Phosphoric acid enhancement in a Pt-encapsulated Metal-Organic Framework (MOF) bifunctional catalyst for efficient hydro-deoxygenation of oleic acid from biomass

The Pt-doped H3PO4@MIL-101Cr catalysts, with a series of phosphoric acid concentrations, were successfully synthesized using the double-solvent method for efficient hydrodeoxygenation (HDO) of fatty acid. The phosphoric acid modification of 1%Pt/MIL-101 enhanced the catalytic performance of HDO conversion of oleic acid in the gas phase with a 1.5-11 times higher turnover frequency (TOF) over metal site compared to the original Pt/MIL-101 catalyst. Moreover, the increase in the number of the moderate acid sites facilitates the decarbonylation/carboxylation compared to the hydrodeoxygenation reaction, based on the gradual increase in the ratio of nC(17)/nC(18) due to the significant increase of the moderated Bronsted acid site. The FE-TEM and CO chemisorption measurements demonstrated that the Pt nanoparticles were highly dispersed on the support, and that they shifted to a larger size distribution due to the competitive adsorption between the acid site and metal site, with diameters in the range of 1.72-3.89 nm. The catalytic stability of a phosphoric acid modified-catalyst was maintained above 75% for 24 h of the HDO reaction. The application of phosphoric acid - MOF-based catalysts for the HDO of a model fatty acid compound was demonstrated for the first time, to the best of our knowledge, exhibiting an efficient catalyst system for HDO in a gas-phase process. (C) 2020 Elsevier Inc. All rights reserved.