FI89795B - Alkylation/transalkylation process for selective production of monoalkylated aromatic compounds - Google Patents

Description

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This invention relates to an improved alkylation / transalkylation process using a dual reactor system using various catalysts to selectively prepare a monoalkylated aromatic product. More specifically, the present invention uses a solid phosphoric acid catalyst to catalyze the alkylation reaction and an acidic crystalline aluminosilicate material to catalyze the transalkylation reaction. The invention also uses the synergy of the two reaction steps and the two separation steps to produce a highly pure monoalkylated aromatic product in better yields than those obtained using only one alkylation reaction zone.

Alkylation of aromatic compounds with an alkylating agent in the presence of an alkylation catalyst is a method well known for its ability to produce monoalkylated aromatic products such as ethylbenzene, cumene, linear alkylbenzenes, and so on. Such monoalkylated aromatic compounds are important chemical precursors in the manufacture of detergents and polymers, among others. Alkylation catalysts known to be capable of preparing alkylated aromatic compounds include the well-known Friede1-Crafts catalysts, sulfuric acid, phosphoric acid, fluoric acid, and aluminum chloride in either liquid or solid support form. Solid granular catalysts such as clays, zeolites and amorphous materials have also been used as alkylation catalysts in both modified and natural forms.

The use of a transalkylation reaction zone in connection with an alkylation reaction zone in the preparation of monoalkylated aromatic compounds is also known. By using a transalkylation reaction zone in one method in combination with an alkylation 2

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with the reaction zone can be alkylation reaction zones. use under conditions leading to a higher degree of conversion due to the ability of the transalkylation reagent to convert undesired polyalkylated aromatic compounds formed under higher degree of alkylation zone conditions to the desired monoalkylated aromatic compounds. Transalkylation catalysts known to be useful in the preparation of alkylated aromatics from polyalkylated aromatics include Friede1-Crafts catalysts such as sulfuric acid, phosphoric acid, aluminum chloride in either liquid or solid support form, and the like. Solid granular catalysts such as clays, zeolites, and amorphous materials have also been used as transalkylation catalysts.

Numerous process formulas are known for the preparation of monoalkylated aromatic products using an alkylation reaction zone, a transalkylation reaction zone and a separation zone, and using various product, feed intermediate intermediates. One disadvantage of known alkylation / transalkylation processes is the sometimes rapid deactivation of transalkylation catalysts due to the presence of aromatic trialkyl compounds and higher boiling compounds in the feed to the transalkylation reaction zone. This rapid deactivation requires frequent regeneration of the catalyst or frequent renewal of the transalkylation catalyst. Replacement or frequent regeneration of the deactivated transalkylation catalyst can therefore be time consuming and expensive.

Another problem with inherently existing alkylation processes using a Friede1-Craft catalyst, such as solid phosphoric acid or fluoric acid, as the alkylation catalyst is that many of these catalysts require water feed and produce an extremely corrosive slurry as a by-product. When using such highly active slurry generating catalysts in the alky Loint process, the process has to be carried out under single run conditions leading to high-f-I -.f -., 3 degree conversion, which tends to form larger amounts of undesired di- and trialkylated aromatic compounds. The addition of a transalkylation reaction zone containing a stable active transalkylation catalyst to such an alkylation process allows the conversion of dialkylated aromatic compounds to monoalkylated aromatic compounds under high degree conversion conditions without adversely affecting the use of the transalkylate.

A new process using a combination of an alkylation reaction step, a first and a second separation step and a transalkylation reaction zone and using a solid phosphoric acid alkylation catalyst and a crystalline aluminosilicate titranalkylation catalyst has been found to be very useful. In addition, it has been found that by separating the dialkylated aromatic compounds from a portion of the undesired hexylbenzene product and substantially all of the trialkylated aromatic compounds and higher boiling compounds, the process can be performed much more efficiently with the added benefit of prolonging the life of the transalkylation catalyst. Finally, a further advantage of the transalkylation catalyst, which has surprisingly been found to give the best results in the above-mentioned alkylation / transalkylation process, is that it can be regenerated by washing the catalyst with hot benzene.

In one general aspect, the present invention relates to an improved alkylation / transalkylation process comprising an alkylation reaction zone comprising an alkylation catalyst comprising a solid phosphoric acid component, a first alkylation zone, a first separation zone, and a crystalline aluminic acid. an aromatic substrate reacts with each other to produce a monoalkylated aromatic product. The first separation zone is characterized by separating two fractions: (1) an unreacted aromatic substrate for use as part of the alkylation reaction zone and / or transalkylation reaction zone feed, (2) compounds having boiling points higher than the desired - and trialkylated aromatic compounds, and (3) a monoalkylated aromatic compound which is recovered as the desired product. An undesired product stream comprising hydrocarbon compounds having a lower molecular weight than the aromatic substrate is also recovered in the first separation zone. The second separation zone is characterized in that it is fed with a fraction from the first separation zone containing compounds having a higher boiling point than the desired monoalkylated aromatic compound, and separates from this stream a fraction rich in dialkylated aromatic compound and fractions having a boiling point of this. higher and lower than the boiling point of the aromatic compound-containing fraction.

It is a further object of the present invention to use a solid phosphoric acid catalyst as the catalyst for the alkylation reaction zone and a crystalline aluminosilicate catalyst bound to an inorganic oxide as the catalyst for the transalkylation reaction zone. It should be further noted that the alkylating agent used in the process may be an alkene, an alcohol, an alkyl halide, an alkyl sulfonate, or a mixture thereof, wherein the number of carbon atoms of the alkylating agent is in the range of 2 to 18.

In a particular embodiment, the present invention relates to a process for the preparation of isopropylbenzene, hereinafter referred to as cumene, from the alkylation reaction of benzene used as an aromatic substrate with propylene as an alkylating agent. The alkylation reaction takes place in an alkylation reaction zone containing a solid catalyst comprising a phosphoric acid component in the form of spheres, extrusion products or granular particles. The alkylation reaction zone is further known for its ability to receive i 5 j ...... f, the recycled portion of the unreacted aromatic substrate recovered in the first separation zone. Liquid fractions comprising the entire product stream of the alkylation reaction zone and the entire product stream of the trans-reaction zone are directed to the first separation zone into fractions to be separated, comprising a benzene-rich fraction, a compound containing higher than the ku-menen. The liquid fraction rich in compounds with a higher boiling point than cumene and recovered in the first separation zone is then directed to the second separation zone where it is separated into a diisopropylbenzene-rich fraction and fractions with a high boiling point or higher fractions. a diisopropylbenzene-rich fraction. The transalkylation reaction zone contains a crystalline aluminosilicate catalyst in the form of spheres, extrusion products or granular particles. The catalyst for the transalkylation reaction zone is preferably mordenite bound to 5-95% by weight of an inorganic oxide support selected from the group consisting of Al 2 O 4, SiO 2, AlPO 4 and mixtures thereof. In addition, the crystalline aluminosilicate transcylation catalyst may be modified by vapor stabilization, acid modification, ion exchange, and the like. The feed to the transalkylation zone may consist of a portion of the separated unreacted benzene fraction and a diisopropylbenzene-rich fraction from which part or all of the unreacted benzene fraction is recovered in the separation zone. These and other embodiments of the present invention will become apparent from the following more detailed description.

U.S. Patent 4,008,290 describes the use of a solid phosphoric acid polyalkylation catalyst in a process comprising a transalkylation reaction zone similar to, but not identical to, the present invention. 6 0.7 7 described in U.S. Patent 4,008,290? Method 5 differs from the method of the present invention in that it circulates the effluent from the alkylation reaction zone to the feed to the alkylation reaction zone for temperature and conversion control purposes. The process of this application does not specifically use direct recycling of the product of the alkylation reaction zone because the recycled material contains an acidic slurry component formed by the action of water on solid phosphoric acid. The acid sludge in the recycle stream adversely affects the life of the alkylation catalyst and is also corrosive in typical process metallurgy. A further distinguishing feature is the feature of the present invention that the feed to the transalkylation reaction zone comprises mainly dialkylated aromatic compounds and an aromatic substrate in order to maximize the life of the transalkylation catalyst while increasing the conversion efficiency of the entire process. The second separation zone is used in the process of this invention to provide a highly pure dialkylated aromatic fraction. According to U.S. Patent 4,008,290, instead, the entire heavy alkylate stream containing di-, tri- and polyalkylated aromatic compounds and recovered in a single separation zone is used as the feed to the transalkylation reaction zone. The inclusion of components heavier than dialkylated aromatic compounds in the feed to the transalkylation reaction zone has been found to cause detrimental accelerated deactivation of the transalkylation catalyst.

The unique process combination of this invention has surprisingly been found to be very useful in the preparation of a monoalkylated aromatic compound from a feed comprising an aromatic compound and an alkylating agent and in which the desired monoalkylated aromatic product is obtained in high yields in a process characterized by efficient catalysts. , inside-väks i.

The invention will become more apparent from the accompanying drawing, the sole figure of which is a flow chart, not limited to the invention, which is an example of an embodiment of the method according to the invention.

The first step of the process of this invention comprises directing an alkylating agent and an aromatic substrate mixed with an alkylation reaction zone containing an alkylation catalyst. The A1 alkylating agent which can be fed to the alkylation reaction zone can be selected from the group consisting of mono-olefins, diolefins, polyolefins, acetylene-containing hydrocarbons and also alkyl halides, alcohols, ethers, esters of various carboxylates and alkyl sulfates, alkyl sulfates, alkyl esters. The most preferred olefinic compounds are olefinic hydrogens, which include monoolefins containing one double bond in the molecule. The monoolefins that can be used as the olefin compounds in the process of this invention are either normally gaseous or normally liquid and include ethylene, propylene, 1-butene, 2-butene, isobutylene, and higher molecular weight, normally liquid olefins such as various pentenes, hexenes, heptenes, octenes and mixtures thereof, and even higher molecular weight liquid olefins, the latter including various olefin polymers having from about 9 to about 18 carbon atoms in the molecule, such as propylene trimer, propylene tetramer, propylene pentamer, etc. -olefins such as cyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, etc. may be used, although not necessarily with similar results. Other hydrocarbons such as paraffins, naphthenes and the like containing from 2 to 18 carbon atoms may also be present in the alkylating agent.

According to a preferred embodiment of the present invention, the monoolefin contains at least 2 and at most 14 carbon atoms. More specifically, the monoolefin is preferably propylene.

The aromatic substrate of the present invention which feeds 8 r,; the alkylation reaction zone in admixture with an alkylating agent may be selected from aromatic compounds, alone or in admixture, with benzene and monocyclic alkyl-substituted benzene having from 7 to 12 carbon atoms and having the structure G to R 11 wherein R is methyl, ethyl or a combination thereof, and n is an integer from 1 to 5. That is, the aromatic substrate portion of the feed may be benzene, an aromatic alkyl radical containing 1 to 5 methyl and / or ethyl group substituents, and a mixture thereof. Non-limiting examples of such raw material compounds include benzene, toluene, xylene, ethylbenzene, mesitylene (1,3,5-trimethylbenzene) and mixtures thereof. It has been found to be particularly advantageous that the aromatic substrate is benzene.

The alkylation reaction zone contains an alkylation catalyst. One particularly preferred alkylation catalyst comprises a solid phosphoric acid-containing composite compound. A phosphoric acid-containing composite compound can be prepared by combining a phosphoric acid, such as pyro- or tetraphosphoric acid, with a solid support. It is not intended to show that the different phosphoric acids that can be used provide catalysts that have similar effects to any given reaction reaction, since each catalyst prepared from different acids and with slightly modified procedures has its own characteristic effect.

Triphosphoric acid, which can be represented by the formula H 2 P 2 O 2, can also be used as one starting material for the preparation of a phosphoric acid-containing composite compound used in the alkylation reaction zone of this invention.

A mixture of phosphoric acid, commonly referred to as polyphosphoric acid, can also be used to prepare a composite compound. Polyphosphoric acid is prepared by heating orthophosphoric acid or pyrophosphoric acid or mixtures thereof with which is generally found to contain from about 79% to about 85% by weight P 2 O 2.

Tetrafosphoric acid of the general formula HgP 2 O 3> corresponding to the double oxide formula 3H_0.2PnO, _ can be considered as an acid which

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is obtained when four molecules of orthophosphoric acid, H 2 PO 4, lose three hydrogens. Tetraphosphoric acid can be prepared gradually or in a controlled manner by removing water or heating orthophosphoric acid and pyrophosphoric acid, or by adding phosphorus pentoxide to these acids in appropriate amounts.

The phosphoric acid-containing composite compound may comprise a large surface area solid carrier. The term "large surface area" means an area measured by a surface absorption method in the range of about 25 m / g to at least 2 about 500 m / g, and preferably a carrier having a surface area of about 2,100-300 m / g. Therefore, satisfactory supports for the preparation of the catalysts used in the process of this invention include high surface area crystalline alumina variants such as gamma, etha- and theta-aluminas, although they may not be of uniform suitability. In addition to the above-mentioned gamma, etha- and theta-aluminas which can be used as solid supports, other refractory oxides and mixtures thereof, such as silica, zirconia, magnesium oxide, thorium oxide, etc., silica-alumina, silica-magnesium oxide dia, alumina-silica-magnesium oxide, alumina-dithium oxide, alumina-zirconia, etc. may also be considered for use as solid supports in the alkylation catalysts of the process of this invention.

The phosphoric acid-containing composite compound used in the alkylation reaction zone may contain from about 8% by weight or less to about 80% by weight or more of phosphoric acid, and preferably from about 10% to about 75% by weight of phosphoric acid.

In addition to the solid phosphoric acid alkylation catalyst that can be used in the alkylation reaction zone, it is contemplated to use other alkylation catalysts, such as a borohalide-modified refractory inorganic oxide catalyst, as well as various crystalline aluminosilicate catalysts.

In a continuous process for the alkylation of aromatic hydrocarbons with olefins, the reagents described above are fed continuously to a pressure vessel, preferably containing the solid phosphoric acid catalyst described above. This feed mixture can be fed to the alkylation reaction zone containing the alkylation catalyst at a constant rate or alternatively at a variable rate. Normally, the aromatic substrate and the olefin-containing alkylating agent are contacted with each other in a molar ratio of about 1: 1 to 20: 1, and preferably in a molar ratio of about 2: 1 to 8: 1. Feeding at these well-established molar ratios helps to maximize the life of the catalyst by minimizing catalyst deactivation caused by the accumulation of coke and heavy materials on the catalyst. The catalyst may be in one layer in the reactor vessel or it may be divided into several layers in the same reactor. The alkylation reaction system may contain one reaction vessel or several reactor vessels in series. The feed to the reaction zone can take place vertically upstream or downstream through the catalyst bed in a typical plug flow reactor or horizontally through the catalyst bed in a radial flow reactor.

In some cases, in order to maintain the reaction temperature in the preferred range and thus reduce the formation of undesired polyalkylated aromatic compounds, it may be desirable to cool the reagents to dissipate the heat generated by the reaction. A cooling stream consisting of an alkyl olefin or a portion of an acid syrup-free monoylated aromatic fraction or aromatic substrate recovered from the first separation zone, or mixtures thereof, can be injected by alkylation. to dissipate heat and to make additional quantities of olefiinialkylointiainetta and unreacted aromatic substrate at different points of the reaction zones. This is accomplished, for example, a single-stage reactor by injecting several times in the above cooling stream components into the reaction zone of strategically placed feed pipes leading to said reaction zone. Jäähdytysmate-als, which is injected into either a single stage reaction system in or multi-stage reaction system , quantity and composition may vary as required.The advantages of multiple injections are the cost of expensive refrigeration equipment. elimination of the process in the process, better selectivity in the formation of the desired alkylated aromatic compound, providing greater heat reduction and optimizing the molar ratio of olefin to aromatic compound throughout the reaction zone, resulting in a better yield of the desired monoalkylated aromatic compound.

Temperatures suitable for use in this process include temperatures that initiate the reaction of the aromatic substrate and its particular olefin, which is used to selectively prepare the desired monoalkylated aromatic compound. In general, suitable temperatures are from about 100 ° C to about 390 ° C, especially from about 150 ° C to about 275 ° C. Pressures suitable for use herein are preferably higher than about 1 atm, but should not be higher than about 130 atm. A particularly favorable pressure range is from about 10 atm to about 40 atm; the rate of liquid passing through the catalyst per hour (LHSV) based on the feed rate of benzene is about 0.5 h ~ 1 _ about 50 h-1 and especially about -1 -1 1 h - about 10 h. It should be noted that the combination of temperature and pressure used herein should be such that the alkylation and transalkylation reactions occur substantially in the liquid phase. In the liquid phase, alkylated aromatic 12. In the process for the preparation of compounds, the catalyst is continuously washed with reagents, which prevents the accumulation of carbonaceous precursors on the catalyst. As a result, less carbon is formed on said catalyst, which prolongs the life of the catalyst compared to the gasase alkylation process, where carbon scaling and catalyst deactivation are a major problem. In order to further slow down the rate of deactivation of the catalyst, a sufficient amount of ^ 2 can be added to the feed of the alkylation reaction zone and to the feed of the transalkylation reaction zone to saturate the liquid feed of the reaction zone in question. The addition of α2 in equilibrium amounts to the liquid phase feed streams in question helps to reduce the rate of catalyst deactivation by preventing the potential polymerization of the pore-clogging polymerizable compounds formed in the process.

In addition, a controlled amount of water is preferably added to the alkylation reaction zone. In order to substantially prevent the loss of water from the catalyst and the consequent deterioration of the activity of the catalyst, an amount of water or water vapor, such as steam, is fed to the 2nd charge mainly to equilibrate the H 2 O vapor pressure of the catalyst. This amount of water ranges from about 0.01% to 6% by volume of the organic material fed to the alkylation reaction zone. The water is then typically removed with a stream of light by-products that is recovered in the first separation zone.

A substantial portion of the hydrocarbon used as the aromatic substrate and the entire olefin used as the alkylating agent reacts in the alkylation reaction zone in the presence of a solid phosphoric acid catalyst to form undesired polyoylated aromatic compounds in addition to the desired monoalkylated aromatic compound. Unwanted polyalkylated aromatic hydrocarbons typically contain two or more alkyl groups having 1 to 18 carbon atoms, for example, di-, tri-, and tetrasopropylbenzene hydrocarbons. Unwanted monoalkylated 13 "aromatic compounds typically contain alkyl groups having more or fewer carbon atoms than the alkyl compound of the desired monoalkylated aromatic product.

In addition, when the desired monoalkylated aromatic product is an alkylated aromatic compound having an unsaturated alkyl side chain, the undesired monoalkylated aromatic compound may also be a monoalkylated aromatic compound containing saturated alkyl side chains. having the same number of carbon atoms as the desired saturated t torn i sr.a alkyl side chains. An important feature of this invention is the recovery and transalkylation of dialkylated aromatic compounds to maximize the amount of desired monoalkylated aromatic hydrocarbons generated in the process while minimizing deactivation of the transalkylation catalyst.

The effluent from the alkylation reaction zone is directed in its entirety to the first separation zone. In the first separation zone, the stream leaving the alkylation reaction zone is separated into at least three fractions using available conventional separation methods to obtain substantially pure fractions: (1) an aromatic substrate, (2) compound. The fraction of the first separation zone containing compounds having a boiling point higher than the boiling point of the desired mono-alkylated aromatic compound is then passed to the second separation zone. In the second separation zone, a feed comprising compounds having a boiling point higher than the boiling point of the desired monoalkylated aromatic compound is separated using any available conventional separation technique to recover a fraction rich in dialkylated aromatics and fractions having a higher boiling point. compounds 14,,, -,.

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fraction.

The recovery and removal of the trialkylated aromatics and a higher boiling compounds the process in the second separation stage a fraction having a boiling point higher than the fraction rich dialkylated aromatic compounds boiling point, prior to introduction into the transalkylointireaktiovyöhykkeeseen, succeed in eliminating the potential transalkylointireaktiovyöhykkeen feed compounds, which could otherwise accelerate transalkyloin-polymerization catalysts deactivation. As mentioned above, an intermediate fraction containing components having boiling points lower than the boiling point of the fraction rich in dialkylated aromatic compounds is also recovered in the second separation zone. The components of the intermediate fraction are typically alkylated aromatic compounds having short saturated side chains, such as methylbenzene, ethylbenzene, butylbenzene, propylbenzene, and the like. By recovering and removing the aromatic compounds formed as intermediates from the process before feeding them to the transalkylation reaction zone, it is possible to reduce from the process the amount of compounds that could otherwise be converted in the transalkylation reaction zone into harmful products that could accumulate in the process. Such diluents are generally removed from the process as unwanted impurities or as part of an unusable drag stream of a desired intermediate component, such as an aromatic substrate drawing stream. Diluents should be removed from the process to prevent them from accumulating in the process. By removing most of the potential 1 diluents in the second separation zone, the process is improved because the purity of the desired product is improved and the drag flow rates are slowed down.

Examples of some separation methods that can be used alone or in one of the first and second separation zones to obtain substantially pure fractions from the above separation zone include: distillation, including 15 V '' '' vacuum distillation, at atmospheric pressure and at atmospheric pressure, above pressure processes, including, for example, liquid-liquid extractions, steam-liquid extractions, supercritical extractions, and the like, absorption methods, adsorption methods, and any other known mass transfer techniques to recover the desired first and second separation product products in substantially pure fractions. The above separation methods are examples of many techniques that could be used to perform the necessary separation, purification, and recovery of products from the alkylation and transalkylation reaction zones. Therefore, the operating conditions of the separation zone are not described here because they depend on the choice of the separation technique to be used and further on the configuration of the separation zone equipment. Continuous distillation is believed to be the primary separation method used in the separation zones. Again, the optimal distillation conditions depend on the exact procedure chosen to perform the desired separation.

As mentioned above, the product from the transalkylation reaction zone, as will be described below, is directed in its entirety to the first separation zone. In addition, part or all of the fresh aromatic substrate feed stream may be initially directed to the first separation zone. By directing the aromatic substrate feed to the first separation zone, it is possible to process aromatic substrate feeds which mainly comprise the desired aromatic substrate feed component, but which may contain harmful amounts of undesired components. By directing the aromatic substrate fed as feedstock to the first separation zone, a substantially pure aromatic substrate feed stream can be obtained as part of the feedstock or as the entire feedstock from both the alkylation reaction zone and the transalkylation reaction zone.

Repeat that the receivables from the first separation zone

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the fractions are substantially pure streams of the desired monoalkylated aromatic compound, unreacted aromatic substrate feed compound, and compounds having boiling points higher than the boiling point of the desired monoalkylated aromatic compound. In addition, in the first separation zone, a fraction of hydrocarbon materials having a lower molecular weight than the undesired products of the reactions of the aromatic substrate feed compound, the alkylation zone, and the transalkylation zone is separated from the process and recovered as the product of the first separation zone. Other undesirable by-product fractions that can be separated from the alkylation and transalkylation reaction products in the first separation zone are benzene draw stream and propylene oligomers. The second separation zone becomes a fraction rich in dialkylated aromatic compounds and fractions with boiling points higher and lower than the fraction rich in dialkylated aromatic compounds. The fraction from the second separation zone comprising hydrocarbons having boiling points lower than the fraction rich in dialkylated aromatic compounds normally comprises undesired saturated alkylated aromatic compounds, whereas said higher boiling aromatic compound typically has a high boiling aromatic fraction. Fractions comprising the desired monoalkylated aromatic product, light hydrocarbon-containing by-products, benzene effluent, propylene oligomers, and hydrocarbons having boiling points higher and lower than the desired fraction rich in dialkylated aromatics are taken from the process. The fraction comprising the aromatic feed substrate can be recycled partly to the alkylation reaction zone and partly to the transalkylation reaction zone. Normally about 25% to about 90% by weight and preferably about 30% to 85% by weight of the aromatic substrate fraction is transferred to the alkylation zone. The remainder of the aromatic substrate feed fraction and the entire dialkylated aromatic fraction are transferred f. j 17 to the transalkylation zone as a feed to the transalkylation zone.

The transalkylation reaction zone receives as feed the entire fraction rich in dialkylated aromatic compounds obtained from the second separation zone, and may receive as feed a portion of the aromatic substrate taken up in the separation zone. i f rakt iosta. The stream formed from the aromatic substrate feed not recovered in the separation zone but from an off-process source can be used as part of the aromatic substrate feed or as the entire aromatic substrate feed to be directed to the transalkylation reaction zone.

The dialkylated aromatic stream used as part of the material to be fed to the transalkylation reaction zone consists of aromatic compounds characterized as comprising a molecule based on an aromatic substrate with two olefinic acid compounds which take the place of two hydrogen atoms in the aromatic substrate. The dialkylated aromatic stream also contains small amounts of aromatic compounds having boiling points similar to those of a dialkylated aromatic compound such as hexylbenzene when it comes to making cumene.

The transalkylation reaction zone is used to remove more than one of the olefinic alkylating agent compounds from the ring structure of the dialkylated aromatic compounds and to transfer the removed alkylating agent compound to one of the aromatic substrate molecules not previously prepared, thus adding. To translate the aromatized compounds on an aromatic substrate, a feed mixture containing a molar ratio of an aromatic substrate to a dialkylated aromatic compound in the range of 1: 1 to 50: 1 and preferably 4: 1 to 10: 1.

fed continuously or intermittently transalkylation ii '> ak 18

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to a thio zone containing a transalkylation catalyst under transalkylation conditions. The transalkylation catalyst used in the transalkylation reaction zone of this invention is an acidic crystalline urinosilicate material bonded to a refractory inorganic oxide material.

The crystalline aluminosilicate material of the transalkylation catalyst of the present invention is a silica-alumina material having either a three-dimensional or channel-pore crystalline mesh size. type, ultrastabii1i Y-type and the like. L-type, omega-type and mordenite are examples of crystalline aluminosilicates with a channel pore structure.

The aluminosilicate material preferably used in the catalyst composition of this invention is a special form of aluminosilicate material known as mordenite. Although mordenite occurs in nature, various synthetic mordenites are also available as a commodity, usually in powder form. These synthetic mordenites can be obtained in both sodium and hydrogen forms and at various silica: alumina ratios. According to a preferred embodiment of the present invention, the mordenite is in the hydrogen form and the ratio of silica to alumina is at least 8: 1, more specifically in the range of 8: 1 to 25: 1.

The aluminosilicate in hydrogen form is coupled to a refractory inorganic oxide and formed into a catalyst composite compound. The formed catalyst composite can be prepared by any method known in the art, including well-known oil droplet and extrusion methods. The aluminosilicate in the hydrogen form may be present in an amount ranging from 5% to about 99.5% by weight, preferably from 60% to about 95% by weight, and the refractory inorganic oxide may be present in an amount ranging from ,,.

0.5% to about 95% by weight. The proven aluminosilicate can be modified by any method known in the art, either before, during or after preparation as a catalyst particle. Examples of potential modification methods include steam deactivation, ion exchange to reduce aluminosilicate to the hydrogen form, addition of metal 1 imodium waves or other chemical modifiers, pre-coking, and so on.

The most preferred inorganic oxide for use in the transalkylation catalyst of this invention is Alumina. The alumina is preferably selected from the group consisting of gamma alumina, eta alumina and mixtures thereof. Other refractory inorganic oxides that may be considered include silica gel, silica-alumina, magnesium-alumina, zirconia-alumina, aluminum phosphates, and the like.

It has been found that there is a strong correlation between the transalkylation performance of the catalyst composite compound of this invention and the surface area of said composite compound. In order to achieve the highest possible performance of the transalkylation catalyst, the catalyst composite compound formed should have the largest possible surface area. The area referred to herein is determined using Langmuir's method for determining correlates of adsorption / desorption isotherms. The Langmuir method is particularly suitable for catalyst composite compounds containing high percentages of crystalline aluminosilicates, while other calculation methods are used primarily to determine the areas of amorphous, less well-defined solids. The information required for the Langmuir method is obtained by well-known adsorption / desorption devices1, preferably by a nitrogen adsorption / desorption device11a.

Coating composites with a large surface area can be obtained in many ways, such as by using crystalline aluminosilicate powder, which already has a very large surface area of 20 ° C, or by using a component of the composite compound with a large surface area. compared to other components in large quantities.

In a continuous process comprising a partially transalkylation zone for transalkylation of dialkylated aromatic compounds with an aromatic substrate, the above-mentioned transalkylation reagents are fed in admixture to a pressure vessel containing the above-described crystalline aluminosilicate transalkylation catalysts. The transalkylating catalyst may be contained in one layer in one reactor vessel or may be divided into several layers in the same reactor. The alkylation reaction system may contain one or more reaction vessels in series. The feed to the transalkylation reaction zone can take place vertically upwards or downwards through the catalyst bed in a typical plug-flow reactor or horizontally across the catalyst bed in a radial flow type reactor.

Temperatures suitable for use in this process include temperatures that initiate a reaction between an aromatic substrate compound and dialkylated aromatic compounds recovered in the first and second separation zones to selectively produce the desired monoalkylated aromatic compound. In general, suitable temperatures for initiating transalkylation reactions are from about 100 ° C to about 390 ° C, and especially from about 125 ° C to about 275 ° C. Pressures suitable for use herein are preferably higher than about 1 atm, but should not be higher than about 130 atm. A particularly favorable pressure range is from about 10 atm to about 40 atm. The rate of liquid passing through the catalyst per hour (LHSV) is preferably -1 to about 0.1 to about 50 hours, and especially about 0.5 to about 5 hours, based on the combined feed rate of the aromatic substrate and dialkylated aromatic compounds. It should be noted that the combination of temperature and pressure used in the transalkylation reaction zone should be such that the transalkylation reactions occur substantially in the liquid phase. The liquid

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In the 21-phase transalkylation process to prepare alkylated aromatic compounds, the catalyst is continuously washed with reagents, thereby preventing the formation of carbon black precursors on the catalyst.

The use of only dialkyl aromatic polyalkylated components, as opposed to the use of di-, tri- and tetra-α1 aromatics as part of the feed to the transalkylation reactor, as well as the reaction in the liquid phase, helps to minimize the formation of carbon scaling during transalkylation. It is believed that if the trialkylated aromatic components and heavier aromatic components removed from the feed to the transalkylation reaction zone in the second separation zone of this invention catalyst activity. This accumulation of heavy compounds in the pores of the transalkylation catalyst would then lead to a loss of catalyst activity. Thus, using only dialkyyliaromaattisiä polyalkylated components as part of transalkylointireaktiovyöhykkeen input and acting transalkylointireaktiovyöhykkeessä the liquid phase of a coal formation to the surface of said catalyst unfavorable, whereby the catalyst life is prolonged in comparison with Priva-gas phase executable transalkylointiprosessiin and the liquid phase using transalkylointiprosesseihin with Transall-kyloidaan trialkylated aromatic compounds and heavier compounds wherein carbon scaling and catalyst deactivating turnstiles are a major problem.

It has been found that the catalyst of the transalkylation reaction zone described above can be regenerated by washing the deactivated transalkylation catalyst with hot liquid benzene. It has been found that the washing of the deactivated transalkylation catalyst with benzene takes place at temperatures of - 250 ° C and higher. At temperatures above 250 ° C, benzene has been found to be most effective in desorbing large aromatic molecules that clog and deactivate the catalyst pores of the transalkylation catalyst, thereby restoring the transalkylation catalyst to a substantially fresh catalyst activity state. It is expected that the desired aromatic substrate and aromatic components other than the desired aromatic substrate may be equally effective in regenerating the transalkylation catalyst by washing with hot liquid hydrocarbon. Benzene is mentioned herein as the most preferred hydrocarbon component because it is probably available in the process of this invention.

To facilitate an understanding of the present invention, reference is made to the figure, which is a flow chart of the method of the present invention. To clarify the explanation, it deals with the preparation of cumene from benzene and propylene. However, the description is not intended to limit the scope of the invention in any way. As mentioned above, the first step of the process of this invention comprises directing a mixed feed stream 4 to an alkylation catalyst-containing reaction zone 1 containing an alkylation catalyst, wherein the mixed feed stream 4 consists of an aromatic benzene substrate feed stream 3 and a propylene olefin alkylation

The first separation zone 6 enters the entire alkylation reaction zone effluent 5 and the entire transalkylation reaction zone effluent 20. In addition, some or all of the benzene aromatic substrate used as feed for the alkylation and transalkylation reaction zone The first separation zone 6 produces at least four product streams 8, 10, 11 and 12 and two silent streams 7 and 9. The products separated in the first separation zone f> are the desired aromatic monoalkylated cumene product stream 8, al- '·· _ t 23 oligomer stream 11, light paraffin by-product stream 12, and benzene-rich aromatic substrate-containing drag stream 10. The intermediate streams recovered in the first separation zone are the benzene-rich aromatic substrate stream 7, the first portion of which can be used for the alkylation reaction. in addition, the second part of the art-taken benzene-rich aromatic substrate stream 7 can be used as the benzene aromatic substrate feed to the transalkylation reaction zone via line 19. Components with boiling points higher than the desired cumene aromatic monoalkylated compound are recovered in the first separation zone 6 and directed entirely via line 9 to the second separation zone 14.

A flow 9 is fed to the second separation zone 14, which contains components having boiling points higher than the desired cumene-containing aromatic mono-alkylated component. The second separation zone produces at least two product streams, 16 and 17, and one intermediate stream 15. The product streams from the second separation zone 14 are an aromatic intermediate stream 16 consisting of hydrocarbons boiling below the desired diisopropylbenzene-rich dialkylated combined aromatic 15 and a product stream 17 comprising hydrocarbons having boiling points higher than a stream 15 containing a dialkylated aromatic compound rich in diisopropylbenzene. having a similar boiling point and being directed to the transalkylation reaction zone 18.

Dialkylated alkylbenzylated aromatic compounds 24 are fed to the transalkylation reaction zone 18 and recovered in the second separation zone 14 and fed to the transalkylation reaction zone 18 via stream 15. The aromatic substrate in benzene is also used as a feedstock to the transalkylation reaction zone 18. The aromatic substrate may be fed directly to zone 18 from some non-process source or may be obtained as part of the recycle flow of the aromatic substrate recovered in the first separation zone 6 via lines 7 and 19 or a mixture of the two.

Example 1

Catalyst A was prepared according to the best method for preparing the transalkylation catalyst used in this invention. The starting material for Catalyst A was a hydrogen-containing, low-sodium, partially dealuminized synthetic mordenite powder (sold by Union Carbide under the tradename LZ-M-8), hereinafter referred to as commercial mordenite.

The commercial mordenite powder was mixed with the alumina powder in a weight ratio of 9: 1, after which an acidified peptizing solution was added. This mixture was then prepared by an extrusion method using means known in the art. After extrusion, the extrusion product was dried and sintered.

After the drying and calcination steps, the extrusion product was washed in an aqueous solution containing 10% by weight of HCl and 10% by weight of NH 4 Cl at 50 ° C for 150 minutes dissolved in zeolite in a volume ratio of 5: 1. After the washing step, the catalyst was dried and recalculated. Catalyst A is a crystalline aluminosilicate catalyst of the transalkylation reaction zone of this invention. The surface area of this catalyst 2 thus obtained was 620 m / g.

The transalkylation catalyst A was tested in a pilot plant to determine the stability of the catalyst over time by processing the feedstock produced from the SPA alkylation catalyst. During the stability test, the deactivation of the transalkylation catalyst of this invention over time was compared to 25. Obtained by using a feedstock comprising diisopropylbenzene and benzene obtained by fractionating a heavy product from the alkylation reaction zone in another fractionation zone to give a substantially pure diisopropylbenzene feed when a feed stream was used in accordance with this invention. comprising diisopropylbenzene, benzene and heavier and lighter aromatic compounds, i.e. a heavy product obtained from the alkylation reaction zone. The pilot plant used to evaluate the catalytic stability of the transalkylation catalyst of this invention consisted of a tubular reactor with a 55 cm transalkylation catalyst connected to a product recovery zone. The reactor pressure was maintained at 34 atm, temperature 150 °

Crssa and the combined fluid flow rate per hour at 1.3 -1 h. A comparison of the effect of the fed transalkylation feedstock mixture on deactivation of the transaxle catalyst is shown in Table 1 below. Case I represents the results obtained for diisopropylbenzene-benzene feedstock 11a corresponding to the transalkylation reaction feedstock of the present invention when fed to the feedstock feed zone. II represents the results obtained using a raw material containing diisopropylbenzene and heavier and lighter aromatic compounds and benzene according to the prior art i.

26

table 1

Comparison of the effects of different transalkylation feedstocks - Case I

Case I Taj5aus_ 11

Raw material fed (% by weight)

Cumene 0.0 0.1

Butyl, pentylbenzenes 0.3 0.6 DIPB 20.0 21.1

Hexylbenzenes 4.8 6.0

Heavy aromatic compounds

Benzene 74.9 71.1

Total 100.0 100.0

Benzene / DIPB molar ratio 7.8 / 1 7.0 / 1

Flow hours 360 100 Output DIPB conversion 50% 35%

Final DIPB conversion 50% 28% DIPB conversion loss 0% 7% DIPB conversion loss rate 0% / 100 h 7% / 100 h

The above results show the remarkable effect of the composition of the feedstock on the deactivation rate of the transalkylation catalyst of the present invention. The rate of deactivation of the transalkylation catalyst of this invention using benzene and dipropylbenzene feed in case I is significantly slower than when using the same catalyst as feedstock containing heavy aromatic compounds in case II. As mentioned, the feedstock of Case I represents the feedstock to be fed to the transalkylation reaction zone from the second separation zone of the process of this invention. The feedstock in Case II represents the feedstock to be fed to the transalkylation reaction zone from an alkylation-transalkylation process that does not have a second separation zone. Thus, the use of a second separation zone to separate substantially all of the heavier aromatics and some of the light aromatics from the diisopropylbenzene-rich fraction fed to the transalkylation reaction zone clearly and dramatically improves the active use of the transalkylation catalyst.

Example 2 This example demonstrates the regenerability of the transalkylation catalyst of this invention. After 1200 hours of operation in a pilot plant under conditions similar to Example 1, Case I, about 30% conversion of diisopropylbenzene was observed in the transalkylation catalyst. This was well below the diisopropylbenzene conversion value of the fresh catalyst of 49-50%. The deactivated transalkylation catalyst was then regenerated by a hot benzene step. The step of regenerating the transalkylation catalyst with hot benzene was carried out: - by stopping the transalkylation reactor, - rinsing the reactor 11a with benzene and at a liquid flow rate of 1.3 h per hour for 12 hours, - raising the reactor temperature from 150 ° C to 250 ° C, then holding reactor at 250 ° C for 12 hours and maintaining the Bentene 1 throughput at a value corresponding to LHSV of 1.3 h "1, - by lowering the reactor temperature from 250 ° C to 150 ° C within 12 hours at a benzene throughput of 1.3 h 1, and - restarting the transalkylation reactor.

After the transalkylation catalyst regeneration procedure was completed and the reactor was restarted, the conversion of the transalkylation catalyst to diisopropylbenzene was improved to 51%. This example demonstrates the benefit of using a hot benzene wash step to restore the activity of a previously deactivated transceiver of this invention. This example also clearly demonstrates the regenerability of the acid washed transalkylation catalyst of this invention.

Claims (10)

29 A process for the preparation of monoalkylated aromatic compounds, characterized in that it comprises the steps of: (a) directing a feed stream (4) comprising an alkylating agent (2) and an aromatic substrate (3) to an alkylation reaction zone (1); containing a solid phosphoric acid cocatalyst and maintaining conditions such that alkylation of said aromatic substrate occurs in the liquid phase; (b) separating the product (5) obtained from the alkylation reaction zone (1) and the product (20) obtained from the transalkylation reaction zone described below in the first separation zone (6) into fractions comprising 1) a substantially aromatic substrate fraction (7), 2) a substantially pure product a fraction (8) and 3) a fraction (9) comprising compounds having boiling points higher than the desired monoalkylated aromatic product; (c) separating in the second separation zone (14) the higher boiling fraction (9) into a fraction rich in dialkylated aromatic compounds (15) and fractions having higher (17) and lower (16) boiling points than the fraction rich in dialkylated aromatic compounds (15); (d) feeding a feed stream comprising an aromatic substrate (19) and a separated hydrocarbon fraction (15) comprising richly dialkylated aromatic compounds to a transalkylation reaction zone (18) containing a crystalline aluminosilicate catalyst and maintaining conditions with said richly dialkylated the hydrocarbon fraction is transalkylated to give the product of the transalkylation reaction zone (20); and (e) feeding the product (20) of the transalkylation reaction zone from step (d) to the first separation zone (6). Process according to claim 1, characterized in that at least a first part of the fraction (7) comprising the aromatic substrate of step (b) is recycled to the alkylation reaction zone and at least a second part of the fraction (7) comprising the aromatic substrate of step (b) is recycled to the transalkylation reaction zone . Process according to Claim 1, characterized in that the alkylating agent is selected from an alkene, an alcohol, an alkyl halide, an alkyl sulphonate or a mixture thereof. Process according to Claim 1, characterized in that the alkylating agent is a monoolefin and has from 2 to 14 carbon atoms. Process according to Claim 1, characterized in that the transalkylation catalyst used in step (d) consists of 5 to 99% by weight of a crystalline aluminosilicate material, characterized in that it has a mean pore diameter of 6 angstroms or more. Process according to Claim 5, characterized in that the crystalline aluminosilicate material contained in the transalkylation catalyst is mordenite. Process according to Claim 4, characterized in that the monoolefin alkylating agent is ethylene or propylene. Process according to Claim 4, characterized in that the monoolefin alkylating agent comprises a C 9 -C 14 olefin. Process according to Claim 1, characterized in that the feed to the alkylation reaction zone is saturated with H 2. Process according to Claim 1, characterized in that the feed to the transalkylation reaction zone is saturated with H 2. 31 c: :::.