A COMPARISON OF ALUMINA, CARBON AND CARBON-COVERED ALUMINA AS SUPPORTS FOR NI-MO-F ADDITIVES - GAS OIL HYDROPROCESSING STUDIES

Catalysts with 3 wt% NiO, 15 wt% MoO3 and 0-6.9 nominal wt% fluoride supported on alumina, carbon and carbon-covered alumina were studied to examine the role of fluoride and the influence of the support on hydroprocessing on Alberta gas oil. Experiments were carried out in a batch reactor at 410-degrees-C and 6.9 MPa initial H-2 pressure. It was found that fluoride promotion enhances cracking and hydrogenation reactions resulting in decreased aromatic and sulphur contents in the gas oil. The promotion is dependent on the type of support and is related to the strength of the fluoride-support interaction and the accessibility of the fluoride to the surface hydroxyl groups on the support. A maximum in activity at 3.6 wt% fluoride was observed for the alumina-supported catalysts whereas higher loadings of fluoride were required for carbon-covered alumina-supported catalysts to see an improvement over their carbon supported counterparts. However, the carbon-covered alumina supported catalysts seem to have a lower propensity for coke deposition than their alumina counterparts.