Izvestia: Scientists find a way to reduce the cost of plastic bags
What compounds will help to produce films, perfume components, plastic products and fertilisers more efficiently in the Russian Federation
Russian scientists have come up with a new way to develop elements to produce polyethylene. Researchers found out how to make the expensive noble-metal catalysts for the film-making process last longer. Technology should reduce the cost of production. Being able to reuse the catalyst outweighs the small loss in its performance and will save significant amounts, experts say. Additionally, the developed elements can be used for the production of components of perfume compositions, plastic products, and fertilisers.
Metal icebergs
Russian scientists from St Petersburg University, N.D. Zelinsky Institute of Organic Chemistry at the Russian Academy of Sciences, and the Centre of New Chemical Technologies at the Siberian Branch of the Russian Academy of Sciences proposed a new method for the synthesis of metal-carbon catalysts. They are needed to create polyethylene for the packaging of many products.
The results of the research supported by a grant from the Russian Science Foundation were published in the Journal of Catalysis.
Films are made from ethylene, i.e. an organic substance with the simple formula C2H4. The problem is that the latter contains impurities of acetylene C2H2. The feedstock is purified from it using catalysts.
‘Acetylene "poisons" catalysts. They lose their activity and the properties necessary for the reaction. The catalysis are noble metals and are very expensive,’ explained Konstantin Rodygin, Principal Investigator of the project and Research Associate at St Petersburg University.
The new method makes it possible to prolong the operation of catalysts and make the production of polyethylene cheaper. The technology is that metal nanoparticles are immersed in a carrier. The resulting systems can work for several cycles. To obtain this construction, the scientists mixed calcium carbide (a compound of calcium with carbon) with various metal salts and heated it in a stream of chlorine. With this exposure, metal salts were reduced to pure metals, and calcium carbide was decomposed to high-purity carbon.
‘The metal particles melted carbon and partially immersed in it,’ said Konstantin Rodygin. ‘We had a kind of metal icebergs in the carbon sea. Additionally, a thin, only a few atoms thick, carbon film covered partially the metal tops, firmly holding the metal and preventing it from leaving the surface. We have received palladium, platinum, gold, silver, copper, and other metals on carbon, and even their alloys.’
New catalysts can be used for the production of not only polyethylene.
‘They convert a variety of compounds into the necessary ones, for example, those used for the production of pesticides, perfumes, plastics,’ said Roman Mironenko, Senior Research Associate at the Centre of New Chemical Technologies at the Siberian Branch of the Russian Academy of Sciences.
Well hidden
The new approach will have a positive economic effect, the scientists say. Alexander Polezhaev is Head of the Laboratory "Functional Composite Materials" at the National Technological Initiative Centre ‘Digital Materials Science’ at Bauman Moscow State Technical University. According to him, new efficient catalytic systems can save millions of dollars and improve the efficiency and environmental friendliness of existing industries. Polyethylene is produced in millions of tons per year, he said.
‘In the world, a huge number of companies are working on improving catalytic systems. Yet only some solutions enter the industry. Nevertheless, this is a very important step towards understanding the ways to deactivate catalysts and possible approaches to their stabilisation and to increase the number of use cycles,’ said Alexander Polezhaev.
With this approach, there will be a slight loss in the maximum performance of the catalyst, but the possibility of its reuse will increase several times, said Anton Konopatsky, Senior Research Associate in the Inorganic Nanomaterials Laboratory at the National University of Science and Technology "MISIS".
‘The approach developed by the scientists is well-known, yet it is used seldom,’ said Anton Konopatsky. ‘The protective shell does not enable metal particles to sinter together. All catalytically active particles retain their size and properties. In their work, the authors showed the applicability of the developed technique to a number of metals, including expensive palladium, platinum and gold.’
Additionally, Aleksandr Glotov, Senior Research Associate in the Department of Physical and Colloidal Chemistry at Gubkin University, underlined the complexity of the method.
‘Chlorine is used to produce the catalyst, which makes high demands on labour protection and equipment manufacturing,’ said Aleksandr Glotov.