Comparison of bulk CoMo bimetallic carbide, oxide, nitride and sulfide catalysts for pyridine hydrodenitrogenation

Abstract

Bimetallic cobalt-molybdenum oxide (CoMoO x) has been prepared and converted into CoMoN x, CoMoC x and CoMoS x materials by temperature-programmed reactions with ammonia, ethane or hydrogen sulfide, respectively. These new bimetallic materials have been characterised using X-ray diffraction (XRD) and solid state NMR and tested for pyridine hydrodenitrogenation (HDN) at various temperatures. The initial HDN activity of the catalysts decreases in order CoMoC x ∼ CoMoN x ∼ CoMoO x > CoMoS x. The stability order of the first three of catalysts is CoMoC x > CoMoN x > CoMoO x, and their activities decrease with the time on stream. In contrast the pyridine conversion over CoMoS x is more stable and activity increases with the time on stream, from 30 to over 50%, this is accompanied by the formation of CoMoSC x material. The high catalytic activity of the CoMoC x catalyst may reflect the ability to hydrocrack pyridine to yield methane. The CoMoS x catalyst system has the highest selectivity to the products cyclopentane (35%) and pentane (27%). A comparison between Co 4Mo 6 catalysts in carbide, nitride, sulfide, and oxide forms was studied for HDN of pyridine. The activities of these catalysts at steady state are shown in the order of: CoMoC x > CoMoN x > CoMoS x > CoMoO x. © 2004 Elsevier B.V. All rights reserved.