GB2125390A

GB2125390A - Preparation of zeolites

Info

Publication number: GB2125390A
Application number: GB08321325A
Authority: GB
Inventors: Philip John Hogan
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1982-08-16
Filing date: 1983-08-08
Publication date: 1984-03-07
Also published as: GB8321325D0; GB2125390B

Abstract

A method of preparation of aluminosilicate zeolites is described in which the source of silicon in the reaction is, at least in part, a layer silicate especially magadiite or kenyaite.

Description

SPECIFICATION Preparation of zeolites The present invention relates to a method for the preparation of zeolites.

Zeolites have been known for very many years but interest in their use as molecular sieves and as catalysts has increased very considerably over the last 30 years. Many zeolites occur in nature and in recent years many synthetic zeolites have also been prepared. The technical literature of the last 25 years or so is replete with descriptions of new zeolites and of their preparation and with proposals for the use of zeolites, both old and new, as catalysts in a wide variety of chemical processes. Many of these proposals relate to the use of zeolites in processes used in the oil and petrochemical industry such as aromatisation, hydrocarbon cracking, isomerisation processes and the like.

Zeolites, both natural and synthetic, include a considerable number of cation-containing crystalline aluminosilicates which can be characterised as rigid three-dimensional frameworks of SiO4 and AlO4 in which the tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total aluminium and silicon atoms to oxygen is 1:2. The electrovalence of the tetrahedra containing aluminium is balanced by the inclusion in the crystal of a suitable cation. The properties of a given cation-containing aluminosilicate zeolite can be varied by suitable selection of a cation and it is now common practice to ion-exchange one cation for another, either partially or completely, so as to obtain a zeolite most suited for the particular purpose in mind.

Natural zeolites have generally been given generic names, for example faujasite, mordenite, while synthetic zeolites are usually designated by letters or other convenient symbols, for example zeolites A, X, Y, FU-1, NU-1, ZSM-5 etc.

A considerable amount of attention has been paid to the preparation of synthetic zeolites with such objects in view as cheaper routes to zeolites and the preparation of purer forms of the zeolites.

Since zeolites are aluminosilicates, starting materials for their preparation must include at least sources of aluminium and of silicon. Many such sources have been proposed from among the many compounds of these elements including for example various metal silicates, metal aluminates, silica, aluminium hydroxide and also compounds which can serve as sources of both silicon and aluminium.

According to the present invention a method for preparing a crystalline aluminosilicate zeolite comprises forming a reaction mixture comprising at least one source of aluminium and at least one source of silicon and crystallising the zeolite from the reaction mixture characterised in that the source of silicon comprises, at least in part, a layer silicate. Layer silicates have been extensively described in the technical literature. For example, Eugster in Science 157 (1967) P. 1177 describes some layered sodium silicates. Silicate sheet structures are discussed by Breck in his book "Zeolite Molecular Sieves" (Wiley-lnterscience 1974) at page 35, examples of such sheet structures being kaolinate, montmorillonite clays, micas and some zeolites, for example heulandite.Further descriptions of layer silicates appear in "Crystal Structures of Clay Minerals and their X-ray Identification", Monograph No.

5 of the Mineralogical Society Ed. G. W. Brindley and G. Brown (1980) pages 2 and 380.

Preferably, the layer silicate comprises magadiite or kenyaite in either natural or synthetic form.

The Applicants have found that magadiite is a particularly attractive source of silicon as it enables useful zeolites to be prepared both cheaply and easily. A further advantage of the use of magadiite and kenyaite is their low content of aluminium. A prime source of natural magadiite is the area in East Africa around Lake Magadi. The exact structure of magadiite is not known but synthetic magadiite is known to have the molecular formula Na2Si14O29. 1 2H2O. Natural magadiite is known to contain small amounts of potassium, calcium and iron and X-ray diffraction also shows the presence of an anorthoclase type material (Ca, K, Na)AlSi3O8.

In preferred embodiments of the present invention the reaction mixture comprises at least one source of aluminium, magadiite as the source, at least in part, of silicon, and an organic material.

Preferably the organic material is a quaternary ammonium cation, more preferably a quaternary alkylammonium cation, for example tetrapropyl ammonium.

Examples The syntheses hereinafter described were carried out in 1000 or 300 cm3 stainless steel autoclaves equipped with "Magnadrive" turbine stirrers. The autoclaves were cleaned prior to each synthesis by heating 1 M sodium hydroxide solution in them for 16 hours at 1 600 C.

Synthetic magadiite was made by a modification of a route described by Lagaly et al in Z.

Naturforsch (1973), 286, 234. Two separate syntheses, A and B, were carried out from different sources of silicon. In each synthesis, however, the molar composition of the reaction mixture was NaOH, 3.51 SiO2, 37.5 H2O.

Synthesis A A solution of sodium hydroxide (24g) in deionised water (405g) was added to silica gel ( 1 62g, analysed as 2.3 Na2O,AI2O3,2321 SiO2, 2163 H20) and the mixture reacted under autogeneous pressure in a 1 litre autoclave at 1 200C for 137 hours with stirring at 600 rpm. After cooling to room temperature, the product was filtered, washed with deionised water until neutral and then dried at 1 000C for 1 6 hours. The yield of sodium magadiite was 1249. The powder X-ray diffraction data are recorded in Table 1 and were assigned as sodium magadiite. Elemental analysis of the product gave 4.8 wt% Na,38.1 wt% Si and 10.1 wt% H2O.

Table 1 Relative d(A) intensity I/Io d(A) I/lo 15.56 100 3.31 58 7.76 12 3.15 61 7.26 3 2.82 5 5.18 18 2.63 3 3.87 2 2.42 2 3.55 29 2.35 5 3.45 94 2.22 3 2.06 2 Synthesis B A solution of sodium hydroxide (24g) in deionised water (96g) was added with stirring to "Syton" X 30 colloidal silica (438.89, analysis 27 Na2O, Al203, 2400 SiO2, 19,550 H20) in a 1 litre autoclave.

The mixture was reacted under autogeneous pressure at 1 200C for 120 hours with stirring at 500 r.p.m. After cooling to room temperature, the product was filtered, washed with deionised water until neutral and then dried at 1 000C for 16 hours. The yield of sodium magadiite was 110g. The X-ray diffraction data were assigned as those of sodium magadiite and are shown in Table 2. Elemental analysis of the product gave: 5.2 wt% Na, 35.5 wt% Si and 9.0 wt% H20 Table 2 d(A) I/Io d(A) I/IO 15.45 90 3.45 100 11.11 2 3.31 64 7.76 9 3.15 66 7.26 3 2.83 5 5.18 19 2.63 3 4.44 0 2.59 7 3.89 0 2.35 3 3.64 22 2.30 3 3.56 31 2.06 2 Natural magadiite Natural magadiite was obtained from the Magadi Soda Company, Kenya. The as-supplied material was ground, washed with denionised water and dried at 100 C for 16 hours. The X-ray powder diffraction pattern was assigned as sodium magadiite with some anorthoclase and calcite impurities and is shown in Table 3. The analysis of the material was (in terms of mole ratios): 0.4 K20: 0.5 CaO: 0.4 Fe203: 2.8 Na20: Al2O3: 33.6 SiO2: 1 2H20.

Elemental analysis gave (all percentages in wt%). 1.0% K,4.3% A, 0.7% Ca, 1.5% Fe, 1.8% Al, 31.4% Si and 7.3% HzO.

Table 3 d(A) 1/I0 d(A) I/lo 15.51 100 3.30 43 10.51 0 3.24 26(A) 8.48 1 3.21 30(A) 7.77 11 3.14 45 7.25 2 3.03 11 6.86 2 3.00 10 6.48 2(A) 2.87 10 5.63 4 2.82 7 5.18 19 2.74 5 5.02 14 2.64 4 4.69 5 2.59 8 4.47 21 2.54 6(C)(A) 4.10 7(A) 2.41 2 4.02 12 2.35 6 3.90 10(C) 2.28 4(C) 3.75 8(A) 2.16 1(A) 3.62 15 2.09 1(C) 3.55 20 2.07 1 3.44 63 2.01 1 Key: (A) Analcime (C) Calcite Example 1 Preparation of zeolite ZSM-5 A solution of sodium aluminate (1.36g, analysis 1.22 Na2O, Al2O3,1.02 H2O) and sodium hydroxide (4.689) in deionised water (609) was added with stirring to a suspension of sodium magadiite (29.2g-prepared as in Synthesis A) in a 1 litre stainless steel autoclave.The mixture was reacted at 1 500C under autogeneous pressure for 11 7 hours. The mixture was then cooled to room temperature, tetrapropylbromide added (13.729), and the mixture again reacted under autogeneous pressure at 1 500C for a further 89 hours with stirring at 500 r.p.m. After cooling to room temperature, the product was filtered, washed with deionised water and dried at 1 000C for 3 hours. The yield was 20g.

The powder X-ray diffraction pattern was consistent with a mixture of ZSM-5 type zeolite (with a pronounced orientation effect in the intensity of the peak at a d-spacing of 1 0A) with ct-quartz and some mordenite. Normal intensities were observed after wet grinding. The X-ray diffraction pattern is shown in Table 4. The ZSM-5 type zeolite had a silica/alumina mole ratio of 40. Elemental analysis gave (all percentages in wt%): 4.99% C,1.41 H, 0.47% N, 1.76% Na,39.6% Si,1.9% Al.

Table 4 d(AJ l/lo d(A) 1/lO d(A) I/lo 13.81 3(M) 5.02 26* 3.00 7 11.32 8 4.64 4 2.96 5 10.10 93* 4.55 6(M) 2.90 5 9.85 4 4.49 3 2.80 1 9.16 9(M) 4.39 3 2.74 3 7.52 5 4.29 15(Q) 2.70 1 7.15 4 4.02 13 2.62 4 6.77 3 3.85 100 2.57 2 6.64 5 3.78 37 2.52 5 6.43 6(M) 3.74 20 2.50 8 6.11 4 3.67 16 2.47 5 6.04 5(M) 3.49 19(M) 2.41 2 5.77 7 3.36 79(Q) 2.34 1 5.61 5 3.22 9(M) 2.29 5 5.42 1 3.16 2 2.25 2 5.17 2 3.07 8 2.21 1 Key: (Q) a -quartz (M) mordenite-type catalyst * pronounced orientation effect Example 2 Example 1 was repeated except that in the initial reaction mixture the amounts of reactants were sodium aluminate (1.36g), sodium hydroxide (2.2g) in deionised water (609) and added to sodium magadiite (29.2g from Synthesis A) in deionised water (297g). The reaction mixture was cooled to room temperature after 114 hours and tetrapropylammonium bromide (13729) added. Thereafter the mixture wa. reacted under autogeneous pressure at 1 500C for 89 hours with stirring at 500 r.p.m.

After cooling 3 to room temperature, the product was filtered, washed with deionised water until neutral and dried at 1 000C for 3 hours. The yield of product was 1 7g. The powder X-ray diffraction pattern was consis nt with a ZSM-5 type zeolite and is recorded in Table 5. The ZSM-5 type zeolite had a silica/alumina ratio of 45. Elemental analysis of the product showed (all percentages by weight): 6.58% C, 1.78% H, 0.62% N,1.68% Na, 39.5% Si, 1.7% Al.

Table 5 d(A) 1/Io d(A) I/lo d(A) I/lo 13.62 2(M) 5.57 4 3.76 36 11.17 9 5.38 1 3.72 18 10.00 30 5.14 2 3.65 14 9.06 7(M) 5.00 8 3.47 14(M) 7.45 4 4.87 0 3.44 9 7.09 3 4.61 4 3.39 10(M) 6.71 3 4.52 5(M) 3.34 8 6.58 4 4.45 2 3.24 7 6.38 5(M) 4.37 3 3.20 8(M) 6.07 4 4.27 6 3.14 2 6.00 5(M) 4.00 13 5.73 6 3.83 100 ty: (M)-mordenite-type zeolite Example 3 Exams e 1 was repeated except that: (a) the tetrapropylammonium bromide was added at the start of the synthesis (b) thee was therefore no intermediate cooling (c) thc otal reaction time was 72 hours.

The yilid of product was 1 89 and its X-ray diffraction pattern was consistent with sodium tetra propylammcnium ZSM-5 type zeolite. The X-ray pattern is recorded in Table 6. The ZSM-5 type zeolite had a silica/ lumina mole ratio of 45 and the elemental analysis was (all percentages by weight): 7.27% C. 1.82% H, 0.68% N,1.38% Na, 39.7% Si, 1.7% Al.

Table 6 d(A) 1/i0 d(A) 1/l0 d(A) 1/l0 13.60 1(M) 5.57 5 3.84 100 11.17 11 5.38 1 3.76 36 10.00 25 5.14 2 3.72 22 9.05 4(M) 5.00 7 3.65 17 7.45 5 4.61 4 3.47 11(M) 7.09 3 4.52 3(M) 3.44 9 6.69 2 4.47 3 3.39 7(M) 6.58. 3 4.37 4 3.33 8 6.38 4(M) 4.27 6 3.24 5 6.00 5(M) 4.09 1 3.20 6(M) 5.72 6 4.00 10 3.42 2 Key: (M)-mordenite-type zeolite Example 4 A solution of sodium aluminate (0.3229), sodium hydroxide (1.169) and tetrapropylammonium bromide (3.27g) in deionized water (779) was added to synthetic sodium magadiite (6.0g from Synthesis B) in a 300 cm3 stainless steel autoclave. The mixture was reacted under autogeneous pressure at 1 500C for 94 hours with stirring at 500 r.p.m.After cooling to room temperature the product was filtered, washed with deionized water until neutral and dried at 1 000C for 16 hours. The yield of product was 2.7g. Its X-ray diffraction pattern, which is recorded in Table 7, was consistent with sodium tetrapropylammonium ZSM-5 type zeolite. The zeolite had a silica/alumina mole ratio of 39 and its elemental analysis (all percentages by weight) was: 7.34% C, 1.73% H,0.65% N, 38.6% Si, 1.9% Al.

Table 7 d(A) 1/Io d(A) 1/Io d(A) I/lo 13.62 1(M) 5.58 7 3.84 100 11.18 12 5.38 1 3.76 36 10.02 26 5.14 2 3.72 22 9.06 5(M) 5.00 7 3.66 18 8.06 0 4.85 1 3.47 11(M) 7.46 5 4.61 4 3.44 10 7.10 3 4.52 3(M) 3.39 8(M) 6.70 2 4.47 3 3.33 8 6.52 3 4.37 4 3.24 5 6.38 5(M) 4.27 7 3.20 6(M) 6.01 5(M) 4.09 2 3.15 2 5.73 6 4.01 10 Key: (M)-mordenite-type zeolite Example 5 A solution of sodium aluminate (0.4g), sodium hydroxide (1.58g) and tetrapropylammonium bromide (4.19) in deionised water (108g) was added to synthetic sodium magadiite (6.0g from Synthesis B) in a 300 cm3 stainless steel autoclave. The mixture was reacted under autogeneous pressure at 1 500C for 114 hours with stirring at 500 r.p.m.After cooling to room temperature, the product was filtered, washed with deionised water until neutral and dried at 1 000C for 3 hours. The yield of product was 1 .9g and the product powder X-ray diffraction pattern was consistent with a mixture of ZSM-5 type zeolite and an analcime (P-C type) zeolite. The diffraction pattern is recorded in Table 8. The ZSM-5 type zeolite had a silica/alumina mole ratio of 23:1. Elemental analysis of the product (all percentages by weight) gave: 5.46% C, 1.48% H, 0.46% N, 3.6% Na, 37.6% Si and 3.1% Al.

Table 8 d(A) Mlo d(A) Ulo d(A) 1/10 11.23 9 4.62 3 3.19 3 10.04 27 4.47 3 3.14 1 9.04 2 4.38 3 3.06 10 7.48 5 4.28 7 2.99 8 7.11 3 4.09 1 2.95 6 6.73 1 4.02 6 2.92 25(A) 6.39 3 3.84 100 2.79 3(A) 6.01 5 3.77 39 2.74 2 5.72 9. 3.73 20 2.68 8(A) 5.59 41 (A) 3.66 17 2.62 4 5.40 1 3.60 2 2.58 2 5.15 2 3.42 59(A) 2.52 3 5.01 9 3.34 8 4.84 6(A) 3.26 3 Key: (A)-analcime (P-C type) zeolite Example 6 A solution of sodium aluminate (0.789) sodium hydroxide (2.719) and tetrapropylammonium bromide (8.069) in deionised water (1009) was added to natural magadiite (209) in deionised water (11 2g) in a 1 litre stainless steel autoclave.The mixture was reacted under autogeneous pressure for 65 hours at 1 500C with stirring at 500 r.p.m. After cooling to room temperature, the product was filtered, washed with deionised water until neutral and dried at 1 000C for 16 hours. The yield of product was 14.79. The powder X-ray diffraction pattern of the product is recorded in Table 9 and is consistent with a mixture of ZSM-5 type zeolite and anorthoclase. The ZSM-5 type zeolite had a silica/alumina molar ratio of 28:1. A trace of mordenite was also present in the product. The elemental analysis of the product (all percentages by weight) was: 5.17% C,1.47% H,0.47% N, 2.2% A, 0.8% K, 0.5% Ca,35.3% Si, 2.4% Al, 1.3% Fe.

Table 9 d(A) 1/lo d(A) I/lo d(A) 1/lo 13.62 2(M) 5.38 1 3.47 17(M) 11.19 14 5.14 2 3.44 14 10.03 23 5.00 5 3.39 11(M) 9.73 5 4.61 5 3.34 11 9.07 7(M) 4.52 6(M) 3.24 16(A) 8.52 1 4.46 4 3.21 16(A)(M) 7.46 5 4.37 5 3.14 1 7.10 3 4.27 8 3.06 10 6.70 3 4.10 3(A) 2.99 11 6.56 5 4.00 13(M) 2.95 7 6.39 7(M) 3.84 100 2.90 5 6.03 6(M) 3.76 38(A) 2.79 1 5.73 7 3.73 28(A) 2.74 3 5.58 7 3.65 20 2.69 1 Key: (A)-anorthoclase (M)-mordenite-type zeolite Example 7 Example 6 was repeated except that: (a) no sodium aluminate was used, and (b) total reaction time was 94 hours.

The yield of product was 139 and its powder X-ray diffraction pattern, which is recorded in Table 10, is consistent with a ZSM-5 type zeolite. The silica/alumina mole ratio of the product was 58 and its elemental analysis (all percentages by weight) was: 7.52% C,1.85% H,0.73% N, 0.6% Na,0.2% K, 0.5% Ca,38.9% Si, 1.3% Al, 1.3% Fe.

Table 10 d(A) Ulo d(A) 1/lo d(A) Iflo 11.19 16 5.38 1 3.72 31 10.03 20 5.14 2 3.65 23 9.73 6 5.00 5 3.59 2 9.00 2 4.61 5 3.49 4 7.46 6 4.46 3 3.44 10 7.09 3 4.37 6 3.39 4 6.72 2 4.27 9 3.34 9 6.38 5 4.09 2 3.31 8 6.00 7 4.01 7 3.25 7 5.72. 6 3.84 100 3.21 5 5.57 6 3.76 34 3.14 2 The Exe naples demonstrate the magadiite, in both natural and synthetic forms, is a suitable source of silica : in the synthesis of ZSM-5 type zeolites. As it is also cheap and readily available magadiite is ry attractive for zeolite synthesis.

Claims

1. A method of preparing a crystalline aluminosilicate zeolite comprising forming a reaction mixture com rising at least one source of aluminium and at least one source of silicon and crystallising the zeolite from the reaction mixture characterised in that the source of silicon comprises, at least in part, a layer silicate.

2. A method as claimed in claim 1 wherein the layer silicate comprises either magadiite or kenyaite in either natural or synthetic form.

3. A method as claimed in claim 1 or 2 in which the reaction mixture comprises at least one source of aluminium, magadiite as the source, at least in part, of silicon and an organic material.

4. A method as claimed in claim 3 in which the organic material is a quaternary ammonium cation.

5. A method as claimed in claim 3 or 4 in which the organic material is a quaternary alkylammonium cation.

6. A method as claimed in any one of claims 3 to 5 in which the organic material is a tetrapropylammonium cation.

7. A method of preparing a crystalline aluminosilicate zeolite substantially as hereinbefore described with reference to any one of examples 1 to 7.