At present, the production methods of itaconic acid are synthesis and fermentation, and the synthesis method is divided into citric acid synthesis and maleic anhydride synthesis. Citric acid synthesis method has high cost and is not suitable for industrialization; Maleic anhydride synthesis method has the advantages of low production cost and high selectivity, but it has not been industrialized; The fermentation method is widely used in industrial production at home and abroad because of its readily available raw materials and mature technology.
(1) citric acid synthesis method: the concentrated citric acid aqueous solution is heated to 280-300℃ under reduced pressure (3O-40 mmHg), which can be decomposed into itaconic anhydride and citraconic acid, and then itaconic acid is separated and extracted from it. The application of this method is limited because of its high production cost.
(2) Formation of maleic anhydride: Maleic anhydride reacts with yeast, and the formed ester reacts with HX, then with formaldehyde, and then hydrolyzed to obtain itaconic acid. This method has mild reaction conditions, high homogeneous catalytic activity and strong selectivity, and has reached the level of industrial application. Moreover, the raw materials are abundant and easily available, the production cost is low, and the three wastes are few. It is expected to be a new method for the production of itaconic acid.
(3) Fermentation method: sugar is used as fermentation raw material, nitrogen source and inorganic salt are added, Aspergillus vomitus is used as strain, and fermentation is carried out at appropriate temperature. Because of its simple production process and low cost, most domestic and foreign manufacturers use this method for production at present. The key of fermentation method is the selection of fermentation raw materials, the selection and cultivation of strains and the separation of products (including plate and frame filtration, ion exchange, concentration, crystallization, centrifugation and drying).
At present, the research on the synthesis of itaconic acid from petrochemical products is being carried out at home and abroad, and some achievements have been made. Dalian Institute of Chemistry of Chinese Academy of Sciences cooperated with Dalian University of Technology, and after three years of research, a new process for synthesizing itaconic acid from petrochemical products was determined. In this process, maleic anhydride was used as the main raw material, and itaconic acid was obtained through four steps of esterification, addition, methylene and hydrolysis.
Maleic diester can also be used as raw material, so esterification can be omitted. If itaconic acid diester is sold and applied as a product, hydrolysis can be omitted. In this way, the formation route is simplified to two key reactions: addition and methylation, which can be combined into one step. This route has the following advantages: ① Rich in raw materials. There are more than 20 maleic anhydride production plants in China, with an annual production capacity of about 40,000 t. After the newly-built maleic anhydride plants in Tianjin Zhonghe, Liaoning Panjin and Jinxi are put into operation, the production capacity will reach about 80,000 t. The supply of maleic anhydride in the market exceeds demand, and the raw materials are sufficient. ② The selectivity of itaconic acid was significantly improved. So far, many technical routes reported in the literature with petrochemical products as raw materials have the same shortcomings, that is, the selectivity is low, only about 30%, which is at a disadvantage in the competition with fermentation method and difficult to industrialize. Therefore, the key to the new synthetic route proposed by Dalian Institute of Chemistry and Dalian University of Technology is to improve the selectivity of itaconic acid. They adopted the following technical measures: (a) The direct reaction between maleic anhydride and formaldehyde was changed into a two-step reaction, and the addition reagent I-IX containing active hydrogen was introduced, which was first added with maleic anhydride diester and then reacted with formaldehyde for methylene. HX is a compound containing heteroatoms, which can be turned into by-products. (b) changing heterogeneous catalysis into homogeneous catalysis with high selectivity. (c) The change of gas into solid should be a liquid phase reaction. (d) The high-temperature pressurized reaction at 300 ~ 500℃ was changed to normal temperature and pressure reaction, and the high-temperature side reaction was avoided due to mild reaction conditions.
The preliminary test results of Dalian Institute of Chemistry and Dalian University of Technology show that the selectivity of itaconic acid is more than doubled than that reported in patent literature by taking the above measures, and it can become a new route of itaconic acid with certain competitiveness, but it has not yet been industrialized. In recent years, the relevant scientific research institutes are further developing and researching the new technology of itaconic acid production, and have made progress.
The research on itaconic acid in China started earlier, but the progress is slow. Breakthrough has been made in recent years, and trial production has been carried out in Yunnan and Sichuan. Shandong Food Fermentation Industry Research and Design Institute used corn starch as raw material to produce itaconic acid by submerged fermentation. After several years' efforts, the mutant strain A.terreus) HA6080 was screened out through small-scale, pilot-scale and industrial production tests, with stable performance, high acid production rate and conversion rate, reaching above 6.0-7.0% and 60% respectively, and less miscellaneous acid production. The project won the first prize of Shandong Science and Technology Progress from 65438 to 0999, and the second prize of National Science and Technology Progress in 2000.
The industrially developed itaconic acid products have been tested by China Shanghai Polymer Materials Testing Center and foreign customers such as Japan and South Korea, and are superior to domestic similar products in appearance and internal quality. The main technical indicators are higher than the standards of the United States and Japan, and the product quality has been highly praised by users at home and abroad, and gained a good reputation among users in the United States, Australia, India, Japan and Taiwan Province Province.