LAUSR

Abstract This study focuses on mechanism and kinetics in catalytic hydrodeoxygenation of palmitic acid under hydrothermal conditions (310, 340 and 370 °C), in which 5% Pt/C serves as catalyst and formic acid is used for in-situ H2 generation. The major products were pentadecane as decarboxylation product, 1-hexadecanol and hexadecane from hydrogenation reaction. Reverse trends in the yields of decarboxylated and hydrogenation compounds along with reaction time suggests a competitive adsorption on catalyst active sites for paths of hydrogenation and decarboxylation. A kinetic model based on the reaction network of hydrodeoxygenation of palmitic acid clearly captures all of the trends in the data and fits the temporal variation of all major products. Results reveal that all adsorption equilibrium constants of 1-hexadecanol on catalyst are higher than 1000 L/mol, indicating it acts as a decarboxylation inhibitor. Reaction rate analysis illustrates decarboxylation is the main deoxygenation pathway even in the presence of in-situ H2. Sensitivity analysis at 340 °C demonstrated that decarboxylation and hydrogenation of palmitic acid were highly affected by each other. TEM characterization confirms the good hydrothermal performance of the Pt/C catalyst and experiment at 340 °C for 90 min led to the growth of Pt average particle size from 1.72 nm to 2.81 nm. Diffusion limitation calculation suggests the influence of micropore diffusion and mass transfer resistance on heterogeneous catalytic reaction is negligible in the tested experimental condition.