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By harnessing a new synthesis technique, the research team said it was able to produce a light-olefin yield of 48 per cent, far more than the previously confirmed yield of less than 27 per cent.
Light olefins refer to olefins with fewer carbon atoms, such as ethylene, propylene and butenes.
The traditional synthesis method, known as the Fischer-Tropsch process, believed to date back to the early 1920s, begins with converting coal into a mix of carbon monoxide and hydrogen. The gas mixture, called syngas, is then transformed into olefins. The conversion happens with the help of a specific catalyst – the key element in the process. However, the efficiency of such reactions has always been limited.
In 2016, a research team led by Professor Pan Xiulian and academic Bao Xinhe from the Dalian Institute of Chemical Physics (DICP) first proposed a new synthesis technique known as OXZEO. This method used a composite catalyst system that separated the decomposition of the reactants from the formation of products. By separating these two processes, the reaction efficiency was significantly increased.
For the first time, OXZEO managed to shatter the classical limit of the Fischer-Tropsch synthesis, raising the selectivity of light olefins from 58 to 80 per cent when the conversion rate of carbon monoxide was 17 per cent. The method also consumed less water and emitted fewer exhaust gases because of its higher conversion rate.
Still, the reaction had its limitations – it was not possible to simultaneously increase the conversion rate and selectivity. Achieving a higher conversion rate of carbon monoxide meant that the proportion of olefins in the product would decrease. Conversely, achieving a highly pure product meant that the conversion rate of reactants would decrease.
After another seven years of research, the team was able to improve the catalyst system, which not only promoted the reaction rate, but also suppressed the occurrence of side reactions. While maintaining a selectivity of more than 80 per cent for light olefins, the catalyst has now achieved a conversion rate of 85 per cent for carbon monoxide.
