Method for preparing cyclohexyl methyl ether through catalytic conversion of phenol

Abstract

The invention discloses a method for preparing cyclohexyl methyl ether through catalytic conversion of phenol, and belongs to the field of preparation of high value-added chemicals through biomass conversion. The process comprises the following steps: mixing phenol and methanol according to a molar ratio of 1: (1-4), adding a noble metal-loaded carbon carrier solid catalyst with an oxygen content of 4.9-12.0%, and carrying out a reaction in a hydrogen environment at a reaction temperature of 110-200 DEG C; by adopting the scheme, phenol is catalyzed to be converted into cyclohexyl methyl ether in one step, the catalytic activity is good, the selectivity is high, and a new thought and method are provided for efficient catalytic conversion of biomass.

Description

Technical Field

[0001] The invention belongs to the field of preparing high value-added chemicals by biomass conversion, and specifically relates to a method for preparing cyclohexyl methyl ether by catalytic conversion of phenol. Background Art

[0002] Lignocellulose is the most abundant biomass that can be used as a renewable raw material for synthetic chemical products. The valorization of lignocellulosic biomass has the potential to reduce the over-dependence on fossil raw materials in the production of chemicals. Every year, humans throw away more than 40 million tons of inedible plant materials such as straw, corn stover and wood shavings. There is a good prospect for converting these waste plants into high-value-added chemicals. Selective hydroetherification of lignin-derived materials produces high-value methoxy chemicals, which are key intermediates in the production of pharmaceuticals, pesticides, perfumes and natural products. Therefore, phenol as a raw material has broad application prospects.

[0003] However, the current process of preparing cyclohexyl methyl ether from lignin still has high reaction temperature, long reaction time, and the yield of cyclohexyl methyl ether is only 39% (Meng Wang, Oliver Y. Gutiérrez, et al. Angew.Chem.Int.Ed, 2018, 57, 3747-3751). The reaction of phenol to cyclohexyl methyl ether by physical mixing of Pd / C catalyst and acid catalyst needs to be completed at 200°C and 4 MPa of hydrogen (Jiayue He a, Chen Zhao a, Johannes A.Lercher, Journal of Catalysis, 309, 2014, 362-375). However, there are not many methods for converting lignin to prepare cyclohexyl methyl ether in one step. The two-step method of alkylating the phenolic hydroxyl group of phenol and then hydrogenating the benzene ring has disadvantages such as difficulty in product separation, high separation cost, and large losses (Sohaib Haseeb, Jesse R. Vanderveen, et al. Green Chem., 2021, 23, 2457-2463). There have been reports on the preparation of cyclohexyl methyl ether in China: a Chinese patent with application number (CN202410327210.5) reported a method for converting guaiacol to prepare methoxycyclohexane using an electrocatalytic method.

[0004] In view of this, it is of great significance to develop new methods for the preparation of cyclohexyl methyl ether, especially to use cheap lignin resources to prepare high-value cyclohexyl methyl ether under milder conditions. Summary of the invention

[0005] The object of the present invention is to provide a method for producing cyclohexyl methyl ether by hydrogenating phenol, which has simple process, convenient operation, readily available catalyst, can be recycled multiple times, and is easy to industrialize.

[0006] The present invention specifically adopts the following technical solutions: The present invention provides a method for preparing cyclohexyl methyl ether by catalytic conversion of phenol, comprising the following steps: Step 1: mixing carbon powder and nitric acid solution and heating them to obtain an oxygen-containing activated carbon carrier; taking another noble metal salt, adding it to ethanol and dropping hydrochloric acid, ultrasonicating the mixture, adding the oxygen-containing activated carbon carrier and mixing, evaporating and calcining to obtain an oxygen-doped carbon material loaded with noble metal nanoparticles; Step 2: Mix phenol and methanol, use the oxygen-doped carbon material loaded with precious metal nanoparticles obtained in step 1 as a catalyst, heat and react in a hydrogen environment, and cool after the reaction to obtain cyclohexyl methyl ether.

[0007] Furthermore, in step 1, the temperature of mixing and heating the carbon powder and the nitric acid solution is 100° C. and the time is 4 h.

[0008] Furthermore, the noble metal salt in step 1 is palladium chloride.

[0009] Furthermore, the calcination after evaporation in step 1 is specifically as follows: firstly calcining in air at 150°C in a muffle furnace for 2 h, and then calcining the obtained powder in a tube furnace at a flow rate of 10% H2 / Ar and 150°C for 2 h; the heating rate is 5°C / min.

[0010] Furthermore, the oxygen-doped carbon material loaded with precious metal nanoparticles obtained in step 1 has a precious metal loading of 1 wt% and an oxygen content of 4.9%-12.0%.

[0011] Furthermore, the molar ratio of step diphenol to methanol is 1:(1-4).

[0012] Furthermore, the hydrogen pressure of the catalytic conversion in step 2 is 2 MPa.

[0013] Furthermore, the heating reaction temperature in step 2 is 110-200° C. and the time is 20 h.

[0014] The reaction process is as follows:

[0015] The beneficial effects of the present invention are as follows: the cyclohexyl methyl ether is obtained by the hydrogenation / acetalization / hydrogenolysis method using the above scheme, the process is simple, the operation is convenient, the catalyst is easily available and can be recycled for multiple times, and can be mass-produced and easily industrialized; and the raw material phenol of the present invention is low in price and easily available. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0018] Example 1: Preparation of Pd / CO catalyst 1. Place 1.0 g of carbon powder and 50 mL of nitric acid solution (5%, 10%, 20%) in a 100 mL conical flask, stir and heat at 100 °C for 4 h, then cool, rinse with 5 L of deionized water and filter, then transfer the product to an oven and dry for 12 h, and finally obtain activated carbon carriers with oxygen contents of 4.9%, 8.3%, and 12.0%, respectively.

[0019] 2. Take 0.0169 g PdCl2 and add it to 20 mL ethanol and add two drops of 2 mol / L hydrochloric acid solution to mix. After the mixture is clarified and transparent under ultrasound, 1.0 g oxygen-doped carbon material is added and mixed. The mixture is heated at 70°C to completely evaporate the ethanol. After evaporation, it is calcined in a muffle furnace at 150°C for 2 h (heating rate of 5°C / min). The solid powder is calcined in a tubular furnace at a flow rate of 10% H2 / Ar and 150°C for 2 h (heating rate of 5°C / min) to obtain the catalyst Pd / CO (noble metal content is 1 wt%).

[0020] Example 2-13: Preparation of cyclohexyl methyl ether Take Example 2 in Table 1 as an example: 17.4 g phenol and 7.5 mL methanol were weighed and added to a 25 mL reactor, and then 0.05 g catalyst Pd / CO (the oxygen content on the carbon carrier was 4.9%, and the amount of precious metal was 1 wt%) was added. H2 gas replaced the air in the reactor five to six times to reduce the oxygen content in the reactor. Heat to 150°C and maintain for 20 hours. Wait for the reaction to end, quickly cool to room temperature, and collect samples.

[0021] For Examples 3-13, except for the different implementation conditions mentioned in the table below, the rest of the operation methods are the same as those of Example 2.

[0022] Table 1 Preparation Example of Cyclohexyl Methyl Ether

[0023] As shown in Table 1, the catalyst of the present invention can realize one-step efficient catalytic conversion of phenol to cyclohexyl methyl ether. In the case of Example 12, the conversion rate of phenol to cyclohexyl methyl ether is 98%, and the yield of cyclohexyl methyl ether is 85.3%.

[0024] The embodiments described above only express several preferred embodiments of the present invention, and the descriptions thereof are relatively specific and detailed, but are not intended to limit the present invention. It should be noted that for those skilled in the art, the present invention may also have various changes and modifications, and any modifications, equivalent substitutions, improvements, etc. made within the concept and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing cyclohexyl methyl ether by catalytic conversion of phenol, characterized in that: The steps include: Step 1: mixing carbon powder and nitric acid solution and heating them to obtain an oxygen-containing activated carbon carrier; taking another noble metal salt, adding it to ethanol and dropping hydrochloric acid, ultrasonicating the mixture, adding the oxygen-containing activated carbon carrier and mixing, evaporating and calcining to obtain an oxygen-doped carbon material loaded with noble metal nanoparticles; Step 2: Mix phenol and methanol, use the oxygen-doped carbon material loaded with precious metal nanoparticles obtained in step 1 as a catalyst, heat and react in a hydrogen environment, and cool after the reaction to obtain cyclohexyl methyl ether.

2. The method for preparing cyclohexyl methyl ether by catalytic conversion of phenol according to claim 1, characterized in that: Step 1: The carbon powder and nitric acid solution are mixed and heated at a temperature of 100° C. for 4 h.

3. The method for preparing cyclohexyl methyl ether by catalytic conversion of phenol according to claim 1, characterized in that: The noble metal salt in step 1 is palladium chloride.

4. The method for preparing cyclohexyl methyl ether by catalytic conversion of phenol according to claim 1, characterized in that: The calcination after evaporation in step 1 is specifically as follows: firstly calcining in air at 150°C in a muffle furnace for 2 h, and then calcining the obtained powder in a tube furnace at a flow rate of 10% H2 / Ar and 150°C for 2 h; the heating rate is 5°C / min.

5. The method for preparing cyclohexyl methyl ether by catalytic conversion of phenol according to claim 1, characterized in that: The oxygen-doped carbon material loaded with precious metal nanoparticles obtained in step 1 has a precious metal loading of 1 wt% and an oxygen content of 4.9%-12.0%.

6. The method for preparing cyclohexyl methyl ether by catalytic conversion of phenol according to claim 1, characterized in that: The molar ratio of step 2 phenol to methanol is 1:(1-4).

7. The method for preparing cyclohexyl methyl ether by catalytic conversion of phenol according to claim 1, characterized in that: The hydrogen pressure for the catalytic conversion in step 2 is 2 MPa.

8. The method for preparing cyclohexyl methyl ether by catalytic conversion of phenol according to claim 1, characterized in that: The heating reaction temperature in step 2 is 110-200°C and the time is 20 h.

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