neutral, the emission of the carbon dioxide by-product does not affect the carbon footprint of the process.

[0172] Acrylic acid can be esterified with the corresponding alcohol (such as methanol, ethanol, n-propanol, isopropanol, n-butanol or 2-ethylhexanol) in a conventional manner to the desired ester, as described above for the esterification of methacrylic acid to produce methacrylate.

[0173] Acrylic acid can optionally be polymerized with one or more comonomers to produce a water-absorbing resin. The water-absorbing resin is used in the production of diapers, tampons, sanitary napkins and other hygiene products and is also used as a water retention agent in market gardening.

[0174] Typical methods for producing a water-absorbing resin include polymerizing a monomer solution or suspension comprising:

[0175] a) acrylic acid, which may be at least partially neutralized,

[0176] b) at least one crosslinking agent,

[0177] c) at least one initiator,

[0178] d) an ethylenically unsaturated monomer optionally copolymerizable with acrylic acid, and

[0179] e) optionally one or more water-soluble polymers,

[0180] The obtained polymer gel is dried, the dried polymer gel is ground, fractionated and subjected to post-crosslinking on the hot surface.

[0181] A suitable crosslinking agent b) is a compound having at least two groups suitable for crosslinking. The crosslinking agent b) is preferably a compound having at least two polymerizable groups that can be polymerized into the polymer network by free radicals. Suitable crosslinking agents b) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallylammonium chloride, tetraallyloxyethane. As the content of the crosslinking agent increases, the centrifuge retention ability decreases and the absorption under pressure reaches a maximum.

[0182] The initiator c) used can be all compounds that generate free radicals under polymerization conditions, such as thermal initiators, redox initiators or photoinitiators. Suitable redox initiators are sodium persulfate / ascorbic acid, hydrogen peroxide / ascorbic acid, sodium persulfate / sodium bisulfite and hydrogen peroxide / sodium bisulfite.

[0183] To further improve the properties, the polymer particles can be post-crosslinked on the surface. Suitable surface post-crosslinking agents are compounds containing groups that can form covalent bonds with at least two carboxylate groups of the polymer particles. Suitable compounds are, for example, polyfunctional amines, polyfunctional amidoamines, polyfunctional epoxides.

[0184] Isobutene is oxidized to produce methacrolein and methacrylic acid

[0185] In another aspect of the present invention, the oxidation reaction is an oxidation reaction in which isobutene produces an intermediate selected from methacrolein and methacrylic acid.

[0186] Suitable oxidation catalysts for oxidizing isobutene to methacrolein are mixed metal oxide catalysts well known in the art.

[0187] No catalyst suitable for the industrial production of methacrylic acid from isobutene in high yield has been found. Therefore, it is industrially advantageous to carry out the reaction in two steps using a catalyst for producing methacrolein from isobutene and a catalyst for producing methacrylic acid from methacrolein.

[0188] However, when producing methacrylic acid in such a two-step oxidation, if the conversion rate of methacrolein is high, it is relatively difficult to obtain a high selectivity of methacrylic acid in the second oxidation step. That is, the selectivity of methacrylic acid formation decreases as the conversion rate of methacrolein increases. Therefore, it becomes advantageous to carry out the second oxidation step under conditions where the conversion rate of methacrolein is relatively low, and then recover the unreacted methacrolein from the reaction product and recycle them back to the second oxidation step. The unreacted methacrolein is separated from the reaction product in the second oxidation step while recovering the target product, methacrylic acid. This is achieved by cooling the reaction product in the second oxidation step to liquefy them, and / or further contacting them with water to separate gaseous components such as oxygen, nitrogen, carbon dioxide gas, etc. As a result, a liquid phase containing methacrolein and / or methacrylic acid is obtained, and these are separated by distillation.

[0189] Epoxidation of ethylene

[0190] In another aspect of the present invention, the oxidation reaction is an epoxidation reaction of ethylene from renewable sources to produce ethylene oxide.

[0191] Ethylene oxide is produced in large quantities and is mainly used as an intermediate for producing several industrial chemicals. Suitable epoxidation catalysts are typically obtained by depositing metallic silver on a support. Highly selective silver-based epoxidation catalysts have been developed, which contain, in addition to silver as the active component, promoter substances for improving the catalytic properties of the catalyst, as described, for example, in WO 2007 / 122090A2 and WO 2010 / 123856 A1. Examples of promoter substances include alkali metal compounds and / or alkaline earth metal compounds and transition metals such as rhenium, tungsten or molybdenum.

[0192] Suitable catalysts typically contain 20% to 35% or 25 to 45 wt.-% of silver relative to the weight of the catalyst.

[0193] As the support material, various porous refractory materials can be used, such as activated carbon, titanium dioxide, zirconium oxide, silica, alumina or ceramic compositions or mixtures of these materials. Preferably, the refractory support is an alumina support. The support preferably has a BET surface area of 0.5 to 3.0 m 2 / g.

[0194] Suitable catalysts can be obtained by

[0195] i) impregnating the refractory support with a silver impregnation solution, preferably under reduced pressure; and optionally subjecting the impregnated refractory support to drying; and

[0196] ii) subjecting the impregnated refractory support to a calcination process;

[0197] Steps i) and ii) may be optionally repeated.

[0198] The epoxidation of ethylene preferably comprises reacting ethylene and oxygen in the presence of an epoxidation catalyst as described above. The epoxidation can be carried out by all methods known to those skilled in the art. All reactors that can be used in prior art ethylene oxide production methods can be used; for example, an externally cooled shell-and-tube reactor (see Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Volume A-10, pages 117 - 135, pages 123 - 125, VCH-Verlagsgesellschaft, Weinheim, 1987) or a reactor with a loose catalyst bed and cooling tubes, such as the reactors described in DE 34 14 717 A1, EP 0 082 609 A1, and EP 0 339 748 A2.

[0199] The epoxidation is preferably carried out in at least one tubular reactor, preferably in a shell-and-tube reactor. On a commercial scale, the epoxidation of ethylene is preferably carried out in a multitubular reactor containing thousands of tubes. The catalyst is filled into the tubes, and these tubes are placed in a shell filled with a coolant. In commercial applications, the inner tube diameter is typically in the range of 20 to 40 mm (see, for example, US 4,921,681 A) or greater than 40 mm (see, for example, WO 2006 / 102189 A1).

[0200] The coolant can be any of several well-known heat transfer fluids, such as tetralin (1,2,3,4-tetrahydronaphthalene). The coolant leaving the reactor can be circulated through a steam generator that generates steam at an elevated pressure. The steam is fed into a steam network.

[0201] In a reactor cooled with boiling water, the coolant is introduced as liquid water into the cooling side of the reactor, most commonly the shell side of the reactor. As the water flows through the cooling side, heat is removed from the process side, and some of the water evaporates into steam. The coolant leaves the cooling side of the reactor as a mixture of water and steam. The steam leaving the reactor shell is removed and can be introduced into the steam network. The temperature of the coolant in the reactor shell is determined by the boiling point of water, which in turn is determined by the pressure at which it operates.

[0202] To prepare ethylene oxide from ethylene and oxygen, the reaction can be carried out under conventional reaction conditions as described, for example, in DE 25 21 906 A, EP 0 014 457 A2, DE 23 00 512 A1, EP 0 172 565 A2, DE 24 54 972 A1, EP 0 357 293 A1, EP 0 266 015 A1, EP 0 085 237 A1, EP 0 082 609 A1, and EP 0 339 748 A2. An inert gas such as nitrogen or a gas that is inert under the reaction conditions (e.g., steam, methane), and also optionally a reaction moderator (e.g., a halogenated hydrocarbon such as chloroethane, vinyl chloride, or 1,2 - dichloroethane) can be additionally mixed into the reaction gas containing ethylene and molecular oxygen.

[0203] The reaction gas preferably contains a chlorine - containing reaction moderator, such as chloroethane, vinyl chloride, or 1,2 - dichloroethane, in an amount of 0 to 15 ppm by weight, preferably 0.1 to 8 ppm by weight, based on the total weight of the reaction gas. The remainder of the reaction gas typically includes hydrocarbons such as methane and also inert gases such as nitrogen. Additionally, other materials such as steam, carbon dioxide, or noble gases can also be present in the reaction gas.

[0204] The concentration of carbon dioxide in the feed (i.e., the gas mixture fed to the reactor) typically depends on the catalyst selectivity and the efficiency of the carbon dioxide removal equipment. The carbon dioxide concentration in the feed is preferably at most 3 vol.-% relative to the total volume of the feed, more preferably less than 2 vol.-%, and most preferably less than 1 vol.-%. Examples of carbon dioxide removal equipment are provided in US 6,452,027 B1.

[0205] The epoxidation of ethylene to ethylene oxide is typically carried out at an elevated catalyst temperature. The catalyst temperature is preferably in the range of 150 °C to 350 °C, more preferably 180 °C to 300 °C, particularly preferably 190 °C to 280 °C, and most preferably 200 °C to 280 °C.

[0206] The epoxidation is preferably carried out at a pressure in the range of 5 to 30 bar. Unless otherwise stated, all pressures in this text are absolute pressures. The epoxidation is more preferably carried out at a pressure in the range of 5 to 25 bar, such as 10 bar to 24 bar, and particularly 14 bar to 23 bar.

[0207] The epoxidation of ethylene is preferably carried out under conditions conducive to obtaining a reaction mixture containing at least 2.3 vol.-% of ethylene oxide. In other words, the ethylene oxide outlet concentration (the concentration of ethylene oxide at the reactor outlet) is preferably at least 2.3 vol.-%. The ethylene oxide outlet concentration is more preferably in the range of 2.5 vol.-% to 4.0 vol.-%, most preferably in the range of 2.7 vol.-% to 3.5 vol.-%.

[0208] The epoxidation is preferably carried out in a continuous process. The epoxidation of ethylene can advantageously be carried out in a recycle process. After each pass, the newly formed ethylene oxide and the by-products formed in the reaction are removed from the product gas stream. The remaining gas stream is supplemented with the required amounts of ethylene, oxygen and reaction moderator and reintroduced into the reactor. The separation of ethylene oxide from the product gas stream and its subsequent work-up can be carried out by customary methods of the prior art (see Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, volume A-10, pages 117 - 135, pages 123 - 125, VCH-Verlagsgesellschaft, Weinheim, 1987).

[0209] The epoxidation of ethylene proceeds with less than 100% selectivity and is accompanied by the production of carbon dioxide. It should be understood that since the starting ethylene is carbon-neutral, the emission of the carbon dioxide by-product does not affect the carbon footprint of the process.

[0210] Ethylene oxide can be subjected to a hydrolysis reaction to produce ethylene glycol, or ethylene oxide can be subjected to an amination reaction to produce ethanolamine and / or ethylenediamine.

[0211] The invention is further illustrated by the following examples.

[0212] Examples (predictive)

[0213] Exemplary embodiments regarding acrylic acid production illustrate the effects of the invention.

[0214] The conversion of 0.7 t of propylene to 1 t of acrylic acid using a standard catalyst produces a total of 0.35 t of CO2 as a yield loss. The cooling of the exothermic reaction zone of the process generates 2.3 t of heated steam from steam condensate.

[0215] To produce this amount of heated steam, 0.14 t of bioethanol will have to be burned. This amount of bioethanol can be saved by interconnecting ethanol dehydration and / or olefin metathesis with acrylic acid production according to the invention. In other words, the combustion of ethanol from a partially renewable source that generates heat is shifted to a later production step, namely the production of acrylic acid, as part of the inevitable yield losses there. The steam requirement for the production of 0.7 t of propylene from renewable sources of ethanol through a series of ethanol dehydration, ethylene dimerization to n-butene, and metathesis reaction between n-butene and ethylene to form propylene is in the range of 2.2 to 3.0 t of steam. Thus, the amount of heated steam generated by heat recovery in acrylic acid manufacture can in principle fully or at least to a large extent cover the steam requirement for the conversion of ethanol to olefins.

Claims

1. A process for manufacturing acrylic acid in combination with the generation of heated steam, the process comprising the steps of: a) subjecting a feedstock comprising ethanol from renewable sources to dehydration to produce an ethylene stream from renewable sources; b) subjecting the ethylene stream from renewable sources to olefin metathesis to obtain propylene from renewable sources; the olefin metathesis comprising (i) and (ii): (i) dimerizing ethylene to obtain n-butene; (ii) a metathesis reaction between the n-butene obtained according to (i) and ethylene to obtain propylene; and c) subjecting the propylene from renewable sources to an oxidation reaction to obtain acrylic acid; and removing at least a portion of the heat generated by the oxidation reaction and transferring at least a portion of the heat to a water stream to produce a heated steam stream.

2. The method according to claim 1, wherein, The heated steam stream is used to provide heat to a heat receiving process.

3. The method according to claim 2, wherein, The heated steam stream is used to provide at least a portion of the heat consumed in at least one of steps a) and b).

4. The method according to any one of the preceding claims, wherein, The oxidation reaction is accompanied by over-oxidation of propylene to carbon dioxide.

5. The method according to claim 4, wherein, 1 to 10 mol.-%, preferably 2 to 8 mol.-% of propylene is over-oxidized to carbon dioxide.

6. The method according to claim 4 or 5, wherein Based on the total amount of CO2 released in the oxidation reaction, the amount of biogenic CO2 released in the oxidation reaction is in the range of 50 to 100 wt.-%.

7. The method according to any one of the preceding claims, wherein, Step b)-(i) comprises: - contacting the ethylene stream from renewable sources with a dimerization catalyst in a dimerization zone; - operating the dimerization zone under conditions effective to produce an effluent consisting essentially of n-butene, a stream consisting essentially of heavier olefins, and optionally an unreacted ethylene stream; - fractionating the effluent to recover a stream consisting essentially of n-butene, a stream consisting essentially of heavier olefins, and an optional ethylene stream; and - subjecting the stream consisting essentially of heavier olefins to hydrogenation to obtain naphtha from renewable sources.

8. The method according to any one of the preceding claims, wherein, The n-butene is a mixed stream comprising 1-butene and 2-butene, and wherein b)-(ii) comprises removing 1-butene from the mixed stream to obtain a 2-butene-rich stream and subjecting the 2-butene-rich stream to the metathesis reaction.

9. The method according to any one of the preceding claims, wherein The n-butene is a mixed stream comprising 1-butene and 2-butene, and wherein b)-(ii) comprises b)-(iia) subjecting the mixed stream to the metathesis reaction to obtain propylene and unreacted 1-butene; b)-(iib) subjecting the unreacted 1-butene to double bond isomerization to obtain 2-butene; and b)-(iic) recycling the 2-butene obtained in step b)-(iib) to step b)-(iia).

10. The method according to any one of claims 1 to 8, wherein, The n-butene is a mixed stream comprising 1-butene and 2-butene, and wherein b)-(ii) comprises passing the mixed stream through a metathesis / isomerization zone comprising both a metathesis catalyst and an isomerization catalyst.

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