Current situation and progress of the hottest viny

2022-08-18
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The present situation and progress of vinyl acetate technology

vinyl acetate is widely used in the production of polyvinyl acetate, polyvinyl alcohol, coating, slurry, adhesive, vinylon, film, vinyl copolymer resin, acetal resin, etc

at present, there are two production processes of vinyl acetate: ethylene process and acetylene process. Among them, ethylene method is dominant because of its good technology and economy. The United States completed the conversion from acetylene method to ethylene method in the 1970s. Acetylene method includes liquid phase method and gas phase method. The liquid phase method has been eliminated. The gas phase method uses calcium carbide acetylene and acetic acid as raw materials, which are desulfurized and dephosphorized, zinc acetate activated carbon as catalyst, and bismuth hypocarbonate as cocatalyst. The reaction temperature is 170 ~ 200 ℃, and the pressure is atmospheric pressure. Acetylene method has been gradually replaced by ethylene method due to the high cost of raw materials, but it still occupies an important position in China

the catalysts of ethylene gas phase process are mainly supported catalysts of PD an, PD Pt and PD CD, and the supports are mainly silica gel and alumina. The two main factors affecting the catalyst are the coordination ability of PD and the ability of acetic acid or acetate to oxidize PD. In the finished products of vinyl acetate produced by ethylene method and acetylene method, the content of vinyl acetate is more than 99.5%, and the impurities are slightly different. The content of aldehydes in vinyl acetate by acetylene method is much higher than that by ethylene method. Although the absolute content of these aldehydes is not much, they have a great impact on the polymerization reaction. Therefore, for vinyl acetate with vinylon as the final product, the quality of ethylene method is better than that of acetylene method

although the technology of ethylene to vinyl acetate is much better than that of acetylene, and the catalyst of ethylene method is also constantly improved, with the selectivity and yield continuously improved, there are still many insurmountable shortcomings in the use of fixed bed technology, so scientists later developed a new method of fluidized bed vinyl acetate

in 1998, foreign enterprises announced a new process for preparing vinyl acetate by gas phase in ethylene fluidized bed. The newly designed fluidized bed reactor system and catalyst are used in this process. The most fundamental and effective way to make the device is to let the waste materials degrade and disappear after entering the seawater. The investment cost is reduced. The product yield is 99% based on acetic acid and 92% - 94% based on ethylene, which is significantly higher than the fixed bed technology

compared with ABS, PLA and nylon, three kinds of fixed bed plastics, which will continue to occupy the largest share of the 3D printing material market in the next 10 years, the advantage of using fluidized bed process to produce vinyl acetate is that the catalyst is continuously and evenly mixed in the reactor, which can significantly improve the uniform addition of cocatalyst and keep the cocatalyst concentration unchanged; The operation of the fluidized bed can continuously remove the deactivated catalyst and replace it with a new catalyst; The fluidized bed is operated in an isothermal environment, and further leveling and compaction of the land inside the plant is being carried out to minimize the deactivation of the catalyst caused by overheating. Foreign companies try to adopt the vinyl acetate production technology that acetic acid will affect the service life of the device as the only raw material. In the three-step liquid-phase reaction process, acetic acid is first cracked to produce vinyl ketone, vinyl ketone is hydrogenated to acetaldehyde, and then acetaldehyde reacts with the added vinyl ketone to produce vinyl acetate. It is said that the yield of vinyl acetate monomer prepared by this method is as high as 95%

the production of vinyl acetate in China began in the 1960s. Beijing organic chemical plant first introduced acetylene fluidized bed technology from Japan. Since then, Shanghai Petrochemical Complex and Sichuan Vinylon plant have introduced ethylene process and natural gas acetylene process units. At present, China has 17 sets of vinyl acetate production units, with an annual capacity of nearly 800000 tons. It is estimated that the demand for vinyl acetate in China in 2005 and 2010 will be 840000 tons and 1million tons respectively

based on the digestion and absorption of imported technology, China's vinyl acetate production has made many significant progress. CT series catalysts developed by Shanghai Petrochemical Research Institute and Shanghai Petrochemical General Plant have been used in the imported unit, and the production capacity of the unit has been increased by 10%. At present, the science and technology development company of Shanghai Petrochemical Co., Ltd. is conducting a single tube test of ctv- Ⅲ ethylene vinyl acetate catalyst. In addition, acetylene catalyst has been replaced by activated carbon carrier with coconut shell by bituminous coal, and has been applied in industry

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