Electrodeposited Ni-rich Ni-Pt mesoporous nanowires for selective and efficient formic acid-assisted hydrogenation of levulinic acid to γ-valerolactone

Abstract

In pursuit of friendlier conditions for the preparation of high-value biochemicals, we developed a catalytic synthesis of -valerolactone by levulinic acid hydrogenation with formic acid as the hydrogen source. Both levulinic and formic acid are intermediate products in the biomass transformation processes. The objective of the work is two-fold; development of a novel approach for milder synthesis conditions to produce -valerolactone and the reduction of the economic cost of the catalyst. Ni-rich Ni-Pt mesoporous nanowires were synthesized in an aqueous medium using a combined hard-soft template-assisted electrodeposition method, in which porous polycarbonate membranes controlled the shape, and the pluronic P-123 copolymer served as the porogen agent. The electrodeposition conditions selected favored nickel deposition and generated nanowires with nickel percentages above the 75 at. %. The increase in deposition potential favored nickel deposition. However, it was detrimental for the porous diameter, because the mesoporous structure is promoted by the presence of the platinum-rich micelles near the substrate, which is not favored at the more negative potentials. The prepared catalysts promoted the complete transformation to -valerolactone in a yield of around 99% and proceeded with the absence of by-products. The couple temperature and reaction time were optimized considering the energy cost. The threshold operational temperature was established at 140 ºC, at which, 120 minutes were sufficient for attaining the complete transformation. Working temperatures below 140 ºC rendered the reaction completion difficult. The Ni78Pt22 nanowires exhibited excellent reusability, with minimal nickel leaching into the reaction mixture, whereas those with higher nickel contents showed corrosion.