Method for preparing benzaldehyde dimethyl acetal by catalyzing benzaldehyde through composite oxide

Abstract

The invention provides a method for preparing benzaldehyde dimethyl acetal by catalyzing benzaldehyde through a composite oxide. According to the method, benzaldehyde is used as a raw material, WO3 / SiO2 is used as a catalyst, methanol is used as a solvent, and the benzaldehyde dimethyl acetal is obtained through an autocatalytic reaction under the condition of normal temperature. The method disclosed by the invention has the advantages of low catalytic material cost, mild conditions, simplicity in operation, high catalytic efficiency and the like, and has a good industrial application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of efficient utilization of solid acids in catalysts, and particularly relates to a method for preparing benzaldehyde dimethyl acetal by catalyzing benzaldehyde with a composite oxide. Background Art

[0002] Liquid acids such as H2SO4, H3PO4, and BF3, as B-acids, have wide applications in organic reactions. However, traditional liquid acid catalysts are prone to cause environmental pollution during catalytic reactions, and the catalysts are not easy to recover. The reaction conditions are harsh, the post-treatment is complicated, and the yield and selectivity are low. At present, a large number of new solid acid catalysts have gradually replaced homogeneous catalysts and are widely used in organic synthesis research and chemical production. For example, metal oxides, clays, molecular sieves, etc. Solid acid catalysts have the advantages of being inexpensive and easily available, not polluting the environment, not corroding equipment, being easy to recover and reuse, and having mild reaction conditions.

[0003] The condensation reaction of aldehydes, ketones with alcohols is an important type of organic reaction, which is widely used in the synthesis of drugs, spices, and the protection of carbonyl groups in organic synthesis. This reaction is usually carried out under acid catalysis. In the presence of an acidic catalyst, aldehydes and ketones easily react with two molecules of alcohol to lose one molecule of water and obtain acetals and ketals. In the condensation reaction of benzaldehyde with methanol, the use of borate as a catalyst gives a yield of 60%. In addition, when using molecular sieves such as HZSM-5, HY or Y as catalysts, the condensation yields reach 90% and 83% respectively. Compared with liquid acid catalysts, solid acid catalysts have attracted the attention of researchers due to their easy preparation, easy recovery, and high catalytic efficiency. In the present invention, WO3 is used as the solid acid center and SiO2 is used as the carrier to prepare WO3 / SiO2 catalysts with different loadings for catalyzing the acetal reaction of benzaldehyde and methanol. The method of the present invention has the advantages of low raw material cost, mild reaction conditions, and high catalytic efficiency, and has good industrial application prospects. Summary of the Invention

[0004] Aiming at the above deficiencies existing in the prior art, the purpose of the present invention is to provide a method for preparing benzaldehyde dimethyl acetal by catalyzing benzaldehyde with a composite oxide. In this method, WO3 is prepared by hydrolyzing WCl6, and different WO3 / SiO2 with different acid strengths are obtained by controlling the calcination temperature. The condensation reaction of benzaldehyde and methanol is catalyzed by using this catalyst, and the reaction is carried out at room temperature. The carrier used in the present invention is SiO2 prepared from basic silica sol. The preparation method of the present invention is simple, and the catalyst carrier is inexpensive, which is beneficial to the industrial production of catalyst preparation.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A method for preparing dimethyl acetal of benzaldehyde by using a composite oxide as a catalyst, which uses benzaldehyde as a raw material, WO3 / SiO2 as a catalyst, and methanol as a solvent, and obtains dimethyl acetal of benzaldehyde through a catalytic reaction under normal temperature conditions.

[0007] Furthermore, the method for preparing dimethyl acetal of benzaldehyde by using the composite oxide as a catalyst includes the following steps:

[0008] (1) Weigh an appropriate amount of WCl6 and add it to a beaker, add water and stir until the turbid liquid completely changes from brown to green, that is, WO3 and HCl are generated;

[0009] (2) Add SiO2 in proportion and continue stirring. After stirring evenly, heat and stir to remove water, and finally transfer it to an oven for drying;

[0010] (3) Grind the dried catalyst crude product into powder, put it into a crucible, and calcine it in a muffle furnace to obtain the WO3 / SiO2 catalyst;

[0011] (4) Use the prepared WO3 / SiO2 to catalyze the condensation reaction of benzaldehyde and methanol.

[0012] Furthermore, in step (4), add the WO3 / SiO2 catalyst, methanol, and benzaldehyde in proportion in a container, react at 30-72 °C for 0.5-1 h, and then stop the reaction.

[0013] Furthermore, in step (4), the content of WO3 is 1%-20%.

[0014] Furthermore, in step (3), the calcination temperature of WO3 / SiO2 is 150-500 °C.

[0015] Furthermore, in step (4), the reaction temperature is 72 °C and the reaction time is 1 h.

[0016] Furthermore, in step (4), after the reaction is completed, add n-octane as an internal standard solution, and filter the reaction solution for gas chromatography analysis.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. Using the preparation method of the present invention, the conversion rate of benzaldehyde is 100%, and the selectivity of dimethyl acetal of benzaldehyde is 100%.

[0019] 2. Compared with the traditional method for preparing WO3 / SiO2 by calcining tungstate (such as the methods disclosed in patents with publication numbers CN10212587, CN101797503A, etc.), the WO3 / SiO2 prepared by the method of the present invention has a stronger acid strength.

[0020] 3. The preparation of WO3 from traditional calcined tungstate generally needs to be carried out under high temperature conditions. The hydrolysis reaction of the present invention can occur at a relatively low temperature, reducing energy consumption and the high-temperature resistance requirements for equipment. Description of the Drawings

[0021] Figure 1 XRD patterns of the products obtained in Examples 1-4;

[0022] Figure 2 XRD patterns of the products obtained in Examples 5-8. Detailed Embodiments

[0023] The method of the present invention will be described in detail below in conjunction with specific examples and the accompanying drawings.

[0024] Example 1

[0025] A method for preparing benzaldehyde dimethyl acetal by catalyzing benzaldehyde with a composite oxide, the steps are as follows:

[0026] 1) Weigh an appropriate amount of WCl6 and add it to a 250 ml beaker, add water and stir until the turbid liquid completely changes from brown to green, that is, WO3 and HCl are formed. Add SiO2 in proportion (the proportion of WO3 is 1%) and continue to stir for 4 h. After stirring evenly, heat and stir for 30 min to remove water, and finally transfer it to an oven for drying;

[0027] 2) Grind the dried catalyst crude product into powder, divide it into five equal parts on average, take one part each and place it on a crucible, and place it in a muffle furnace for roasting. After roasting at 150 °C for 2 h, the prepared 1%-WO3 / SiO2-150 is obtained;

[0028] 3) Add about 0.2 g of 1%-WO3 / SiO2-150 catalyst, 7.9 g of methanol, and 0.52 g of benzaldehyde to a 25 mL round-bottom flask, and react at 72 °C for 1 hour. The conversion rate of benzaldehyde is 58%, and the selectivity of benzaldehyde dimethyl acetal is 100%.

[0029] Example 2

[0030] A method for preparing benzaldehyde dimethyl acetal by catalyzing benzaldehyde with a composite oxide, the steps are as follows:

[0031] 1) Weigh an appropriate amount of WCl6 and add it to a 250 ml beaker, add water and stir until the turbid liquid completely changes from brown to green, that is, WO3 and HCl are formed. Add SiO2 in proportion (the proportion of WO3 is 5%) and continue to stir for 4 h. After stirring evenly, heat and stir for 30 min to remove water, and finally transfer it to an oven for drying;

[0032] 2) Grind the dried crude catalyst into powder, divide it into five equal parts on average, take one part each and place it on a crucible, then put it into a muffle furnace for roasting. After roasting at 150 °C for 2 h, the prepared 5%-WO3 / SiO2-150 is obtained;

[0033] 3) Add about 0.2 g of 5%-WO3 / SiO2-150 catalyst, 7.9 g of methanol, and 0.52 g of benzaldehyde into a 25 mL round-bottom flask, react at 72 °C for 1 hour, the conversion rate of benzaldehyde is 81%, and the selectivity of benzaldehyde dimethyl acetal is 100%.

[0034] Example 3

[0035] A method for preparing benzaldehyde dimethyl acetal by using a composite oxide to catalyze benzaldehyde, the steps are as follows:

[0036] 1) Weigh an appropriate amount of WCl6 and add it to a 250 ml beaker, add water and stir until the turbid liquid completely changes from brown to green, that is, WO3 and HCl are formed. Add SiO2 in proportion (the proportion of WO3 is 10%) and continue to stir for 4 h. After stirring evenly, heat and stir for 30 min to remove water, and finally transfer it to an oven for drying;

[0037] 2) Grind the dried crude catalyst into powder, divide it into five equal parts on average, take one part each and place it on a crucible, then put it into a muffle furnace for roasting. After roasting at 150 °C for 2 h, the prepared 10%-WO3 / SiO2-150 is obtained;

[0038] 3) Add about 0.2 g of 10%-WO3 / SiO2-150 catalyst, 7.9 g of methanol, and 0.52 g of benzaldehyde into a 25 mL round-bottom flask, react at 72 °C for 1 hour, the conversion rate of benzaldehyde is 76%, and the selectivity of benzaldehyde dimethyl acetal is 100%.

[0039] Example 4

[0040] A method for preparing benzaldehyde dimethyl acetal by using a composite oxide to catalyze benzaldehyde, the steps are as follows:

[0041] 1) Weigh an appropriate amount of WCl6 and add it to a 250 ml beaker, add water and stir until the turbid liquid completely changes from brown to green, that is, WO3 and HCl are formed. Add SiO2 in proportion (the proportion of WO3 is 20%) and continue to stir for 4 h. After stirring evenly, heat and stir for 30 min to remove water, and finally transfer it to an oven for drying;

[0042] 2) Grind the dried crude catalyst into powder, divide it into five equal parts on average, take one part each and place it on a crucible, then put it into a muffle furnace for roasting. After roasting at 150 °C for 2 h, the prepared 20%-WO3 / SiO2-150 is obtained;

[0043] 3) Add approximately 0.2 g of 20%-WO3 / SiO2-150 catalyst, 7.9 g of methanol, and 0.52 g of benzaldehyde into a 25 mL round-bottom flask, react at 72 °C for 1 hour, with a benzaldehyde conversion rate of 67% and a benzaldehyde dimethyl acetal selectivity of 100%.

[0044] Example 5

[0045] A method for preparing benzaldehyde dimethyl acetal by using a composite oxide to catalyze benzaldehyde, the steps are as follows:

[0046] 1) Weigh an appropriate amount of WCl6 and add it to a 250 ml beaker, add water and stir until the turbid liquid completely changes from brown to green, that is, WO3 and HCl are formed. Add SiO2 in proportion (WO3 accounts for 10%) and continue to stir for 4 h. After stirring evenly, heat and stir for 30 min to remove water, and finally transfer it to an oven for drying;

[0047] 2) Grind the dried catalyst crude product into powder, divide it into five equal parts on average, take one part each and place it on a crucible, and place it in a muffle furnace for roasting. After roasting at 300 °C for 2 h, the prepared 10%-WO3 / SiO2-300 is obtained;

[0048] 3) Add approximately 0.2 g of 10%-WO3 / SiO2-300 catalyst, 7.9 g of methanol, and 0.52 g of benzaldehyde into a 25 mL round-bottom flask, react at 72 °C for 1 hour, with a benzaldehyde conversion rate of 81% and a benzaldehyde dimethyl acetal selectivity of 100%.

[0049] Example 6

[0050] A method for preparing benzaldehyde dimethyl acetal by using a composite oxide to catalyze benzaldehyde, the steps are as follows:

[0051] 1) Weigh an appropriate amount of WCl6 and add it to a 250 ml beaker, add water and stir until the turbid liquid completely changes from brown to green, that is, WO3 and HCl are formed. Add SiO2 in proportion (WO3 accounts for 10%) and continue to stir for 4 h. After stirring evenly, heat and stir for 30 min to remove water, and finally transfer it to an oven for drying;

[0052] 2) Grind the dried catalyst crude product into powder, divide it into five equal parts on average, take one part each and place it on a crucible, and place it in a muffle furnace for roasting. After roasting at 350 °C for 2 h, the prepared 10%-WO3 / SiO2-350 is obtained;

[0053] 3) Add approximately 0.2 g of 10%-WO3 / SiO2-350 catalyst, 7.9 g of methanol, and 0.52 g of benzaldehyde into a 25 mL round-bottom flask, react at 72 °C for 1 hour, with a benzaldehyde conversion rate of 85% and a benzaldehyde dimethyl acetal selectivity of 100%.

[0054] Example 7

[0055] A method for preparing benzaldehyde dimethyl acetal by using a composite oxide to catalyze benzaldehyde comprises the following steps:

[0056] 1) Weigh an appropriate amount of WCl6 and add it to a 250 ml beaker. Add water and stir until the turbid liquid completely changes from brown to green, that is, WO3 and HCl are formed. Add SiO2 in proportion (the proportion of WO3 is 10%) and continue stirring for 4 h. After stirring evenly, heat and stir for 30 min to remove water, and finally transfer it to an oven for drying;

[0057] 2) Grind the dried catalyst crude product into powder, divide it into five equal parts on average, take one part each and place it on a crucible, and put it into a muffle furnace for roasting. After roasting at 450 °C for 2 h, the prepared 10%-WO3 / SiO2-450 is obtained;

[0058] 3) Add about 0.2 g of 10%-WO3 / SiO2-450 catalyst, 7.9 g of methanol, and 0.52 g of benzaldehyde to a 25 mL round-bottom flask, and react at 72 °C for 1 h. The conversion rate of benzaldehyde is 87%, and the selectivity of benzaldehyde dimethyl acetal is 100%.

[0059] Example 8

[0060] A method for preparing benzaldehyde dimethyl acetal by using a composite oxide to catalyze benzaldehyde comprises the following steps:

[0061] 1) Weigh an appropriate amount of WCl6 and add it to a 250 ml beaker. Add water and stir until the turbid liquid completely changes from brown to green, that is, WO3 and HCl are formed. Add SiO2 in proportion (the proportion of WO3 is 10%) and continue stirring for 4 h. After stirring evenly, heat and stir for 30 min to remove water, and finally transfer it to an oven for drying;

[0062] 2) Grind the dried catalyst crude product into powder, divide it into five equal parts on average, take one part each and place it on a crucible, and put it into a muffle furnace for roasting. After roasting at 500 °C for 2 h, the prepared 10%-WO3 / SiO2-500 is obtained;

[0063] 3) Add about 0.2 g of 10%-WO3 / SiO2-500 catalyst, 7.9 g of methanol, and 0.52 g of benzaldehyde to a 25 mL round-bottom flask, and react at 72 °C for 1 h. The conversion rate of benzaldehyde is 92%, and the selectivity of benzaldehyde dimethyl acetal is 100%.

[0064] Sample testing

[0065] XRD testing

[0066] Figure 1 XRD testing was carried out on the products prepared in Examples 1-4Figure 2 XRD tests were conducted on the products prepared in Examples 5-8. It can be seen from Figure 1 that when prepared at low temperature, the supported WO3 / SiO2 structure exhibits monoclinic WO3, where SiO2 exists in an amorphous form. It can be seen from Figure 2 that when the calcination temperature is higher than 300 °C, WO3 / SiO2 exists in a triclinic structure. Combining Figure 1 with the preparation of a 10% WO3 loading catalyst at 150 °C, as the preparation temperature increases, the crystal morphology changes from monoclinic to triclinic.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing benzaldehyde dimethyl acetal by catalyzing benzaldehyde with a composite oxide, characterized in that: Benzaldehyde is used as raw material, WO3 / SiO2 is used as catalyst and methanol is used as solvent, and benzaldehyde dimethyl acetal is obtained by catalytic reaction at room temperature.

2. The method for preparing benzaldehyde dimethyl acetal by using benzaldehyde catalyzed by the composite oxide according to claim 1, characterized in that: The following steps are involved: (1) Weigh an appropriate amount of WCl6 into a beaker, add water and stir until the turbid liquid changes from brown to green, thus generating WO3 and HCl; (2) Add SiO2 in proportion and continue stirring. After stirring evenly, heat and stir to remove water, and finally move to an oven for drying; (3) Grinding the dried catalyst crude product into powder, putting it into a crucible, and calcining it in a muffle furnace to obtain a WO3 / SiO2 catalyst; (4) The prepared WO3 / SiO2 is used to catalyze the condensation reaction of benzaldehyde and methanol.

3. The method for preparing benzaldehyde dimethyl acetal by using a composite oxide catalyzed by benzaldehyde according to claim 2, characterized in that: In step (4), WO3 / SiO2 catalyst, methanol and benzaldehyde are added into a container in proportion, and the reaction is stopped after reacting at 30-72°C for 0.5-1h.

4. The method for preparing benzaldehyde dimethyl acetal by using a composite oxide catalyzed by benzaldehyde according to claim 2, characterized in that: In step (4), the content of WO3 is 1% to 20%.

5. The method for preparing benzaldehyde dimethyl acetal by using a composite oxide catalyzed by benzaldehyde according to claim 2, characterized in that: In step (3), the calcination temperature of WO3 / SiO2 is 150-500°C.

6. The method for preparing benzaldehyde dimethyl acetal by using a composite oxide to catalyze benzaldehyde according to claim 3, characterized in that: In step (4), the reaction temperature is 72° C. and the reaction time is 1 h.

7. The method for preparing benzaldehyde dimethyl acetal by using benzaldehyde catalyzed by the composite oxide according to claim 2, characterized in that: In step (4), after the reaction is completed, n-octane is added as an internal standard solution, and the reaction solution is filtered and analyzed by gas chromatography.

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