GB2193490A - Metallosilicate Sigma-2 - Google Patents

Abstract

A crystalline metallosilicate, designated Sigma-2, which is non-zeolitic, having a distinctive X-ray diffraction pattern and which is prepared from reaction mixtures containing amines, preferably adamantanamine, as the organic component and has the formula:- 0.1-1.5 M2O: Y2O3: at least 20 X O2: 0-4000 H2O M is a monovalent inorganic cation or 1 DIVIDED n of a cation of valency n; X is silicon and/or germanium; Y is one or more of aluminium, iron, chromium, titanium vanadium, zirconium, molybdenum, arsenic, antimony, manganese, gallium and/or boron.

Description

SPECIFICATION Metallosilicates The present invention relates to a novel crystalline metallosilicate, hereinafter designated Sigma2, to methods for its preparation and to its use.

The occurrence in nature of crystalline metallosilicates, for example aluminosilicates, has been known for a very long time and in more recent times many new metallosilicates have been prepared synthetically. Particular interest has been shown in the zeolitic crystalline aluminosilicates and similar metallosilicates because of their sorption and catalytic properties. Over the last 25 years many so-calied "high-silica" zeolitic crystalline aluminosilicates have been prepared.

Some interest has also been shown in the non-zeolitic crystalline metallosilicates even though they appear to be of more limited use and applicability than true zeolites.

According to the present invention a crystalline metallosilicate material, Sigma-2, has a composition (in terms of mole ratios of oxides) expressed by the formula 0.1 to 1.5 R2O : Y2O3 : at least 20 XO2 : 0 to 4000H2O wherein R is a monovalent cation or 1/n of a cation of valence n, Xis silicon and/or germanium, Y is one or more of aluminium, iron, chromium, vanadium, molybdenum, arsenic, antimony, manganese, gallium and/or boron and H2O is water of hydration additional to water notionally present when M is H, and having an X-ray diffraction pattern substantially as set out in Table 1.

The X-ray diffraction data were obtained with a Philips APD 1700 automated X-ray diffraction system using Cu Ka radiation from a long fine focus X-ray tube operating at 40 kV and 50 mA.

(The radiation was monochromatised by a curved graphite crystal adjacent to the detector). An automatic, theta-compensating divergence slit was used with a 0.1 mm receiving slit and data collected between 1" and 60 2-theta with a step-scan size of 0.02 degrees 2-theta. Intensities were measured as peak heights above background from a packed powder bed of specimen.

Table 1 Typical X-Ray Diffraction for Metallosilicate Sigma-2

I d(A) Intensity I 9.75 + 0.20 w - vs 8.56 + 0.18 w - Tn 7.61 + 0.15 w I 6.65 + 0.14 w 4.54 + 0.10 vs 4.48 + 0.09 vs 4.39 + 0.09 Tn 4.28 + 0.09 , w 4.24 + 0.09 w 3.81 + 0.08 w I 3.39 + 0.07 Tn 3.33 + 0.07 Tn 3.29 + 0.06 Tn 3.05 + 0.05 w I 2.99 + 0.05 w 2.76 + 0.04 w 2.62 + 0.04 w 2.50 + 0.04 w vs = 60 to 100% s = 40 to 60% m = 20 to 40% w = 0 to 20% Within the above definition, particular mention may be made of materials having a molar composition expressed by the formula: 0.1 to 1.5 R2O : Y2O3 : at least 20 X02 : 0 to 200 H2O The X02/Y203 mole ratio in Sigma-2 is typically in the range 30:1 to 5000:1.

This definition includes both freshly prepared Sigma-2 ("freshly prepared" means the product of synthesis and washing, with optional drying, as hereinafter described) and forms of it resulting from dehydration and/or calcination. In freshly prepared Sigma-2, M may include an alkali metal, especially sodium, potassium, rubidium and/or caesium, and ammonium and hydrogen may also be present. Sigma-2 is usually prepared from reaction mixtures comprising nitrogencontaining organic cations or bases as hereinafter described and such cations or bases may also be present in the freshly prepared product. These nitrogen containing cations or bases are hereinafter referred to as Q.

Freshly prepared Sigma-2 may also contain nitrogen-containing compounds well in excess of the 1.5 moles (per mole of Y2O3) set out in the aforesaid definition of the composition of Sigma2, typically in the range 0.1 to 120 mole per mole of Y2O3. Most, if not all, of the nitrogen containing base will be physically trapped within the crystal lattice and should be removed by thermal treatment and/or oxidative degradation. This physically trapped basic material does not constitute part of the composition for the purposes of definition.Thus Sigma-2 as made typically has the following molar composition: 0.1 to 1.5 M20 : 0.1 to 120 Q: Y2O3 40 to 5000 X02 : 0 to 2000 H20 wherein M is an alkali metal and/or ammonium and can include hydrogen.

The present invention also comprises a method for the preparation of metallosilicate Sigma-2 which comprises reacting an aqueous mixture containing sources of at least one oxide XO2, optionally at least one oxide Y2O3, at least one oxide L2O and a source of a nitrogen-containing organic cation or base comprising an amine or quaternary ammonium compound or a derivative thereof or a precursor thereof where L is an alkali metal or ammonium.

Preferably the reaction mixture has a composition in terms of mole ratios of oxides of: X0JY203 25:1 to 5000:1, more preferably 40:1 to 2000:1, most preferably 70:1 to 2000:1.

LOH/XO2 10-8:1 to 1.0:1, more preferably 10-6:1 to 0.25:1, most preferably 10-4:1 to 0.15:1.

H2O/XO2 10:1 to 200:1, more preferably 15:1 to 80:1, most preferably 20:1 to 60:1.

Q/X 2 0.005:1 to 4:1, more preferably 0.01:1 to 1.0:1, most preferably 0.05:1 to 0.5:1 NZ/XO2 0 to 4.0:1, more preferably 0 to 1.0:1, most preferably 0 to 0.6:1.

X, Y, Q and L are as hereinbefore defined, and N is an alkali metal or ammonium ion which may be the same as L or a mixture of L and another alkali metal or ammonium ion necessary to balance the anion Z which comprises a strong acid radical added as a salt of N or present as the result of an acid form of Q being used, for example an amine hydrochloride, in which case Z represents the chloride ion. Other examples of Z may include bromide, iodide, sulphate and possibly mixtures of strong acid radicals.

NZ addition, while not essential, may accelerate crystallization of Sigma-2 from the reaction mixture and may also affect the size of crystals obtained.

Preferably Q is an amine, more preferably a cyclic amine, most preferably an adamantanamine, for example 1-adamantanamine.

The preferred alkali metal(s) is/are sodium and/or potassium and N is preferably the same as L. In their experiments so far the Applicants have found that if L is sodium then it is preferable to use a reaction mixture having an SiO2/Al2O3 mole ratio of greater than 75:1. When lower ratios than this are used, the synthesis of alumino-silicate Sigma-2 appears to be favoured by the use of higher reaction temperatures, for example greater than 180 to 1 900C. At such low SiO2/AI2O3 mole ratios the formation of Sigma-2 is also favoured by a stirring regime which is not very vigorous and which, if used in zeolite synthesis, might be regarded as inefficient and/or inadequate.At these low SiO2/Al203 mole ratios normally vigorous and efficient mixing tends to favour the formation of zeolite Sigma-1 (described in our co-pending United Kingdom Patent Application No 8618774) rather than Sigma-2.

The Applicants have also found that, using reaction mixtures having the same or similar SiO2/AI203 mole ratios, it is rather easier to prepare pure Sigma-2 when L is potassium rather than sodium.

The preferred oxide XO2 is silica (SiO2) and the preferred oxide Y203 is alumina (AN203).

The silica source can be any of those commonly considered for use in synthesising zeolites, for example powdered solid silica, silicic acid, colloidal silica or dissolved silica. Among the powdered silicas usable are precipitated silicas, especially those made by precipitation from an alkali metal silicate solution, such as the type known as "KS 300" made by AKZO, and similar products, aerosil silicas, fumed silicas such as those sold under the name "CAB-O-SIL" and silica gels suitably in grades for use in reinforcing pigments for rubber or silicone rubber.

Colloidal silicas of various particle sizes may be used, for example 10 to 15 or 40 to 50 microns, as sold under the registered Trade Marks "LUDOX", "NALFLOC", "NALCOAG" and "SYTON". The usable dissolved silicas include commercially available waterglass silicates containing 0.5 to 6.0, especially 2.0 to 4.0 mols of SiO2 per mol of alkali metal oxide, "active" alkali metal silicates as defined in UK Patent 1,193,254, and silicates made by dissolving silica in an alkali metal hydroxide or quaternary ammonium hydroxide or a mixture thereof.

The optional alumina source is most conveniently sodium aluminate, but can be aluminium, an aluminium salt, for example the chloride, nitrate or sulphate, an aluminium alkoxide or alumina itself, which should preferably be in a hydrated or hydratable form such as colioidal alumina, pseudoboehmite, boehmite, gamma alumina or the alpha or beta trihydrate.

At the end of the reaction, the solid phase is collected on a filter and washed and is then ready for further steps such as drying, dehydration and calcination. The Applicant's experience so far suggests that Sigma-2 is not apparently amenable to conventional methods of ion exchange once the organic content of the synthesised product has been reduced to a low level, for example by calcination.

The metallosilicate Sigma-2 finds use as a catalyst, for example in hydrocarbon conversion reactions, and as a sorbent. It is believed that it will also act as an encapsulating means for compounds, elements or ions by adsorption, chemisorption or ion-exchange, in particular of gases such as poisonous residues, isotopes, radioactive waste and other gases.

The metallosilicate of this invention and its preparation are further described and illustrated int the following examples.

Example 1 This example illustrates the synthesis of sodium adamantanamine Sigma-2, using 1-adamanta- namine (AN).

The synthesis mixture had the following molar composition ratios: 3Na2O : 20AN : 0.6AN203: 60Si02 : 2400H2O 2.52 g AN was dispersed in 101.5 g colloidal silica (Syton X30) and then 200 g water was added to give Mixture A. 0.943 g NaOH was added to 1.404 g sodium aluminate ("Technical" grade, British Drug Houses, of molar composition 1.229 Na20: Al2O3: 5.7 H20) and then 89.0 g water was added to give Mixture B. Mixture B was added to Mixture A with stirring at room temperature and the resulting mixture was stirred for 30 minutes before charging to a 1 litre capacity stainless steel autoclave. After sealing the autoclave, the reaction mixture was heated to 1 800C and maintained at that temperature under autogenous pressure for 120 hours with stirring at approximately 500 rpm.At the end of this time, the reactor and its contents were cooled to room temperature and discharged. The product was filtered and washed thoroughly with deionised water (about 2 litres) and the resulting solid was dried in an oven at 110 C ovenight. The yield was about 30 g.

The X-ray diffraction pattern of this solid is shown in Table 2 and Fig. 1. Chemical analysis of the product showed it to contain the following elements at the levels given: Carbon 10.1 wt %, Nitrogen 1.1 wt %, Silicon 33.2 wt %, Aluminium 0.69 wt % and Sodium 0.22 wt %. Calculation shows the product to have a Si02/AI203 molar ratio of about 92:1.

An attempt to prepare the hydrogen form of Sigma-2 was made by calcining 10 g of the dried solid from above in air in a muffle furnace at 700"C for 24 hours, and then attempting to exchange twice at ambient temperature with 1 M hydrochloric acid solution (about 100 cm3) for 2 hours, filtering and washing thoroughly with deionised water before finally drying at 110 C for 16 hours.

The X-ray diffraction pattern for this form is shown in Table 3 and Fig. 2. Chemical analysis of this material (which was white and crystalline) showed that the carbon and nitrogen levels had been very substantially reduced but that the sodium contained in the product of synthesis could not be removed by conventional calcination and ion-exchange procedures. This suggests that the crystalline aluminosilicate has very small windows in its pore system which, although allowing the products of combustion to escape at high temperatures, do not permit ion exchange at ambient temperature. Calculation shows this form of Sigma-2 to have a SiO2/Al2O3 molar ratio of about 90:1.

Table 2 X-Ray Diffraction Data for "As-made" Product of Example 1

I d(A) 1/lo d(A) I/lo I 9.75 13.8 2.87 4.8 8.56 3.7 2.83 8.6 I 7.61 1.3 2.76 7.7 5.70 1.2 2.62 11.7 4.53 100.0 2.59 8.0 I 4.48 81.0 2.56 5.9 4.39 28.8 2.50 7.9 I 4.29 10.1 2.39 1.1 4.24 7.9 2.29 2.9 3.81 11.0 2.27 1.3 3.62 3.9 2.25 2.6 I 3.58 2.3 2.22 5.5 3.39 17.2 2.13 3.1 3.33 36.6 2.05 1.3 3.29 5.8 2.02 7.7 3.11 1.1 1.99 3.5 3.05 9.7 1.96 3.6 2.99 14.3 1.90 6.2 1.85 2.02 Table 3 X-Ray Diffraction Data for Calcined form of Sigma-2 as prepared in Example 1

I d(A) I/Io d(A) I/Io 9.77 71.3 2.87 7.7 I 8.57 23.5 2.83 7.4 7.61 18.0 2.80 4.3 I 6.66 17.7 2.76 10.3 5.70 8.9 2.63 14.6 I 5.11 2.4 2.59 9.8 4.90 1.4 2.56 7.1 4.54 100.0 2.50 10.8 4.49 70.9 2.39 1.5 I 4.40 25.1 2.29 3.3 I 4.30 9.9 2.25 2.4 4.25 5.8 2.22 4.5 3.81 11.1 2.15 1.4 I 3.62 4.1 2.13 3.5 3.58 2.8 2.05 1.8 3.40 18.1 2.02 7.3 3.34 37.0 1.99 5.2 3.29 25.2 1.96 3.5 I 3.06 11.4 1.90 7.2 I 2.99 14.2 1.85 2.3 Example 2 This example illustrates the synthesis of a very high-silica form of Na, K, adamantanamine Sigma-2 using 1-adamantanamine (AN).

The synthesis mixture had the following molar composition ratios: 0.85Na2O:3 K2O : 20 AN : 60SiO2 : 2400H20 25.2 g AN was dispersed in 101.5 g colloidal silica (Syton X30) and then 200 g water was added to give Mixture A. 2.80 g KOH was added to 88.9 g water to give Mixture B. Mixture B was added to Mixture A with stirring at room temperature and the resulting mixture was stirred for 30 minutes before charging to a 1 litre capacity stainless steel autoclave. After sealing the autoclave, the reaction mixture was heated ta 1800C and maintained at that temperature under autogenous pressure for 96 hours with stirring at approximately 500 rpm. At the end of this time, the reactor and its contents were cooled to room temperature and discharged. The product was filtered and washed thoroughly with deionised water (about 2 litres) and the resulting solid was dried in an oven at 110 C overnight. The yield was about 26 g.

The X-ray diffraction pattern of this solid is shown in Table 4. Chemical analysis of the product showed it to contain the following elements at the levels given: Carbon 5.6 wt %, Nitrogen 0.8 wt %, Silicon 38.5 wt %, sodium 0.041 wt %, Alumi nium < 0.05 wt % and Potassium 0.18 wt %. Calculation shows the product to have a SiO2/A12O3 molar ratio of > 1480:1.

Table 4 X-Ray Diffraction Data for "As-made" Product of Example 2

d(A) I/Io d(A) I/Io 9.72 14.4 2.86 5.1 I 8.53 3.7 2.82 9.2 7.58 1.3 2.80 3.3 I 6.63 0.6 2.75 8.8 5.68 1.1 2.62 13.4 4.89 1.0 2.58 9.0 I 4.52 100.0 2.56 7.7 I 4.47 84.8 2.50 10.0 4.38 29.6 2.39 1.6 4.28 9.8 2.33 1.1 4.24 8.9 2.29 3.7 4.08 1.5 2.27 1.6 3.80 11.5 2.24 3.2 3.61 3.7 2.21 7.7 I 3.57 2.1 2.14 1.4 I 3.39 18.5 2.12 4.3 3.33 39.1 2.05 2.2 3.28 25.3 2.01 12.1 3.26 6.2 2.00 4.2 3.17 1.2 1.98 7.0 3.10 1.96 5.6 I 3.05 10.0 1.94 1.3 3.02 2.0 1.90 9.5 I 2.98 15.6 1.89 5.3 1.84 3.2 Example 3 This example illustrates the synthesis of a very high-silica form of Na, adamantanamine Sigma2, using 1-adamantanamine (AN).

The synthesis mixture had the following molar composition ratios: 3Na2O : 20AN : 60SiO2 : 2400H20 25.2 g AN was dispersed in 101.5 g colloidal silica (Syton X30) and then 200 g water was added to give Mixture A. 1.435 g NaOH was added to 88.9 g water to give Mixture B. Mixture B was added to Mixture A with stirring at room temperature and the resulting mixture was stirred for 30 minutes before charging to a 1 litre capacity stainless steel autoclave. After sealing the autoclave, the reaction mixture was heated to 180 C and maintained at that temperature under autogenous pressure for 120 hours with stirring at approximately 500 rpm. At the end of this time, the reactor and its contents were cooled to room temperature and discharged.

The product was filtered and washed thoroughly with deionised water (about 2 litres) and the resulting solid was dried in an oven at 110or overnight. The yield was about 28 g.

The X-ray diffraction pattern of this solid is shown in Table 5. The presence of additional lines in the X-ray diffraction pattern would appear to be due to low levels of Sigma-1, probably at a level of about 6% by weight. Chemical analysis of the product showed it to contain the following elements at the levels given: Carbon 6.8 wt %, Nitrogen 0.9 wt %, Silicon 34.2 wt %, Aluminium < 0.05 wt % and Sodium 0.18 wt %. Calculation shows the product to have a SiO2/AI203 molar ratio of > 1314:1.

Table 5 X-Ray Diffraction Data for "As-made" Product of Example 3

I d(A) I/Io d(A) I/Io I 9.73 14.0 2.86 5.1 8.53 3.4 2.82 9.3 7.58 1.0 2.80 2.9 I 5.73 2.1 2.75 8.9 I 5.68 1.0 2.62 13.7 5.15 2.6* 2.58 8.9 4.89 1.2 2.55 7.3 I 4.83 1.5* 2.50 9.8 I I 4.68 1.8* 2.42 1.0 I 4.52 100.0 2.39 1.7 I I 4.48 84.0 2.33 1.3I I 4.38 29.4 2.29 3.4 4.28 9.5 2.27 1.9 I 4.24 8.6 2.24 3.4 4.13 1.2 2.21 7.7 3.80 12.0 2.15 1.3 3.61 3.9 2.12 4.5 3.57 2.4 2.05 2.0 3.39 19.7* 2.01 11.6 3.33 38.7* 2.00 3.9 3.28 26.1* 1.98 6.7 3.26 6.8 1.96 4.9 3.17 1.2 1.94 1.2 3.10 1.1 1.89 9.1 3.05 11.2 1.85 2.9 3.02 2.4 2.98 16.3 * Probably due at least in part to the presence of a low level of zeolite Sigma-1.

Example 4 This example illustrates the synthesis of Sigma-2 using 1-adamantanamine and a temperature of 200"C.

The synthesis mixture had the following molar composition ratios: 3Na2O : 20AN : Awl203: 60 Six2: 2400 H2O 25.2 g AN was dispersed in 101.5 g colloidal silica (Syton X30) and then 200 g water was added to give Mixture A. 0.616 g NaOH was added to 2.34 g sodium aluminate ("Technical" grade, British Drug Houses, of molar composition 1.229 Na2O : Awl203 : 5.7 H2O) and then 88.9 g water was added to give Mixture B. Mixture B was added to Mixture A with stirring at room temperature and the resulting mixture was stirred for 30 minutes before charging to a 1 litre capacity stainless steel autoclave.After sealing the autoclave, the reaction mixture was heated at 200"C and maintained at that temperature under autogenous pressure for 50 hours with stirring at approximately 500 rpm. At the end of this time, the reactor and its contents were cooled to room temperature and discharged. The product was filtered and washed thoroughly with deionised water (about 2 litres) and the resulting solid was dried in an oven at 110 C overnight. The yield was about 29 g.

The X-ray diffraction pattern of this product showed it to be highly crystalline, mostly Sigma-2 but with additional lines due to another crystalline phase. From the position and relative intensity of the additional lines in the pattern, it was probable that this other phase was zeolite Sigma-1 present at a level of about 4% in the product mixture. Chemical analysis showed the product mixture to have a SiOJAl2O3 molar ratio of about 44:1.

Example 5 This example illustrates the synthesis of Na,K, adamantanamine Sigma-2 using 1-adamantanamine (AN).

The synthesis mixture had the following molar composition ratios: 0.85Na2O : 3K2O : 20 AN : Awl203: 60 Ski02 : 2400 H2O 25.2 g AN was dispersed in 101.5 g colloidal system (Syton X30) and then 200 g water was added to give Mixture A. 0.86 g KOH was was added to 5.89 g potassium aluminate solution (1 .90K2O : Awl203 : 23.66H2O) and then 85.4 g water was added to give Mixture B. Mixture B was then added to Mixture A with stirring at room temperature and the resulting mixture was stirred for 30 minutes before charging to a 1 litre capacity stainless steel autoclave.After sealing the autoclave, the reaction mixture was heated to 180"C and maintained at that temperature under autogenous pressure for 120 days with stirring at approximately 500 rpm.

At the end of this time, the reactor and its contents were cooled to room temperature and discharged. The product was filtered and washed thoroughly with deionised water (about 2 litres) and the resulting solid was dried in an oven at 110"C overnight. The yield was about 319.

The X-ray diffraction pattern of this product showed it to be highly crystalline, mostly Sigma2, but with additional lines due to another crystalline phase. From the position and relative intensity of the additional lines in the pattern, it was probable that this other phase was zeolite Sigma-1, present at a level of 4% in the product mixture. Chemical analysis showed the product mixture to have a SiO2/AI203 molar ratio of about 48:1.

Claims (12)

1. A crystalline metallosilicate material, designated Sigma-2, which has a composition (in terms of mole ratios of oxides) expressed by the formula: 0.1 to 1.5 R2O : Y2O3 : at least 20 XO2 : 0 to 4000H2O wherein R is a monovalent cation or 1/n of a cation of valence n, X is silicon and/or germanium, Y is one or more of aluminium, iron, chromium, vanadium, molybdenum, arsenic, antimony, manganese, gallium and/or boron and H2O is water of hydration additional to water notionally present when M is H, and having an X-ray diffraction pattern substantially as set out in Table 1.

2. A crystalline metallosilicate as claimed in claim 1 wherein the composition (in terms of mole ratios of oxides) is expressed by the formula: 0.1 to 1.5 R2O: Y2Q : at least 20 X02 : 0 to 200 H2O

3. A crystalline metallosilicate as claimed in claim 1 or 2 wherein the XO2/Y2O3 mole ratio is in the range 30:1 to 5000:1.

4. A crystalline metallosilicate as claimed in claim 1 as freshly made having a molar composition: 0.1 to 1.5 M2O: 0.1 to 120 Q: Y2O3 : 40 to 5000 XO2 : 0 to 2000 H2O wherein M is an alkali metal and/or ammonium and can include hydrogen and Q is as hereinbefore defined.

5. A method for the preparation of metallosilicate Sigma-2 as defined in claim 1 which comprises reacting an aqueous mixture containing sources of at least one oxide XO2, optionally at least one oxide Y2O3, at least one oxide L20 and a source of a nitrogen-containing organic cation or base comprising an amine or quaternary ammonium compound or a derivative thereof or a precursor thereof where L is an alkali metal or ammonium.

6. A method as claimed in claim 5 wherein the reaction mixture has a composition in terms of mole ratios of oxides of: XO2/Y2O3 in the range 25:1 to 5000:1 LOH/XO2 in the range 10-3:1 to 1.0:1 H2O/XO2 in the range 10:1 to 200:1 Q/XO2 in the range 0.005:1 to 4:1 NZ/XO2 in the range 0 to 4.0:1 where X, Y, 0 and L are as hereinbefore defined, and N is an alkali metal or ammonium ion which may be the same as L or a mixture of L and another alkali metal or ammonium ion necessary to balance the anion Z which comprises a strong acid radical added as a salt of N or present as the result of an acid form of 0 being used.

7. A method as claimed in claim 5 or 6 wherein the source of nitrogen-containing organic cation or base is a cyclic amine.

8. A method as claimed in claim 7 wherein the cyclic amine is an adamantanamine.

9. A method as claimed in any one of claims 5 to 8 wherein the alkali metal L is sodium and/or potassium.

10. A method as claimed in claim 9 wherein L is sodium and the reaction mixture has a XO2/Y203 mole ratio greater than 75:1.

11. A catalyst or sorbent comprising metallosilicate Sigma-2 as claimed in any one of claims 1 to 4.

12. A catalytic process employing the catalyst claimed in claim 11.