(111a) Catalytic Subcritical Hydropyrolysis of Waste Biomass and Selective Enrichment of Hydrocarbon Fuels

Subcritical hydropyrolysis of waste paper using novel catalysts was investigated as a means of producing hydrocarbon fuels. The proposed process involves two-steps: 1) complete conversion of the biomass in aqueous environment in presence of a homogeneous catalyst, and 2) selective conversion of bio-oil into hydrocarbons in presence of a metal supported mesoporous catalyst. In the first phase, the subcritical hydropyrolysis of biomass led to the formation of three product phases: a gas phase containing lighter gases and hydrocarbons (H2, CO, CO2 and CH4); a liquid bio-oil slurry containing alkanes, alkenes, aldehydes and carboxylic acids; and a solid residue (bio-char). The second step involves selective reduction of bio-oil into alkanes utilizing a mesoporous catalyst for hydrocarbon enrichment. The complete catalytic conversion of biomass was achieved at 250oC. In step-1, the experiments were performed with a slurry of 10-20 wt% waste paper in distilled water previously mixed with 5-8 wt% Cu2+/Ni2+ catalyst and heated in high pressure reactor at temperatures 150o-250oC for 3-4 hours. In step -2, a heterogeneous catalyst containing a metal immobilized on mesoporous silica was synthesized and used for selective enrichment of hydrocarbon fuel. Preparation of the mesoporous catalyst involved the synthesis methodology similar to MCM-41 followed by metal impregnation. It was performed using the surfactant assisted sol-gel synthesis route involving generation of an ordered mesoporous silicate structure with controllability of pore size and porosity. The gel formation was accomplished using silica precursor, ethanol, and Brij-76 surfactant well-mixed in acidified solution. After 24 h of aging, the gels were extracted in ethanol, treated in autoclave, and finally calcined at 600oC. The calcined powder was analyzed using transmission electron microscopy, atomic force microscopy, and powder x-ray diffraction. The mesoporous gels were functionalized with poly (4-vinyl) pyridine and treated with metal ions to establish binding with the mesoporous silicate network. Functionalization of the surface was confirmed using FTIR, and metallic concentration was determined using energy dispersive spectroscopy. It was found that a homogenous Ni2+ catalyst produced more hydrogen and a Ni-impregnated mesoporous silica catalyst generated higher hydrocarbons. Synthesis and characterization of a catalyst, hydrocarbon selectivity and results obtained on the aqueous phase subcritical reforming of the biomass including kinetic analysis will be presented.