Toward Selective Dehydrogenation of Glycerol to Lactic Acid over Bimetallic Pt-Co/CeOx Catalysts

Selective synthesis of lactic acid from bioderived substrates still remains a grand challenge. We reported a series of unique bimetallic Pt-Co/CeOx catalysts, prepared by fractional precipitation method. Strong electronic coupling for Pt-Co is found to enhance activity toward dehydrogenation (C-H bond cleavage) of glycerol, as evidenced from X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) studies of the catalysts. Detectable electroaffinity of PtCo trends to gain electrons from CeOx support; thus some side reactions (such as C-C and C-O bond cleavage) are largely restrained. Such hybridized structures lead to remarkable activity (turnover frequency (TOF) = 1533.9 h(-1)) with good selectivity toward lactic acid (87.7%) and total organic acids (>95%) at 200 degrees C. In addition, the effect of reaction temperature and substrate concentration on the initial reaction rate reveals that dehydrogenation of glycerol possibly follows a dual-site mechanism, where both glycerol and base need to be activated on the bimetallic Pt-Co surface. Furthermore, the plausible reaction pathway is discussed in detail.