CATALYTIC GENERATION OF HYDROGEN AND CHEMICALS FROM BIOMASS DERIVED POLYOLS

The principal goal of this research is to produce hydrogen from biosustainable polyols, compounds containing a hydrocarbon chain with neighboring hydroxyl groups, such as glycerol or sorbitol. Hydrogen is an energy carrier which can replace oil and reduce pollution and greenhouse gas emissions when it is generated from renewable sources. At present, hydrogen is derived from fossil fuels such as natural gas, naphtha or coal. We show that hydrogen can be produced by reforming of glycerol, sorbitol, glucose or sucrose in water at a low temperature over supported metal catalysts. A thermodynamic analysis that forms the basis of the process compares aqueous phase reforming of polyols with steam reforming of alkanes. Catalyst screening involving different noble metals and different supports indicates that alumina supported platinum catalysts are effective for hydrogen production by aqueous phase reforming of polyols. In an attempt to achieve high hydrogen yields, the effects of operating temperature, pressure, and nature of the feed are studied. Higher operation temperatures favor higher hydrogen yields while hydrogen production is strongly inhibited by high system pressure. Short chain polyols have better hydrogen selectivities than long chain polyols. An effort is made to show that valuable chemicals can be derived from polyols. Glycerol and other polyols are potential sources of value-added chemicals, such as 1,2-propanediol, a major commodity chemical now obtained from petroleum derived propylene. It can be generated by an alternative renewable route through hydrogenolysis of biodiesel-derived glycerol. The effects of hydrogenolysis conditions such as reaction temperature, hydrogen pressure, water content in the feed and catalysts are evaluated. Both high temperature and high hydrogen pressure favor 1,2-propanediol formation. This research discusses biorefinery processes and shows how biosustainable polyols can be used as a source of hydrogen and of chemicals. The development of the aqueous phase reforming of polyols to produce hydrogen and the hydrogenolysis of polyols to generate value-added chemicals build a foundation for further research