Effect of Support Properties on Selective Butanediols Production from Erythritol using Ir/ReO_x Catalysts

Abstract

This study reports the selective obtaining of butanediols (BDO), widely used in the polymer and synthetic rubber industry, by CÀ O hydrogenolysis of erythritol. The effect of the support on catalytic activity and selectivity to BDO was exhaustively studied using Ir/ReO x catalysts supported on SiO 2 , Al 2 O 3 , activated carbon, CeO 2 , TiO 2 and ZrO 2 . The catalysts were thoroughly characterized and it was found that the physicochemical, redox and acidic properties of the supports notably influenced the metal dispersion, reducibility of the species and particle sizes.The most active and selective catalyst was Ir/ReO x /TiO 2 (maximum BDO yield of 53 %), favoring CÀ O hydrogenolysis and minimizing CÀ C scissions and dehydration reactions. This superior performance was attributed to the formation of small clusters with an intimate contact between Ir and partially oxidized Re species (mainly Re + IV ) that favors the appropriate adsorption of erythritol on ReO 2 and the further interaction with H 2 adsorbed on Ir 0 to render BDO.

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

“…The TiO 2 support has also been proposed to have a role in the suppression of the overreduction of Re species, leading to the interaction between an erythritol molecule and catalytic active site. 220,221 Fig. 27 shows the conversion and selectivity as a function of reaction time for erythritol hydrogenolysis over Ir-ReO x /rutile TiO 2 (4 wt% Ir, Re/Ir = 0.25) at 353 K. 222 The reaction temperature (353 K) for the Ir-ReO x catalyst was clearly lower than that (453 K) for the Cu catalyst, which was due to the very high activity of Ir-ReO x catalysts for C-O hydrogenolysis of various polyfunctionalized compounds such as sugars, 223,224 sugar alcohols, 222,[225][226][227] and cyclic ones.…”

“…The TiO 2 support has also been proposed to have a role in the suppression of the over-reduction of Re species, leading to the interaction between an erythritol molecule and catalytic active site. 220,221…”

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

“…Recently, studies have demonstrated that the activity of multifunctional polyol HDO catalysts containing oxophilic metals (e.g., ReO x ) and metallic sites (e.g., Ir) can be affected by the redox and acidic properties of catalyst supports . The effect of the support was studied by varying the TiO 2 support to ZrO 2 , SiO 2 , and Al 2 O 3 as shown in Table , entries 1 and 6–8.…”

“…Recently, studies have demonstrated that the activity of multifunctional polyol HDO catalysts containing oxophilic metals (e.g., ReO x ) and metallic sites (e.g., Ir) can be affected by the redox and acidic properties of catalyst supports. 24 The effect of the support was studied by varying the TiO 2 support to ZrO 2 , SiO 2 , and Al 2 O 3 as shown in Table 1, entries 1 and 6−8. TiO 2 supported MoO X -Pd gave the highest THF rate of formation (0.22 mol•mol co −1 •min −1 ) and THF selectivity compared to MoO X -Pd supported on ZrO 2 , Al 2 O 3 , and SiO 2 .…”

“…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 .…”