Manufacture of lower aromatic compounds
AssigneeMobil Oil Corporation
InventorsJames A. Brennan, Roger A. Morrison
Life of this patent
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Abstract
Certain acidic heterogeneous catalysts produce large yields of benzene, toluene and xylene from alkyl aromatics of at least nine carbon atoms by a mechanism different from the classical disproportionation reaction characteristic of acid catalysts. These catalysts are characterized by a zeolite of the ZSM-5 type or zeolite ZSM-12 or zeolite ZSM-21. The reaction has the unique function of providing aliphatic by-products of higher molecular weight than is to be expected by splitting side chains from benzene rings. Typically, aromatic mixtures so derived from such charge stocks have unusually low content of ethyl benzene, thus greatly simplifying separation of xylene isomers.
Claims33
In the manufacture of gasoline and concurrent production of chemical grade aromatic compounds of eight or less carbon atoms by catalytic reforming of naphtha and using part of the reformate for each purpose, the improvement resulting in higher quality gasoline of lower "heavy end" content, which comprises fractionating a catalytic reformate to provide a light reformate containing most of the C.sub.8 and lighter components of the reformate and a heavy reformate which contains no more than 20 weight percent of xylenes, blending said light reformate with other motor fuel components to provide a finished gasoline, contacting said heavy reformate with a catalyst characterized by an effective amount of type ZSM-5 zeolite, zeolite ZSM-12 or zeolite ZSM-21 under conditions to remove from alkyl aromatics side chain alkyl groups of greater than one carbon atom and produce therefrom aliphatic hydrocarbons containing more carbon atoms than the side chains so removed and to produce more xylenes then contained in said heavy reformate and to also produce benzene and toluene, said conditions being about 550.degree. to about 1000.degree.F., about 100 to about 2000 pounds per square inch, about 0.5 to 10 mols of hydrogen per mol of hydrocarbon and a weight hourly space velocity between about 0.1 and about 200 unit weights of hydrocarbon per unit weight of said zeolite in the catalyst per hour, and recovering from the product of contacting said heavy reformate with said catalyst aliphatic hydrocarbons having a greater number of carbon atoms than the side chains of alkyl aromatics in said heavy reformate and at least one aromatic hydrocarbon of eight or less carbon atoms in an amount greater than quantity of said aromatic hydrocarbon in said heavy reformate.
A process for producing aromatic compounds of six to eight carbon atoms from an aromatic hydrocarbon charge predominantly higher in molecular weight than eight carbon atom aromatics, without substantial formation of heavier (350.degree.F.+) aromatics through conventional disproportionation or transalkylation reactions, which process comprises fractionating an aromatic naphtha to remove therefrom a substantial amount of C.sub.8 aromatics together with lower boiling components of said naphtha and thereby produce said charge with a catalyst characterized by an effective amount of type ZSM-5 zeolite, zeolite ZSM-12 or zeolite ZSM-21 under conditions to remove from alkyl aromatics side chain alkyl groups of greater than 1 carbon atom and produce therefrom aliphatic hydrocarbons containing more carbon atoms than the side chains so removed and to produce more xylenes than contained in said heavy reformate and to also produce benzene and toluene, said conditions being about 550.degree. to about 1000.degree.F., about 100 to about 2000 pounds per square inch, about 0.5 to 10 mols of hydrogen per mol of hydrocarbon and at a weight hourly space velocity between about 0.1 and about 200 unit weights of hydrocarbon per unit weight of said zeolite in the catalyst per hour and recovering from the product of contacting said charge with said catalyst aliphatic hydrocarbons having a greater number of carbon atoms than the side chains of alkyl aromatics in said heavy reformate and at least one aromatic hydrocarbon of eight or less carbon atoms in an amount greater than quantity of said aromatic hydrocarbon in said heavy reformate.
Dependencies are inferred from the claim text.