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Zirconium‐based intermetallics as heterogeneous catalysts for the fischer‐tropsch reaction: I. Zr‐Ni‐Co catalysts
Author(s) -
AlShammary A. F. Y.,
Caga I. T.,
Tata A. Y.,
Winterbottom J. M.,
Harris I. R.
Publication year - 1992
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.280550410
Subject(s) - zirconium , intermetallic , hydrogen , catalysis , materials science , carbon monoxide , activation energy , methanation , analytical chemistry (journal) , zirconium alloy , paramagnetism , inorganic chemistry , chemistry , metallurgy , physics , organic chemistry , alloy , quantum mechanics , biochemistry , chromatography
Alloys of the general formula Zr 50 Ni x CO 50‐x , where 0 ≦ x ≧ 50, have been prepared and used in the temperature range 300–400°C, in the pressure range 1–9 barg in a microtubular reactor for the reaction of hydrogen with carbon monoxide to give hydrocarbons. The alloys or intermetallic materials were prepared by argon arc melting, powdered by hydrogen decrepitation and characterised by means of optical microscopy (metallography), scanning electron microscopy with surface analysis and magnetic susceptibility measurements. The selectivity towards higher hydrocarbons increased with (i) increase in the total pressure and (ii) decrease in hydrogen content of the feed gases. The kinetics were found to be of the form:\documentclass{article}\pagestyle{empty}\begin{document}$$ r = k\,p_{H_2 }^m p_{CO}^n $$\end{document}where m = 1.0 ± 0.2 and n = 0. The apparent energy of activation (E a ) lay in the range of 80–130 kJ mole −1 and there appeared to be a compensation effect between E a and the pre‐exponential factor A. The turnover numbers for the reaction exhibited an activity maximum for alloys of composition around Zr 50 Ni 40 Co 20 and Zr 50 Ni 30 Co 20 . Magnetic susceptibility measurements indicated that alloys changed their nature from moderately paramagnetic to strongly paramagnetic or even ferromagnetic after use and this is attributed to the conversion of zirconium to zirconium oxide during reaction with the attendant production of free 3d‐transition metals. Derived catalysts prepared by air treatment of the hydrogen‐decrepitated intermetallics behaved almost identically to the latter materials and gave similar magnetic susceptibility values to used hydrided materials.