Active zeolite catalysts of improved stability

Claim 2

In an acid-catalyzed reaction using a catalyst comprising a zeolite having a silica/alumina ratio greater than 12 and a constraint index of 1 to 12, the improvement which comprises steaming said zeolite in its fresh state under controlled conditions of temperature, time and steam partial pressure so as to initially increase the α-activity of said catalyst and produce a steamed catalyst having a peak α-activity, and subsequently reduce the α-activity from said peak α-activity to an α-activity substantially the same as the α-activity of said fresh catalyst and no more than 25% below the initial α-activity of said fresh catalyst, said steamed catalyst having enhanced stability over said fresh catalyst.

Claim 3

A process according to claim 1 wherein said zeolite is ZSM-5.

Claim 4

A process according to claim 1 wherein said catalyst comprises one or more metal promoters.

Claim 5

A process according to claim 3 wherein said catalyst has said metal promoters included on it prior to the steaming procedure.

Claim 6

A process according to claim 3 wherein said catalyst has said metal promoters included on it after the steaming procedure.

Claim 7

A process according to claim 1 wherein said silica/alumina ratio is no less than 20.

Claim 8

A process according to claim 6 wherein said silica/alumina ratio is about 40.

Claim 9

A process according to claim 6 wherein said silica/alumina ratio is about 70.

Claim 10

In a process for isomerizing the xylene content of a charge mixture of eight carbon atom aromatic hydrocarbon compounds which mixture contains xylenes 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 which comprises using as said catalyst a steamed zeolite and maintaining a conversion temperature of about 500° F. to about 1000° F., said zeolite having been steamed prior to said contact at a temperature and pressure and for a period of time so as to initially increase the α-activity of said catalyst and produce a steamed catalyst having a peak α-activity, and subsequently reduce the α-activity from said peak α-activity to an α-activity substantially the same as the α-activity of said fresh catalyst and no less than 75% of the initial α-activity of the fresh, unsteamed zeolite, said steamed catalyst having enhanced stability over said fresh catalyst.

Claim 11

In a process for isomerizing the xylene content of a charge mixture of eight carbon atom aromatic hydrocarbon compounds which mixture contains xylenes 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 which comprises using as said catalyst a steamed zeolite and maintaining a conversion temperature of about 500° F. to about 1000° F., said zeolite having been steamed prior to said contact at a temperature and pressure and for a period of time so as to initially increase the α-activity of said catalyst and produce a steamed catalyst having a peak α-activity, and subsequently reduce the α-activity from said peak α-activity to an α-activity substantially the same as the α-activity of said fresh catalyst and no less than 75% of the initial α-activity of the fresh, unsteamed zeolite, said steamed catalyst having enhanced stability over said fresh catalyst.

Claim 12

A process according to claim 9 wherein said zeolite is ZSM-5.

Claim 13

A process according to claim 9 wherein said catalyst comprises one or more metal promoters.

Claim 14

A process according to claim 9 wherein said catalyst has said metal promoters included on it prior to the steaming procedure.

Claim 15

A process according to claim 9 wherein said catalyst has said promoters included on it after the steaming procedure.

Claim 16

A process according to claim 9 wherein the reaction temperature is 550° F. to 900° F.

Claim 17

A process according to claim 9 wherein said charge mixture comprises at least 5-45% ethylbenzene and 10-75% m-xylene with the remainder of said charge mixture comprising p-xylene, o-xylene, other aromatics and non-aromatics.