Preparation method of benzyl alcohol

Abstract

The invention discloses a preparation method of benzyl alcohol, which comprises the following steps: taking gas-phase benzene and formaldehyde as raw materials, reacting in a fixed bed reactor filled with a supported catalyst, condensing the obtained reactant, rectifying and separating to obtain a benzyl alcohol product, the supported catalyst comprises active metal and a beta molecular sieve carrier; the active metal is preferably one or more of iron, cobalt, nickel and zinc. The method can generate benzyl alcohol with high selectivity, has high atom economy, and avoids the problems that the conventional route is not environment-friendly and the product contains chlorine.

Description

Technical Field

[0001] The invention relates to a synthesis method, in particular to a preparation method of benzyl alcohol. Background Art

[0002] Benzyl alcohol is an excellent solvent and an important intermediate for synthetic spices and medicines. It is widely used in the fields of photosensitivity, dyes, cosmetics, coatings and inks. Benzyl alcohol has many advantages when used as a diluent for epoxy resins. For example, benzyl alcohol itself is non-toxic and non-volatile. After curing, it can be well compatible with epoxy resins without migration. It can promote the reaction of epoxy resins and amines, accelerate the reaction speed, has good hydrophobic properties, can significantly improve the gloss of coatings, reduce the appearance of birch phenomenon, and can improve the toughness of cured products. With the development of related industries, the demand for benzyl alcohol at home and abroad is increasing. At present, the industrial preparation of benzyl alcohol is mainly through the hydrolysis of benzyl chloride, but this method consumes a lot of energy, is heavily polluted, and the product contains chlorine, which affects its application in the fields of food, medicine and spices. It is of great significance to develop a new atomic economic route for preparing benzyl alcohol.

[0003] The document "Wu Xianchun, Shan Xilin, Dong Qun, et al. A new route for the synthesis of benzyl alcohol and benzyl ether from benzene and formaldehyde over shape-selective catalysts [J]. Fine Chemicals, 2001 (2): 114-116." discloses a method for preparing benzyl alcohol and benzyl ether using benzene and formaldehyde as raw materials. However, the conversion rate of benzene does not exceed 51.98%, and the selectivity of benzyl alcohol does not exceed 53.1%, and there is still much room for improvement. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing benzyl alcohol. The method can produce benzyl alcohol with high selectivity and high atom economy, and avoids the problems of conventional routes being environmentally unfriendly and containing chlorine in the product.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing benzyl alcohol comprises taking gaseous benzene and formaldehyde as raw materials, reacting in a fixed bed reactor loaded with a supported catalyst, and condensing and rectifying the obtained reactants to obtain a benzyl alcohol product.

[0007] The supported catalyst comprises an active metal and a β molecular sieve carrier; the active metal is preferably one or more of iron, cobalt, nickel and zinc; preferably, the content of the active metal in the supported catalyst is 1-2 wt%.

[0008] The present invention does not impose any restrictions on the preparation method of the supported catalyst, and the supported catalyst can be obtained by referring to any known preparation method of the supported catalyst, such as impregnation method, precipitation method, pyrolysis method, ion exchange method, vapor deposition method, sol-gel method, electrochemical method, etc. From the perspective of simple operation and easy availability of raw materials, the impregnation method and / or precipitation method are preferably used for preparation.

[0009] As a feasible example of the method for preparing the supported catalyst in the present invention, the method comprises the following steps:

[0010] a. First, calcine the β molecular sieve to remove impurities. The preferred calcination conditions are calcination at 400-650°C for 1-5h;

[0011] b. Immerse the β molecular sieve in the active metal salt solution and stir and mix thoroughly;

[0012] c. Separate the solid product of the catalyst precursor, dry it and then calcine it to obtain a supported catalyst; preferably, the calcination condition is calcination at 500-800° C. for 1-5 hours.

[0013] In step c, the catalyst precursor solid product is separated by suction filtration, rotary evaporation, etc. without limitation.

[0014] In some preferred examples, the average pore size of the β molecular sieve is 0.55-0.65 nm.

[0015] In some preferred examples, the molar ratio of benzene to formaldehyde is n(benzene):n(formaldehyde)=0.95-1.05.

[0016] In some preferred examples, the mass space velocity of the benzene and formaldehyde reaction feed is 0.2-1h -1 , preferably 0.3-0.5h -1 .

[0017] In some preferred examples, the reaction temperature of benzene and formaldehyde is 180-250° C., preferably 200-220° C.; and / or the reaction pressure is normal pressure.

[0018] The source of formaldehyde in the present invention is not limited in any way, and it can be directly purchased from commercial products, or obtained by depolymerization of trioxymethylene according to conventional methods. Preferably, the depolymerization temperature is, for example, 190-220°C, preferably 200-210°C.

[0019] The present invention uses beta molecular sieve as a catalyst carrier, which can show good shape selection function through its "confinement" effect, avoid excessive reaction of benzyl alcohol to generate large molecules such as diphenylmethane, and further improve the reaction selectivity through active metal modification. Compared with the prior art, the scheme of the present invention can improve the selectivity of benzyl alcohol to more than 90%. DETAILED DESCRIPTION

[0020] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0021] The raw materials and reagents used in the examples and comparative examples of the present invention were purchased from commercial sources unless otherwise specified.

[0022] β molecular sieve-1: average pore size 0.6 nm, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0023] β molecular sieve-2: average pore size 0.65 nm, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0024] β molecular sieve-3: average pore size 0.55 nm, purchased from Beijing Inokai Technology Co., Ltd.

[0025] Trioxymethylene: purchased from Beijing Inokai Technology Co., Ltd.

[0026] Product content test method:

[0027] High performance liquid chromatography: Shimadzu LC-20AT, operating conditions: chromatographic column: Waters XSelect HSS T3 5μm×4.6mm×250mm, detection wavelength 233nm, mobile phase: acetonitrile / water (water containing 0.1% phosphoric acid) = 35 / 65, elution mode: isocratic elution, flow rate: 1.0mL / min, column temperature 30℃, injection volume 10μL.

[0028] [Preparation Example 1] Co / β molecular sieve catalyst

[0029] First, β molecular sieve-1 was calcined in a muffle furnace at 550°C for 2h to remove impurities. 98g of the calcined β molecular sieve was immersed in 200g of deionized water solution dissolved with 4.94g of cobalt nitrate hexahydrate, and the mixture was fully stirred and mixed. Then, the stirred mixture was placed in a rotary evaporator and rotary evaporated for 2h at room temperature and negative pressure (1kpaA). The obtained catalyst precursor was dried in a blast drying oven at 120°C for 2h, and finally calcined in a muffle furnace at 550°C for 2h to obtain Co / β molecular sieve catalyst 1 with a metal Co loading of 1wt%.

[0030] [Preparation Example 2] Fe / β molecular sieve catalyst

[0031] First, β molecular sieve-2 was calcined in a muffle furnace at 550°C for 2h to remove impurities. 98g of the calcined β molecular sieve was immersed in 200g of deionized water solution dissolved with 8.6g of ferric nitrate, and the mixture was fully stirred and mixed. Then, the stirred mixture was placed in a rotary evaporator and rotary evaporated for 2h at room temperature and negative pressure (1kpaA). The obtained catalyst precursor was dried in a blast drying oven at 120°C for 2h, and finally calcined in a muffle furnace at 550°C for 2h to obtain Fe / β molecular sieve catalyst 2 with a metal Fe loading of 2wt%.

[0032] [Preparation Example 3] Ni / β molecular sieve catalyst

[0033] First, β molecular sieve-3 was calcined in a muffle furnace at 550°C for 2h to remove impurities. 98g of the calcined β molecular sieve was immersed in 200g of deionized water dissolved with 7.425g of nickel nitrate, and the mixture was fully stirred and mixed. Then, the stirred mixture was placed in a rotary evaporator and rotary evaporated for 2h at room temperature and negative pressure (1kpaA). The obtained catalyst precursor was dried in a blast drying oven at 120°C for 2h, and finally calcined in a muffle furnace at 550°C for 2h to obtain a Ni / β molecular sieve catalyst 3 with a metal Ni loading of 1.5wt%.

[0034] [Preparation Example 4] Fe-Co / β molecular sieve catalyst

[0035] First, β molecular sieve-1 was calcined in a muffle furnace at 550°C for 2h to remove impurities. 98g of the calcined β molecular sieve was immersed in 200g of deionized water dissolved with 4.94g of cobalt nitrate hexahydrate and 4.3g of ferric nitrate, and the mixture was fully stirred and mixed. Then, the stirred mixture was placed in a rotary evaporator and rotary evaporated for 2h at room temperature and negative pressure (1kpaA). The obtained catalyst precursor was dried in a blast drying oven at 120°C for 2h, and finally calcined in a muffle furnace at 550°C for 2h to obtain Fe-Co / β molecular sieve catalyst 4 with Co and Fe loadings of 1wt% each.

[0036] [Examples 1-4]

[0037] (1) The solid trioxymethylene powder was first heated to 70°C in an oil bath in a glass bottle to melt into a liquid, and then quantitatively pumped into a cracking reaction tube (empty tube, no catalyst, electric heating jacket for heating and temperature control) by a horizontal flow pump for cracking to generate formaldehyde. The cracking reaction conditions are shown in Table 1.

[0038] (2) Benzene was pumped into a continuous fixed bed reactor filled with 100 g of catalyst, and the gaseous formaldehyde generated by the cracking of trioxymethylene was introduced into the fixed bed reactor to react with benzene under normal pressure. The reaction conditions were shown in Table 1. After the reactants were cooled by a condenser, samples were taken for analysis of the reaction conversion rate and selectivity. The results are shown in Table 2.

[0039] Table 1

[0040]

[0041]

[0042] Table 2

[0043] Example 1 Example 2 Example 3 Example 4 Benzene conversion 52.2％ 49.2％ 54.4％ 53.9％ Benzyl alcohol selectivity 90.4％ 91.3％ 90.9％ 91.1％

[0044] [Comparative Example 1]

[0045] Benzene and formaldehyde were intermittently reacted in a three-necked round-bottom flask. 100 g of benzene, 110 g of formaldehyde aqueous solution (concentration 35%), and 4.2 g of p-toluenesulfonic acid were added to the three-necked round-bottom flask, stirred, heated to 200°C, reacted for 3 hours, and samples were taken for analysis and calculation. The benzene conversion rate was 61.2%, the benzyl alcohol selectivity was 0.38%, and the diphenylmethane selectivity was 93.5%.

[0046] [Comparative Example 2]

[0047] The reaction was carried out in a method substantially the same as that in Example 1, except that the supported catalyst 1 was replaced by β molecular sieve 1. The reactants were sampled and analyzed, and the benzene conversion rate was 51.1%, and the benzyl alcohol selectivity was 80.6%.

[0048] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing benzyl alcohol, characterized in that: The method uses gaseous benzene and formaldehyde as raw materials, reacts in a fixed bed reactor loaded with a supported catalyst, and the obtained reactants are condensed and then distilled to obtain benzyl alcohol products. The supported catalyst comprises an active metal and a β molecular sieve carrier; the active metal is preferably one or more of iron, cobalt, nickel and zinc; preferably, the content of the active metal in the supported catalyst is 1-2 wt%.

2. The method for preparing benzyl alcohol according to claim 1, characterized in that The molar ratio of benzene to formaldehyde is n(benzene):n(formaldehyde)=0.95-1.

05.

3. The method for preparing benzyl alcohol according to claim 1 or 2, characterized in that: The mass space velocity of the benzene and formaldehyde reaction feed is 0.2-1h -1 , preferably 0.3-0.5h -1 .

4. The method for preparing benzyl alcohol according to any one of claims 1 to 3, characterized in that: The reaction temperature of benzene and formaldehyde is 180-250° C., preferably 200-220° C.; and / or the reaction pressure is normal pressure.

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