Compared with the traditional treatment methods such as landfill and incineration, waste plastics pyrolysis technology can not only reduce the pollution of the environment during the plastic treatment, but also can reduce the waste plastics into fuels and chemicals, so as to effectively recover the waste resources. However, pyrolysis of waste plastics usually requires a high temperature, making the pyrolysis process waste recycling process becomes complicated. The advantages of pyrolysis waste plastics compared with other methods were analyzed and the mechanism of thermal degradation of plastics was systematically expounded. On the basis of comprehensive domestic and foreign research, two kinds of low temperature pyrolysis waste plastics are proposed: Catalytic pyrolysis and co-pyrolysis. The mechanism of catalytic pyrolysis and co-pyrolysis to reduce the degradation temperature of plastics was analyzed by using the free radical theory of plastic degradation.
The material has many advantages over the world (such as light, cheap, no rust, corrosion resistance, reusable, etc.) in the world has been widely used. The survey shows that since 1950, plastic consumption has increased at almost 10% per year. With the rapid development of China's economy, the per capita consumption of plastic has increased significantly. At present, China has become the world's largest consumer of plastics, plastic consumption of more than 60 million t, accounting for about 1/4 of the world's total consumption.
The growing use of plastic to people's lives to bring great convenience at the same time, also caused a lot of white pollution. In the ultraviolet light and combustion, the emission of CO, vinyl chloride monomer, HCl, methane, NOx, SO2, hydrocarbon, and the like, when the waste is bulky and bulky, is not easily decomposed after being discarded, causing the land to be knotted and hinder crop respiration and absorption. Class, aromatics, alkaline and oily sludge, dust and other pollution of water and air, chlorine plastic incineration release of dioxin and other harmful substances . Waste plastic processing is becoming more and more urgent and necessary. Recycling is the most fundamental way to solve the problem of waste plastics, which can use chemical pyrolysis can be converted into waste plastics and chemicals. Pyrolysis is an irreversible thermochemical reaction in the absence of oxygen or anoxic conditions. The pyrolysis of organic solid waste can ultimately produce combustible gas, pyrolysis of tar and coke. Studies have shown that waste plastics through the heat cracking can produce a large number of high calorific value of liquefied petroleum products and gas products . Due to the heat resistance of plastics, plastic pyrolysis usually requires very high temperatures (400 ° C). Sometimes in order to obtain high-yield chemical raw materials, pyrolysis temperature will be as high as 700 ~ 900 ℃ . At present, there are many studies on the pyrolysis of plastics at home and abroad, and the low temperature pyrolysis of waste plastics is rarely reported. The pyrolysis process of plastics is carried out under high temperature condition. The harsh reaction condition is an important reason why this technology can not be widely used. Therefore, it is very important to explore the method and mechanism of pyrolysis waste plastics under low temperature condition. In this paper, the mechanism of the thermal degradation of plastics was systematically analyzed. On this basis, the method and mechanism of pyrolysis of waste plastics were studied. The aim was to provide theoretical basis for pyrolysis of waste plastics under low temperature.