Crystalline silicate particle having an aluminum-containing outer shell

Claim 2

A particle, comprising an inner portion and an outer portion disposed as a shell around said inner portion wherein said outer portion has the same crystal structure as said inner portion, said inner portion comprising an intermediate pore size crystalline silicate having a silica:alumina mole ratio greater than about 200:1, and said outer portion having a silica:alumina mole ratio of less than about 100:1 and wherein said particle is prepared by a process comprising: (1) initiating crystallization in a crystallization medium substantially free of aluminum to produce the intermediate pore size crystalline silicate; (2) adding a source of aluminum to said crystallization medium; and (3) crystallizing onto said crystalline silicate the isostructural outer portion which comprises alumina.

Claim 3

A particle, comprising an inner portion and an outer portion disposed as a shell around said inner portion wherein said outer portion has the same crystal structure as said inner portion, said inner portion comprising an intermediate pore size crystalline silicate having a silica:alumina mole ratio greater than about 200:1, and said outer portion having a silica:alumina mole ratio of less than about 100:1 and wherein said particle is prepared by a process comprising: (1) crystallizing the intermediate pore size crystalline silicate from a first reaction medium substantially free of aluminum; (2) removing said crystalline silicate from said first reaction medium; (3) adding said crystalline silicate to a second reaction medium comprising sources of aluminum, and (4) crystallizing the isostructural, alumina containing outer layer onto said crystalline silicate.

Claim 4

A particle, comprising an inner portion and an outer portion disposed as a shell around said inner portion wherein said outer portion has the same crystal structure as said inner portion, said inner portion comprising an intermediate pore size crystalline silicate having a silica:alumina mole ratio greater than about 200:1, and said outer portion having a silica:alumina mole ratio of less than about 100:1 and wherein said particle is prepared by a process comprising: (1) crystallizing the intermediate pore size crystalline silicate from a first reaction medium substantially free of aluminum; (2) removing said crystalline silicate from said first reaction medium; (3) adding said crystalline silicate to a second reaction medium comprising sources of aluminum, and (4) crystallizing the isostructural, alumina containing outer layer onto said crystalline silicate.

Claim 5

The particle of claim 2 having the X-ray diffraction pattern of ZSM-5.

Claim 6

The particle of claim 2 having the X-ray diffraction pattern of ZSM-11.

Claim 7

A process for preparing a particle, comprising an inner portion and an outer portion disposed as a shell around said inner portion wherein said outer portion has the same crystal structure as said inner portion, said inner portion comprising an intermediate pore size crystalline silicate having a silica:alumina mole ratio greater than about 200:1, and said outer portion having a silica:alumina mole ratio of less than about 100:1, comprising: (1) initiating crystallization in a crystallization medium substantially free of aluminum to produce the intermediate pore size crystalline silicate; (2) adding a source of aluminum to said crystallization medium; and (3) crystallizing onto said crystalline silicate the isostructural outer portion which comprises alumina.

Claim 8

A process for preparing a particle, comprising an inner portion and an outer portion disposed as a shell around said inner portion wherein said outer portion has the same crystal structure as said inner portion, said inner portion comprising an intermediate pore size crystalline silicate having a silica:alumina mole ratio greater than about 200:1, and said outer portion having a silica:alumina mole ratio of less than about 100:1, comprising: (1) initiating crystallization in a crystallization medium substantially free of aluminum to produce the intermediate pore size crystalline silicate; (2) adding a source of aluminum to said crystallization medium; and (3) crystallizing onto said crystalline silicate the isostructural outer portion which comprises alumina.

Claim 9

The process of claim 5 wherein the reaction mixture comprises sources of organic cation, silica and hydroxide ion.

Claim 10

The process of claim 6 wherein the source of hydroxide ion is sodium hydroxide.

Claim 11

The process of claim 6 wherein in step (2) the organic ion to SiO 2 mole ratio is reduced from that in step (1).

Claim 12

The process of claim 7 wherein in step (2) the hydroxide content is lower than that in step (1).

Claim 13

The process of claim 5 wherein step (3) is performed at a temperature of from about 100° C. to 120° C. and at a pH of from 10 to 12.

Claim 14

The process of claim 5 wherein said crystalline silicate is silicalite having a silica:alumina mole ratio greater than about 200:1 and said isostructural outer portion has a silica:alumina mole ratio less than about 100:1.

Claim 15

A process for preparing a particle, comprising an inner portion and an outer portion disposed as a shell around said inner portion wherein said outer portion has the same crystal structure as said inner portion, said inner portion comprising an intermediate pore size crystalline silicate having a silica:alumina mole ratio greater than about 200:1, and said outer portion having a silica:alumina mole ratio of less than about 100:1, comprising: (1) crystallizing the intermediate pore size crystalline silicate from a first reaction medium substantially free of aluminum; (2) removing said crystalline silicate from said first reaction medium; (3) adding said crystalline silicate to a second reaction medium comprising sources of aluminum, and (4) crystallizing the isostructural, alumina containing outer layer onto said crystalline silicate.

Claim 16

A process for preparing a particle, comprising an inner portion and an outer portion disposed as a shell around said inner portion wherein said outer portion has the same crystal structure as said inner portion, said inner portion comprising an intermediate pore size crystalline silicate having a silica:alumina mole ratio greater than about 200:1, and said outer portion having a silica:alumina mole ratio of less than about 100:1, comprising: (1) crystallizing the intermediate pore size crystalline silicate from a first reaction medium substantially free of aluminum; (2) removing said crystalline silicate from said first reaction medium; (3) adding said crystalline silicate to a second reaction medium comprising sources of aluminum, and (4) crystallizing the isostructural, alumina containing outer layer onto said crystalline silicate.

Claim 17

The process of claim 12 wherein the first and second reaction mixtures comprise sources of organic cation, silica and hydroxide ion.

Claim 18

The process of claim 13 wherein the source of hydroxide ion is sodium hydroxide.

Claim 19

The process of claim 13 wherein in step (3) the organic ion to SiO 2 mole ratio is reduced from that in step (1).

Claim 20

The process of claim 14 wherein in step (3) the hydroxide content is lower than that in step (1).

Claim 21

The process of claim 12 wherein step (4) is performed at a temperature of from about 100° C. to 120° C. and at a pH of from 10 to 12.

Claim 22

The process of claim 12 wherein said crystalline silicate is silicalite having a silica:alumina ratio greater than about 200:1 and said isostructural outer portion has a silica:alumina mole ratio less than about 100:1.

Claim 23

The composition of claim 2 wherein the silica:alumina mole ratio of said inner portion is greater than about 500:1.

Claim 24

The composition of claim 2 wherein the silica:alumina mole ratio of said inner portion is greater than about 1000:1.