Kinetics Study of the Hydrodeoxygenation of Xylitol over a ReOx-Pd/CeO2 Catalyst

Abstract

In this study, we elucidate the reaction kinetics for the simultaneous hydrodeoxygenation of xylitol to 1,2-dideoxypentitol and 1,2,5-pentanetriol over a ReOx-Pd/CeO2 (2.0 weight% Re, 0.30 weight% Pd) catalyst. The reaction was determined to be a zero-order reaction with respect to xylitol. The activation energy was elucidated through an Arrhenius relationship as well as non-Arrhenius kinetics. The Arrhenius relationship was investigated at 150–170 °C and a constant H2 pressure of 10 bar resulting in an activation energy of 48.7 ± 10.5 kJ/mol. The investigation of non-Arrhenius kinetics was conducted at 120–170 °C and a sub-Arrhenius relation was elucidated with activation energy being dependent on temperature, and ranging from 10.2–51.8 kJ/mol in the temperature range investigated. Internal and external mass transfer were investigated through evaluating the Weisz–Prater criterion and the effect of varying stirring rate on the reaction rate, respectively. There were no internal or external mass transfer limitations present in the reaction.

Hydrodeoxygenation of potential platform chemicals derived from biomass to fuels and chemicals

“…147 In contrast, ReO x -Pd/CeO 2 catalysts, in which Pd species have the same role as Au and Ag to reduce Re, gave the saturated products through the high hydrogenation activity of Pd. [151][152][153][154] This reaction system is called "DODH + hydrogenation", and the reaction scheme is shown in Fig. 13.…”

Rhenium – A Tuneable Player in Tailored Hydrogenation Catalysis

“…Due to the selectivity of rhenium‐based catalysts towards the hydrogenolysis of C−O bonds rather than C−C bonds, bimetallic catalysts of general composition M−ReO x (M=noble metal) have been studied for the hydrogenolysis of bio‐derived polyols such as glycerol [66] . Silica‐supported Rh−ReO x , Ru−ReO x , Pt−ReO x , Ir−ReO x and Pd−ReO x were evaluated in this reaction by Amada et al., [67] where Rh−ReO x was the most active, yet Ir−ReO x had the highest selectivity to the desired product 1,3‐propanediol ‐ interestingly, Pd−ReO x /SiO 2 showed no activity in the hydrogenolysis of glycerol, [67] whereas Pd−ReO x /CeO 2 is reported as active in the hydrodeoxygenation of other polyols, [68,69] indicating an influence of the CeO 2 support [70] . Rh−ReO x was among the first bimetallic catalyst containing ReO x studied by the research group of Tomishige et al.…”

Supported Bifunctional Molybdenum Oxide-Palladium Catalysts for Selective Hydrodeoxygenation of Biomass-Derived Polyols and 1,4-Anhydroerythritol

“…Various heterogeneous catalysts have been reported for the simultaneous HDO of polyols and cyclic ethers. The catalysts are comprised of supported oxophilic metals (e.g., ReO x, WO x ) promoted by noble metals (e.g., Ir, Pd, Rh). ,− Recently, studies have demonstrated the removal of hydroxyls from erythritol over Ir-ReO x /SiO 2 , Ir-ReO x /TiO 2 , Pt-WO x /SiO 2 , and ReO x -Pd/CeO 2 , mainly producing monomer building blocks, such as 1,2-BDO, 1,4-BDO, and 1,3-butanediol (1,3-BDO). ,,,, Furthermore, the single-step transformation of vicinal hydroxyls in 1,4-AHERY to the corresponding alkene (2,5-dihydrofuran (2,5-DHF)) by DODH has been demonstrated over supported ReO x . Researchers have also demonstrate that the addition of Pd to ReO x supported on CeO 2 leads to conversion of 1,4-AHERY to tetrahydrofuran (THF) at 413 K and a hydrogen pressure of 80 bar with 99% selectivity at 38% conversion by simultaneous HDO. , On the basis of kinetic and computational studies, the active sites proposed for the ReO x -Pd/CeO 2 were isolated Re 4+ species formed by the reduction of Re 6+ species in the presence of Pd-dissociated hydrogen atoms. , There has been spectroscopic evidence that the ReO x exists in a mono-oxo (ReO) and a dioxo (OReO) state on the ReO x -Pd/CeO 2 catalyst, which further supports the proposed active sites .…”