Chemical reduction method
Researchers began to try to extract chemical components from plastics for reuse. The technological method adopted is to cut off the long chain of polymer and restore its original properties. The cracked raw materials can be used to make new plastics. Some methods promote the chemical cracking of bonded carbon atoms by adding chemical elements, or promote their thermal cracking by adding energy.
Bayer company in Germany developed a hydrolysis chemical reduction method to crack PUC sponge pad. Experiments show that the chemical reduction method is technically feasible, but it can only be used to treat plastic wastes generated in the manufacturing process of clean plastics, such as corner powder. However, plastics contaminated by other pollutants used in households are difficult to be treated by chemical decomposition. With the application of this reduction method, a large number of wastes will not be hydrolyzed until 2 1 century. Some new chemical decomposition methods are still in the process of research. Ford Motor Company of the United States is currently applying ester decomposition method to the treatment of automobile waste plastic parts.
Rensselaer Institute of Technology has developed a solution that can decompose plastic waste. This patented solution is to mix six different types of plastics and heat them together. Six polymers can be extracted at different temperatures. In the experiment, polystyrene plastic fragments and related solutions were mixed into a dissolved state at room temperature, then heated in a sealed container, and then sent to a low-pressure "flash chamber", and the solution quickly evaporated (recyclable), leaving reusable pure polystyrene.
It is said that the purification device used in the study can purify 1kg of polymer per hour. The New York State Government and Niagara Mohawk Power Company are planning to jointly establish a small-scale pilot plant. Investors claim that after the completion of the factory, 4t polymer raw materials can be recovered every hour. Its cost is only 30% of the production raw materials, and it has very obvious commercial value.
Hydrogenation precipitation method
Many experts believe that hydrogenation can be used to treat mixed plastic products. Raw materials such as synthetic crude oil and gas can be produced by putting the mixed plastic fragments into a hydrogen reactor and adding specific temperature and pressure. This treatment method can be used to treat PVC waste, and its advantage is that it will not produce toxic dioxins and chlorine. With this method, 60%-80% of the mixed plastic products can be refined into synthetic crude oil according to the different plastic components. Three chemical companies, such as BASF in Germany, pointed out in the same research report that hydrogenation is the best thermal cracking method, and the synthetic crude oil products obtained by decomposition are of good quality and can be used for refining.
The University of Kentucky in Lexington, USA, invented a technical method to turn waste plastics into high-quality plastic fuel oil. The fuel produced by this method is very similar to crude oil, even lighter than crude oil, and it is easier to be refined into high octane fuel oil. This kind of fuel oil produced from waste plastics contains no sulfur and few impurities. Plastics and coal liquefy in a similar way. But also can produce high-quality fuel oil.
The researchers mixed all kinds of plastics with zeolite catalyst and tetralin in a bath, then put them into a reactor called "pipeline bomb" and heated them under pressure with hydrogen to promote the decomposition of macromolecular plastics into compounds with smaller molecular weight. This process is similar to combination in crude oil processing. After this treatment, the oil yield of waste plastics is very high, and the oil yield of polyethylene plastic bottles can reach 88%. When waste plastics and coal are mixed and liquefied at the ratio of about 1: 1, better fuel oil can be obtained. After evaluating the economic benefits of this process, it is predicted that the fuel oil produced from waste plastics will be transformed into blast furnace benefits within 5- 10 years. At present, Germany has started to build a reactor in Botup that is expected to produce 200 tons of plastic fuel per day.