Elucidation of the Catalytic Pathway for the Direct Conversion of Furfuryl Alcohol into γ-Valerolactone over Al2O3-SiO2 Catalysts.

The one-pot conversion of furfuryl alcohol (FA) into GVL was investigated over the sol-gel-synthesized Al2O3-SiO2 (AlSi) catalysts with various Al2O3 loadings (0.2-10 wt %) and commercial zeolites including MFI-1, H-ZSM5, H-beta, and HY-15 in a batch reactor under mild reaction conditions (130 °C, 1 bar N2, and 15-120 min). The reaction pathways depend largely on the acid properties of the catalysts, especially the types of Bronsted (B) and Lewis (L) acid sites. A tandem alcoholysis/hydrogenation/cyclization sequence is dominant on the AlSi catalysts (Al ≥ 4%) and all the zeolites except MFI-1, resulting in complete conversion of FA and GVL with an yield 64-75% with IPL as the major side-product, regardless of the differences in their B/L ratios 0.06-1.35. In the absence of B acid sites (i.e., 0.2% AlSi and MFI-1 catalysts), FA could be straightforwardly converted into GVL on the weak Lewis acid sites from the isolated silanol groups using 2-propanol as a hydrogen source. The AlSi catalysts are promising tunable catalysts for FA conversion with good recyclability.

Room Temperature Nanographene Production via CO2 Electrochemical Reduction on the Electrodeposited Bi on Sn Substrate.

Electrochemical reduction of carbon dioxide (CO2RR) to crystalline solid carbon at room temperature is challenging, but it is a providential CO2 utilization route due to its indefinite storage and potential applications of its products in many advanced technologies. Here, room-temperature synthesis of polycrystalline nanographene was achieved by CO2RR over the electrodeposited Bi on Sn substrate prepared with various bismuth concentrations (0.01 M, 0.05 M, and 0.1 M). The solid carbon products were solely produced on all the prepared electrodes at the applied potential -1.1 V vs. Ag/AgCl and were characterized as polycrystalline nanographene with an average domain size of ca. 3-4 nm. The morphology of the electrodeposited Bi/Sn electrocatalysts did not have much effect on the final structure of the solid carbon products formed but rather affected the CO2 electroreduction activity. The optimized negative potential for the formation of nanographene products on the 0.05Bi/Sn was ca. -1.5 V vs. Ag/AgCl. Increasing the negative value of the applied potential accelerated the agglomeration of the highly reactive nascent Bi clusters in situ formed under the reaction conditions, which, as a consequence, resulted in a slight deviation of the product selectivity toward gaseous CO and H2 evolution reaction. The Bi-graphene composites produced by this method show high potential as an additive for working electrode modification in electrochemical sensor-related applications.

Lignin Valorization by Cobalt-Catalyzed Fractionation of Lignocellulose to Yield Monophenolic Compounds.

Herein, a catalytic reductive fractionation of lignocellulose is presented using a heterogeneous cobalt catalyst and formic acid or formate as a hydrogen donor. The catalytic reductive fractionation of untreated birch wood yields monophenolic compounds in up to 34 wt % yield of total lignin, which corresponds to 76 % of the theoretical maximum yield. Model compound studies revealed that the main role of the cobalt catalyst is to stabilize the reactive intermediates formed during the organosolv pulping by transfer hydrogenation and hydrogenolysis reactions. Additionally, the cobalt catalyst is responsible for depolymerization reactions of lignin fragments through transfer hydrogenolysis reactions, which target the ß-O-4' bond. The catalyst could be recycled three times with only negligible decrease in efficiency, showing the robustness of the system.