Composite zeolite

Claim 2

A catalyst composition comprising a crystalline modified-silica zeolite having a constraint index of from 1 to 12 overlying a silica core having substantially the same crystalline structure as the modified-silica zeolite.

Claim 3

A catalyst composition comprising a crystalline modified-silica zeolite having a constraint index of from 1 to 12 overlying a silica core, in which the silica core is a silica polymorph of analogous structure to the modified-silica zeolite, so that the silica core alone and the complete catalyst display substantially the same x-ray diffraction patterns.

Claim 4

A catalyst composition comprising a crystalline modified-silica zeolite having a constraint index of from 1 to 12 overlying a silica core, in which the silica core is a silica polymorph of analogous structure to the modified-silica zeolite, so that the silica core alone and the complete catalyst display substantially the same x-ray diffraction patterns.

Claim 5

A composition as claimed in claim 1, in which the silica core is a silica polymorph having, after calcination in air for at least one hour at 600° C., a mean refractive index of 1.39±0.01 and a specific gravity at 25° C. of 1.70±0.05.

Claim 6

A composition as claimed in claim 3, in which the silica core is a silica polymorph having an X-ray powder diffraction pattern in which the six strongest d-values are: 11.1±0.2 Å 10.0±0.2 Å 3.85±0.07 Å 3.82±0.07 Å 3.76±0.05 Å 3.72±0.05 Å

Claim 7

A composition as claimed in claim 3, in which the silica polymorph has a pore diameter in the range of from 5 to 6 Ångstrom units and a pore volume of 0.18 ml/g, determined by adsorption.

Claim 8

A composition as claimed in claim 3, in which the silica polymorph has, following calcination in air for at least an hour at 600° C., an adsorptive capacity for water vapour at 23° C. and a water vapour pressure of 4.6 mm Hg of less than 1 wt. %, an infra-red spectrum which exhibits a substantial absence of absorption in the region of 3700-3100 cm -1 , and an X-ray powder diffraction pattern containing at least the following d-values: 11.1±0.2 10.0±0.2 9.75±0.1 3.85±0.04 3.82±0.04 3.71±0.02 3.62±0.02 and showing an absence of reflections intermediate the reflections corresponding to d-spacings of 3.82±0.04 Å and 3.71±0.02 Å.

Claim 9

A composition as claimed in claim 1, in which the silica core is a silicate resulting from thermal treatment at a temperature of from 200° C. to 600° C. for from 1 to 48 hours of a crystal metal organosilicate having a composition, in its anhydous state, in terms of mole ratios of oxides as follows: 0.9±0.2(xR.sub.2 O+(1-x)M.sub.2/n O):<0.005Al.sub.2 O.sub.3 :>1 where M is sodium or sodium in combination with tin, calcium, nickel or zinc, R is a tetraalkylammonium and x is a number greater than 0 but not exceeding 1, the organosilicate having the following characteristic X-ray diffraction lines: ______________________________________ Interplanar spacing d (Å) Relative Intensity ______________________________________ 11.1 ± 0.2 s 10.0 ± 0.2 s 7.4 ± 0.15 w 7.1 ± 0.15 w 6.3 ± 0.1 w 6.04 ± 0.1 w 5.97 5.56 ± 0.1 w 5.01 ± 0.1 w 4.60 ± 0.08 w 4.25 ± 0.08 w 3.85 ± 0.07 vs 3.71 ± 0.05 s 3.04 ± 0.03 w 2.99 ± 0.02 w 2.94 ± 0.02 w ______________________________________

Claim 10

A composition as claimed in claim 1, in which the silica core has the following characteristic X-ray diffraction pattern: ______________________________________ Interplanar spacing d (Å) Relative Intensity ______________________________________ 11.2 ± 0.2 m 10.1 ± 0.2 m 6.73 ± 0.2 w 5.75 ± 0.1 w 5.61 ± 0.1 w 5.03 ± 0.1 w 4.62 ± 0.1 w 4.39 ± 0.08 w 3.86 ± 0.07 vs 3.73 + 0.07 m 3.49 ± 0.07 w 3.07 ± 0.05 w 3.00 2.01 ± 0.02 w ______________________________________

Claim 11

A composition as claimed in claim 1, in which the silica core is a silica having the following significant lines in its X-ray pattern: ______________________________________ Interplanar spacing d (Å) Relative Intensity ______________________________________ 11.9 ± 0.2 s 10.2 ± 0.2 m 4.76 ± 0.1 w 4.29 ± 0.08 vs 3.87 ± 0.07 vs 3.66 ± 0.07 w 3.49 ± 0.07 w 3.38 ± 0.07 m 3.20 ± 0.06 w 3.05 ± 0.05 w 2.64 ± 0.03 w ______________________________________

Claim 12

A composition as claimed in claim 1, in which the silica core alone and the catalyst composition display the significant x-ray diffraction lines of a ZSM-5 zeolite.

Claim 13

A composition as claimed in claim 1 in which the modified-silica zeolite has a formula expressed in terms of the mole ratios of oxides as follows: M.sub.2/n O:W.sub.2/x O:YSiO.sub.2 :zH.sub.2 O wherein M is at least one cation of valence n, W is the modifying element of valence x, Y is at least 5 and z is from 0 to 40.

Claim 14

A composition as claimed in claims 11, in which the modifying element W is Al, B, Ga, Cr, Fe, V, Ti, Be, As or a combination of two or more of those elements.

Claim 15

A composition as claimed in claim 11, in which the modified-silica zeolite is of the formula (expressed in terms of mole ratios of oxides): M.sub.2/n O:W'.sub.2 O.sub.3 :Y'SiO.sub.2 :zH.sub.2 O wherein W' is one or more of Al, Ga and B, Y' is 20-5000, and M, n and z are as defined in claim 11.

Claim 16

A composition as claimed in claim 11, in which the mean ratio of silicon to modifying element W or W' in the complete catalyst (expressed in terms of mole ratios of their oxides) is from 20 to 500.

Claim 17

A composition as claimed in claim 1, in which the silica core has a crystallite size of greater than 0.1μ mean diameter.

Claim 18

A composition as claimed in claim 15, in which the silica core has a crystallite size of from 0.5μ to 20μ mean diameter.

Claim 19

A composition as claimed in claim 1, in which the weight ratio of the silica core to the overlying modified-silica zeolite (expressed in terms of the weight ratio of the SiO 2 core to the SiO 2 in the reaction mixture for the modified-silica zeolite) is from 1:1 to 10:1.

Claim 20

A composition as claimed in claim 17, in which the weight ratio of the silica core to the overlying modified-silica is from 1:1 to 4:1.

Claim 21

A process for the preparation of a composite zeolite comprising a silica core with an overlying modified-silica zeolite having a tetrahedral silica network substituted by a modifying element, in which process preformed particles of silica are placed in a crystallisation gel for the modified-silica zeolite comprising a silica source and a source of the modifying element and the crystallisation gel is maintained under appropriate reaction conditions to bring about formation on the silica particles of a modified-silica zeolite having a constraint index of from 1 to 12, the silica having substantially the same crystalline structure as the modified-silica zeolite.

Claim 22

A process for the preparation of a composite zeolite comprising a silica core with an overlying modified-silica zeolite having a tetrahedral silica network substituted by a modifying element, in which process preformed particles of silica are placed in a crystallisation gel for the modified-silica zeolite comprising a silica source and a source of the modifying element and the crystallisation gel is maintained under appropriate reaction conditions to bring about formation on the silica particles of a modified-silica zeolite having a constraint index of from 1 to 12, the silica having substantially the same crystalline structure as the modified-silica zeolite.

Claim 23

A process as claimed in claim 19, in which the crystallisation gel also contains an organic template compound.

Claim 24

A process as claimed in claim 19, in which the weight ratio of the preformed silica particles to SiO 2 in the silica source is from 1:1 to 10:1.

Claim 25

A process as claimed in claim 19, in which the crystallisation gel and silica particles are maintained at a temperature of from 100 to 2000 C for from 1 to 30 days.

Claim 26

A catalyst composition comprising silica core particles having formed thereon an overlying crystalline modified-silica zeolite with a constraint index of 1 to 12, the modified-silica zeolite and the silica core having substantially the same crystalline structure.

Claim 27

A catalyst composition comprising silica core particles having formed thereon an overlying crystalline modified-silica zeolite with a constraint index of 1 to 12, the modified-silica zeolite and the silica core having substantially the same crystalline structure.

Claim 28

A process for the preparation of a composite zeolite comprising a silica core with an overlying modified-silica zeolite having a tetrahedral silica network substituted by a modifying element selected from the class consisting of Al, B, Ga, Cr, Fe, V, Ti, Be, As, or mixtures thereof, in which process preformed particles of silica are placed in a crystallisation gel for the modified-silica zeolite comprising a silica source and a source of the modifying element and the crystallisation gel is maintained under appropriate reaction conditions to bring about formation on the silica particles of a modified-silica zeolite having a constraint index of from 1 to 12, the silica having substantially the same crystalline structure as the modified-silica zeolite.

Claim 29

A process for the preparation of a composite zeolite comprising a silica core with an overlying modified-silica zeolite having a tetrahedral silica network substituted by a modifying element selected from the class consisting of Al, B, Ga, Cr, Fe, V, Ti, Be, As, or mixtures thereof, in which process preformed particles of silica are placed in a crystallisation gel for the modified-silica zeolite comprising a silica source and a source of the modifying element and the crystallisation gel is maintained under appropriate reaction conditions to bring about formation on the silica particles of a modified-silica zeolite having a constraint index of from 1 to 12, the silica having substantially the same crystalline structure as the modified-silica zeolite.