First principles modeling of deoxygenation chemistry on bi-metallic phosphides and zeolites nanosheets

With the dwindling availability of petroleum, focus has shifted to renewable energy sources such as lignocellulosic biomass. Cellulose and hemicellulose are highly utilized components of biomass, and on the other hand, lignin is a plentiful, under-utilized component of the lignocellulosic biomass. Hence, utilization of the lignin component is necessary for the realization of an economically sustainable biorefinery model. Once depolymerized, lignin has the potential to replace petroleum-derived molecules. Further, a catalyst is capable of selectively removing the oxygen atoms without hydrogenating the aromatic components would be valuable. Bimetallic phosphides and zeolites are capable of selectively cleaving CAROMATIC–O bonds from aromatic compounds. In the present study, the applications of a bimetallic phosphides (FeMoP, RuMoP and NiMoP) for CAROMATIC–O bond cleavage and hydrogenation of C=O and C=C bond in the aromatic model compounds (Phenol, furfural, cinnamaldehyde, and CO2) were examined. The Fe:Mo ratio was varied in FeX Mo2−X P catalysts (0.88 to 1.55) to investigate the effect of catalyst acidity and hydrogenolysis capability via first principle calculations. The most acidic material was most selective for phenol to benzene. Further, combination of different transition metals with phosphorus were tested for hydrogenolysis and hydrogenation mechanism of phenol. Additionally, composition effect in RuXMo2−XP (X = 0.8, 1.0 and 1.2) have investigated for furfural and cinnamaldehyde hydrogenation. It was found that tuning in metal combination and composition results in control of binding energy and activation energy barrier which tune the selectivity for desire reaction and reaction pathway. Alternatively, highly active MWW-zeolite nanosheets have recently been explored for depolymerization in lignin. First, binding strength of different lignin dimers (phenolic and non-phenolic) was studied in terms of binding energy and binding mode over different terminated zeolite surface as a function of temperature and solvent. The optimized binding structure of lignin dimers were further considered to study the hydrogenolysis pathways over Al- and Sn-substituted MWW zeolite nanosheets. Generally, it was found that fully hydroxyl terminated surface, phenolic dimers and higher temperature in methanol pro- motes higher binding energy. Moreover, Al-substituted zeolite nanosheet resulted in lowering activation energy barriers significantly to cleave β-O-4 Linkages in Lignin dimers