阅读说明：本技术 一种香兰素的连续制备工艺 (Continuous preparation process of vanillin ) 是由 陈清 周军学 汤建刚 黎信业 于 2020-12-08 设计创作，主要内容包括：本发明涉及一种香兰素的连续制备工艺,包括如下步骤：S1、在混合反应釜中配制由4-甲基愈创木酚、亚硝基二甲基苯胺的原料液,在混合反应釜中补充催化剂；所述催化剂为以Pd纳米粒子负载在多孔碳材料上；S2、将步骤S1混合物移动至反应器,同时通过高压氧气管向反应器输入高压氧气,与步骤S1混合物在0.3-0.5MPa,100-120℃下进行催化氧化反应4-8小时；S3、将步骤S2产物输送到超临界流体萃取设备中中对产物进行萃取,萃取出的液相经即为得到的香兰素,对萃取后的滤液进行过滤,同时通过分离罐对气液进行分离,过滤出的催化剂回收至用至步骤S1中,过滤出的气体回收至储罐中。本发明采用的催化剂具有选择性好、产率高的优点。(The invention relates to a continuous preparation process of vanillin, which comprises the following steps: s1, preparing a raw material liquid of 4-methyl guaiacol and nitrosodimethylaniline in a mixing reaction kettle, and supplementing a catalyst in the mixing reaction kettle; the catalyst is prepared by loading Pd nanoparticles on a porous carbon material; s2, moving the mixture obtained in the step S1 to a reactor, simultaneously inputting high-pressure oxygen to the reactor through a high-pressure oxygen pipe, and carrying out catalytic oxidation reaction on the mixture obtained in the step S1 at the temperature of 100-120 ℃ under the pressure of 0.3-0.5MPa for 4-8 hours; s3, conveying the product obtained in the step S2 to supercritical fluid extraction equipment to extract the product, obtaining vanillin from the extracted liquid phase, filtering the extracted filtrate, separating gas and liquid through a separation tank, recycling the filtered catalyst to the step S1, and recycling the filtered gas to a storage tank. The catalyst adopted by the invention has the advantages of good selectivity and high yield.)

1. A continuous preparation process of vanillin is characterized by comprising the following steps:

s1, preparing a raw material liquid of 4-methyl guaiacol and nitrosodimethylaniline in a mixing reaction kettle, and supplementing a catalyst in the mixing reaction kettle;

the catalyst is prepared by loading Pd nanoparticles on a porous carbon material;

s2, moving the mixture obtained in the step S1 to a reactor, simultaneously inputting high-pressure oxygen to the reactor through a high-pressure oxygen pipe, and carrying out catalytic oxidation reaction on the mixture obtained in the step S1 at the temperature of 100-120 ℃ under the pressure of 0.3-0.5MPa for 4-8 hours;

s3, conveying the product obtained in the step S2 to supercritical fluid extraction equipment to extract the product, obtaining vanillin from the extracted liquid phase, filtering the extracted filtrate, separating gas and liquid through a separation tank, recycling the filtered catalyst to the step S1, and recycling the filtered gas to a storage tank.

2. The continuous process of claim 1, wherein: the particle size of the Pd nano particles is 4-7 nm.

3. The continuous process of claim 2, wherein: the porous carbon material is any one of carbon fiber and activated carbon.

4. The continuous process of claim 3, wherein: the mass ratio of the Pd nanoparticles to the porous carbon material is 1:10:1: 1;

the continuous process of claim 1, wherein: according to the weight fraction, the 4-methyl guaiacol is 60-70 parts, the nitrosodimethylaniline is 30-50 parts, and the catalyst is 1-2 parts respectively.

5. The continuous process of claim 1, wherein: the preparation method of the nitrosodimethylaniline comprises the following steps:

mixing hydrochloric acid and water, adding the mixture into a mixing reaction kettle, cooling to about 8 ℃, continuously dropwise adding dimethylaniline until the temperature is not more than 25 ℃, then continuously stirring for 10min, cooling to 8 ℃, dropwise adding 25% sodium nitrite aqueous solution, continuously stirring for 30 min at the temperature of 8 ℃, filtering to obtain p-nitrosodimethylaniline hydrochloride, and then adding a certain amount of ethanol and concentrated hydrochloric acid to obtain the p-nitrosodimethylaniline.

6. The continuous vanillin preparation process of claim 1, wherein the catalyst is prepared by the following steps:

(a) the Pd salt solution was mixed with 5 mL of concentrated hydrochloric acid, cooled in an ice bath, and then 50mL of 40% C was added₂H₄Adding acid-washed porous carbon material into the O solution, and mechanically stirring for 30-60 minutes;

(b) adding 50 g of KOH solution dissolved in 50mL of water, keeping the temperature below 50 ℃, raising the temperature to 60 ℃ after the addition, keeping the temperature for 30 min, washing and cleaning the catalyst with water for multiple times, and then filtering and pouring out the water;

(c) and (c) washing the product obtained in the step (b) with glacial acetic acid, performing suction filtration, washing and filtering for multiple times with water, and drying at the temperature of 100 ℃ to obtain the catalyst.

7. The continuous process of claim 7, wherein: the Pd salt solution is a palladium chloride solution, wherein the palladium chloride solution is formed by mixing 8.25 g of palladium chloride and 50ml of water; the mass of the porous carbon material is 4.94-49.4 g.

Technical Field

The invention relates to the field of organic synthesis, in particular to a production process and reaction equipment for synthesizing vanillin by methyl guaiacol.

Background

Vanillin is commonly known as vanilla powder, vanillin, Yunnan powder, vanilla essence, and vanillin. Is extracted from Vanilla planifolia of Rutaceae. White to yellowish crystalline or crystalline powder, slightly sweet. It is soluble in hot water, glycerol and alcohol, and is not easily dissolved in cold water and vegetable oil. The fragrance is stable and is not easy to volatilize at higher temperature. It is easy to oxidize in air and is easy to change color when it is exposed to alkaline substances. The 3-methoxy-4-hydroxybenzaldehyde has a chemical name of 3-methoxy-4-hydroxybenzaldehyde, has vanilla bean fragrance and strong milk fragrance, plays roles in enhancing and fixing fragrance, is widely applied to industries such as cosmetics, tobacco, cakes, candies, baked foods and the like, is one of synthetic spice varieties with the largest global yield, and has a history of more than 100 years for industrial production of vanillin. The recommended amount of vanillin in the final flavored food is about 0.2 to 20000 mg/kg. According to the regulations of the Ministry of health in China, vanillin can be used in large infants, infant formula foods and infant cereal foods (except infant formula cereal powder), and the maximum using amount is 5mg/ml and 7mg/100g respectively. Vanillin can also be used as plant growth promoter, bactericide, lubricant defoamer, and is also an important intermediate for synthesizing medicaments and other spices. Besides, it can be used as glazing agent in electroplating industry, ripener in agriculture, deodorant in rubber products, anti-hardening agent in plastic products and medical intermediate, etc. and is widely used.

The existing preparation process of vanillin adopts 2-methoxy-4-methylphenol to prepare vanillin, the process is not complex, but the yield is low, three wastes are more, 20 tons of water are required to be used for producing one ton of vanillin, and the requirement of process production cannot be met.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide a production process and a method for preparing vanillin.

The technical scheme of the invention is as follows:

a continuous preparation process of vanillin is characterized by comprising the following steps:

s1, preparing a raw material liquid of 4-methyl guaiacol and nitrosodimethylaniline in a mixing reaction kettle, and supplementing a catalyst in the mixing reaction kettle;

the catalyst is prepared by loading Pd nanoparticles on a porous carbon material;

s2, moving the mixture obtained in the step S1 to a reactor, simultaneously inputting high-pressure oxygen to the reactor through a high-pressure oxygen pipe, and carrying out catalytic oxidation reaction on the mixture obtained in the step S1 at the temperature of 100-120 ℃ under the pressure of 0.3-0.5MPa for 4-8 hours;

s3, conveying the product obtained in the step S2 to supercritical fluid extraction equipment to extract the product, obtaining vanillin from the extracted liquid phase, filtering the extracted filtrate, separating gas and liquid through a separation tank, recycling the filtered catalyst to the step S1, and recycling the filtered gas to a storage tank.

Further, the particle size of the Pd nano-particles is 4-7 nm.

Further, the porous carbon material is any one of carbon fiber and activated carbon.

Further, the mass ratio of the Pd nanoparticles to the porous carbon material is 1:10:1: 1;

furthermore, according to the weight fraction, the 4-methyl guaiacol is 60-70 parts, the nitrosodimethylaniline is 30-50 parts, and the catalyst is 1-2 parts respectively.

Further, the preparation method of the nitrosodimethylaniline comprises the following steps:

mixing hydrochloric acid and water, adding the mixture into a mixing reaction kettle, cooling to about 8 ℃, continuously dropwise adding dimethylaniline until the temperature is not more than 25 ℃, then continuously stirring for 10min, cooling to 8 ℃, dropwise adding 25% sodium nitrite aqueous solution, continuously stirring for 30 min at the temperature of 8 ℃, filtering to obtain p-nitrosodimethylaniline hydrochloride, and then adding a certain amount of ethanol and concentrated hydrochloric acid to obtain the p-nitrosodimethylaniline. A

Further, the preparation method of the catalyst comprises the following steps:

(a) mixing the Pd salt solution with 5 mL of concentrated hydrochloric acid, cooling under the ice bath condition, then adding 50mL of 40% C2H4O solution, adding the acid-washed porous carbon material, and mechanically stirring for 30-60 minutes;

(b) adding 50 g of KOH solution dissolved in 50mL of water, keeping the temperature below 50 ℃, raising the temperature to 60 ℃ after the addition, keeping the temperature for 30 min, washing and cleaning the catalyst with water for multiple times, and then filtering and pouring out the water;

(c) and (c) washing the product obtained in the step (b) with glacial acetic acid, performing suction filtration, washing and filtering for multiple times with water, and drying at the temperature of 100 ℃ to obtain the catalyst.

Further, the Pd salt solution is a palladium chloride solution, wherein the palladium chloride solution is formed by mixing 8.25 g of palladium chloride and 50ml of water; the mass of the porous carbon material is 4.94-49.4 g.

By the scheme, the invention at least has the following advantages:

(1) the catalyst adopted by the invention has the advantages of good selectivity and high yield, and the Pd atoms with low coordination numbers on the steps and the vertex angle sites of the Pd nanoparticles in the catalyst prepared by the invention are mainly responsible for the adsorption and activation of vanillyl alcohol molecules and can inhibit the deep oxidation of vanillin.

(2) The method adopts the supercritical carbon dioxide fluid for extraction, not only can realize the continuous separation and circulation of the catalyst, but also can improve the purity of the vanillin.

The foregoing is a summary of the present invention, and in order to provide a clear understanding of the technical means of the present invention and to be implemented in accordance with the present specification, the following is a detailed description of the preferred embodiments of the present invention.

Detailed Description

The following examples are included to further illustrate the embodiments of the present invention. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Example 1

Preparation of the catalyst:

the palladium chloride solution (8.25)g of palladium chloride mixed with 50mL of water) and 5 mL of concentrated hydrochloric acid (36%), cooled in an ice bath, 50mL of 40% C are then added₂H₄Adding acid-washed porous carbon material 4.94g g into the O solution, and mechanically stirring for 30 minutes;

adding 50 g KOH solution dissolved in 50mL water, keeping the temperature below 50 ℃, raising the temperature to 60 ℃ after the addition, keeping the temperature for 30 min, washing and cleaning the catalyst with water for multiple times, and then filtering and pouring out the water;

washing the product with glacial acetic acid, suction filtering, washing with water for several times, filtering, and drying at 100 deg.C to obtain the catalyst.

Preparation of nitrosodimethylaniline:

mixing hydrochloric acid (15%) and water, adding the mixture into a mixing reaction kettle, cooling to about 8 ℃, continuously dropwise adding dimethylaniline at the temperature of not more than 25 ℃, then continuously stirring for 10min, cooling to 8 ℃, dropwise adding 25% sodium nitrite aqueous solution, continuously stirring for 30 min at the temperature of 8 ℃, filtering out p-nitrosodimethylaniline hydrochloride, and then adding a certain amount of ethanol and concentrated hydrochloric acid to obtain the p-nitrosodimethylaniline.

Continuous preparation of vanillin:

preparing a raw material solution consisting of 60 parts of 4-methyl guaiacol and 30 parts of nitrosodimethylaniline in a mixing reaction kettle, and supplementing 1 part of catalyst in the mixing reaction kettle;

moving the mixture to a reactor, simultaneously inputting high-pressure oxygen to the reactor through a high-pressure oxygen pipe, and carrying out catalytic oxidation reaction on the mixture and the previous mixture for 4 hours at the temperature of 100 ℃ under the pressure of 0.3 MPa;

and (3) conveying the product into supercritical fluid extraction equipment to extract the product, obtaining vanillin by passing an extracted liquid phase, filtering the extracted filtrate, simultaneously separating gas and liquid by a separation tank, recovering the filtered catalyst to the previous step, and recovering the filtered gas to a storage tank.

Tests show that the conversion rate of the 4-methyl guaiacol is 96 percent, and the selectivity of the vanillin is 99 percent.

Example 2

Preparation of the catalyst:

a palladium chloride solution (8.25 g of palladium chloride mixed with 50mL of water) was mixed with 5 mL of concentrated hydrochloric acid (36%), cooled in an ice bath, and 50mL of 40% C was added₂H₄Adding acid-washed porous carbon material 25g g into the O solution, and mechanically stirring for 45 minutes;

adding 50 g KOH solution dissolved in 50mL water, keeping the temperature below 50 ℃, raising the temperature to 60 ℃ after the addition, keeping the temperature for 30 min, washing and cleaning the catalyst with water for multiple times, and then filtering and pouring out the water;

washing the product with glacial acetic acid, suction filtering, washing with water for several times, filtering, and drying at 100 deg.C to obtain the catalyst.

Preparation of nitrosodimethylaniline:

mixing hydrochloric acid (15%) and water, adding the mixture into a mixing reaction kettle, cooling to about 8 ℃, continuously dropwise adding dimethylaniline at the temperature of not more than 25 ℃, then continuously stirring for 10min, cooling to 8 ℃, dropwise adding 25% sodium nitrite aqueous solution, continuously stirring for 30 min at the temperature of 8 ℃, filtering out p-nitrosodimethylaniline hydrochloride, and then adding a certain amount of ethanol and concentrated hydrochloric acid to obtain the p-nitrosodimethylaniline.

Continuous preparation of vanillin:

preparing a raw material solution consisting of 65 parts of 4-methyl guaiacol and 40 parts of nitrosodimethylaniline in a mixing reaction kettle, and supplementing 1.5 parts of a catalyst in the mixing reaction kettle;

moving the mixture to a reactor, simultaneously inputting high-pressure oxygen to the reactor through a high-pressure oxygen pipe, and carrying out catalytic oxidation reaction on the mixture and the previous mixture for 6 hours at the temperature of 110 ℃ under the pressure of 0.4 MPa;

and (3) conveying the product into supercritical fluid extraction equipment to extract the product, obtaining vanillin by passing an extracted liquid phase, filtering the extracted filtrate, simultaneously separating gas and liquid by a separation tank, recovering the filtered catalyst to the previous step, and recovering the filtered gas to a storage tank.

The test shows that the conversion rate of the 4-methyl guaiacol is 97 percent, and the selectivity of the vanillin is 98 percent.

Example 3

Preparation of the catalyst:

a palladium chloride solution (8.25 g of palladium chloride mixed with 50mL of water) was mixed with 5 mL of concentrated hydrochloric acid (36%), cooled in an ice bath, and 50mL of 40% C was added₂H₄Adding acid-washed porous carbon material 49.4g g into the O solution, and mechanically stirring for 60 minutes;

adding 50 g KOH solution dissolved in 50mL water, keeping the temperature below 50 ℃, raising the temperature to 60 ℃ after the addition, keeping the temperature for 30 min, washing and cleaning the catalyst with water for multiple times, and then filtering and pouring out the water;

washing the product with glacial acetic acid, suction filtering, washing with water for several times, filtering, and drying at 100 deg.C to obtain the catalyst.

Preparation of nitrosodimethylaniline:

mixing hydrochloric acid (15%) and water, adding the mixture into a mixing reaction kettle, cooling to about 8 ℃, continuously dropwise adding dimethylaniline at the temperature of not more than 25 ℃, then continuously stirring for 10min, cooling to 8 ℃, dropwise adding 25% sodium nitrite aqueous solution, continuously stirring for 30 min at the temperature of 8 ℃, filtering out p-nitrosodimethylaniline hydrochloride, and then adding a certain amount of ethanol and concentrated hydrochloric acid to obtain the p-nitrosodimethylaniline.

Continuous preparation of vanillin:

preparing a raw material solution consisting of 70 parts of 4-methyl guaiacol and 50 parts of nitrosodimethylaniline in a mixing reaction kettle, and supplementing 2 parts of a catalyst in the mixing reaction kettle;

moving the mixture to a reactor, simultaneously inputting high-pressure oxygen to the reactor through a high-pressure oxygen pipe, and carrying out catalytic oxidation reaction on the mixture and the previous mixture for 8 hours at the temperature of 120 ℃ under the pressure of 0.5 MPa;

and (3) conveying the product into supercritical fluid extraction equipment to extract the product, obtaining vanillin by passing an extracted liquid phase, filtering the extracted filtrate, simultaneously separating gas and liquid by a separation tank, recovering the filtered catalyst to the previous step, and recovering the filtered gas to a storage tank.

The test shows that the conversion rate of the 4-methyl guaiacol is 94 percent, and the selectivity of the vanillin is 96 percent.

Comparative example 1

Comparative example 1 differs from example 1 in that no catalyst was added.

The test shows that the conversion rate of the 4-methyl guaiacol is 64 percent, and the selectivity of the vanillin is 65 percent.

Comparative example 2

Comparative example 2 differs from example 1 in that supercritical fluid extraction is not performed.

The test shows that the conversion rate of the 4-methyl guaiacol is 94 percent, and the selectivity of the vanillin is 65 percent.

The working principle of the chemical reaction of the invention is as follows:

the invention has at least the following advantages:

(1) the catalyst adopted by the invention has the advantages of good selectivity and high yield, and the Pd atoms with low coordination numbers on the steps and the vertex angle sites of the Pd nanoparticles in the catalyst prepared by the invention are mainly responsible for the adsorption and activation of vanillyl alcohol molecules and can inhibit the deep oxidation of vanillin.

(2) The method adopts the supercritical carbon dioxide fluid for extraction, not only can realize the continuous separation and circulation of the catalyst, but also can improve the purity of the vanillin.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.