Hydrogenation of lactic acid to propylene glycol over copper-containing catalysts

Abstract

Catalytic properties of different copper-containing catalysts synthesized from different precursors were studied in the hydrogenation of lactic acid at mild conditions. The most active catalyst was found to be chrysocolla-like copper hydroxysilicate with the copper loading of about 50 at%. At the optimal reaction conditions (T = 473 K, WHSV = 0.08 h -1 ), 95% conversion of lactic acid over this catalyst and 65% selectivity to 1,2-propylene glycol were achieved. The effect of the weight hourly space velocity (WHSV) on the lactic acid conversion and selectivity to propylene glycol was studied. It is found that the formation of propylene glycol and propanoic acid as a byproduct proceeds via parallel pathways.

Catalytic conversion of lactic acid into propylene glycol over various metals supported on silica

“…Three metal (Ag, Co, Cu) catalysts showed no catalytic activity for hydrogenation of lactic acid, while Ni, Pt, and Ru supported on silica showed pretty high activities. Parmon et al [23] reported liquidphase hydrogenation of lactic acid to propylene glycol over silica-supported copper catalyst. The lactic acid hydrogenation over the 14 wt% Cu/SiO 2 catalyst leads to the 45% conversion of lactic acid with 50% selectivity of propylene glycol at the hydrogen pressure of 0.1 MPa.…”

Hydrogenation of Lactic Acid to 1,2‐Propanediol over Ru‐Based Catalysts

“…The main challenge in establishing a catalytic process for the hydrogenation of LA to 1,2‐PDO is to reduce the carboxylic acid group, while preserving the α‐hydroxy moiety. Given the intrinsic difficulty to reduce carboxylic acids with H 2 , harsh conditions are typically required to achieve high conversion, which usually has the drawback of also promoting undesired hydrogenolysis side reactions. The development of an active catalyst for selective hydrogenation of LA to 1,2‐PDO under mild reaction conditions is highly desired …”

“…Neat lactic acid could be successfully reduced in the presence of a Re black at 150 °C and 258 bars of H 2 , yielding up to 80 % of 1,2‐PDO . The hydrogenation of LA in the gas phase has been reported using a Cu‐based catalyst at temperatures between 160 °C and 220 °C, resulting in high 1,2‐PDO yields . Supported Ru has been recently identified as a promising catalyst for the aqueous‐phase hydrogenation of carbonyl‐containing biomass‐derived oxygenates including carboxylic acids .…”

“…[10] The reductivet ransformation of LA to 1,2-propanediol (1,2-PDO) through catalytic hydrogenation is regarded as an attractive green alternative to the current process in which 1,2-PDO is obtainedt hrough the hydration of propylene oxide. [11] The main challenge in establishing ac atalytic process for the hydrogenation of LA to 1,2-PDO is to reduce the carboxylic acid group, while preserving the a-hydroxy moiety.G iven the intrinsic difficulty to reduce carboxylic acids with H 2 ,h arsh conditions are typically required to achieve high conversion, [12] which usually has the drawback of also promoting undesired hydrogenolysis side reactions. The development of an active catalystf or selective hydrogenation of LA to 1,2-PDO under mild reaction conditions is highly desired.…”

“…[14] The hydrogenation of LA in the gas phase has been reported using aC ubased catalyst at temperatures between 160 8Ca nd 220 8C, resulting in high 1,2-PDO yields. [12,15] Supported Ru has been recently identified as ap romising catalystf or the aqueous-phase hydrogenation of carbonyl-containing biomass-derived oxygenatesi ncluding carboxylic acids. [16] The activity of Ru can be promoted by Sn or Mo to enablet he selective hydrogenation of carboxylic acids and their esters.…”