PREPARATION METHOD FOR BETA ZEOLITE

Abstract

The present invention provides a preparation method of Beta molecular sieve, comprising: activating a mineral having low silica-to-alumina ratio and a mineral having high silica-to-alumina ratio, respectively, wherein the mineral having low silica-to-alumina ratio is activated via a sub-molten salt medium, and the mineral having high silica-to-alumina ratio is activated via means of high-temperature calcination; mixing the activated minerals with sodium chloride, potassium chloride, water and template agent for hydrothermal crystallization, wherein the charged amounts of the raw materials satisfies a molar ratio of: 0.03-0.18 Na.sub.2O:0.01-0.03 K.sub.2O:0.1-0.4 (TEA).sub.2O:1 SiO.sub.2:0.01-0.5 Al.sub.2O.sub.3:12-40 H.sub.2O; cooling the crystallized product and removing the mother liquor by filtration, washing the resulting filter cake with water to neutral and drying it to obtain the Beta molecular sieve. The method of the present invention broadens the range of raw materials for synthesizing the molecular sieve, greatly reduce the production cost, and significantly improve the environmental friendliness of the synthesis process, thereby having a wide range of application prospects.

Claims

1. A preparation method of Beta molecular sieve, characterized in that, the method comprises the following steps: (1) activation of minerals: activating a mineral having a low silica-to-alumina ratio and a mineral having a high silica-to-alumina ratio, respectively, wherein the mineral having a low silica-to-alumina ratio is activated via a sub-molten salt medium, and the mineral having a high silica-to-alumina ratio is subjected to thermal activation treatment by means of high-temperature calcination; (2) crystallization: mixing the mineral having a low silica-to-alumina ratio and the mineral having a high silica-to-alumina ratio, which have been activated in Step (1), with sodium chloride, potassium chloride, water and a template agent for hydrothermal crystallization, and controlling charged amounts of the respective raw materials such that the molar ratio satisfies: 0.03-0.18 Na.sub.2O:0.01-0.03 K.sub.2O:0.1-0.4 (TEA).sub.2O:1 SiO.sub.2:0.01-0.5 Al.sub.2O.sub.3:12-40 H.sub.2O; cooling the crystallized product, removing the mother liquor by filtration, washing the resulting filter cake with water to neutral and drying it to obtain the Beta molecular sieve.

2. The preparation method according to claim 1, wherein the mineral having a low silica-to-alumina ratio has a silica-to-alumina molar ratio of 10 or less, and the mineral having a high silica-to-alumina ratio has a silica-to-alumina molar ratio of 30 or more.

3. The preparation method according to claim 1, wherein the mineral having a low silica-to-alumina ratio is kaolin and/or rectorite; and the mineral having a high silica-to-alumina ratio is diatomite and/or white carbon black.

4. The preparation method according to claim 1, wherein the activation of the mineral having a low silica-to-alumina ratio with a sub-molten salt medium in Step (1) comprises mixing uniformly the mineral having a low silica-to-alumina ratio with an alkali metal hydroxide and water prior to drying.

5. The preparation method according to claim 4, wherein the alkali metal hydroxide is sodium hydroxide, the mass ratio of the mineral having a low silica-to-alumina ratio to the total weight of sodium hydroxide and water is 1:1-10, the mass ratio of sodium hydroxide to water is from 2:1 to 1:5, and the drying temperature is from 100 C. to 400 C.

6. The preparation method according to claim 1, wherein, in Step (1), the mineral having a high silica-to-alumina ratio has a calcination temperature of 600 C. to 1000 C., and a calcination time of 1 to 10 hours.

7. The preparation method according to claim 1, wherein, in Step (2), the template agent is tetraethylammonium hydroxide, tetraethylammonium bromide or a combination thereof.

8. The preparation method according to claim 1, wherein, in Step (2), the crystallization is carried out at 130 C. to 160 C. for 24 to 72 hours.

9. Beta molecular sieve produced by the method according to claim 1.

10. The Beta molecular sieve according to claim 9, having a silica-to-alumina molar ratio of 2.0 to 78.0, a relative crystallinity of 70 to 100%, and a grain size of 100 to 600 nm.

11. The Beta molecular sieve according to claim 9, wherein the mineral having a low silica-to-alumina ratio has a silica-to-alumina molar ratio of 10 or less, and the mineral having a high silica-to-alumina ratio has a silica-to-alumina molar ratio of 30 or more.

12. The Beta molecular sieve according to claim 9, wherein the mineral having a low silica-to-alumina ratio is kaolin and/or rectorite; and wherein the mineral having a high silica-to-alumina ratio is diatomite and/or white carbon black.

13. The Beta molecular sieve according to claim 9, wherein the activation of the mineral having a low silica-to-alumina ratio with a sub-molten salt medium in Step (1) comprises mixing uniformly the mineral having a low silica-to-alumina ratio with an alkali metal hydroxide and water prior to drying.

14. The Beta molecular sieve according to claim 12, wherein the alkali metal hydroxide is sodium hydroxide, the mass ratio of the mineral having a low silica-to-alumina ratio to the total weight of sodium hydroxide and water is 1:1-10, the mass ratio of sodium hydroxide to water is from 2:1 to 1:5, and the drying temperature is from 100 C. to 400 C.

15. The Beta molecular sieve according to claim 9, wherein, in Step (1), the mineral having a high silica-to-alumina ratio has a calcination temperature of 600 C. to 1000 C., and a calcination time of 1 to 10 hours.

16. The Beta molecular sieve according to claim 9, wherein, in Step (2), the template agent is tetraethylammonium hydroxide, tetraethylammonium bromide or a combination thereof.

17. The Beta molecular sieve according to claim 9, wherein, in Step (2), the crystallization is carried out at 130 C. to 160 C. for 24 to 72 hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is an XRD spectrum of the Beta molecular sieve obtained in Example 1 of the present invention.

[0028] FIG. 2 is a scanning electron microscope (SEM) image magnified by 100,000 times of the Beta molecular sieve obtained in Example 1 of the present invention.

[0029] FIG. 3 is an XRD spectrum of the Beta molecular sieve obtained in Example 2 of the present invention.

[0030] FIG. 4 is a scanning electron microscope (SEM) image magnified by 100,000 times of the Beta molecular sieve obtained in Example 2 of the present invention.

[0031] FIG. 5 is an XRD spectrum of the Beta molecular sieve obtained in Example 3 of the present invention.

[0032] FIG. 6 is a scanning electron microscope (SEM) image magnified by 100,000 times of the Beta molecular sieve obtained in Example 3 of the present invention.

[0033] FIG. 7 is an XRD spectrum of the Beta molecular sieve obtained in Example 4 of the present invention.

[0034] FIG. 8 is a scanning electron microscope (SEM) image magnified by 100,000 times of the Beta molecular sieve obtained in Example 4 of the present invention.

[0035] FIG. 9 is an XRD spectrum of the Beta molecular sieve obtained in Example 5 of the present invention.

[0036] FIG. 10 is a scanning electron microscope (SEM) image magnified by 100,000 times of the Beta molecular sieve obtained in Example 5 of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0037] The present invention will now be described, by way of example, with reference to the following detailed description of the embodiments and the beneficial effects of the present invention, which are intended to assist the reader in a better understanding of the spirit and features of the invention and are not to be construed as limiting the scope of the invention.

[0038] The relative crystallinity described in the examples is the ratio of the characteristic peak areas of the 2 angle at 21.5 in the XRD spectrum between the resulting product and the molecular sieve standard sample according to ASTM D 3906-03, expressed as a percentage. The standard sample is a Beta molecular sieve (manufactured by Nankai University Catalyst Factory, which has a silica-to-alumina molar ratio of 40) synthesized by using conventional chemical reagents as raw materials, and its crystallinity is defined as 100%.

[0039] The silica-to-alumina ratio of the product was characterized by an X-ray fluorescence (XRF) method using Rigaku ZSX-100e4580 Type X-ray fluorescence spectrometer. The silica-to-alumina ratio of the molecular sieve described in the present invention refers to the molar ratio of SiO.sub.2 to Al.sub.2O.sub.3.

[0040] Selection of minerals in Examples: The diatomite, kaolin and rectorite used are commercially available. The main components of diatomite are: SiO.sub.2 with a content of 96.2 wt. %, and Al.sub.2O.sub.3 with a content of 2.13 wt. %; the main components of rectorite are: SiO.sub.2 with a content of 43.2 wt. %, and Al.sub.2O.sub.3 with a content of 37.2 wt. %; the main components of kaolin are: SiO.sub.2 with a content of 50.5 wt. %, and Al.sub.2O.sub.3 with a content of 44.6 wt. %.

EXAMPLE 1

[0041] Activation of minerals: 50.00 g of a diatomite powder was weighed and calcined at 800 C. for 4 h for use. 12.00 g of a rectorite powder was weighed and mixed homogeneously with 18.00 g of solid sodium hydroxide, and 90.00 g of deionized water was added, then dried at 250 C. for use.

[0042] Preparation of the molecular sieve: 9.00 g of the calcined diatomite powder was weighed, and 43.00 g of tetraethylammonium hydroxide (mass fraction of 25%, the same below), 7.70 g of deionized water, 0.03 g of sodium chloride, 0.43 g of potassium chloride, and 0.73 g of the activated rectorite powder were added, such that the molar ratio satisfies: 0.04 Na.sub.2O:0.02 K.sub.2O:0.25 (TEA).sub.2O:1 SiO.sub.2:0.02 Al.sub.2O.sub.3:15 H.sub.2O. After mixing uniformly, this mixture was poured into a Teflon-lined stainless steel crystallization vessel, heated to 140 C., and left to crystallization for 72 h. After the completion of crystallization, the mixture was cooled and the mother liquor was removed by filtration, and the resultant was washed to neutral, and dried at 120 C., to obtain a crystallized product. The physical phase of the product was identified by XRD characterization as a Beta molecular sieve. In the product, the Beta molecular sieve had a relative crystallinity of 99%, a grain size of 400 to 600 nm, a silica-to-alumina ratio of 48.0, an XRD spectrum as shown in FIG. 1, and a SEM image as shown in FIG. 2.

EXAMPLE 2

[0043] Activation of minerals: 50.00 g of a diatomite powder was weighed and calcined at 600 C. for 8 h for use. 12.00 g of a rectorite powder was weighed and mixed homogeneously with 24.00 g of solid sodium hydroxide, and 60.00 g of deionized water was added, then dried at 200 C. for use.

[0044] Preparation of the molecular sieve: 9.00 g of the calcined diatomite powder was weighed, and 60.20 g of tetraethylammonium hydroxide, 48.21 g of deionized water, 0.03 g of sodium chloride, 0.65 g of potassium chloride, and 0.86 g of the activated rectorite powder were added, such that the molar ratio satisfies: 0.05 Na.sub.2O:0.03 K.sub.2O:0.35 (TEA).sub.2O:1 SiO.sub.2:0.02 Al.sub.2O.sub.3:35 H.sub.2O. After mixing uniformly, this mixture was poured into a Teflon-lined stainless steel crystallization vessel, heated to 150 C., and left to crystallization for 24 h. After the completion of crystallization, the mixture was cooled and the mother liquor was removed by filtration, and the resultant was washed to neutral, and dried at 120 C., to obtain a crystallized product. The physical phase of the product was identified by XRD characterization as a Beta molecular sieve. In the product, the Beta molecular sieve had a relative crystallinity of 90%, a grain size of 200 to 600 nm, a silica-to-alumina ratio of 47.5, a XRD spectrum as shown in FIG. 3, and a SEM image as shown in FIG. 4.

EXAMPLE 3

[0045] Activation of minerals: 50.00 g of a diatomite powder was weighed and calcined at 950 C. for 2 h for use. 12.00 g of a rectorite powder was weighed and mixed homogeneously with 12.00 g of solid sodium hydroxide, and 6.00 g of deionized water was added, then dried at 350 C. for use.

[0046] Preparation of the molecular sieve: 9.00 g of the calcined diatomite powder was weighted, and 25.80 g of tetraethylammonium hydroxide, 44.65 g of deionized water, 0.60 g of sodium chloride, 0.33 g of potassium chloride, and 0.57 g of the activated rectorite powder were added, such that the molar ratio satisfies: 0.06 Na.sub.2O:0.015 K.sub.2O:0.15 (TEA).sub.2O:1 SiO.sub.2:0.02 Al.sub.2O.sub.3:24 H.sub.2O. After mixing uniformly, this mixture was poured into a Teflon-lined stainless steel crystallization vessel, heated to 130 C., and left to crystallization for 60 h. After the completion of crystallization, the mixture was cooled and the mother liquor was removed by filtration, and the resultant was washed to neutral, and dried at 120 C., to obtain a crystallized product. As measured by XRD, the physical phase of the product belongs to Beta molecular sieve. In the product, the Beta molecular sieve had a relative crystallinity of 85%, a grain size of 300 to 600 nm, a silica-to-alumina ratio of 48.5, an XRD spectrum as shown in FIG. 5, and a SEM image as shown in FIG. 6.

EXAMPLE 4

[0047] Activation of minerals: 50.00 g of a diatomite powder was weighed and calcined at 950 C. for 2 h for use. 12.00 g of a kaolin powder was weighed and mixed homogeneously with 18.00 g of solid sodium hydroxide, and 42.00 g of deionized water was added, then dried at 300 C. for use.

[0048] Preparation of the molecular sieve: 9.00 g of the calcined diatomite powder was weighed, and 43.76 g of tetraethylammonium hydroxide, 20.64 g of deionized water, 0.12 g of sodium chloride, 0.33 g of potassium chloride, and 1.25 g of the activated kaolin powder were added, such that the molar ratio satisfies: 0.07 Na.sub.2O:0.015 K.sub.2O:0.25 (TEA).sub.2O:1 SiO.sub.2:0.027 Al.sub.2O.sub.3:20 H.sub.2O. After mixing uniformly, this mixture was poured into a Teflon-lined stainless steel crystallization vessel, heated to 140 C., and left to crystallization for 48 h. After the completion of crystallization, the mixture was cooled and the mother liquor was removed by filtration, and the resultant was washed to neutral, and dried at 120 C., to obtain a crystallized product. The physical phase of the product was identified by XRD characterization as a Beta molecular sieve. In the product, the Beta molecular sieve had a relative crystallinity of 75%, a grain size of 100 to 500 nm, a silica-to-alumina ratio of 35, an XRD spectrum as shown in FIG. 7, and a SEM image as shown in FIG. 8.

EXAMPLE 5

[0049] Activation of minerals: 50.00 g of a diatomite powder was weighed and calcined at 800 C. for 6 h for use. 12.00 g of a kaolin powder was weighed and mixed homogeneously with 18.00 g of solid sodium hydroxide, and 54.00 g of deionized water was added, then dried at 300 C. for use.

[0050] Preparation of the molecular sieve: 8.59 g of the calcined diatomite powder was weighed, and 43.76 g of tetraethylammonium hydroxide, 20.64 g of deionized water, 0.33 g of potassium chloride, and 3.22 g of the activated kaolin powder were added, such that the molar ratio satisfies: 0.16 Na.sub.2O:0.015 K.sub.2O:0.25 (TEA).sub.2O:1 SiO.sub.2:0.05 Al.sub.2O.sub.3:20 H.sub.2O. After mixing uniformly, this mixture was poured into a Teflon-lined stainless steel crystallization vessel, heated to 140 C., and left to crystallization for 72 h. After the completion of crystallization, the mixture was cooled and the mother liquor was removed by filtration, and the resultant was washed to neutral, and dried at 120 C., to obtain a crystallized product. The physical phase of the product was identified by XRD characterization as a Beta molecular sieve. In the product, the Beta molecular sieve had a relative crystallinity of 78%, a grain size of 300 to 500 nm, a silica-to-alumina ratio of 19.0, an XRD spectrum as shown in FIG. 9, and a SEM image as shown in FIG. 10.