Chinese scientists have learned to convert plastic into diesel

Recycle this package, please

Plastic is both a curse and a blessing to our entire civilization. On the one hand, without plastics of various types, humanity would have developed quite differently. The invention of plastics at one time allowed to significantly accelerate technological progress. On the other hand, plastic gradually litters our planet. This is especially true for polyethylene - it is not easy to recycle it, and a large amount of plastic film and products are simply thrown away. And then - plastic gets into the seas and oceans, forms giant garbage islands, breaks food chains in ecosystems of various types.

How can this problem be solved? At first glance, the solution lies on the surface: we collect plastic products, send for recycling (remelting), create new products. But the devil, as they say, is in the details. In order to recycle plastic using the proposed method, you need to collect plastic waste made from the same type of plastic. For example, only transparent plastic PET bottles. And even in this case, it is necessary to make significant efforts - to wash the bottles to such an extent that the final melt has the minimum amount of impurities. This is possible, but not too practical and quite expensive. Another method is the processing of plastics without oxygen access under high pressure and a temperature of about 500 ° C. As a result, we obtain a number of monomers, including styrene, terephthalic acid, methyl methacrylate . In modern conditions, only a small fraction of plastics is recycled, the rest is simply thrown away. Not very practical. What to do?

Recently, Chinese scientists from the Shanghai Institute of Organic Chemistry, led by Xiaongkhin Jia (Xiangqing Jia) have proposed a new type of processing , which allows to turn plastic into diesel fuel. It always takes a lot, therefore, if the technological process of processing is economically beneficial, plastic can be processed in large quantities. So far, the Chinese work only with polyethylene.
')
Polyethylene - a thermoplastic polymer of ethylene, belongs to the class of polyolefins. It is an organic compound and has long molecules ... —CH2 — CH2 — CH2 — CH2 —…, where “-” denotes covalent bonds between carbon atoms. The most common plastic in the world. For processing comes in the form of granules from 2 to 5 mm. Polyethylene is obtained by polymerization of ethylene. Polyethylene products are suitable for processing and subsequent use. Polyethylene (except for ultrahigh molecular weight) is processed by all methods known to plastics, such as extrusion, blown extrusion, injection molding, and pneumatic molding.

The process proposed by the Chinese consists of two stages. Both the first and second stages of converting polyethylene to diesel require the use of catalysts. The first catalyst is composed of iridium (the Chinese do not disclose details about this compound). This catalyst removes some of the hydrogen from carbon bonds. As a result, some single bonds between carbon atoms are converted into double bonds. And this, in turn, opens up the possibility of using the second catalyst.

Chinese scientists also do not disclose its composition and structure, saying only that the catalyst includes atoms of rhenium and aluminum . Oil compounds are also used (experts do not disclose the names of the components). Under the influence of the second catalyst, the double bonds between carbon atoms are broken, and the molecules of the oil compounds are attached to the ends of the formed components.


Types of polyethylene products that can be recycled

The whole process is cyclical. As mentioned above, the first catalyst displaces hydrogen atoms from polyethylene. But the same hydrogen can be reused to convert double bonds between carbon atoms into single ones. Such reactions can be repeated again and again. If you do this for several hours in a row, all of the polyethylene is destroyed, only the components of this compound remain. To increase the speed of the reaction, a temperature of 150 ° C is needed.

Upon completion of the process polyethylene is divided into three main types of components. The first type is simple organic compounds like butane, it can be used for other chemical reactions in production. The second is the wax-like compounds that are needed to make plastics. And the third type is diesel.

By changing the various steps of the polyethylene conversion process, researchers can increase or decrease the yield of each of these three components. According to Chinese scientists, most plastics can be divided into individual components using this type of reaction. But for other types of plastic reaction conditions will be somewhat different. The advantage of the proposed solution is high efficiency and relatively mild reaction conditions.

Scientists who developed this method plan to patent it in 2017. Perhaps the commercial use of the proposed process will begin later this year.