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Modification of Co/Al 2 O 3 Fischer–Tropsch Nanocatalysts by Adding Ni: A Kinetic Approach
Author(s) -
Nikparsa Paria,
Mirzaei Ali Akbar,
Rauch Reinhard
Publication year - 2016
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.20978
Subject(s) - fischer–tropsch process , nanomaterial based catalyst , chemistry , catalysis , kinetic energy , activation energy , adsorption , reaction rate constant , analytical chemistry (journal) , reaction rate , fourier transform infrared spectroscopy , selectivity , chemical engineering , kinetics , organic chemistry , physics , quantum mechanics , engineering
ABSTRACT In this article, the effects of Ni (Co:Ni ratio = 4:1) on the performances and kinetic parameters of Co/Al 2 O 3 nanocatalysts are explored in Fischer–Tropsch synthesis. As a result, the probability of chain growth increases and the deactivation rate decreases with addition of Ni. The properties of catalysts are characterized at different stages using Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and the vibrating sample magnetometer technique. The Co/Ni/Al 2 O 3 catalyst with higher surface area and pore size exhibits higher activity and C 5+ selectivity. The different results obtained for room‐temperature ferromagnetism have been attributed to the different metal oxides in the catalysts. The Fischer Tropsch kinetic study is done on the basis of the Langmuir–Hinshelwood–Hougen–Watson adsorption theory. Seven kinetic expressions based on the carbide and enolic mechanisms are selected. All experimental data are theoretically examined with these kinetic expressions to derive the best kinetic according to the linear and nonlinear approaches. The kinetic parameters of the fitted model, including the rate constant ( k ) and activation energy ( E a) , are calculated with the Levenberg–Marquardt and genetic algorithm. The results show that by adding Ni the activation energy ( E a ) decreases, the reaction rate (– R CO ) increases, and the CO adsorption on the Co/Ni/Al 2 O 3 catalyst is faster as well.