CN117800830A - A method for synthesizing acetic acid by oxidation of isopropanol - Google Patents

Abstract

A method for synthesizing acetic acid by oxidation of isopropanol belongs to the technical field of organic synthesis and can solve the shortcomings of the current synthesis of acetic acid, such as harsh reaction conditions, cumbersome catalyst preparation, and difficult separation. The invention uses ozone as an oxidant, acetonitrile as a solvent, and does not add any catalyst or additive to oxidize isopropanol to prepare acetic acid under normal pressure. The method has the advantages of high efficiency, environmental protection, high conversion rate, simple process, etc.

Description

A method for oxidizing isopropyl alcohol to synthesize acetic acid

Technical field

The invention belongs to the technical field of organic synthesis, and specifically relates to a method for oxidizing isopropyl alcohol to synthesize acetic acid.

Background technique

Acetic acid, also known as acetic acid, is a widely used bulk chemical product and organic acid. It is mainly used to produce important chemical products such as vinyl acetate, terephthalic acid, acetic anhydride and acetate ester. Mordenite ( MOR) molecular sieve catalyzes the reaction of gas-phase carbonylation of methanol to produce acetic acid, which promotes the non-noble metal-free halogen-free addition of gas-phase methanol carbonylation to produce acetic acid. Compared with the traditional methanol liquid-phase carbonylation route, the green synthesis of acetic acid from synthesis gas is environmentally friendly. , low cost and other advantages. Ni (NI Y M. CatalSci Technol, 2017, 7(20): 4818-4822) investigated the effect of n(CO)/n(CH ₃ OH) on the carbonylation reaction of methanol. When n(CO)/n(CH When ₃ OH) decreases from 80 to 20, the acetic acid selectivity decreases from 93.8% to 60.3%. At the same time, the effect of temperature on the carbonylation performance of methanol was also investigated, and it was found that the reaction temperature was 565 K as the optimal reaction temperature. Therefore, the route to produce acetic acid using synthesis gas as raw material has the advantages of wide source of raw materials and environmental friendliness, which shows great advantages in acetic acid synthesis research. However, this process still has low acetic acid yield, harsh reaction conditions, and volatile catalysts. issues such as living.

Patent CN202211017531.2 provides a method for regulating the carbonylation of methanol to prepare acetic acid, by regulating one or more of the rhodium concentration, lithium iodide concentration and flash temperature to regulate the acetic acid yield. However, the reaction conditions of this method are harsh and must be carried out under high temperature and high pressure conditions. Patent US 3769329 discloses a method for preparing acetic acid by carbonylation of methanol in a homogeneous catalyst body using a rhodium-based catalyst and methyl iodide as a promoter. The reaction system contains a large amount of water, which increases the reaction rate but increases the cost of product purification. Patent CN201810078381.3 reports an ethanol synthesis acetic acid catalyst and preparation method and acetic acid preparation method. Carbon nanotubes are pretreated to obtain hydrogen peroxide-treated carbon nanotubes, under the catalytic action of H ₂ PdCl ₆ and PdCl ₂ Prepare acetic acid.

In view of the current problems of complicated synthesis process steps, harsh reaction conditions, and the need to consider the stability, cost, preparation, and recovery of catalysts in the synthesis of acetic acid, it is important to develop a new way to synthesize acetic acid with mild reaction conditions, simple processes, and no catalysis. significance. Isopropyl alcohol has wide sources and is cheap, and ozone has strong oxidizing properties. The present invention innovatively proposes to apply ozone to isopropyl alcohol to prepare acetic acid. This method has potential industrial application value.

Contents of the invention

The invention aims at the disadvantages of the current synthesis of acetic acid, such as harsh reaction conditions, complicated catalyst preparation and difficult separation, and provides a method for synthesizing acetic acid by oxidation of isopropanol. The preparation method has the advantages of no catalysis, high reaction yield, mild process conditions and high atom economy.

The present invention adopts the following technical solutions:

A method for oxidizing isopropyl alcohol to synthesize acetic acid, including the following steps:

In the first step, add isopropyl alcohol and reaction solvent into the reaction bottle in sequence;

In the second step, adjust the pressure reducing valve of the oxygen cylinder and set the partial pressure to 0.1 MPa. After oxygen enters the ozone generator, ozone mixed gas is generated. Set the gas flow rate to 200 L/h. The ozone mixed gas enters the reaction bottle and reacts with it. react with substances to control the gas phase concentration of ozone to 220 mg/L;

The third step is to introduce the ozone mixed gas into the reaction bottle, and set the reaction liquid temperature to 35-45°C and the reaction time to 180 min;

The fourth step is to add a saturated sodium thiosulfate solution to the reaction solution after the reaction is completed, extract and separate to obtain an organic phase, remove the reaction solvent by vacuum distillation, and then separate by distillation to obtain the product acetic acid.

Furthermore, the amount of isopropanol used in the first step is 10-50 mL.

Further, the reaction solvent in the first step includes N,N-dimethylformamide or acetonitrile.

Further, the volume ratio of isopropyl alcohol to solvent described in the first step is 1:100~1:50.

The beneficial effects of the present invention are as follows:

The present invention uses isopropyl alcohol as a reactant and ozone as an oxidant without adding any catalyst. Under normal pressure conditions, isopropyl alcohol is prepared to obtain acetic acid with a high conversion rate. The method has the advantages of simple process, mild reaction conditions, and high product yield. High efficiency and other advantages.

Description of drawings

Figure 1 is an equation for synthesizing acetic acid by ozone oxidation of isopropyl alcohol according to the present invention;

Figure 2 is an EPR spectrum of superoxide radicals captured during the reaction process of the present invention;

Figure 3 is a possible reaction process of synthesizing acetic acid by ozone oxidation of isopropyl alcohol according to the present invention.

Detailed ways

A method for oxidizing isopropyl alcohol to synthesize acetic acid, including the following steps:

In the first step, add isopropyl alcohol (10~50mL) and reaction solvent into the reaction bottle in sequence;

In the second step, adjust the pressure reducing valve of the oxygen cylinder and set the partial pressure to 0.1 MPa. After oxygen enters the ozone generator, ozone mixed gas is generated. Set the gas flow rate to 200 L/h. The ozone mixed gas enters the reaction bottle and reacts with it. react with substances to control the gas phase concentration of ozone to 220 mg/L;

In the third step, pass the ozone mixed gas into the reaction bottle, set the reaction liquid temperature to 35~45°C, and the reaction time to 180 minutes;

In the fourth step, after the reaction is completed, add saturated sodium thiosulfate solution to the reaction solution, extract and separate to obtain the organic phase, remove the reaction solvent by distillation under reduced pressure, and then separate by distillation to obtain the product acetic acid.

Example 1

Weigh 30 mL of isopropyl alcohol and 3000 mL of acetonitrile and place them in a reaction bottle. After reacting for 180 minutes at a reaction temperature of 45°C, add saturated sodium thiosulfate solution to the reaction solution, extract and separate to obtain the organic phase. After pressure distillation, the reaction solvent is removed, and the product acetic acid is obtained by distillation separation, and acetic acid is obtained with a yield of 80%.

Example 2

Weigh 50 mL isopropyl alcohol and 2500 mL N,N-dimethylformamide and place them in a reaction bottle. After reacting for 180 minutes at a reaction temperature of 35°C, add saturated sodium thiosulfate solution to the reaction solution and extract. The organic phase was separated, and the reaction solvent was removed by distillation under reduced pressure. The product acetic acid was then separated by distillation, and acetic acid was obtained with a yield of 70%.

Example 3

Weigh 20 mL of isopropyl alcohol and 2000 mL of acetonitrile and place them in a reaction bottle. After reacting for 180 minutes at a reaction temperature of 40°C, add saturated sodium thiosulfate solution to the reaction solution, extract and separate to obtain the organic phase. After pressure distillation, the reaction solvent was removed, and the product acetic acid was obtained by distillation separation, and acetic acid was obtained with a yield of 82%.

Example 4

Weigh 10 mL isopropyl alcohol and 1000 mL N,N-dimethylformamide and place them in a reaction bottle. After reacting for 180 minutes at a reaction temperature of 45°C, add saturated sodium thiosulfate solution to the reaction solution and extract. The organic phase was separated, and the reaction solvent was removed by distillation under reduced pressure. The product acetic acid was then separated by distillation, and acetic acid was obtained with a yield of 90%.

Example 5

Weigh 10 mL of isopropyl alcohol and 500 mL of N,N-dimethylformamide and place them in a reaction bottle. After reacting for 180 minutes at a reaction temperature of 40°C, add saturated sodium thiosulfate solution to the reaction solution and extract. The organic phase was separated, and the reaction solvent was removed by distillation under reduced pressure. The product acetic acid was then separated by distillation, and acetic acid was obtained with a yield of 78%.

Description of Figure 2 and conclusions that can be drawn from Figure 2: The reaction process of ozone oxidation of isopropyl alcohol to synthesize acetic acid belongs to a free radical chain reaction. This method has the advantages of mild process conditions, efficient reaction, simple post-processing, and environmental protection and greenness. ,have a broad vision of application.

Claims (4)

1. A method for synthesizing acetic acid by oxidizing isopropanol is characterized by comprising the following steps: the method comprises the following steps:

firstly, sequentially adding isopropanol and a reaction solvent into a reaction bottle;

step two, regulating a pressure reducing valve of an oxygen steel bottle, setting the partial pressure to be 0.1 MPa, generating ozone mixed gas after oxygen enters an ozone generator, setting the gas flow to be 200L/h, enabling the ozone mixed gas to enter a reaction bottle to react with reactants, and controlling the gas phase concentration of ozone to be 220 mg/L;

thirdly, introducing ozone mixed gas into a reaction bottle, setting the temperature of a reaction liquid to be 35-45 ℃ and the reaction time to be 180 min;

and fourthly, after the reaction is finished, adding a saturated sodium thiosulfate solution into the reaction liquid, extracting and separating to obtain an organic phase, removing a reaction solvent after reduced pressure distillation, and separating by distillation to obtain the product acetic acid.

2. The method for synthesizing acetic acid by oxidizing isopropyl alcohol according to claim 1, wherein: the amount of isopropanol used in the first step is 10-50 mL.

3. The method for synthesizing acetic acid by oxidizing isopropyl alcohol according to claim 1, wherein: the reaction solvent in the first step comprises N, N-dimethylformamide or acetonitrile.

4. The method for synthesizing acetic acid by oxidizing isopropyl alcohol according to claim 1, wherein: in the first step, the volume ratio of the isopropanol to the solvent is 1:100-1:50.