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In 1954, American Cyanamid Company developed the first legal sulfate production technology, the industrial production. Since then, acrylamide production process has undergone two changes: the mid-invented the copper-catalyzed hydration 1970s, mid-1980s to develop a microbial production process. Sulfuric acid hydration process is complex, copper-catalyzed hydration reaction due to addition contain small amounts of by-products; microbial production of monomers due to the impurity content of less activity, is particularly suitable for the production of ultra-high molecular weight polyacrylamide, and therefore subject to respected. In relation to the microbiological assay, a traditional method of legitimate legal and copper sulfate catalytic water.
Traditional methods sulfuric acid hydration prior acrylonitrile at below 100 ℃ hydrolysis into acrylamide sulfate, and was then acrylamide (AM). By the beginning of the acrylamide homo- prepared nonionic polyacrylamide, relatively simple products. Soon he developed a partially hydrolyzed with a base (after hydrolysis) of anionic polyacrylamide.
Legitimate use of copper water acrylonitrile in the presence of catalytic copper-based catalyst is prepared by the hydration reaction of acrylamide, which comprises the reaction system or a salt thereof having an active methylene group and an acidic group in one molecule appears and anionic acrylamide-containing solution with a weakly basic or a medially basic exchange resin. In the above hydration reaction, the formation of impurities is suppressed, and catalyst activity was not affected, resulting acrylamide can be used to produce a high molecular weight and a good water-soluble flocculants.
Copper-catalyzed hydration of acrylonitrile can also be handled by at least two purification steps, first the acrylonitrile and strong acid cation exchange resin, then or in contact with the activated carbon with a resin having a primary or secondary amino group of. The resulting final through hydration reaction of acrylonitrile in the presence of a copper catalyst. Even with the general quality of acrylonitrile, which is also capable of producing high-quality acrylamide, and to further develop the polyacrylamide has a good water-soluble.
Legal disadvantage is the need for copper-catalyzed water recycling acrylonitrile, and separation of copper, waste of resources and energy; and more side effects, is not easy to control, product purity is not high.
Microbial microbiological assay method acrylonitrile, water and immobilized biocatalysts formulated into hydration solution, after separating the spent catalyst catalytic reaction can be obtained acrylamide product. Compared with traditional copper legitimate catalytic water, its features are: reaction at normal temperature and pressure, the equipment is simple, safe operation; a high conversion per pass, without separation and recovery of unreacted acrylonitrile; specificity of the enzyme enables a high selectivity No side effects. When using J-1 strain, the reaction temperature is 5-15 ℃, PH value of 7-8, the reaction zone acrylonitrile concentration of 1% -2%. Acrylonitrile conversion was 99.99%, the selectivity of 99.98% acrylamide, an acrylamide reactor outlet concentration close to 50%; the amount of inactivated enzyme catalyst is discharged outside the system is less than 0.1% of the product; no copper separation section, without ion exchange processing, the separation and purification operation is greatly simplified; high product concentration, without mention rich operation, the whole process is simple, less investment in equipment, high economic efficiency, in favor of small-scale production.
Microbiological method has the following specific Technology:
(1) The application of membrane technology microbiological method. The method comprises the step of microbial cell culture, preparation of bacterial suspension weight, with a free microbial cells as biocatalyst carried hydration reaction of acrylonitrile, acrylamide separating the resulting reaction liquid hydration. Characterized in that the membrane was washed with a micro purification of bacterial fermentation broth to prepare a bacterial suspension weight, using an ultrafiltration membrane to separate the acrylamide hydration fluid and biological impurities. Production of acrylamide using the technology can significantly improve production efficiency and cell utilization while reducing biological impurities hydrating fluid product, good quality of acrylamide obtained high purity.
(2) Continuous catalytic microbes. The law produced by fermentation containing nitrile hydratase acid Corynebacterium or mutagenic cell lines, followed by a free cell method or immobilized cell method catalytic synthesis of acrylamide Acrylonitrile water, and then to give a high purity acrylamide.
(3) The use of a microbial catalyst washed by aqueous acrylic acid solution. The first method a microbial catalyst washed with an aqueous solution of acrylic acid and acrylamide prepared by the washed microbial catalyst for the conversion reaction.