Simultaneous production of lactate and formate from glycerol and carbonates over supported Pt catalysts

Abstract

Glycerol and carbonates (used as CO2 sources) were simultaneously converted to carboxylic acid salts under mild hydrothermal media over supported Pt catalysts. The dehydrogenation of glycerol produced lactate (LA); at the same time, hydrogen molecules released from glycerol were effectively transferred to reduce carbonate or bicarbonate ions to formate (FA). Several reaction parameters, including temperature, time, glycerol and carbonate concentration, water amount, catalyst loading, and CO2 source were evaluated. Under the optimized reaction conditions, ~50% yield of LA from glycerol and ~26% yield of FA from potassium carbonate were achieved concomitantly over Pt/γ-Al2O3 catalyst. Importantly, this was done without using external H2 or additional strong base. The textural, structural, and chemical properties of the catalysts were evaluated using N2 adsorption–desorption, powder X-ray diffractometry (PXRD), inductively coupled plasma-atomic emission spectrometry, scanning transmission electron microscopy (STEM), temperature programmed reduction, and temperature programmed desorption analysis. The catalyst was reused for four consecutive cycles with little variation in catalytic activity and product distribution. Used catalysts were further characterized using, PXRD, STEM, and X-ray photoelectron spectral analysis to better understand the structural and chemical changes that occurred in the recycled catalysts, and the factors governing change in the catalytic activity. A plausible reaction pathway was proposed based on the catalytic results and the product distribution data obtained.