Selective hydrogenolysis of glycerol to propylene glycol in a continuous flow trickle bed reactor using copper chromite and Cu/Al2O3 catalysts

Abstract

CATALYSTS. The glycerol hydrogenolysis reaction was performed in a continuous flow trickle bed reactor using a water glycerol feed and both copper chromite and Cu/Al 2 O 3 catalysts. The commercial copper chromite had a higher activity than the laboratory prepared Cu/Al 2 O 3 and was used for most of the tests. Propylene glycol was the main product with both catalysts, acetol being the main by-product. It was found that temperature is the main variable influencing the conversion of glycerol. When the state of the glycerol-water reactant mixture was completely liquid, at temperatures lower than 190 °C, conversion was low and deactivation was observed. At reaction temperatures of 210-230 °C the conversion of glycerol was complete and the selectivity to propylene glycol was stable at about 60-80% all throughout the reaction time span of 10 h, regardless of the hydrogen pressure level (1 to 20 atm). These optimal values could not be improved significantly by using other different reaction conditions or increasing the catalyst acidity. At higher temperatures (245-250 °C) the conversion was also 100%. Under reaction conditions at which copper chromite suffered deactivation, light by-products and surface deposits were formed. The deposits could be completely burned at 250 °C and the catalyst activity fully recovered.

The Joint Synthesis of 1,2-Propylene Glycol and Isopropyl Alcohol by the Copper-Catalyzed Hydrogenolysis of Solketal

“…1 While the noble metal-based catalysts have turned out to be the most promising for the latter purpose, 2,3 the copper-based catalysts seem to be the best choice for the hydrogenolysis of glycerol into 1,2-PG because of the relative low costs and efficient performance. High yields (up to 98%) and selectivities (up to 99.6%) in glycerol hydrogenolysis have been reported for Cu, 4−10 Cu−B, 11,12 Cu−Cr, 5,6,10,13 Cu−Mg, 14 Cu−Pd, 15 and Cu−Zn 16,17 catalysts.…”