Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF CRYSTALLINE POROUS ALUMINOSILICATE ZEOLITE

Abstract

An improved process for the preparation of crystalline porous aluminosilicate zeolite by mixing at room temperature, a source of silica, SiO2, a source of aluminum oxide, Al203, optionally a source of alkali metal oxide preferably Na20 or K20 or mix - ture thereof, optionally a nitrogen containing organic base or quaternary ammonium salt, commonly known as template, water, and a source of promoter at room temperature, heating the resultant reaction mixture in the temperature range 70 - 200°C for 2 to 200 hours, filtering, washing, drying and calcining the resultant solid composite material in the temperature range 300 - 700°C, subjecting the composite material to a conventional ion-exchange treatement, filtering, washing with water, drying and calcining at a temperature in the range of 300-700°C to obtain the aluminosilicate zeolite.

Full Text

This invention relates to an improved process for the production 88 of crystalline, porous aluminosilicate 88 zeolites. Zeolites are an important class of solid, crystalline, microporous materials because of their unique catalytic and adsorption properties. Zeolites are crystalline solid alurainosilicates with three dimensional frame-work composed of [SiO4]4- and [A1O4]5-tetrahedra in sucli a way that two aluminiums are not adjacent. Zeolites are represented as: (Formula Removed) where M is a charge coupansating cation with valence n, genarally an element from group 1 or II of the periodic table or an organic cation. The ratio of x/y can be one or more. Z represents the number of water molecules which are reversibly adsorbed in the zeolite pores. These zeolites are commonly prepared under hydrothermal conditions at autoger.eous pressure. Generally, the reaction mixture, comprising «:f the sources of silica, alumina, alkali cation and optionally a nitogen containing organic template selected from corimon.y used mono or di quaternary ammonium compounds or amines, is filled in a container which is then closed to the extent o:: air tightness, heated in the range 80-200 °C for few hours to fet days or even weeks till fully crystalline material is obtained. Depending upon the chemical composition, method of preparatr.on, organic template and temperature and time required for crystallization, various zeolites with different chemical compositions and crystallographic dimentions are formed. [See; (1): P.A. Jacobs and J.A. Martens, Studies in Surface Science and Catalysis vol. 33, year 1987; (2):H.G. Karge and J. Weitkamp (editors), Studies in Surface Science and Catalysis, vol 46 year 1989]. The major drawback of "he prior art method for the preparation of zeolites is that the desired material(s), prepared by optimizing the various synthesis parameters like the composition of the starting reaction mixture and crystallization temperature, require relatively lower time to obtain the desired material. Further, this process of optimazation of synthesis parameters is required for each individual zeolite composition and structure. Furthermore, in nost of the cases, particularly wherein x/y ratio is 10 or more, :he time required is quite long, generally ranging between 1 to 10 days in the temperature range of 100 to 200 °C [see P.A. Jacobs and J.A. Martens, Studies in Surface Science and Catalysis vol. 33, year 1987]. Another drawback of the prior art methods of preparing zeolites, is that due to relativlely long crystallization time, generally large distribution of partcle or crystallite size and shape is obtained mainly due to secondary crystallization and overlaping nucleation and crystallization processes during hydrothermal syntheis of zeolites. This inhomogeneous disribution of crystallites size and shape adversally affect the catalytic properties of the zeolites. Apart from this, the loger crystallization time at higher temperature consumes more energy and thus adding to the cost of the material. The main objective of the present invention therefore is to develop a general method for efficient and faster synthesis of zeolites, represented by the general formula given herein before, by using some promoters, which are the oxianions (oxiacids or their salts) of the elements selectecd from groups V A and VII A of the periodic table and can be represented by a common formula as given below and herein after mentioned as promoter : (Formula Removed) where M is charge balancing cation of valency n, E is a cation of charge e of an element from group V A or VII A, 0 is an oxygen anion with -2 valency and z, net negative charge on (E04)x~ anion, where x — -:i + e (where e may be 5 or 7) . More specifically, M may be a monovalent or a divalent cation selected from H+, Li+, Na+, K+, Cs+, NH4+, Mg2+, Ca2+ or mixtures thereof, and Ee+ may J:e P5+, As5+, Sb5+, Cl5+, Br5+, I5+, Cl7+, Br7+ or I7+, e.g. H3PO°1, H3ASO4' HClO4 etc. Accordingly the ma:.n objective of present invention is to provide an improved process for efficient and significantly faster preparation of zeolites using promoters. Another objective of the present invention is to provide an improved process for the preparation of zeolite at a reduced crystallization time and / or crystallization temperature. Accordingly, the present invention describes an improved process for the preparation of zeolites of the formula: (Formula Removed) (where M is a charge compensating cation of valence n, an element from group I or II of the periodic table selected fron H+. Li+, Na+, K+, Cs+, NH4+, Mg2+, Ca2+ or mixtures thereof, or ai: organic cation and where the ratio x/y can be one or more and z represents the number of water molecules which comprises mixinc a- room temperature, (a) a source of silica, (b) a source of alumina, (c) optionally a source of alkali metal oxide, (d optionally a nitrogen containing organic base or quaternary amm<:nium salt commonly known as template a source of promoter having formula mz and water at room temperature heating the resultant mixture temerature ranging betveen for period from to hours filtering washing drying calcining solid conpos te material in range subjecting resulting composite conventional ion-exchange treatement with> In one of the embodiments of the present invention the source of silica is selected from fumed silica, silica sol, sodium silicate and tetraethyl ortho silicate. In another embodiment of the present invention the source of alumina is selected from Al (SO ) .16H 0; Al(NO ) .9H 0, 2 4 3 2 3 3 2 aluminium isopropoxide, sodium aluminate and catapol B. In another embodiment of the present invention the templates are selected from primary secondary and tertiary amines, mono and di-qutarnary ammonium halide/hydroxide. In yet another embodiment of the invention, the source of alkali metal oxide is selected from LiOH, NaOH, NH OH, CsOH, 4 MgO, CaO or their mixtures thereof. In yet another embodiment of the present invention the source of promoters are selected from HC10 , NaClO , KC10 , 4 4 4 H PO , Na HPO , Na PO , K PO , Na HAsO and K HAsO . 34 24 3434 2 4 2 4 The preferred molar composition of the starting reaction mixture, gel1 can be represented as: SiO : 0-0.5 AlO : 0-0.5 2 2 3 NaO : 0-0.5 T : 0.01-0.5 R : 20-60 HO (where T is a conven- 2 2 tionaily used nitrogen containing organic base or quaternary (both mono and di) ammonium salt and R is a promoter. However, in a more preferred embodiment of the present invention, the value of R may range between 0.05 and 0.2. The process of the present invention is described in the following examples which are, illustrative and should not to be construed to limit the scope of the present invention, in any manner. Example 1. This example illustrates the influence of different promoters in the synthesis of the zeolite, which is characterized by the value of x/y .> 10 in the formula given above. The process was repeated using different promoters mentioned in table 1. 60 g of fumed Si02 was stirred with 10 g of NaOH and 254 g of tetrapropyl ammonium hydroxide for 1 hr. Then 15.8 g of aluminium sulphate (16 H20) taken in 100 g of water was added into it with vigorous stirring. finally the quantity of the promotor specificed in table 1 was added into the gel with the rest amount of water (200 g and the stirring was continued of another 1 hr. The gel was charged into stainess steel autoclaves in the temperature range 100-170 °C for 6-48 hrs When the crystallization is over, the products were filtered, thoroughly washed with water, dried at 100°C and calcined. The molar composition of the gel in terms of the moles of oxides was: SiO2 : 0.05 A12O3 : 0.125 Na2O : 0.125 (TPA)2O : 30 H2O. The details of the promotor, the autoclave temperature and the crystallizcitior time is tabulated in table 1 below. Table 1 (Table Removed) It is evident from tie above table that the the use of promotor has considerably reouced the crystallization time thereby reducing the time required for the synthesis of catlyst. The catalyst prepared was characterised by x ray diffraction method and the x ray diffraction pattern is tabulated in Table 2 Table 2 X~Ray powder diffraction pattern (Table Removed) where d and I/Io represent, here and hereafter in tables 1-11, lattice spacing and the relative intensity of the XRD peak with respect to the intensity of the most intense XRD peak of the particular structure, respectively. Example 2 This example illustrates the influence of promoters in the synthesis of the zeoli:e, which is characterized by the value of x/y > 3 000 in the formula given above, and the powder x-ray diffraction pattern qiven in Table 4, with and without a promoter. 18 g of fuined Si02 was stirred with 3 g of NaOH and 76.2 g of tetrapropyl .unmonium hydroxide (20 wt%, aqueous) for 1 hr. Finally the quantity of~the promotor specificed in table 3 was added into the gel with the rest amount of water (108 g) and the stirring was continued of another 1 hr. Finally the gel was charged into stainess steel autoclaves in the temperature range 100-170°C for 6-48 as mdicatid in the table 3 When the crystallization was over, the products were filtered, thoroughly washed with water, dried at 100°C and calcined. The molar composition of the gel in terms of the moles of oxides was: SiO2 : 0.125 Na2O : 0.125 (TPA)2O : 30 H2O. The details of the promotor, the autoclave temperature and the crystallization time is tabulated in table 3 below. Table 3 (Table Removed) It is evident from te above table that the the use of promotor has considerably reduced the crystallization time thereby reducing the time required for the synthesis of catlyst. The catalyst was characterised by x ray diffraction and the results are tabulated in table 4 Table 4 X-Ray powder diffraction pattern (Table Removed) Example 3 This example illustrates the synthesis of zeolite with x/y = 20 to 200 XRD pattern of which is given in Table 3, with and without the use of promoters. 6 g of fumed SiO2 was stirred with 0.67 g of NaOH and 25.2 g of tetramethyl ammonium hydroxide (TMAOH, 25% aq.) solution for 1 hr. Then 1.58 g of aluminium sulphate dissolved in 10 g of water was added into it. Finally promoter taken in the remaining amount of water was added into the gel and the stirring was continued for another 1 hr. Finally, the gel was autoclaved at 170°C :or 1-5 d. The molar gel composition was: SiO. 0.05 A1203 : 0.08 Na2 : 0.25 (TMA)20 : 35 H20. The details of promoter, autoclave temperature and the crystallization time is tabulated in table 5 below. Table 5 (Table Removed) Example 4. This example illuatra:es the synthesis of zeolite characterized by x/y = 10 - 100 and XRD pattern given in table 4 and the role of those promoters in its synthesis. 8 g of fumed Si02 was stirred with 0.53 g of NaOH, 0.37 g of KOH and 25.4 g of tetraethyl ammonium hydroxide (TEAOH) in 10 g of H20 for 1 hr. Then 2.8 g of aluminit;.m sulphate dissolved in 10 g of water was added slowly into it. Finally promoters inthe quantities mentioned in table 7 iaken in the rest amount of water was added into the gel and the s.irring was continued for another lhr. Then the gel was autoclnved at 140°C for l-7d. The gel composition in terms of the moles of cxides was: SiO2: 0.025 Na2O : 0.0125 K2O: 0.033 A12O3: 0.25 -TEA2O : 25 H2O. The details of the promotor, the autoclave temperature and the crystallization time is tabulated in table 7 below. Table 7 (Table Removed) Table 8 XHRay powder diffraction pattern Example 5. This example illustrates the utility of promoters in the synthesis of zeolrete as characterized by x/y = 40 -2000 and XRD pattern given in Table 5. 6 g of fumed SiO2 was stirred with 25.4 g of hexamethylene bis(benzyl dimethyl ammonium hydroxide) (ROH, 15% aq.) and 1 g of N OH taken in 10 g of water for 1 hr. Then 0.2 g of aluminium sulphate taken in 10 g of water was added into it under vigorous stirring. Finally the quantity of promoter (as indicatead in table 9 was added into the gel with the rest amount of water and stirring was continued for another 1 hr. Then the content was charged into stainless steel autoclave at 160°C for 1- 6 d. The gel composition in terms of the moles of oxides were : SiO2 : 0.00625 A12O3 : 0.125 Na2O : 0.1 ROH : 30 H2O. The details of the promotor, the autoclave temperature and the crystallization time is tabulated in table 9 below. Table 9 (Table Removed) Table 10 X-Ray powder diffraction pattern (Table Removed) Example 6. This example describes the role of promoters vis-a-vis their absence in the synthenis of zeolite characterized by x/y =40 2000 and XRD pattern given in Table 12. The same template as used in example 4 was used here. 6 g of fumed SiO2 was stirred with 1 g of NaOH and 43.2 g of ROH for 1 hr. Then 0.7 g of aluminium sulphate taken in 10 g of water was added into it under vigorous stirring. Finally the amount of promoters as indicated in table 11 was added into the gel and the stirring was continued for another 1 hr. Finally the content was autoclaved at 170°C without aggitation. The gel composition in terms of moles of oxides were : SiO2 : 0.011 A12O3 : 0.125 Na2O : 0.166 ROH : H2O. The details of the promotor the autoclave temperature and the crystallization tine is tabulated in table 11 below. Table 11 (Table Removed) Table 11 X~Ray powder diffraction pattern (Table Removed) Example 7. This example illustrates the synthesis of zeolite characterized by its x/y = 30 - 300 and XRD pattern gived in Table 14 and the role of various promoters in their synthesis. First 52.5 g of sodium silicate >25% aq.) solution was stirred with 50 ml of water for 15 m. Tt.en a. 6 g of pyrrolidine (R) was added into it and the solution was istirred for another 0.5 hr. Then 2.4 g of aluminium sulphate, along with promoters in the quantities indicated in tablts 13 were slowly added in the remaining amount of water. Stirring was continued for another lh before autoclaving at 160°C.H of the final gel ranges between 12.0 to 12.4. Final gel conposition, in terms of moles of oxides was: 55 SiO2 : Al2O3 : 30 R : 8.5 Na2O : 2400 H2O. The details of the promotor, the autoclave temperature and the crystallization time is tabulated in table 13 below. Table 13 (Table Removed) Table 1.4 X-Ray powder diffraction pattern (Table Removed) Example 8. This example demonstrates the synthesis of zeolite with x/y = 1 and characterized through its XRD pattern given in Table 16 with and without the use of promoters. 18.2 g of sodium aluminate (43% A12O3, 39% Na2O) and 0.55 g of NaOH was dissolved in 40 g of water with constant stirring. Then 32 g of sodium silicate was added into it and the stirring was continued for another 1 hr. Then the required amount of promoter as indicated in table 15 was taken in rest amount of water was added into it. After stirring for another lh the gel was autoclaved at 60°C for 2-6 hr. The gel composition in terms of moles of oxides was: 1.75 SiO2 : A1203 : 2.25 Na2C) : 7 5 H20. The details of the promotor, the autoclave temperature and the crystallization time is tabulated in table 15 below. Table 15 Promotor St Autoclave (Table Removed) Table 16 X--Ray powder diffraction pattern (Table Removed) Example 9. This example describes the synthesis of zeolite as characterized by x/y = 40 - 400 and XRD pattern of Table 18 in presence and absence of promoters. 6g of fumed SiO2 was stirred with 0.4 g of NaOH and 2.4 g of pyrrolidine (R) taken in 15 g of water for 1 hr. Then 0.78 g of aluminium sulphate dissolved in 10 g of water was added into it with constant stirring. Finally promoters taken in the quantity indicated in table 17 in remaining amount of water was added into the gel with vigorous stirring. Stirring was continued for another 1 hr. Then the content was autoclaved at 170°C for 2-8 d. The gel composition in terms of the moles of oxides was: 80 Si02 : A12O3 : 4.0 Na2O : 8.0 R : 2400 H2O. The details of the promctor, the autoclave temperature and the crystallization time in tabulated in table 17 below. Table 17 (Table Removed) Table 1B X-Ray powder diffraction pattern (Table Removed) Example 10. This example illustrates the synthesis of zeolite as characterized by x/y =2-4 and XRD pattern given in Table 2 0 and the utility of the promoters in their synthesis. This synthesis was performed in two stages. In first step, the seed solution was prepared by mixing 2.77 g of NaOH and 0.78 g of sodium aluminate taken in 6 g of weiter and 11.5 g of sodium silicate and it was agged for 1 d. Then 24 g of sodium silicate was stirred with 10 g of water and to it. seed solution and 2.8 g sodium aluminate and 0.5 g of NaOH solution in 10 g of water was added simultaniously to it with vigorous stirring. Then 2.7 g of aluminium sulphate dissolved in 10 g of water was added into the gel and finally promoter inthe quantify mentioned in table 19 taken in 10 g of water was added into it with vigorous stirring. Finally the gel was autoclaved at 100°C for 3-12 hr. The molar gel composition of the constituents was: 6.0 SiO2 : A12O3 : 2.8 Na2O : 160 H2O. The details of the promotor, the autoclave temperature and the crystallization time is tabulated in table 19 below. Table 19 (Table Removed) Example 11. This example illustrates the synthesis of zeolite with x/y = 4-12 and XRD pattern of Table 22 and the role of the promoters in their synthesis. 5.7 g of catapol B (3 0% A12O3) was stirred with 11.2 g of KOH taken In 3 0 g of water. After 1 h 10 g of fumed silica was added slowly into it and the stirring was continued. Finally promoter inthe quantity mentioned in table 21, dissolved in 15 g of water was idded slowly into the gel and the stirring was continued for another 1 hr. Then the content was charged into a stainless steel, autoclave at 160°C for 1-6 d. The gel composition in terms of moles of oxides was : 10 SiO2 : 8.4 K2O : 1.0 A12O3 : 200 H2O. The details of the promotor, the autoclave temperature and the crystallization time is tabulated in table 21 below. Table 21 (Table Removed) The main advantageous feature of the present invention is that by using the promoters as mentioned earlier, the overall time required for the complete crystallization of the zeolites is considerably shortened thus saving time and energy / electricity and simultaneously increasing the manufacturing throughput in a given time. We claim 1. An improved process for the preparation of crystalline porous, aluminosi1icates, (commonly known as zeolite) having formula: (Formula Removed) Where M is a charge compansating cation with valence n, genarally an element from group I or II of the periodic table or an organic cation, x and y are the moles of silica and alumina present per unit cell of the zeolite respectively, and Z is the moles of water present per unit cell comprises mixing (a) a source of silica, (b) a source of aluminum oxide, (c) optionally a source of alkali metal oxide, (d) optionally a nitrogen containing organic base or quaternary ammonium salt, commonly known as template, (e) water, and (f) a source of promoter represented by the formula: M (EO ) , wherein M is z/n 4 z charge balancing cation of valency n, E is a cation of charge e of an element from group V A or VII A, 0 is an oxygen anion with -2 valency and z, net negative charge on x-(EO ) anion, where x = - 8 + e (where e may be 5 or 7), 4 more specifically, M may be a monovalent or a divalent + + + + + + 2+ cation selected from H , Li , Na , K , Cs , NH , Mg , 4 2+ e+ 5+ 5+ 5+ Ca or mixtures thereof, and E may be P , As , Sb , 5+ 5+ 5+ 7+ 7+7+ CI , Br , I , CI , Br or I , e.g. H PO , H AsO , 3 4 3 4 HC10 etc. at room temperature and heating the resultant 4 reaction mixtee in the temperature range 70 - 200 oC for 2 to 200 hours, filtering, washing, drying and calcining the resultant solid composite material at a temperature in the range of 300 - 700 oC, subjecting the resultant composite material to a conventional ion-exchange treatement, filtering, washing with water, drying and calcining at a temperature in the range of 300— 700«C . to obtain the above mentioned zeolite. 2. A process as claimed in claim 1 wherein the source of silica used is selected from fumed SiO , sodium silicate, 2 silica sol, tetraethyl orthosi1icate or mixtures thereof. 3. A process as claimed in claims 1 It 2 wherein the source of alumina used as selected from Al2O3 , Al2(SO4)3 , Al(NO3)3 , aluminium isopropoxide or mixtures thereof. 4. A process as claimed in claims 1 to 3 wherein the source of alkali metal oxide is selected from LiOH, NaOH, KOH, NH OH, CsOH, MgO, CaO etc. or their mixtures thereof. 4 5. An improved process for preparing crystalline alumino sili cate zeolite catalyst composite materials as substan tially described herein with reference to examples 1 to 11.

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