Reactions of biomass derived oxygenates on metal and carbide surfaces

Biomass is a renewable resource as an alternative to fossil fuels for chemical and fuel production. Through depolymerization, such as hydrolysis and pyrolysis, biomass can be converted to numerous oxygenates, which can be further upgraded into value-added products. This thesis processes a fundamental study to investigate the upgrading of two platform chemicals, furfural and glycerol, which are produced from hemicellulose and triglyceride, respectively. The ring-opening of tetrahydrofurfuryl alcohol (THFA), formed by full hydrogenation of furfural, produces a valuable monomer, 1,5-pentanediol (1,5-PeD). This thesis reveals that the ring-opening of partially hydrogenated furfural to produce 1,5-pentanediol is a promising pathway, which has a lower activation barrier than that from the furfural-THFA-1,5-PeD pathway. The surface with strong interaction with furan ring can enhance the ring-opening reaction. However, a proper binding with the furan ring is also critical to avoid further decomposition. The hydrodeoxygenation (HDO) reaction can convert furfural to 2-methylfuran, a promising fuel additive. A comparison of bimetallic catalysts consisting of 3d transition metal over platinum, 3d/Pt(111) surfaces suggests that the 3d-terminated surfaces with strong oxophilic metal modifier have high HDO activity. However, Pt is a precious metal and the 3d-terminated 3d/Pt(111) is unstable due to the diffusion of the 3d metal. The two drawbacks make 3d/Pt catalysts unpractical for industrial use. Molybdenum carbide (Mo2C) shows Pt-like properties as a substrate and has high diffusion barrier to stabilize the surface 3d atoms, making it an ideal material to replace Pt. The 3d/Mo2C shows similar furfural HDO activity to 3d/Pt(111) with an enhanced stability in both surface science experiment and reactor evaluations. Due to the promising performance of 3d/Mo2C catalysts, they can be utilized in the HDO reaction of glycerol. Glycerol has three C-O bonds, and the selective HDO reaction upgrades glycerol into various products by cleaving different numbers of C-O bonds. The strong oxophilicity makes Mo2C active to break all C-O bonds of glycerol forming propylene. The Cu modifier can reduce the oxophilictiy of the Cu/Mo¬2C surface and products with fewer C-O bonds cleaved are observed as Cu coverage increases.