Metal-ion pillared clays as hydrocracking catalysts (I): Catalyst preparation and assessment of performance at short contact times

A set of pillared clay catalysts based on montmorillonite (a natural clay) and laponite (a synthetic clay) have been prepared. The new catalysts have been pillared with tin, chromium and aluminium pillars as well as layered double hydroxides based on polyoxo-vanadate and -molybdate. The activities of these novel catalysts have been compared with that of a commercial supported NiMo/Al2O3 catalyst and with sulphided Mo(CO)6 during short (10 min) contact runs. A coal extract sample was reacted at 440 °C in a microbomb reactor in the presence of tetralin and 19 MPa hydrogen. Products were compared by size exclusion chromatography, using NMP as eluent, and by UV–fluorescence. Boiling point distributions of hydrocracked products were determined by a TGA based method; ‘conversions’ were defined as the decrease in the fraction of material with boiling points >450 °C during the reaction. Previous work at 440 °C and 19 MPa H2 indicates extensive thermal (pyrolytic) cracking during the first 10 min; in the absence of catalyst recombination reactions rapidly take over. Results with several of the new catalysts did not show any improvement compared to the absence of catalyst with ∼39% conversion. The highest conversion (∼70%) was obtained with the Sn laponite pillared clay. The Cr montmorillonite catalyst, pre-calcined at 500 °C, gave the greatest overall shift to smaller molecular masses even though the observed conversion of >450 °C boiling material was relatively poor.