CN1396148A

CN1396148A - Process for preparing 2-butenoic acid industrially by oxygen oxidizing method

Info

Publication number: CN1396148A
Application number: CN 02129053
Authority: CN
Inventors: 刘秉奇
Original assignee: JIEXIN CHEMICAL INDUSTRY Co Ltd TIANJIN
Current assignee: JIEXIN CHEMICAL INDUSTRY Co Ltd TIANJIN
Priority date: 2002-08-30
Filing date: 2002-08-30
Publication date: 2003-02-12
Anticipated expiration: 2022-08-30
Also published as: CN1161315C

Abstract

A process for preparing 2-butanois acid by oxygen oxidizing includes such steps as adding 2-butenal, water and n-hexane to a reactor, filling compressed air and then adding oxygen, oxidizing reaction at 18-24 deg.C and under 0.34-0.52 MPa, vacuum distillation to obtain the aqueous solution of 2-butenoic acid, adding activated carbon, decolouring, filtering, cooling-crystallizing, filtering, adding water, crystallizing again, filtering and baking. Its advantages are simple equipment and no waste gas exhaust.

Description

Method for industrially preparing 2-butenoic acid by oxygen oxidation method

Technical Field

The invention relates to a method for preparing 2-butenoic acid by an oxidation method.

Background

The preparation of 2-butenoic acid (commonly known as crotonic acid) by oxidation of 2-butenal (commonly known as crotonaldehyde) is the current method for large-scale preparation of 2-butenoic acid. The basic reaction principle is as follows:

in the course of the reaction, 2-butenal is oxidized to give a peroxy 2-butenoic acid intermediate, which then gives 2-butenoic acid.

The 2-position of the product has unsaturated double bonds, and acetic acid and formic acid byproducts can be generated during deep oxidation, so that the yield of the product is influenced.

Based on the above-mentioned reaction principles, a great deal of work has been done by many skilled workers on the mode of selective oxidation of 2-butenal, for example Shawinigan in Brit Patent 595170 discloses a process for preparing 2-butenoic acid by bubbling air through aqueous 2-butenal in the presence of a catalyst of copper acetate, cobalt acetate and a diluent; richard M Watson in US Patent 2945058 describes the use of aqueous 2-butenal as starting material, eliminating the catalyst air oxidation process by adding a diluent, followed by Albert Bouniot et al in US Patent 3579575 to improve the process.

In the method of the invention, since air is used for oxidation in the reaction, when oxygen molecules in the air are utilized, a large amount of inert gas generated in the reaction carries part of the material to be continuously discharged out of the reaction system in the reaction process, so that a large amount of material is lost, and the air is easily polluted, so that a device for collecting and treating the material in the tail gas is arranged.

In the above invention, the post-reaction treatment method is to obtain the final product by organic solvent extraction or reduced pressure distillation, and a large amount of solvent is consumed or a vacuum pressure reduction device is required.

Disclosure of Invention

The invention aims to provide a method for industrially preparing 2-butenoic acid by an oxygen oxidation method, which overcomes the defects of the background technology to the maximum extent by improving the background technology.

The basic technical solution of the invention is as follows: adding 2-butenal, water and n-hexane into a reaction tank, injecting compressed air, and maintaining the pressure in the reaction tank at 0.34-0.52MPa/cm²And carrying out oxidation reaction at the temperature of 18-24 ℃, and then carrying out post-treatment process to obtain a crude product. In the oxidation reaction, when the tank pressure is reduced and constant, oxygen is supplied to the reaction tank to maintain the oxidation reaction at an oxygen content of 6Obtaining an oxidation reaction solution under a condition of-10%. And discharging residual gas in the tank after the reaction is finished. The gas contains only a very small amount of 2-butenal material, thus avoiding a large loss of material.

Adding a certain amount of water into a distillation tank filled with the oxidation reaction liquid, wherein the adding amount of water can be 500-600 liters, performing azeotropic distillation on the 2-butenal and the water to evaporate unreacted 2-butenal under reduced pressure, the evaporation amount is about 80 percent of the input amount, recovering the 2-butenal in a layered manner for reuse, and the rest in the tank is the 2-butenoic acid aqueous solution. Adding 1-2 kg of active carbon into the 2-butenoic acid aqueous solution for decolorization and filtration. Cooling and crystallizing the filtrate, filtering to obtain a crude product of the 2-butenoic acid, adding 2-2.5 times of water into the crude product, heating at 50-70 ℃ for 15 minutes, cooling to 0-5 ℃ for recrystallization, filtering and drying to obtain a finished product, wherein the yield is over 80 percent (based on the consumed 2-butenal), and the appearance of the product is white crystals with the content of over 99 percent.

In the circulating state of the reaction liquid, when compressed air is introduced into the reaction tank in order to accelerate the reaction rate, the tank pressure is preferably set to 0.47MPa/cm²Closing the air inlet valve, consuming oxygen in the air along with the reaction, and reducing the tank pressure when the tank pressure is constant at 0.47Mpa/cm²In this case, the remaining gas in the tank is inert gas. Then supplementing oxygen to the gas to make the oxygen content in the tank reachAbout 18-20 percent, and obtaining oxidation reaction liquid after the reaction is finished. In the reaction process, the reaction temperature is controlled to be in a range of 18-24 ℃ in general, and the closed state is subjected to intermittent oxidation, so that the waste gas emission in the reaction process is completely avoided, and the loss of materials is avoided.

The material adding proportion is that when 2-butenal is one part, the adding amount of water in the oxidation reaction is 0.13 part, and the adding amount of normal hexane is 0.3-0.5 part (the weight ratio). According to the dissolution concentration of water in the 2-butenal, when the 2-butenal, the water and a diluent n-hexane are added, the water content is controlled to be 11.6 percent. The 2-butenal containing water is oxidized without causing the aggregation of peroxide, and the hydrophilic radical of the peroxide is decomposed in water phase without affecting the double bond oxidation of hydrophobic radical olefin for selective oxidation. The existence of the diluent n-hexane can disperse the reaction heat conduction, and is favorable for preventing the polymerization of the unsaturated 2-butenal. The amount of the diluent to be added may be 0.3 to 0.5 times (by weight) the amount of the 2-butenal.

Aiming at the defects of the prior documents, the invention adopts oxygen oxidation to avoid the emission of waste gas of a reaction system, thereby reducing the investment of production equipment and cutting off a tail gas absorption tower and a recycling device sprayed by a solvent.

The product post-treatment adopts water as a solvent, and adopts a recrystallization method to replace a reduced pressure distillation method in the original document, and devices such as organic solvent extraction, reduced pressure distillation and the like in the original document are removed.

The oxidation reaction equipment is a stainless steel reaction tank capable of bearing reaction pressure, a liquid circulating pump provided with a gas-liquid mixer, a compressed air and oxygen inlet pipe, and a gas outlet pipe connected with the gas mixer. The reaction tank replaces a reaction tower in the background technology, so that the reaction equipment is simpler, and batch production can be realized.

The various manufacturing machines or equipment used in the present invention and the various chemical materials thereof can be commercially available and known techniques.

Detailed Description

Example 1:

600 kg of 2-butenal and 79 kg of water are put into a 2000L reaction tank,and 180 kg of n-hexane. Starting a circulating pump to circulate the materials, and controlling the temperature of the materials to be 20 ℃. Compressed air is introduced once to 0.35Mpa/cm². After the reaction, the pressure is gradually reduced and air is supplemented until the pressure is stabilized at 0.315-0.32Mpa/cm². Then introducing industrial oxygen and keeping the pressure at 0.34-0.345Mpa/cm²Controlling the reaction temperature to be 18-20 ℃, stopping introducing oxygen when the reaction consumes about 27 kg of oxygen, reacting for 0.5 hour to obtain oxidation reaction liquid, and transferring the feed liquid into a distillation retort.

Slowly heating the feed liquid in a distillation tank, distilling to recover n-hexane, adding 300L water when the temperature in the tank reaches 70 deg.C, and distilling under reduced pressure to obtain vacuum degree of 0.08Mpa/cm²Distilled to obtain 300When the mixed liquid of the 2-butenal and the water is increased, 300 liters of water is added, and the reduced pressure distillation is continued until the distillate does not contain the 2-butenal, and the distillation is stopped. Adding 2 kg of active carbon, decoloring for 15 minutes, filtering, cooling to 0-5 ℃, crystallizing, and filtering to obtain about 130 kg of finished product 2-butenoic acid crude product. Adding water 2 times the weight of the crude product into the crude product, heating to 50 ℃ for 15 minutes, cooling to 0-5 ℃ after the crude product is dissolved, recrystallizing, filtering to obtain 108 kg of finished product 2-butenoic acid, drying and granulating. The finished product is obtained in a yield of 81.31% (based on 2-butenal consumed).

Distilling the mixture of 2-butenal and water under reduced pressure, and separating the water layer to obtain the upper layer liquid of 2-butenal which can be recovered for reuse. Example two:

600 kg of 2-butenal, 79 kg ofwater and 300 kg of n-hexane are put into a 2000-liter reaction tank. Starting a circulating pump to circulate the materials, and controlling the temperature of the materials to be 20 ℃. Introducing compressed air once to make the pressure in the tank be 0.55Mpa/cm². The reaction started and the pressure dropped gradually. Then supplementing air until the pressure is stabilized at 0.47Mpa/cm². Then introducing oxygen, and keeping the pressure at 0.5-0.52Mpa/cm²And controlling the reaction temperature to be 19-21 ℃, stopping introducing oxygen when the reaction consumes about 28 kg of oxygen, reacting for 0.5 hour, and stopping the reaction to obtain an oxidation reaction solution. The post-treatment was the same as in example one. The finished product is white crystal, 108 kg of finished product is obtained, the content is more than 99 percent, and the yield is 81.40 percent (calculated by the consumed 2-butenal).

Claims

1. A method for industrially preparing 2-butenoic acid by oxygen oxidation comprises adding 2-butenal, water and n-hexane into a reaction tank, injecting compressed air, and maintaining the pressure in the reaction tank at 0.34-0.52Mpa/cm²Oxidizing at 18-24 deg.C, post-treating to obtain crude product ①, adding oxygen into the reactor when the pressure in the reactor is constant and reduced, and maintaining at 0.34-0.52Mpa/cm²Oxidizing reaction while keeping oxygen content at 6-10% to obtain oxidized liquid, ② adding the crude product in post-treatmentAdding 2-2.5 times of water for recrystallization, filtering and drying to obtain the finished product.

2. The method for industrially preparing 2-butenoic acid by the oxygen oxidation method according to claim 1, wherein the oxidation reaction temperature is controlled to be 19 to 21 ℃ until the reaction conversion rate reaches about 18 to 20% to obtain an oxidation reaction solution.

3. The method for industrially producing 2-butenoic acid by oxygen oxidation according to claim 1, wherein water is added to the crude product at ② in an amount of 2 to 2.5 times the weight of the crude product, and the mixture is heated at 50 to 70 ℃ for 15 minutes and then cooled to 0 to 5 ℃ for recrystallization.