from first principles PP-I-1

PP-IV-21Mechanistic Study of Reaction Pathways in Butyl Lactate to PropyleneGlycol Hydrogenolysis over Cu/SiO 2Simonov M.N., Simakova I.L.Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russiasimakova@catalysis.ruA catalytic method starting from lactic acid obtained by fermentation of crude biomass ispromising way of 1,2-propanediol synthesis instead of conventional petroleum-basedper-oxidation process. However it is well known that catalytic hydrogenation of carboxylicacid to corresponding alcohols is a very difficult process, which requires high hydrogenpressure and temperature. For example, the hydrogenation of lactic acid to propylene glycolover Ru-containing catalyst was carried out at 145 bar and 423 K to reach noticeableconversion of lactic acid and selectivity to propylene glycol [1]. Using copper-containingcatalysts permits to reduce hydrogen pressure up to 1 bar, but consecutive dehydrationhydrogenationreaction path occurs under such conditions leading to formation of undesirablepropanoic acid [2]. Possible way to avoid dehydration and thereby to increase selectivity ispreliminary esterification of lactic acid. The goal of the present work is to study kineticpeculiarities of butyl lactate hydrogenolysis in fixed-bed reactor over Cu/SiO 2 catalyst inorder to develop high selective process of propylene glycol synthesis.Hydrogenolysis of butyl lactate was carried out over 45.5wt% Cu/SiO 2 at PH 2 1 bar in thetemperature range from 403 to 493 K. It was observed that increase of temperature leads toincrease of substrate conversion as overall reaction rate grows while selectivity to propyleneglycol decreases due to increase of hydroxyacetone formation. Propanoic acid formation wasnot detected during hydrogenolysis. Effect of residence time on composition of reactionmixture was studied. It was found, that concentration of butyl lactate is decreased andconcentrations of main products are increased with increasing residence time. It isnoteworthy, that ratio between propylene glycol and hydroxyacetone was independent onresidence time and substrate conversion. The data obtained allow assuming that formation ofpropylene glycol and hydroxyacetone is equilibrated thermodynamically and therefore thisequilibrium can be shifted to desired product by slight increase of hydrogen pressure [3].References:[1] Z. Zhang, J. E. Jackson, D. J. Miller, Appl. Catal. A. 219 (2001) 89.[2] M.N. Simonov, I.L. Simakova, V.N. Parmon, React. Kinet. Catal. Lett. 97 (2009) 157.[3] M. Simonov, P. Zaikin, I. Simakova, Appl. Cat. B: Environmental, 119– 120 (2012) 340.306