~™ IIINMNNIIMIIIINIIINNII (19) J European Patent Office Office europeen des brevets (11) EP 0 879 809 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) |nt. CI.6: C07C 15/073, C07C 2/66 25.11.1998 Bulletin 1998/48 //B01J29/035 (21) Application number: 98109045.9 (22) Date of filing: 19.05.1998 (84) Designated Contracting States: • Merrill, James T. AT BE CH CY DE DK ES Fl FR GB GR IE IT LI LU Katy, Texas 77449 (US) MCNLPTSE • Butler, James R. Designated Extension States: Houston, Texas 77059 (US) AL LT LV MK RO SI (74) Representative: (30) Priority: 21.05.1997 US 861206 Leyder, Francis et al c/o Fina Research S.A. (71) Applicant: FINA TECHNOLOGY, INC. Dept. Brevets Dallas, Texas 75206 (US) Zone Industrielle C 7181 Seneffe (Feluy) (BE) (72) Inventors: • Ghosh, Ashim Kumar Houston, Texas 77059 (US) (54) Gas phase alkylation-liquid phase transalkylation process (57) Process for the production of ethylbenzene by aromatic fraction is subject to disproportionation to pro- alkylation over a silicalite alkylation catalyst with the vide a reduced diethylbenzene content and an subsequent transalkylation of diethylbenzene with the enhanced ethylbenzene content. A specific monoclinic alkylation catalyst and conditions selected to retard silicalite alkylation catalyst has a silica/alumina ratio of xylene production and also heavies production. A feed- at least 300 and has a crystal size of less than one stock containing benzene and ethylene is applied to a micron. multi-stage alkylation reaction zone having a plurality of series-connected catalyst beds containing a pentasil molecular sieve alkylation catalyst which is silicalite of a predominantly monoclinic symmetry having a silica/alu- mina ratio of at least 275. The feedstock is supplied to the alkylation reaction zone to cause gas-phase ethyla- tion of benzene at a flow rate to provide a space velocity of benzene over the catalyst to produce a xylene con- centration in the product of about 600 ppm or less based upon the ethylbenzene content. Periodically the space velocity may be increased to a value which is greater than the space velocity associated with a mini- mum concentration of diethylbenzene in the alkylation product such that diethylbenzene production is enhanced while minimizing any attendant transalkyla- tion reactions within the alkylation reaction zone. This is accompanied by a relatively low xylene content in the product, specifically no more than 600 based <7> ppm upon O the ethylbenzene in the product. The output from the CO alkylation reactor is applied to an intermediate recovery <7> zone for the separation and recovery of ethylbenzene with the recovery of a polyalkylated aromatic compo- co nent which is supplied along with benzene to a o transalkylation reaction zone where the polyalkylated Q_ LU Printed by Xerox (UK) Business Services 2.16.6/3.4 1 EP 0 879 809 A1 2 Description passed to a separation system in which ethylbenzene product is recovered, with the recycle of polyethylben- FIELD OF THE INVENTION zenes to the alkylation reactor where they undergo transalkylation reactions with benzene. The Dwyer cat- This invention involves an aromatic alkyla- s alysts are characterized in terms of those having a con- tion/transalkylation process involving vapor phase ethyl- straint index within the approximate range of 1-12 and ation of benzene over a silicalite aromatic alkylation include, with the constraint index in parenthesis, ZSM-5 catalyst under conditions providing enhanced diethyl- (8.3), ZSM-1 1 (8.7), ZSM-12 (2), ZSM-35 (4.5), ZSM-38 benzene production and diminished xylene production (2), and similar materials. and followed by a subsequent liquid phase transalkyla- 10 A silicalite is a well-known alkylation catalyst. For tion over a relatively large pore size zeolite transalkyla- example, U.S. Patent No. 4,520,220 to Watson et al dis- tion catalyst. closes the use of silicalite catalysts having a average crystal size of less than 8 microns and a silica/alumina BACKGROUND OF THE INVENTION ratio of at least about 200 in the ethylation of a aromatic 15 substrate such as benzene or toluene to produce ethyl- Aromatic conversion processes which are carried benzene or ethyltoluene, respectively. As disclosed in out over molecular sieve catalyst are well known in the Watson et al, the alkylation procedure can be carried chemical processing industry. Such aromatic conver- out in a multi-bed alkylation reactor at temperatures rag- sion reactions include the alkylation of aromatic sub- ing from about 350°-500°C. and, more desirably, about strates such as benzene to produce alkyl aromatics 20 400°-475°C, with or without a steam co-feed. The reac- such as ethylbenzene, ethyltoluene, cumene or higher tor conditions in Watson et al are such as provide gen- aromatics and the transalkylation of polyalkyl benzenes erally for vapor phase alkylation conditions. to monoalkyl benzenes. Typically, a alkylation reactor Another procedure employing silicalite and involv- which produces a mixture of mono- and poly- alkyl ben- ing the ethylation of benzene under vapor phase reac- zenes may be coupled through various separation 25 tion conditions coupled with the recycle of stages to a downstream transalkylation reactor. Such polyethylbenzene containing products back to the alkylation and transalkylation conversion processes can alkylation reactor is disclosed in U.S. Patent No. be carried out in the liquid phase, in the vapor phase or 4,922,053 to Wagnespack. Here, alkylation is carried under conditions in which both liquid and vapor phases out at temperatures generally in the rage of 370°C. to are present. 30 about 470°C. and pressures ranging from atmospheric Alkylation and transalkylation reactions may occur up to about 25 atmospheres over a catalyst such as sil- simultaneously within a single reactor. For example, icalite or ZSM-5. The catalysts are described as being where various series-connected catalyst beds are moisture sensitive and care is taken to prevent the pres- employed in a alkylation reactor as described below, it is ence of moisture in the reaction zone. The alkyla- a conventional practice to employ interstage injection of 35 tion/transalkylation reactor comprises four series the aromatic substrate between the catalyst beds, connected catalyst beds. Benzene and ethylene are which tends to enhance transalkylation reactions within introduced into the top of the reactor to the first catalyst the alkylation reactor. For example, in the ethylation of bed coupled by recycle of a polyethylbenzene fraction to benzene with ethylene to produce ethylbenzene, the the top of the first catalyst bed as well as the interstage alkylation product within the reactor includes not only 40 injection of polyethylbenzene and benzene at different ethylbenzene but also polyethylbenzene, principally points in the reactor. diethylbenzene with reduced amounts of triethylben- Another process involving the use of a silicalite as a zene, as well as other alkylated aromatics such as alkylation catalyst involves the alkylation of an alkylben- cumene and butylbenzene. The interstage injection of zene substrate in order to produce dialkylbenzene of a the ethylene results not only further in elation reactions 45 suppressed ortho isomer content. Thus, as disclosed in but also transalkylation reactions where, for example, U.S. Patent No. 4,489,214 to Butler et al, silicalite is benzene and diethylbenzene undergo transalkylation to employed as a catalyst in the alkylation of a produce ethylbenzene. Thus, even though a separate monoalkylated substrate, toluene or ethylbenzene, in transalkylation reactor is connected downstream order to produce the corresponding dialkylbenzene, through a series of separation stages, it is the accepted so such as toluene or diethylbenzene. Specifically dis- practice to minimize polyalkylation within the alkylation closed in Butler et al is the ethylation of toluene to pro- reactor in order to facilitate the subsequent treatment duce ethyltoluene under vapor phase conditions at and separation steps. temperatures raging from 350°-500°C. As disclosed in An example of vapor phase alkylation is found in Butler, the presence of ortho ethyltoluene in the reaction U.S. Patent No. 4,107,224 to Dwyer. Here, vapor phase 55 product is substantially less than the thermodynamic ethylation of benzene over a zeolite catalyst is accom- equilibrium amount at the vapor phase reaction condi- plished in a down flow reactor having four series con- tions employed. nected catalyst beds. The output from the reactor is U.S. Patent No. 4,185,040 to Ward et al discloses a 2 3 EP 0 879 809 A1 4 alkylation process employing a molecular sieve catalyst use of separate alkylation and transalkylation reaction of low sodium content which is said to be especially zones, with recycle of the transalkylated product to a useful in the production of ethylbenzene from benzene intermediate separation zone. In the Barger process, and ethylene and cumene from benzene and propylene. the temperature and pressure conditions are adjusted The Na20 content of the zeolite should be less than 0.5 5 so that the alkylation and transalkylation reactions take wt. %. Examples of suitable zeolites include molecular place in essentially the liquid phase. The transalkylation sieves of the X, Y, L, B, ZSM-5, and omega crystal catalyst is a aluminosilicate molecular sieve including X- types, with steam stabilized hydrogen Y zeolite being type, Y-type, ultrastable-Y, L-type, omega type and mor- preferred. Specifically disclosed is a steam stabilized denite type zeolites with the latter being preferred. The ammonium Y zeolite containing about 0.2% Na20. Var- w catalyst employed in the alkylation reaction zone is a ious catalyst shapes are disclosed in the Ward et al pat- solid phosphoric acid containing material. Aluminosili- ent. While cylindrical extrudates may be employed, a cate alkylation catalysts may also be employed and particularly preferred catalyst shape is a so-called "trilo- water varying from 0.01 to 6 volume percent is supplied bal" shape which is configured as something in the to the alkylation reaction zone.