Synergy between the CoMoS Phase and Supported or Unsupported Cobalt Sulfide. Existence of a Remote Control Effect

MOHAMED KARROUA,; HARIS MATRALIS,; EDGARDO SHAM; PAUL GRANGE; BERNARD DELMON

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN

CHEMICAL SOC JAPAN

Año: 1995 vol. 68 p. 107 - 119

0009-2673

Unsupported Co9S8, MoS2, and CoMoS sulfides (prepared by the HSP method) as well as supported MOS2/Ab03 and CoSx/C (prepared by impregnation) were used to prepare a series of binary mechanical mixtures of various compositions. A variety of physicochemical techniques (temperature programmed decomposition and sulfidation, both followed by subsequent TPO, XRD, TPR, microelectrophoresis, XPS and AEM) were used to study the samples, verif¡r the formation of the "CoMoS phase" in the mixed CoMo sulfide and investigate the existence of interactions between the sulfides forming the mechanical mixtures. The catalytic activity of the supported and unsupported HSP sulfides as well as that of the mechanical mixtures was tested in the hydrodesulíurization of thiophene (HDS) and the hydrogenation oí cyclohexene (HYD) at 573 K and 3 MPa. The mechanical mixtures exhibit a synergy. in HDS and HYD. This shows that cobalt sulfide (supported or unsupported HSP) can promote the activity not only oí molybdenum sulfide, but also of the unsupported HSP "CoMoS phase". In addition, XRD and AEM (performed before and after catalytic tests) were used to study the evolution of the unsupported "CoMoS phase" during the catalytic reaction. It was found that this phase is unstable; cobalt segregates from the CoMoS association to form C09SS, even after a relatively short period in the reactor. These resulta provide more evidence that the remote control mechanism plays a major role in the synergetic behavior of the CoMo hydrotreating catalysts.