Neutral Polymer-Oriented Hierarchical Pore Beta Molecular Sieve and Environment-Friendly Preparation Method Thereof

Abstract

The present invention relates to the technical field of molecular sieves, in particular to a neutral polymer-oriented hierarchical pore Beta molecular sieve and an environment-friendly preparation method thereof. The environment-friendly preparation method of the neutral polymer-oriented hierarchical pore Beta molecular sieve includes the following steps: preparing a sample by a hydrothermal method with nitrogen-free polyketal as a template agent; and conducting acid treatment on the obtained sample to remove the template agent and to obtain the hierarchical pore Beta molecular sieve. The hierarchical pore Beta molecular sieve is a nano-mesoporous molecular sieve, a mesopore diameter thereof is concentrated at 10 to 20 nm, a crystal grain size thereof is 30 to 120 nm, a specific surface area thereof is 700 to 820 m.sup.2/g, and a pore volume thereof is 0.75 to 0.92 cm.sup.3/g. The present application can solve the problems such as collapse of a molecular sieve structure caused by high-temperature roasting, emission of harmful gases and non-recyclability of the template agent. Moreover, the prepared Beta molecular sieve is a hierarchical pore molecular sieve, and has the advantages of nano-single crystal structure, high specific surface area, high pore volume and the like.

Claims

1. An environment-friendly preparation method of a neutral polymer-oriented hierarchical pore Beta molecular sieve, comprising the following steps: A. preparing a sample by a hydrothermal method with nitrogen-free polyketal as a template agent; and B. conducting acid treatment on the obtained sample to remove the template agent and to obtain the hierarchical pore Beta molecular sieve.

2. The environment-friendly preparation method of the neutral polymer-oriented hierarchical pore Beta molecular sieve according to claim 1, wherein a terminal position of the template agent has a hydroxyl group.

3. The environment-friendly preparation method of the neutral polymer-oriented hierarchical pore Beta molecular sieve according to claim 2, wherein a structural formula of the template agent is as follows: ##STR00003##

4. The environment-friendly preparation method of the neutral polymer-oriented hierarchical pore Beta molecular sieve according to claim 1, wherein an acid treatment agent used for the acid treatment comprises hydrochloric acid.

5. The environment-friendly preparation method of the neutral polymer-oriented hierarchical pore Beta molecular sieve according to claim 1, wherein a temperature of the acid treatment is 80° C. to 100° C., and acid treatment time is 5 to 7 hours.

6. The environment-friendly preparation method of the neutral polymer-oriented hierarchical pore Beta molecular sieve according to claim 1, wherein Step A comprises the following steps: a. mixing water, an aluminum source and the template agent evenly, and then adding a silicon source in batches to obtain a gel; b. aging the gel for 5 to 12 hours at 20° C. to 30° C. and then placing the gel in a reaction kettle to be crystallized for 3 to 10 days at 180° C. to 200° C.; c. after crystallization is completed, filtering and drying an obtained solid product to obtain a sample.

7. The environment-friendly preparation method of the neutral polymer-oriented hierarchical pore Beta molecular sieve according to claim 6, wherein the gel comprises, in parts by molar, 1 part of SiO.sub.2, 0.01 to 0.05 part of Al.sub.2O.sub.3, 0.08 to 0.22 part of Na.sub.2O, 35 to 50 parts of H.sub.2O, and 0.1 to 0.3 part of the template agent.

8. The environment-friendly preparation method of the neutral polymer-oriented hierarchical pore Beta molecular sieve according to claim 6, wherein the aluminum source comprises one or more of sodium metaaluminate, aluminum sulfate, kaolin, and rectorite.

9. The environment-friendly preparation method of the neutral polymer-oriented hierarchical pore Beta molecular sieve according to claim 6, wherein the silicon source comprises one or more of silica sol, tetraethoxysilane, white carbon black, and diatomite.

10. A hierarchical pore Beta molecular sieve prepared by adopting the environment-friendly preparation method of the neutral polymer-oriented hierarchical pore Beta molecular sieve of claim 1, wherein the hierarchical pore Beta molecular sieve is a nano-mesoporous molecular sieve, a mesopore diameter thereof is concentrated at 10 to 20 nm, a crystal grain size thereof is 30 to 120 nm, a specific surface area thereof is 700 to 820 m.sup.2/g, and a pore volume thereof is 0.75 to 0.92 cm.sup.3/g.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0026] FIG. 1 is an XRD diffractogram of a hierarchical pore Beta molecular sieve prepared in Example 1;

[0027] FIG. 2 shows N.sub.2 adsorption and desorption curves of the hierarchical pore Beta molecular sieve prepared in Example 1; and

[0028] FIG. 3 is a pore diameter distribution diagram of the hierarchical pore Beta molecular sieve prepared in Example 1.

DETAILED DESCRIPTION OF EMBODIMENTS

[0029] The followings are specific embodiments of the present invention, and in conjunction with the accompanying drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these examples.

[0030] An environment-friendly preparation method of a hierarchical pore Beta molecular sieve included the following steps.

[0031] A. A sample was prepared by a hydrothermal method with nitrogen-free polyketal as a template agent.

##STR00002##

was selected as the template agent.

[0032] 0.08 g of NaAlO.sub.2 and 0.3 g of NaOH were dissolved in 12.1 mL of water to form a clear solution, and then 0.84 g of the above template agent was added into the clear solution. After even stirring, 0.93 g of white carbon black was added. A feeding molar ratio met: 1 (SiO.sub.2):0.02 (Al.sub.2O.sub.3):0.22 (Na.sub.2O):50 (H.sub.2O):0.2 (template agent). After aging for 8 hours at 25° C., a gel was transferred into a stainless steel reaction kettle with a polytetrafluoroethylene lining and placed in a 180° C. homogeneous reactor to be crystallized for 144 hours. A product was centrifuged, washed and then dried at 100° C. to obtain a solid sample.

[0033] B. Acid treatment was conducted on the obtained sample to remove the template agent and to obtain the hierarchical pore Beta molecular sieve.

[0034] 0.2 g of the above solid sample was weighed to be added into 25 mL of hydrochloric acid with a concentration of 1 mol/L. Stirring was conducted for 12 hours at 80° C. An obtained product was centrifuged, fully washed with deionized water until neutral, and finally dried in a 110° C. oven to obtain a product with a crystal grain size of about 65 nm.

[0035] An XRD diffractogram of the product was shown in FIG. 1, and a phase of the obtained product is determined by XRD to belong to a Beta molecular sieve, and a relative crystallinity thereof was 98%.

[0036] As shown in FIG. 2 and FIG. 3, the product was a hierarchical pore molecular sieve with mesopores, a mesopore diameter thereof was concentrated at 20 nm, a specific surface area thereof was 721 m.sup.2/g, and a pore volume thereof was 0.72 cm.sup.3/g.

EXAMPLE 2

[0037] An environment-friendly preparation method of a hierarchical pore Beta molecular sieve included the following steps.

[0038] A. A sample was prepared by a hydrothermal method with nitrogen-free polyketal as a template agent.

[0039] The template agent in Example 1 was used as a template agent, sodium metaaluminate and aluminum sulfate were used as an aluminum source, and tetraethoxysilane was used as a silicon source. After the aluminum source and sodium hydroxide were dissolved in water to form a clear solution, the template agent was added into the clear solution. After even stirring, the silicon source was added. The amount of addition was adjusted to make a feeding molar ratio meet: 1 (SiO.sub.2):0.03 (Al.sub.2O.sub.3):0.22 (Na.sub.2O):50 (H.sub.2O):0.2 (template agent). After aging for 8 hours at 25° C., a gel was transferred into a stainless steel reaction kettle with a polytetrafluoroethylene lining and placed in a 190° C. homogeneous reactor to be crystallized for 48 hours. A product was centrifuged, washed and then dried at 100° C. to obtain a solid sample.

[0040] B. Acid treatment was conducted on the obtained sample to remove the template agent and to obtain the hierarchical pore Beta molecular sieve.

[0041] 0.2 g of the above solid sample was weighed to be added into 25 mL of hydrochloric acid with a concentration of 1 mol/L. Stirring was conducted for 12 hours at 80° C. An obtained product was centrifuged, fully washed with deionized water until neutral, and finally dried in a 110° C. oven to obtain a product.

[0042] A phase of the product is determined by XRD to belong to a Beta molecular sieve, and a relative crystallinity thereof was 96%, a crystal grain size thereof was about 25 nm, a mesopore diameter thereof was concentrated at 10 nm, a specific surface area thereof was 750 m.sup.2/g, and a pore volume thereof was 0.81 cm.sup.3/g.

EXAMPLE 3

[0043] An environment-friendly preparation method of a hierarchical pore Beta molecular sieve included the following steps.

[0044] A. A sample was prepared by a hydrothermal method with nitrogen-free polyketal as a template agent.

[0045] The template agent in Example 1 was used as a template agent, aluminum sulfate was used as an aluminum source, and silica sol and white carbon black were used as a silicon source. After the aluminum source and sodium hydroxide were dissolved in water to form a clear solution, the template agent was added into the clear solution. After even stirring, the silicon source was added. The amount of addition was adjusted to make a feeding molar ratio meet: 1 (SiO.sub.2):0.05 (Al.sub.2O.sub.3):0.08 (Na.sub.2O):35 (H.sub.2O):0.2 (template agent). After aging for 8 hours at 25° C., a gel was transferred into a stainless steel reaction kettle with a polytetrafluoroethylene lining and placed in a 180° C. homogeneous reactor to be crystallized for 240 hours. A product was centrifuged, washed and then dried at 100° C. to obtain a solid sample.

[0046] B. Acid treatment was conducted on the obtained sample to remove the template agent and to obtain the hierarchical pore Beta molecular sieve.

[0047] 0.2 g of the above solid sample was weighed to be added into 25 mL of hydrochloric acid with a concentration of 1 mol/L. Stirring was conducted for 12 hours at 80° C. An obtained product was centrifuged, fully washed with deionized water until neutral, and finally dried in a 110° C. oven to obtain a product.

[0048] A phase of the product is determined by XRD to belong to a Beta molecular sieve, and a relative crystallinity thereof was 92%, a crystal grain size thereof was about 18 nm, a mesopore diameter thereof was concentrated at 12 nm, a specific surface area thereof was 710 m.sup.2/g, and a pore volume thereof was 0.71 cm.sup.3/g.

EXAMPLE 4

[0049] An environment-friendly preparation method of a hierarchical pore Beta molecular sieve included the following steps.

[0050] A. A sample was prepared by a hydrothermal method with nitrogen-free polyketal as a template agent.

[0051] The template agent in Example 1 was used as a template agent, commercially available kaolin was used as an aluminum source, and commercially available silicon source was used as a silicon source. In particular, the kaolin was mainly composed of 53.14 wt. % of SiO.sub.2 and 44.11 wt. % of Al.sub.2O.sub.3. Before use, the kaolin needs to be pretreated as follows: 12.00 g of the kaolin was weighed, 16.00 g of sodium hydroxide was added to be mixed evenly, 64.00 g of deionized water was added, and drying was conducted at 200° C. for standby application. The diatomite was mainly composed of 95.35 wt. % of SiO.sub.2 and 2.67 wt. % of Al.sub.2O.sub.3. Before use, the diatomite also needs to be pretreated as follows: 20.00 g of the diatomite was weighed, and roasted for 4 hours at 600° C. for standby application.

[0052] After the aluminum source and sodium hydroxide were dissolved in water to form a clear solution, the template agent was added into the clear solution. After even stirring, the silicon source was added. The amount of addition was adjusted to make a feeding molar ratio meet: 1 (SiO.sub.2):0.02 (Al.sub.2O.sub.3):0.22 (Na.sub.2O):50 (H.sub.2O):0.2 (template agent). After aging for 8 hours at 25° C., a gel was transferred into a stainless steel reaction kettle with a polytetrafluoroethylene lining and placed in a 180° C. homogeneous reactor to be crystallized for 144 hours. A product was centrifuged, washed and then dried at 100° C. to obtain a solid sample.

[0053] B. Acid treatment was conducted on the obtained sample to remove the template agent and to obtain the hierarchical pore Beta molecular sieve.

[0054] 0.2 g of the above solid sample was weighed to be added into 25 mL of hydrochloric acid with a concentration of 1 mol/L. Stirring was conducted for 12 hours at 80° C. An obtained product was centrifuged, fully washed with deionized water until neutral, and finally dried in a 110° C. oven to obtain a product.

[0055] A phase of the product is determined by XRD to belong to a Beta molecular sieve, and a relative crystallinity thereof was 96%, a crystal grain size thereof was about 80 nm, a mesopore diameter thereof was concentrated at 20 nm, a specific surface area thereof was 700 m.sup.2/g, and a pore volume thereof was 0.60 cm.sup.3/g.

COMPARATIVE EXAMPLE 1

[0056] This comparative example was basically the same as Example 1, and the difference only lied in that: no template agent was added in this comparative example.

[0057] A phase of a product prepared in this comparative example was determined by XRD to belong to a ZSM-5 molecular sieve.

COMPARATIVE EXAMPLE 2

[0058] This comparative example was basically the same as Example 2, and the difference only lied in that: no template agent was added in this comparative example.

[0059] A phase of a product prepared in this comparative example was determined by XRD to belong to a ZSM-5 molecular sieve.

COMPARATIVE EXAMPLE 3

[0060] This comparative example was basically the same as Example 3, and the difference only lied in that: no template agent was added in this comparative example.

[0061] A phase of a product prepared in this comparative example was determined by XRD to be amorphous.

COMPARATIVE EXAMPLE 4

[0062] This comparative example was basically the same as Example 4, and the difference only lied in that: no template agent was added in this comparative example.

[0063] A phase of a product prepared in this comparative example was determined by XRD to be amorphous.

[0064] From the examples and the comparative examples, it can be seen that by using nitrogen-free polyketal as a template agent, a hierarchical pore Beta molecular sieve with a high specific surface area and a high pore volume can be synthesized.

[0065] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various amendments or additions to the described specific embodiments or substitute them in similar manners, but it will not deviate from the spirit of the present invention or go beyond the scope defined by the appended claims.