Catalytic Properties of Bimetallic Catalysts Based on Binary Complexes of Transition Metals in Fischer-Tropsch Synthesis
A. A. Khassin1, S. I. Pechenyuk2, D. P. Domonov3, T. P. Minyukova4, G. K. Chermashentseva5, G. N. Kustova6, L. M. Plyasova7
1 Boreskov Institute of Catalysis, aakhassin@catalysis.ru
2 Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials
3 Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials
4 Boreskov Institute of Catalysis
5 Boreskov Institute of Catalysis
6 Boreskov Institute of Catalysis
7 Boreskov Institute of Catalysis
Abstract
The possibility to prepare bimetallic catalysts Fe-Ni, Fe-Co and Co-Cu through thermolysis of binary complex salts involving a complex cation of one metal and a complex anion of other one is discussed, and their catalytic properties in Fischer-Tropsch synthesis are presented. Our study revealed that deposition of binary complex salts having composition [Ni(NH3)6]3[Fe(CN)6]2, [Co(NH3)6][Fe(CN)6] and [Co(NH3)6]2C2O4[Cu(C2O4)2]2 on to the surface of aluminium hydroxide and subsequent thermolysis of the obtained composition give the chance to have metallic particles of size 15-40 nm fixed on the surface of aluminium oxide. In the case of binary complexes Ni-Fe and Co-Fe, the formation of bimetallic particles of size 15-16 nm and respective structures FCC and BCC is observed. Break-up of complexes proceeds in several sequential exothermic stages. The catalytic properties of bimetallic particles Fe-Co of BCC structure, which are prepared by thermolysis of [Co(NH3)6][Fe(CN)6] + Al(OH)3 composition, differ essentially from the literature data for Co-Fe catalysts by the reduced activity of the prepared particles with respect to the secondary processes for hydrogenation of olefins. This feature manifests itself in the extremely high selectivity of the process in relation to olefines and its anomalous temperature dependence. A rise in the process pressure up to 10-20 atm leads to significant changes in catalytic properties of bimetallic Co-Fe catalysts, among them the loss of selectivity in relation to olefins and the decrease in the rate of secondary process of vapour conversion of CO. The pressure dependence of process passing character is caused by variation in structure of catalytically active component under the action of reagents.
|
