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Cellulose-derived levulinic acid (LA) can be converted into gamma-valerolactone (GVL), a sustainable platform chemical for the production of bio-based chemicals. However, LA as an organic acid causes severe metal leaching during the heterogeneous hydrogenation of LA to GVL, especially in the presence of water. Various endeavors for preventing metal leaching have focused more on the process and less on the intrinsic nature of catalysts. The aim of this work is to derive a novel metal-leaching-resistant catalyst for the aqueous-phase hydrogenation of LA into GVL by using a nanocomposite containing three components, Ag, ZrO2, and graphene oxide (GO). The AgZrO2GO catalyst without pre-reduction treatment resulted in complete conversion of LA and approximately 100 mol% selectivity to GVL in the aqueous reaction, and metal leaching from the catalyst was completely eliminated. The relationship between the catalytic performance and the distinct physicochemical properties of the catalyst was extensively discussed. [ABSTRACT FROM AUTHOR]

In this work, the reaction mechanism for the conversion of CO2 and H2 to methanol has been researched by density functional theory (DFT). The production of methanol from CO2 and H2 is catalyzed by a univocal bifunctional pincer-type complex trans-RuH2(CO)(dpa) (dpa = bis-(2-diphenylphosphinoethyl)amine). The reaction mechanism includes three continuous catalytic processes: (1) CO2 is converted to formic acid; (2) formic acid is converted to formaldehyde and water; (3) formaldehyde is converted to methanol. By computing the catalytic processes, we have shown that the rate-limiting step in the whole process is the direct cleavage of H2. The calculated largest free energy barrier is 21.6 kcal/mol. However, with the help of water, the free energy barrier can be lowered to 12.7 kcal/mol, which suggests viability of trans-RuH2(CO)(dpa) as a catalyst for the direct conversion of CO2 and H2 to methanol. [ABSTRACT FROM AUTHOR]

Metal leaching is a major issue in efficient production of γ-valerolactone (GVL) from levulinic acid (LA) under mild reaction conditions. In this study, Ag was added to Cu-supported γ-Al 2 O 3 catalyst to suppress Cu leaching in the hydrogenation of LA into GVL. The CuAg/Al 2 O 3 catalyst was reduced in situ during the reaction, and Cu leaching in the solution was significantly suppressed. The bimetallic catalyst without reduction pretreatment achieved approximately 100% yield to GVL and exhibited good reusability in nine consecutive cycles under mild reaction conditions of 180 °C and 1.4 MPa H 2 pressure in tetrahydrofuran (THF). The strong interplay in the geometric and electronic effects between Cu and Ag was verified through XPS, H 2 -TPR, TEM, STEM/EDS, and XRD analyses. This paper extensively discussed the mechanism of Ag on preventing Cu leaching and the superiority of in situ reduction in solution over external reduction in gas. [ABSTRACT FROM AUTHOR]