Hydrogenolysis of glycerol to 1,2‐propanediol in a continuous flow trickle bed reactor

Abstract

BACKGROUND Hydrogenolysis of glycerol to glycols in continuous flow three phase reactors is of practical importance due to the need to give value to huge amounts of surplus glycerol. Thermodynamic and kinetic aspects must be revised for a proper design. The system was studied in a trickle‐bed reactor using copper chromite and Cu/Al2O3 as catalysts. RESULTS Phase equilibrium and flow pattern were verified. Solid, liquid and gas phases were present, with the liquid phase in ‘trickling’ flow. Catalysts were characterized by inductively coupled plasma (ICP), nitrogen sortometry, X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), temperature programmed reduction (TPR) and pyridine thermal programmed desorption (TPD). The average reaction rate was found to be practically constant under different process conditions. A theoretical analysis indicated that the resistance to the transfer of hydrogen from the gas to the liquid phase dominated the overall kinetics. Selectivity to 1,2‐propanediol varied with temperature, with a maximum at 230 °C (97%). Selectivity was a function of the catalyst acidity. When the pressure was increased the selectivity to 1,2‐propanediol was increased, up to 97% at 14 bar. Higher pressures did not modify this value. CONCLUSIONS Optimum reaction conditions for maximum selectivity to 1,2‐propanediol with Cu‐based catalysts are 230 °C and 14 bar. System kinetics are, however, dominated by the gas–liquid mass transfer resistance. © 2017 Society of Chemical Industry

Mechanism Analysis and Kinetic Modelling of Cu NPs Catalysed Glycerol Conversion into Lactic Acid

“…A large number of surplus glycerol processing methods have already been proposed such as hydrogenolysis to 1,2-propanediol [3], dehydration to acrolein [4,5], oxydehydration to acrylic acid [6], chlorination to epichlorohydrin [7], carbonation to glycerol carbonate [8]. One of the most promising chemicals, which can be obtained from glycerol, is lactic acid known as 2-hydroxypropanoic acid.…”

Transition Metal Catalysts for the Glycerol Reduction: Recent Advances

“…Copper chromite and Cu/Al 2 O 3 catalysts had very different physical and chemical properties; however, in the hydrogenolysis of GL, carried out in a trickle-bed reactor, 97 % selectivity of 1,2-PD and complete conversion of GL were obtained for both catalysts at 503 K and 14 bar H 2 . [174] This comparable activity would be related to the presence of Cu 0 species in both catalysts, as seen by XPS. The authors observed also that higher temperatures produced a decrease in the selectivity to 1,2-PD due to the formation of different by-products: minor alcohols in presence of Cu/Al 2 O 3 , and HAc and 3-HPA in the case of copper chromite.…”

“…Copper chromite and Cu/Al 2 O 3 catalysts had very different physical and chemical properties; however, in the hydrogenolysis of GL, carried out in a trickle‐bed reactor, 97 % selectivity of 1,2‐PD and complete conversion of GL were obtained for both catalysts at 503 K and 14 bar H 2 [174] . This comparable activity would be related to the presence of Cu 0 species in both catalysts, as seen by XPS.…”

“…This comparable activity would be related to the presence of Cu 0 species in both catalysts, as seen by XPS. The authors observed also that higher temperatures produced a decrease in the selectivity to 1,2‐PD due to the formation of different by‐products: minor alcohols in presence of Cu/Al 2 O 3 , and HAc and 3‐HPA in the case of copper chromite [174] . In the range 473–493 K, a catalyst consisting of Cu‐Cr oxides with NiO supported on γ‐Al 2 O 3 led to an increased selectivity for 1,2‐PD, in spite of HAc [167] .…”

“…The authors observed also that higher temperatures produced a decrease in the selectivity to 1,2-PD due to the formation of different by-products: minor alcohols in presence of Cu/Al 2 O 3 , and HAc and 3-HPA in the case of copper chromite. [174] In the range 473-493 K, a catalyst consisting of Cu-Cr oxides with NiO supported on γ-Al 2 O 3 led to an increased selectivity for 1,2-PD, in spite of HAc. [167] The reactivity of copper chromite catalyst in the hydrogenolysis of GL was also studied by DFT showing that the interactions with the substrate were due to both Cr-O and hydrogen bonds.…”