Performance of combined cobalt—nickel—zirconia and HZSM‐5 catalyst systems for carbon monoxide hydrogenation

The synthesis of hydrocarbons via hydrogenation of carbon monoxide was investigated over cobalt—nickel—zirconia catalysts of various compositions in combination with zeolite HZSM-5 in “mixed bed” and “follow bed” arrangements. These combinations resulted in the formation of aromatics in amounts as high as 30-35 wt% under relatively mild operating conditions (1 atm, 250–280°C). Although the olefinicity of C2 and C3 fractions in the product stream was higher in the mixed bed compared to the follow bed arrangement, the selectivities to aromatics were comparable in the two bed arrangements. The aromatic selectivity was found to be sensitive to operating conditions. The formation of aromatics was favored at high HZSM-5/metal catalyst ratios, low space velocities and high reaction temperatures. The product distributions obtained using various metal/zeolite bifunctional catalysts have been discussed. On a etudie la synthese d'hydrocarbures par hydrogenation du monoxyde de carbone sur des catalyseurs cobalt—nickel—oxyde de zirconium de diverses compositions, associes avec la zeolite HZSM-5, dans des arrangements de lits melanges ou de lits successifs. Ces combinaisons out conduit a la formation de produits aromatiques, en quantites allant jusqu'a 30–35% en poids dans des conditions operatoires relativement moderees (1 atmosphere, 250-280°C). Bien que la teneur en olefines des fractions en C2 et C3 dans les produits soit plus elevee dans l'arrangment des lits melanges que dans celui des lits successifs, les selectivites en aromatiques se sont averees comparables dans les deux arrangements. On a trouve que la selectivite en aromatiques etait sensible aux conditions operatoires. Des proportions elevees en zeolite ZSM-5 par rapport aux catalyseurs metalliques, des temps de contact eleves et des temperatures de reactions elevees favorisent la formation des aromatiques. On discute les distributions des produits obtenus en employant divers catalyseurs bi-fonctionnels metal/zeolite.

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