Synthesis of zeolites of faujasite structure

Claim 2

A process for the preparation of zeolites belonging to the faujasite structural class and exhibiting a Si:Al ratio higher than 1, said process comprising first forming a reaction mixture which has a pH higher than 10 and contains water, a source of tetravalent silicon, a source of trivalent aluminum, a source of hydroxide ions in the form of a strong inorganic or organic base and a structural agent ST so as to produce an alumino silicate gel having the composition to permit its crystallization into a compound of the faujasite structural class, and the gel obtained is then kept at a temperature not exceeding 150° C. and at a pressure of at least equal to the autogenous pressure of said gel for a sufficient period to effect the crystallization of said gel into a precursor of the zeolite consisting of the zeolite with the structural agent ST trapped in its cavities and said precursor is subjected to a calcination to destroy said structuring agent ST and to produce the zeolite, and wherein the structuring agent ST consists of at least one compound MC selected from the group consisting of carbon-containing macrorings and macropolyrings which contain in the rings heteroatoms selected from the group consisting of oxygen, nitrogen, silicon, and sulfur, and which contain 10 to 24 atoms per ring.

Claim 3

The process according to claim 1, wherein the quantity of structuring agent ST in the reaction mixture intended to form the gel is such as to make the molar ratio ST:Al III ranged from 0.1 to 4.

Claim 4

The process according to claim 1, wherein the ingredients making up the reaction mixture giving rise to the aluminosilicate gel are employed in such quantities as to give said gel, in terms of molar ratios, a composition such that Si IV :Al III =2 to 20, OH:Al III =0.5 to 8, ST:Al III =0.1 to 4 and H 2 O:Al III =40 to 200.

Claim 5

The process according to claim 3, wherein said composition is such that Si IV :Al III =4 to 10, OH - :Al III =1 to 6, ST:Al III =0.1 to 1 and H 2 O:Al III =50 to 150.

Claim 6

The process according to claim 1, wherein the structuring agent ST consists of at least one compound MC chosen from the group consisting of a) crown ethers whose ring contains 10 to 24 atoms and comprises solely oxygen atoms as heteroatoms, at least 4 in number, b) compounds derived from the crown ethers defined under a) by partial or complete replacement of the oxygen atoms in the ring by substituents chosen from sulphur atoms and the groups >NH, >NR and >Si<R R R in which R is a C 1 -C 4 hydrocarbyl radical, and c) the carbon-containing macropolyrings chosen from polyoxadiazabicycloalkanes in which each ring contains 10 to 18 atoms and has at least two oxygen atoms in addition to the two nitrogen atoms.

Claim 7

The process according to claim 1, wherein the structuring agent ST results from the association of at least one compound MC with a costructurant CS consisting of at least one oxygen-containing acyclic compound chosen from the compounds of formula R.sub.1 --O--C.sub.m H.sub.2m-1 X--O).sub.8 R.sub.2 in which each of R 1 and R 2 , which are identical or different, denotes a hydrogen atom or a C 1 -C 4 alkyl radical, X denotes a hydrogen atom or an OH radical, m is equal to 2 or 3 and may be different from one repeat unit to another and g is a number ranging from 1 to 12.

Claim 8

The process according to claim 6, wherein the costructurant CS consists of at least one compound chosen from ethylene glycol methyl ether, ethylene glycol dimethyl ether, ethylene glycol, propylene glycol, polyethylene glycols of formula HO--CH 2 CH 2 CH 2 O) g .sbsb.1 H and their methyl ethers of formula CH 3 O--CH 2 CH 2 O) g .sbsb.1 H and polypropylene glycols of formula OH--CH 2 CH 2 CH 2 O) g .sbsb.1 H with g 1 denoting a number ranging from 2 to 9 in these formulae.

Claim 9

The process according to claim 6, wherein the quantity of structuring agent resulting from the association of at least one compound MC and of the costructurant CS, which is present in the reaction mixture intended to form the gel and the composition of said structuring agent are such as to make the molar ratio structuring agent: Al III range from 0.1 to 4 and so as to make the molar ratio MC:Al III equal to or higher than 0.05.

Claim 10

The process according to claim 8, wherein the quantity of structuring agent and its composition are such as to make the molar ratio structuring agent: Al III range from 0.2 and 2 and so as to make the molar ratio MC:Al III equal to or higher than 0.1.

Claim 11

The process according to claim 1, wherein the structuring agent consists of at least one compound MC 1 chosen from the compounds MC which are macrorings which have 10 to 17 atoms in the ring or macropolyrings which have 10 to 18 atoms in each ring, so as to obtain a zeolite which has the faujasite structure of cubic symmetry.

Claim 12

The process according to claim 6, wherein the structuring agent results from the association of a costructurant CS with at least one compound MC 1 chosen from the compounds MC which are macrorings which have 10 to 17 atoms in the ring or macropolyrings which have 10 to 18 atoms in each ring, so as to obtain a zeolite which has the faujasite structure of cubic symmetry.

Claim 13

The process according to claim 1, wherein the structuring agent consists of at least one compound MC 2 chosen from the compounds MC which are macrorings containing at least 18 atoms in the ring, so as to obtain a zeolite which has the hexagonal symmetry structure of the hexagonal polytypes of faujasite.

Claim 14

The process according to claim 1, wherein the source of tetravalent silicon is chosen from the group consisting of finely divided silicas in the form of hydrogels, aerogels or colloidal suspensions, water-soluble silicates such as alkali metal silicates like sodium silicate, and hydrolysable silicic esters such as tetraalkyl orthosilicates of formula Si(OR) 4 in which R denotes a C 1 -C 4 alkyl radical.

Claim 15

The process according to claim 1, wherein the source of trivalent aluminum is selected from the group consisting of aluminum salts, aluminum oxides and hydroxides and aluminates.

Claim 16

The process according to claim 1, wherein the source of hydroxide ions is selected from the group made up of hydroxides of the alkali metals of group IA of the Periodic Classification of the Elements, the hydroxides of the alkaline-earth metals Ca, Sr and Ba and quaternary ammonium hydroxides.

Claim 17

The process according to claim 1, wherein the reaction mixture contains cations M n+ of at least one metal M, of valency n, other than the metals whose hydroxides are strong bases, in an overall quantity such as to make the molar ratio M n+ :Al III in said mixture not exceed 0.4.

Claim 18

The process according to claims 1 to 16, wherein before proceeding to crystallize the gel, crystallization seeds are added to the reaction mixture intended to form said gel, in a quantity ranging from 0.1% to 10% by weight of said reaction mixture.

Claim 19

The process according to claim 1, wherein before proceeding to crystallize the gel, said gel is subjected to a maturing operation, in a closed vessel, at a temperature below the crystallization temperature for a period ranging from approximately 6 hours to approximately 6 days.

Claim 20

The process according to claim 1, wherein the crystallization of the alumino-silicate gel, with or without seed, is carried out by keeping the said gel at a temperature ranging from 90° C. to 120° C. for a period of between 2 hours and fifteen days.

Claim 21

The process according to claim 1, wherein the calcination of the zeolite precursor is carried out at a temperature above 300° C.

Claim 22

Precursors of zeolites of the faujasite structural class, consisting of aluminosilicates which have a Si:Al ratio higher than 1 and which, on the one hand, exhibit a structure of cubic symmetry comparable with that of faujasite or else a structure of hexagonal symmetry comparable with that of the hexagonal polytypes of faujasite or else comprise domains exhibiting a structure of cubic symmetry comparable to that of faujasite and domains exhibiting a structure of hexagonal symmetry comparable with that of the hexagonal polytypes of faujasite, and have cavities or channels trapping molecules of a structuring agent, ST, wherein the structuring agent ST consists of at least one compound MC, chosen from the group consisting of carbon-containing macrorings and macropolyrings which contain in the rings heteroatoms chosen from O, N, Si and S and which contain 10 to 24 atoms per ring, or results from the association of at least one compound MC with a costructurant CS consisting of at least one oxygen-containing acyclic compound chosen from the compounds of formula R 1 --O--C m H 2m-1 X--O] 8 R 2 , in which each of R 1 and R 2 , which are identical or different, denotes a hydrogen atom or a C 1 -C 4 alkyl radical, X denotes a hydrogen atom or an OH radical, m is equal to 2 or 3 and may be different from one repeat unit to the other and g is a number ranging from 1 to 12.

Claim 23

Precursors of zeolites of the faujasite structural class, consisting of aluminosilicates which have a Si:Al ratio higher than 1 and which, on the one hand, exhibit a structure of cubic symmetry comparable with that of faujasite or else a structure of hexagonal symmetry comparable with that of the hexagonal polytypes of faujasite or else comprise domains exhibiting a structure of cubic symmetry comparable to that of faujasite and domains exhibiting a structure of hexagonal symmetry comparable with that of the hexagonal polytypes of faujasite, and have cavities or channels trapping molecules of a structuring agent, ST, wherein the structuring agent ST consists of at least one compound MC, chosen from the group consisting of carbon-containing macrorings and macropolyrings which contain in the rings heteroatoms chosen from O, N, Si and S and which contain 10 to 24 atoms per ring, or results from the association of at least one compound MC with a costructurant CS consisting of at least one oxygen-containing acyclic compound chosen from the compounds of formula R 1 --O--C m H 2m-1 X--O] 8 R 2 , in which each of R 1 and R 2 , which are identical or different, denotes a hydrogen atom or a C 1 -C 4 alkyl radical, X denotes a hydrogen atom or an OH radical, m is equal to 2 or 3 and may be different from one repeat unit to the other and g is a number ranging from 1 to 12.

Claim 24

Precursors according to claim 21, wherein the compound(s) MC contained in the structuring agent ST are selected from the group consisting of a) crown ethers whose ring contains 10 to 24 atoms and comprises solely oxygen atoms as heteroatoms, at least 4 in number, b) the compounds derived from the crown ethers defined under a) by partial or complete replacement of the oxygen atoms of the ring by substituents chosen from sulphur atoms and the groups >NH, >NR and >Si<R R R , in which R is a C 1 -C 4 hydrocarbyl radical, and c) the carbon-containing macropolyrings chosen from polyoxadiazabicycloalkanes in which each ring contains 10 to 18 atoms and has at least two oxygen atoms in addition to the two nitrogen atoms.

Claim 25

Precursors according to claim 21, wherein in addition to the compound(s) MC, the structuring agent ST also contains a costructurant CS consisting of at least on compound chosen from ethylene glycol methyl ether, ethylene glycol dimethyl ether, ethylene glycol, propylene glycol, polyethylene glycols of formula HO--CH 2 CH 2 O) g .sbsb.1 H and their methyl ethers of formula CH 3 --O--CH 2 CH 2 O) g 1 H and propylene glycols of formula HO--CH 2 CH 2 CH 2 O) g .sbsb.1 H with g 1 denoting a number ranging from 2 to 9 in these formulae.

Claim 26

The process of claim 1 wherein the Si:Al ratio is greater than 3.

Claim 27

The process according to claim 14, wherein the source of trivalent aluminium is selected from the group consisting of alkali metal aluminates and aluminium trialkoxides of formula Al(OR) 3 in which R is C 1 -C 4 alkyl radical.

Claim 28

The process according to claim 16, wherein said cations M nt are selected from the group consisting of Co ++ , Cd ++ , Mg ++ and Ag + .

Claim 29

The process according to claim 17 wherein the recrystallization seeds are produced by grinding a zeolite of the same kind as the crystalline phase to be produced or by synthesis from a suitable nucleating solution.

Claim 30

Precursors according to claim 21 exhibiting a structure of cubic symmetry comparable with that of faujasite, wherein they exhibit an x-ray diffraction pattern comparable with that defined in Table III TABLE III ______________________________________ 2θ (°) d.sub.hkl (10.sup.-1 nM) (h k l) I/Io ______________________________________ 6.26 14.10 ± 0.2 (1 1 0) VS 10.23 8.65 (2 2 0) w 12.01 7.35 (3 1 1) mS 15.77 5.615 ± 0.05 (3 3 1) S 18.81 4.713 (5 1 1) m 20.49 4.331 (4 4 0) mS 22.93 3.875 (6 2 0) w 23.77 3.740 (5 3 3) mS 25.15 3.537 (4 4 4) vw 25.93 3.433 (5 5 1) vw 27.19 3.276 (6 4 2) mS 27.93 3.191 ± 0.008 (7 3 1) vw 29.81 2.994 (7 3 3) w ______________________________________ and are represented by a formula which, reduced to a unit cell of the cubic structure, is written (vM.sub.1.sup.qt) (wM.sup.nt) ((SiO.sub.2).sub.192-x (AlO.sub.2).sub.x).sup.x- (PST.sub.1) (zH.sub.2 O) and in which M1 qt denotes a q-valent cation of a metal selected from the group consisting of group IA of the Periodic Classification of the Elements (q=1), an alkaline-earth metal chosen from Ca, Sr and Ba (q=2), and a monovalent cation containing nitrogen (q=1) M n+ denotes a cation of a metal M of valency n other than a cation M1 qt , x, z, v and w are numbers such that 30≦x≦96, z≧0 and depending on the hydration state of the precursor, 0<v≦x/q and 0≦w≦x/n with qv+wn≧x, p is a number such that 4≦p≦10 and ST 1 denotes at least one compound MC 1 selected from the compounds MC consisting of macrorings containing from 10 to 17 atoms in the ring or macropolyrings containing 10 to 18 atoms in each ring or a mixture of at least one compound MC 1 and of the constructurant CS.

Claim 31

Precursors according to claim 21, exhibiting a structure of hexagonal symmetry comparable with that of the hexagonal polytypes of faujasite, wherein they exhibit an x-ray diffraction pattern comparable with that given in Table IV below: TABLE IV ______________________________________ 2θ (°) d.sub.hkl (10.sup.-1 nM) (h k l) I/Io ______________________________________ 5.88 15.02 ± 0.2 (1 0 0) VS 6.24 14.15 (0 0 2) S 6.65 13.28 (1 0 1) S 10.12 8.73 ± 0.08 (1 ) w 11.01 8.03 (1 0 3) mw 11.93 7.41 (1 1 2) mS 13.58 6.515 (2 0 2) vw 15.57 5.686 ± 0.05 (0 0 5) mS 15.86 5.580 (2 1 1) mw 16.70 5.305 (1 0 5) mw 17.15 5.165 (2 0 4) S 18.16 4.88 (2 1 3) mw 18.71 4.74 (1 1 5) mw 19.65 4.509 (1 0 6) mS 20.42 4.345 (2 2 0) S 22.14 4.011 (3 1 2) mS 22.71 3.912 (1 0 7) mw 23.32 3.811 (3 1 3) mw 23.60 3.766 (3 0 5) mw 24.68 3.604 (3 1 4) mw 25.81 3.449 (2 2 5) w 26.49 3.362 (2 1 5) w ______________________________________ and are represented by a formula which, reduced to a hexagonal unit cell of the crystalline structure, is written (u M1 qt ) (rM n+ ) (SiO.sub.2).sub.96-y (AlO.sub.2).sub.y).sub.y- (j ST.sub.2) (t H.sub.2 O) with, in this formula, M 1 qt denoting a q-valent cation of a metal selected from the group consisting of IA of the Periodic Classification of the Elements (q=1), an alkaline-earth metal chosen from Ca, Sr and Ba (q=2) and a monovalent cation containing nitrogen (q=1) M nt denoting a cation of a metal M of valency n other than a cation M 1 qt , y, u, r and t being numbers such that 15≦y≦48, t≧0 and depending on the hydration state of the precursor, 0<u≦y/q and 0≦r≦y/n with q u+n r≧y, j being a number such that 2≦j≦5 and ST 2 denoting at least one compound MC 2 chosen from the compounds MC which are macrorings containing at least 18 atoms in the ring.

Claim 32

A process for the preparation of zeolites which have the cubic symmetry structure of faujasite by calcination of the precursors of claim 38, the zeolites obtained having a cubic unit cell parameter value of between 2.4 and 2.5 nm, exhibiting an x-ray diffraction pattern comparable with that given in Table I below: TABLE 1 ______________________________________ 2θ (°) d.sub.hkl (10.sup.-1 nM) (hkl) I/Io ______________________________________ 6.245 14.14 ± 0.2 (1 1 1) VS 10.205 8.66 (2 2 0) S 11.965 7.39 (3 1 1) mS 15.735 5.627 ± 0.05 (3 3 1) S 18.775 4.721 (5 1 1) w 20.465 4.335 (4 4 0) mw 22.895 3.881 (6 2 0) w 23.755 3.727 (5 3 3) mS 25.105 3.544 (4 4 4) vw 25.965 3.428 (5 5 1) vw 27.175 3.279 (6 4 2) mS 27.885 3.196 ± 0.008 (7 3 1) vw 29.765 2.999 (7 3 3) w ______________________________________ and corresponding to the formula which, reduced to unit cell of the cubic structure, is written (v M.sub.1.sup.q+) (w M.sup.n+) ((SiO.sub.2).sub.192-x (AlO.sub.2).sub.x).sup.x- (z H.sub.2 O) and in which, M 1 qt , M nt , x,z,v and w have the meanings given in claim 37.

Claim 33

A process for the preparation of zeolites which have the hexagonal symmetry structure of the hexagonal polytypes of faujasite by calcination of the precursors of claim 29, the zeolites obtained having hexagonal unit cell parameters a,b,c, of the said structure such that 1.72 nm<a=b<1.77 nm and 2.80 nm<c<2.89 nm, exhibiting an x-ray diffraction pattern comparable with that given in Table II ______________________________________ 2θ (°) d.sub.hkl (10.sup.-1 nM) (h k l) I/Io ______________________________________ 5.88 15.03 ± 0.2 (1 0 0) VS 6.23 14.2 (0 0 2) VS 6.66 13.3 (1 0 1) S 8.40 10.52 (1 0 2) w 10.19 8.68 ± 0.08 (1 1 0) S 11.06 7.99 (1 0 3) mS 11.78 7.51 (2 0 0) mS 11.95 7.40 (1 1 2) mS 13.49 6.56 (2 0 2) vw 15.06 5.88 ± 0.05 (2 0 3) w 15.58 5.68 (0 0 5) S 15.89 5.57 (2 1 1) w 16.73 5.29 (1 0 5) w 17.18 5.16 (2 0 4) S 18.22 4.87 (2 1 3) w 18.79 4.72 (1 1 5) w 19.67 4.51 (1 0 6) w 20.45 4.34 (2 2 0) mS 22.22 4.00 (3 1 2) w 22.75 3.91 (1 0 7) w 23.30 3.82 (3 1 3) w 23.66 3.76 (3 0 5) S 24.75 3.59 (3 1 4) w 25.83 3.45 (2 2 5) w 26.52 3.36 (2 1 5) w 27.16 3.28 (4 1 0) w 28.77 3.103 ± 0.008 (3 2 4) w 30.38 2.942 (4 0 6) vw 30.89 2.894 (3 3 0) w 31.20 2.866 (5 0 3) w 31.56 2.834 (3 3 2) vw ______________________________________ and corresponding to a formula which, reduced to a unit cell of the hexagonal structure, is written (u M.sub.1.sup.q+) (r M.sup.n+) ((SiO.sub.2).sub.96-y (AlO.sub.2).sub.y).sup.y- (t H.sub.2 O) and in which the symbols M 1 qt , M nt , y,t,u and r have the meanings given in claim 38.

Claim 34

A process for the preparation of precursors of zeolites belonging to the faujasite structural class and exhibiting a Si:Al ratio higher than 1, said process comprising first forming a reaction mixture which has a small pH higher than 10 and contains water, a source of tetravalent silicon, a source of trivalent aluminum, a source of hydroxide ions in the form of a strong inorganic or organic base and a structuring agent ST so as to produce an alumino silicate gel having the composition to permit its crystallization into a compound of the faujasite structural class, and the gel obtained is then kept at a temperature not exceeding 150° C. and under a pressure at least equal to the autogenous pressure of said gel for a sufficient period to effect crystallization of the gel into a precursor of the zeolite consisting of the zeolite with the structuring agent ST trapped in its cavities and consisting of at least one compound MC selected from the group consisting of the carbon-containing macrorings and macropolyrings which contain in the rings heteroatoms selected from the group consisting of oxygen, nitrogen, silicon and sulfur, and which contain 10 to 24 atoms per ring.

Claim 35

A process for the preparation of precursors of zeolites belonging to the faujasite structural class and exhibiting a Si:Al ratio higher than 1, said process comprising first forming a reaction mixture which has a small pH higher than 10 and contains water, a source of tetravalent silicon, a source of trivalent aluminum, a source of hydroxide ions in the form of a strong inorganic or organic base and a structuring agent ST so as to produce an alumino silicate gel having the composition to permit its crystallization into a compound of the faujasite structural class, and the gel obtained is then kept at a temperature not exceeding 150° C. and under a pressure at least equal to the autogenous pressure of said gel for a sufficient period to effect crystallization of the gel into a precursor of the zeolite consisting of the zeolite with the structuring agent ST trapped in its cavities and consisting of at least one compound MC selected from the group consisting of the carbon-containing macrorings and macropolyrings which contain in the rings heteroatoms selected from the group consisting of oxygen, nitrogen, silicon and sulfur, and which contain 10 to 24 atoms per ring.

Claim 36

The process according to claim 32, wherein the quantity of structuring agent ST in the reaction mixture intended to form the gel is such as to make the molar ratio ST:Al III ranging from 0.1 to 4.

Claim 37

The process according to claim 32, wherein the ingredients making up the reaction mixture giving rise to the aluminosilicate gel are employed in such quantities as to give said gel, in terms of molar ratios, a composition such that SI IV :Al III III =2 to 20, OH - :Al III =0.5 to 8, ST:Al III -0.1 to 4 and H 2 O:Al III =40 to 200.

Claim 38

The process according to claim 32, wherein the structuring agent ST consists of at least one compound MC chosen from the group consisting of a) crown ethers whose ring contains 10 to 24 atoms and comprises solely oxygen atoms as heteroatoms, at least 4 in number, b) compounds derived from the crown ethers defined under 1) by partial or complete replacement of the oxygen atoms in the ring by substituents chosen from sulphur atoms and the groups >NH, >NK and SI< R R in which R is a C 1 -C 4 hydrocarbyl radical, and c) the carbon-containing macropolyrings chosen from polyoxadiazabicycloalkanes in which each ring contains 10 to 18 atoms and has at least two oxygen atoms in addition to the two nitrogen atoms.

Claim 39

The process according to claim 32, wherein the structuring agent ST results from the association of at least one compound MC with a costructurant CS consisting of at least one oxygen-containing acyclic compound chosen from the compound of the formula R.sub.1 --O--C.sub.m H.sub.2m-1 X--O).sub.g R.sub.2 in which each of R 1 and R 2 , which are identical or different, denotes a hydrogen atom or a C 1 -C 4 alkyl radical, X denotes a hydrogen atom or an OH radical, m is equal to 2 or 3 and may be different from one repeat unit to another and g is a number ranging from 1 to 12.

Claim 40

The process according to claim 36, wherein the quantity of structuring agent resulting from the association of at least one compound MC and of the costructurant CS, which is present in the reaction mixture intended to form the gel and the composition of the said structuring agent are such to make the molar ratio structuring agent:Al III range from 0.1 to 4 and so as to make the molar ratio MC:Al III equal to or higher than 0.05.

Claim 41

The process according to claim 32, wherein the structuring agent consists of at least one compound MC 1 chosen from the compounds MC which are macrorings which have 10 to 17 atoms in the ring or macropolyrings which have 10 to 18 atoms in each ring, so as to obtain a zeolite precursor which has the faujasite structure of cubic symmetry.

Claim 42

The process according to claim 36, wherein the structuring agent results from the association of a costructurant CS with at least one compound MC 1 chosen from the compounds MC which are macropolyrings which have 10 to 17 atoms in the ring or macropolyrings which have 10 to 18 atoms in each ring, so as to obtain a zeolite precursor which has the faujasite structure of cubic symmetry.

Claim 43

The process according to claim 32, wherein the structuring agent consists of at least one compound MC 2 chosen from the compound MC which are macrorings containing at least 18 atoms in the ring, so as to obtain a zeolite precursor which has the hexagonal symmetry structure of the hexagonal polytypes of faujasite.

Claim 44

The process according to claim 32, wherein the source of tetravalent silicon is chosen from the group consisting of finely divided silicas in the form of hydrogels, aerogels or colloidal suspensions, water-soluble silicates such as alkali metal silicates and hydrolysable silicic esters such as tetraalkyl orthosilicates of formula Si(OR) 4 in which R denotes a C 1 -C 4 alkyl radical.

Claim 45

The process according to claim 41, wherein the source of trivalent aluminum is chosen from the group consisting of aluminium salts, aluminium oxides and hydroxides, aluminates and aluminium esters.

Claim 46

The process according to claim 32, wherein the source of hydroxide ions is chosen from the group consisting of hydroxides of the alkali metals of group IA of the Periodic Classification of the Elements, the hydroxides of the alkaline-earth metals Ca,Sr and Ba and quaternary ammonium hydroxides.

Claim 47

The process according to claim 32, wherein the reaction mixture contains cations M n+ of at least one metal M, of valency n, other than the metals whose hydroxides are strong bases, in an overall quantity such as to make the molar ratio M n+ :Al III in said mixture not exceed 0.4.

Claim 48

The process according to claim 32, wherein before proceeding to crystallize the gel, crystallization seeds are added to the reaction mixture intended to form said gel, in a quantity ranging from 0.1% to 10% by weight of said reaction mixture.

Claim 49

The process according to claim 32, wherein before proceeding to crystallize the gel, said gel is subjected to a maturing operation, in a closed vessel, at a temperature below the crystallization temperature for a period ranging from approximately 6 hours to approximately 6 days.

Claim 50

The process according to claim 32, wherein the crystallization of the aluminosilicate gel, with or without seed, is carried out by keeping said gel at a temperature ranging from 90° C. to 120° C. for a period of between 2 hours and fifteen days.