Abstract
The research of the formation mechanism of iron carbides is significant to design the high-performance catalysts for the Fischer–Tropsch synthesis (FTS) process. In this paper, the effect of potassium promoter on the formation of atomic carbon via carburization gases dissociation on the iron-based catalyst, the C2H4, C2H2 and CO/H2 adsorption energies and dissociation paths as well as the rate constants of the corresponding elementary steps are investigated by DFT on the Fe(110), Fe(110)-K2O, Fe(211) and Fe(211)-K2O surfaces. The calculation results demonstrated that the K2O promoter can modify the capabilities of surface C formation via the thermodynamic method as well as the kinetical method. The K2O promoter can increase the CO adsorption energy while decreasing the C2H4 adsorption energy both on Fe(110) and Fe(211) surfaces. Kinetically, via tuning the catalyst surfaces from Fe(110) to Fe(211), the K2O promoter can inhibit the ability of C2H4/C2H2 dissociation to atomic carbon, while enhancing the ability of CO/H2 decomposition to atomic carbon. The C2H4/C2H2 dissociation rate constants on Fe(211) and Fe(211)-K2O are about 107 times slower than that on Fe(110) and Fe(110)-K2O, whereas the dissociation rate constants of CO/H2 on Fe(211) are about 106 times faster than that on Fe(110), and about 107 times faster on Fe(211)-K2O than on Fe(110)-K2O.
Highlights
Owing to the lack of crude oil, Fischer–Tropsch synthesis (FTS), which converts syngas (CO andH2 ) into valuable chemicals and clean fuels, is of important academic and commercial significance in China
As is well-known, carburization behavior of α-Fe catalyst is closely related on the nature of the catalyst and the pretreatment conditions
In order to illuminate the essential effect of the potassium promoter on the generation
Summary
Owing to the lack of crude oil, Fischer–Tropsch synthesis (FTS), which converts syngas (CO andH2 ) into valuable chemicals and clean fuels, is of important academic and commercial significance in China. The catalyst is one of the most key factors account for the successes of the industrial FTS process, and the iron-based catalysts are extensively studied and used for decades due to their low cost and relative high activity [1,2,3,4,5]. It is well known that the main active phases are iron carbides in the iron-based FTS [6,7,8]. The research of the formation mechanism of iron carbides is significant to design the high-performance catalysts for FTS process. The formation of carbon atoms via carburization gases dissociation on iron-based catalyst surfaces is the precondition for generation the iron carbides. The most studied carburization gases are CO and syngas, Catalysts 2020, 10, 527; doi:10.3390/catal10050527 www.mdpi.com/journal/catalysts
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
