Bio-oil produced via fast pyrolysis contains an appreciable quantity of water. Typical acid catalysts used to purify and stabilize bio-oil become solvated and are greatly inhibited by the presence of water. The development of a water tolerant acid catalyst would play an integral role in the effective stabilization of bio-oil and in the viability of bio-oil as an alternative fuel source. The proposed design of this study is to use a heterogeneous catalyst comprised of dispersed catalytic sulfonic acid active sites using high surface area mesoporous silica (SBA-15) as a support. The surface of the SBA-15 will be modified with organic functional groups in order to make the surface and local environment adjacent to the sulfonic acid moiety more hydrophobic. It is anticipated that the grafting of organic moieties on the surface of the SBA-15 will reduce solvation of the active site of the catalyst and in turn reduce inhibition by water that has been introduced upon formation of the bio-oil as a result of dehydration. Solution thermodynamics shows a strong correlation between the increasing hydrophobicity of inner-sphere and outer-sphere modifications on sulfonic acid catalysts and the decreasing solvation of the active site of the catalyst and the mesoporous silica support.
