CN1172904C

CN1172904C - Process for preparing phenylacetamide

Info

Publication number: CN1172904C
Application number: CNB011268018A
Authority: CN
Inventors: 谌文�; 谌文燊
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-09-18
Filing date: 2001-09-18
Publication date: 2004-10-27
Anticipated expiration: 2021-09-18
Also published as: CN1342644A

Abstract

The present invention relates to a production method of phenylacetamide. The present invention is characterized in that on the basis of the prior producing route, an optimal preparation method is preferably selected to increase the yield and quality of phenylacetamide. In the method disclosed by the present invention, phenylacetamide is produced by using styrene, the optimal material feeding molar ratio of styrene to sulfur is 1:1.9 to 2.0, and the amount of liquid ammonia is measured by 24% of the volume of aqueous solution which can completely dissolve hydrogen sulfide converted from sulfur used as feeding material. The present invention has the advantages of high overall yield up to more than 95%, high purity up to 99% and safe operation, and is suitable for large industrial production.

Description

Process for producing acetamide

Technical Field

The invention relates to the field of chemical synthesis, in particular to a production method of acetamide.

Background

Acetamide is widelyused as a solvent in industry, can be used as a solubilizer for substances with low water solubility when dissolved in water, and has wide application in the paper industry, the pharmaceutical industry, the printing and dyeing industry and the like.

Acetamide is usually prepared by introducing ammonia into acetic acid at high temperature, and the yield can reach 85%.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for preparing acetamide with high yield and good purity by using ethylene as a raw material.

The preparation method of acetamide disclosed by the invention comprises the following steps:

the materials are put into a reaction kettle according to the mol ratio of 1: 2 of ethylene to sulfur, water and ammonia are added, the dosage of the water is calculated by the volume of the materials which can be completely dissolved after the sulfur is completely converted into hydrogen sulfide, and the dosage of the ammonia is calculated by 24 percent of the volume of the water. At a temperature of 160 ℃ and a pressure of 35kg/m²Reacting under the condition, filtering, distilling (bp 221.2 ℃), decoloring and crystallizing after the reaction is finished.

The saturation degree of the hydrogen sulfide in water is 8 percent.

The method for preparing acetamide has the advantages of yield of more than 90 percent and purity of more than 99 percent.

The reaction equation for preparing acetamide by the invention is as follows:

(I)

(II)

as can be seen from the reaction formulas (I) and (II), the amounts of sulfur and ammonia used as catalysts play a key role in the whole reaction, and for producing a high-yield and high-purity product, the hydrogen sulfide released in the reaction must be immediately converted into ammonium sulfide. To achieve this, a large excess of liquid ammonia is required, while taking into account the relationship between the saturation concentration of hydrogen sulfide converted to ammonium sulfide in the reaction and the production volume, only to bring the reaction to completion. If the concentration of the liquid ammonia is too low, the hydrogen sulfide released by the reaction is difficult to immediately convert into ammonium sulfide, so that the reaction speed is delayed, and the influence of side reaction is generated; if the liquid ammonia concentration is too high, the reaction cannot be carried out for the desired purpose without taking into account that the hydrogen sulfide saturation is compatible with the production volume. Assuming that all the hydrogen sulfide evolved from the reaction is converted to ammonium sulfide in half and the remaining half of the hydrogen sulfide remains in the autoclave, the over-concentrated hydrogen sulfide can react with the nascent acetamide:

(III)

the "sulfur" evolved again leads to the following reaction:

(VI)

the ammonium polysulfides have a certain oxidizing action, and thecircuitous interference of these side reactions prevents the reaction from proceeding smoothly.

In addition, the gaseous state of the hydrogen sulfide in the autoclave brings the influence of difficult control on the temperature and the pressure, the hydrogen sulfide is likely to explode due to slight negligence, and the hydrogen sulfide poisoning accident can also happen due to insufficient ventilation during discharging.

The saturation concentration in the aqueous hydrogen sulfide solution is 8%, and if it exceeds this concentration, the hydrogen sulfide produced by the reaction will not be converted into ammonium sulfide, thereby interfering with the reaction.

Therefore, according to the influence factors, the invention greatly increases the use amount of liquid ammonia and water, ensures the concentration of ammonia to be 24 percent, and ensures that the generated H is as much as possible₂S is converted into ammonium sulfide, so that smooth reaction is ensured.

The total yield of the acetamide prepared according to the proportion of the invention can reach more than 90 percent, the purity can reach 99 percent, and the invention has the following advantages:

1. enough surplus liquid ammonia is available, so that the hydrogen sulfide generated by the reaction is immediately converted into ammonium sulfide;

2. the saturated concentration of the ammonium sulfide is just met in the high-pressure kettle;

3. free hydrogen sulfide is not available, so the temperature and the pressure are easy to control and are not threatened by explosion and poisoning of the hydrogen sulfide.

4. The reaction tends to be complete, and the yield and the quality of the product can be improved;

on the basis of the invention,the temperature and the pressure can be properly increased, and the reaction time can be shortened.

The preparation method of acetamide disclosed by the invention has the advantages of high yield, good quality, safe operation and suitability for large-scale industrial production.

Detailed Description

In a 1300 liter autoclave, the input quantities are 26.6kg of ethylene and 60.8kg of sulphur, the volume of aqueous solution calculated to be totally converted into hydrogen sulphide and soluble is 808L, and the quantity of liquid ammonia is about 182.4kg of 24% of this volume [ volume of water: (60.8/32 × 34) ÷ 8% ═ 808L, ammonia dosage: 808X 24% ═ 182.4kg]The reaction concentration is 160 ℃, and the pressure is 3.43X 10⁶Pa reaction, the final acetamide yield is 99%, and the purity is 99%.

Claims

1. A process for preparing acetamide features that the ethylene is high-pressure reacted in the presence of sulfur and liquid ammonia to obtain acetamide.

2. A process for the production of acetamide according to claim 1 wherein the molar ratios of the feeds are: the ratio of ethylene to sulfur is 1: 2.0, and the dosage of liquid ammonia is 24% of the volume of the water solution which can be completely dissolved after the sulfur is completely converted into hydrogen sulfide.