Major breakthrough in direct conversion of syngas to low-carbon olefins

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This post was last edited by liaifeng on 2018-8-9 at 09:05. Major breakthrough in direct conversion of syngas into low-carbon olefins. Author/Source: Date: 2017-09-25. Clicks: 2. Low-carbon olefins include ethylene, propylene, and butylene; they are widely used in the production of plastics, fibers, etc., and serve as important chemical raw materials as well as the foundation of the modern chemical industry. Traditionally, they are obtained through the cracking of naphtha. Given that our country is rich in coal but poor in oil and gas, it is of great strategic significance to develop methods for producing low-carbon olefins from non-petroleum carbon sources such as coal, natural gas, and biomass. Syngas (a mixture of CO and H2) is an important platform for the conversion and utilization of carbon resources such as coal and natural gas. In the 1920s, German scientists invented the Fischer-Tropsch process for producing liquid fuels from coal via syngas; it is currently the only effective method for directly converting syngas into low-carbon olefins. However, the drawback of this method is its low selectivity for the target product; for example, the selectivity for C2-C4 hydrocarbons (hydrocarbons with 2 to 4 carbon atoms, including alkanes and alkenes) among all hydrocarbons is no more than 58%. In 2012, the team led by the internationally renowned professor in the field of C1 chemistry, de Jong, made a breakthrough by optimizing the composition and structure of F-T catalysts; at a conversion rate of less than 1.5%, the selectivity for low-carbon olefins was 61%, and even at a conversion rate of 88%, the selectivity for low-carbon olefins remained as high as 52%. In 2016, a team led by researchers Bao Xinhe and Pan Xiulian from the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, proposed a new route different from the traditional Fischer-Tropsch process (the OX-ZEO process). By creatively using a novel bifunctional nanocomposite catalyst, this approach enables the direct conversion of syngas into low-carbon olefins in just one step, with a selectivity of up to 80%; the selectivity for C2-C4 hydrocarbons exceeds 90%, which is far higher than the theoretical limit of 58% for low-carbon hydrocarbons in the traditional Fischer-Tropsch process. Moreover, the catalyst maintained stable performance throughout 110 hours of testing. This catalyst cleverly separates the catalytic active centers for the two key steps of CO molecule activation and intermediate C-C coupling: here, CO and H2 molecules are adsorbed and activated at the defect sites of partially reduced metal oxides to form CH2 intermediates; the reactive CH2 then combines with CO to form the gaseous intermediate CH2CO, which proceeds through a selective C-C coupling reaction in the confined environment of the acidic pores of the molecular sieve MSAPO, thereby enabling the directed formation of low-carbon olefins. Studies have shown that by controlling the pore structure and acid properties of molecular sieves, the product molecules can be modified in a controlled manner. On the other hand, by replacing H2 with CO to eliminate excess oxygen atoms in hydrocarbon formation, it is possible, in principle, to eliminate the energy- and water-intensive water-gas shift reaction for hydrogen production, thereby reducing the energy and water consumption associated with the chemical reactions themselves, without altering the total CO2 emissions. This opens up a new technical route for the further development of strategic emerging industries in China that rely on coal conversion to produce low-carbon olefins. This research finding was published in 2016 in Science, and in the same issue the journal featured a review article by de Jong titled \"Surprising Selectivity,\" which argued that the OX-ZEO process would be highly competitive on an industrial scale in the future.