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the method of making acrylamide
Acrylamide as a commodity has two forms: water solution and crystal, the crystal colorless and transparent, the boiling point of 125 DEG C, the melting point of 84~85 Deg. C, soluble in water, alcohol, ether, acetone, chloroform, insoluble in benzene and heptane. It is stable at room temperature, but when the temperature above the melting point, oxidation conditions are, in the role of ultraviolet light, easy to produce polymerization reaction. When heated and dissolved, the release of a strong corrosive gas and nitrogen oxides.
Acrylamide is a kind of unsaturated amides, extensively used to manufacture water-soluble polymer polyacrylamide copolymer --; a small amount for the hydrophilic center make dear oily polymer forming permeable, in order to increase the adhesive force, improve and solvent resistance softening point; and a small part is used as a crosslinking agent of vinyl polymers.
Production method of Acrylamide
Production technology in 1954, American Cyanamid Company developed the first sulfuric acid hydration production technology, realize industrialization production. Since then, acrylamide production process has experienced two changes: in twentieth Century 70 time metaphase invented the copper catalytic hydration, the middle of the 80's developed a production process of microbial method. Sulfuric acid hydration process of complex, copper catalytic hydration for addition reaction of monomers containing a small amount of by-product; microbial method for low impurity content, high activity, particularly suitable for the production of ultra high molecular weight polyacrylamide, so admired. With respect to the microbial method, hydration and copper sulfate catalytic hydration belongs to traditional method.
The 2.1 traditional methods of sulfate method acrylonitrile to 100 DEG C hydrolysis into acrylamide sulfate, neutralization to acrylamide (AM). The early by acrylamide homopolymer prepared non-ionic polyacrylamide, single product. Soon developed by alkaline partial hydrolysis (after hydrolysis method) of anionic polyacrylamide.
Copper catalytic hydration of acrylonitrile in the presence of copper based catalyst by hydration reaction for the preparation of acrylamide, the method comprises that compounds with active methylene groups and acid groups in a molecule or its salt in the reaction system, and then make the containing acrylamide solution and weakly or moderately alkaline anion exchange resin contact. In the hydration reaction, the generation of impurities is suppressed, and the catalyst activity is not affected by any effect, income of acrylamide can be used for the manufacture of high molecular weight and good water soluble flocculant.
Copper catalyzed hydration of acrylonitrile can also be through at least two purification steps to deal with, first of all to acrylonitrile contact with strong acidic cation exchange resin, and then with the resin has a primary or secondary amino group or contact with active carbon. Finally, in the presence of a copper based catalyst acrylonitrile obtained after hydration reaction. Even with acrylonitrile general quality, this method can produce high-quality acrylamide, and can be further produced with good water soluble polyacrylamide.
Copper catalytic hydration disadvantage is the need for recovery of acrylonitrile and separation of copper, the waste of resources and energy; at the same time more side effects, not easy to control, the product purity is not high.
2.2 microbiological method microbiological method acrylonitrile and water and immobilized biocatalyst prepared into aqueous solution, in the catalytic reaction and separating waste catalyst can be obtained with acrylamide. Compared with the traditional copper catalyzed water legitimate, its characteristic is: under normal temperature and normal pressure reaction, simple equipment, safe operation; high conversion per pass, without separation and recovery of the unreacted acrylonitrile; specific properties of the enzymes to make selective high, no side reaction. Using the J-1 strain, the reaction temperature of 5-15 DEG C, the pH value is 7-8, the reaction zone of acrylonitrile concentration was 1%-2%. Acrylonitrile conversion rate of 99.99%, acrylamide selectivity is 99.98%, the reactor outlet acrylamide concentration close to 50%; the loss of enzyme catalyst discharged outside the system is less than 0.1% of the product; without copper separation section, without ion exchange processing, make the separation and purification of operation greatly simplified; high product concentration, without concentration operation the entire process, simple operation, less equipment investment, production and high economic benefit, for small scale production.
Microbial method has the following several concrete technology:
(1) the microbiological method of the application of membrane separation technology. The method includes the step with acrylamide hydration liquid microbial cultivation, mushroom weight suspension was prepared, using free cells as biological catalyst of acrylonitrile hydration reaction, separating the reaction proceeds. It is characterized by microfiltration membrane to washing and purifying the broth to prepare bacteria weight suspension with ultra filtration membrane to separate the acrylamide hydration liquid and biological impurities. Using the technology of production of acrylamide can obviously improve the production efficiency and biomass utilization, and the impurity content of hydrated products in biological fluid decreases, get good quality, high purity acrylamide.
(2) Microbial Continuous Catalytic method. The method of production by fermentation containing a nitrile hydratase propionic acid Corynebacterium or its mutant cells, and then use the method of free cells or immobilized cells by catalytic synthesis of acrylamide acrylonitrile water, then processing, obtained high purity acrylamide.
(3) by using a microbial catalyst washed with aqueous acrylic acid solution. This method first uses the aqueous acrylic acid solution washing microbial catalyst, and then washing by microbial catalyst for conversion reaction to prepare the acrylamide.