A Kinetic and Mass Transfer Model for Glycerol Hydrogenolysis in a Trickle-Bed Reactor

Abstract

A detailed model of glycerol hydrogenolysis in a trickle-bed reactor is presented that includes a mechanistically based kinetic rate expression, energy transport, mass transport across the gas-liquid and liquid-solid interfaces, intraparticle catalyst mass transfer, and partial wetting of the bed. Optimal kinetic parameters for the glycerol hydrogenolysis rate expression were determined via nonlinear regression analysis on the basis of experiments conducted in a laboratory-scale trickle-bed reactor over a broad range of operating conditions. Model predictions agree well with experimental data and accurately predict trends in reactor performance with liquid flow rate, temperature, hydrogen pressure, and base promoter concentration. The model is thus a useful tool for predicting laboratory reactor performance and for design of commercial-scale trickle-bed systems. IntroductionGlycerol (1,2,3-propanetriol, herein GO) has become an attractive feedstock for chemicals production because it is readily available as the major byproduct from biodiesel production. 1 In particular, GO hydrogenolysis to propylene glycol (PG) has received attention in both patent and open literature, because PG is a thousand kilo-tonne commodity with applications as a polymer building block, emollient in consumer products, and nontoxic replacement for ethylene glycol (EG). Among numerous patents describing GO conversion to PG, Casale et al. 1 used sulfide-modified ruthenium to achieve 75% PG yield; Schuster et al. 2 used a mixed metal (Cu/Co/Mn/Mo) catalyst with heteropolyacids that gave 96% PG yield, and Werpy et al. 3 demonstrated >80% selectivity to PG over a Ni/ Re catalyst. The open literature contains several studies of catalysts for PG formation from GO, including bimetallic Pt/Ru and Au/Ru catalysts at neutral and elevated pH, 4 carbon-supported Ru and

Nanostructured Metal Catalysts for Selective Hydrogenation and Oxidation of Cellulosic Biomass to Chemicals

“…Besides, glycerol showed an endothermic adsorption on Cu surface. A simplified model describing the adsorption of glycerol, glyceraldehyde and acetol on the same site was proposed by Xi and co‐workers . With negligible adsorption of OH − as the promoter and 1,2‐PDO, this model fitted the experimental data very well in the range of 180–200 °C.…”

Glycerol transformation to value added C3 diols: reaction mechanism, kinetic, and engineering aspects

“…A catalyst composed of Co, Pd and Re supported on activated carbon was used for the kinetic study reported by Xi et al employing a trickle‐bed reactor at a temperature range of 453–475 K and hydrogen pressures 3.3–13.3 MPa . The main reaction steps included (1) dehydrogenation of glycerol to adsorbed glyceraldehyde species, (2) rearrangement and dehydration to a second adsorbed intermediate analogous to pyruvaldehyde (see Figure ), and (3) hydrogenation of the latter to form 1,2‐propanediol.…”

“…The parity plot showed good agreement between the experimental and predicted data especially at the lower concentration range. The activation energy for glycerol conversion to 1,2-propanediol found to be 54.2 kJ/mol ( 76 The main reaction steps included (1) dehydrogenation of glycerol to adsorbed glyceraldehyde species, (2) rearrangement and dehydration to a second adsorbed intermediate analogous to pyruvaldehyde (see Figure 8), and (3) hydrogenation of the latter to form 1,2-propanediol. The final rate expression (Table 2, entry 3) was simplified and included information about glycerol, hydroxide promoter, and hydrogen.…”

Kinetic modeling of Pt/C catalyzed aqueous phase glycerol conversion with in situ formed hydrogen

“…Although several computational studies using density functional theory (DFT) have provided insights into possible activation modes of the C‐C, C‐H, and O‐H bonds of polyols (such as glycerol and EG) on selected metal catalysts, there is a lack of reliable experimental investigations into the intrinsic kinetics of aqueous phase conversion of polyols. Further, while the kinetics of catalytic polyol hydrogenolysis in aqueous medium has been studied in the presence of externally added hydrogen, no such studies exist for tandem catalysis without adding hydrogen from external sources.…”