Back to results
US 4,211,886 AGranted
Manufacture of benzene, toluene and xylene
AssigneeMobil Oil Corporation
InventorsSamuel A. Tabak, Roger A. Morrison
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeMobil Oil Corporation
InventorsSamuel A. Tabak, Roger A. Morrison
Estimating the term…
Benzene, toluene and xylene are produced in high yield from aromatic naphtha by a processing technique which combines (1) high temperature isomerization of eight carbon atom aromatics over a catalyst having relatively low activity and constrained access to the internal pore surface and (2) processing of heavy single ring aromatics of nine or more carbon atoms together with toluene under dealkylation/transalkylation conditions. The effluents of the two reactions are blended for processing through separation and recovery equipment. The unique chemistry of the isomerization stage results in splitting off alkyl side chains of two or more carbon atoms while retaining methyl groups attached to aromatic rings. Because of these reaction characteristics, full range reformate is advantageously added to the isomerizer charge for conversion to methyl benzene and redistribution of methyl groups to the thermodynamic equilibrium values.
A new use of known apparatus for simultaneously isomerizing xylenes and converting ethylbenzene to products readily separable by distillation from the mixture of C.sub.8 aromatics by contacting a mixture of C.sub.8 aromatics and hydrogen with a catalyst at conversion conditions of elevated temperature and pressure in a loop comprising an isomerization reactor for the contact aforesaid, distillation means for separating C.sub.8 aromatics from lower boiling and higher boiling hydrocarbons, means to transfer hydrocarbon effluent of said isomerization reactor to said distillation means, means for introducing fresh feed C.sub.8 aromatics to said loop, a xylene separator for recovery of para xylene, means for transfer of mixed C.sub.8 aromatics to said xylene separator, and means to transfer C.sub.8 aromatics lean in para xylene from said xylene separator to said isomerization reactor, which new use comprises contacting, in the isomerization reactor of said known apparatus, a vapor phase mixture of hydrogen, said C.sub.8 aromatics lean in para xylene and fresh charge material containing alkyl benzenes of more than eight carbon atoms with a zeolite catalyst at a temperature of about 800.degree.-1000.degree. F., a pressure of 150 to 300 pounds per square inch and a weight hourly space velocity between 1 and about 200;
In a process for isomerizing the xylene content of a charge mixture of eight carbon atom aromatic hydrocarbon compounds which mixture contains xylene, and ethylbenzene by contact at conversion conditions with a catalyst comprising a zeolite having a silica/alumina ratio greater than 12 and a constraint index of 1 to 12, the improvement resulting in conversion of ethylbenzene to benzene and conversion of higher alkyl benzenes to benzene, toluene and xylene which comprises including in the charge mixture alkyl aromatics of more than eight carbon atoms maintaining the conversion temperature at about 800.degree. F. to 1000.degree. F., using such catalyst comprising a zeolite of reduced acid activity such that less than 2 weight percent of xylene is converted to compounds other than xylene when contacted with said catalyst at 900.degree. F. 200 psig and LHSV of 5, separating toluene and C.sub.9.sup.+ aromatics from the products of contact with said zeolite catalyst, reacting said C.sub.9.sup.+ aromatics in admixture with hydrogen by contacting the same with a porous acidic solid catalyst at a temperature of 550.degree. to 1000.degree. F., and adding the product of said contact with porous acidic solid catalyst to the product of contact with said zeolite catalyst.
A process for the manufacture of aromatic hydrocarbon which comprises subjecting a hydrocarbon naphtha to catalytic reforming under conditions to convert naphthenes to aromatic hydrocarbons including xylenes, ethylbenzene and alkylbenzenes of more than eight carbon atoms in a reformate reaction product, mixing at least that portion of said reformate boiling above C.sub.8 aromatics with a recycle stream hereafter defined which contains xylenes and ethylbenzene, contacting the resultant mixture at 800.degree.-1000.degree. F. with a zeolite catalyst having a constraint index of 1 to 12, a silica/alumina ratio above about 12 and reduced acid activity such that less than 2 weight percent of xylene is converted to compounds other than xylene when contacted with said catalyst at 900.degree. F., 200 psig and LHSV of 5, whereby to isomerize xylene content of said mixture and to convert ethylbenzene and alkylbenzenes of more than eight carbon atoms to benzene, toluene and xylene, distilling the product of said contacting to separate compounds of less than eight carbon atoms and compounds of more than eight carbon atoms from a C.sub.8 fraction, recovering at least one xylene isomer from said C.sub.8 fraction to provide a stream lean in said recovered isomer and containing xylenes and ethylbenzene, mixing said lean stream with said reformate as the recycle stream aforesaid, reacting said compounds of more than eight carbon atoms in admixture with hydrogen by contacting said admixture with a porous acidic solid catalyst at a temperature of 550.degree. to 1000.degree. F. and adding the product of said contact with porous acidic solid catalyst to the product of contact with said zeolite catalyst.
In a process for manufacture of at least one of benzene, toluene and xylene from a hydrocarbon naphtha containing carbocyclic single ring components by catalytic reforming of the naphtha under conditions to dehydrogenate carbocyclic rings with production of a reformed naphtha containing benzene, toluene, xylenes, ethylbenzenes and alkylbenzenes of more than eight carbon atoms and thereafter separating benzene, toluene or xylene from the reformed naphtha, the improvement which comprises contacting said reformed naphtha or a fraction thereof containing alkylbenzenes of more than eight carbon atoms and hydrogen at 800.degree.-1000.degree. F. with a zeolite catalyst having a constraint index of 1 to 12, a silica/alumina ratio above about 12 and reduced acid activity such that less than 2 weight percent of xylene is converted to compounds other than xylene when contacted with said catalyst at 900.degree. F., 200 psig and LHSV of 5, whereby to convert ethylbenzene and alkylbenzenes of more than eight carbon atoms to benzene, toluene and xylene, and recovering at least one of benzene, toluene or xylene as a product.
Dependencies are inferred from the claim text.