Possibilities for the preparation of new metal sulfide catalyst systems based on carbon carriers having favourable textural and surface properties have been explored, and attention has been given to the characterization (structure) and evaluation (hydrosulfurization activity) of these catalysts. Two different types of carbon carriers were prepared viz., carbon black composite and carbon-covered alumina. The influence of various carbon carrier oxidative treatments on the activity of the supported sulfide phase has been studied. For the characterization of the structure of the active (Mo) sulfide phase deposited on an (activated) carbon carrier a combination of dynamic oxygen chemisorption, thiophene hydro desulfurization and X-ray photoelectron spectroscopy measurements was applied. Carbon black composites having outstanding textural properties for the application as support material for molybdenum sulfide catalysts could be prepared. The Inertness of their surface appeared to be a drawback for obtaining h'igh catalytic activity. However, catalytic activity was considerably improved after the reactivity of the carbon surface towards the molybdenum phase was Increased by means of an oxidative treatment. The carbon-covered aluminas prepared had promising textural properties. Covering the alumina surface by a layer of pyrolitlc carbon was found to improve the activity of supported (cobalt) sulfide phase. In none of the carboncovered aluminas prepared the alumina surface was completely covered since the carbon was not uniformly deposited. Therefore the maximum effect of the carbon coverage on the catalytic activity was never reached. However, heat treatment of the pyrolitic carbon appeared beneficial in this case. The results of dynamic oxygen chemisorption measurements showed that the molybdenum sulfide phase supported on active carbon had a high density of only one type of active site with a high turn over frequency. The alumina supported molybdenum phase had a lower active site density and different types of sites seemed to be present at low and high molybdenum concentration. For both the Mo/C and Mo/¿-Al2O3 catalysts, the decline in activity with run time was not reproduced by the oxygen chemisorption capacities. Thus Initial deactivation was neither caused by sintering of the active phase nor by pore blocking.
|Number of pages||7|
|Journal||Erdöl und Kohle, Erdgas, Petrochemie, vereinigt mit Brennstoff-Chemie|
|Publication status||Published - 1987|