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This article comes from the official account of Wechat: SF Chinese (ID:kexuejiaodian), author: SF

Do you believe that coal can be turned into water? Recently, Chinese scientists have made new breakthroughs in this field. However, the "water" mentioned here is not water in the real sense, but a kind of liquid substance-olefins. For olefins, except in high school chemistry textbooks, many people may be relatively strange. In fact, all kinds of plastic products that are common in our daily life, such as shoes, clothing, mobile phones and beverage bottles, are made from olefins.

(by Mei Lin / tr. by Robert Taylor)

Olefin is a kind of important chemical raw materials, and olefin is needed in the manufacture of common plastic products mentioned above. At present, in the field of chemical industry, the widely used method of producing olefins is to produce olefins from petroleum. And China is a country with relatively few oil reserves, if it wants to meet the needs of production, it needs to import more oil, affecting China's energy security.

As a result, some scientists have come up with a new direction for producing olefins from coal. Compared with oil, China is rich in coal resources. At present, coal is mainly used as energy material.

In recent years, with the concept of low-carbon environmental protection deeply rooted in the hearts of the people and the national plan to realize the "double-carbon" double-carbon strategy, the green and environmentally friendly use of coal resources has become a new direction of scientific research. From the point of view of environmental protection, the production of olefins from coal is a new way of green utilization of coal.

Coal turns into "water". There has long been a way to react hydrocarbons in coal, oil and natural gas with oxidants to form a mixture of carbon monoxide and hydrogen, which is called syngas. After a series of chemical reactions, syngas will be converted into olefins and other important chemical raw materials. In the actual chemical production, the key to producing olefins from coal is the catalyst.

In 2016, the research team of Dalian Institute of Chemical Engineering of the Chinese Academy of Sciences changed the active component of traditional catalysts from metal or metal carbides to OXZEO, a composite catalyst of metal oxides and molecular sieves. As a result, in the process of preparing olefins, the selectivity of olefins (representing the singleness of the reaction product) reached 80%.

However, the OXZEO catalyst is not perfect-in the OXZEO-catalyzed reaction, the conversion of carbon monoxide is only 17%. This means that carbon monoxide is not reactive, and to produce enough olefins requires a large amount of nitric oxide, which will increase costs.

A new generation of OXZEO catalyst: breaking the reaction "seesaw" for this reason, scientists from Dalian Institute of Physicochemistry, Chinese Academy of Sciences have carried out further research. They found that the primary OXZEO catalyst increased the selectivity of olefins, but did not increase the conversion of carbon monoxide because the catalyst not only catalyzed the main reaction of olefin formation, but also catalyzed two side reactions. In this way, once the conversion of carbon monoxide is increased, more other products will be formed through the side reaction, thus reducing the selectivity of olefins. Therefore, under the premise of ensuring the selectivity of olefins, the conversion of carbon monoxide can only be reduced.

In order to solve this problem of the primary OXZEO catalyst, the research team prepared microporous molecular sieves based on metal germanium ions on the basis of the original molecular sieves, which reduced the occurrence of side reactions. while ensuring that the selectivity of olefins was more than 80% (up to 83%), the conversion of carbon monoxide reached an astonishing 85%, improving the reaction efficiency.

Published in the May 19, 2023 issue of the journal Science, this breakthrough has completely subverted the inherent mode of production in the coal chemical industry for more than a century, successfully solved the seesaw problem in traditional catalytic reactions, which is difficult to improve activity and selectivity at the same time, and greatly reduced the consumption of water and energy.

References:

Disentangling the activity-selectivity trade-off in catalytic conversion of syngas to light olefins | Science

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