CA2028935C - Aromatic conversion processes and catalysts useful therein - Google Patents

Abstract

Aromatic conversion processes and catalysts useful therein and their preparation including alkylation and trans-alkylation processes involving alkylation of an aromatic sub-strate with a C2-C4 alkylating agent with recovery of a mono-alkylated aromatic product and liquid phase transalkylation of a polyalkylated product. Specifically, a benzene feedstock is supplied to an alkylation zone operated under liquid or vapor phase conditions with the output supplied to the transalkylation zone operated under lower temperature liquid phase conditions.
In aromatic conversion processes over molecular sieve catalysts such as zeolite Y or beta under liquid phase conditions, an aro-matic feedstock containing water is passed to a dehydration zone to provide a dehydrated feedstock of a water content of no more than 100 ppm, preferably 50 ppm or less. A specific molecular sieve catalyst comprises hydrogen zeolite beta of high surface area and low sodium content. The modified zeolite beta has a surface area of at least 600 m2/g and a sodium content of less than 0.04 wt.% Na2O. The modified zeolite beta is prepared from as-synthesized zeolite beta by sequential ion exchange treatments with intermediate calcination at a temperature of 400°-700°C for a period of two hours or longer.

Description

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AROMA'PIC CONVERSION PROCESSES

FIELD OF THE INVENTION
This invention relates to aromatic conversion processes including alkylation and transalkylation processes involving aro-matic compounds including zeolite catalysts useful in such pro-cesses and more particularly to alkylation-transalkylation pro-cesses involving alkylation of a benzene feedstock with a C2-C4 alkylating agent and liquid phase transalkylation of resulting polyalkylbenzenes, treatment of the alkylation product in a separation zone, and recycle of at least a portion of the trans-alkylation product to the separation zone.

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BACKGROUND OF THE INVENTION
Molecular sieves and their use in aromatic conversion processes are well known in the chemical processing and refining industry. Aromatic conversion reactions of considerable commer-cial importance include the alkylatic>n of aromatic compounds such as in the production of ethyltoluene, xylene, ethylbenzene, cu-mene, or higher alkyl aromatics and in disproportionation reac-tions such as toluene disproportionation, xylene isomerization, or the transalkylation of polyalkylbenzenes to monoalkylbenzenes.
Such alkylation, transalkylation or other aromatic conversion processes may be carried out in the liquid phase, in the vapor phase, or under conditions in which both liquid and vapor phases exist.
An example of vapor phase alkylation is found in U.S.
Patent No. 4,107,224 to Dwyer. Here, vapor phase ethylation of benzene over a zeolite catalyst is accomplished in a down flow reactor, The output from the reactor is passed to a separation system in which ethylbenzene product is recovered, with the re-cycle of polyethylbenzenes to the alkylation reactor where they undergo transalkylation reactions with benzene. The Dwyer cata-lysts are characterized in terms of those having a constraint index within the approximate range of 1 to 12 and include, with the constraint index in parenthesis, ZSM-5 (8.3), ZSM-11 (8.7), ZSM-12 (2>, ZSM-35 (4.5), ZSM-38 (2), and similar materials.
Various molecular sieves, including, inter alia, zeolite beta (constraint index 0.6), are disclosed as having constraint indi-....
ces outside of the range suitable for the Dwyer ethylbenzene pro-duction process.
U.S. Patent No. 3,551,510 to Pollitzer et al. discloses an alkylation-transalkylation process in which the output from the alkylation reaction zone is passed directly to the trans-alkylation zone. In Pollitzar, alkylation is carried out using an alkylating agent, characterized as an olefin acting compound, over a solid phosphoric acid alkylation catalyst. The olefin acting compound may be selected from materials such as monoole-fins, diolefins, polyolefins, actylenic hydrocarbons, alkyl hali-des, alcohols, ethers and esters. The output from the alkylation reaction zone, which includes polyethylbenzenes, is supplied to a transalkylation reaction zone along with an aromatic substrate, e.g., benzene. The transalkylation zone contains an acid ex-tracted crystalline aluminosilicate catalyst, specifically mor-denite, and is operated in an upflow mode. Exemplary transalkyl-ation conditions include a liquid hourly space velocity of 1.0, a pressure of 500 psig and a temperature of 250°C. The output from the transalkylation zone is supplied to a separation zone from which a polyalkylaromatic, e.g., polyethylbenzene, is withdrawn and recycled to the alkylation zone.
Another alkylation-transalkylation process is disclosed in U.S. Patent No. 4,008,90 to Ward. Ward, like the patent to Pollitzer, discloses the use of a solid phosphoric acid catalyst in the alkylation zone. In Ward, benzene is reacted with propy-lene to produce curnene. The output from the alkylation reactor is split so that a portion principally benzene and cumene, is re--cycled to the alkylation reactor. Another portion containing principally benzene, cumene, propane and di- and tri- isopro-pylbenzene is supplied to a separation zone. In the separation zone a di- and tri-isopropylbenzene :rich stream is separated and supplied along with benzene to a transalkylation zone which con-tains a solid phosphoric acid catalyst. A cumene rich effluent from the transalkylation zone is recycled to the separation zone.
U.S. Patent No. 4,169,111 to Wight discloses an alkyla-tion-transalkylation process for the manufacture of ethylbenzene employing crystalline aluminosilicates in the alkylation and transalkylation reactors. The catalysts in the alkylation and transalkylation reactors may be the same or different and include low sodium content zeolites, preferably less than 0.5 weight per-cent Na20, having silica/alumina mole ratios between 2 and 80 and preferably between 4-12, Exemplary zeolites include molecular sieves of the X, Y, L, B, ZSM-5 and omega crystal types with steam stabilized Y zeolite containing about 0.2$ Na20 being pre-(erred. The alkylation reactor is operated in a downflow mode and under temperature and pressure conditions in which some liquid phase is present. The transalkylation reactor, which is described as generally requiring higher temperatures than the optimum temperature for alkylation in order to achieve maximum transalkylation efficiency, is also operai~ed in a downflow mode.
In Wight, the output from the alkylation reactor is cooled and supplied to a benzene column from which benzene is recycled to the alkylation rea<aor. The bottoms fraction from the benzene column is supplied to an ethylbenzene column from which ethylben-...

zene is recovered as the process product. The bottoms product from the ethylbenzene column is supp:l.ied to a third column which is operated to provide a substantially pure diethylbenzene over-heads fraction which contains from 10 to 90$, preferably 20 to 60~ of the total diethylbenzene feed to the column. The diethyl-benzene overheads fraction is recycled to the alkylation reactor while a side cut containing the remaining diethylbenzene and tri-ethylbenzene and higher molecular weight compounds is supplied to the transalkylation reactor along with benzene. The effluent from the transalkylation reactor is recycled to the benzene column.
U.S. Patent No. 4,774,377 to Barger et al. discloses an alkylation/transalkylation process which, like the above-described Wight process, involves the use of separate alkylation and transalkylation reaction zones, with recycle of the trans-alkylated product to an intermediate separation zone. In the Barger process, the temperature and pressure conditions are ad-justed so that the alkylation and transalkylation reactions takE
place in essentially the liquid phase. The transalkylation cata-lyst is an aluminosilicate molecular sieve including X-type, Y-type, ultrastable-Y, L-type, omega type and mordenite type zeo-lites with the latter being preferred. The catalyst employed in the alkylation reaction zone is a solid phosphoric acid contain-ing material. Aluminosilicate alkylation catalysts may also be employed and water varying from 0.01 to 6 volume percent is supplied to the alkylation reaction zone. The output from the alkylation reaction zone is supplied to first and second separa-...

tion zones. Water is recovered in the first separation zone. In the second reaction zone intermediate aromatic products and tri-alkylaromatic and heavier products are separated to provide an input to the transalkylation reaction zone having only dialkyl aromatic components, or diethylbenzene in the case of an ethyl-benzene manufacturing procedure or diisopropylbenzene in the case of cumene production. A benzene substrate is also supplied to the transalkylation zone for the transalkylation reaction and the output from the transalkylation zone is recycled to the first separation zone. The alkylation and transalkylation zones may be operated in downflow, upflow, or horizontal flow configurations.
As noted previously, various zeolitic molecular sieves are known for use in alkylation and/or transalkylation proce-dures. As indicated in the aforementioned U.S. Patent No.
4,107,224 to Dwyer, certain molecular sieves, including zeolite beta, are characterized as being unsuitable for use in the pro-duction of relatively low molecular weight alkylbenzenes such as ethylbenzene. In contrast to the relatively low molecular weight alkylbenzenes disclosed in the Dwyer et al. patent, U.S. Patent No. 4,301,316 to Young, discloses the use of molecular sieves to produce relatively high molecular weight alkylbenzenes which may be used as precursors for alkyl aryl sulfonate detergents. In Young, relatively long chain length alkylating agents having one or more reactive alkyl groups of at least 5 carbon atoms are em-ployed in the alkylation of benzene in the presence of a crystalline zeolite alkylation catalyst. The reactants may be in the vapor phase or the liguid phase and the zeolite catalysts may -7- .....
be modified or unmodified. Preferred zeolite catalysts include zeolite beta, ZSM-4, ZSM-20, ZSM-38, and synthetic and naturally occurring isotypes thereof such as zeolite omega and others. As described in Young, the zeolites may be subject to various chemi-cal treatments including alumina extraction and combination with one or more metal components such as the metals of groups IIB, III, IV, VI, VIIA, and VIII. The zeolites may also be subjected to thermal treatments including steaming or calcination in air, hydrogen or an inert gas. Specifically disclosed is the reaction of benzene and 1-dodecene over zeolite beta (Si02/A1203 = 175) in a flow reactor at 250°C and 600 psig.
LJ.S. Patent No. 4,185,040 to Ward et al. discloses an alkylation process employing a molecular sieve catalyst of low sodium content which is said to be esgecially useful in the pro-duction of ethylbenzene from benzene and ethylene and cumene from benzene and propylene. The Na20 content of the zeolite should be less than 0.7 weight percent and preferably less than 0.5 weight percent. Examples of suitable zeolites include molecular sieves of the X, Y, i~, B, ZSM-5, and omega crystal types, with steam stabilized hydrogen Y zeolite being preferred. Specifically dis-closed is a steam stabilized ammonium Y zeolite containing about 0.2$ Na20. The alkylation process may be carried out with either upward or downward :Flow, the latter being preferred, and prefer-ably under temperature and pressure conditions so that at least some liquid phase is present, at least until substantially all of the olefin alkylating agent is consumed. Ward et al. states that rapid catalyst deactivation occurs under most alkylating con-~_. ~~~J~~'~~
_8-ditions when no liquid phase is present.
Another alkylation procedure is disclosed in European Patent Application No. 272,830 to Ratcliffe et al. The Ratcliffe procedure employs molecular sieve alkylation catalysts which have been treated in a manner to improve selectivity to monoalkyla-tion, specifically in the propylation of.benzene to produce cu-mene. Selectivity is said to be increased by at least one percentage point by first depositing a carbonaceous material on the catalyst and then subjecting the resultant carbon containing catalyst particles to combustion. Specific zeolitic crystalline molecular sieves include those selected from the group of Y
zeolites, fluorided Y zeolites, X zeolites, zeolite beta, zeolite L, and zeolite omega. The zeolites may be modified to arrive at products of reduced alumina content and reduced sodium content.
A preferred zeolite is Y zeolite produced by first ammonium ex-changing to a sodium content of about 0.6-5.0 wt.~, expressed as Na20, calcining at a temperature of about 315°-900°C in the pre-sence of steam, and then ammonium exchanging the steam-calcined zeolite to obtain a product having less than 1.0 weight percent and preferably less than about 0.2 weight percent sodium, ex-pressed as Na20.
Zeolite beta referred to in certain of the references addressed previously is a crystalline aluminosilicate molecular sieve zeolite which finds application in a number of industrial processes including as a catalyst in various hydrocarbon conver-sion reactions such as hydrocracking, hydroisomerization and de-waxing. Zeolite beta, like many other molecular sieve zeolites, ...
_g_ is synthesized by the hydrothermal digestion of a reaction mix-ture comprising silica, alumina, an alkali alkaline earth metal and an organic templating agent. ThE~ organic agent acts as a template in the nucleation and growth of the zeolite beta crystals. Once the crystals are formed, it is conventional prac-tice to carry out a calcination treatment in order to remove the organic material from the interstitial channels of the molecular sieve network.
Crystalline zeolite beta, which is identified by its x-ray diffraction pattern, and basic procedures for its preparation are disclosed in U.S. Patent No. 3,308,069 to Wadlinger et al.
The chemical composition of zeolite beta in the as synthesized form as disclosed in the patent to Wadlinger et al. may be characterized as follows:
CX m (1.0 1-x) TEAJ A102 ~ ySi02 ' WH20 wherein: X is less than 1, m is at least one cation, usually an alkali metal or alkaline earth metal, more specifically sodium, n is the valence of m, y is from about 5 to 100, W is about 4, and TEA represents the tetraethylammonium ion.
As described in Wac'tlinger et al., zeolite beta may be formed from a mixture in water of tetraethylammonium hydroxide and suitable sources of sodium monoxide (or hydroxide), alumina, and silica.
Typical reaction mixture compositions, in terms of mole ratios, fall within the following ranges:

_lo_ Si02/A1203 - from about ZO to about 200;
Na20/tetraethylammonium hydroxide (TEAOH) - from about 0-0.1;
TEAOH/Si02 - from about 0.1--1.0;
H20/TEAOH - from about 20 to about 75.
The resulting reaction mixture can be heated at a temperature of about 75° to about 200°C until crystallization of the molecular sieve occurs. The crystallized product can be separated from the reaction mixture by filtration or centrifuging and then washed with water and dried to remove water from the molecular sieve network. The product can then be calcined in air or in an inert atmosphere in order to remove the templating agent as described above.
The Wadling:r patent discloses that the catalytic mater-ials can be prepared by calcining the original sodium form of the zeolite beta and/or replacing the major portion of the sodium ions with other metallic or ammoniacal ions. Specifically dis-closed in Wadlinger (Example 2) is a composition containing after calcination in air at 55°C, 0.7 mole percent Na20. Disclosed in Example 8 is a product formed by treating a dried product which was exchanged continuously fox 48 hours with 2~ solution of ammo-nium chloride. After washing free of excess chlorine ions, the catalyst was dried and calcined for 3 hours at 1000°F to produce an acid beta aluminosilicate having 0.07$ Na content.
Various other procedures are known for the synthesis of zeolite beta. European Patent Application 159,846 by Rubin, discloses the synthesis of zeolite beta having a silica/alumina mole ratio of up to 300 employing a templating agent formed by the combination of dimethylbenzylamine and benzyl halide. The hydrothermal digestion procedure in which the crystals are formed is carried out at a temperature below 175°C in order to avoid the formation of undesirable side effects. The zeolite beta produced in accordance with the Rubin application, when employed either as an absorbent or a catalyst, can be at least partially dehydrated by heating at a temperature of about 200°-600°C in an air or nitrogen atmosphere for about 1-48 hours. The inorganic rations of freshly synthesized zeolite beta can be decomposed by heating to a temperature up to about 550°C for 1-48 hours. Zeolite beta prepared in accordance with the Rubin process can have the origi-nal rations associated therewith replaced by a wide variety of other rations including hydrogen, ammonium and metal rations and mixtures thereof.
European Patent Application 165,208 by Bruce et al., discloses a procedure for the preparation of zeolite beta simi-lar to that disclosed in the aforementioned Rubin application ex-cept that the templating agent is a dibenzyl dimethyl ammonium halide or hydroxide with the silica/alumina components employed to provide a silica/alumina mole ratio in the synthesized product of about 20-250.
U.S. Patent x,642,226 to Calvert et al. discloses a pro-cess for the preparation of zeolite beta which is similar to those disclosed in the aforementioned European patent applica-tions and which employs dibenzyl dimethylammonium hydroxide or ....

chloride as a templating agent. The reaction mixture in Calvert is heated at a temperature of about 80° to about 175°C for about 1 to about 120 days. The Calvert patent states that the zeolite beta can be used in either the organic nitrogen-containing an alkali metal containing form, the alkali metal form and hydrogen form or another univalent or multivalent cationic form. Calvert also discloses that zeolite beta can be used in intimate combina-tion with a metallic component, e.g., a hydrogenation component such as tungsten, vanadium, molybdenum, rhenium, nickel, cobalt, chromium, manganese, or a noble metal such as platinum or palla-dium. The patent further states that the zeolite beta should be at least partially dehydrated when employed either as an absor-bent or as a catalyst or as a hydrocarbon conversion catalyst.
Chlorides, nitrates, and sulfates are disclosed as ion exchange agents. Calvert et al. discloses zeolite beta of relatively low sodium content, e.g., 0.14 wt.~ Na and 0.11 wt.~ Na.
Another process for the preparation of zeolite beta is disclosed in European Patent Application 164,939 by Calvert. The synthesis procedures disclosed here are similar to those in the above-mentioned references, except that a tetraethylammonium bro-mide or hydroxide templating agent is employed to produce a par-tially crystalline product of extremely high silica/alumina ratio which is said to be less expensive than fully crystalline zeolite beta which is dealuminized to provide a corresponding silica/
alumina mole ratio. The digestion period in this procedure is for a period of about 1-7 days at a temperature of 90°-200°C.
The silica/alumina ratio of the zeolite beta produced here ranges 2,~~~~~~:~~

from 20-1000 and is preferably greater than 200.
European Application 186,447 by Kennedy et al., disclo-ses the use of zeolite beta in catalytic cracking processes. The zeolite beta may be used in the as-synthesized form following calcination and be of either low or high silica/alumina activi-ties, It may be synthesized with trivalent framework ions other than aluminum to form, for example, borosilicates, boroaluminosi-licates, gallosilicates, or galloaluminosilicates structural iso-types, which are considered to constitute forms of zeolite beta. .
The zeolite beta may be acid extracted to form the high silica/
alumina products.
As noted previously, various aromatic conversion pro-cesses may be carried out in either or both of the liquid and vapor phases. At the relatively high temperatures involved in vapor phase reactions, it is generally accepted that water pre-sent in the feed stream is detrimental to the reaction process.
While various reasons are advanced for the adverse impact of water, the most widely observed detrimental effect is probably catalyst deactivation due to dealumination. For example, U.S.
Patent I~o. 4,197,214 to Chen et al. discloses a process fox modifying various crystallined zeolite molecular sieves such as ZSM-5, ZSM-11, ZSM-:L2, ZSM-35, ZSM-38, faujasite, mordenite, and erionite by the inclusion of metallic ions such as zinc. Chen et al. state that high temperature steam functions by way of a hydrolysis reaction to cause loss of framework aluminum which is accompanied by the :Loss of the associated protons, leading to a reduction in catalytic activity. The hydrolysis reaction is said ,..

to be quite slow at temperatures below about 800°F. However, at higher temperatures above 900°F, the reaction rate is sufficient-ly fast to affect long term stability of the zeolite catalyst.
In some cases, water can be tolerated under the high temperature conditions involved in vapor phase reactions. For example, the aforementioned patent to Dwyer states that water and hydrogen sulfide are tolerable if more rapid aging of the cata-lyst is acceptable, but are moderately detrimental in the pro-cess. Steam stabilized zeolites are disclosed as useful in aro-matic conversion processes involving alkylation such as in the production of ethylbenzene or cumene. Thus, the aforementioned patent to Ward et al. discloses that steam stabilized hydrogen Y
zeolite is preferred in the alkylation of benzene to produce ethylbenzene or cumene.
The use of steam stabilized zeolites in the production of high molecular weight alkyl benzenes is disclosed in the aforementioned patent to Young in which relatively high molecular weight alkylating agents are used in either the vapor phase or the liquid phase. The zeolite catalyst may be subjected to modifying treatments involving steaming for periods ranging from about one quarter to about 100 hours in an atmosphere containing from about 5 to about 100 steam.
In hydrocarbon conversion processes involving olefin conversion, water m;ay or may not be tolerated in the feed,stream, depending on the nature of the molecular sieve employed. For ex-ample, LI.S. Patent No. 4,551,438 to Miller discloses the oligo--merization of olefins over molecular sieves such as ZSM-5, ZSM-11 s '1 -ls-and silicalite characterized as intermediate pore size having an effective pore aperture in the range of about 5 to 6.5 angstroms.
Miller discloses that the feed should contain less than 100 ppm and preferably less than 10 ppm water, as well as being low in sulfur and nitrogen. On the other hand, when employing a some-what larger pore size molecular sieve, specifically steam stabi-lized zeolite Y in the conversion of C2-C4 olefins to motor fuels, water is described as an effective cofeed which stabilizes the catalyst and reduced the deactivation rate. As also describ-ed in U.S. Patent No. 4,740,648 to Rabo et al., co-fed water is described as a particularly desirable diluent which tends to aid in resistance of zeolite Y catalyst to coking and aging.

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SUMMARY OF THE INVENTION
In accordance with the present invention there is pro-vided an alkylation-transalkylation process involving alkylation of an aromatic substrate with a C2-C4 alkylating agent coupled with separation to recover a monoalkylated aromatic product and liquid phase transalkylation of a polyalkylated product. In one aspect of the invention, both the alkylation and transalkylation reactions are carried out in the liquid phase over molecular sieve aromatic alkylation and transalkylation catalysts. The output from the alkylation reaction zone is supplied to a separa-tion zone which is operated to produce a lower boiling fraction comprising the aromatic substrate, which may be recycled to the alkylation reaction zone, and a higher boiling fraction compris-ing a mixture of monoalkylated and polyalkylated aromatics. The higher boiling fraction is supplied to a second lower boiling fraction comprising the desired monoalkylated product and a high-er boiling fraction comprising polyalkylated product.
At least a portion of the polyalkylated fraction includ-ing substantially all dialkylated and trialkylated aromatics is supplied, along with the aromatic substrate, to a transalkylation reaction zone containing a molecular sieve transalkylation cata-lyst. The transalkylation zone is operated under liquid phase conditions to cause disproportionation of the polyalkylated frac-tion to arrive at a disproportionation product having a reduced polyalkylated aromatic content and an enhanced monoalkylated aro-matic content. At least a portion of the disproportionation pro-~~~u.~r.~.~
_1~_ duct is supplied to the first separation zone, In a specific application of the invention directed to the production of ethyl-benzene or cumene, the output from the transalkylation zone is supplied to a third separation zone from which benzene and a monoalkyl benzene fraction (ethylbenzene or cumene) is recovered and recycled to the separation zone.
In another embodiment of the invention, a benzene feed-stock and a C2-C4 alkylating agent are supplied to an alkylation reaction zone containing a molecular sieve alkylation catalyst and which is operated to produce an alkylated product comprising a mixture of monoalkyl and polyalkyl benzenes. In this embodi-ment of the invention, the alkylation zone may be operated under liquid phase or vapor phase conditions with the output from the alkylation zone being subjected to separation steps as described above. The transalkylation reaction zone is operated at an average temperature below the average temperature of the alkyla-tion reaction zone and under conditions to maintain the benzene in the liquid phase. In a specific application of this embodi-, ment of the invention to a procedure employing vapor phase ethy-lation of benzene followed by liquid phase transalkylation, the average temperature of the transalkylation reaction zone is at least 100°C less than the average temperature of the alkylation reaction zone. ' In yet a further aspect of the invention involving the alkylation of a benzene feedstock with a C2-C4 alkylating agent, the alkylation catalyst is selected from the group consisting of zeolite beta, zeolite omega, and zeolite Y and the alkylation re-actor is operated under conditions to maintain the benzene feed-stock in the liquid phase, as described previously. The effluent from the alkylation reactor is subjected to separation steps along the lines described above and :subsequent to separation to recover the desired monoalkylbenzene product, e.g., ethylbenzene or cumene, at least a portion of the polyalkylbenzene fraction including substantially all of the dialkylbenzene content and a predominant portion of the trialkylbenzene content is supplied to the transalkylation zone containing a transalkylation catalyst selected from the group consisting of zeolite Y, zeolite beta and zeolite omega. Preferably, the alkylation catalyst comprises zeolite beta and the transalkylation catalyst zeolite beta or zeolite Y.
In a further embodiment of the invention directed speci-fically to the production of ethylbenzene, in which the alkyla-tion reaction takes place over a zeolite beta alkylation catalyst. The output from the alkylation reaction zone is supplied to a benzene separation zone. A higher boiling traction comprising an ethylbenzene polyethylbenzene mixture is supplied from the benzene separation zone to wn ethylbenzene separation zone. This zone is operated to produce lower boiling product fraction comprising ethylbenzene and a higher boiling fraction comprising polyethylbenzene containing no more than 5 wt.~
ethylbenzene. The polyethylbenzene fraction is supplied along with benzene to a transalkylation reaction zone which preferably contains a zeolite Y transalkylation catalyst.
In accordance with a further aspect of the invention _19_ there is provided a modified molecular sieve comprising hydrogen zeolite beta of high surface area and low content of sodium or other alkali metal which is of a good activity and aging quality when used as a catalyst in hydrocarbon conversion reactions.
Also provided in accordance with the invention is a process of producing such modified zeolite beta and a process for the alky-lation of aromatic substrates with relatively low molecular weight alkylating agents under moderate temperature conditions including liquid phase conditions employing an alkylation cata-lyst comprising zeolite beta as described herein. A preferred embodiment of the present invention is in the alkylation of ben-zene with ethylene to produce ethylbenzene carried out in the liquid phase and at alkylation condi~ions under which the xylene make, based upon the amount of ethylbenzene produced, is no more than 0.03 wt.~.
In another embodiment of the invention, liquid phase alkylation process is carried out using a plurality of series connected reaction stages operated at an average temperature of no more than 300°C with the interstage injection of the C2-C~
alkylating agent in a manner to maintain at least 1 mole percent and preferably at least 2 mole percent of alkylating agent solu-bilized in the aromatic substrate.
In one aspect of the present invention, the modified zeolite beta has a surface area based upon the crystalline struc-ture of the zeolite beta of at least 600 m2/g and preferably at least 650 m2/g. A further aspect of the invention provides a molecular sieve in which the hydrogen zeolite beta is in combina-~? f i tion with a binder and in which the surface area of the zeolite beta, based upon the molecular sieve and the binder, is at least 450 m2/g.
In yet a further aspect of the invention, there is pro-vided a hydrogen zeolite beta having a sodium content in the crystalline structure of the zeolite beta of less than 0.04 wt.~
Na20. Preferably, the sodium content is less than 0.02 wt.~
Na20.
Another embodiment of the present invention involves a process for the preparation of a hydrogen zeolite beta derived by modification of an alkali metal containing zeolite beta synthe-sized by the hydrothermal digestion of a reaction mixture con-taining an organic templating agent. The synthesized zeolite beta may be produced by any suitable technique, such as described in Wadlinger et al. or Calvert et al. or the European patent applications. In carrying out the process, the synthesized zeolite beta is treated with an ion exchange medium in order to protonate at least a portion if the active sites of the zeolite.
by exchanging off alkali metal ions. The ion exchange zeolite is then calcined at a temperature within the range of 400°-700° for a period of at least two hours, preferably within the range of 2-10 hours. The calcined zeolite beta is again treated with an ion exchange medium to protonate an additional portion of the active sites by exchanging off additional alkali metal ions. The ion exchanged zeolite from this step is mixed with a binder to produce a mulled zeolite-binder mixture. This mixture is pelle--tized by extrusion or any other suitable technique and the re-a sulting pellets are then dried.
In a preferred embodiment of the invention, the ion ex-change treatment steps are accomplished by repeated submersions of the zeolite beta in an ion exchange: medium comprising an aqueous solution of ammonium salt. In a further aspect of the invention, the intermediate calcination step between the ion ex-change treatment steps is carried out under time and temperature conditions sufficient to arrive at a surface area based upon the crystalline structure of the zeolite beta which has at least twice the surface area of the zeolite beta in the as synthesized form.
In a further embodiment of the invention, there is pro-vided a liquid phase aromatic conversion process employing a zeolite molecular sieve catalyst having a pore size greater than 6.5 angstroms in which a feedstock containing at least one aroma-tic compound and having water entrained therein is passed to a dehydration zone. In the dehydration zone, water is removed to provide a dehydrated feedstock of a water content no more than 100 ppm, preferably 50 ppm, or less. The dehydrated feedstock is then supplied to the reaction zone containing the molecular sieve catalyst which preferably is selected from the group consisting of zeolite Y and zeolite beta. The reaction zone is operated at temperature and pressure conditions to maintain the reactor con-tents in the liquid phase and also sufficient to cause the con-version reaction to proceed in the presence of the catalyst.
One embodiment of the invention involves the liquid phase alkylation of an aromatic substrate, specifically the ethy-?~~~~~

lation of benzene to produce ethylbenzene with the dehydration of the feedstock to reduce the water content to no more than 100 ppm, as described above. A further aspect of the invention in-volves the transalkylation of a feedstock containing a mixture of a polyalkylbenzene component and a benzene component to produce a disproportionation product comprising a monoalkylbenzene. At least a portion of the feed to the transalkylation reaction zone is dehydrated to provide a feedstock, including both the poly-alkylbenzene and the benzene components, having a total water content of no more than 100 ppm.
Another embodiment of the present invention involves a process for the liquid phase alkylation of an aromatic substrate with a C2-C4 alkylating agent in a multistage reaction system in which the aromatic substrate/alkylating agent mole ratio is pro-gressively decreased when going from one stage to another. In this aspect of the invention, the reaction stages are operated under temperature and pressure conditions effective to cause alkylation of the aromatic substrate with the pressure being ' abave the vapor pressure of the aromatic substrate and below the vapor pressure of the alkylating agent at the alkylation reaction conditions. A feedstock comprising the aromatic substrate and the alkylating agent is supplied to the initial reaction stage in relative amounts to provide a first mole ratio of aromatic sub-strate to alkylating agent. Effluent comprising a mixture of the aromatic substrate and alkylated product is withdrawn from each reaction zone and supplied to the next succeeding reaction stage, Alkylating agent is supplied along with the effluent to the next ._.

succeeding reaction stage to provide an overall progression across the multistage reaction system of a decreasing mole ratio of the aromatic substrate to the alkyl.ating agent in an amount to provide a final mole ratio of aromatic: substrate to alkylating agent for the final reaction stage which is less than the first mole ratio supplied to said initial reaction stage. Preferably, the multistage reaction system in this embodiment of the inven-tion comprises from 3-8 reaction stages operated under conditions producing the monoethylation of benzene in which the xylene make based upon the amount of ethylbenzene produced, is no more than 0.05 wt.~, preferably no more than 0.03 wt.$ as indicated pre-viously.

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BRIEF DESCRIPTION OF THE DRAWINGS
FIGURES la-lc and 2a-2c are cJraphs illustrating the re-sults of transalkylation experiments carried out using two dif-ferent zeolite Y catalysts.
FIGURES 3a-3c are graphs illustrating the results of experimental work carried out in the transalkylation of diethyl-benzene using another zeolite Y catalyst.
FIGURES 4a-4c are a series of graphs showing experimen-tal work carried out with a rare earth zeolite.
FIGURES 5a, 5b and 6 are graphs illustrating further experimental work employing a zeolite Y catalyst.
FIGURE 7 is a simplified schematic flow diagram illustrating one embodiment of the invention in which a poly-ethylbenzene fraction is subjected to a residue extraction step prior to transalkylation.
FIGURE 8 is a schematic illustration of a modification of the process of FIGURE 7 in which the output from the trans-alkylation reactor is subjected to a separation step prior to re-cycle.
FIGURE 9 is a simplified schematic illustration of yet another embodiment of the invention in which the bottoms fraction from. an ethylbenzene column is supplied directly to a trans-alkylation reactor with the output of the transalkylation reactor being supplied to a downstream separation zone, FIGURE 10 is a schematic flow diagram showing a modifi-cation of the embodiment of FIGURE 9.

FIGURE 11 is a schematic illustration of a specific embodiment for carrying out the invention employing a plurality of series connected reaction stages.
FIGURE 12 is a graph showing the results of experimental work involving dehydration of a feedstream to a transalkylation reaction carried out over a zeolite Y catalyst.
FIGURE 13 is a graph showing the results of experimental work involving dehydration of a feedstream to a transalkylation reaction carried out over another zeolite Y catalyst.

-26- ~~,J~~d~
DETAILED DESCRIPTION
A preferred application of the invention involves liquid phase alkylation over a zeolite beta alkylation catalyst coupled with liquid phase transalkylation over a molecular sieve trans-alkylating catalyst selected from the group consisting of zeolite Y and zeolite beta. An especially preferred embodiment of the invention involves the use of zeolite beta as an alkylation cata-lyst and zeolite Y as a transalkylation catalyst. However, as will appear below, other molecular sieve catalysts can be employ-ed in carrying out the present invention. Moreover, while a pre-ferred application of the invention is in the use of liquid phase transalkylation in conjunction with liquid phase alkylation, the invention can be carried out employing vapor phase alkylation, as disclosed, for example, in the aforementioned patent to Dwyer, coupled with liquid phase transalkylation and appropriate recycle of the transalkylated product to a separation zone.
In its more general aspects, the invention involves transalkylation coupled with aromatic alkylation employing C~-C4 alkylating agents which, broadly stated, can be alkylating agents of the type disclosed in the aforementioned patent to Pollitzer et al., such as ole:Eins, alkynes, alkyl halides, alcohols, ethers and esters. The most widei:y used alkylating agents are ethylene and propylene applied in the production of ethylbenzene and cumene, respective7.y. The invention is especially applicable to the ethylation of benzene under conditions in a manner in which byproduct xylene yields are reduced and the invention will be ~~ .m _.

described specifically by reference to the production of ethyl-benzene together with the attendant transalkylation of polyethyl-benzenes.
As noted previously, a conventional process fox the pro-duction of ethylbenzene involves recycsling polyethylbenzenes, separated from the ethylbenzene produc;t, to the alkylation reac-for where they undergo transalkylation to yield ethylbenzene. A
byproduct of this procedure is increased xylene yield in the effluent from the alkylation reactor. The presence of xylenes complicates downstream processing and separation steps. A par-ticular impact of a significant xylene content in the product stream is that it often mandates operation of the distillation column from which the ethylbenzene is taken overhead in a manner to provide a substantial ethylbenzene content, often times 15-20$
or more, in the bottom polyethylbenzene fraction. For example, ethylbenzene produced in accordance with the present invention can be employed in the production of styrene by catalytic de-hydrogenation. The boiling points of ortho xylene and styrene ' are very close, within 1°C of one another. As a practical matter, the ethylbenzene specifications will call for a very low xylene content, normally less than 2000 ppm. Tn order to meet this specification, it is normally necessary to operate the ethylbenzene column under moderate distillation conditions re-sulting in a high ethylbenzene content in the bottoms fraction as described above. Tkie present invention, by carrying out poly-ethylbenzene transalkylation in a separate reactor under relati-vely mild liquid phase conditions, minimizes the xylene make in the manufacturing process. This enables ethylbenzene recircula-tion to be reduced by limiting the ethylbenzene content in the polyethylbenzene fraction to 5 wt.~ or less, and where preferred catalysts are used to further minimize: xylene make, down to about 2 wt. $. or less ethylbenzene.
A preferred aspect of the present invention involves supplying the polyethylbenzene fraction, including both diethyl-benzene and the triethylbenzene and higher molecular weight com-pounds to the transalkylation reactor as contrasted with separating out a substantial portion of the diethylbenzene for recycle to the alkylation zone, as disclosed in the aforemen-tinned patent to Wight, or separating out trialkylaromatics with transalkylation only of dialkylbenzene, as disclosed in the aforementioned patent to Barger. In this respect, depending upon the configuration of the interface of the transalkylation reactor and polyethylbenzene or other separation zones, substantially all of the diethylbenzene and substantially all or most of the tri-ethylbenzene content will be supplied to the transalkylation reactor. In either case, the practical effect of this embodiment of the invention is that recycle to the alkylation reactor is limited to benzene and lighter components, e.g., ethylene, while most if not all of the triethylbenzenes together with diethylben-zenes are retained in the system ultimately for conversion to benzene and ethylbenzenes. This offers significant advantages over the prior art processes, not only in terms of reduced xylene makes as described previously, but also in terms of ultimate pro-duct yield.

In experimental work relative to the invention, a number of catalysts were employed in transalkylation tests carried out in an upflow, flooded-bed reactor, that is, only a liquid phase was in contact with the catalyst. The feed employed in this ex-perimental work was an approximate 1:1 mixture of benzene and the polyethylbenzene overheads fraction from a commercial operation employing vapor phase alkylation of benzene to produce ethylben-zene. A typical feed employed in the experimental work had the composition as shown below in Table I.

Table I
Non-Aromatic 0.32 Benzene 50.241 Toluene 0.000 Fthylbenzene 6.117 p+ M-Xylene 0.000 Styrene 0.063 o-Xylene 0.066 Cumene 3.973 n Propylbenzene 7.816 m + p Ethyltoluene 2.053 1,3,5-Trimethylbenzene 0.128 o-Ethyltoluene 0.356 1,2,4-Trimethylbenzene 0.536 1,2,3-Trimethylbenzene 0.401 m-Diethylbenzene 14.808 o + p-Diethylbenzene 7.328 Butylbenzenes 1.653 heavies 4.429 In the experimental work, the average pressure was about 300 psia with a pressure drop across the reactor ranging from about 5 to 15 psi. The temperature profile across the reactor was relatively constant with an endotherm from the inlet to the outlet of less than 10°C and usually less than 5°C. The experi-mental runs were initiated at relatively low temperatures, usual-ly less than 100°C and progressively increased as described lat-er. The space velocity was maintained relatively constant at a value of 6 hr.-l (ZHSV) based on the total hydrocarbon feed. Di-ethylbenzene conversions and selectivity to ethylbenzene were measured as a function of catalyst age (duration of the run) along with the production of various other components including xylenes.
In a first test run, the catalyst used was a commercial-ly available zeolite Y (identified herein in Catalyst A) in which the inlet temperature was progressively increased up to about 235°C and stabilized there with an average temperature increase through the reactor of only 1° or 2°C. The results of this ex-perimental work axe illustrated in FIGURES la-lc in which percent diethylbenzene conversion C, percent selectivity to ethylbenzene S, ortho xylene production O, in ppm, and temperature, T, °C, are plotted as curves 11, 12, 14, and 16, respectively versus the catalyst age A, in hours, on the abscissa. As can be seen from an examination of the data presented in FIGURE 1, the diethylben-zene conversion stabilized in about the 32-37~ range for a reac-' for temperature of about 237°C with the catalyst showing very little deactivation over the duration of the run. The select-ivity to ethylbenzene was virtually 100. During the run, O-xylene production stabilized at about 400 to 500 ppm.
Another test run was carried out using an experimental zeolite Y identified herein as Catalyst B. The results o~ this run are set forth in FIGURES 2a-2c in which curves 18, 19, 21 and 22 are graphs of diethylbenzene conversion, C, selectivity to ethylbenzene, S, parts per million O-xylene, O, and temperature, ~~2~

T, respectively plotted as a function of catalyst Age A. In this experiment, the catalyst was run for nearly 400 hours with the temperature, after initialization, increasing slightly with time to a final value of about 240°C. As can be seen, diethylbenzene conversion was relatively good, mostly in the 30-40~ range at relatively moderate temperatures. Selectivity to ethylbenzene was greater than 90$ and during most of the run was virtually at 100. The 0-xylene content of the product stream stabilized at about 900 ppm.
Yet another test run was carried out employing another zeolite Y catalyst identified herein as Catalyst C. The results herein in terms of diethylbenzene conversion, selectivity and as a function of time and temperature, are set forth in FIGURES 3a-3c. In FIGURE 3, curves 24, 25, 27 and 28 are graphs of diethyl-benzene conversion, selectivity to ethylbenzene, 0-xylene content (ppm), O, and temperature, T, °C as a function of catalyst age on the abscissa. As shown in FIGURE 3, diethylbenzene conversion was, on balance, slightly better than for catalysts A and B, and fell generally into the 40-50~ range at reactor temperatures ranging from about 210° to about 236°C. Selectivity to ethylben-zene was more than 90~ over much of the run at virtually 100.
O-xylene content stabilized at about 800-900 ppm. The catalyst showed very little deactivation over the life of the run.
A rare earth zeolite Y identified herein as Catalyst D
was employed in yet another test. The results for catalyst D are set forth in FIGURE~~ 4a-4c with curves 30, 32, 33 and 35 repre-senting graphs of diethylbenzene conversion, selectivity to -33- ~"~~t~ ~~~~
athylb~naene, ppr~r ~~xYlane and t~m~aeratur~, raa~eotivaly as a ~una~tioaa ~~ cat~lyat age, cutaly~it t~ ~hov~~a~ ralativelY 9fl~d x~~~
ault~ including diethylbenzetta ~c~s~vgt:~ion in the ~0-50~ ras~ga.
Initial r~1~ctivity way about 1DD0, with ss~lect~.vity fa111ng of~
slightly to abaut 94t tawmgd the nc~d of the t.-un. s~hil~ quad can°~
version and ~alectivity wat~a aoEa.i~~ved, the reaction tampcz'atur~
was substantially taigh~x than tsar the ~rxevlat~a zaralite Y, r~~ing to abcaut 2°70°t: at the ogr~c~.ugion a~ the roan, xbrrut 210 hours.
~h~ ~eada for the ~acperi~~ntal Worl~ da~iat~c~ in ~xBU~~s 1-4 confvgt~c~ gmnara~lly to ttx~ cs~mpositlon ahawn in ~'abl~ I.
~cwavat, th~ ~a~d fear the ~ira~t teat run tCa.talyat ~1 was ~re~ of s~rgho. xylana and the feed ~ar the aecouW runt tcatallrnt H 3 oan-~
tainted about 0.02 pe~ra arsd mete xxlent$.
~ddl.tional e~parimental war~C und~z the above~idanti~ied conditions Was caxri~d oat employing three ~additianal aatalyatat C~talya~t ~, a canon n~cchange resin avr~i.labl~ ~rb~ ltohra ~ Haas un~sr the dasigna~xion l~anbexlyat 15, Catalyst ~', a. 9uparacidia alu~ina available from ~larahawayil,tra~. under rh~ designati~~a 3999 and ~atalyatc ~ a nictcel modi~i~d mordenite a~railable Exam Utsion Carbi.dc under tote, designation NibCn9044. t~a'talyat ~ sl~a~asd little c3lathylbanzen~ es~nversinn sand r~o athylbangann psoduatian~
up to thn tune th~ axp~rlit~ant was kar~inat.~d, at about 5t? Maura dlnd ~ e'.eR1~1~1'~~'.Illr~ 8~ ~.J~~~.i d51~ 1:0 ~X~6.~'~l~l~n~d~.
1~~~=i.~u~t~~~e Catalyst F praduc~d diethylbsnz~n~ canver~ion~ r~raging txoaa about to 20~ at temperatures ranging tram about 300"-450°C with, ..
s~l~caivi%y to ethylbenzen~ ~or the moe~t part being ibaa that s0~. Catalyst. c~ was run tnr 100 hears at te~mperatur~a ranc~ia~g up to 350~C a~t~d e~hawed almost na dia$hylben~ena conversion.
~Pha ~aoltt~ Y catal,yata ident~.lies3 above as Catalysts ~

and B were also used in downflow trickle bed reactors where a substantial gas phase was present. Fresh and regenerated cata-lysts were used. This experimental work was carried out at pressures of about 330 psig, nominal space velocities of about 10 hr-1 (LHSV> and average reactor temperatures of about 300°C in the case of fresh catalyst A, about 300°-400°C in the case of fresh Catalyst B and about 200°C in the case of the regenerated catalysts. For fresh catalyst A, initial diethylbenzene conver-sion was about 24~ but this fell off rapidly after a few hours.
The catalyst was then regenerated and under the less severe tem-perature conditions of about 200°C, initial diethylbenzene con-version was high, about 60$ but this, again, reduced to only a few present after about 24 hours.
When employing fresh catalyst B the initial diethylben-zene conversion was over 50~, but this fell to about 20~ after about 5 hours and then decreased further to only a few percent.
The regenerated catalyst B, when run at the lower temperature of about 200°C, showed an initial diethylbenzene conversion of about 58$ which declined to about 27~ after 29 hours, at which time the run was terminated.
Yet additional experimental work was carried out employ-ing zeolite Y identified above as catalyst B in which the feed was a relatively pure diethylbenzene mixed in approximately equal parts with benzene. Unlike the feedstock employed in the experi-mental work of FIGURES 1 through 4, the pure diethylbenzene feed-stock contained only very small amounts of material susceptible to cracking or other conversion reactions, e.g., deethylation, to produce xylenes and was also free of ~;ylenes. The makeup of the feedstock in this experimental work is set forth below in Table II.
Table II
Components Wt,~

Non-aromatics 0.01 Benzene 56.58 Toluene 0.09 Ethylbenzene 0,01 Xylenes 0.0000 n-PR-BZ 0.02 m,p-ethyltoluene 0.03 o-ethyltoluene 0.01 124 trimethylbenzene sec-BU-BZ 0.47 123 Trimethylbenzene m,Diethylbenzene 27.62 o,p-diethylbenzene 14.27 n--BU-B Z 0 . 3 5 Heavies 0.54 In this test run,.the inlet and outlet pressures were held at 310 and 305 psig, respectively. The average temperature of the reactor was increased approximately linearly with time from an initial value of about 198° to a final value of about 298°C. The space velocity was generally held within the range of _.

about 5.8-6.0 hr'1 (LI-ISV) with the exception of about two-thirds of the way through the test where it fell to about 5.1 before re-covering to the higher value.
The results of this test run are set forth in FIGURES 5 and 6. In FIGURE 5a, curve 38 is a graph of temperature, T, ver-sus catalyst A in hours on the abscissa. In FIGURE 5b curves 40 and 41 are graphs of percent selectivity to ethylbenzene and per-cent ethylbenzene conversion, respectively. Curve 42 is a graph of the total xylene make, X, expressed in ppm, based upon the amount of ethylbenzene produced. FIGURE 6 shows the relationship between ethylbenzene conversion and temperature. Curve 43 is a graph of ethylbenzene conversion, C, on the ordinate versus tem-perature, T, on the abscissa.
As indicated by the data set forth in FIGURE 5, xylene make remained low throughout the test run. No xylene was pro-duced until the temperature was increased to about 260°C (which generally corresponds to the reduction in space velocity to about 5.1 hours-1 as reported previously). Percent conversion remained good until the temperature was increased above 280°C. As indi-Gated in FIGURE 6, ethylbenzene conversion appears to remain above 50$ over a temperature range of about 200°-290°C with the optimum range appearing to be about 210° to 28U°C.
With further reference to 'the drawings, FIGURES 7 through 10 illustrate schematic flow diagrams illustrating dif-ferent embodiments o:E the invention. It will be assumed for purposes of discussion that the invention is applied in the pro-duction of ethylbenzene by reaction of ethylene with benzene and ~~~~~r~~~a that the alkylation reaotion in carrtad out i~ ~ E3.oodedwbed li~u~.d phase al'~tlation r~acte~r employing ~eol9.te b~t~:r ~~o~.ita Y
or ra~o3.it.~ amega ,~a ~th~ alkyla~.i4n catalyst. Hv~a~ver, as noted previouall' aid as di~cusssd iaa c~rsater de~tnil below, th~ ~llkyla~
Lion step can be oc~nducted as a v~pc~s phase seaotien emplcaying a catalyst auGh as ~ilicallt~ og ~5~~~.
Ftafarxing flrgt tg l~IGIJ~tE '~, a fmedatraam 50 ccantainin~
ethylene and benzene supplied via lanes 51 and 5~o r~~p~cti'~alW
is passed first tc~ a d$hydrator 54r whexe the mater eontant is reduced to a levsl of ~bnut 1p0 ppm or leas, pr~f~rably about ~0 ppm ~~c legs, and then to an alkylation reaction gone 54. The alkylation reactor, vthich may comprl,~a a pluxaJ.ity a~f ~arie~ con nested adiabatic r~act4ra with ir~tarstaga infection of ethylene an8 mlao interatage ogoling, normally will.,b~ operated at an.
av~rager temperature of abQUt ZZ~°C and under auffi~ciant pressure, about 6U0 Asia or above, to maia~ta~.n the b~n~eria in the liquid phase and at least sheaf ~ t~~le~ percent of athylac~s ae~.~ib~.li~~d , in the ben~dne, hs an altarnativ~ to aging adiabatic r~aci:orar one ar m~ra isothermal reao$s~s~ cnn b~ sm~laYad ~rifi~h suitable oosling .m~arr~ um~d tc~ anaintain a aubatantiaily aonataat tempara°°
turn (little or t~~ tecnperat~ura dlffereritial~ from the islet to the r~ut.le~: of the seact.or. "l~ha effluent a~.~eeatm ffom the a1~3~16t~ "
Lion reactor i~ supplied to a pxe~fract~.onatiot~ oolumn 59 wi9loh la gperat~d tn psovida a .li.ght ~varheacia traatian includine~ banaen~
which la auppli~d via line 59 to the a~.bcY1~tio~~t Yeaot~r input a~ld a haavi~r lieiuide Zra.mtian containing b~naan~, ~t.hylb~an~~n~
a~parativn tone b~..
Th~ output from the pre~ractionatis~a~ Bona 56 is auppli~d'"
via ilna 60 ~a a bac~rena asparati.on ~~one ~1~ The o~t~rhe~ed, frao-tion from column 61 contains the remaining benzene which is re-cycled via line 62 to the alkylation reactor input. The heavier bottoms fraction from column 61 is supplied via line 64 to an ethylbenzene separation zone 65. The overheads fraction from column 65, of course, comprises ethylbenzene which is supplied to storage or to any suitable product destination. By way of ex-ample, the ethylbenzene may be used as a feedstream to a styrene plant in which styrene is produced by the dehydrogenation of ethylbenzene. The bottoms fraction containing polyethylbenzenes, heavier aromatics and preferably only a small amount of ethylben-zene, no more than 5$ as discussed previously, is supplied to polyethylbenzene separation zone 68. The bottoms fraction of column 68 comprises a residue. The overhead fraction from column 68, containing polyethylbenzene, triethylbenzene (usually~in relatively small quantities) and a minor amount of ethylbenzene is supplied to a transalkylation reaction zone 72. By minimizing the amount of ethylbenzene recovered from the bottom of column 65, the ethylbenzene content of the transalkylation feedstream is kept small in order to drive the transalkylation reaction in the direction of ethylbenzene production. The polyethylbenzene frac-tion withdrawn overhead through line 70 is mixed with benzene supplied via line 73 and then supplied to the transalkylation re-actor 72. The mole ratio of benzene to polyethylbenzene should be at least 1:1 and preferably is within the range of 1:1 to 4:1.
The output from the transalkylation reactor containing benzene, ethylbenzene and diminished amounts of polyethylbenzenes is supplied via line 75 to the benzene column 61.

~n the proCe~~ depicted in ~gGtlR~ 7, the alkylat:ian re~
actian is carried out in the lfc~uid phase with ~lshyd~'atidn ~f gees to the elk ylation rsactor...~s ~ot.~d previoaaly, the inven-tion may bs carried out smp~.oyia~g vapgr ph~as al.kyl~~.ign fol3.ow~d by liquid phase tranaalkylatis~r~ and in such reactions, dapsndirsg upon the catalyst ~mployed, sigrai~icant ~qe~antitisa r~~ wats~r may big included ire ttis feed t~ ~.hs alkwlation Reactor. In this Caaa.
it taay b~ necessary to asparat~ly aacornpliah dehydration of the °
~~sd to the t~ranaal3cyl.ation rbaotor. such dehydrati~n easy take pZaas at any point upstream at t;.he tranaaikylat~.~n reactor, and ,~ naosaeary, dahydratinn should be aocorapliahsd with r~s~rsct to the ~rest~ bonssne feed auppli~d via lirse '1~ as wsll~ an with ro-spsct to the polyethylene comps~nant praduc~d dux~,lng the alkyla~-tiolt lgaCt.iidn a ~xGUItE 9 diacloa~aa a anodl.fication c~ the pr~aasga dia-claaed in ~iGo~~ 7 in wriiah tha~ Iran~alkYl.atior~ reactor output is atab~ectsd to further treatment prior to x~scyci~ to the asparatian system. ~~a embadi~ant of FYGUI~~ 8 is particu3,ax~.y useful irf thc~as~ cases in which relatively high oonveraioa~ is achieved in the tran~~lkylati.on r~acts~r. In flee smbcadi.r~ont o! ~IG~it~ ~, 'the alkylnti4n rsaator and separation gyatem .ia idsrtti~cal to that of hYQI~R~ '~ and like oomparis~tts are indioatsd.,by the. $a~a~ xe~srst~as ahataotars. ~ liowavsx, t3~e output from they tranaaskylation rs~ctor to 'nup~slisai to a Dsoandary aspara~tion roes ?7 which may take they form of a diatil,lation o~lumn which is c~peratedt in a inannsr to. .
produce .a bottc~rn' purge stream withdrawn via line ?8 and. a raaycl.s stream withdrawn via ~.ing 80 and supplied to the bsn~sns ~~lut~n.
elm pur:ge stream containing heavy hydrocarbons is wii~h-drawn from the ~'yats~, thus providing a ~aartially airaqlg..gaaa ..

system in which high molecular weight hydrocarbons are not recir-culated.
FIGURE a illustrates yet another embodiment of the in-vention in which the polyethylbenzene fraction recovered from the ethylbenzene column is directly passed to a transalkylation reac-tor. In FIGURE 9, the same system components as shown in FIGURES
7 and 8 are designated by like reference numerals. As shown in FIGURE 9, the output from the ethylbenzene column 65 is mixed with benzene supplied via line 82 and supplied to the trans-alkylation reactor 84. Here, the entire polyethylbenzene frac-tion is subjected to transalkylation. The conditions employed in reactor 84 may be the same as described above with the ratio of benzene to polyethylbenzene ranging from about 1:1 to 4:1.
It will be recognized that the procedure depicted in FIGURE 9 is similar to that of FIGURE 8 except that the entire bottoms fraction from the ethylbenzene column is subjected to the transalkylation reaction. Limiting the ethylbenzene content of the input to the transalkylation reactor to no more than 5$, pre-ferably 2~ or less is especially significant here in establishing conditions promoting the transalkylation reaction. The output .
from the transalkylation reactor is applied via line 85 to a post transalkylation separation zone 86 which may take the form of a distillation column operated to produce an overhead fraction that is comprised predominantly of benzene and ethylbenzene and a bot-toms fraction, composed predominantly of Cg and Clp hydrocarbons such as ethyltoluene, cumene, butylbenzene, etc., which is elimi-nated from the recycle stream by purge line 88. The overheads fraction is recycled through line 89 i.o the benzene column simi-larly as described above.
The embodiment of FIGURE 10 is similar to that of FIGURE
except that the transalkylation reactor output is split, with a portion being directly supplied to the benzene column 61 via line 92 and the remainder to the separation zone 86 which is op-erated as described above. The configuration of FIGURE 10 provi-des a means for maintaining a low concentration of Cg and C10 hydrocarbons in the system and reduces the energy costs of opera-ting column 86. Typically about 60$ or more of the transalkyla-tion reactor output is recycled directly to the benzene column 61 with the remainder being directed to the separation zone 86.
As noted previously, one of the zeolite catalysts useful as an aromatic alkylation catalyst is zeolite beta and a specific embodiment of the present invention involves the use of an aroma-tic alkylation catalyst comprising a modified zeolite beta, under relatively mild liquid phase alkylation conditions. The inven-tion is especially applicable to the ethylation of benzene under mild liquid phase conditions producing little or no xylene make, and the invention will be described specifically by reference to the production of ethylbenzene. Eowever, other alkylation reac-tions may be utilized in carrying out the invention. For ex-ample, the invention may be applied to the reaction of propylene with benzene to produce cumene. Also, while olefinic alkylating agents normally wil:L be employed, other alkylating agents such as alkynes, alkyl halides, alcohols, ethers, and esters as disclos-ed, fox example, in the aforementioned patent to Pollitzer et .,.

al., may be used. Other aromatic substrates such as toluene and xylene may also be subject to alkylat:ion in accordance with the invention.
The activity of zeolite beta as utilized in the present invention is in direct contrast to the teachings found in the aforementioned patent to Dwyer which suggests that zeolite beta, because of its low constraint index, is unsuitable for use under the relatively severe conditions involved in the vapor phase ethylation of benzene, and in the aforementioned patent to Young, which limits its application to relatively long chain alkylating agents. Dwyer, which is directed to ethylbenzene production under relatively severe temperature conditions well above 300°C, i.e., 650°-900°F, and preferably 700°-850°F, teaches as noted above, that zeolite beta cannot be used as a catalyst in the ethylation of an aromatic substrate even under the high tempera-ture conditions involved in the Dwyer process.
The present invention proceeds in a manner directly con-trary to these prior art teachings. In the invention, zeolite beta is a highly effective catalyst for the alkylation of an aro-matic substrate with low molecular weight (C2-C4) alkylating agents. Moreover, it is an effective alkylating agent under mild liquid phase conditions involving temperatures of 300°C or less, providing high conversion efficiency and high selectivity to monoalkylation. As noted previously, these mild reaction con-ditions permit the production of ethylbenzene with a xylene make which is negligible and, for all practical purposes, nonexistent.
Crystalline zeolite beta which is identified by its x-ray diffraction pattern and basic procedures for its preparation are disclosed in the aforementioned U.S. Patent No. 3,308,069 to Wadlinger et al. As described therein, zeolite beta is synthe-sized by the hydrothermal digestion of a reaction mixture com-prising silica, alumina, an alkali or alkaline earth metal oxide or hydroxide and an organic templating agent.
The zeolite beta catalysts employed in 'this embodiment of the invention preferably are of ultra-low sodium content which can readily be produced by new procedures as described in detail below. Low sodium content zeolite betas are in themselves, known in the art. For example, the aforementioned patent to Wadlinger discloses zeolite beta formed by treating a dried product result-ing from the digestion procedure which was exchanged continuously for 48 hours with a 2$ solution of ammonium chloride. After washing free of excess chloride ions, the catalyst was dried and calcined for three hours at 1000°F to produce an acid beta alumi-nosilicate having 0.07$ Na content. The aforementioned patent to Culvert et al. also discloses zeolite beta of relatively low sodium content, e.g., 0.14 wt.~ and 0.11 wt.~ Na.
The preferred zeolite beta of the present invention is characterized by a sodium content substantially lower than those disclosed in the patents to Wadlinger et al. and Culvert et al.
It is also characterized in terms of a very high surface area, specifically at least 600 m2/g based upon the crystalline zeolite beta. The preferred zeolite beta has a low sodium content of less than 0.04 wt.~ and preferably less than 0.02 wt.$, expressed as Na20. The preferred zeolite beta is produced by means of a ~~:' %~~,~z.~;~r.D

series of ion exchange and calcination procedures carried out em-ploying as-synthesized zeolite beta as a starting material. The synthesized zeolite beta can be produced by the hydrothermal digestion of a reaction mixture in accordance with any suitable procedure such as those disclosed in the aforementioned U.S.
patents to Wadlinger et al. and Calvert et al., and the aforemen-tinned European patent applications.
In producing modified zeolite beta in accordance with the present invention, the as synthesized zeolite beta is sub-jected to a plurality of sequential ion exchange and calcination treatments to arrive at a molecular sieve product of extremely low sodium content, substantially below the sodium content of the acid zeolite beta produced in accordance with the patent to Wadlinger as described above. In addition, the final molecular sieve product has a substantially higher surface area than that heretofore attained for zeolite beta. This embodiment of the invention involves an initial ion exchange treatment of the as-synthesized zeolite beta followed by calcination, followed by subsequent ion exchange to arrive at a product of ultra-low sodium content and high surface area.
While the invention is not to be limited by theory, it is believed the initial ion exchange treatment removes a substan-tial portion of the sodium or other alkali metal ions incorporat-ed during synthesis, such that the subsequent calcination pro-cedure, carried out under essentially anhydrous conditions, does not lead to collapse or otherwise undesirable changes in the crystal structure of the zeolite beta. This calcination pro-cedure, together with the initial ion exchange treatment, pre-ferably results in at least a twofold increase in the zeolite beta surface area over the surface area of the zeolite in the as synthesized form.
The intermediate calcination step is effective to decom-pose the organonitro templating agent within the pore network of the zeolite beta and opens up the molecular sieve channels so that they are readily susceptible to subsequent ion exchange treatment. After the initial calcination step, an ion exchange treatment is again carried out in order to protonate an addi-tional portion of the active sites in the zeolite by exchanging off sodium or other alkali metal ions. This second ion exchange treatment results in a zeolite beta of extremely low sodium con-tent, less than 0.04 wt.~ Na20, and high surface area, at least 600 m2/g based upon the zeolite beta crystalline structure. The preferred ion exchange medium is an ammonium salt. The zeolite beta resulting from the second ion exchange treatment is mixed with a binder, pelletized-and dried and then subjected to another calcination step in order to convert the ammonium exchanged act-ive sites to acidic iH+> active sites.
As synthesized zeolite beta used as a starting material for the present invention can be synthesized by the hydrothermal_ digestion of silica, alumiria,, or sodium and other alkyl metal oxides, and an organic templating agent in accordance with any suitable procedure :such as those disclosed in the aforementioned U.S. Patents to Wad7_inger et al. and Calvert et al. and the aforementioned European patent applications.

Typical digestion conditions include temperatures rang-ing from slightly below the boiling point of water to about 170°C
at pressures equal to or greater than the vapor pressure of water at the temperature involved. The resulting reaction mixture should be maintained under mild agitai~ion, such as stirring, for periods ranging from about 1 day to several months to achieve the desired degree of crystallization to form the zeolite product.
Lower temperatures will normally require longer periods in order to arrive at the desired crystal formation. For example, at tem-peratures of about 100°C, crystal growth may occur during periods , ranging from about 1 month to 4 months, whereas, at temperatures near the upper end of the aforementioned range, e.g., about 160°C, the digestion period may be from 1 or 2 days up to about 1 week. At intermediate temperatures of about 120°-140°C, the di-gestion period may be for several weeks, perhaps 2-4 weeks.
Any suitable templating agent may be used in forming the zeolite beta molecular sieve crystalline structure and, as indi-Gated by the references referred to above, appropriate templating agents include tetraethylammonium hydroxide and halides such as tetraethylammonium chloride and dibenzyl dimethyl-ammonium hydroxide or halide such as dibenzyl dimethyl ammonium chloride.
The reaction components may be varied in accordance with tech-niques well known in the art to provide the zeolite beta product of varying silica/a7_umina ratios. Typically, the reaction mix-ture used to synthe:~ize the zeolite beta molecular sieve will contain formulations within the following retie xanges:

Table III
Si02/A1203: 20-1000 H20/Si02: 5-200 OH-/Si02: 0.1-0.2 M/Si02: 0.01-1.0 R/Si02: 0.1-2.0 In the above table, R is the nitroorgano templating agent, e.g., a tetraethylammonium group and M is an alkali metal ion, usually but not necessarily, sodium. For a further description of zeolite beta and methods for its synthesis, recourse may be had to the above patents and patent applications including specifi-cally, U.S. Patent Nos. 3,308,069 (Wadlinger et al.) and 4,642,226 (Calvert et al.).
As explained above, a critical first step in carrying out the method of the present invention lies in treating the as synthesized zeolite beta with an ion exchange medium prior to high temperature calcination which is designed to remove a predo-minant portion of the templating agent from the intercrystalline molecular sieve network. The product at the conclusion of the hydrothermal digestion procedure leading to crystallization of the zeolite beta, can be washed and dried at a temperature usually substantially less than 200°C, e.g., about 150°C, design-ed to remove water from the product including dehydrating the product of water retained within the intercrystalline pores.
Higher calcination temperatures, typically on the order of 400°C

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The ion exchange medium may include any suitable agent effective to protonate active sites in the molecular sieve struc-ture by exchanging the sodium or other alkaline metal ions incor-porated during the crystallization procedure. P.mmonium salts, as described in detail below, are the preferred ion exchange agents and the invention will be described in detail with reference to the use of such ion exchange agents. However, it should be recognized that other ion exchange agents compatible with aci-difying the active sites in the molecular sieve network can be used in carrying out the invention. For example, ion exchange can be accomplished using aqueous solutions of mineral acids, such as hydrochloric acid, nitric acid, or sulfuric acid or low molecular weight organic acids such as formic, acetic, or pro-pionic acid. The use of acids, particularly the strong mineral acids, may be undesirable in preparing and modifying the zeolite beta for certain applications in that dealumination of the zeo-lice may result. in addition, organic salts, such as ammonium acetate and primary, secondary or tertiary amine salts incor-porating low molecular caeight alkyl substituents such as methyl and ethyl groups, may be employed. Examples of such amine salts include alkyl ammonium chlorides and nitrates such as ethyl ammo-nium nitrate, methyl ammonium nitrate, trimethyl ammonium nitrate and like amine salts may be employed. Also included as ion ex-change agents are quaternary ammonium salts based again on low molecular weight alkyl groups.

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As noted previously, normally inorganic ammonium salts, such as ammonium nitrate, ammonium sulfate, ammonium carbonate, or ammonium chloride, will be used as the ion exchange agent.
Ammonium nitrate is particularly preferred since upon heating, subsequent to the ion exchange step, it decomposes to ammonia and nitric acid which, in turn, produces water and nitrogen oxides which evolve from the catalyst product. A salt such as ammonium sulfate is usually less advantageous because of its substantially higher decomposition temperature relative to ammonium nitrate.
Also, in some cases, the sulfur may incorporate into the molecu-lar sieve framework replacing framework oxygen.
Preferably, the initial ion exchange treatment is carried out in two discrete steps each involving submersing the zeolite beta in fresh ion exchange solutions. During the first and preferably during both ion exchange steps, the zeolite beta remains submersed in the medium until the exchange system approaches equilibrium between the ammonium and sodium (or other alkaly metal) ions. By way of example, employing a 2 normal ' ammonium nitrate solution, the zeolite beta may initially be sub-mersed in the ion exchange solution for a period of about 1-5 hours at a temperature of 50°-90°C. Upon conclusion of the ini-tial treatment, the zeolite beta is withdrawn from the solution, caashed with water a;nd then submersed in a fresh solution of 2 normal ammonium nitrate. The time and temperature conditions here may be the same as for the first submersion.
At the conclusion of the initial ion exchange treat-men a , the ammonium exchanged zeolite beta is then subjected to a ~~? ~~)~~

high temperature calcination treatment. The calcination treat-ment is carried out at a temperature and for a time sufficient to evolve at least a predominant portion, and preferably substan-tially all, of the templating agent from the interstitial pore spaces of the channels of the molecular sieve network. The calcination temperatures should be at least 400°C. It normally will be no more than 700°C, although higher temperatures can be employed. The calcination treatment should be normally carried out for a period of about 2-10 hours, although at higher tempera-Lures, shorter periods of down to about 1 hour may be adequate.
The calcination treatment may extend beyond 10 hours, although there usually will be no reason for the longer calcina-tion treatment. Preferably, the surface area at the conclusion of this calcination step is at least twice the surface area of the zeolite beta in the as synthesized form. As indicated by the example described below, three-fold or more increase in surface area can be achieved at the conclusion of the calcination step.
The initial calcination step is followed by a second ion exchange treatment which results in a further increase in surface area of the zeolite beta and a further decrease in the sodium, or other alkali metal ion content. This post-calcination ion ex-change treatment is, like the initial treatment, preferably carried out in two :stages by twice submersing the zeolite beta within fresh ion exchange solutions. The time and temperature parameters employed in the second set of ion exchange treatments may be the same as those involved in the first ion exchange treatment.

At the conclusion of the second set of ion exchange treatments, the zeolite beta typically will have a surface area at least twice that of the original starting material and a very low sodium content of no more than 0.04 wt.$ calculated as Na20 and usually less than 0.02 wt.~ Na20.
Where the resulting zeolite beta is to be used as a catalyst, it normally will be mixed with a binder such as alumina salt, gamma/alumina, or other refractory oxides to produce a mulled zeolite beta binder mixture. The mixture can then be palletized by any suitable technique such as extrusion, and the resulting pellets then dried. At this point, the palletized binder zeolite product is calcined under conditions sufficient to decompose the ammonium ions on the active site so the zeolite beta can arrive at the acid (H+) form. By way of example illus-trating the present invention, an as synthesized zeolite beta having a silica/alumina ratio of about 20-50 and containing tetraethylammonium hydroxide as a retained templating agent, was used as a starting material. The as synthesized zeolite beta had an initial surface area of 210 m2/g and a sodium content of about 0.5-1$ Na20. The as synthesized zeolite beta was initially sub-jected to an ammonium ion exchange treatment by submersing 100 grams of the catalyst in 1 liter of an aqueous solution of ammo-nium nitrate having a normality of 2. The zeolite beta was sub-mersed in the ion e~:change medium under mild agitation at 85°C
for a period of two hours. The zeolite beta was then separated from the ion exchange solution, washed and retreated with a fresh solution of 2 normal. ammonium nitrate again at 85°C far a period ~~~~~z~

of two hours. The surface area at the conclusion of the second ammonium exchange step was 247 m2/g and the sodium content was less than 0.11. The ammonium exchanged zeolite beta was then calcined at a temperature of about 560°C for two hours. The sur-face area at the conclusion of the calcination step was 666 m2/g.
After calcination, the exchanged and calcined zeolite beta was cooled and then subjected to a second ion exchange treatment involving a two-stage process, with each stage extend-ing for two hours using the same ion exchange medium and under the same conditions as used during the initial treatment. At the conclusion of the third ammonium exchange procedure (the first stage of the second treatment>, the surface area of the zeolite beta cvas further increased to 708 m2/g. The surface area at the conclusion of the final ion exchange treatment was 815 m2/g. The sodium content at the conclusion of the final ion exchange step was reduced to a value where it could not be measured using ato-mic absorption techniques. Based upon this analysis, the Na20 content was substantially less than 100 ppm.
'The ammonium zeolite beta was mulled with peptized alu-mina in a proportion of four parts zeolite beta to one part alu-mina binder. The resulting plastic zeolite binder mixture was extruded to form pellets having the size of about 1/16" and the resulting pellets were then calcined at 560°C for two hours. The surface area of the final product, based upon the zeolite binder mixture, was 642 m2/g.
Modified zeolite beta produced in accordance with the present invention can be used in various catalyst applications as indicated previously or in other applications, for example, such as selective absorbent. Where used as a catalyst, it may often times be desirable to incorporate a metal component into the zeolite beta binder substrate. Suitable metal components include those found in groups VIB and VIII of the Periodic Table.
Specific metals include chromium, molybdenum, tungsten, vanadium, iron, cobalt, nickel, copper, platinum, and palladium.
In experimental work carried out respecting the inven-tion, the high surface area, ultra low sodium content zeolite beta described above, was employed as a catalyst in the reaction of ethylene and benzene to produce ethylbenzene. The experimen-tal work was carried out in an upflow reactor heated by a sand bath set at a nominal temperature of 200°C. The reactor contain-ed 3.6 grams (7.0 ml) of catalyst in the form of 1/16" pellets based upon the zeolite-binder mixture arid having a surface area of 642 m2/g as described previously. The benzene was supplied to the bottom of the reactor at a rate to provide a space velocity (LHSV) of 10 hr-1. Ethylene was supplied to provide a benzene/
ethylene mole ratio of 5.2 with the actual mole ratio varying during the experimental work from about 5.0 to 5.3. The results of the experimental work are set forth in Table IV. The effluent analysis is set forth in weight percent for benzene and ethylben-zene and for various other components including toluene, cumene, meta-diethylbenzene, and ortho and para diethyl benzene in yields relative to ethylbenzene. The total xylene yield throughout the run was zero.
The reactor was equipped with four thermocouples spaced _5a_ evenly from the inlet, TC #1, to the outlet TC #4. From the exo-therm profile indicated by the thermocouples, it is evident that most of the alkylation reaction occurred in the lower portion of the catalyst bed. Thus, the effective space velocity was substantially higher than the nominal value of 10 hr'1 (LHSV>.

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From an examination of the experimental data presented in Table IV, and bearing in mind that, for the most part, the ethylene charge to the reactor was slightly less than 20~ of the stoichiometrically equivalent amount of benzene, it can be seen that the zeolite beta catalyst is highly active and shows good selectivity to ethylbenzene production. The activity of the catalyst remained substantially undiminished after the duration of the experimental work.
In carrying out this embodiment of the invention, the alkylation reaction is carried out at pressures well above the vapor pressure of the aromatic substrate at the reaction tempera-ture involved in order to ensure that a liquid phase is retained in the reactor. In order to provide a complete liquid phase reaction, a flooded-bed format is used in which the catalyst bed is completely immersed in liquid. This can readily be accomplished using an upflow technique such as used in the ex-perimental work and this usually will be preferred i.n carrying out the invention. However, downflow flooded bed operation can' be accomplished by control of the outlet flow rate to ensure that the catalyst beds are covered by liquid benzene or other aromatic substrate.
Preferably, a staged reaction format is employed in order to ensure good solubility of the ethylene (or other alky-lating agent) in the benzene for other aromatic substrate) so that the entire reaction takes place in the liquid phase. In addition, use of multiple stages provides an opportunity for interstage cooling where adiabatic reactors are used or permits cal Ls3 s ~'7 ~, ~.~~l~~.a~~~
_5s_ the use of several isothermal reaction stages.
Turning now to FIGURE 11 of the drawings, there is shown a schematic illustration of a staged reactor system used for the production of ethylbenzene by the reaction of ethylene with ben-zene which includes a plurality of adiabatic reactors with inter-stage cooling and injection of ethylene. More particularly, and as illustrated in the drawing, ethylene and benzene are supplied via lines 102 and 104 to the inlet line 105 of a dehydration unit 106 which is operated in accordance with another embodiment as described hereinafter. The dehydration unit functions to de-hydrate the input to the alkylation reactors so that it is essen-tially dry, preferably containing less than 100 ppm, more preferably, less than 50 ppm, water. By way of example, dehydra-for 106 may take the form of a packed column packed with a desic-cant such as silica gel or other suitable hydrophilic medium.
The dehydrator effluent is supplied to a reactor 108, the first of a plurality of series connected alkylation reactors operated in an upflow mode. Reactor 108 is operated at an average temperature of 300°C or less, and preferably, at an average temperature within the range of 200°-250°C. The pressure on reactor 108 is sufficient to maintain the benzene in the liquid phase and preferably is at least 50 psi above the vapor pressure of the benzene at the reactor temperature. Typically, the reactor pressure is within the range of about 500-600 Asia.
The remaining downstream reactors normally are operated under approximately the same conditions as the initial reactor. The effluent from the initial reactor 108 is withdrawn via line 109 rd 'lJ ~d :.~ c~ r.~
and applied through a h~aat exchanger 112 where it is cooled.
Lthylane is supplied via l3.ns 111 whaxe .lt is mixed with th~
flfgluent from the tirs~ r~ractor, ~lae. Praf~a; ably, the ethylene is supplied to the r~:actar effluent prier to cr~olinc~ In order to faci.litat~ distribution c~f the ethylene thr.~ughout the lis~ui,d bsn~ene. l3aeirably, the cooling axt~ap is carried ~ut en reduced the temperature of tha feed mir,t.ure supplied to the sac~nd re~G-tor 11~ t.o a value about the sa~we set the lnls~ t~em~~raturra to the first reaator 10.9. The average temp~raturs in the seoond xsactor normmlly wii,l be about the same as that of the First reactor.
fibs preas~ara will, of necssgi:y, be somewhat lc~wsr i.n order to provide for sufgi~isnt pr8eeure gradient to aGCnmodate tl~w through the cyst~m. fibs effluent Pram ths~ secaad $enctar 114 is supplied along with athylenr~ provided via ~llaae 117 to a seacnd interntage .cooling unit li9 where the shares mixtura~to third rga~ctar Z20 ie aga~.n aaa~,ed to a te~nnera~ture about ~qusl to the inlet tempsrature for they first twc~ reactors.
The outgun. frs~~n xeact~or~ 120 is supplied via line 12~ to a downstream aeparatian and processing unit 12~. rn unit 12d, eth~lbenzene ie e~parat~~ad and withdrawn ae the produet of the alkylation plant. Typicalz~,~, $r.hy.lbanzene will b~ used ae the charge to a dehy~3roganation system syatsm~where It undergoes catal.ytia d~shYdroget~ation in the pxod~acl:ion of etyren~. Normal ly, banza»a arid ~thyl~ena will ba aeparat~d in unit 12~ and re-Cyclad tt~r ue9 in the al3cylst.i~n presses. Heeviaar palystt~yl~~
bsn~ena~ may ba t~canamlky~.ated with ben~ena to produce additional ethyl.ben$en~~ as described previouei.y.
d is cvnvantianal., n ataichlometria exreasa of b~n~ena to athylvns Will be supplied in the shares ntoaJc to ttW a~yl~.-~.60-tion reactors in drderr tee anisanca seelectivigy ~t~r mona~axkylati~n.
~psrmtion of the seactara tc provide lictuid phtsae alkylation undar relat3v~ly mild ca~nditiona~'nc~t only minimixea the acylena ps'oducad in the alkYlatian s;aaction hut a1s~ enables the use of a somewhat lows b~nxena,/ethYl~na mol~a reties than is usually the aaao. Usually, the benxan~/~thyi~na mole retie ~'i13, be 5sI ctc lager and mare pr~farably~ ~sl or less. ~ant~na~athYlane mole a~atioa as low as about ~ a 1 maY be at~ploy~d . Ratiog graa,t~r than ssi can bs used. Howcvurr tfaera is usually little incan$ive to uea e~ttrtmely h3.gh ratios and, ~t~ a practical lita,tte~, the bans;~ne/ethylsng mole gatio will a~ldom ~~cCaad i.5sl. ~h~
bens:ene/ethylation mole ratios referred to ~tbave era with raapant to the avsrall system and fcr a mufti-atag~ raaotian ayatern such ae dapiated in the drasaS.ngr Ch~ banzene/athyl,cne ratio of the fa$d to sash stage gill be 1~~a than the saverail ratio.
the aanount of ethylenedaolubilixed its the bettzt~sne charges to each reactor atag~ ~ail1 cepand in part upon the number ~f reac%~or stagers employed. Prafea't~blyr at least 3 reactor staa~ee, ae illu$trat.ed, Mill be head. . Additional s:'eaatas~ stages may tie prov idad, a~'thoug~ th~ total number of atag~a sxsarmally c~il1 not ~xcead 6. t~x~ferablyr the pr~aauxa in each raactior~ stags nrsd the eraount of ethylene eeyplied that~in ia..auoh as to Provide at lenat l~mole percent of ettsyler~~ sclubilizea in th~ banaanae ~$ua,lly at ieaa~t 2 mote percent of ethyl~ns vaill ba acalt~bilixad in the charge i:o ~sxah reactor. ~s~ferablyr unlasis n ggaat 9na~nY
reactor stages era amplolred, ~aaually the amsaunt of ethylene ~alu~
bi.liaud in the liquid banxene ghas$a of each sr~actoz~ e~lll tie at least 4 mole percent.
The following Table V gives exemplary conditions and re-action parameters for a multistage system of the type shown in the drawing, but employing five reaction stages. As will be dis-cussed below, Table V also illustrates a preferred mode of opera-Lion when going from one reaction stage to the next, as well as advantages accruing in the use of multiple reaction stages in the liquid phase alkylation process where the reaction pressure, while above the vapor pressure of the aromatic substrate, is below the vapor pressure of the alkylating agent at the reaction conditions.
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N t0 U~
~ U1 ~-i N m C lC1 In Table V, the idealized reactor conditions for the ethylation of benzene with ethylene are illustrated in columns 2-5. The benzene feed rate in moles per unit time to each of the reaction stages is set forth in column 6. Benzene conversion for each reaction stage is indicated in column 7 and the ethylene feed rate in moles per unit time to each reaction zone is set forth in column 8. The last column presents the mole ratio of benzene to ethylene at the input of each of the successive reac-tion stages. The data presented in Table V is based upon an idealized case, assuming that benzene conversion is about 90$ of theoretical based upon the feed rate of ethylene which, of course, is the limiting reactant.
At the temperature and pressure conditions depicted in Table V, the solubility of ethylene in the liquid aromatic com-pounds involved, including benzene, ethylbenzene and polyethyl-benzene, is about 10 mole percent. The ethylene feed to the first reaction stage is controlled in order to provide an amount of ethylene near the solubility limit. Within the first reaction zone, 0.36 moles of benzene are converted and the effluent from the first reaction zone, after cooling as described previously, is applied to the second reaction zone. The aromatic feed to the second reaction zone will comprise about 3.64 moles of benzene and about 0.36 moles of ethylbenzene and,polyethylbenzenes per unit time. Since the ethylated product can serve to solubilize the ethylene at the reaction conditions, the ethylene feed rate can be retained at 0.4 moles per unit time, resulting in a de-creased benzene conversion rate. The relationships described above prevail when going from one reaction stage to the next, re-sulting in a decreased mole ratio of benzene to ethylene in each succeeding reaction stage and an increased benzene conversion rate although in the idealized case presented in Table V, the interstage injection of ethylene is maintained constant. This need not necessarily be the case. For example, the ethylene feed rate can be increased or decreased slightly from one stage to the next, or alternatively decreased and increased, so long as the overall progression across the multistage system is one of decreasing benzene/ethylene ratio with the attendant increase in benzene conversion. By way of an example of a progressively de-creasing feed rate and with reference to the system depicted in Table V, the ethylene feed rate can be progressively decreased by 2-3$ when going from one reaction stage to the next while retain-ing the characteristic of a decreasing benzene/ethylene ratio as depicted in the Table. If the ethylene feed rate is increased when going from one stage to the next, it is preferred to main-taro the ethylene below the solubility limit at the temperature and pressure conditions involved in order to avoid multiphase flow through the catalyst bed.
Multistage ethylation of benzene may also be carried out in accordance with the present invention employing isothermal reaction zones. Isothermal reactors can take the form of shell and tube type heat exchangers with the alkylation catalyst depo-sited within the tubes and with a heat transfer medium circulated through the shell surrounding the catalyst filled tubes. The heat exchange medium will, of course, be supplied through the reactors at rates to maintain a relatively constant temperature across each reaction stage. In this case, interstage cooling will be unnecessary, although it will be preferred to inject ethylene at the front of each reaction stage.
As discussed previously, it is desirable in accordance with certain aspects of the invention to employ a dehydration step. Aromatic conversion reactions such as alkylation or tran-salkylation may be carried out in the vapor phase or in the liquid phase. Intermediate pore sized zeolites such as ZSM-5 (pore size of about 6 angstroms) are effective catalysts for vapor phase alkylation or transalkylation where movement of aro-matic molecules in the gas phase through the molecular sieve net-work takes place by energy vibration. Somewhat larger pore size molecular sieves appear to be necessary to provide effective catalysts for processes such as the liquid phase alkylation of benzene. Thus, benzene, which has a kinetic diameter of about 5.9 angstroms, will enter into the molecular sieve network of an intermediate pore size molecular sieve such as ZSM-5. However,' the resulting alkylated product such as ethylbenzene or cumene will not readily move through the molecular sieve channels by liquid phase displacement.
The zeolite molecular sieves employed in the present invention and having a pore size greater than 6.5 angstroms are effective catalysts under relatively mild conditions for liquid phase hydrocarbon aromatic hydrocarban conversion reactions such as the ethylation of benzene or the transalkylation of polyethyl-benzene. As noted previously, conversion takes place at relati-~~?~~)~~~

vely loco temperature conditions of less than 300°C, about 275°C
or less. In fact, effective ethylation or transalkylation reac-tions can take place in the liquid phase over larger pore size zeolite molecular sieves employed in the present invention at temperatures within the range of about 200°-250° C and such reac-tions can be accomplished without undesirable side reactions as may be encountered in vapor phase reaction conditions. The pressure on the reaction zone in which the conversion reaction takes place is necessarily above the vapor pressure of the aroma-tic substrate involved. Preferably, the reaction zone pressure is at least 50 psi above the vapor pressure. Thus, in the ethy-lation of benzene at 225°C to produce ethylbenzene, the reactor pressure preferably would be about 350 psig or more. In general, the reactor pressure may range from about 250-1000 psig.
While, as noted previously, water can be tolerated in vapor phase reactions, it does under the high temperature con-ditions encountered in vapor phase reaction, effect the dealumi-nation of the catalyst with a corresponding decrease in proton-aced sites and a reduction in acidic catalyst activity. One would not expect a similar effect to be encountered under the relatively mild conditions of liquid phase aromatic conversion reactions and, in fact, it appears that dealumination in the pre-sence of water does not occur under these conditions, However, by dehydrating the :Feed stream to the liquid phase reaction zone, the aging quality o:E the catalyst is substantially increased. In fact, by decreasing the water content to well below 300 ppm, a value normally tolerated in vapor phase reactions without sub-n~ s/~ r~ ~ s~ ~i~
YJ ~..J ".~ LY

stantial adverse impact upon catalyst aging quality, the aging quality of the catalyst in the liquid phase condition is materially enhanced.
As nested previously, the molecular sieves employed in the present invention have pore sizes greater than 6.5 angstroms which readily accomodate movement of molecules within the molecu-lar sieve network by a liquid phase displacement mechanism. The preferred zeolite molecular sieves, zeolites Y and beta, have a pore size within the range of 7.0-7.5 angstroms. The catalysts are not acid extracted to effect dealumination. In additional experimental work carried out relative to the invention, such larger pore size zeolite molecular sieves ware employed as cata-lysts in the liquid phase transalkylation of diethylbenzene. Two zeolite Y catalysts were used in this experimental work. Zeolite Y is characterized by a three dimensional channel system and has an average pore size of about 7.3. Zeolite Y catalysts have silica/alumina ratios of less than 10, usually about 5-6.
In this experimental work, a mixture of benzene and a .
polyethylbenzene overheads fraction resulting from a vapor phase alkylation process was passed into a reactor containing a zeolite Y catalyst. The reactor was operated in a flooded, upflow mode configuration and under a pressure of about 30 psig to maintain the aromatic compounds in the liquid phase. The flow rate was sufficient to provide a space velocity (~HSV) based upon the total feed of about 3 hr-1. The weight ratio of benzene to polyethylbenzene overheads was about 4. A typical feed com-position employed in the experimental work is shown in Table VI.

4'1 !~ ,..
~r/~;'a~~~

Table VI
Non-Aromatic 0.01 Benzene 78.87 Toluene 0.00 Ethylbenzene 3.40 p-Xylene 0.01 m-Xylene 0.02 Styrene 0.03 o-Xylene 0.04 Cumene 1.67 n Propylbenzene 3.30 m-Ethyltoluene 0.15 p-Ethyltoluene 0.05 .

o-Ethyltoluene 0.04 1,3,5-Trimethylbenzene 0.07 1,2,4-Trimethylbenzene 0.20 sec-Butylbenzene 0.39 1,2,3-Trimethylbenzene 0.32 m-Diethylbenzene 7.03 n-Butylbenzene 0:29 p,o-Diethylbenzene 3.90 Heavies ~ 0.49 The water content of the feed was about 300 ppm. The temperature was progressively increased during the run as necessary to maintain the transalkylation reaction at 70~ conver-sion of diethylbenzene. Over the first 11 days of the experimen-tal run, the charge of wet feedstock was first passed into a de-hydrator filled with a molecular sieve desiccant. The output from the dehydrator was passed into the reaction zone. The dried feedstock was estimated to have a water content of about 30 ppm.
Thereafter, and over the remainder of the run, the wet feed was applied directly to the reactor.
The results of the experimental work employing one of the zeolite Y catalysts axe set forth in FIGURE 12. In FIGURE
12, curves 126 and 127 are graphs of temperature, T in °C
necessary to maintain 70~ diethylbenzene conversion plotted on the ordinant versus the age, A, of the catalyst (the duration of the run) in days plotted on the abscissa. As indicated by curve 126 for the dried feed, the catalyst exhibited an aging quality of about 1.8°C per day (average daily increase in temperature necessary to maintain 70~ conversion). Curve 127 of FIGURE 12 indicates the aging quality of the catalyst when the feed stream was diverted from the dryer so that the wet feed containing about 300 ppm water was directly applied to the alkyaltion reactor. As indicated by curve 127, the aging characteristic for the catalyst more than doubled to about 3.9°C/day.
Similar experimental work was carried out using another zeolite Y catalyst in the liquid-phase transalkylation of poly-ethylbenzene. The feedstock employed here was the same as the feedstock used in the experimental work described immediately above. In this case, the temperature was adjusted as necessary to maintain the transalkylation reaction at 80$ conversion of di-ethylbenzene. The space velocity was the same as employed in the previous zeolite Y experimental work, 3 hr-1 (LHSV?. The trans-alkylation reaction was carried out at a pressure of 300 psig in order to maintain the aromatic hydrocarbons in the liquid phase.
In this test, the wet feed, containing about 300 ppm, was ini-tially applied to the reaction vessel containing the zeolite Y.
At the conclusion of nine days, the feedstream was first directed to a dehydrator containing silica gel which extracted water from the feed stream to provide a water content of about 30 ppm. The run was then continued for an additional 11 days during which de-hydrated feed was supplied to the reaction zone. The results of the experimental work carried out for the second zeolite Y are illustrated in FIGURE 13, in which curves 129 and 130 are graphs of temperature T, in °C, required for 80$ diethylbenzene conver-sion of the wet and dry feeds, respectively, plotted against catalyst age in days. As shown in FIGURE 13, the initial wet feed caused a very rapid deactivation of the catalyst. However, at the conclusion of the wet feed injection, the introduction of dry feed not only materially reduced the catalyst deactivation rate but actually enhanced the activity of the catalyst.
In addition to transalkylation, this embodiment of the invention may be employed in the liquid phase alkylation of aro-matic substrates. As indicated earlier, a particularly important liquid phase alkylation reach on is the ethylation of benzene under mild liquid phase conditions which results in little or no xylene make. Other liquid phase alkylation reactions may be em-ployed, particularly those involving the use of C2-C,~ alkylating agents. For example, this embodiment of the invention may be employed in the reaction of propylene and benzene to produce cumene. Usually, alkylating agents will take the form of ole-fins. However, other al)cylating agents such as alkynes, alkyl halides, alcohols, ethers and esters .as disclosed, for example, in the aforementioned patent to Pollitzer, may be employed.
Also, aromatic substrates other than benzene, for example, toluene or xylene, may also be subject to liquid phase alkylation in accordance with the invention.
As noted previously, dehydration of an aromatic feed-stock in accordance with the invention may be carried out in con-junction with the use of a zeolite molecular sieve other than zeolite Y having a pore size within the range of 7.0-7.5 angstroms. Specifically, zeolite beta is an effective alkylation catalyst under the mild temperature conditions involved in liquid phase alkylation. The preferred zeolite beta alkylation cata-lysts are, as described earlier, of a very low sodium content, less than 0.04 weight percent and preferably less than 0,02 weight percent expressed as Na20, and have a high surface area,, at least 600 m2/g. The zeolite beta has a silica/alumina ratio of about 20-25.
Zeolite omega, referred to previously in regard to its use in alkylation and transalkylation is disclosed in U.S. Patent No. 4,241,036 to Flanigan et al., along with its x-ray diffrac-tion pattern and basic procedures for its preparation. Zeolite omega is synthesized by the hydrothermal digestion of a reaction mixture comprising silica, alumina, an alkali or alkaline earth metal oxide or hydroxide, specifically sodium hydroxide, and an a ry r~ ~.
~~~~~,._~~
_72._ alkylammonium component, specifically tetramethylammonium hydroxide.
The chemical composition of zeolite omega in its pre-ferred form may be characterized as follows:
[xR2+yM2n0):A1203:5-20Si02:0-8H20 wherein:
x has a value ranging from 0-0.7 and the sum of x and y ranges from 0.5-1.5;
R represents hydrogen, ammonium, alkylammonium or mix-tures thereof;
M is a metal compound, usually an alkali metal compound such as sodium; and n is the valence of M.
For a further description of zeolite omega and its preparation, reference is made to the aforementioned U.S. Patent 4,241,036 to Flanigan et al., the entire disclosure of which is incorporated herein by reference.
In the alkylation of benzene, both the benzene feedsto~ck and the ethylene for other alkylating agent) may contain water.
Accordingly, it will be preferred to pass both the benzene and the ethylene through a dehydration unit. While separate dehydra-toys may be used for the two feed components, usually the ethy-lene and benzene will be mixed in the mixed feed stream and applied to the dehydration unit and from there to the liquid phase reactor.
In the application of this aspect of the invention to the transalkylation of polyalkylbenzenes, all or part of the feed ~~~t~~~v to the transalkylation reactor may be subject to a prior dehydra-tion step. Normally, the transalkylation of polyalkyl benzenes will be carried out in conjunction with a prior alkylation step with the output from the alkylation reactor being subjected to one or more separation steps resulting in a polyalkylbenzene com-ponent which is combined with benzene and then passed to the transalkyaltion reaction zone operated under liquid phase dispro-portionation conditions as discussed previously.
Where the invention involves a transalkylation process carried taut in conjunction with a liquid phase alkylation step proceeded by a dehydration step as described above, the poly-alkylbenzene component supplied to the transalkylation reactor should be substantially free of water and it normally will be necessary to subject only the benzene component to a dehydration step. However, in other applications of the invention, it may be necessary to subject the polyalkylbenzene component to a dehydra-tion step prior to its introduction to the transalkylation reac-tor. For example, the transalkylation procedure may be carried out in combination with a vapor phase alkylation procedure which tolerates water in the feed stream or in which water is addi-tionally added, for example, as disclosed in the aforementioned patent to Barger et al. In this case, it may be necessary to subject both the polyethylbenzene component and the benzene com-ponent to dehydration prior to passage to the transalkylation reactor.
Having described specific embodiments of the present invention, it will be understood that modification thereof may be suggested to those skilled in the arty and it is intended to cover all such modifications as fall within the scope of the appended claimso

Claims (56)

1. In a process for the production of ethylbenzene, the steps comprising:

a) supplying a feed stock containing benzene into a reaction zone containing a molecular sieve aromatic alkylation catalyst;

b) supplying an ethylating agent to said reaction zone;

c) operating said reaction zone at temperature and pressure conditions to maintain said benzene in the liquid phase and causing ethylation of said benzene substrate by said ethylating agent in the presence of said catalyst to produce an alkylated product comprising a mixture of ethylbenzene and polyethylbenzenes;

d) recovering said alkylated product from said reaction zone and supplying said product to a benzene separation zone comprising a first prefractionation column and a second benzene fractionation column connected in series with said first fractionation column;

e) operating said first fractionation column to produce a light overheads fraction which includes benzene and a heavier liquid bottoms fraction containing benzene, ethylbenzene, and polyethylbenzene which is supplied to said benzene fractionation column;

f) operating said second benzene fractionation column to provide an overheads fraction containing benzene and a higher boiling bottoms fraction comprising an ethylbenzene and polyethylbenzene mixture;

g) supplying said higher boiling fraction from said second benzene fractionation column to an ethylbenzene separation zone;

h) operating said ethylbenzene separation zone to produce a second lower boiling fraction comprising ethylbenzene and a higher boiling fraction comprising heavier polyethylbenzene fraction;

i) supplying at least a portion of said polyethylbenzene fraction including substantially all of the diethylbenzene and triethylbenzene in said polyethylbenzene fraction to a transalkylation reaction zone containing a molecular sieve transalkylation catalyst;

j) supplying said benzene to said transalkylation zone;

k) operating said transalkylation reaction zone under temperature and pressure conditions to maintain said benzene in the liquid phase and effective to cause disproportionation of said polyethylbenzene fraction to arrive at a disproportionation product having a reduced polyethylbenzene aromatic content and an enhanced ethylbenzene content; and 1) supplying at least a portion of said disproportionation product to said second benzene fractionation column;

2. The process of Claim 1, further comprising prior to step k) in Claim 1, supplying the output from said transalkylation zone to a third separation zone and operating said third separation zone to produce a lower boiling fraction comprising a benzeneethyl benzene component and a higher boiling fraction comprising a polyethylbenzene component and supplying said benzeneethylbenzene component to said first recited separation zone in accordance with step k) of Claim 1.

3. The method of Claim 2, wherein said ethylating agent is ethylene.

4. The method of Claim 1, wherein said alkylation catalyst comprises zeolite beta.

5. The method of Claim 4, wherein said alkylating agent is ethylene.

6. The method of Claim 5, wherein said transalkylation catalyst is zeolite Y.

7. In an process for the production of ethylbenzene, the steps comprising:

a) supplying a benzene feed stock into an alkylation reaction zone containing a molecular sieve aromatic alkylation catalyst;

b) supplying an ethylating agent to said reaction zone;

c) operating said reaction zone at temperature and pressure conditions to maintain said benzene in the vapor phase and causing ethylation of said benzene by said ethylating agent in the presence of said catalyst to produce an alkylated product comprising a mixture of ethylbenzene and polyethylbenzenes;

d) recovering said alkylated product from said reaction zone and supplying said product to a benzene separation zone comprising a first prefractionation column and a second benzene fractionation column connected in series with said first fractionation column;

e) operating said first fractionation column to produce a light overheads fraction which includes benzene and a heavier liquid bottoms fraction containing benzene, ethylbenzene, and polyethylbenzene which is supplied to said benzene fractionation column;

f) operating said second benzene fractionation column to provide an overheads fraction containing benzene and a higher boiling bottoms fraction comprising an ethylbenzene and polyethylbenzene mixture.

g) supplying said higher boiling fraction from said second benzene fractionation column to an ethylbenzene separation zone;

h) operating said ethylbenzene separation zone to produce a second lower boiling fraction comprising ethylbenzene and a higher boiling fraction comprising a heavier polyethylbenzene fraction;

i) supplying at least a portion of said polyethylbenzene fraction to a transalkylation reaction zone containing a molecular sieve transalkylation catalyst;

j) supplying benzene to said transalkylation zone;

k) operating said transalkylation reaction zone at an average temperature at least 50°C below the average temperature of said alkylation reaction zone and under temperature and pressure conditions to maintain said benzene in the liquid phase and effective to cause disproportionation of said polyethylbenzene fraction to arrive at a disproportionation product having a reduced polyethylbenzene content and an enhanced monoethylbenzene content; and 1) supplying at least a portion of said disproportionation product to said benzene separation zone.

8. The process of Claim 7, wherein said transalkylation reaction zone is operated at an average temperature at least 100°C below the average temperature of said alkylation reaction zone.

9. In a process for the production of ethylbenzene, the steps comprising:

a) supplying a benzene feed stock and an ethylating agent into a primary reaction zone containing an aromatic alkylation catalyst comprising zeolite beta;

b) operating said reaction zone under temperature and pressure conditions to maintain said benzene feedstock in the liquid phase to effect ethylation of said benzene feed stock to produce an alkylated product comprising an ethylbenzene and polyethylbenzene mixture;

c) recovering said alkylated product from said reaction zone and supplying said product to a benzene separation zone comprising a first prefractionation column and a second benzene fractionation column connected in series with said first fractionation column;

d) operating said first fractionation column to produce a light overheads fraction which includes benzene and a heavier liquid bottoms fraction containing benzene, ethylbenzene, and polyethylbenzene which is supplied to said benzene fractionation zone; and e) operating said second benzene fractionation column to provide an overheads fraction containing benzene and a higher boiling bottoms fraction comprising an ethylbenzene and polyethylbenzene mixture.

f) supplying said higher boiling fraction from said second benzene fractionation column to an ethylbenzene separation zone;

g) operating said ethylbenzene separation zone to produce a second lower boiling fraction comprising ethylbenzene and a second higher boiling fraction comprising a heavy polyethylbenzene fraction containing no more than 5 wt. % ethylbenzene;

h) supplying said polyethylbenzene fraction from said ethylbenzene column to a transalkylation reaction zone containing a transalkylation catalyst;

i) supplying benzene to said transalkylation reaction zone;

j) operating said transalkylation reaction zone under temperature and pressure conditions to effect liquid phase disproportionation of said polyethylbenzene fraction to arrive at a disproportionation product having a reduced polyethylbenzene content and an enhanced ethylbenzene content; and k) supplying at least a portion of said disproportionation product to said benzene separation zone.

10. The method of Claim 9, further comprising the step of supplying said disproportionation product to a separation zone, operating said zone to produce a lower boiling fraction comprising benzene and ethylbenzene and a higher boiling polyethylbenzene fraction and supplying said lower boiling fraction to said benzene separation zone in accordance with step i).

11. The method of Claim 9, wherein said transalkylation catalyst comprises a molecular sieve selected from the group consisting of zeolite Y.

12. The method of Claim 11, wherein said transalkylation zone is operated at a space velocity (LHSV) based upon benzene and alkyl benzenes which is less than the space velocity (LHSV) in said primary reaction zone based upon benzene.

13. The method of Claim 12, wherein said transalkylation zone space velocity is less than one half the space velocity of said primary alkylation zone.

14. A molecular sieve comprising hydrogen zeolite beta having a surface area based upon the crystalline structure of said zeolite beta of at least 650 m2/g.

15. A molecular sieve according to Claim 14, wherein said molecular sieve comprises hydrogen zeolite beta in combination with a binder and wherein the surface area of said zeolite beta based upon the composite of said molecular sieve including said binder is at least 450 m2/g.

16. A molecular sieve according to Claim 14, wherein said zeolite beta has a sodium content of less than 0.04 wt. % Na2O .

17. A molecular sieve comprising hydrogen zeolite beta having a sodium content in the crystalline structure of said zeolite beta of less than 0.02 wt. % Na2O.

18. In a process for the preparation of a hydrogen zeolite beta derived by modification of an alkali metal containing zeolite beta synthesized by the hydrothermal digestion of a reaction mixture comprising silica, alumina, an alkali metal oxide, and an organic templating agent, the steps comprising:
(a) treating said synthesized zeolite beta with an ion exchange medium to protonate a portion of the active sites in said zeolite by exchanging said alkali metal;

(b) calcining said ion exchanged zeolite at a temperature within the range of 400°-700°C for a period within the range of 210 hours;

(c) treating said calcined zeolite with an ion exchange medium to protonate an additional portion of the active sites in said zeolite by exchanging said alkali metal;

(d) mixing said ion exchanged zeolite from step (c) with a binder to produce a mulled zeolite binder mixture;

(e) pelletizing said zeolite binder mixture and drying the resulting pellets.

19. The process of Claim 18, wherein the treatment of step (a) comprises submersing said synthesized zeolite beta in an ion exchanged medium, separating said zeolite beta from said ion exchange medium, and submersing said separated zeolite beta in a second ion exchange medium.

20. The process of Claim 19, wherein the treatment of step (c) comprises submersing said synthesized zeolite beta in an ion exchange medium, separating said zeolite beta from said ion exchange medium, and submersing said separated zeolite beta in a second ion exchange medium.

21. The process of Claim 18, wherein the ion exchange medium employed in steps (a) and (c) is an aqueous solution of an ammonium salt.

22. The process of Claim 21, wherein said ammonium salt employed in steps (a) and (c) is ammonium nitrate.

23. In a process for the preparation of a hydrogen zeolite beta derived by modification of sodium zeolite beta synthesized by the hydrothermal digestion of a reaction mixture comprising silica, alumina, sodium oxide, and an organic templating agent, the steps comprising:

(a) treating said synthesized zeolite beta with an ion exchange medium comprising an aqueous solution of an ammonium salt to exchange a portion of the active sites in said zeolite beta by replacing sodium with ammonium ions;

(b) calcining said ion exchanged zeolite beta at a temperature and for a period of time sufficient to remove at least a portion of the templating agent from said zeolite and arrive at a surface area based upon the crystalline structure of said zeolite beta which is at least twice the surface area of said zeolite beta in the assynthesized form;

(c) treating said calcined zeolite with an ion exchange medium comprising an aqueous solution of an ammonium salt to exchange another portion of the active sites in said zeolite beta by replacing sodium with ammonium ions;

(d) mixing said ion exchanged zeolite from step (c) with a binder to produce a mulled zeolite/binder mixture;

(e) pelletizing said zeolite/binder mixture and drying the resulting pellets;

(f) calcining said pellets at a temperature and for a time sufficient to decompose ammonium ions on the active sites of said zeolite to hydrogen.

24. The process of Claim 23, wherein the treating step of step (a) is carried out by contacting said synthesized zeolite beta with said ion exchange medium for a period of at least two hours.

25. The process of Claim 24, wherein said treating step (a) comprises submersing said synthesized zeolite beta in a first portion of said ion exchange medium for a period of at least one hour, separating said zeolite beta from said first portion of said ion exchange medium, and submersing said separated zeolite beta in a second portion of said ion exchange medium for a period of at least one hour.

26. In a process for the liquid phase alkylation of aromatic compounds, the steps comprising:

(a) supplying a feedstock containing an aromatic substrate into a reaction zone and into contact with an alkylation catalyst comprising zeolite beta having a surface area of at least 650 m2/gram of crystalline zeolite beta;

(b) supplying a C2C4 alkylating agent to said reaction zone;

(c) operating said reaction zone at temperature and pressure conditions to maintain said aromatic substrate in the liquid phase causing alkylation of said aromatic substrate by said alkylating agent in the presence of said catalyst; and (d) recovering alkylated aromatic substrate from said reaction zone.

27. The process of Claim 26, wherein said zeolite beta has a sodium content of less than 0.02 wt. % expressed as Na2O.

28. The process of Claim 26, wherein said aromatic substrate comprises benzene and said alkylating agent is an ethylating agent or a propylating agent.

29. The process of Claim 28, wherein said alkylating agent is ethylene.

30. In a process for the liquid phase alkylation of aromatic compounds, the steps comprising:

(a) supplying a feedstock containing an aromatic substrate into a reaction zone and into contact with an alkylation catalyst comprising zeolite beta having a sodium content of less than 0.02 wt. % expressed as Na2O;

(b) supplying a C2C4 alkylating agent to said reaction zone;

(c) operating said reaction zone at temperature and pressure conditions to maintain said aromatic substrate in the liquid phase and causing alkylation of said aromatic substrate by said alkylating agent in the presence of said catalyst; and (d) recovering said alkylated aromatic substrate from said reaction zone.

31. The process of Claim 30, wherein said zeolite beta has a sodium content of less than 0.01 wt.% expressed as Na2O.

32. The process of Claim 30, wherein said alkylating agent is ethylene and said reaction zone is operated under temperature and pressure conditions under which the xylene make based upon the amount of ethylbenzene produced is no more than 0.05 wt.%.

33. In a process for the production of ethylbenzene by the liquid phase ethylation of benzene, the steps comprising:
(a) supplying a benzene feedstock into a reaction zone and into contact with an alkylation catalyst comprising zeolite beta;
(b) supplying an ethylating agent to said reaction zone;
(c) operating said reaction zone at temperature and pressure conditions providing a pressure in said reaction zone at least 50 psi above the vapor pressure of said benzene and causing monoethylation of said benzene in the liquid phase by said ethylating agent in the presence of said catalyst, and under which conditions the xylene make based upon the amount of ethylbenzene produced is no more than 0.03 wt.%; and (d) recovering ethylbenzene from said reaction zone.

34. The process of Claim 33, wherein said reaction system comprises a plurality of series connected reaction stages containing said zeolite beta alkylation catalyst, supplying said benzene feedstock to the first of said series connected reaction stages and passing the effluent from said first reaction stage to at least a second of said reaction stages and separately supplying said ethylating agent to each of said reaction stages.

35. The method of Claim 34, wherein said ethylating agent is ethylene.

36. The process of Claim 35, further comprising the step of cooling the effluent from said first reaction stage prior to supplying said effluent to said second reaction stage and mixing the ethylene supplied to said second reaction stage with the effluent from said first reaction stage prior to said cooling step.

37. In a liquid phase aromatic conversion process, the steps comprising:
(a) supplying a feedstock containing at least onearomatic compound and having water entrained therein to a dehydration zone;
(b) within said dehydration zone removing water from said feedstock to provide a dehydrated feedstock having water content of no more than 100 ppm;
(c) supplying said dehydrated feedstock into a reaction zone containing a zeolite molecular sieve catalyst having a pore size greater than 6.5 angstroms and selected from the group consisting of zeolite Y and zeolite beta;

(d) operating said reaction zone at temperature and pressure conditions to maintain said aromatic compound in the liquid phase and sufficient to cause said aromatic conversion reaction to proceed in the presence of said catalyst; and (e) recovering converted product from said reaction zone.

38. The process of Claim 37, wherein said dehydrated feedstock has a water content of no more than 50 ppm.

39. The process of Claim 37, wherein said catalyst has a pore size within the range of 7.0-7.5 angstroms.

40. The process of Claim 37, wherein said catalyst comprises zeolite beta.

41. The process of Claim 37, wherein said reaction zone is operated at a pressure at least 50 psi above the vapor pressure of said aromatic compound.

42. In a process for the liquid phase alkylation of aromatic compounds, the steps comprising:

(a) supplying a feedstock containing an aromatic substrate and having water entrained therein to a dehydration zone;

(b) within said dehydration zone removing water from said feedstock to provide a dehydrated feedstock having a water content of no more than 100 ppm;

(c) withdrawing said dehydrated aromatic substrate from said dehydration zone and passing said substrate into a reaction zone containing an alkylation catalyst comprising a zeolite molecular sieve having a pore size greater than 6.5 angstroms;

(d) supplying an alkylating agent to said reaction zone;

(e) operating said reaction zone at temperature and pressure conditions to maintain said aromatic substrate in the liquid phase and under temperature conditions to cause alkylation of said aromatic substrate by said alkylating agent in the presence of said catalyst; and (f) recovering an alkylated aromatic substrate from said reaction zone.

43. The process of Claim 42, wherein said aromatic substrate comprises benzene and said alkylating agent is an ethylating agent or a propylating agent.

44. The process of Claim 42, wherein the output from said reaction zone comprises a mixture of monoalkyl and polyalkyl benzenes further comprising subjecting said output from said reaction zone to at least one separation step resulting in a polyalkyl benzene component and supplying said polyalkyl benzene component and benzene to a transalkylation reaction zone containing a transalkylation catalyst comprising a zeolite molecular sieve having a pore size greater than 6.5 angstroms and operating said transalkylation reaction zone under temperature and pressure conditions to effect liquid phase disproportionation of said polyalkyl benzene component in the presence of said transalkyation catalyst to arrive at a disproportionation product having a reduced polyalkyl benzene content and an enhanced monoalkyl benzene component.

45. The process of Claim 42, wherein said catalyst has a pore size within the range of 7.0-7.5 angstroms.

46. The process of Claim 45, wherein said alkylating agent is an olefin.

47. The process of Claim 45, wherein said alkylating agent is ethylene.

48. The process of Claim 47, wherein said dehydrated feedstock has a water content of no more than 50 ppm.

49. The process of Claim 47, wherein said alkylation catalyst comprises zeolite beta.

50. In a process for the transalkylation of a feedstock having water entrained therein and containing a mixture of a polyalkylbenzene component and benzene to produce a disproportionation product comprising a monoalkylbenzene, the steps comprising:

(a) subjecting at least a portion of said feedstock to a dehydration step to extract water therefrom and provide a feedstock having a total water content of no more than 100 ppm.

(b) passing said dehydrated feedstock into a transalkylation reaction zone containing a zeolite molecular sieve transalkylation catalyst having a pore size greater than 6.5 angstroms and selected from the group consisting of zeolite beta and zeolite Y;

(c) operating said transalkylation reaction zone under temperature and pressure conditions to effect liquid phase disproportionation of said polyalkylbenzene component in the presence of said transalkylation catalyst to arrive at a disproportionation product having a reduced polyalkylbenzene content and an enhanced monoalkylbenzene content; and (d) withdrawing said disproportionation product from said reaction zone.

51. The process of Claim 50, wherein said polyalkylbenzene component is produced in an alkylation reaction zone in which benzene is reacted with an alkylating agent to produce an effluent including a mixture of monoalkyl and polyalkyl benzenes and said feedstock comprises a polyalkylbenzene component separated from said mixture and benzene.

52. The process of Claim 51, wherein said alkylation reaction zone is operated under conditions to effect vapor phase alkyaltion of said benzene.

53. The process of Claim 51, wherein said alkylating agent is an ethylating agent or a propylating agent.

54. The process of Claim 53, wherein said transalkylation catalyst comprises zeolite beta.

55. The process of Claim 54, wherein said transalkylation catalyst comprises zeolite Y.

56. In a process for the production of ethylbenzene by liquid phase alkylation of benzene with ethylene in a multistage reaction system comprising at least three series-connected adiabatic reaction stages containing an alkylation catalyst and including an initial adiabatic reaction stage, at least one intermediate adiabatic reaction stage, and a final adiabatic reaction stage, the steps comprising:

operating said reaction stages under adiabatic reaction conditions of temperature and pressure effective to cause alkylation of said benzene with ethylene in the presence of said catalyst, said pressure being above the vapor pressure of benzene and below the vapor pressure of ethylene at said temperature conditions;

supplying a feedstock comprising benzene and ethylene to the initial adiabatic reaction stage in relative amounts to provide a first mole ratio of benzene to ethylene;

withdrawing an effluent comprising a mixture of benzene and ethylated benzene reaction product from each reaction stage preceding said final reaction stage and supplying said effluent to the next succeeding reaction stage;

supplying ethylene along with the effluent mixture to the next succeeding reaction stage to provide an overall progression across said multi-stage reaction system of a decreasing mole ratio of benzene to ethylene in an amount to provide a final mole ratio of benzene to ethylene for said final reaction stage which is less than said first mole ratio of benzene to ethylene supplied to said initial reaction stage;

cooling the effluent mixture from a next preceding reaction stage prior to supplying said effluent mixture to the next succeeding reaction stage while mixing the ethylene supplied to the next succeeding reaction stage with the effluent mixture from the preceding reaction stage prior to said cooling; and withdrawing an effluent product from said final reaction stage comprising a mixture of benzene and ethylated benzene.