A Mechanistic Study of Polyol Hydrodeoxygenation over a Bifunctional Pt-WOx/TiO2 Catalyst

Recent Advances in the Catalytic Hydroconversion of 5-Hydroxymethylfurfural to Valuable Diols

Biomass, a globally available resource, is a promising alternative feedstock for fossil fuels, especially considering the current energy crisis and pollution. Biomass-derived diols, such as 2,5-bis(hydroxymethyl)furan, 2,5-bis(hydroxymethyl)-tetrahydrofuran, and 1,6-hexanediol, are a significant class of monomers in the polyester industry. Therefore, the catalytic conversion of biomass to valuable diols has received extensive research attention in the field of biomass conversion and is a crucial factor in determining the development of the polyester industry. 5-Hydroxymethylfurfural (HMF) is an important biomass-derived compound with a C6-furanic framework. The hydroconversion of HMF into diols has the advantages of being simple to operate, inexpensive, environmentally friendly, safe, and reliable. Therefore, in the field of diol synthesis, this method is regarded as a promising approach with significant industrialization potential. This review summarizes recent advances in diol formation, discusses the roles of catalysts in the hydroconversion process, highlights the reaction mechanisms associated with the specificities of each active center, and provides an outlook on the challenges and opportunities associated with the research on biomass-derived diol synthesis.

Tungsten oxide decorated silica-supported iridium catalysts combined with HZSM-5 toward the selective conversion of cellulose to C6 alkanes

Herein, WO_x-decorated Ir/SiO₂ (W/Ir = 0.06) and HZSM-5 were coupled to selectively convert microcrystalline cellulose (MCC) into C₆ alkanes. A 92.8% yield of liquid alkanes including an 85.3% yield of C₆ alkanes was produced at 210 °C. Cellulose hydrolysis, glucose hydrogenation and sorbitol hydrodeoxygenation were integrated to produce alkanes via a sorbitol route. Ir-WO_x/SiO₂ showed high performance for hydrogenation and hydrodeoxygenation reactions after hydrolysis catalyzed by HZSM-5. The intimate contact between WO_x and Ir enhanced the synergistic interaction through the electron transfer from Ir to WO_x. The interaction strengthened the reduction capability of Ir for hydrogenations, as well as improved the adsorption and activation of C-O bonds on reduced WO_x for deoxygenations. The monotungstate WO_x species provided moderate Lewis acids to cooperate with Ir to accelerate hydrodeoxygenations with alleviated retro-aldol condensation to yield more C₆ alkanes.

Reduction of NOx by H2 on WOx-Promoted Pt/Al2O3/SiO2 Catalysts Under O2-Rich Conditions

This work addresses the reduction of NOx by H2 under O2-rich conditions using Al2O3/SiO2-supported Pt catalysts with different loads of WOx promotor. The samples were thoroughly characterised by N2 physisorption, temperature-programmed desorption of CO, scanning electron microscopy, X-ray diffraction, laser raman spectroscopy, X-ray photoelectron spectroscopy and diffuse reflectance infrared fourier transform spectroscopy with probe molecule CO. The catalytic studies of the samples without WOx showed pronounced NOx conversion below 200 °C, whereas highest efficiency was related to small Pt particles. The introduction of WOx provided increasing deNOx activity as well as N2 selectivity. This promoting effect was referred to an additional reaction path at the Pt-WOx/Al2O3/SiO2 interface, whereas an electronic activation of Pt by strong metal support interaction was excluded.

Graphic Abstract

Enhancing Hydrodeoxygenation of Bio-oil via Bimetallic Ni-V Catalysts Modified by Cross-Surface Migrated-Carbon from Biochar

Aromatics from selective hydrodeoxygenation (HDO) of biomass-derived bio-oil are an ideal feedstock for replacing industrial fossil products. In this study, biochar-modified Hβ/Ni-V catalysts were prepared and tested in the atmospheric HDO of guaiacol and bio-oil to produce aromatics. Compared with unmodified Hβ/Ni-V, higher HDO activity was achieved in catalysts with all kinds of biochar modifications. Especially, the pine nut shell biochar (PB)-modified PB-Hβ-8/Ni-V showed the highest selectivity to aromatics (69.17%), mainly including benzene and toluene. Besides, under the conditions of 380 °C and weight hourly space velocity (WHSV) of 0.5 h^-1, the cleavage of C_Ar-OH (C_Ar means the carbon in the benzene ring) was promoted to form more aromatics. Moreover, great recyclability (58.77% aromatics for the reactivated run-3 test) and efficient HDO of bio-oil (44.9% aromatic yield) were also achieved. Based on the characterization results, the enhanced aromatic selectivity of PB-Hβ-8/Ni-V was attributed to the synergetic effect between PB and Hβ/Ni-V. In detail, a stable surface migrated-carbon layer was formed on Hβ/Ni-V via the metal catalytic chemical vapor deposition (CVD) process of the pyrolysis PB volatiles. Simultaneously, a carbothermal reduction driven by the migrated-carbon took place to decorate the surface metals, obtaining more Ni⁰ and V³⁺ active sites. With this synergism, increased Ni⁰ sites promoted H₂ adsorption and dissociation, which improved the hydrogenation activity. Furthermore, the higher affinity of the reactant and increased oxygen vacancies both contributed to enhancing the selective surface adsorption of oxygenous groups and the cleavage of the C_Ar-OH bond, thus improving the deoxygenation activity. Therefore, the HDO activity was improved to form more target aromatics over biochar-modified catalysts. This work highlighted a potential avenue to develop economic and environmental catalysts for the upgrading of bio-oil.