Olefin epoxidized rice hull catalyst and preparation method thereof
The olefin epoxidation catalyst prepared by pre-carbonization, acidic and alkaline treatment of rice husks solves the problems of existing catalyst separation and high cost, and achieves a highly selective and economical epoxidation reaction, replacing titanium silicon Application of molecular sieve.
Patent Information
- Application Number
- CN202411489964.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-24
- Publication Date
- 2024-12-27
AI Technical Summary
The existing olefin epoxidation catalysts have problems such as difficulty in separation of catalysts and product recycling, and the high cost and low efficiency of titanium silicon molecular sieves limit their industrial development.
The olefin epoxidation rice husk catalyst is prepared by pre-carbonization, acidic and alkaline treatment and complexing agent treatment, forming a catalyst with the main components of carbon and silica, which is used to replace titanium silicon molecular sieve for ringing. Oxidation reaction.
The high selectivity and economic efficiency of the catalyst are achieved, and the epoxidation of olefins can be effectively catalyzed to form high value-added epoxy compounds. For example, the selectivity of epoxycyclohexane can reach 96.5%, and the catalyst preparation process is simplified.
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of olefin epoxidation reaction, and particularly relates to an olefin epoxidation rice husk catalyst and a preparation method thereof. Background Art
[0002] Epoxides are important chemical synthesis intermediates used in the production of fine chemicals, food additives, pharmaceutical intermediates and other essential products. The high reactivity of epoxy compounds, coupled with the charge polarization effect and intra-ring strain of the epoxy group, makes them prone to ring-opening reactions. This reactivity enables them to be converted into a variety of valuable chemical products such as surfactants, polymers and glycols. At present, the global production of epichlorohydrin alone has reached 10 million tons, which is widely used in the manufacture of chemicals such as polyurethane and propylene glycol. Another important epoxy compound is oxirane, which can be used to synthesize various organic intermediates through ring-opening reactions and has a wide range of applications in the fields of pharmaceuticals, pesticides and surfactants. The efficient and selective synthesis of epoxy compounds has always been an important topic in academia and industrial applications. The epoxidation reaction of olefins is the main method for producing epoxy compounds. With the advancement of industrial processes and the growth of demand for high-end chemicals, the demand for epoxides has continued to rise, driving the continuous development of related basic research and application technologies.
[0003] In the catalytic epoxidation of olefins, catalysts can generally be divided into two categories: homogeneous catalysts and heterogeneous catalysts. Among them, homogeneous catalysts are generally metal organic complexes, polyoxometalates, etc. Homogeneous catalysts usually have high catalytic activity and selectivity, but there are problems such as difficulty in separating catalysts from products and difficulty in recycling. Heterogeneous catalysts mainly include various supported transition metal complex catalysts, metal organic framework materials (MOF), composite metal oxides, heteroatom molecular sieves, etc. Among them, heteroatom molecular sieve catalysts represented by titanium silicalite (TS-1) have been successfully used in various types of selective catalytic oxidation reaction processes including propylene epoxidation, and have achieved large-scale industrialization. However, TS-1 molecular sieves usually use expensive tetrapropylammonium hydroxide as a template, which not only increases the synthesis cost, but also limits its industrial development. In addition, the TS-1 molecular sieve synthesized by the cheap system has problems such as large grain size and low skeleton titanium content, which further affects its catalytic performance. Therefore, selecting cheaper and more readily available catalysts for olefin epoxidation is the focus and difficulty of current research.
[0004] To solve the above problems, this invention proposes a rice husk catalyst for olefin epoxidation, and its preparation method and application. Rice husk is a by-product of the rice milling process and the main agricultural waste in the rice production process. It is cheap and easy to obtain. At the same time, the catalyst can be used to catalyze olefin epoxidation to obtain epoxy compounds with high added value. Summary of the invention
[0005] The present invention provides a rice husk catalyst for olefin epoxidation and a preparation method thereof, and the catalyst is used to catalyze the olefin epoxidation process to obtain a high value-added epoxide compound. The steps for preparing the rice husk catalyst for olefin epoxidation are as follows:
[0006] (1) Pre-carbonizing the rice husk catalyst under nitrogen conditions at a suitable temperature to obtain pre-carbonized rice husk; metal impurities in the unpre-carbonized rice husk exist in the form of organic matter and cannot be removed by an acid solution or a complexing agent solution;
[0007] (2) mixing the pre-carbonized rice husk obtained in step (1) with an acidic solution, heating and refluxing the mixture, filtering and washing the mixture, mixing the mixture with a complexing agent solution, heating and refluxing the mixture, filtering, washing, and vacuum drying the mixture to obtain pre-treated rice husk; treating the pre-carbonized rice husk with an acidic solution and a complexing agent solution to remove impurities such as metals in the rice husk.
[0008] (3) The pretreated rice husks obtained in step (2) are mixed with an alkaline solution, heated to reflux for reaction, and then filtered, washed, and vacuum dried. Under nitrogen conditions, the rice husks are carbonized again at a suitable temperature to obtain an olefin epoxidation rice husk catalyst.
[0009] Preferably, in step (1), the pre-carbonization temperature is 200-400° C., such as 200, 300, or 400° C.; and the pre-carbonization time is 6-12 h.
[0010] Preferably, in step (2), the ratio of the pre-carbonized rice husk to the acidic solution is 1 g: 10-100 mL.
[0011] Preferably, in step (2), the concentration of the acidic solution is 1-5wt%; the acidic solution is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, oxalic acid, and citric acid.
[0012] Preferably, in step (2), the ratio of the pre-carbonized rice husk to the complexing agent solution is 1 g: 10-100 mL.
[0013] Preferably, in step (2), the concentration of the complexing agent solution is 0.1-1wt.%, preferably one or more of ethylenediaminetetraacetic acid, aminotriacetic acid, citric acid, and tartaric acid;
[0014] Preferably, in step (2), the heating reflux reaction is carried out at a temperature of 40-120° C., such as 40, 60, 80, 100, 120° C., and the reflux time is 6-24 h;
[0015] Preferably, in step (3), the ratio of the pretreated rice husk to the alkaline solution is 1 g: 10-50 mL.
[0016] Preferably, in step (3), the alkaline solution is preferably one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and potassium carbonate.
[0017] Preferably, in step (3), the concentration of the alkaline solution is preferably 0.01-0.5 mol / L, for example 0.01, 0.02, 0.05, 0.1, 0.2, 0.5 mol / L.
[0018] Preferably, in step (3), the heating reflux reaction is carried out at a temperature of 40-120°C, such as 40, 60, 80, 100, 120°C, and the reflux time is 6-24h.
[0019] Preferably, in step (3), the carbonization temperature is 400-800° C., such as 400, 500, 600, 700, 800° C.; and the carbonization time is 1-4 h.
[0020] The application of the rice husk catalyst prepared by the above method in olefin epoxidation comprises the following steps:
[0021] Cyclohexene, olefin epoxidation rice husk catalyst, hydrogen peroxide solution and acetonitrile solution are added into a reaction kettle and reacted under heating and stirring.
[0022] Preferably, the dosage ratio of the cyclohexene, olefin epoxidation rice husk catalyst, hydrogen peroxide solution and acetonitrile solution is: 4.1g:1g:12g-24g:10mL.
[0023] Preferably, the heating and stirring temperature is 70°C.
[0024] Beneficial effects of the present invention:
[0025] (1) The present invention uses rice husk as raw material, and prepares an olefin epoxidation rice husk catalyst by pre-carbonization, acid treatment, complexing agent solution treatment, alkali treatment, and carbonization. The catalyst is mainly composed of carbon and silicon dioxide. The catalyst preparation process is simple, the raw material source is wide and cheap, and it is easy to synthesize on an industrial scale. It can replace titanium silicon molecular sieves for epoxidation processes, and the economic efficiency is very significant.
[0026] (2) The present invention improves the selectivity of olefin epoxidation reaction using rice husk catalyst by optimizing the preparation method of rice husk catalyst, and can be used for selective epoxidation of olefins to produce high value-added epoxidation chemicals. For example, in an embodiment of the present invention, the selectivity of cyclohexene oxide can reach 96.5% by using the rice husk catalyst prepared by the present invention to catalyze the epoxidation of cyclohexene. DETAILED DESCRIPTION
[0027] The present invention is further described below by means of specific embodiments. The embodiments described in the present invention are only used as illustrations of the present invention and do not limit the scope of the present invention.
[0028] Example 1
[0029] The catalyst was prepared as follows:
[0030] (1) Dry fresh rice husks in an oven at 120°C for 12 h, weigh 1 g of the dried rice husks, and heat them to 400°C for pre-carbonization under nitrogen conditions for 6 h to obtain pre-carbonized rice husks;
[0031] (2) weighing 1 g of the pre-carbonized rice husk obtained in step (1), mixing it with 50 mL of a 5 wt % hydrochloric acid solution and 50 mL of a 5 wt % citric acid, heating it under reflux at 60° C. for 12 h, filtering it, washing it, mixing it with 100 mL of a 0.5 wt % ethylenediaminetetraacetic acid solution, heating it under reflux at 60° C. for 12 h, filtering it, washing it, and vacuum drying it to obtain pre-treated rice husk;
[0032] (3) Weigh 1 g of the pretreated rice husk obtained in step (2), mix it with 30 mL of 0.1 mol / L sodium hydroxide solution, heat it under reflux at 60° C. for 6 h, then filter, wash, and vacuum dry it, and carbonize the rice husk again at 700° C. under nitrogen for 1 h to obtain a rice husk catalyst for olefin epoxidation.
[0033] Cyclohexene oxidation:
[0034] 0.41 g of cyclohexene, 0.1 g of the above-mentioned olefin epoxidation rice husk catalyst, 1.2 g of 30 wt% hydrogen peroxide solution and 10 mL of acetonitrile solution were added into a 25 mL reactor, heated to 70° C. with stirring, and maintained at 70° C. for 2 h. After the reaction, the conversion rate of cyclohexene was 16.4% according to gas phase analysis, the selectivity of cyclohexene oxide was 96.5%, and the utilization efficiency of hydrogen peroxide was 83.4%.
[0035] Example 2
[0036] The catalyst was prepared as follows:
[0037] (1) Dry fresh rice husks in an oven at 120°C for 12 h, weigh 1 g of the dried rice husks, and pre-carbonize them at 200°C under nitrogen for 6 h to obtain pre-carbonized rice husks;
[0038] (2) weighing 1 g of the pre-carbonized rice husk obtained in step (1), mixing it with 50 mL of a 5 wt % hydrochloric acid solution and 50 mL of a 5 wt % citric acid, heating it under reflux at 60° C. for 12 h, filtering it, washing it, mixing it with 100 mL of a 0.5 wt % ethylenediaminetetraacetic acid solution, heating it under reflux at 60° C. for 12 h, filtering it, washing it, and vacuum drying it to obtain pre-treated rice husk;
[0039] (3) Weigh 1 g of the pretreated rice husk obtained in step (2), mix it with 30 mL of 0.1 mol / L sodium hydroxide solution, heat it under reflux at 60° C. for 6 h, then filter, wash, and vacuum dry it, and carbonize the rice husk again at 700° C. under nitrogen for 1 h to obtain a rice husk catalyst for olefin epoxidation.
[0040] Cyclohexene oxidation:
[0041] 0.41 g of cyclohexene, 0.1 g of the above-mentioned olefin epoxidation rice husk catalyst, 1.2 g of 30 wt% hydrogen peroxide solution and 10 mL of acetonitrile solution were added into a 25 mL reactor, heated to 70° C. with stirring, and maintained at 70° C. for 2 h. After the reaction, the conversion rate of cyclohexene was 2.3% according to gas phase analysis, the selectivity of cyclohexene oxide was 87.6%, and the utilization efficiency of hydrogen peroxide was 58.9%.
[0042] Example 3
[0043] The catalyst was prepared as follows:
[0044] (1) Dry fresh rice husks in an oven at 120°C for 12 h, weigh 1 g of the dried rice husks, and heat them to 400°C for pre-carbonization under nitrogen conditions for 6 h to obtain pre-carbonized rice husks;
[0045] (2) weighing 1 g of the pre-carbonized rice husk obtained in step (1), mixing it with 50 mL of a 5 wt % hydrochloric acid solution and 50 mL of a 5 wt % citric acid, heating it under reflux at 60° C. for 12 h, filtering it, washing it, mixing it with 100 mL of a 0.5 wt % tartaric acid solution, heating it under reflux at 60° C. for 12 h, filtering it, washing it, and vacuum drying it to obtain pre-treated rice husk;
[0046] (3) Weigh 1 g of the pretreated rice husk obtained in step (2), mix it with 30 mL of 0.1 mol / L sodium hydroxide solution, heat it under reflux at 60° C. for 6 h, then filter, wash, and vacuum dry it, and carbonize the rice husk again at 700° C. under nitrogen for 1 h to obtain a rice husk catalyst for olefin epoxidation.
[0047] Cyclohexene oxidation:
[0048] 0.41 g of cyclohexene, 0.1 g of the above-mentioned olefin epoxidation rice husk catalyst, 1.2 g of 30 wt% hydrogen peroxide solution and 10 mL of acetonitrile solution were added into a 25 mL reactor, heated to 70° C. with stirring, and maintained at 70° C. for 2 h. After the reaction, the conversion rate of cyclohexene was 4.1% according to gas phase analysis, the selectivity of cyclohexene oxide was 80.5%, and the utilization efficiency of hydrogen peroxide was 47.6%.
[0049] Example 4
[0050] The catalyst was prepared as follows:
[0051] (1) Dry fresh rice husks in an oven at 120°C for 12 h, weigh 1 g of the dried rice husks, and heat them to 400°C for pre-carbonization under nitrogen conditions for 6 h to obtain pre-carbonized rice husks;
[0052] (2) weighing 1 g of the pre-carbonized rice husk obtained in step (1), mixing it with 50 mL of a 5 wt % hydrochloric acid solution and 50 mL of a 5 wt % citric acid, heating it under reflux at 60° C. for 12 h, filtering it, washing it, mixing it with 100 mL of a 0.5 wt % ethylenediaminetetraacetic acid solution, heating it under reflux at 60° C. for 12 h, filtering it, washing it, and vacuum drying it to obtain pre-treated rice husk;
[0053] (3) Weigh 1 g of the pretreated rice husk obtained in step (2), mix it with 30 mL of 0.5 mol / L sodium hydroxide solution, heat it under reflux at 60° C. for 6 h, then filter, wash, and vacuum dry it, and carbonize the rice husk again at 700° C. under nitrogen for 1 h to obtain a rice husk catalyst for olefin epoxidation.
[0054] Cyclohexene oxidation:
[0055] 0.41 g of cyclohexene, 0.1 g of the above-mentioned olefin epoxidation rice husk catalyst, 1.2 g of 30 wt% hydrogen peroxide solution and 10 mL of acetonitrile solution were added into a 25 mL reactor, heated to 70° C. with stirring, and maintained at 70° C. for 2 h. After the reaction, the conversion rate of cyclohexene was 3.5% according to gas phase analysis, the selectivity of cyclohexene oxide was 90.5%, and the utilization efficiency of hydrogen peroxide was 78.9%.
[0056] Example 5
[0057] The catalyst was prepared as follows:
[0058] (1) Dry fresh rice husks in an oven at 120°C for 12 h, weigh 1 g of the dried rice husks, and heat them to 400°C for pre-carbonization under nitrogen conditions for 6 h to obtain pre-carbonized rice husks;
[0059] (2) weighing 1 g of the pre-carbonized rice husk obtained in step (1), mixing it with 50 mL of a 5 wt % hydrochloric acid solution and 50 mL of a 5 wt % citric acid, heating it under reflux at 60° C. for 12 h, filtering it, washing it, mixing it with 100 mL of a 0.5 wt % ethylenediaminetetraacetic acid solution, heating it under reflux at 60° C. for 12 h, filtering it, washing it, and vacuum drying it to obtain pre-treated rice husk;
[0060] (3) Weigh 1 g of the pretreated rice husk obtained in step (2), mix it with 30 mL of 0.1 mol / L sodium hydroxide solution, heat it under reflux at 80° C. for 6 h, then filter, wash, and vacuum dry it, and carbonize the rice husk again at 700° C. under nitrogen for 1 h to obtain a rice husk catalyst for olefin epoxidation.
[0061] Cyclohexene oxidation:
[0062] 0.41 g of cyclohexene, 0.1 g of the above-mentioned olefin epoxidation rice husk catalyst, 1.2 g of 30 wt% hydrogen peroxide solution and 10 mL of acetonitrile solution were added into a 25 mL reactor, heated to 70° C. with stirring, and maintained at 70° C. for 2 h. After the reaction, the conversion rate of cyclohexene was 10.2% according to gas phase analysis, the selectivity of cyclohexene oxide was 94.5%, and the utilization efficiency of hydrogen peroxide was 85.6%.
[0063] Example 6
[0064] The catalyst was prepared as follows:
[0065] (1) Dry fresh rice husks in an oven at 120°C for 12 h, weigh 1 g of the dried rice husks, and heat them to 400°C for pre-carbonization under nitrogen conditions for 1 h to obtain pre-carbonized rice husks;
[0066] (2) weighing 1 g of the pre-carbonized rice husk obtained in step (1), mixing it with 50 mL of a 5 wt % hydrochloric acid solution and 50 mL of a 5 wt % citric acid, heating it under reflux at 60° C. for 12 h, filtering it, washing it, mixing it with 100 mL of a 0.5 wt % ethylenediaminetetraacetic acid solution, heating it under reflux at 60° C. for 12 h, filtering it, washing it, and vacuum drying it to obtain pre-treated rice husk;
[0067] (3) Weigh 1 g of the pretreated rice husk obtained in step (2), mix it with 30 mL of 0.1 mol / L sodium hydroxide solution, heat it under reflux at 60° C. for 6 h, then filter, wash, and vacuum dry it, and carbonize the rice husk again at 400° C. under nitrogen for 1 h to obtain a rice husk catalyst for olefin epoxidation.
[0068] Cyclohexene oxidation:
[0069] 0.41 g of cyclohexene, 0.1 g of the above-mentioned olefin epoxidation rice husk catalyst, 1.2 g of 30 wt% hydrogen peroxide solution and 10 mL of acetonitrile solution were added into a 25 mL reactor, heated to 70° C. with stirring, and maintained at 70° C. for 2 h. After the reaction, the conversion rate of cyclohexene was 2.5% according to gas phase analysis, the selectivity of cyclohexene oxide was 96.5%, and the utilization efficiency of hydrogen peroxide was 85.3%.
[0070] Example 7
[0071] The catalyst was prepared as follows:
[0072] (1) Dry fresh rice husks in an oven at 120°C for 12 h, weigh 1 g of the dried rice husks, and heat them to 400°C for pre-carbonization under nitrogen conditions for 1 h to obtain pre-carbonized rice husks;
[0073] (2) weighing 1 g of the pre-carbonized rice husk obtained in step (1), mixing it with 50 mL of a 5 wt % hydrochloric acid solution and 50 mL of a 5 wt % citric acid, heating it under reflux at 60° C. for 12 h, filtering it, washing it, mixing it with 100 mL of a 0.5 wt % ethylenediaminetetraacetic acid solution, heating it under reflux at 60° C. for 12 h, filtering it, washing it, and vacuum drying it to obtain pre-treated rice husk;
[0074] (3) Weigh 1 g of the pretreated rice husk obtained in step (2), mix it with 30 mL of 0.1 mol / L sodium hydroxide solution, heat it under reflux at 60° C. for 6 h, then filter, wash, and vacuum dry it, and carbonize the rice husk again at 700° C. under nitrogen for 1 h to obtain a rice husk catalyst for olefin epoxidation.
[0075] Cyclohexene oxidation:
[0076] 0.41 g of cyclohexene, 0.1 g of the above-mentioned olefin epoxidation rice husk catalyst, 2.4 g of 30 wt% hydrogen peroxide solution and 10 mL of acetonitrile solution were added into a 25 mL reactor, heated to 70° C. with stirring, and maintained at 70° C. for 2 h. After the reaction, the conversion rate of cyclohexene was 28.9% according to gas phase analysis, the selectivity of cyclohexene oxide was 96.5%, and the utilization efficiency of hydrogen peroxide was 79.3%.
[0077] Comparative Example 1
[0078] Referring to the preparation method of cyclohexene epoxidation catalyst in Example 1, the difference is that the carbonized rice husk is not treated with acidic solution and complexing agent solution, and other operations and conditions remain unchanged. After the reaction, the conversion rate of cyclohexene in gas phase analysis is 2.1%, the selectivity of cyclohexene oxide is 82.3%, and the utilization efficiency of hydrogen peroxide is 58.9%.
[0079] Compared with Example 1 and Comparative Example 1, impurities such as metals exist in the rice husks that have not been pre-carbonized by treatment with an acidic solution or a complexing agent solution, resulting in a decrease in the catalytic performance of the catalyst.
[0080] Comparative Example 2
[0081] Referring to the preparation method of cyclohexene epoxidation catalyst in Example 1, the difference is that the carbonized rice husks are not treated with an alkaline solution, but are directly carbonized, and other operations and conditions remain unchanged. After the reaction, the conversion rate of cyclohexene in gas phase analysis is 1.2%, the selectivity of cyclohexene oxide is 3.6%, and the utilization efficiency of hydrogen peroxide is 84.6%.
[0082] Comparing Example 1 and Comparative Example 2, the alkaline solution treatment can form special active sites on the surface of the pretreated rice husk, thereby enhancing the performance of the catalyst in catalyzing olefin epoxidation.
[0083] Comparative Example 3
[0084] Referring to the preparation method of cyclohexene epoxidation catalyst in Example 1, the difference is that the pretreated rice husk is treated with an alkaline solution at 120° C. for 6 hours, and other operations and conditions remain unchanged. After the reaction, the conversion rate of cyclohexene in gas phase analysis is 0.5%, the selectivity of cyclohexene oxide is 72.3%, and the utilization efficiency of hydrogen peroxide is 67.9%.
[0085] Comparative Example 1 and Comparative Example 3, the treatment of rice husks with an alkaline solution at 120° C. resulted in a significant decrease in the SiO 2 content of the rice husks and a decrease in the number of active sites on the surface.
[0086] It should be noted that the above is a preferred embodiment of the present invention. It should be pointed out that for the technology in the field, several improvements and supplements can be made without departing from the method of the present invention, and these improvements and supplements should also be regarded as the scope of protection of the present invention.
Claims
1. A method for preparing a rice husk catalyst for olefin epoxidation, characterized in that: The steps include: (1) pre-carbonizing rice husks under nitrogen conditions to obtain pre-carbonized rice husks; (2) treating the pre-carbonized rice husk with an acid and a complexing agent to obtain pre-treated rice husk; (3) treating the pretreated rice husks with alkali to obtain alkali-treated rice husks; (4) The alkali-treated rice husk is carbonized under nitrogen conditions to obtain a rice husk catalyst for olefin epoxidation.
2. The method for preparing the olefin epoxidation rice husk catalyst according to claim 1, characterized in that: The pre-carbonization temperature in step (1) is 200-400° C. and the time is 6-12 hours.
3. The method for preparing the olefin epoxidation rice husk catalyst according to claim 1, characterized in that: The specific steps of the acid treatment in step (2) are: mixing the pre-carbonized rice husks with the acidic solution, heating and refluxing the mixture, and then filtering and washing the mixture; The heating reflux reaction temperature is 40-120°C and the time is 6-24h; The ratio of the pre-carbonized rice husk to the acidic solution is 1 g: 10-100 mL; The concentration of the acidic solution is 1-5wt%; The acidic solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, oxalic acid and citric acid.
4. The method for preparing the olefin epoxidation rice husk catalyst according to claim 1, characterized in that: The specific steps of the complexing agent treatment in step (2) are: mixing the rice husks treated with acid with the complexing agent solution, heating and refluxing the mixture, and then filtering, washing, and vacuum drying the mixture; The heating reflux reaction temperature is 40-120°C and the time is 6-24h; The dosage ratio of the pre-carbonized rice husk and the complexing agent solution is 1g: 10-100mL; The complexing agent solution is selected from one or more of ethylenediaminetetraacetic acid, aminotriacetic acid, citric acid, and tartaric acid; the concentration of the complexing agent solution is 0.1-1wt%.
5. The method for preparing the olefin epoxidation rice husk catalyst according to claim 1, characterized in that: The specific steps of the alkali treatment in step (3) are: mixing the pretreated rice husks with the alkaline solution, heating and refluxing, and then filtering, washing, and vacuum drying; The concentration of the alkaline solution is 0.01-0.5 mol / L; The dosage ratio of the pretreated rice husk and the alkaline solution is 1g:10-50mL; The alkaline solution is one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and potassium carbonate; The heating reflux reaction has a temperature of 40-120° C. and a time of 6-24 hours.
6. The method for preparing the olefin epoxidation rice husk catalyst according to claim 1, characterized in that: The carbonization temperature in step (4) is 400-800°C and the time is 1-4h.
7. A rice husk catalyst for olefin epoxidation prepared by the method according to any one of claims 1 to 6.
8. Use of the rice husk catalyst according to claim 7 in olefin epoxidation.
9. The use according to claim 8, characterized in that: Cyclohexene, olefin epoxidation rice husk catalyst, hydrogen peroxide solution and acetonitrile solution are added into a reaction kettle and reacted under heating and stirring.