MXPA99002036A - Control of the training of diarilalcan subproducts in aromatic renting by olefins using zeolite catalysts b - Google Patents

Abstract

The amount of unwanted by-products of diarylalkane WH which form an alkylation reaction using a zeolite beta catalyst wherein a reacted aromatic reacts with an olefin is reduced by the use of an alkylaromatic diluent in an amount such that the proportion of phenyl group per The alkyl group corresponding to the olefin reagent entering the reactor is maintained within the range of 0.75: 1 a to 25: 1 and the concentration of the olefin entering the reaction is less than an amount calculated by dividing MWo by the sum of 6.17 MWA and MWu giving MWO is the molecular weight of the olefin, and MWAA is the molecular weight of the aromatic feed

Description

CONTROL OF THE TRAINING OF DIARILALCAN SUBPRODUCTS IN ION AROMATIC RENT BY OLEFINS USING CATALYZERS OF BETA ZEOLITE FIELD OF THE INVENTION This invention relates to a process for the production of aromatic compounds of onaalkyl by Iqui lation. Specifically, this invention relates to the highly selective alkylation of benzene by ethylene for the purpose of producing ethylbenzene using beta zeolite. BACKGROUND OF THE ART The alkylation of aromatic compounds with C2 to C4 olefins is a common reaction for the production of anoalkylaromatics. An example of this reaction that is practiced industrially is the alkylation of benzene with ethylene to produce ethylbenzene. As usual, several byproducts accompany this production of ethylbenzene. A simplified summary of the alkylation reaction and its product and common byproducts is presented below: EP DFB TED C H -C H 3 + other polyalkylated benzenes Heavy DPE Even though the formation of the byproducts of diethyl benzene ("DEB") and triethylbenzene ("TEB") can, at first glance, be considered as a reduction in the efficient use of the ethylene, in fact each of them can Easily transalute by benzene to produce ethylbenzene ("EB"), as shown below: The combination of alkylation and transalkylation can therefore optimize the production of ethylbenzene. A combination of this type can be carried out in a process having two reaction zones, one for alkylation and the other for transalkylation, or in a process having a unique reaction zone where both alkylation and transalkylation. In many cases, it is preferred to employ a single reaction zone and not two reaction zones due to savings in capital investment. In contrast to diethyl benzene and triethyl benzene, 1,1-diphenylethane (1,1-DPE) can not be converted to ethylene by alkylation, and therefore 1,1-DPE represents a reduction in the efficiency of the use of ethylene and ethylene loss. In fact, the production as a byproduct of i, l-DPE and heavy benzene palietylates other than diethylbenzene and triethylbenzene collectively referred to herein as heavy represents virtually all the reduction in ethylene utilization. Although the ideal ethylbenzene process would not form a byproduct of 1,1-DPE, the current minimum requirement is that the amount of 1,1-DPE formed should not exceed 1.0% by weight of the alkylation reactor effluent relative to ethylbenzene . The byproduct formation of 1,1-DPE is having an increasing importance taking into account the expectation in some areas of minimum standards regarding the 1,1-DPE content no greater than 0.5% by weight. It is useful to underline two key operation variables of the alkylation zones of ethylbenzene. The first key variable is the molar ratio between the phenyl groups per ethyl group, which is often referred to here as the phenyl / ethyl ratio. The numerator of this ratio is the number of moles of phenyl groups that pass through the alkylation zone during a specified period of time. The number of moles of phenyl groups is the sum of all phenyl groups, independently of the component in which the phenyl group is found. For example, one mole of benzene, one mole of ethylbenzene, and one mole of diethylbenzene each contribute one mole of phenyl group to the sum of the phenyl groups. The denominator of this relationship is the number of moles of ethyl groups that pass through the alkylation zone during the same specified period of time. The number of moles of ethyl groups is the sum of all the ethyl and ethenyl groups, independently of the compound in which the ethyl or ethenyl group is found. For example, one mole of ethylene and one mole of ethylbenzene each contribute one mole of ethyl group for the sum of ethyl groups, while one mole of diethylbenzene contributes two moles of ethyl groups. The second key variable is the effective concentration of ethylene that enters the alkylation zone. A practical mathematical approach is that the concentration of ethylene depends on the reciprocal of the molar ratio of phenyl groups per ethyl group according to the following formula: (ethylene) equals approximately (phenyla / ethyl ratio) -l Thus, the increase of the phenyla / ethyl ratio decreases the ethylene concentration. It is known that a low concentration of ethylene to a high molar ratio of phenyl groups per ethyl group minimizes the formation of byproduct of 1,1-DPE. The amount of 1, 1-DPE formed depends on the square of the reciprocal of the phenyl / ethyl ratio according to the following formula: (1,1-DPE) equals approximately (phenyl / ethyl) -2 ratio.

Thus, increasing the phenyla / ethyl ratio decreases the amount of i, i-DPE formed. Even when the decrease in 1,1-DPE formation is obtained by a small increase in the phenyl / eti ratio. it can be small, it is also very significant, resulting in a high phenyla / ethylate ratio as a condition of choice to minimize the formation of i, i-DPE. However, a high phenyl / ethyl ratio increases the capital and operating costs usually associated with the recovery of the excess benzene. These chaos give rise to the search for a procedure to obtain ethylbenzene that minimizes the formation of byproduct 1, 1-DPE at a phenylalanol ratio.

In the prior art, this search for a method for obtaining commercially viable ethylbenzene that only produces a small amount of 1, i-DPE but also operates with a low phenyla / ethyl ratio has not borne fruit. All prior art procedures follow the same well-known approach which consists in dividing the alkylation zone into an increasing number of catalyst beds and injecting decreasing portions of the total ethylene in each bed. When the permitted concentration of 1,1-DPE is relatively high, this approach undoubtedly provides certain benefits. For example, if benzene is alkylated with ethylene in a single bed alkylation carrot operating with a phenyle / ethyl molar reaction of 5, then the highest concentration of ethylene that occurs at the ethylene injection site is 16.77. malar Downstream of the ethylene injection point, the ethylene concentration decreases to very low concentrations as ethylene is consumed and as ethylbenzene is formed, while the phenyl / ethyl ratio remains essentially the same. However, if the single bed is divided into four beds in series and if a quarter of the required ethylene is injected into each bed, then the phenyle / ethyl ratio is 20 in the first bed, 10 in the second bed, 6.7 in the third bed, and 5 in the fourth bed. Therefore, the highest concentration of ethylene is 4.8 mol% in the first bed, 4.5 mol% in the second bed, and 4.3 mol% in the third bed, and 4.2 mol% in the fourth bed. Thus, the division of the bed and the division of the ethylene injection increase the phenyle / ethyl ratio and decrease the highest concentration of ethylene. But, with the aim of operating in the lower phenyla / ethylation ratios and to also achieve the low concentrations of 1,1-DPE that are expected to be the minimum standard in the near future, this prior art approach is not viable. For example, if benzene is alkylated with ethylene in a four-bed alkylation zone that operates with a global phenyla / ethyla molar ratio of 2 instead of 5 as in the previous example, then the phenyl / ethyl ratio is located within a range of S in the first bed to 2 in the fourth bed, and the highest concentration of ethylene is located within a range of 11.1% molar in the first bed to 8.3% molar in the fourth bed. Compared to the previous example, the concentration of ethylene in each bed approximately doubles, which would result in an unacceptable amount of formation of i, 1-DPE. In order to reduce the concentrations of ethylene to the concentrations indicated in the previous example, the number of beds should increase by 10, simply as a consequence of the fact that the overall phenyl / ethyl ratio decreased from 5 to Thus, in response to the industry's demand for lower phenyla / ethyl ratios and market demand in the sense of obtaining low byproduct concentrations of i, 1-DPE in the product stream, the process of the prior art inexorably divides the alkylation reaction carrot into a large number of very small catalyst beds. For various technical, economic and practical considerations, this inefficient solution of the prior art processes is unacceptable in the hydrocarbon processing industry.

SUMMARY OF THE INVENTION A method has been discovered that significantly reduces the formation of 1, 1-DPE by-product in the alkylation of benzene benzene using zeolite to beta in a low molar ratio of phenyl groups per ethyl group (phenyl / ethyl ratio) . It has also been found that this method can significantly reduce the formation of 1,1-DPE in the production of ethylbenzene by alkylation and transalkylation using zeolite beta in a low molar ratio of phenyl groups per ethyl group (phenyla / ethylate) "This invention may employ one or more components or portions of the effluent stream of the alkylation zone to dilute the ethylene concentration in the alkylation zone and thereby to decrease the byproduct formation of 1,1-DPE. This result using beta zeolite was surprising and could not be derived from the prior art which says that the formation of 1,1-DPE can be reduced only by increasing the phenyl / ethyl ratio to either increasing the number of catalyst beds. In addition, prior art processes employing Zealite Y produce more I, 1-DPE and deactivate more rapidly as a result of the use of the same diluent components and streams that provide benefits in this invention which employ beta zeolite. A process of alkylation of benzene by ethylene in a low concentration of ethylene shows a significant advantage in terms of selectivity compared to a process which operates with a high concentration of ethylene. Using this invention, the ethylbenzen processes can now minimize the formation of 1,1-DPE even when operating at low malar ratios of phenyl groups per ethyl group. With the problem of the formation of 1,1-DF'E now solved by this invention, the ethylbenzen processes can now operate more cost-effectively with a low malar ratio of phenyl groups per ethyl group. The underlying chemical reactions that would be considered responsible for the observed results is that in the alkylation of an aromatic by an olefin, when the concentration of an olefin decreases, a selective decrease in the reaction between the alefin and the alkylaromatic is observed. The products of this reaction are an aromatic alkenyl and a paraffin corresponding to the olefin. The alkenyl aromatic may in turn serve as an active alkylating agent and react with the aromatic to form the undesired by-product of diarylalkal. The consequence is that it can be expected that a decrease in the olefin concentration will generally give benefits in terms of alkylation of aromatics with olefins. Applying this hypothesis to the IO alkylation of benzene with ethylene, the apparent anomalous formation of 1,1-DPE probably results from the following reactions: C2H5 CH - CH2 + CH2 - CH + C2K6 When a catalyst is employed, it is believed that ethylbenzene and styrene are released into the catalyst and that hydrogen transfer occurs from ethylbenzene to ethylene. In any case, a decrease in ethylene concentration provides a decrease in styrene formation and, in turn, the formation of i, 1-DPE. This invention minimizes the formation of 1,1-DPE by using a diluent in the combined feed to the alkylation reaction zone to prevent the ethylene concentration from reaching the high ethylene concentrations present in prior art processes. It is generally known that in the prior art processes the concentration of ethylene in the reaction zone decreases from a relatively high concentration to the entry point when the ethylene is introduced to an II. relatively low concentration at the outlet when almost all the ethylene has been consumed. Thus, even in prior art processes, low ethylene concentrations can be observed, especially near the exit of the reaction zone. However, it has been found that even high-density ethylene localized tracians that occur in the prior art processes at the ethylene injection site produce unacceptably high concentrations of 1,1-DPE. Thus, it is now recognized that a diluent can avoid localized high ethylene concentrations and minimize the formation of 1,1 ~ DPE. In addition, it has been recognized that some diluents are preferred to other diluents and that a selective choice of this diluent can decrease not only the malar ratio of phenyl groups per ethyl group but also the formation of other desirable byproducts in addition to 1,1-DPE. This chemical explanation explains the formation of other diarylalkanes that correspond to other olefins that rent other aromatics. For example, in the alkylation of benzene with prapilene to produce eumeno, the corresponding diarylalkanne would probably be 2,2-diphenylpropane (2,2-DPP). Although the formation of 1,1 ~ DPP is also possible, it is believed that the formation of 2,2-DPP is more likely due to the isamerization of the rump prapil.

It is a broad object of the present invention to improve the selectivity and decrease the chalks of the processes for the alkylation of aromatics with olefins. It is another broad object of the invention to improve the selectivity and decrease the process rates for the alkylation of aromatics with olefins and the transalkylation of aromatics with laromatic pal ialqui. It is a specific object of this invention to minimize the formation of 1,1-diphenylethane (1,1-DPE) in the alkylation processes that produce ethylbenzene. It is another specific object of this invention to decrease the costs associated with the operation of alkylation procedures by decreasing the molar ratio of phenyl groups to alkyl groups under the alkylation conditions. In a broad embodiment, this invention is a process for producing a monoalkylaramático. An aromatic feed, an olefin, and a diluent comprising at least one phenyl group and at the ore an alkyl group corresponding to the olefin are passed to an alkylation zone. The aromatic feed and the alefin react in the alkylation zone in the the presence of a beta zeolite catalyst to alkylate the aromatic with the alefin to form a monoalkylaromatic. The reaction conditions that inhibit the formation of the by-product of diarylalkane are a molar ratio of phenyl groups per alkyl group corresponding to the alefin from 0.75.1 to 25: 1 and an olefin concentration, based on the weight of the aromatic fed , define it, and the diluent passed to the alkylation zone, less than MWa ^ • £ that 6.17 x MWA + MWa where MWa is the molecular weight of the olefin and MWA is the molecular weight of the aromatic. In a more specific embodiment, this invention is a process for the production of ethylbenzene. Benzene, ethylene and a diluent comprising at least one phenyl group and at the ore an ethylene rump pass to an alkylation rod. The benzene and the ethylene react in the alkylation carrot in the presence of a zeolite beta catalyst under reaction conditions sufficient to alkylate the benzene with ethylene to form ethylbenzene. The reaction conditions which inhibit the formation of the unwanted byproduct 1,1-diphenylethane are a molar ratio of phenyl groups for ethyl groups of 1: 1 to 6: 1 and an ethylene concentration of less than 5.5% by weight based on the weight of benzene, ethylene and dilLtyente that will pass to the alquilación carrot. A product comprising ethylbenzene and the diluent is removed from the alkylation zone. The product contains less than 1.0% by weight of 1, 1-diphenylethane in relation to ethylbenzene. The diluent is separated from the product and recycled to the alkylation zone. In another more specific embodiment, this invention is a process for the production of ethylbenzene. The ethylene, an inlet stream comprising benzene, and a recycle stream containing a diluent combine to form a combined stream, and the combined stream passes to a reaction zone. The reaction carrot contains a catalyst comprising beta zealite and operates under conditions sufficient to alkylate benzene with ethylene. The reaction conditions which inhibit the formation of undesired 1, i-diphenylethane are a malar ratio of phenyl groups per ethyl group of 1: 1 to 6: 1 and an ethylene concentration of less than 5.5% by weight based on the weight of the combined stream. An effluent stream comprising benzene, ethylbenzene, a diethylbenzene and a heavy laramatic polyalkylene is recovered from the reaction rod. The effluent stream contains 1.0% by weight of 1, 1-diphenylethane relative to ethylbenzene. At least part of the effluent stream passes to a separation zone where the effluent stream is separated. the separation zone: a low boiling fraction comprising benzene, a product stream comprising ethylbenzene, and a high boiling fraction that captures diethylbenzene and heavy polyalquilarate. The product stream is recovered from the process. A portion of the input stream is provided from at least a portion of the low boiling fraction. The recycle stream is formed from a portion of the effluent stream or at least a portion of the high boiler fraction. In another embodiment, this invention is a process for the production of a monoalkylaromatic aromatic. A fed aromatic, an olefin, and an aromatic of parylkylane that camps at the ore a phenyl group and at least two additional alkyl groups corresponding to the alefin of the aromatic feed pass to a reaction zone. In the reaction zone, the aromatic feed is alkylated with the olefin and the aromatic is transalkylated with the aromatic of palialkylation in the presence of beta zeolite to form a monaalkyl aromatic. The conditions of the by-product inhibition reaction include a molar ratio of alkyl phenyl groups of alkyl from 0.75: 1 to 25: 1 and a concentration, based on the weight of the aromatic feed, the define, and the polyalkyl aromatic which passes to the reaction zone, the olefin smaller than MWa s% -in weight 6.17 x MWA • + • MWa where MWa is the molecular weight of the olefin and MWA is the molecular weight of the aromatic. These reaction conditions inhibit the diarylalkane formation corresponding to the olefin. DETAILED DESCRIPTION OF THE INVENTION This invention can generally be applied to the alkylation of an alkylation substrate with an alkylation agent in the presence of a diluent. This invention applies more specifically to the alkylation of an aromatic with an olefin. Although benzene is the main aromatic of interest, aromatics such as alkyl substituted benzenes, generally fused ring systems, and alkylated derivatives thereof may be employed. Examples of aromatics of this type san toluene, ethylbenzene, propylbenzene, etc.; xylene, estylene, methylethylbenzene, etc. naphthalene, anthracene, phenanthrene, methylnaphthalene, dimethyl Inaf alene, and tetralin. It can be used more than an aromatic. Olefins containing from 2 to 6 carbon atoms are the main alkylation agents contemplated in this invention. Examples of olefins of this type include ethylene, propylene, butene-1, cis-butene-2, trans-butene-2, and iso-butene. However, olefins having from 2 to 20 carbon atoms can be used efficiently in this invention. It can be used more than one alefina.

The most widely practiced hydrocarbon conversion process to which the present invention can be applied is the catalytic alkylation of benzene with ethylene for the purpose of producing ethylbenzene. Accordingly, for purposes of simplification, the discussion of the present invention will largely refer to part to its application to a catalytic ethylbenzene reaction system. The diluent can be any compound capable of mixing with the alkylating agent (eg, ethylene) and decreasing the concentration of the alkylating agent downstream of the injection site of the alkylating agent. It is not necessary that the diluent is inert. In practice, however, the diluent must have several characteristics consistent with the objective of the process of producing high yields of high purity product. First, the diluent should decrease the molar ratio of phenyl groups to ethyl groups in the reaction stem. Benzene, although adequate, is not preferred due to the high recovery and recycling cost of benzene. Second, the diluent should not adversely affect the yield of ethylbenzene. Toluene and eumeno are not preferred because ethylene can rent toluene or eumeno and produce by-products that can not be easily converted to ethylbenzene by is alkylation a. good transalkylation. Ethylbenzene is also not preferred because ethylbenzene can change the balance of the alkylation reaction of ethylbenzene formation and park ethylbenzene can react with ethylene to produce styrene and finally l, i-DPE. Third, the diluent should not adversely affect the purity of ethylbenzene. Accordingly, xylenes are not preferred because they are relatively difficult to separate from ethylbenzene by distillation. Another reason for which xylenes are preferred is that they can negatively affect the yield of ethylbenzene for alkylation with ethylene. A fourth characteristic of the diluent, apart from its effect on minimizing the formation of 1,1-DPE, is that the diluent should increase the yield of ethylbenzene. Helium, neon, argon, or otherwise inert materials are preferred because they can not react to form ethylbenzene. On the other hand, a diluent reactive to either a transalkylating agent such as palleti Ibencena coma dieti Ibenceno, triethylbenzene, etc. , until hexaethylbenzene, is preferred because each can be transalkylated in ethylbenzene, regardless of whether each is alkylated by ethylene. Due to the possibility of alkylation of palilethylbenzene by ethylene, however, the lighter Ibencene polytests are more preferred than the heavier pallets and benzenes, being especially preferred in diethylbenzene. When the aromatic is benzene and the olefin is ethylene, the diluent can generally be an alkylbenzene having at least one C2 to C4 alkyl group. Said alkanols include ethylbenzene, a diethylbenzene, triethylbenzene, butylbenzene, dibutylbenzene, tributylbenzene, ethylbutylbenzene, diethylbenzene benzene, and a good diphenylethane. According to the particular aromatic and olefin, however, the diluent may be an alkylated derivative of benzene, naphthalene, anthracene, and tetralin. Reaction conditions that inhibit the formation of the undesired diphenylalanne byproduct include a molar ratio of fepila groups per alkyl group from 25: 1 to 0.75. In this invention, the successful operation in a low molar ratio of phenyl groups per ethyl group, for example, less than 6: 1, is achieved by introducing the diluent into the reaction stem in such a way that the concentration of ethylene remains less than 5.5% by weight. In contrast, in prior art processes for the alkylation of benzene can ethylene, if the molar ratio of phenyl groups to ethyl group is 6.17, then ethylene constitutes 5.5% by weight of the total weight of hydrocarbons, that is, benzene and ethylene, which passes to the alkylation reaction zone. In the general case for alkylating agents other than ethylene and alkylation substrates other than benzene, an exaggerated operation in accordance with this invention at a low molar ratio of phenyl groups per alkyl group is achieved by introducing the diluent into the the reaction in such a way that the concentration, based on the weight of the alkylating agent, diluent alkylating substance passing to the alkylation zone, in percent by weight of alkylation agent remains lower than that calculated by the following formula: MWAA, % by weight 6.17 x MS + MWAA where MWAA is the molecular weight of the alkylating agent (eg, alephine) and MWAS is the molecular weight of the alkylation substrate (exemplary pair, benzene). In general, for a given malar ratio of alkylation substrate per alkylation agent, the higher the molar ratio of phenyl groups to alkyl groups in the feed stream, the lower the rise in temperature in the reaction zone that occurs as a result of the alkylation reactions. The alkylation reactions have a heat of reaction of 233 to 349 J / kmol (100-150 BTU / lb-mol) and are considered moderately exothermic. Even though some ethylbenzene reactors have indirect jig swapping devices to remove the jig as it occurs, most of the ethylbenzene reactors are adiabatic, and therefore the outlet temperature of the effluent stream is higher than the outlet temperature. entry of reactants. An increase in the molar ratio between phenyl groups and alkyl groups in the feed roller increases the quality of the phenyl groups available to act as a heat sink in the reaction zone and consequently decreases the temperature rise in the area of the reaction. reaction. Thus, in practicing the invention, the inlet temperature in the reaction zone is typically 200 to 260 ° C (392 to 500 ° F) and preferably 230 to 250 ° C (446 to 482 ° F). Even though the temperature rise that occurs in the reaction zone could be 10 to 190 ° C (18 to 342 ° F) depending on the total mass flowing in the reactor, the temperature rise is generally 5 at 50 ° C (9 to 90 ° F), and preferably 5 to 20 ° C (9 to 36 ° F). In general, for all reagents presented here, the appropriate reaction temperature is generally 100 ° C (2i2 ° F) up to the critical alkylation substrate temperature, which can be 475 ° C (887 ° F) to even higher .

The temperature rise in the reaction zone can be controlled by adjusting the molar ratio between phenyl groups and ethyl groups in the feed stream. The fact of minimizing the temperature rise helps to avoid high output reactor temperatures that cause undesirable side effects such as the decomposition of hydrocarbons. High reaction temperatures may also cause vaporization of benzene and ethylene in the reaction zone. In one embodiment of this invention, the elevation of the temperature in the reaction stem can be controlled by removing an effluent stream from the reaction stem, cooling a portion of the effluent stream, and recycling the cooled portion of the reaction stream. effluent stream to the reaction zone. Although recycling the reactor effluent to the reaction stem in this way may be disadvantageous for some reaction zones, it is not disadvantageous for this invention because the recycling of reactor effluent to the reaction zone does not significantly alter the distribution of products when the catalyst is a beta zeolite. A significant alteration in the distribution of the product is a change in the concentration of any of the products in the reactor effluent stream of more than 0.5% by weight »A significant alteration in the product distribution does not occur park in the reaction conditions , beta zealite is such an active promoter of the alkylation reaction between benzene and ethylene that the magnitude of the reaction comprises at least 80% and generally more than 90% of what is necessary to reach a steady state. Thus, the recycling of reactor effluent to the reaction zone does not interfere significantly with the magnitude of the alkylation reaction, and the recycling of reactant effluent can be used for the purpose of controlling the temperatures in the reaction zone. . The alkylation is carried out in the liquid phase. Therefore, the reaction pressure must be sufficiently high to ensure at least a partial liquid phase. When ethylene is the alefin, the range of pressures for the alkylation reaction is usually 1379 to 6985 kPa (g) (from 200 1000 psig), more usually from 2069 to 4137 kPa (g), and even more commonly from 3103 at 4137 kPa (g). Preferably, the reaction conditions are sufficient to anticipate benzene in a liquid phase and supercritical conditions for ethylene. For olefins other than ethylene, this invention may be practiced generally at a pressure of 345 to 6985 kPa (g) (50 to I000 psig). The space velocity per hour by weight of ethylene can be located within a range of 0.01 to 2.0 hr-1. The space velocity per hour in aromatics, including benzene and an aromatic diluent having at least one C2 + group, is generally from 0.3 to 480 hr-i. In a preferred embodiment, wherein the diluent is diethylbenzene or trieti Ibencena, the molar ratio between benzene and ethylene is from 2: 1 to 6: 1, the space velocity per hour by weight of ethylene is from 0.1 to 1.0 ht-1, and the space velocity per hour in weight of the aromatics, including benzene, and the diluent is from 0.5 to 19 hr-1. The main reaction that occurs in the reaction zone is the alkylation of benzene by ethylene to produce ethylbenzene. In addition, other reactions may occur in the area of the reaction. For example, the diluent may be alkaline with ethylene or with ethylbenzene, or the diluent may be cross-linked with ethylene to ethylbenzene, or the diluent may be transalkylated with benzene to either ethylbenzene. By-product reactions are reduced by the practice of this invention, the reactor effluent stream usually contains the by-products of these other reactions. Accordingly, a portion of the reactor effluent stream can be employed without any downstream separation and a stream for supplying diluent to the area of the alkylation reaction. Alternatively, the reactor effluent stream can be passed to a separation zone from which it can be recovered fi re bed containing one or several components that are suitable diluents, and this fraction can in turn be passed to the zone of alkylation reaction »The reactor effluent stream contains ethylbenzene and may also contain unreacted diluent, a by-product of a collateral alkylation reaction including the diluent, or a by-product of the transalkylation side reaction including the diluent. The reactant effluent carrier may also contain unreacted benzene as well as a by-product of a collateral alkylation reaction that includes benzene or a by-product of a transalkylation side reaction including benzene. In addition, the reactor effluent carrier may contain unreacted ethylene, but the concentration of unreacted ethylene will likely be non-significant because the benzene is usually present at least in a stoichiometric ratio. Although it is not often that the feed stream contains paraffins Cl to C3 in addition to ethylene, if the ethane is present in the feed carriage, then the reactor effluent stream may also contain unreacted ethane. The reactor effluent stream passes to a separation zone, which generally comprises a benzen fraction column with the object of recycling the unreacted benzene to the alkylation rod, and an ethylbenzene fractionation column in order to recover the ethyl benzene eat product from the heavier palladium-benzenes. A fractionation column of palylalkyl benzene can also be used to separate the diethyl benzenes and triethylbenzenes from the other heavier polyalkylbenzenes, particularly when the alkylbenzene which is present in the feed stream is a diethylbenzene or a trieti 1 benzene. The separation zone generally comprises a removal of ethane unless the concentrations of ethylene, ethane or unreacted light C3 paraffins in the reactor effluent reach a sufficiently high level to justify their separation from the reactor effluent stream. The beta zeolite is presented in the documents US-A-330869, US-A-4891458 and US-A-5081323? and in document US-A-5522984 a vaporized beta zealite with ammonium exchange is presented. A preferred beta zeolite for use in the present invention is a modified surface-modified beta zeolite resulting from washing with a native zeolite beta with a standard. That is, the formation of the surface modified beta zeolite begins with a beta zeolite with a standard where the standard is, for example, a tetraalkylamide salt, such as a tetraethylammonium salt. It is critical to wash a zeolite beta with an acid pattern in order to protect the internal sites of the zealite and avoid a dealumination. The standard beta zealite is treated with a strong acid at a pH between 0 and 2, even though a pH lower than i is preferred. The acids that can be used include nitric acid, sulfuric acid, phosphoric acid, etc. For example, a weak 0.01 molar nitric acid can be used in combination with ammonium nitrate to carry out the acid wash, even though substantially higher concentrations, up to 20% by weight of nitric acid, are preferred. Nitric acid is a preferred acid that is an acid that does not form complexes and therefore encourages the dealumination. The treatment of the zealite beta with standard with strong acid can be carried out in the temperature range between 20 ° C and 125 ° C. It is important that the acid wash be carried out under such severe conditions as to achieve a dealumination. The time during which the acid wash is carried out to prepare the preferred zealite depends on the temperature. It is critical for the formation of the beta zeolite with surface modification that there is no significant dealumination of the zeolite »As a general statement, it can be said that the acid wash should be carried out during an insufficient time to achieve the dealumination. For example, using nitric acid 0.01 malar and 40% ammonium nitrate at a temperature of 70 ° C, it will be found that contact times of 2-3 hours are adequate to modify the surface aluminum environment without causing significant dealumination. Using 15% nitric acid with ammonium nitrate to treat a 25% paste at a temperature of 85 ° C, a 90 minute treatment is effective. The pattern is removed by calcination at temperatures within a range of 550 -700 * 0 The calcination conditions are well known in the art and it is not necessary to dwell on this subject. It is also necessary to mention that the zeolite powder itself is usually used as an alkylation catalyst. Accordingly, in the most usual case, after acid washing of the standard beta zealite, said zealite is washed with a conventional agglomerator, extruded, and the extruded part is ulceratedly calcined. But the clinical portion of the preparation of the preferred zeolite is the acid washing of the beta with standard according to the above description. The acid wash of a calcined beta zealite (ie, with a standard) does not offer the modified surface material of the preferred zealite. It has been found that, after the treatment described above, the surface aluminum atoms exhibit a chemical modification. It has been hypothesized that the modification is in the form of replacement of strong acid sites on the catalyst surface by weaker acid sites. What has been definitively observed in te is that the surface aluminum atoms of the preferred modified beta-zeolite have 2p binding energy in accordance with the edited pair of electro-voltaic fataelectron x-ray spectroscopy at 74.8 electron volts. See US-A-5723710 for additional details. EXAMPLES Catalyst A is a fresh alkylation catalyst comprising beta zealite made in accordance with the teachings of document US-3308069. A sample of catalyst A was used to produce ethylbenzene by alkylation of the benzene with ethylene under alkylation conditions in which heavy alkylaromatics were occluded at the surface and within the internal spacing of the Catalyst A sample. After having been used for alkylation, the sample of Catalyst A exhibited a content of heavy occluded cyclaratiles of 5% by weight relative to the weight of the catalyst. While in contact with the air, the sample of Catalyst A having heavy alkylaromatics occluded was heated from room temperature to 650 * 0 (1202 ° F) for a period of three hours, maintained at a temperature of 650 ° C for three hours. hours, and then it was cooled to room temperature. The sample of Catalyst A after cooling is known in these Examples as a. ? X X_.C? Ot_í £ 5 * Catalyst C is a fresh alkylation catalyst comprising elastated beta zealite in accordance with US-3308069. Catalyst D is a fresh alkylation catalyst comprising 80% by weight of zeolite Y "ul traestabilizado" and 20% by weight of alumina binder. In Examples 1-9 below, the net reactor effluent stream is the total reactor effluent stream minus the portion, if any, of the total reactor effluent stream recycled to the reactor. Efficiency is defined in relation to ethylene and is calculated by subtracting the weight of ethylene in the net reactor effluent stream to the weight of the ethylene in the ethylene fed to the reactor divided by the weight of ethylene in the net reactor effluent stream, multiplied per 100. The selectivity of 1,1-DPE is defined as the concentration in weight percentage of 1,1-DPE in the net reactor effluent stream, calculated based on the net reactor effluent stream free of benzene and light compounds. In general, the performance of a compound is defined as the conversion product and selectivity of this compound, divided by 100. However, the yield of ethylbenzene has a special definition insoas it is defined as co or the sum of the yields Individuals of ethylbenzene, diethylbenzene and Ibencena trieti. This calculation of the ethylene yield represents the total yield of ethylbenzene that would be produced if all of the diethylbenzene and the triethylbenzene in the product stream were transalked to ethylbenzene in a transalkylation rod, and subsequently recovered. In addition, in Examples 1-9, the benzene liquid hourly space velocity (LHSV) is calculated using only the constituent benzene and not including benzene in the portion, if any, of the reactor effluent stream. total recycled to the catalyst bed. Also, since the molar ratio between phenyl groups and ethyl group (or per propyl group) is essentially the same in the current fed to the total reactor and in the total reactor effluent stream, the molar ratio between phenyl groups and grupo etila (a por prapils group) is not significantly affected by the recycling of a part of the total reactant effluent stream. In Examples 1-7, the catalyst comes into contact with a combined feed stream containing fresh benzene, fresh ethylene, a recycled acrylic acid portion of the reactor effluent stream (in Examples 1, 3, 5, 6 and 7). only), and dieti Ibencena fresco (in example 6 only). When a portion of the reactor effluent stream is recycled to the reactor, the weight ratio of the recycled portion of the stream to the reactor is 3. reactor effluent for the fresh benzene weight and fresh ethylene was 2.0. The concentration of ethylene in the combined feed is more than 5.5% by weight in Examples 2, 4 and 5, which are the control examples. I aul? Effect of ethylene concentration on the formation of 1,1-DPE in several molar proportions of phenyl groups per ethyl group using beta zeolite catalysts Example 1 2 3 4 Catalyst B B B B Phenyl / ethyl, mol / mol 5.21 5.25 4.09 4.27 Temp. maximum, ° C 241.9 Ten KO? -I "Te p. Elevation, ° C 15.9 33.3 20.9 34.7 Pressure, Pa 3.89 3.89 3.89 3.89 Benzene LHSV, hf-1 3.9 4 * X1 _» »_) T_>» T_> Effluent recycling / 2.0 0 2.0 0 fresh feed, weight / weight Ethylene concentration 2.15 6.4 2.79 7.75 in combined feed% in weight EB yield,% in 99.82 99.79 99.83 Q ™ jr "" weight Selectivity of 1.1- DPE, 886 928 895 1230 wppm 1,1-DPE / EB in effluent of .101 .105 105 143 reactor (% by weight /% by weight) x 100 Ethylene efficiency, 99.9 99.9 99.9 99.9% by weight Ex em la 5 6 7 Catalyst B A A Phenyl / eti lo, mol / mol 1.81 4.54 4.55 Te. maximum, ° C 242 242 Elevation of temp. , "C 24.1 _-_ *. ^ 25.5, Pressure, mPa 3.89 x- n 3.89 Benzene LHSV, hr-1 1.3 3.9 2.9 Recycling effluent / 2.0 2.0 2.0 fresh feed, weight / weight Concentration of ethylene at 5 e > '7 1.88 2.44 combined feed,% by weight EB return,% by weight 98.24 99.49 99.38 Selectivity of i, l-DPE, wppm 11180 2900 3100 1,1-DPE / EB in effluent of 1.74.357.348 reactor (% by weight /% by weight) x 100 Ethylene efficiency,% by 99.5 99.8 99.8 weight A comparison of Examples i and 2 shows the effect of recycling a part of the reactor effluent stream to the reactor with the object of increasing the ethylene concentration in the alkylated carrier to almost the same malar ratio between phenyl groups for the ethyl group (5"2i and 5.25). The recycling of a part of the effluent stream in example i increases the yield of ethylbenzene, decreases the selectivity of i, l ~ DPE and decreases the ratio between i, i-DPE and ethylbenzene in the effluent stream. A comparison of examples 3 and 4 shows the effect of recycling a portion of the reactor effluent stream to the reactor with the object of decreasing the ethylene concentration in the feed fed at molar ratios of phenyl groups by ethyl group (4.09 and 4.27) which are smaller than in the plas and 2 axes. The recycling of a part of the reactor effluent stream in the 3-post increases the yield of ethylbenzene, decreases the selectivity of 1,1-DPE, and decreases the ratio of 1, 1-DPE to ethylbenzene in the effluent stream, even though the molar ratio of phenyl groups to ethyl group is lower in example 3 than in example 4. Example 5 shows the effect of recycling a portion from the reactor effluent stream to the reactor at a lower molar ratio of phenyl groups to the ethyl group as in examples ai 4, but without decreasing the ethylene concentration in the fed stream. While the concentration of ethylene in the feed stream is relatively high at 5.52% by weight, then even though the molar ratio of phenyl groups to ethyl group is 1.81: 1, the yield of ethylbenzene is lower, the selectivity of 1.1 - DPE is higher, and the ratio of il-DPE for ethylbenzene in the effluent stream is higher than in examples ia 4. In example 6, fresh diethylbenzene passed to the reactor with the purpose of simulating the recycling effect of diethylbenzene . The fresh diethylbenzene constituted 4.5% by weight of the weight of the fresh benzenate, fresh ethylene, and fresh diethylbenzene that passed to the reactor. The mole ratio of phenyl groups per ethyl group of 4.54 takes into account the phenyl and ethyl groups of fresh diethylbenzene. A comparison of examples 6 and 7 shows the effect of the introduction of diethylbenzene to the reactor while a portion of the stream of recycle is recycled. effluent to the reactor in almost the same molar proportions of phenyl groups per ethyl group. The interruption of diethylbenzene increases the yield of ethylbenzene and decreases the selectivity of 1, 1-DPE. In examples 8 and 9, the catalyst is contacted with a combined feed stream containing fresh benzene, fresh propylene, and a recycled aliquot portion of the reactor effluent stream. The ratio between the weight of the recycled portion of the reactor effluent stream by the weight of fresh benzene and fresh propylene was i.5 in Example 8 and 1.75 in Example 9 »The position of the maximum temperature (due to the exothermic reaction) in the bed of catalyst was noticed. The deactivation ended up observing the position of the maximum temperature after a suitable time interval (for example 48 hours) under the test conditions. Deactivation is calculated by measuring the difference of these two positions (in inches), dividing by the length of the bed (in inches), and then dividing by the time interval (in days). The results are multiplied by 100% to provide a deactivation rate in catalyst bed percentage / day. Table 2 Effect of reactor effluent recycling on catalyst deactivation rate in the same phenol / propyl ratio using beta zeolite catalyst Example 8 9 Catalyst 0 C Feni / Propyl, mol / mol 4 4 Maximum temperature, ° C 180 180 Elevation at temperature ° C 25 23 Pressure, mPa 3.55 3.85 Benzene LHSV, hr ~ l 4 4 Effluent recycling / feeding 1.5 1.75 fresh, weight / weight Propylene concentration in 4.7 4.3 combined feeding,% by weight Deactivation rate, "/./day 3.45 2.86 A comparison of examples 8 and 9 shows that increasing the recycle ratio of the effluent stream to the catalyst bed in the same molar ratio of phenyl groups per propyl group decreases the rate of catalyst deactivation. Even though those data showing a decrease in deactivation speed were obtained when catalyst C was used to alkylate benzene with propylene, it is believed that a similar decrease in catalyst deactivation rate would be observed if catalyst C were used to rent Benzen with ethylene. Examples 10 and 11 provide examples of control employing a zeolite Y in which the catalyst comes into contact with a combined stream comprising fresh benzene, fresh ethylene, and a portion of recycled aliquot of the reactor effluent stream (in the 10-axis shaft). In Example 10, the ratio between the weight of the recycled portion of the reactor effluent carrier 58 and the weight of fresh benzene was 3. The deactivation rates were determined by the calculation method described above for examples 8 and 9. Table 3 Effect of reactor effluent recycling on the formation of 1,1-DPE and on the deactivation viscosity of catalyst in the same phenyla / ethyl ratio employing a zeolite Y catalyst Example 10 11 DD catalyst Phenyl / Ethyl, mol / mol 5.0 5.0 Maximum temperature, "C 240 240 Pressure, psi (g) 550 550 Ethylene LHSV, hr-1 0.3 0.3 Recycling effluent / fresh benzene 0 w / w i, DPE / EB in reactor effluent, 7 2.45 (".in weight / 7, in weight)? 100 Speed of deactivation,". day * > "ñ 1.7 A comparison of examples 10 and 11 shows that the increase in the recycle rate of the effluent carrier to the catalyst bed in the same molar ratio of phenyl groups to the ethyl group increases the ratio of 1, 1-DPE by ethylbenzene in the effluent stream and increases the rate of catalyst deactivation.So, in contrast to the zeolite beta, the performance of the zeolite Y will begin as a result of recycling the reactant effluent.

Claims (9)

1. CLAIMS 1.
2. A process for the production of monoalkylaratatic, comprising: a) passing a fed aromatic, an olefin, and a diluent comprising at least one phenyl group and at least one additional alkyl group corresponding to said olefin said aromatic fed to an alkylation carrot; b) reacting said aromatic feed and said alefin in said alkylation zone in the presence of beta zeolite to alkylate said aromatic fed with said alefin to form a monoalkylaromatic; c) inhibiting the formation of by-product of diarylalkane which scavenges said olefin by operating said alkylation carriage under reaction conditions comprising a molar ratio between phenyl groups and alkyl group corresponding to said olefin from 0.75: 1 to 25: 1 and a concentration of said olefin, based on the weight of said aromatic feed, said olefin, and said diluent that pass to said alkylation zone in step (a), greater than MWo f "^ by weight 6.17 x MWA + MWa where MWo is the molecular weight of said alefin and MWA is the molecular weight of said aromatic feed, and d) removing from said alkylation zone a product comprising said mannoalkylaramático The process of claim 1 further characterized by said reaction conditions comprising a temperature from 100 ° C to 475 ° C and a sufficient pressure to keep said aromatic fed in at least a partial liquid phase
3. 3. The process of claims 2 The said diluent is selected from the group consisting of alkylated benzene derivatives, alkylated naphthalene derivatives, alkylated anthracene derivatives and alkylated tetralin derivatives.
4. 4. The process of claim 1 or 2 wherein said fed aromatic is selected within the rump consisting of benzene, naphthalene, anthracene, tetralin, and alkylated derivatives thereof.
5. The process of claims 1 or 2 wherein said alefin has from 2 to 20 carbon atoms.
6. 6. The process of claim 1 or 2 wherein said alefin is ethylene, said aromatic feed is benzene, said monoalkylaromatic is ethylbenzene, said byproduct of diarylalkane is i, 1-dif-n-ylethane, and said diluent is dieti 1 benzen »7» The process of claims 1 or 2 of said alefin is prapilena, said aromatic fed is benzene, said latheal manoalqui is eumeno, said byproduct of 4:
7. diarylalkan is 2,2-difeni Iprapane and said diluent is diprapyl benzene,
8. 8 The process of claim 1 or 2 wherein said beta zealite comprises a surface-modified, patterned, zeolite beta-free zeolite, characterized in that it has aluminum bond energies 2p surface area "as measured by photaelectrics x-ray spectroscopy, from at least 74.8 electron-valios.
9. 9. The process of claims 1 or 2 further characterized in that said olefin is ethylene, said aromatic fed is benzene, said monoalqui laromatic is ethylbenzene, said byproduct of diarylalkane is 1,1-diphenylethane, and said diluent is selected from the group that consists of ethyl benzene, diethylbenzene, triethylbenzene, tetraethylbenzene, ethylbutylbenzene, or diethyl butyl benzene.