Novel polyhedral@SiO2 core-shell catalysts designed for Fischer-Tropsch synthesis

Background: Fischer-Tropsch synthesis (FTS) has attracted much attention for converting syngas to liquid fuels. Enhanced catalytic stability and excellent product selectivity can be achieved by rational design of catalysts. However, the traditional SiO2-supported Fe-based catalysts display higher interaction between active metal and SiO2 support, thus resulting in a lower catalytic activity. Rational design of catalysts with weaker Fe-Si interaction promises excellent catalytic performances. Results: Novel polyhedral@SiO2 core-shell catalysts with adjustable shell thickness were prepared. The incorporation of SiO2 shell with suitable thickness can maintain the integrity of the active structure, and thus promising excellent C5+ productivity combined with higher catalytic activity. On the other hand, the SiO2 layer can prolong the residence time of CnHm intermediates on the active surface of Fe particles that enhance the C-C coupling reaction, favoring chain growth for production of C5+ yield. However, excessive addition of tetraethyl orthosilicate cannot increase the shell thickness in the absence of ammonium hydroxide and can be responsible for a poor CO conversion. Si-66 with shell thickness of 66 nm achieves an optimum C5+ yield of 2.23 x 10(-3) g(HC) g(Fe)(-1) s(-1) and a higher iron time yield value of 31.5 mu mol(CO) g(Fe)(-1) s(-1). Obviously, this C5+ yield is comparable to that for the Mn-promoted FeSiMn catalyst (2.22 x 10(-3) g(HC) g(Fe)(-1) s(-1)) reported in our previous work. Conclusions: The introduction of SiO2 as shell can improve structural stability during FTS. Moreover, the novel polyhedral@SiO2 core-shell catalyst exhibits excellent C5+ yield, and which is 1.8 times higher than that for a spindle@SiO2 core-shell catalyst reported in our previous work. (C) 2022 Society of Chemical Industry (SCI).