Polyacrylamide is an organic polymer, which is widely used in oil exploitation, Water Treatment Chemicals, mineral processing, Oilfield Chemicals，paper making and other fields. Polyacrylamide is formed by polymerization of acrylamide monomer. Therefore, the importance of acrylamide production in the polyacrylamide production process is self-evident.
Polyacrylamide monomer acrylamide production technology, no matter which production method, their raw materials are acrylonitrile, hydrated under the action of the catalyst to produce the crude product of acrylamide monomer, refined acrylamide monomer, the monomer is the raw material for the production of polyacrylamide. The reaction process is roughly as follows:
Acrylonitrile +(water catalyst/water) → Compound → crude acrylamide → refined acrylamide
According to the type of reaction catalyst and development history, the production technology of acrylamide monomer can be divided into two categories: chemical method and biological method:
First, chemical production technology can be divided into two generations according to the stage
The first generation of chemical method adopts sulfuric acid catalytic hydration technology. The disadvantages of this technology are low conversion rate of acrylonitrile, low yield of acrylamide products and low by-products, which brings great burden to refining. In addition, due to the strong corrosion of catalyst sulfuric acid, the equipment cost is high and the production cost is increased.
The second generation production technology of chemical method is binary or ternary skeleton copper catalytic production technology. The disadvantage of this technology is that in the process of chemical production of acrylamide, there is an exchange process of copper ions, so the final product introduces metal copper ions that affect polymerization, thereby increasing the cost of post-treatment and refining.
Second, the production technology of microbial acrylamide
Microbial method uses biological enzyme as catalyst, the acrylonitrile, water and biocatalyzer are prepared into a hydrated solution, and the waste catalyst can be separated after the catalytic reaction to obtain acrylamide products. Compared with copper catalyzed water method, it is characterized by: acrylonitrile one-way conversion rate is very high, a paper introduced in 12 years is 99.99%: there is no need to separate and recover unreacted acrylonitrile: the specific properties of the enzyme make the selectivity extremely high, 99.98%, no side reaction. And because there is no ion exchange treatment and no copper separation section, the separation and refining operation is greatly simplified. The product obtained by the biological method has a high concentration and no concentration operation is required, which is especially suitable for the production of high viscosity and ultra-high relative molecular weight polypropionamide.
So far, the microbiological method has developed the following three specific process technologies:
(1) Microbiological method of applying membrane technology:
The processes involved include microbial culture and preparation of bacterial weight suspension. Acrylonitrile hydration reaction was carried out with free bacteria as biocatalyster and the acrylamide hydration solution was separated. It is characterized by the use of microfiltration membrane to wash and purify the bacteria in the fermentation liquid to prepare the bacteria weight suspension, and the use of ultrafiltration membrane to separate the acrylamide hydration liquid and biological impurities. The production efficiency and utilization rate of bacteria can be significantly improved by this process, and the content of biological impurities in the hydrated product can be reduced. The acrylamide obtained has good quality and high purity.
(2) Microbial continuous catalysis method:
Corynebacterium propionate or its mutagenic cells containing nitrile hydratase were produced by fermentation, then acrylonitrile water was catalyzed to synthesize acrylamide by free cell method or immobilized cell method, and then high purity acrylamide was obtained by treatment.
(3) The use of microbial catalysts washed in acrylic water solution:
Acrylamide is prepared by washing the microbial catalyst with acrylic water solution, and then the washed microbial catalyst is used in the conversion reaction.
Foreign microbiological technology was first developed by Japan's Nitto Company. The company built a 4000t/a microbial enyl rubber production plant in Yokohama, Japan, in 1984, and increased the production capacity of the plant to 20,000 t/a in 1992. Nitto microbial process production of acrylamide technology is still based on acrylonitrile as raw material, hydration reaction is carried out in a multistage continuous advector reactor, and the reactant is directly separated and filtered by foam to obtain 50% of the acrylamide monomer solution. The advanced nature of the technology is shown in the good selectivity of nitrile hydratase catalyst, high yield, and less impurities in the product. The by-product is less, the reaction is carried out at normal temperature and pressure, and the section of product concentration and acrylonitrile recovery are omitted, so that the process is simplified. Because the biological method of producing acrylamide monomer has so many advantages, in the 1990s, Japan and Russia quickly established 10,000-ton microbial catalytic acrylamide devices.
China is the third country in the world to have this technology after Japan and Russia. The nitrile hydratase, codenamed Norcardia-163, obtained from seed culture during the three Five-Year Plan period, is now in production in several regions with high quality and has reached the quality index of ultra-high molecular weight polyacrylamide. It indicates that China's microbial catalytic acrylamide technology has reached the international advanced level.
Henan Hongze Environmental Protection Technology Co., Ltd