Method for preparation of mordenite

Abstract

The present invention provides a method for preparing a mordenite, which is a method for preparing the mordenite through a hydrothermal crystallization by using natural aluminosilicate minerals as total silicon sources and total aluminum sources, comprising the steps of: subjecting the natural aluminosilicate minerals to activation treatment which is an activation by sub-molten salt and an activation by thermal treatment; selecting and mixing the activated natural aluminosilicate minerals according to the silicon-to-aluminum ratio of the targeted mordenite, adding thereto deionized water, sodium hydroxide, crystal seed, a templating agent to obtain a reaction mixture; adjusting the reaction mixture by using an inorganic acid to have a pH of 10-13, and then aging it at 40-80° C. for 6-24 hours; and subjecting the aged reaction mixture to hydrothermal crystallization, and then filtering, washing, drying and calcinating the crystallized product to obtain the mordenite. The method for preparing a mordenite provided in the present invention enlarges the sources of raw materials for a molecular sieve, has a low cost and a simple process route, and can largely reduce the cost for synthesizing a molecular sieve.

Claims

1. A method for preparing a mordenite, which is a method for preparing the mordenite through a hydrothermal crystallization by using natural aluminosilicate and silicate minerals as total silicon sources and total aluminum sources, comprising the steps of: subjecting the natural aluminosilicate and silicate minerals to activation treatment which is a sub-molten salt activation and/or a thermal treatment activation; selecting and mixing the activated natural aluminosilicate and silicate minerals according to the silicon-to-aluminum ratio of the targeted mordenite, adding thereto deionized water, sodium hydroxide, crystal seed, a templating agent to obtain a reaction mixture having a composition by mole of SiO.sub.2:Al.sub.2O.sub.3=10-40:1, H.sub.2O:SiO.sub.2=30-90:1, Na.sub.2O:SiO.sub.2=0.1-0.4:1, and the templating agent: SiO.sub.2=0-0.6:1, in which the crystal seed is added in amount of 0-10 wt % based on the total mass of the reaction mixture; adjusting the reaction mixture by using an inorganic acid to have a pH of 10-13, and then aging it at 40-80° C. for 6-24 hours; and where the templating agent is not added, subjecting the aged reaction mixture to hydrothermal crystallization, and then filtering, washing and drying the crystallized product to obtain the mordenite; and where the templating agent is added, subjecting the aged reaction mixture to hydrothermal crystallization, and then filtering, washing, drying and calcinating the crystallized product to obtain the mordenite.

2. The method for preparing a mordenite according to claim 1, wherein the natural aluminosilicate minerals include one of kaolin, rectorite, montmorillonite, illite, perlite and bentonite, or combinations of more than one members thereof, and the natural silicate minerals include one of diatomaceous earth and white carbon black, or combinations thereof, wherein the one of diatomaceous earth and white carbon black, or combinations thereof are used as a portion of the silicon sources, and the one of kaolin, rectorite, montmorillonite, illite, perlite and bentonite, or combinations of more than one members thereof are used as a portion of the silicon sources and total aluminum sources.

3. The method for preparing a mordenite according to claim 2, wherein the diatomaceous earth, white carbon black are subjected to activation treatment via the sub-molten salt activation or the thermal treatment activation method; the thermal treatment activation for diatomaceous earth, white carbon black is carried out by calcinating the diatomaceous earth or white carbon black at 600-1000° C. for 2-6 hours; and the sub-molten salt activation for diatomaceous earth, white carbon black is carried out by mixing the diatomaceous earth or white carbon black with an alkaline substance and deionized water at a mass ratio of 1:0.5-3.5:1-15, and then baking the mixture at 100-350° C. for 2-6 hours.

4. The method for preparing a mordenite according to claim 3, wherein the kaolin, rectorite, montmorillonite, illite, perlite, bentonite are subjected to activation treatment via the sub-molten salt activation; the sub-molten salt activation for kaolin, rectorite, montmorillonite, illite, perlite, bentonite is carried out by mixing the kaolin, rectorite, montmorillonite, illite, perlite or bentonite with an alkaline substance and deionized water at a mass ratio of 1:0.5-3.5:1-15, and then baking the mixture at 100-350° C. for 2-6 hours.

5. The method for preparing a mordenite according to claim 4, wherein the alkaline substance includes one of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, or combinations of more members thereof.

6. The method for preparing a mordenite according to claim 3, wherein the alkaline substance includes one of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, or combinations of more members thereof.

7. The method for preparing a mordenite according to claim 2, wherein the kaolin, rectorite, montmorillonite, illite, perlite, bentonite are subjected to activation treatment via the sub-molten salt activation; the sub-molten salt activation for kaolin, rectorite, montmorillonite, illite, perlite, bentonite is carried out by mixing the kaolin, rectorite, montmorillonite, illite, perlite or bentonite with an alkaline substance and deionized water at a mass ratio of 1:0.5-3.5:1-15, and then baking the mixture at 100-350° C. for 2-6 hours.

8. The method for preparing a mordenite according to claim 7, wherein the alkaline substance includes one of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, or combinations of more members thereof.

9. The method for preparing a mordenite according to claim 1, wherein the crystal seed is a mordenite molecular sieve.

10. The method for preparing a mordenite according to claim 1, wherein the templating agent is one of tetraethylammonium bromide (TEABr), tetrapropylammonium bromide (TPABr), triethanol amine, diethanol amine and caprolactam, or combinations of more members thereof.

11. The method for preparing a mordenite according to claim 1, wherein the hydrothermal crystallization is carried out using a two-stage crystallization having firstly a pre-crystallization at 100-120° C. for 24-48 hours and then a crystallization at 170-190° C. for 24-48 hours.

12. The method for preparing a mordenite according to claim 1, wherein the inorganic acid includes one of sulfuric acid, hydrochloric acid and nitric acid, or combinations of more members thereof.

13. A mordenite which is prepared by the method for preparing a mordenite according to claim 1, wherein the mordenite has a relative crystallinity of 80%-110% and a silicon-to-aluminum ratio of 5-35.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a X-ray diffraction (XRD) pattern of the mordenite as prepared in Example 1.

(2) FIG. 2 is an scanning electron microscope (SEM) image of the mordenite as prepared in Example 1.

(3) FIGS. 3 to 12 are XRD patterns of the mordenites as prepared in Examples 2 to 11, respectively.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(4) The technical solutions in the present invention are further described in detail in order to provide more explicit understandings of technical features, objectives and beneficial effects of the present invention, which cannot be construed as limitations for the implementable scopes of the present invention.

(5) In the Examples, the natural aluminosilicate and silicate minerals in raw materials for synthesizing a molecular sieve are of industrial grade, while other chemical raw materials are of reagent grade. The relative crystallinity as mentioned in the Examples is a ratio, expressed in percentage, of sum of characteristic peak areas in the XRD pattern at 2θ=6.51°, 9.77°, 13.45°, 22.20°, 25.63°, 26.25° and 27.67° of the obtained product to sum of those of a mordenite standard sample, which is a commercial mordenite (a mordenite from the Catalyst Plant of Nankai University, Tianjin) as synthesized with conventional chemical agents as raw materials, and having a crystallinity of 100% as defined.

(6) In the Examples, the data of XRD is measured by a Bruck AXS D8 Advance type X-ray diffractometer from Germany, and the SEM images are obtained by a FEI Quanta 200F field emission scanning electron microscope from Holland.

Example 1

(7) This example provides a method for preparing a mordenite, wherein the used diatomaceous earth having main components of 93.6 wt % of SiO.sub.2 and 3.2 wt % of Al.sub.2O.sub.3, rectorite having main components of 41.3 wt % of SiO.sub.2 and 38.2 wt % of Al.sub.2O.sub.3, kaolin having main components of 50.5 wt % of SiO.sub.2 and 44.6 wt % of Al.sub.2O.sub.3, montmorillonite having main components of 61.5 wt % of SiO.sub.2 and 18.2 wt % of Al.sub.2O.sub.3, and illite having main components of 60.9 wt % of SiO.sub.2 and 24.8 wt % of Al.sub.2O.sub.3, are all commercially available.

(8) The method for preparing a mordenite is carried out according to steps as below:

(9) baking the diatomaceous earth as commercially available to dryness and crushing it into powders, weighing 50.00 g of the diatomaceous earth powders and calcinating them at 800° C. for 4 hours to obtain an thermal activated diatomaceous for use;

(10) baking the rectorite as commercially available to dryness and crushing it into powders, weighing 10.00 g of the rectorite powders, mixing them with 15.00 g of solid sodium hydroxide uniformly, adding thereto 75.00 g of deionized water and baking the resultant to dryness at 250° C. for 4 hours to obtain a sub-molten salt activated rectorite for use;

(11) weighing 4.2 g of solid TEABr and dissolving it into 10 g of deionized water to obtain a TEABr solution for use;

(12) weighing 10 g of a concentrated sulfuric acid with a mass percentage of 98%, adding it to 40 g of deionized water, and cooling the solution to room temperature, for use;

(13) weighing, separately, 6.0 g of the diatomaceous earth powders activated by thermal treatment, 2.2 g of the rectorite powders activated by sub-molten salt activation method, 1.6 g of solid sodium hydroxide, and the above TEABr solution, adding them to 50 g of deionized water and adjusting the pH by the sulfuric acid solution to have a pH of 12.5 to obtain a reaction mixture having a composition by mole of 18SiO.sub.2:Al.sub.2O.sub.3:6.3Na.sub.2O:4.1TEABr:540H.sub.2O;

(14) aging the reaction mixture at 70° C. for 24 hours before transferring it to a stainless-steel kettle for crystallization with a polytetrafluoroethylene liner, subjecting it to a pre-crystallization at 120° C. for 24 hours and then a static crystallization at 170° C. for 48 hours;

(15) upon the completion of crystallization, cooling and filtering the reaction product to remove mother liquor, washing it to have a neutral pH, drying it at 120° C. for 24 hours and then calcinating the resultant as obtained in a muffle furnace at 550° C. for 10 hours to remove the templating agent, so as to obtain the mordenite.

(16) The product mordenite has a relative crystallinity of 110% and a silicon-to-aluminum ratio of 12, and the XRD pattern and SEM images thereof are shown in FIGS. 1 and 2, respectively.

Example 2

(17) This example provides a method for preparing a mordenite, wherein the diatomaceous earth and the process for thermal activation thereof, and the processes for preparing the TEABr solution and the sulfuric acid solution are the same as those in the Example 1.

(18) The method for preparing a mordenite is carried out according to steps as below:

(19) baking the rectorite as commercially available to dryness and crushing it into powders, weighing 10.00 g of the rectorite powders, mixing them with 25.00 g of solid sodium hydroxide uniformly, adding thereto 125.00 g of deionized water and baking the resultant to dryness at 250° C. for 5 hours to obtain a sub-molten salt activated rectorite for use;

(20) weighing, separately, 6.0 g of the diatomaceous earth powders activated by thermal treatment, 3.5 g of the above rectorite powders activated by sub-molten salt activation method, and the TEABr solution, adding them to 50 g of deionized water and adjusting the pH by the sulfuric acid solution to have a pH of 13 to obtain a reaction mixture having a composition by mole of 18SiO.sub.2:Al.sub.2O.sub.3:6.3Na.sub.2O:4.1TEABr:540H.sub.2O;

(21) aging the reaction mixture at 70° C. for 24 hours before transferring it to a stainless-steel kettle for crystallization with a polytetrafluoroethylene liner, subjecting it to a pre-crystallization at 100° C. for 24 hours and then a static crystallization at 170° C. for 36 hours;

(22) upon the completion of crystallization, cooling and filtering the reaction product to remove mother liquor, washing it to have a neutral pH, drying it at 120° C. for 24 hours and then calcinating the resultant as obtained in a muffle furnace at 550° C. for 10 hours to remove the templating agent, so as to obtain the mordenite.

(23) The product mordenite has a relative crystallinity of 102% and a silicon-to-aluminum ratio of 11, and the XRD pattern thereof is shown in FIG. 3.

Example 3

(24) This example provides a method for preparing a mordenite, wherein the processes for activating diatomaceous earth and rectorite, and the processes for preparing the TEABr solution and the sulfuric acid solution are the same as those in the Example 1.

(25) The method for preparing a mordenite is carried out according to steps as below:

(26) weighing, separately, 6.0 g of the diatomaceous earth powders activated by thermal treatment, 0.5 g of the rectorite powders activated by sub-molten salt activation method, 2.4 g of solid sodium hydroxide, and the above TEABr solution, adding them to 50 g of deionized water and adjusting the pH by the sulfuric acid solution to have a pH of 13 to obtain a reaction mixture having a composition by mole of 35SiO.sub.2:Al.sub.2O.sub.3:12.2Na.sub.2O:8TEABr:1050H.sub.2O;

(27) aging the reaction mixture at 70° C. for 24 hours before transferring it to a stainless-steel kettle for crystallization with a polytetrafluoroethylene liner, subjecting it to a pre-crystallization at 110° C. for 24 hours and then a static crystallization at 170° C. for 48 hours;

(28) upon the completion of crystallization, cooling and filtering the reaction product to remove mother liquor, washing it to have a neutral pH, drying it at 120° C. for 24 hours and then calcinating the resultant as obtained in a muffle furnace at 550° C. for 10 hours to remove the templating agent, so as to obtain the mordenite.

(29) The mordenite has a relative crystallinity of 97% and a silicon-to-aluminum ratio of 26, and the XRD pattern thereof is shown in FIG. 4.

Example 4

(30) This example provides a method for preparing a mordenite, wherein the processes for activating diatomaceous earth and rectorite, and the processes for preparing the sulfuric acid solution are the same as those in the Example 1.

(31) The method for preparing a mordenite is carried out according to steps as below:

(32) weighing 2.0 g of solid TEABr and dissolving it into 10 g of deionized water to obtain a TEABr solution for use;

(33) weighing, separately, 2.8 g of the diatomaceous earth powders activated by thermal treatment, 1.0 g of the rectorite powders activated by sub-molten salt activation method, 0.75 g of solid sodium hydroxide, and the above TEABr solution, adding them to 50 g of deionized water and adjusting the pH by the sulfuric acid solution to have a pH of 11 to obtain a reaction mixture having a composition by mole of 18SiO.sub.2:Al.sub.2O.sub.3:6.3Na.sub.2O:4.1TEABr:1260H.sub.2O;

(34) aging the reaction mixture at 40° C. for 24 hours before transferring it to a stainless-steel kettle for crystallization with a polytetrafluoroethylene liner, subjecting it to a pre-crystallization at 100° C. for 24 hours and then a static crystallization at 170° C. for 48 hours;

(35) upon the completion of crystallization, cooling and filtering the reaction product to remove mother liquor, washing it to have a neutral pH, drying it at 120° C. for 24 hours and then calcinating the resultant as obtained in a muffle furnace at 550° C. for 10 hours to remove the templating agent, so as to obtain the mordenite.

(36) The mordenite has a relative crystallinity of 88% and a silicon-to-aluminum ratio of 10, and the XRD pattern thereof is shown in FIG. 5.

Example 5

(37) This example provides a method for preparing a mordenite, wherein the processes for activating diatomaceous earth and rectorite, and the process for preparing the sulfuric acid solution are the same as those in the Example 1.

(38) The method for preparing a mordenite is carried out according to steps as below:

(39) weighing, separately, 6.0 g of the diatomaceous earth powders activated by thermal treatment, 2.2 g of the activated rectorite powders by sub-molten salt activation method, 1.6 g of solid sodium hydroxide, and 4.6 g of triethanol amine (TEA), adding them to 60 g of deionized water and adjusting the pH by the sulfuric acid solution to have a pH of 12.5 to obtain a reaction mixture having a composition by mole of 18SiO.sub.2:Al.sub.2O.sub.3:6.3Na.sub.2O:5.4TEA:540H.sub.2O;

(40) aging the reaction mixture at 55° C. for 24 hours before transferring it to a stainless-steel kettle for crystallization with a polytetrafluoroethylene liner, subjecting it to a pre-crystallization at 120° C. for 24 hours and then a static crystallization at 170° C. for 36 hours;

(41) upon the completion of crystallization, cooling and filtering the reaction product to remove mother liquor, washing it to have a neutral pH, drying it at 120° C. for 24 hours and then calcinating the resultant as obtained in a muffle furnace at 550° C. for 10 hours to remove the templating agent, so as to obtain the mordenite.

(42) The mordenite has a relative crystallinity of 103% and a silicon-to-aluminum ratio of 12, and the XRD pattern thereof is shown in FIG. 6.

Example 6

(43) This example provides a method for preparing a mordenite, wherein the processes for activating diatomaceous earth and rectorite, and the process for preparing the sulfuric acid solution are the same as those in the Example 1.

(44) The method for preparing a mordenite is carried out according to steps as below:

(45) weighing, separately, 6.0 g of the diatomaceous earth powders activated by thermal treatment, 2.2 g of the rectorite powders activated by sub-molten salt activation method, 1.6 g of solid sodium hydroxide, and 0.7 g of crystal seed for mordenite (as manufactured by Catalyst Plant of Nankai University), adding them to 60 g of deionized water and adjusting the pH by the sulfuric acid solution to have a pH of 12 to obtain a reaction mixture having a composition by mole of 18SiO.sub.2:Al.sub.2O.sub.3:6.3Na.sub.2O:540H.sub.2O, wherein the amount of the crystal seed is 1.0 wt % based on the total weight of the reaction mixture;

(46) aging the reaction mixture at 70° C. for 24 hours before transferring it to a stainless-steel kettle for crystallization with a polytetrafluoroethylene liner, subjecting it to a pre-crystallization at 120° C. for 24 hours and then a static crystallization at 170° C. for 40 hours;

(47) upon the completion of crystallization, cooling and filtering the reaction product to remove mother liquor, washing it to have a neutral pH, drying it at 120° C. for 24 hours to obtain a crystallized product which is measured by XRD to have a phase pertaining to mordenite.

(48) The mordenite has a relative crystallinity of 90% and a silicon-to-aluminum ratio of 13, and the XRD pattern thereof is shown in FIG. 7.

Example 7

(49) This example provides a method for preparing a mordenite, wherein the processes for activating diatomaceous earth and rectorite, and the process for preparing the sulfuric acid solution are the same as those in the Example 1.

(50) The method for preparing a mordenite is carried out according to steps as below:

(51) weighing, separately, 6.0 g of the diatomaceous earth powders activated by thermal treatment, 2.2 g of the rectorite powders activated by sub-molten salt activation method, and 1.6 g of solid sodium hydroxide, adding them to 50 g of deionized water and adjusting the pH by the sulfuric acid solution to have a pH of 12.5 to obtain a reaction mixture having a composition by mole of 18SiO.sub.2:Al.sub.2O.sub.3:6.3Na.sub.2O:540H.sub.2O;

(52) aging the reaction mixture at 70° C. for 24 hours before transferring it to a stainless-steel kettle for crystallization with a polytetrafluoroethylene liner, subjecting it to a pre-crystallization at 120° C. for 24 hours and then a static crystallization at 170° C. for 24 hours;

(53) upon the completion of crystallization, cooling and filtering the reaction product to remove mother liquor, washing it to have a neutral pH, drying it at 120° C. to obtain a crystallized product which is measured by XRD to have a phase pertaining to mordenite.

(54) The product mordenite has a relative crystallinity of 86% and a silicon-to-aluminum ratio of 10, and the XRD pattern thereof is shown in FIG. 8.

Example 8

(55) This example provides a method for preparing a mordenite, wherein the process for activating diatomaceous earth, and the process for preparing the sulfuric acid solution are the same as those in the Example 1.

(56) The method for preparing a mordenite is carried out according to steps as below:

(57) weighing 3.5 g of solid TEABr and dissolving it into 10 g of deionized water to obtain a TEABr solution for use;

(58) baking the kaolin as commercially available to dryness and crushing it into powders, weighing 10.00 g of the kaolin powders, mixing them with 14.00 g of solid sodium hydroxide uniformly, adding thereto 70.00 g of deionized water and baking the resultant to dryness at 200° C. for 6 hours to obtain a sub-molten salt activated kaolin for use;

(59) weighing, separately, 4.0 g of the diatomaceous earth powders activated by thermal treatment, 0.95 g of the kaolin powders activated by sub-molten salt activation method, 1.1 g of solid sodium hydroxide, and the above TEABr solution, adding them to 50 g of deionized water and adjusting the pH by the sulfuric acid solution to have a pH of 12.5 to obtain a reaction mixture having a composition by mole of 20SiO.sub.2:Al.sub.2O.sub.3:7Na.sub.2O:4.6TEABr:1000H.sub.2O;

(60) aging the reaction mixture at 70° C. for 24 hours before transferring it to a stainless-steel kettle for crystallization with a polytetrafluoroethylene liner, subjecting it to a pre-crystallization at 120° C. for 24 hours and then a static crystallization at 170° C. for 48 hours;

(61) upon the completion of crystallization, cooling and filtering the reaction product to remove mother liquor, washing it to have a neutral pH, drying it at 120° C. for 24 hours and then calcinating the resultant as obtained in a muffle furnace at 550° C. for 10 hours to remove the templating agent, so as to obtain a product which is measured by XRD to have a phase pertaining to mordenite.

(62) The mordenite has a relative crystallinity of 104% and a silicon-to-aluminum ratio of 18, and the XRD pattern thereof is shown in FIG. 9.

Example 9

(63) This example provides a method for preparing a mordenite, wherein the process for activating diatomaceous earth, and the process for preparing the sulfuric acid solution are the same as those in Example 1. The process for preparing the TEABr solution is the same as that in Example 8.

(64) The method for preparing a mordenite is carried out according to steps as below:

(65) baking the montmorillonite as commercially available to dryness and crushing it into powders, weighing 10.00 g of the montmorillonite powders, mixing them with 15.00 g of solid sodium hydroxide uniformly, adding thereto 75.00 g of deionized water and baking the resultant to dryness at 250° C. for 5 hours to obtain a sub-molten salt activated montmorillonite for use;

(66) weighing, separately, 4.0 g of the diatomaceous earth powders activated by thermal treatment, 3.0 g of the montmorillonite powders activated by sub-molten salt activation method, 0.05 g of solid sodium hydroxide, and the TEABr solution, adding them to 60 g of deionized water and adjusting the pH by the sulfuric acid solution to have a pH of 12.5 to obtain a reaction mixture having a composition by mole of 20SiO.sub.2:Al.sub.2O.sub.3: 7Na.sub.2O:4.6TEABr:1000H.sub.2O;

(67) aging the reaction mixture at 70° C. for 24 hours before transferring it to a stainless-steel kettle for crystallization with a polytetrafluoroethylene liner, subjecting it to a pre-crystallization at 120° C. for 24 hours and then a static crystallization at 170° C. for 48 hours;

(68) upon the completion of crystallization, cooling and filtering the reaction product to remove mother liquor, washing it to have a neutral pH, drying it at 120° C. for 24 hours and then calcinating the resultant as obtained in a muffle furnace at 550° C. for 10 hours to remove the templating agent, so as to obtain a product which is measured by XRD to have a phase pertaining to mordenite.

(69) The mordenite has a relative crystallinity of 98% and a silicon-to-aluminum ratio of 15, and the XRD pattern thereof is shown in FIG. 10.

Example 10

(70) This example provides a method for preparing a mordenite, wherein the process for activating diatomaceous earth, and the process for preparing the sulfuric acid solution are the same as those in Example 1. The process for preparing the TEABr solution is the same as that in Example 8.

(71) The method for preparing a mordenite is carried out according to steps as below:

(72) baking the illite as commercially available to dryness and crushing it into powders, weighing 10.00 g of the illite powders, mixing them with 15.00 g of solid sodium hydroxide uniformly, adding thereto 75.00 g of deionized water and baking the resultant to dryness at 250° C. for 4 hours to obtain a sub-molten salt activated illite for use;

(73) weighing, separately, 4.0 g of the diatomaceous earth powders activated by thermal treatment, 1.98 g of the illite powders activated by sub-molten salt activation method, 0.6 g of solid sodium hydroxide, and the TEABr solution, adding them to 55 g of deionized water and adjusting the pH by the sulfuric acid solution to have a pH of 12.5 to obtain a reaction mixture having a composition by mole of 20SiO.sub.2:Al.sub.2O.sub.3:7Na.sub.2O:4.6TEABr:1000H.sub.2O;

(74) aging the reaction mixture at 70° C. for 24 hours before transferring it to a stainless-steel kettle for crystallization with a polytetrafluoroethylene liner, subjecting it to a pre-crystallization at 120° C. for 24 hours and then a static crystallization at 170° C. for 48 hours;

(75) upon the completion of crystallization, cooling and filtering the reaction product to remove mother liquor, washing it to have a neutral pH, drying it at 120° C. for 24 hours and then calcinating the resultant as obtained in a muffle furnace at 550° C. for 10 hours to remove the templating agent, so as to obtain a product which is measured by XRD to have a phase pertaining to mordenite.

(76) The mordenite has a relative crystallinity of 95% and a silicon-to-aluminum ratio of 14, and the XRD pattern thereof is shown in FIG. 11.

Example 11

(77) This example provides a method for preparing a mordenite, wherein the processes for activating diatomaceous earth and rectorite, and the process for preparing the sulfuric acid solution are the same as those in Example 1. The process for activating kaolin and the process for preparing the TEABr solution are the same as those in Example 8.

(78) The method for preparing a mordenite is carried out according to steps as below:

(79) weighing, separately, 5.0 g of the diatomaceous earth powders activated by thermal treatment, 0.65 g of the rectorite powders activated by sub-molten salt activation method, 0.5 g of the kaolin powders activated by sub-molten salt activation method, 1.2 g of solid sodium hydroxide, and the TEABr solution, adding them to 50 g of deionized water and adjusting the pH by the sulfuric acid solution to have a pH of 12.5 to obtain a reaction mixture having a composition by mole of 23 SiO.sub.2:Al.sub.2O.sub.3: 6.2Na.sub.2O:4.1TEABr:1000H.sub.2O;

(80) aging the reaction mixture at 70° C. for 24 hours before transferring it to a stainless-steel kettle for crystallization with a polytetrafluoroethylene liner, subjecting it to a pre-crystallization at 110° C. for 24 hours and then a static crystallization at 170° C. for 48 hours;

(81) upon the completion of crystallization, cooling and filtering the reaction product to remove mother liquor, washing it to have a neutral pH, drying it at 120° C. for 24 hours and then calcinating the resultant as obtained in a muffle furnace at 550° C. for 10 hours to remove the templating agent, so as to obtain a product which is measured by XRD to have a phase pertaining to mordenite.

(82) The mordenite has a relative crystallinity of 98% and a silicon-to-aluminum ratio of 20, and the XRD pattern thereof is shown in FIG. 12.