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Nano-limited catalysis is a universal concept, coal-to-olefin is only one of its applications, and its application in the future is unlimited.
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This video was released on April 22, 2022 and has reached 69,000 views
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In order to reduce the dependence on imported oil, what can we think of? Many people think of new energy sources and electric vehicles, and many people think of controlled nuclear fusion. These are important, of course, but they all focus on the application of oil as an alternative to energy. In fact, there is another major application of petroleum, which is as a chemical raw material. China consumes nearly 700 million tons of oil a year, of which 120 million tons are used in chemical production (https://www.cas.cn/zkyzs/2021/12/327/cmsm/202112/t20211221_4819027.shtml). Therefore, the production of chemicals from other feedstocks has strategic value.
Among other raw materials, the most abundant reserves are coal. The reserve-to-production ratio of oil, that is, the ratio of reserves to mined amounts, is only a few decades, and the storage-to-production ratio of coal is hundreds of years. So the term "coal-to-olefins" sounds bland, but it's actually worth a lot, because most chemicals are made from olefins, and we often hear how many tens of thousands of tons of ethylene are used to measure the production capacity of chemical plants. Academician Bao Xinhe, president of the University of Science and Technology of China, and his team at the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences won the first prize of the 2020 National Natural Science Award, and the main achievement was coal to olefins.
In fact, the industry invented the technology of coal to olefins a hundred years ago. It is the "Fischer process", named after the two inventors, the German scientists Fisher and Topsch. In this process, carbon monoxide (CO) molecules are first actively dissolved into carbon (C) atoms and oxygen (O) atoms by metal or metal carbide catalysts, and then hydrogenated to form methylene (CH2) intermediates, while releasing water molecules. Methylene intermediates polymerize on the surface of the catalyst to form hydrocarbon products containing different numbers of carbon atoms.
The Fisto process is widely used, but what are its drawbacks? The biggest drawback is low selectivity. We want to produce low-carbon olefins, but methylene will continue to polymerize. So in theory, it can be calculated that the proportion of olefins with 2 to 4 carbons can only be up to 58% (https://www.cas.cn/cm/202111/t20211105_4812752.shtml). In addition, it consumes a large amount of hydrogen (H2) to remove oxygen atoms, which generally comes from water gas transformation. This is a high water consumption, high energy consumption process, and at the same time emits a lot of carbon dioxide (CO2), which are serious problems.
Over the past hundred years, scientists have done a lot of exploration to improve the Fischer-Tropsch catalyst, but they have not been able to push the theoretical limits of selectivity. At the same time, the activity and selectivity of catalysts are often seesaws, and one is high and the other is low.
With so much background in mind, the contributions of Bao Xin and the academician team came to light: they proposed a new technical route that overcame the shortcomings of the Fiitow process. The key here is "nano-limited catalysis", which is the new scientific principle they proposed. In fact, the name of their first prize in natural science is nano-limited catalysis, which is a scientific concept, not a practical effect such as coal to olefins.
The nanometer is 10 to the power of 9 meters, which is about the scale of 10 atoms. Nano-domain catalysis means that when the catalyst is confined to a small space at the nanoscale, such as inside a carbon nanotube, or at the interface of a metal and an oxide, its electronic structure changes, making the catalytic activity increase.
For example, in the past, the selectivity of the Fischer-Tropsch reaction could not exceed 58%, because the surface of the catalyst was open, and the polymerization reaction of the intermediate methylene was random, and it could not brake, and eventually a large number of unwanted high carbon products would be generated. Now that they have intermediates entering the nanoscale molecular sieve pores, they can generate low-carbon olefins in a targeted manner, which is greatly improved in selectivity (Comics: Chinese scientists propose a new concept of physical chemistry: nano-limited catalysis | Sheldon》）。
In addition, previously the Fischer-Tropsch process used a single catalyst to perform two roles: activation and coupling. Activation is the preparation of CH2 from CO and H2, and coupling is to make CH2 join together to form olefins. Now they have separated these two steps and implemented them with two catalysts, activating the oxide in the interface limit and coupling the molecular sieve pore limit just mentioned. One step becomes two steps, which seems complicated, but in fact, it is simple, because the efficiency of both steps is greatly improved. In this way, the Fischer-Tropsch route is abandoned, eliminating the water-consuming and energy-consuming water-gas conversion to hydrogen production and the water-hydrogen cycle process, creating a new way for low water consumption to transform coal through syngas step by step.
The technology is not yet being applied on a large scale, but is undergoing industrial experiments. In cooperation with Shaanxi Yanchang Petroleum (Group) Co., Ltd., they built the world's first set of 1,000-ton coal directly into low-carbon olefins industrial test equipment through syngas, and successfully completed the industrial whole process test in 2020, verifying the feasibility and advancedness. Teacher Bao is a very sincere and down-to-earth person, he said in an interview with reporters: "We are now studying to this extent, and do not exaggerate (https://www.cas.cn/cm/202111/t20211104_4812456.shtml). ”
In the 2020 National Science and Technology Award, another achievement is closely related to it, but it has been practically applied, that is, the "4 million tons / year coal indirect liquefaction complete set of technological innovation and industrialization" in the first prize of the Science and Technology Progress Award. See the difference, right? This is coal-to-oil, and Mr. Bao's team is doing coal-to-olefins. This coal-to-oil technology is mainly developed by the Shanxi Institute of Coal Chemistry of the Chinese Academy of Sciences, and the basic technical route is still Fischer-Tropsch synthesis, and there will be opportunities to introduce it to you in detail later.
Finally, I would like to say that I attach more importance to the contribution of Chinese scientists in proposing new concepts than to practical effects. For example, nano-limited catalysis here is a universal concept, coal-to-olefin is only one of its applications, and its application in the future is unlimited.
In the past, when everyone opened the textbook, there were only a few names of Chinese scientists. The Chinese scientific community has made great strides in recent years, but most people are unaware of these latest developments. Not long ago, I introduced the "gathering induces luminescence" discovered by Academician Tang Benzhong ("The real pleasure of scientific research lies in its unpredictability| Technology Yuan Ren"), which is one of the hottest concepts in the field of nanoluminescence. If there are more fields pioneered by Chinese scientists such as nano-limited catalysis and aggregation-induced luminescence, we can say that China has made due contributions to the world.