A method for preparing cyclohexyl methyl ether by catalytic conversion of phenol

Abstract

The invention discloses a method for preparing cyclohexyl methyl ether by catalytic conversion of phenol, and belongs to the field of high value-added chemicals prepared by biomass conversion. The process of the present invention mixes phenol and methanol according to a molar ratio of 1: (1-4), adds an oxygen content of 4.9% to 12.0%, a carbon-supported solid catalyst loaded with a noble metal, and reacts in a hydrogen environment, with a reaction temperature of 110 to 200 ° C. Using the above scheme, phenol is catalyzed into cyclohexyl methyl ether in one step, with good catalytic activity and high selectivity, and provides new ideas and methods 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 particularly relates to a method for preparing cyclohexyl methyl ether by catalytic conversion of phenol. Background Art

[0002] Lignocellulose is the most abundant biomass available as a renewable feedstock for synthetic chemicals. The value-added production of lignocellulosic biomass has the potential to reduce over-reliance on fossil feedstocks in chemical production. Every year, humans discard over 40 million tons of inedible plant materials, such as straw, corn stover, and wood shavings. Converting these waste plants into high-value-added chemicals holds great promise. Selective hydroetherification of lignin-derived materials yields high-value methoxylated chemicals, which are key intermediates in the production of pharmaceuticals, pesticides, fragrances, and natural products. Therefore, using phenol as a feedstock offers promising applications.

[0003] However, the current process for preparing cyclohexyl methyl ether from lignin still suffers from high reaction temperatures and long reaction times, with a cyclohexyl methyl ether yield of 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 using a physical mixture of a Pd / C catalyst and an acid catalyst requires a temperature of 200°C and 4 MPa of hydrogen (Jiayue He, Chen Zhao, Johannes A. Lercher, Journal of Catalysis, 309, 2014, 362-375). However, there are few methods for converting lignin into cyclohexyl methyl ether in one step. The two-step method, which involves alkylating the phenolic hydroxyl group of phenol and then hydrogenating the benzene ring, suffers from drawbacks such as difficulty in product separation, high separation costs, and large losses (Sohaib Haseeb, Jesse R. Vanderveen, et al. Green Chem., 2021, 23, 2457-2463). There are reports of the preparation of cyclohexyl methyl ether in China: a Chinese patent application number (CN202410327210.5) reports on the electrocatalytic conversion of guaiacol to methoxycyclohexane.

[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. The process is simple, easy to operate, the catalyst is readily available, multiple cycles can be performed, and the process is easy to industrialize.

[0006] The present invention specifically adopts the following technical solutions:

[0007] The present invention provides a method for preparing cyclohexyl methyl ether by catalytic conversion of phenol, comprising the following steps:

[0008] Step 1: mixing carbon powder with nitric acid solution and heating to obtain an oxygen-containing activated carbon support; taking a noble metal salt, adding it to ethanol and adding hydrochloric acid dropwise, sonicating the mixture, adding the oxygen-containing activated carbon support and mixing, evaporating to dryness, and then calcining to obtain an oxygen-doped carbon material loaded with noble metal nanoparticles;

[0009] Step 2: Phenol and methanol are mixed, and the oxygen-doped carbon material loaded with noble metal nanoparticles obtained in step 1 is used as a catalyst, and heated in a hydrogen environment for reaction. After the reaction is completed, the mixture is cooled to obtain cyclohexyl methyl ether.

[0010] Furthermore, in step 1, the temperature of mixing the carbon powder and the nitric acid solution and heating the mixture is 100° C. and the time is 4 h.

[0011] Furthermore, the noble metal salt in step 1 is palladium chloride.

[0012] Furthermore, the calcination after evaporation in step 1 is specifically as follows: first calcining in air at 150°C in a muffle furnace for 2 h, and then calcining the obtained powder in a tube furnace with a flow rate of 10% H2 / Ar and 150°C for 2 h; the heating rate is 5°C / min.

[0013] Furthermore, the oxygen-doped carbon material loaded with noble metal nanoparticles obtained in step 1 has a noble metal loading of 1 wt% and an oxygen content of 4.9%-12.0%.

[0014] Furthermore, the molar ratio of step 2 phenol to methanol is 1:(1-4).

[0015] Furthermore, the hydrogen pressure of the catalytic conversion in step 2 is 2 MPa.

[0016] Furthermore, the heating reaction temperature in step 2 is 110-200° C. and the time is 20 h.

[0017] The reaction process is as follows:

[0018]

[0019] The beneficial effects of the present invention are as follows: 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 multiple times, large-scale production is possible, and industrialization is easy; and the raw material phenol of the present invention is low in price and easily available. DETAILED DESCRIPTION

[0020] To make the objects, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be described clearly and completely below in conjunction with the examples. Where specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art in the art. 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" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Example 1: Preparation of Pd / CO catalyst

[0023] 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 to obtain activated carbon supports with oxygen contents of 4.9%, 8.3%, and 12.0%, respectively.

[0024] 2. Take 0.0169 g of PdCl2 and add it to 20 mL of 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 of 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 air at 150°C in a muffle furnace for 2 h (heating rate of 5°C / min). The obtained solid powder is calcined in a tube 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%).

[0025] Example 2-13: Preparation of cyclohexyl methyl ether

[0026] Taking Example 2 in Table 1 as an example: 17.4 g of phenol and 7.5 mL of methanol were weighed and added to a 25 mL reactor. 0.05 g of the catalyst Pd / CO (with an oxygen content of 4.9% on the carbon support and 1 wt% of precious metal) was then added. H₂ gas was used to displace the air in the reactor five to six times to reduce the oxygen content. The reaction mixture was heated to 150°C for 20 hours. After the reaction was complete, the mixture was rapidly cooled to room temperature and a sample was collected.

[0027] 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 Example 2.

[0028] Table 1 Preparation Example of Cyclohexyl Methyl Ether

[0029]

[0030] As shown in Table 1, the catalyst of the present invention can achieve efficient one-step catalytic conversion of phenol to cyclohexyl methyl ether. In Example 12, the conversion rate of phenol to cyclohexyl methyl ether was 98%, and the yield of cyclohexyl methyl ether was 85.3%.

[0031] The embodiments described above merely represent several preferred embodiments of the present invention. While the descriptions are relatively specific and detailed, they are not intended to limit the present invention. It should be noted that those skilled in the art will readily appreciate that the present invention is susceptible to various variations and modifications. Any modifications, equivalent substitutions, or improvements within the scope of the present invention are intended to be included within the scope of protection 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 with nitric acid solution and heating to obtain an oxygen-containing activated carbon support; separately taking palladium chloride, adding it to ethanol and adding hydrochloric acid dropwise, ultrasonicating the mixture, adding the oxygen-containing activated carbon support and mixing, evaporating to dryness, and then calcining to obtain an oxygen-doped carbon material loaded with noble metal nanoparticles; The carbon powder and nitric acid solution were mixed and heated at 100°C for 4 hours. The powder was then calcined in a muffle furnace at 150°C for 2 hours in air, and then calcined in a tube furnace at 150°C for 2 hours with a flow rate of 10% H2 / Ar. The heating rate was 5°C / min. The resulting oxygen-doped carbon material loaded with noble metal nanoparticles had a noble metal loading of 1 wt% and an oxygen content of 4.9%-12.0%. Step 2: Mix phenol and methanol, use the oxygen-doped carbon material loaded with noble 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; The hydrogen pressure for catalytic conversion is 2 MPa, the heating reaction temperature is 110-200°C, and the reaction time is 20 h.

2. 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).

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