Fischer-Tropsch synthesis is a key reaction for sustainable production of fuel and chemicals via syngas but a very complicated catalytic reaction process with co-production of paraffin, olefin, alcohol and other products. For the purpose of high selectivity to the objective product, it is very desirable to regulate the reaction network for certain reactions to take place preferentially. Obviously, one of the great challenges in FTS research is to control CO activation and then both carbon chain growth and termination. In the past decades, syngas to fuel and chemicals via FTS were investigated at our group, including fundamental research and industrial deployment. Herein, some progress in the study of reaction network and structure-performance relationship are discussed to shed a light for development of next generation catalyst. A CuFe-based HAS model catalyst was firstly investigated to illustrate the complicated reaction network. Various kinds of reactions occurred in parallel, such as F-T reaction, methanol synthesis reaction, C2+OH formation reaction and WGS reaction. There also existed various second reactions in the reaction network, such as dehydration of alcohols, hydrogenation of olefin. High space velocity benefited for higher selectivity to total alcohols and lower selectivity to CO2. However, high space velocity hindered carbon chain growth and shifted the product to low carbon number. Several types of probe molecules (including alcohol, aldehyde, olefin and CO2) were in-situ introduced into the reaction system to further investigate the catalytic mechanism and reaction network. The existence of surface acyl species indicated that the insertion of CO rather than hydroxyl was the underlying mechanism for higher alcohols synthesis over modified FT catalysts along with the support from surface simulation. However, the effect of CO2 was reversible and the catalytic performance could be recovered after switching to pure syngas. The structural evolution of CuFe bimetallic nanoparticles indicated that phase separation between Cu and Fe components took place and then alcohol selectivity decreased with time on stream. In addition, ethane hydrogenolysis test as probe reaction and in-situ EXAFT were also adopted to reveal the detail surface structure evolution. Based on the above, both reaction network and structure-performance relationship were discussed for the development of next generation catalysts in our group.

Syngas to fuel and chemicals via FTS: Reaction network and structure-performance for catalyst development

249th National Meeting (2015)

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