Catalytic Tar Cracking of Hot Gas Derived from the Pilot Plant Pyrolysis of Dried Sewage Sludge Using Novel Ni/SBA-15 Catalyst Extrudates

Novel Ni/SBA-15 catalysts were synthesised and their activity in the dry reforming of methane process was assessed. Extrudates, in the shape of pellets, of these materials were prepared and tested in a pyrolysis pilot plant fitted with a catalytic reactor for the sewage sludge pyrolysis tar removal. The Ni/SBA-15 catalyst pellets remained highly active and stable throughout the test duration, converting 100% tar in the hot gas to smaller non-condensable gases, thereby increasing the pyrolysis gas fraction and eliminating the problematic tar in the vapour stream. Catalyst characterisation with Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX) analysis, Transmission Electron Microscope (TEM) and Thermogravimetric Analysis (TGA) confirmed that both, the Ni/SBA-15 powered catalyst and the pellets as well, were resistant to sintering and carbon deposition and remained highly active even with relatively high-level sulphur in the feed stream. The Ni/SBA-15 catalyst extrudates were prepared by mixing the powdered catalyst with varied amounts of colloidal silica binder and fixed amounts of methyl cellulose and water. The highest mechanical strength of the extrudates was determined to be for those obtained with 36% of the inorganic binder. The physical properties and catalytic activity of Ni/SBA-15 pellets with 36% colloidal silica was compared with the original powdered Ni/SBA-15 catalyst after crushing some of the pellets to powder to determine any binder inhibitory effect. The results confirm that colloidal silica binder did not inhibit the desired catalyst properties and performance in the reaction. Instead, an enhanced catalytic performance was observed.