TW201016653A - Process for producing acrolein and/or acrylic acid from propane - Google Patents

Abstract

A process for the preparation of acrolein and or acrylic acid from propane, in which the propane is subjected, in a first reaction stage, to a partial oxydehydrogenation with molecular oxygen under homogeneous and/or heterogeneous catalysis to give propylene and the propylene-containing product gas mixture formed in the first reaction stage is then used in at least one further reaction stage for the preparation of acrolein and/or acrylic acid by gas-phase catalytic propylene oxidation. The present process for producing acrolein and/or acrylic acid from propane includes selectively removing major byproducts of the propane and propylene oxidation reactions such as carbon oxides and other inert gases such as argon and nitrogen from the gas stream recycled to the propane oxidation reactor. The present process advantageously reduces cost of producing acrolein and/or acrylic acid from propane by reducing the raw materials (propane and oxygen) requirement, by reducing the energy requirement of the process, and by significantly reducing the size of the major equipment required in the process.

Description

201016653 VI. Description of the Invention: TECHNICAL FIELD OF THE INVENTION The present invention relates to a process for producing acrolein and/or acrylic acid from propylene. [Prior Art] Acetone and acrylic acid are important intermediates for, for example, preparation of active ingredients and polymers. At present, the main method for producing acrolein and/or acrylic acid on an industrial scale is gas phase catalytic propylene oxidation. For example, as described in Ep_a 575 897, propylene is mainly used as a by-product of steam cracking of naphtha to produce ethylene. generate. For example, an industrial process for acrylic acid production involves first converting propylene primarily to acrolein and a small amount of acrylic acid by first reacting a mixture of propylene, air, and steam in a first reactor to form acrolein product in a first reaction step. The acrolein product is then fed to the second reactor without separation of the product for subsequent reaction of acrolein with additional air and steam to form acrylic acid. The product acid containing acrylic acid obtained from the second reactor can be introduced into a collecting device to obtain acrylic acid in the form of an aqueous solution. A 4 knives from the collection unit and containing the remaining exhaust of unreacted propylene are then recycled to the first reactor inlet along with the starting gas mixture of propylene, air and steam. The use of propane welding in other fields is expanding and therefore, there is a possibility of preparing propylene vine and/or acrylic acid without using propylene as a raw material of a natural gas component, such as rawmatenal base. A competitive approach available in industry. 5 201016653 In the past decade or so, research on the production of propylene and acrylic acid by propane instead of propylene in the industry has been extremely significant. The use of propane as a feed source is ideal 'because it is easier to obtain and less expensive than propylene. The use of propane as a feedstock provides a significant advantage in reducing the cost of raw materials and it allows the propylene/acrylic acid to be de-coupled from an ethylene/propylene plant that is extremely capital intensive, as is known in the art. A method of producing propylene with a wide acrylic acid. For example, European Patent 117146 β1 teaches the production of acrylic acid from the firing of propane by propane dehydrogenation to produce an effluent gas stream comprising propylene, hydrogen, carbon oxides and unreacted propane. U.S. Patent Nos. 5,7,5,684, 7,388,106 B2 and 7,321, 〇58 B2 are other examples of processes for preparing acrolein or acrylic acid from propane. These processes for the preparation of acrolein and/or acrylic acid from propane based on dehydrogenation of propane, in combination with acrolein and/or acrylic acid production processes, present significant problems for several reasons, some of which are described below. The dehydrogenation of propylene to propylene produces hydrogen as a by-product, which must be treated to remove hydrogen from the recycle process. Hydrogen is extremely flammable and reduces the flammability limit of the reaction gas mixture, thereby limiting the oxygen content of the reaction mixture. In addition, propane dehydrogenation is a latent endothermic reaction requiring high energy input in the process and is carried out at a temperature of between 50 (TC to 70 (temperature in the range of TC) which is about 25 times that required for the reaction of propylene to acrolein. The temperature of 〇 to 4〇〇〇c is much higher, so it is essentially necessary to cool the effluent before feeding the effluent from the dehydrogenation of propane to the reactor for the formation of acrolein from propylene. On the other hand, the oxidative dehydrogenation of propane The process of reacting propylene with propylene to form acrolein and/or acrylic acid may be easier to combine due to the synergy of 201016653 between the two processes (such as no hydrogen generation during the process), and excess oxygen in the recycle gas may be The oxidative dehydrogenation reactor is used to reduce the reaction temperature of the oxidative dehydrogenation reaction. Further, the propylene oxide oxidative dehydrogenation is carried out at a low conversion rate to provide a desired propylene concentration for the propylene oxidation reaction. U.S. Patent No. 6,492,548 teaches Propylene oxidative dehydrogenation to produce acrolein and acrylic acid from propane. Figure 1 of U.S. Patent No. 6,492,548 shows a method of making propylene. Feeding the gaseous propane feed stream and the gaseous oxygen feed stream to a first oxygenation dehydrogenation reactor containing a heterogeneous oxidative dehydrogenation catalyst, and subsequently feeding the effluent from the first reactor to a subsequent reaction Acryl aldehyde is produced to produce acrolein. The recycle gas stream is also fed to the first reactor. Figure 2 of U.S. Patent No. 6,492,548 shows a process for the manufacture of propylene glycol from propane comprising incorporating into a second acrolein reactor. A third reactor, W097/36848, W097/36849, U.S. Patent No. 6,166,263, and U.S. Patent No. 6,187,963 teach other processes for the oxidative dehydrogenation of acrolein and/or acrylic acid from propane. Converting propane to propylene at low conversion and high selectivity; converting propylene to acrolein; recovering propylene or converting acrolein to acrylic acid; and recycling unreacted propane to the propane oxidative dehydrogenation reactor The oxidative dehydrogenation reaction of propane to propylene typically does not reach the selectivity for complete propylene formation. Typically, at least a small portion of the propylene and propylene are oxidized to carbon monoxide and dioxide. This is also the case when converting propylene to propylene. The selectivity of propane to propylene is usually maximized by oxidative dehydrogenation of propane with relatively low conversion of propylene (eg 5% to 20%). However, this approach only minimizes the by-products such as carbon oxides 201016653 and will accumulate in the process if the by-products are not removed from the recycle process. W〇97/36848 , W097/36849 and U.S. Patent Nos. 6,166,263 and 6'492,548 teach the process of controlling the reaction gas by flushing only the recycle gas and not separating the by-product components from the recycle gas for the continuous recycle process. The mixture of Shenhe 蕾 is tired. When only the knee is punched, the airflow is controlled; during the accumulation of improper by-products in the process, a large amount of flushing of the recycle gas is required, which leads to several disadvantages: (1) a large amount of flushing leads to a large loss of the raw material propane' and propylene. And the oxygen loss is lost. And (2) a large amount of flushing is still insufficient to achieve a low concentration of by-product carbon oxides, resulting in a large-scale decrease in the concentration of propylene and propylene in the feed to the reactor, thereby substantially This reduces the productivity of major equipment such as reactors, absorbers, aftercoolers, recycle compressors and the like in the process. Larger scale flushes increase the concentration of reactants such as propane and propionate in the feed stream to the reactor and the concentration of products such as propylene and propylene and/or acrylic in the product gas mixture, but The large flush rate, which further increases the loss of unreacted propane, propylene and oxygen in the flush, making the overall process uneconomical. U.S. Patent Nos. 6,388,129, 6,423,875 and 6,426,433 teach the use of an oxidative dehydrogenation process to partially convert propane to propylene using modified (oxygen-enriched) air; to convert propylene to acrolein; and, if appropriate, propylene Conversion of aldehyde to acrylic acid; recovery of acrolein or acrylic acid; separation of nitrogen and other inert gases by fractional distillation and recycling of unreacted propane and propylene to an oxidative dehydrogenation reactor, wherein the first reaction zone (oxygen 8 201016653) The molecular oxygen required in the dehydrogenation zone is added as air to the starting mixture of reactant gases fed to the first reaction zone. The method disclosed in U.S. Patent Nos. 6,388,129, 6,423,875 and 6,426,433 uses air to supply oxygen to the oxidative deoximation reactor. Due to the large amount of nitrogen present in the air, a low concentration of propylene is present in the reactor, thereby reducing the advantageous effect of the high heat capacity of the propylene burn in the reaction. The reaction also requires a single pass conversion of propylene to propylene to achieve a sufficient concentration of propylene in the feed to the propylene to acrolein reactor to achieve sufficient productivity in the reactor. In the oxidative dehydrogenation of propane, the greater propane conversion required in such processes results in lower selectivity to propylene formation and further increases in the formation of by-products such as carbon oxides. The fractionation described in the above patents must also be carried out under low temperature conditions, which makes the overall process extremely expensive. U.S. Patent No. 6,541,664 B1 describes a process for the formation of a propylene pass by a propylene plant by means of two catalysts in series. This is achieved by oxidation on the bed and separation of the propane and propylene from the reaction product mixture. U.S. Patent No. 6,541,664 B1 does not describe how the propane and propylene are separated from the product mixture in the process, or even the formation of by-products such as carbon oxides. The prior art method of converting propane to acrylic acid and/or acrylic acid provides inefficiency and high capital cost and high energy cost of the combustion. Accordingly, there is a need to provide an economical process for the manufacture of acrolein and/or acrylic acid from propane via an oxidative dehydrogenation process with reduced overall cost. There is still a need in the industry to further enhance the interest in using propane as a feed source to make propylene and/or acrylic acid. It is also desirable to use propane in addition to the source of the feed to increase the efficiency of the reaction. SUMMARY OF THE INVENTION The present invention provides an improved continuous process for the conversion of propane to acrolein and/or acrylic acid. In the process of the present invention, propane is first partially converted to propylene in a first reaction zone (oxidation dehydrogenation zone with oxygen); and then a propylene-containing product gas stream from the vegetable once zone is fed to another reaction In the zone (propylene oxide zone), in the other reaction zone, the propylene contained in the gas stream is converted into acrolein and/or acrylic acid. This invention relates to a process for the manufacture of acrolein and/or acrylic acid from propylene. ❹ The process of the present invention provides a process step and a device for selectively removing major by-products such as carbon oxides produced in the oxidative dehydrogenation of propane and the propylene oxidation reaction step, and optionally recycling to propane oxidative dehydrogenation Other inert gases such as argon and nitrogen are removed from the gas in the reactor. Selective removal of by-products via the purge gas stream greatly reduces the loss of feedstock propane, propylene, and oxygen, thereby increasing the feedstock (propane and oxygen) yield. This improvement also results in a significant reduction in the size of the primary equipment used in the process, such as reactors, heat exchangers, absorbers, recycle compressors, and the like, thereby significantly reducing the overall capital cost of the process. The object of the present invention is to advantageously reduce the production of acrolein from propane by reducing the feedstock (propane and oxygen) requirements of the process, reducing the energy requirements of the process, and significantly reducing the size of the primary equipment used in the process. Or the cost of acrylic acid. The object of the present invention is also to selectively remove the major by-products such as carbon oxides from the oxidative dehydrogenation of propylene and the propylene oxidation reaction from the gas recycled to the propylene oxide oxidative dehydrogenation reactor. 10 201016653 The object of the present invention is to provide a process for the preparation of acrolein and/or acrylic acid from propane in which propane is subjected to partial oxidation dehydrogenation by molecular oxygen in a first reaction stage to obtain propylene. Next, the propylene product in the gas mixture formed in the first reaction stage is used in at least one other reaction stage to prepare propylene and/or acrylic acid by gas phase catalytic propylene oxidation; wherein the gas is recycled to the reaction At least a portion of by-products formed during the oxidative dehydrogenation and propylene oxidation reaction stages of the propane burn are previously removed or reduced. The process of the present invention advantageously has a selective byproduct removal step to remove the gaseous byproducts of the propylene oxidative dehydrogenation step and the propylene oxidation step. By-products in the process may include, for example, carbon dioxide and carbon monoxide; and optionally include inert gases such as argon, nitrogen, and the like. Although the invention herein is primarily directed to the conversion of propane to acrolein and/or acrylic acid', it will be apparent to those skilled in the art that the present invention can also be applied to the conversion of butane to decyl acrolein and/or methacrylic acid. β [Embodiment] In general, the process of the invention for preparing acrolein and/or acrylic acid from propane comprises a first reaction stage or a first reaction zone in which propane is subjected to catalytic partial oxidation by molecular oxygen. Hydrogen reaction ("oxidative dehydrogenation") to obtain propylene. The catalyst used in the first reaction zone can be homogeneous and/or heterogeneous. Forming a propylene-containing product gas mixture in the first reaction zone and then using the propylene-containing product gas mixture (ie, the effluent from the first reaction zone) in at least one other reaction zone for gas phase catalysis The alkene oxidation reaction produces acrolein and/or acrylic acid. Preferably, the recycle gas stream containing the reaction zone is added to the first reaction zone along with a make-up propane gas and oxygen feed stream to form a gas starting mixture of the first reaction zone. The recycle gas stream is treated to remove certain undesirable gaseous by-products, such as carbon dioxide, prior to addition to the starting gas mixture of the first reaction stage. Instructing the method of invention to enable the source of the feed to be simmered and the rate is critical and can be obtained from a variety of sources, including, for example, propane naturally occurring due to oil field = 夭 . gas generation or exhaust from refinery units . The purity of the propane feed used in the process of the present invention is also not particularly limited. For example, the propane ruthenium feed stream may contain lower alkanes such as ethane 'methane, air or carbon dioxide as impurities. Typically, the propane feed will comprise at least 3 mole percent, preferably at least 50 mole percent, more preferably at least 8 mole percent propane, and most preferably at least 90 mole percent propane. The oxygen source (for oxidative dehydrogenation of propane and propylene oxidation) used in the oxygen-containing gas feed stream used in the process of the present invention is not critical and is available from a variety of oxygen generators. Preferably, the source of oxygen comprises at least about 9 mole percent and more preferably at least about 95 mole percent oxygen. The source of oxygen preferably contains a small amount (e.g., less) of other inert gases, such as nitrogen. Therefore, the use of low oxygen-containing gas streams such as air is not good 'this is because the nitrogen content in the air reduces the concentration of propane in the reaction gas mixture' and thus reduces the beneficial effect of high propane concentration in the reactor'. The cycling ability of propylene, propylene and oxygen causes adverse effects. The modified recycle gas mixture gas stream used in the process of the present invention comprises a recycle gas mixture gas stream comprising: unreacted propane, 12 201016653 gas, other inert gases (such as nitrogen, argon), and by-products: Such as - carbon monoxide, carbon dioxide), these by-product gases have been formed in the present, 丨, A A8, and have been reduced in the re-jujube gas by removing from the recycled gas mixture to these by-products Concentration. The method of the present invention entails removing at least a portion of the by-product of the recycle gas mixture gas stream to form a modified recycle gas mixture gas stream, 'then the reformed recycle gas mixture gas stream is subsequently made in the present invention. The gaseous feed stream (propane and oxygen) is combined to produce propylene and/or acrylic acid. The components contained in the recycle gas mixture may include components in the presence of traces such as propane, 〇2, °0, 仏〇, 〇2, propylene, ethane, ethylene, formamidine and other components. The gaseous by-products which are removed or reduced from the recycled gas mixture are preferably carbon oxides, and are specifically carbon dioxide, for example. After reforming the original content of the initial recycle gas mixture, the resulting reformed recycle gas mixture gas stream preferably contains by-products, such as carbon dioxide, which are lower in concentration than the initial recycle gas mixture. For example, the modified recycle gas mixture gas stream to be used in the present invention may contain components which are normally present in air, such as rare gases, carbon dioxide, water vapor, and the like. The first reaction stage or the first reaction zone of the method of the present invention is an "oxidative dehydrogenation reaction zone" or an "oxidative dehydrogenation zone" in which one part of the feed is burned Converted to propylene (propylene, also known as "proper"), 13 201016653 and the remaining propane burned and loaded with other substantially inert gases used as a diluent for the reaction. The first reaction zone of the novel process of the present invention can be designed to use a homogeneous oxidation de-chemicalizer or a heterogeneous oxidative dehydrogenation catalyst. It is preferred in the present invention to use a heterogeneous oxidative dehydrogenation catalyst. Any effective catalyst for converting propane combustion to propylene by gasification degassing is suitable for use in the present invention. A typical catalyst for the oxidative dehydrogenation of propane is a transition metal oxide such as vanadium oxide or molybdenum oxide or a mixed metal oxide. Catalysts which are particularly suitable for use in the oxidative dehydrogenation of propane in the present invention are described, for example, in U.S. Patent Nos. 4,148,757, 4,212,766, 4,26,822, 5,198,580, and 5,38,933; All of these patents are incorporated herein by reference. An example of a catalyst suitable for use in accordance with the present invention is a catalyst comprising a mixed metal oxide comprising Mo, V, Te and the like. The catalyst used in the process of the present invention may be in the form of pellets, beads or rings containing perforations, or may be in the form of a catalytic component deposited on a refractory carrier. The reaction conditions of the oxidative dehydrogenation reaction zone are as follows: the temperature of the oxidative dehydrogenation reaction is generally from about 200 ° C to about 600 ° C, preferably from about 250 ° C to about 50 (TC, and more preferably from about 350 ° C to About 450 ° C. For the oxidative dehydrogenation reaction, the operating pressure of the reaction is generally from about 1 bar to about 10 bar, preferably from about 2 bar to about 6 bar, and more preferably from about 2 bar to about 4 bar. The reactor pressure typically depends on the multiple drops in the entire recycle gas loop and the operating pressure of the remaining equipment in the recycle loop. Gas phase oxidation off 201016653 The gas space velocity per hour in a hydrogen reaction is typically from about 100 h·1 to about 10,000 h·1, preferably about 300 h·1 to about 6000 h·1 and more preferably from about i000 hi to about 4000 h-1. As used herein, “gas hourly space velocity” ") means the volume of the reactant gas passing through the catalyst in the next hour under standard conditions (〇〇c and 1 atm pressure) divided by the total volume of the catalyst. In the first reaction stage (ie propane oxidation) In the dehydrogenation step Φ ❹ propylene reaction), the molar ratio of propane to oxygen The desired conversion and the selectivity of the catalyst vary. Generally, the molar ratio of propane to oxygen in the gaseous starting mixture is preferably in the range of from about 3:1 to about 40:1, and preferably at about 5:1. In the range of about 20:1, and more preferably in the range of about 5:1 to about 1 〇: 1. Other standards for selecting molar ratio are such that the combined gas feed stream entering the reactor is preferably in the flammable zone. Externally to make the operation of the process safer. The reaction gas starting mixture may also contain other substantially inert components such as HA, c〇2, co, noble gases and unconverted propylene. Unconverted = olefin Means propylene remaining due to incomplete conversion of propylene to propylene and/or acetoacetate in the oxidized zone of propylene. After the propylene oxidation step and after product separation and gaseous byproduct removal zone, The recycle gas mixture recycled to the oxidative dehydrogenation reaction is generally referred to herein as a reformulated recycle gas. The present invention provides the most inferiority of the desired combustion in the reaction gas mixture and is: non-essential and substantially inert Gas (such as carbon oxides, the concentration of the hospital is (4) The molar nr feed is 丙 η 40 冥 40%, preferably at least about 50 mol%, at least about 6 〇 mol % and the best at least ... ear %. For the reaction and 15 201016653 words, reaction The high propane concentration is advantageous because it increases the heat capacity of the reaction gas mixture. The increased heat capacity increases the flammability limit of the reaction gas mixture, thereby making the oxygen concentration in the reaction gas mixture higher and by relieving the reaction. The desired product has a higher selectivity. The concentration of the inert gas (such as N2, CO, co2, water, and sulphur) in the gas mixture feed entering the oxidative dehydrogenation reaction zone can be _, mol%, It is preferably less than 30 m〇l%, more preferably less than 2% fine, and it may be as low as 5 mol% or less. Water is a by-product of the oxidative dehydrogenation of propane and the reaction of propylene to acrolein and/or acrylic acid. Depending on the exact nature of the acrolein and/or hydrazine or acrylic acid product recovery step and the method used to remove the gaseous by-products from the recycle gas to produce a reformed recycle gas, one portion of this water may be present in the recycle gas stream. In the mass recycle gas stream. The concentration of water in the modified recirculating gas may range from about 丨 mol % to about 1 〇 mol %, preferably i mol % to about 5 mol %. In the reaction of propane to propylene or the oxidative dehydrogenation of propane, the selectivity of propylene decreases as the conversion of propane increases. Preferably, the propane oxime dehydrogenation reaction is carried out to provide a relatively low propane conversion and a relatively high propylene selectivity. For example, the conversion of propane is preferably from about 5% to about 4%, and more preferably from about 10% to about 2% Q/0. As used herein, the term "propane C〇nversion" means the percentage of C-burning in the reactor feed. The selectivity for conversion of propane to propylene is preferably from about 7% to about 98%, more preferably from about 8% to about 98%, and most preferably from about (four) to about 98%. As used herein, the term "pr〇pyIene" means the number of moles of propylene produced by the propane reacted per mole, and Table 16 201016653 is not a percentage. Water is a by-product of the reaction. A variety of by-products are also formed, including carbon monoxide, carbon dioxide, hydrogen, methane, ethane, and the like. The main by-products formed are carbon monoxide and carbon dioxide. Oxidative dehydrogenation of propane to propylene can be carried out in any suitable equipment known to those skilled in the art, such as a single reactor or two or more reactors in series or in parallel. Any suitable reactor sequence known to those skilled in the art can be used for the reaction of propane to propylene. For example, the reaction can be carried out in a single stage, or can be carried out in two or more stages, with oxygen being introduced between the stages. The reactor used in the present invention may be, for example, a bundle of tubes containing a casing in which each tube is filled with a catalyst for promoting heat removal; or a fluidized bed reactor. When the propylene product is produced in the first reaction zone, the effluent gas mixture from the first reaction zone is passed to the second reaction zone, and the propylene contained in the effluent gas mixture from the first zone is in the second reaction zone. The catalyst in the second reaction zone is reacted with oxygen to form a propylene road and/or acrylic acid. The first reaction stage or the second reaction zone is a propylene oxidation reaction zone for forming acrolein and/or acrylic acid. Although only two stages or two zones are described with respect to the process of the invention, it is also possible for the process of the invention to be carried out in x or more stages in a single reactor or in a plurality of reactors. The reaction of propylene to acrolein and/or acrylic acid. It is also possible to convert the propylene vapor phase contained in the propylene oxide oxidative dehydrogenation product gas mixture to a propylene oxide and/or propionic acid in a subsequent oxidation stage or in two subsequent oxidation stages. In general, when the acrylic acid is the desired material, two vapor phase oxidative oxidation stages are carried out, however, a one-stage gas phase catalytic oxidation can also be used to convert propylene to acrylic acid. In general, a gas phase catalytic oxidation stage is carried out if acrolein is the desired product. For the process of the invention, the reaction of propylene to propylene does not depend on any particular catalyst' and any catalyst effective for the conversion of propylene to propylene can be used. 9 Typical catalysts include mixed metal vapor catalysts, such as U.S. Patent No. Catalysts disclosed in U.S. Patent Nos. 3,825,600, 3, 649, 930, 4, 339, 355, 5,0..77, 434.., or 5,218,146, all of which are incorporated herein by reference. An example of a catalyst suitable for the reaction of acrylonitrile to acrolein is an oxide catalyst containing Mo, Fe and Bi. Suitable catalysts, for example, which are useful in the oxidation stage of propylene to acrolein, are those described in DE-A 29 09 592; the disclosure of which is incorporated herein by reference. Alternatively, a multimetal oxide catalyst as described in DE-A 1 97 53 817 can be used, which is incorporated herein by reference. The catalyst may be in the form of a non-loaded hollow cylinder catalyst, as described in EP-A 575 897, incorporated herein by reference. A multimetal oxide catalyst comprising Bi, Mo and Fe ❿ can also be used in the propylene oxidation stage, such as from

Nippon Shokubai's ACF-2. The catalyst used in the process of the present invention may be in the form of pellets, beads or rings containing perforations, or may be in the form of a catalytic component deposited on a refractory carrier. Suitable catalysts for the formation of propylene from propylene are available from Nippon Shokubai, such as ACF-4, ACF-7; and from Nippon Kayaku and Mitsubishi. 18 201016653 In the reaction zone for the formation of acrolein from propylene, the gas composition of the feed stream (ie the mixture of the effluent from the first reaction zone and the oxygen which can be added) generally has a total molar amount of about 5 based on the total flow of the feed stream. Molar % to about 3 〇 mol % and preferably about 6 mol % to about 15 mol % propylene content; 'about 8 mol % to about 3 based on the total moles of the feed stream Oxygen content in the range of from about 5% by mole to about 15 mole percent; at least about 40 mole percent, preferably at least about 5 moles, based on the total moles of the feed stream. % propane content; and carbon oxides having less than about 30 mole %, preferably less than about 2 mole %, and more preferably less than about 1 mole %, based on the total moles of the feed stream content. Decreasing the concentration of carbon oxides in the gas composition of the feed stream increases the concentration of propane in the feed stream entering the reaction. The concentration of propane in the feed stream of propylene to acrolein has a beneficial effect on mitigating reactor temperature and improving acrolein selectivity by increasing the heat capacity of the reaction gas mixture. The concentration of vapor in the gas composition of the feed stream depends on the degree of conversion in the first reaction zone because water in the form of steam is a by-product of the Q reaction in the first reaction zone. Water is also a by-product of the reaction in the second reaction zone. It is believed that at least some of the steam has a beneficial effect on the reaction of propylene to acrolein. In the propylene oxidation reaction in the second reaction zone, the molar ratio of oxygen to propylene is in the range of from about 1.1 to about 2 to 5 and preferably from about 12 to about 18. In order to achieve the desired ratio of propylene to oxygen, it may be necessary to add oxygen to the effluent stream of the oxidative dehydrogenation product gas before the product gas enters the propylene oxidation reaction zone. The general reaction conditions for the reaction of propylene to acrolein are as follows: propylene generation 201016653

The reaction to acrolein is operated at a temperature of from about 250 ° C to about 45 (TC and preferably from about 275 ° C to about 4 ° C. The oxidation temperature of propylene to acrolein is generally lower than the oxidative dehydrogenation temperature of propane. Thus, an aftercooler can be provided after the oxidative dehydrogenation zone to cool the effluent from the oxidative dehydrogenation reaction zone to a low temperature, which is then sent to the propylene oxidation zone. In general, the stream exiting the aftercooler ί! The temperature of the object is the township l〇〇t: to about 350 弋, after the comfort is 1 ^) 01 to about 2501, depending on the temperature, pressure and composition of the effluent gas, one part of the water contained in the gas may Condensation due to cooling of the effluent gas. Condensed water can be easily removed from the process. D The reaction pressure for the reaction of propylene to acrolein is from about 1 bar to about 4 bar'. However, low pressure, atmospheric pressure or high pressure may also be used. The pressure is preferably from about 2 bar to about 3 bar. The operating pressure in this reaction zone will be slightly lower than the operating pressure in the oxidative dehydrogenation reaction zone, which is the amount of pressure drop across each reaction zone. The pressure in each zone is affected by the pressure drop across the system. The contact time for the reaction of propylene to acrolein is in the range of from about 0.2 seconds to about 2 seconds and preferably from about 0.5 seconds to about 2 seconds. As used herein, "contact time" is defined as the ratio of the open volume of the catalyst bed (open © volume) to the process volume flow rate under process conditions. The conversion of propylene is preferably at least about 70%, and more preferably at least about 80%. In the reaction of propylene to acrolein, the acrolein selectivity is from about 8% to about 99%, and more preferably from about 90% to about 99%. As used herein, the term "conversion" means the number of moles of propylene that reacts in the propylene fed to the reactor per mole, expressed as a percentage; and the term "selectivity" means The amount of moles of propylene that is generated by the propylene reacted per mole is 20, 2010,653, expressed as a percentage. As previously stated, the selectivity of propylene to acrolein is improved as the propane concentration in the feed stream entering the reaction increases. The present invention describes how to increase the concentration of propane burn in the reaction feed stream by selectively removing improper gaseous by-products of the reaction. In the reaction of acryl to form acrolein, various by-products such as carbon dioxide, carbon monoxide, acetaldehyde, furfural, acetic acid, and allyl acetate are also formed in small amounts. The type of reactor used to convert propylene to acrolein is not critical and may be, for example, a fixed bed tubular flow reactor through which the coolant passes. Fluidized bed reactors can also be used. More details of suitable reactors are known to those skilled in the art. The effluent gas mixture from the propylene oxidation stage is a mixture of acrolein with other components such as propane 'unreacted propylene, water, carbon oxides, excess oxygen, and the like. The acrolein product can be separated from the other components in a manner known to those skilled in the art. If acrolein is the desired product for the process, the 3 propylene-derived product gas effluent is fed to the propylene recovery zone. The type of equipment used to recover the acrolein product from the reaction effluent is known to those skilled in the art. The acrolein separated in this manner can be used as an intermediate for the synthesis of various end products. In another embodiment of the invention, acrolein is not recovered as a product, but the acrolein-containing product gas effluent can be fed to the reaction zone of acrolein to acrylic acid to form acrylic acid. The acrolein-containing product gas effluent can be used for gas phase catalytic oxidation to produce acrylic acid. When acrolein is used to prepare acrylic acid in another gas phase catalytic oxidation stage, the acrolein-containing reaction gas in the propylene oxidation stage is generally transferred to this another oxidation / 21 201016653 stage without separation from the secondary component. The acrolein-containing effluent gas can be cooled, and then the gas effluent is passed to an acrolein oxidation reactor, thereby converting acrolein to acrylic acid. It may also be necessary to add oxygen to the propylene product gas effluent gas stream. The gas stream is then fed to an acrolein oxidation reactor to produce propylene. The oxidation stage of the propylene-containing reaction gas is conveniently carried out, for example, in a fixed bed reactor having a multi-ruthenium catalyst tube, such as, for example, DE-A 44 31 949, DE-A 44 42 346, DE-A All of these patents are incorporated herein by reference in their entirety by reference. The catalyst for the reaction of acrolein to acrylic acid may be any catalyst suitable for converting acrolein to acrylic acid and may be the same or different from the catalyst used to oxidize propylene to propylene. For example, a catalyst suitable for this reaction can be described in U.S. Patent No. 5,218,146, the disclosure of which is incorporated herein by reference. Other catalysts for the conversion of acrolein to acrylic acid are described, for example, in U.S. Patent Nos. 4,892,856, 5, 77,434, 5,198,58, and 5,381,933; This is incorporated herein by reference. A suitable acrylic acid catalyst for the production of acrylic acid is commercially available, for example, from Nippon Shokubai, Japan. The conditions of the acrolein oxidation zone are as follows: the acrolein oxidation reaction is carried out at a temperature ranging from about 180 C to about 350 C and preferably from about 200 ° C to about 320 ° C. The residence time of the reaction mixture in the acrolein oxidation zone is in the range of from about 1 second to about 7 seconds, and preferably in the range of from about 丨5 seconds to about 6 seconds. The operating pressure of the reaction of propylene to acrylic acid is substantially similar to the pressure required for the reaction of propane and propylene to acrolein. The operating pressure in the acrylic acid reaction zone is lower than the operating pressure in the acrolein reaction zone and the propane oxidative degassing zone. The amount of reduction is the pressure drop of each of the aforementioned reaction zones. The conversion of propylene carbonate to acrylic acid is generally at least about 90% or more than 9% by weight; and preferably from about 95% to about 99% or more. The single pass total conversion of propylene to acrylic acid in the two-stage operation is preferably not less than about 7 〇 mol%, and preferably not less than 80 mol%. The effluent gas mixture of propylene oxide to acrylic acid is a mixture of acrylic acid and other components such as propane, unreacted propylene, water, carbon oxides, excess oxygen, propylene, and the like. The acrylic acid-containing effluent gas mixture is then fed to the product recovery zone' to recover the acrylic acid from the gas mixture. The product recovery stage or product recovery zone of the process of the present invention comprises treating a product gas mixture gas stream comprising acrolein and/or acrylic acid formed in the second reaction zone in at least one other zone, thereby self-containing acrolein and/or The product stream and the recycle gas mixture © gas stream are separated from the gas stream of the product gas mixture of acrylic acid. A variety of product separations and improvements known to those skilled in the art can be used in the present invention. For example, acrolein can be separated by partial condensation, absorption in a solvent comprising water, and fractionation from a first effluent stream. For example, propylene can be recovered as described in U.S. Patent Nos. 5,198,578 and 6,492,548 each incorporated herein by reference. Similarly, acrylic acid can be separated from the effluent stream containing acrylic acid from the second reaction zone using a variety of product separations and improvements known to those skilled in the art, such as partial condensation, absorption, and fractionation. For example, it can be absorbed by a solvent (see also DE-A 43 08 087) or by absorption with water or 23 201016653 by partial condensation or fractionation ' or as in US Pat. No. 4,999,452 (which is incorporated by reference) The tantalum method disclosed therein is incorporated herein to recover the acrylic acid produced in the process of the invention. Various known methods of separating acrylic acid are also outlined, for example, in DE_A 1 96 00 955, which is incorporated herein by reference.

The common efflux of all separation methods used is _" residual body; other years of condensed by-products (such as acetyl, acetic acid) that do not contain acrolein and/or acrylic acid, or propylene vine and/or acrylic acid. , allyl alcohol), and the water content of the gas is substantially small or substantially free of water. The remaining t bodies (referred to as recycle gases) contain primarily propane and minor amounts of other components such as unconverted propylene, oxygen, water, carbon dioxide, carbon monoxide, and other substantially inert components (such as nitrogen, argon, etc.) A preferred feature of the separation scheme is that it avoids contaminating the recycle gas stream with a potential catalyst poison of a poisonable oxidative dehydrogenation catalyst, an acrolein or an acrylic catalyst. The presence of an oxidative dehydrogenation catalyst or acrolein/acrylic catalyst poison The unreacted gases, such as propane, propylene and oxygen, are prevented from being recycled to the reaction sequence. The temperature and pressure of the effluent product stream leaving the product recovery zone depends on the particular acrolein or acrylic acid recovery process used, but will typically be separately In the range of from about 30 ° C to about 70 ° C and in the range of from about 1 bar to about 2 bar. It is desirable in the present invention to separate at least a portion of the by-products such as carbon dioxide contained in the recycle gas stream. The recycle gas stream is used in the oxidative dehydrogenation reaction zone as a reformed recycle gas stream, such as carbon monoxide and dioxane The carbon oxide of carbon is an important by-product of the oxidative dehydrogenation of propane and the reaction of propylene to propylene carbonate. 201016653 and/or the reaction of acrylic acid. If these by-products are not removed from the process, the concentration of these components It will accumulate during the recycling process, resulting in a decrease in the concentration of the diluent gas vessel (such as the propylene plant) which is required for the reaction. The reduced propane concentration in the oxidative dehydrogenation reaction requires a large conversion ratio of propane to propylene. The same propylene concentration is achieved in the feed to the propylene oxidation reaction' which reduces the propylene selectivity of the oxidative dehydrogenation reaction and produces even more by-products in the reaction. Similarly, acrolein and/or acrylic acid is formed in propylene. It is also advantageous and desirable to have a higher concentration of propylene in the reaction, wherein the higher propylene concentration and the higher heat capacity of the resulting reaction gas mixture moderate the reaction and increase the production of the desired product (such as acrolein and/or acrylic acid). Therefore, at least a portion of the carbon dioxide contained in the recycle gas is separated, and then the gas is recycled to the first reaction zone. Oxidative dehydrogenation of propane and subsequent In the olefin oxidation reaction, at least a portion of the carbon monoxide contained in the reforming recycle gas is oxidized to carbon dioxide. Therefore, it is not necessary to separately remove carbon monoxide for the method of the present invention. A variety of self-flowing gases are known in the art and commercial use. Separation of Dioxide® Carbon, such as the Kirk_0thmer Encyclopedia of Chemical Technology (Kirk-Othmer)

Encyclopedia of Chemical Technology, Vol. 4 and 15 is incorporated herein by reference. Any method and apparatus known in the art to be suitable for use in the process can be utilized to remove at least a portion of the by-product carbon dioxide contained in the recycle gas mixture to form a reformed recycle gas mixture gas stream. For example, the at least a portion of the recycle gas stream can be removed from the recycle gas 25 201016653 stream by passing at least a portion of the recycle gas stream through an adsorption unit, such as an absorption/stripping unit, using a solvent such as a hot aqueous solution comprising potassium carbonate or sodium carbonate. Carbon monoxide is described in Volume 4 of the Kirk-Othmer Chemical Technology Encyclopedia, which is incorporated herein by reference. Alternatively, at least a portion of the recycle gas can be passed through a filtration unit (such as a filtration unit containing membrane units) that selectively removes at least a portion of the carbon dioxide and preferably a portion of other inert gases, such as nitrogen and/or argon, such as Kirk- This is incorporated herein by reference. In the case where a membrane unit is used to separate at least a portion of the carbon monoxide, the membrane selected in the present application has a high selectivity for separating carbon dioxide and other gases to be removed from the recycle gas. For example, in the industry, cellulose acetate membranes are used to remove carbon dioxide from natural gas. In the case where carbon dioxide is separated from the recycle gas using an absorber/stripping unit, it is preferred to use an aqueous absorbent such as an aqueous solution containing potassium carbonate. Absorption methods using organic compounds such as ethanolamine solutions are not preferred for the process of the present invention and do not prevent contamination of such components. Various variations of the method of using an aqueous carbonate solution are commercially available and practiced. For example, there are at least three commercial methods using hot aqueous carbonate solutions; these methods are Benfield (owned by u〇p), Cab(10)❹

The solution absorbs the gas stream so that at least one bath contained in the bath removes a portion of the carbon dioxide. A portion of the carbon dioxide-containing recycle gas solution flows through the absorber. At least a portion of the carbon dioxide in the carbon causes the gas in the open absorber to be less than the carbon dioxide in 26 201016653. The carbon dioxide-containing water/liquid mixture is sent to a stripper where it is stripped of carbon dioxide from the solution and the resulting lean solution is returned to the absorber for reuse. The efficiency of selective byproduct removal, such as the separation of carbon dioxide from the recycle gas, increases as the pressure in the byproduct separation unit increases. However, an increase in pressure in the selective by-product removal unit that exceeds the pressure required for the remainder of the operation can result in a less economical overall process. Therefore, it is preferred to operate the selective byproduct removal step under the pressure normally required for the remainder of the process, such as at a pressure slightly above the pressure required for the oxidative dehydrogenation reaction. Preferably, the selective byproduct removal step is directly sequenced downstream of the recycle gas pressurization step and upstream of the oxidative deargonization step to remove the byproduct removal unit by utilizing the highest pressure in the recycle gas loop The operating pressure is maximized to maximize the efficiency of the byproduct removal step. The operating pressures for the oxidative dehydrogenation zone in the process of the invention are described in the previous section. In one embodiment, the operating pressure for removal of by-products from the recycle gas stream is within the operating pressure of 2 bar of the oxidative desorption reaction zone, β ❹ $ . The amount of carbon dioxide and other inert gases to be separated from the recycle gas stream of the present invention may range from about 5% to about 99% of the carbon dioxide and other inert gases contained in the recycle gas. Preferably, at least about 20%, more preferably at least about 3%, most preferably at least about 4%, and even more preferably about 50% and up to about 99%, preferably up to about 90%, are separated from the recycle gas, More preferably up to about 80% and optimally up to about 60% of carbon dioxide and other inert gases. The presence of a certain amount of carbon dioxide and other inert gases in the recycle gas is not harmful to the process. Therefore, it is not necessary to achieve a very low content of carbon oxides and other inert gases in the reforming recycle gas. Accumulation of some carbon dioxide in the recirculating gas Zhao will improve the removal efficiency of carbon dioxide. For example, the amount of carbon oxide contained in the gas stream of the modified mixture is modified to recirculate the gas mixture. The total amount is generally from about i mole % to about 3 mole %, preferably from about 2 moles / Torr to about 20 mole % 'and more preferably from about 5 mole % to about 3%. . Passing a small amount of m from m (4) recycling as a flushing gas to control the accumulation of other inert gases (such as nitrogen, argon) that cannot be removed in the selective byproduct removal step. Intended to be configured to be primarily configured to be primarily generated

The invention is described below with reference to circle 1 and 圊2, limiting the scope of the subsequent patent application. Figure 1 shows the process of the invention for producing acrolein; and Figure 2 shows the process of the invention for acrylic acid. t Referring to Figure 1, a method for producing acrolein (generally indicated by the numeral 1), comprising (iv) an oxidative dehydrogenation reactor 30 and an aftercooler 40, a propylene chain reaction having an aftercooler 6〇 5〇, B-Wang Road recovery system 7〇, recycled gas machine unit 8〇 and by-product removal system 9〇.

A small amount of acrylic acid can also be obtained as necessary in the method shown in Fig. 1 and can be recovered as a by-product. Referring again to Figure Bu, a specific example of the present invention will be shown, which will include a smile: 9m 〇 1% propane and, about! A gaseous propane feed stream 31 of other hydrocarbons (such as propylene) and a gaseous oxygen feed stream 32 is fed to the reactor % (i.e., olefins and zone) containing a heterogeneous oxidative dehydrogenation catalyst. That is, an ene k-reactive catalyst such as the preferred catalyst described herein. The oxygen feed is about 99.5 mol / β ‘the rest is inert gas 1 such as argon. The reformed 28 201016653 helium ring gas stream 92 is fed to the reactor 3〇. The upgraded recycle gas stream 92 contains unconverted propane burn and oxygen which have not been converted by this process at previous times. The upgraded recycle gas stream 92 also contains propylene, water, and various non-condensable gases that are substantially non-reactive during the process. Substantially non-reactive gases will include, but are not limited to, carbon dioxide and oxidizing, and nitrogen. All of the feed stream is preheated to near the operating temperature of reactor 30, which can be operated at temperatures between about 400 ° C and about 500 ° C. The pressure of the feed stream can be slightly greater than the reactor pressure, and the reactor pressure can be between about 2 bar and about 3 ® bar. The gaseous material is in operative contact with the solid catalyst in a reactor which can have a variety of designs, including a fixed catalyst bed or a fluidized catalyst bed. The conversion of propane to propylene may range from about 1% to about 2%. Gas product stream 35 contains propylene product, unreacted propane, oxygen, water, minor by-products, and non-reactive feed materials. The first effluent from the propane oxidative dehydrogenation reactor 30 is a crude propylene product stream 35 which is first cooled in an aftercooler 4 Torr to about 3 Torr (where the water stream 41 is introduced into the aftercooler 40 and thereafter The effluent stream 42)' is then mixed with additional oxygen stream 36 to achieve the desired oxygen to propylene ratio, and then sent via stream 37 to the propylene oxidation reactor 5, ie, the propylene reaction zone, at The propylene contained in the effluent in the reactor is oxidized to acrolein. Reactor 50 contains a heterogeneous catalyst for the oxidation of propylene, i.e., an acrolein catalyst, such as the preferred catalyst described herein. Gaseous reactants In effective contact with the solid catalyst in reactor 5, the reactor can have a variety of designs, including a fixed catalyst bed or a fluidized catalyst bed. Reactor 50 can be at a temperature of about 300. (: to about 400.) Operating from about 2 bar to about 3 29 201016653 bar pressure. The conversion rate of propylene containing propylene is about 90 〇 / 〇, but it can also be about 70% to about 100%. c by w < dry circumference. Reactor 50 The main product is acrolein, in which acrylic acid is a trace amount of 吝铷 吝铷 Α 风 风 风 4 product. The effluent gas stream from the reactor 5 在 is introduced in the aftercooler 60 (wherein the soil is introduced into the deionized water stream 61 The aftercooler 6" and immediately from the exhaust stream 60 in the post-paste 60 is cooled to about deg" to allow the flow of gas to flow. The gas stream 51 has a pressure of about 2 £, but it can also be between about 1 bar and about Within the range of 3 bar... ❹ A variety of recovery and improvement schemes known to the skilled artisan (such as absorption and fractionation) can be used to separate acrolein from the other components of the effluent stream 51 using a recovery system or unit. The recovered acrolein is removed from the separation unit 70 as a gas stream 71, and the remaining gas is removed from the unit as stream 72. The temperature and pressure of stream 72 depends on the particular propylene separation process used, but may typically be From about 30 ° C to about 70 ° (in the range of from about 1 bar to about 2 bar absolute), the gas stream 72 consists essentially of a non-reactive gas such as propylene, propylene, oxygen, and various previously described gases. The recycle gas stream 72 is then compressed The selectivity for removal of the working pressure unit 9〇

The force, which is higher than the working pressure of the reactor 30, is followed by selective removal of the secondary stream from the recycle stream 81 by passing at least a portion of the recycle stream 81 from the compressor 80 through the selective byproduct removal unit 90. The product carbon dioxide 'and thus reforms the recycle gas stream 81' to form a reformed recycle gas stream 91 that is withdrawn from the removal unit 9A. The byproduct removal unit 90 can be comprised, for example, of an absorber/stripper system that utilizes an aqueous solvent comprising a potassium carbonate solution and absorbs about 50% of the carbon dioxide contained in the recycle gas. Subsequently, stream 91 is split into a reformed recycle gas stream 92 containing a partial flow rate of 30 201016653 and a small portion of flush stream 93. The magnitude of the purge gas stream 93 is selected to achieve the desired level of other minor amounts of inert gas in the reformed recycle gas. The reformed recycle gas stream 92 and the feed streams 31 and 32 are then mixed via gas streams 33 and 34 to supplement the feed gas stream 34 entering the propane oxidative degassing reactor 30. Figure 2 shows another embodiment of the invention which represents a method configured to generate acrylic acid (generally indicated by the numeral symbol 2). As in Fig. 2, a device similar to that of Fig. 1 was used, but the third reactor 100 was incorporated in the process and placed after the acrolein reactor 50 and before the acrylic acid recovery unit 120. The operation of the oxidative dehydrogenation reactor 30 is the same as described above with reference to FIG. The operation of the acrolein reactor 5 of Figure 2 is very similar to the operation of the reactor 50 described with reference to Figure j, with the possible exception that the temperature, pressure and/or oxygen content may be suitably varied to facilitate the formation of acrylic acid rather than propylene. age. The reactor 50 of Figure 2 may also be connected to the aftercooler as shown in Figure ,, or may not be connected to the aftercooler as appropriate. As shown in Figure 2, the effluent gas stream 51 from the reactor 50 is uncooled, but combined with other oxygen from the gas stream 52 to form a feed stream 53, which enters the acrylic acid reactor 100, i.e., propylene. Acid reaction zone. Reactor 100 contains a heterogeneous catalyst for the conversion of acrolein to acrylic acid, such as the preferred catalysts described herein. Reactor 1 () was designed to be in effective contact with the catalyst and reactant gas. The conversion ratio of propylene to acrylic acid is in the range of about 70% to about 100%. The effluent gas from reactor 100 is cooled in aftercooler ι1 (where deionized water stream m is introduced into aftercooler 110 and vapor stream 31 201016653 112 is discharged from aftercooler 11 )) and sent as stream 101 to The acrylic acid recovery unit is 12 〇. It is possible to separate the acrylic acid product stream 121 from residual reactants, gaseous by-products, and diluent gases in stream ι 22 using a variety of possible recovery schemes known to those skilled in the art. The recovered acrylic acid is removed as a stream 121 from the single 7L 120, and the unreacted gas exits the unit as stream 122. The temperature of the vortex 1 is followed by: depending on the particular method of separation of the two olefinic acids used, but typically in the range of about 3 〇Ί 0 to about τ 〇 1 及 and about i 到It is within the range of about 2 bar absolute pressure. Stream i 22 is primarily composed of propane propylene, oxygen, and various substantially inert gases such as carbon monoxide, carbon dioxide, and nitrogen. The recycle gas stream 122 is compressed by compressor 80 to the working pressure of the selective byproduct removal unit 90 which is higher than the working pressure of the reactor 30. The reformed recycle gas stream 91 is then reformed by removing the by-product carbon dioxide from the recycle gas stream 81 from the compressor 8 in the removal unit 9A. The gas stream 91 is divided into a recycle gas stream 92 containing a majority of the flow rate and a small portion of the purge gas stream 93. The amount of flushing gas stream 93 is selected to prevent a slow accumulation of trace amounts of inert gas, and then gas stream 92 is mixed with feed streams 3 and 32. The following examples are provided to provide a better understanding of the invention, including its representative advantages. The following examples are provided for illustrative purposes only and are not intended to limit the scope of the appended claims. EXAMPLES In the following examples, computer modeling experiments were performed to show the effect of selective removal of dioxin 32 from the recycle gas stream fed to the propane oxidative dehydrogenation reactor. Example 1 In a computer simulation experiment using a commercial method to model soft and physical properties of acrolein from propane, a combination of 823 mol/h of propane, 602 mol/h of oxygen, and a composition of 6454 mol/h or less was modified. Circulating gas: 74.9 mol% propylene, 1.7 mol% propylene, 4.3 mol% water, 〇5.1 mol% C02, 1.6 mol% CO, 4.5 mol% 〇2 * 1.5 mol% N2, and 6.4 mol% other components; The following composition is provided for the reactor feed: 7 1.8 mol% propane, 1.4 mol% propylene, 〇3.6 mol% water, 4.2 mol% C02 > 1.3 mol% CO, 11.3 mol% 02, 1.2 mol% N2, and 6.5 mol% of other components. The above reactor feed is fed to a gas phase catalytic propane oxidative dehydrogenation reactor. 33 201016653 Control the reactor discharge temperature to 450 °C. The conversion of propane was 13% and the propylene selectivity was 90%. The main by-products of the reaction are carbon dioxide and carbon monoxide. Some of the oxidation present in the reactor feed is converted to carbon dioxide in the reactor. The reactor effluent was cooled to 300 ° C in an aftercooler and combined with 921 mol/h of other oxygen, and then the combined gas was passed to a reactor that catalyzes the formation of propylene to acrolein, thereby providing the reactor with the following Composition of the combined feed gas: 53.6 mol% propane burn, 8.4 mol% propylene, 1 3.5 mol% water, 6.3 mol% C02 » 0.8 mol% CO, 11.9 mol% 〇2, and 5.5 mol% other components. The peak temperature of the reactor was controlled at about 300 °C. The conversion of propylene was about 85% and the acrolein selectivity was about 92%. The main by-products of the reaction are carbon dioxide and carbon monoxide, as well as other by-products typically found in the oxidation of propylene to acrolein. The composition of the product gas in the acrolein reaction zone is as follows: 5 3.2 mol% propane burn, 1.2 mol% propylene, 6.6 mol% acrylic acid, 21.5 mol% water, 201016653 7.2 mol% C02, 1.1 mol% CO > 2 mol% 02, and 6.0 mol% of other components. The reactor product gas stream is immediately cooled to 250 ° C in an aftercooler and sent to an absorber to recover acrolein from the gas mixture gas stream, wherein the gas is scrubbed with water to absorb substantially all of the propylene and a small amount of acrylic acid in the water. And other water soluble by-products. The acrolein of the desired purity can be recovered from the acrolein solution obtained by those skilled in the art. The gas leaving the absorber (referred to herein as "recycle gas") has a temperature of 40 ° C and is substantially free of acetonide, acrylic acid, and other water soluble components. The composition of the recycle gas is as follows: 71.1 mol% propane burn, 1.6 mol% propylene, 4.3 mol% water, 9.8 mol% C02, ❹ 1.5 mol% CO, 4.3 mol% 〇2, and 7.4 mol% other components. (gauge pressure), followed by yuan. The gas is sent to the selective by-product removal sheet by pressurizing the recycle gas to a pressure of 2 bar with potassium carbonate, "uyang, you remove the 50% carbon dioxide present in the armor. Carbonate is stripped from the potassium carbonate-enriched solution and the lean solution is recycled back to the absorber. The gas leaving the carbon dioxide absorber 35 201016653 contains less carbon dioxide and is referred to herein as "re-circulating" Modified recyde gas )". The modified re-heavy ring gas is divided into two = points: a very small part (less than 2% of the total amount) and the remaining larger part. The portion of the material is removed as a flushing gas from the process to remove other gases, such as nitrogen, argon, etc., from (d). Mixing most of the remaining reformed recirculating gas _’ flooded the mouth and vines. The results of the examples [shown in Table I are shown.

Comparative Example A

A computer simulation experiment similar to the experiment in Example 1 was carried out, but the selective byproduct removal unit was not used. The flushing rate of the recycle gas was increased from 〇.12 kg/kg of acrolein in Example 1 to 丙烯71 kg/kg of acrolein. The results of Comparative Example A are shown in Table I.

Comparative Example B Another computer simulation experiment was conducted which was an experiment similar to the one in Comparative Example A, in which no selective byproduct removal unit was used. Further, the flushing rate of j gas was compared with that of 丙烯71 kg/kg of acrolein in Comparative Example A.

, 増 added to 1 · 16 kg / kg of acrolein. The results of Comparative Example B are shown in Table I. 36 201016653 Table i Comparative Example A Comparative Example B Example 1 Method for the formation of acrolein from propane of the prior art Low rinsing rate * Method for producing acrolein from propane of the prior art High rinsing rate * Improved method for producing propane by propane Flush gas flow (lb) / propylene 0.71 1.16 0.12 propylene reactor feed composition (mol%) propylene 38 56 72 carbon oxide 50 30 5.5 propylene reactor feed composition (mol%) propylene 4.7 6.7 8.4 Carbon oxides 48 28 7.1 Propylene 30 43 54 Result Acrolein concentration in acrolein reaction effluent (% by mole) 3.7 5.2 6.6 Gas flow rate (lb) / acrolein (lb) entering the acrolein absorber 20 14 11 Water flow rate into acrolein absorber (lb) / acrolein (Λ) 76 55 46 Required propane (lb) / acrolein (lb) 1.25 1.65 1.08 Yield of propane to acrolein and acrylic acid (%) 64 49 74 * The prior art methods in the above embodiments are taught in W097/3 6848 and U.S. Patent Nos. 6,166,263 and 6,492,548. The results in Table I show that although the modified process has a much smaller gas rinsing rate', compared to the carbon oxide concentration of about 3 Torr to 5 〇 mol% in the prior art method, the oxidative dehydrogenation of propane in the improved process (propylene) The concentration of carbon oxides in the reactor feed is only about 6 m〇i%. Similarly, the propane concentration in the feed of the improved process of the present invention is about 72 mol% compared to a propane concentration of about 38 to 56 mol% in the prior art process 37 201016653. In the improved process of the present invention, the high concentration of propane in the feed to the propylene oxide oxidative dehydrogenation reactor provides various benefits such as increasing the heat capacity of the reaction mixture. The high heat capacity moderates the reaction, thereby preferably controlling the exotherm of the reaction of propane to propylene and improving the efficiency. The high concentration of propane also reduces the single pass conversion of the propylene, which further increases the selectivity of the propylene and increases the yield of the desired product. The results in Table I show that the acrolein reactor feed composition is also improved. Although the modified process has a much smaller gas flushing rate, it is improved compared to the 28 to 48 mol% carbon oxide concentration in the prior art process. The carbon oxide concentration in the propylene reactor feed in the process was only about 7 moi%. Similarly, the modified method of the present invention has a propane burn concentration of about 54 mol% as compared with the propane concentration of 30 to 43 mol% in the prior art method. In the process of the invention, the high concentration of propane in the reactor feed is also advantageous for this reactor. In propylene and acrolein reactors, the use of propane instead of carbon oxides as a reactor diluent has a beneficial effect in mitigating temperature rise and increasing reaction efficiency. The results in Table 1 also show that 'the same is converted to propylene in the oxidative dehydrogenation reactor, and the propylene concentration & 8.4 mol% in the acrolein reactor feed in the improved process of the present invention, Only 4.7 mol% to 6 7 m〇1% in the prior art method. This improved process has the effect of increasing the yield of the acrolein reactor and the remainder of the process. The concentration of acrolein in the effluent gas of the reactor in the method of the invention is 64 m〇1%, and the concentration in the prior art method is only 3.6 mol% to 5.1 mol%, which indicates that the yield of the improved method is 201016653. Improved. As shown in Table 1, the improved process of the present invention provides the following additional benefits: (1) The process of the invention requires 15% less propane (1.08 lb propane compared to 丨25 lb propane) / acrolein (lb) product, thereby Significant savings in raw material propane costs. (2) The recycle gas flow rate in the process of the present invention is 11 lb/lb propylene monomer compared to 20 lb/lb acrolein in the prior art. The reduced gas flow rate required in the process of the present invention is almost half that of the prior art process shown in Comparative Example A, allowing the main equipment in the entire recycle gas loop (such as propane oxidative dehydrogenation reaction). The size of the reactor, the propylene oxidation reactor, the post reactor cooler, the acrolein absorber, the recycle gas compressor, etc., is extremely significantly reduced. (3) In the acrolein absorber, compared to the prior art method requiring % water/lb acrolein, the process of the invention requires only 46 lbs of water per lb of acrolein, which allows equipment in the circulating water circuit (such as propylene) The size of the aldehyde absorber and the propylene flocator is reduced in proportion to a decrease in moisture content. (4) The higher acrolein concentration in the acrolein solution from the acrolein absorber (6.4% compared to 3.6% in the previous method) results in more efficient acrolein recovery in the acrolein stripper, thus making propylene The energy required in the aldehyde stripper reboiler is reduced. Thus, the process of the present invention provides extremely significant raw materials, operating costs, and capital cost savings over prior art processes. When the preparation of acrylic acid involves further oxidation of acrolein to acrylic acid, this improvement can be used to form acrolein propylene 39 201016653 «ϋβ & Μ ': The invention has been described in terms of specific aspects, but it is also intended by those skilled in the art. For example, other alternatives to the invention may include the use of the process of the invention to produce methacryl or methacrylic acid from isobutyl (tetra). [囷 简单 说明 】 】 ” 说明 说明 说明 周 周 周 周 周 周 周 周 周 周 周 周 周 周 周 周 周 周 周 周 周 周 周 ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ The same elements are used throughout the drawings to designate the same parts. Figure 1 is a simplified process flow diagram showing one embodiment of the method of the invention for converting propane to propylene. Figure 2 is a simplified process flow block Figure showing a specific example of the process of the invention for converting propane to acrylic acid. [Explanation of main component symbols] 10 : Method 20 for producing acrolein: Method 30 for configuring acrylic acid: Reactor 31: Feed stream 32: Feed stream 33: Stream 34: Feed stream 35: Gas product stream 36: Oxygen stream 37: Gas stream 201016653. 40: Aftercooler 41: Water stream 42: Discharged steam stream 50: Reaction 51: effluent gas stream 52: gas stream 5 3 : feed stream 60: aftercooler © 61: deionized water stream 62: vented steam stream 70: recovery system or unit 71: gas stream 72: gas stream 80: compressor unit 8 1 : Recirculation airflow 90: removal system or unit 〇 91: reformed recycle gas stream 92: reformed recycle gas stream 93: flush gas stream 100: reactor 10 1 : gas stream 110: aftercooler 111: deionized water stream 112: vented steam stream 41 201016653 120 : recovery or separation unit 12 1 : acrylic acid product stream 122 : gas flow

42

Claims (1)

201016653 VII. Patent application scope: 1. A method for preparing acrolein and/or acrylic acid from propane, comprising feeding a reaction gas starting mixture to a first reaction zone; wherein the reaction gas starting mixture comprises propane, molecular oxygen and a reforming recycle gas mixture gas stream containing at least a propane burn; wherein in the first reaction zone, the propane contained in the starting mixture of the reaction gas is subjected to partial oxidation dehydrogenation by molecular oxygen under the action of a catalyst, thereby Obtaining a product gas mixture comprising propylene as a first effluent; wherein, the propylene-containing product gas mixture formed in the first reaction zone, ie the first effluent, is subsequently used in at least one other reaction zone Producing acrolein and/or acrylic acid by gas phase catalytic propylene oxidation to form a product gas mixture gas stream containing acrolein and/or acrylic acid; wherein the acrolein and/or formed in the at least one other reaction zone Or a product gas mixture stream of acrylic acid is used in at least one separation zone, thereby from the acrolein and And or a product gas mixture of acrylic acid gas stream separating a product stream comprising acrolein and/or acrylic acid and a recycle gas mixture stream comprising propane and a quantity of by-products; wherein the recycle gas is separated from the gas stream of the recycle gas mixture At least a portion of the by-products contained in the mixture gas stream to form a reformed recycle gas mixture gas stream, and wherein the reforming recycle gas mixture gas stream is added to the reaction gas starting point of the first reaction zone In the mixture. 2. A process for the manufacture of acrolein from propane comprising the steps of: (i) a feed stream comprising (a) propane burned, (b) oxygen and (c) a propane-containing reformed recycle gas stream comprising propane 43 201016653 Passing to a first reaction zone in which the feed stream is contacted with a propane reaction catalyst under conditions effective to promote partial oxidative dehydrogenation or oxidative dehydrogenation of propane to provide propylene, unreacted C a first effluent gas stream of fire, water and carbon oxides; (11) transferring the first effluent gas stream to a second reaction zone, wherein the first household gas flow is promoted to promote the gas flow in the second reversal zone The desired propylene is converted into a propylene oxime strip, and the propylene Xinpi mushroom catalyst is contacted to provide a second effluent stream comprising propane, acrolein and carbon oxides; (iii) separating propylene from the second effluent stream Road, thereby providing (a) a product stream comprising acrolein and (b) a recycle gas stream comprising propane and carbon oxides; (iv) selectively removing at least a portion of by-product carbon dioxide from the recycle gas stream to form Contains C The reformer recycle gas stream; the modified and (v) at least a portion of the recycle gas stream from step is recycled to the first reaction zone, thereby constituting a portion of the feed stream. 3. A method for producing acrylic acid from propylene, comprising: (i) delivering a feed stream comprising (a) propane, (b) oxygen, and (c) 13 recirculating gas comprising propane to a reaction zone in which the feed stream is contacted with a propane reaction catalyst under conditions effective to promote partial oxidative dehydrogenation or oxidative dehydrogenation of propane in the first reaction zone to provide propylene, unreacted propane, water, and a first effluent gas stream of carbon oxide; (Η) transferring the first effluent gas stream to a second reaction zone, wherein the first effluent gas stream is in effect to promote conversion of propylene contained in the gas stream into Contacting with an acrolein reaction catalyst under acrolein conditions, whereby 44 201016653 provides a _ / pit iron stream i containing propane, acrolein and carbon oxides, (that is, transferring the second effluent gas stream to the acrylic acid reaction zone, The second effluent gas stream is contacted with the propylene reaction catalyst under conditions effective to promote the conversion of the propylene (tetra) contained in the gas stream to the propylene reaction zone, thereby providing the propylene, propionate and carbon oxides. It Three effluent gas stream; (⑺ third effluent stream from the acrylic acid separation to provide (. a product stream comprising acrylic acid and (1) a recycle gas stream comprising propane and carbon oxides; (v) selectively removing at least a portion of by-product carbon dioxide from the recycle gas stream to form a reforming recycle comprising propane And (W) recycling at least a portion of the upgraded recycle gas stream to the first reaction zone to form a portion of the feed stream. 4. The method of claim 3, wherein the secondary gas contained in the recycle gas mixture stream is removed from the recycle gas mixture stream by an adsorption process, a filtration process, or a combination thereof. A portion of the product thereby forming a stream of the reformed recycle gas mixture. 5. The method of claim 1 to 3, wherein the method comprises: removing - a small portion of the modified recycle gas mixture gas stream containing an inert gas as a flushing gas stream, & Except at least - part of the inert gas. 6. The method of claim 1, wherein the first effluent, the first effluent, the first effluent, the first effluent, the first effluent, the first effluent, the first effluent Cool to a temperature lower than the initial temperature of the effluent 45 201016653. ^ If you apply for a patent range! The method of item 3, wherein the recycle gas is pressurized upstream of the selective byproduct removal step such that the pressure in the product removal unit is throughout the recycle gas loop. 8. If you apply for a patent scope! The method of item 3, wherein the by-product of the selective removal from the recycled fluorine stream comprises carbon oxides and carbon oxides. :- 9. The method of claim 3, wherein the carbon dioxide is removed from the recycle gas stream by an absorption method using a solvent solution; and wherein the solvent solution comprises an aqueous potassium carbonate solution or an aqueous sodium carbonate solution. A method of applying the patent range _! to item 3, wherein the carbon dioxide is removed from the recycle gas stream by a transition process using a separation material; and wherein the separation material comprises a polymer film. 11. The method of claim 3, wherein the single pass is removed from the recycle gas stream and is recommended to about 99% by-products including carbon oxides and/or carbon dioxide to form the modification. Mass recycle gas stream. 12. The method of any of claims 3 to 3, wherein the modified carbon dioxide and/or carbon dioxide is removed from the recycle gas stream in a single pass to form the reformed recycle gas stream. 13. The method of claim 2, wherein the concentration of carbon oxides in the reformed recycle gas stream is from about 1 mole percent to about the total moles in the reformed recycle gas stream. 3 〇% ear. 14. The method of claim 4, wherein the reaction gas vessel initial mixture or the feed stream comprises at least 50 mole percent of the total mole 46 201016653 in the feed stream. Propane. The method of claim 1, wherein the cough reactive gas starting mixture or the feed, the inert gas including the carbon oxide in the feed is in the feed stream The total number of moles is less than 40 mol%. ^ The method of the first to third paragraphs of the patent range, wherein the reaction gas (iv) is in the initial mixture or the cyan and oxygen in the feed stream is fine per mole. Oxygen is present in an oxygen ratio of from about 5 to about 10 moles of propane. ❹ 17. The method of claim 3, wherein the conversion of propane is from about 5% to about 40% and the selectivity of propane to propylene is from about 70% to about 99%. 18. The method of claim 3, wherein the concentration of propane in the feed stream entering the propylene oxidation zone is at least about 40 mole percent based on the total moles of the first effluent gas stream. . 19. The method of claim i, wherein the concentration of propylene in the feed stream entering the propylene oxidation zone is from about 5 mole percent to about the total moles in the feed stream. 20 moles %. The method of claim 1, wherein the conversion of propylene to acrolein in the reaction of propylene to acrolein is from about 7% to about 99%. /. The selectivity for conversion of propylene to propylene is from about 8% to about 99%. 21. The method of claim 1, wherein the propylene concentration in the second effluent gas stream is at least 5 moles per gram of total moles in the second effluent gas stream. 22. For example, in the scope of patent application, items 1 to 3, the unit ratio of propane 47 201016653 to acrolein (the mass flow rate of propane in the feed stream is greater than the acrolein product stream) The mass flow rate of the acrolein product is less than about 1.2. 23. The method of claim 1 to 3, wherein less than about 5% of the reformed recycle gas is purged from the process (mass flow rate of the flush gas stream is greater than mass flow rate of the reformed recycle gas stream) rate). , schema · (such as the next page) 48