Heterogeneously-catalyzed aerobic oxidation of furfural to furancarboxylic acid with CuO-Promoted MnO_(2)

A cost-effective and sustainable noble-metal free catalyst system based on ubiquitously available Mn-Cu bimetallic oxides was served as efficient catalysts for furfural selective oxidation to furancarboxylic acid(FA). Interestingly, Mn_(2)Cu_(1)O_(x)exhibited an excellent furfural conversion of 99% with quantitative selectivity toward FA. Especially, we demonstrate the significant weakening of the Mn-O bonds with the incorporation of CuO into the Mn-Cu oxides, resulting in an improved OLreactivity of Mn_(2)Cu_(1)O_(x), which brings about a higher catalytic activity for furfural oxidation. More importantly, Mn_(2)Cu_(1)O_(x)could exhibit YFA>90% over 5 cycles of reusability test. Through this study, the relationship between the morphology, surface chemistry, and catalytic activity of Mn-Cu bimetallic oxides are elucidated, providing a simple and environmentally friendly catalytic strategy and scientific basis for the development of Mn-Cu bimetallic oxides bioderived molecular aerobic oxidation materials.

Synthesis, isolation and characterization of methyl levulinate from cellulose catalyzed by extremely low concentration acid

A direct synthesis of methyl levulinate from cellulose alcoholysis in methanol medium under mild condition(180 210 C)catalyzed by extremely low concentration sulfuric acid(0.01 mol/L)and the product isolation were developed in this study.Effects of different process variables towards the catalytic performance were performed as a function of reaction time.The results indicated that sulfuric acid concentration,temperature and initial cellulose concentration had significant effects on the synthesis of methyl levulinate.An optimized yield of around 50%was achieved at 210 C for 120 min with sulfuric acid concentration of 0.01 mol/L and initial cellulose concentration below 100 g/L.The resulting product mixture was isolated by a distillation technique that combines an atmospheric distillation with a vacuum distillation where n-dodecane was added to help distill the heavy fraction.The light fraction including mainly methanol could be reused as the reaction medium without any substantial change in the yield of methyl levulinate.The chemical composition and structural of lower heavy fraction were characterized by GC/MS,FTIR,1H-NMR and13C-NMR techniques.Methyl levulinate was found to be a major ingredient of lower heavy fraction with the content over 96%.This pathway is efficient,environmentally benign and economical for the production of pure levulinate esters from cellulose.

Effects of Zr/Ti molar ratio in SO_4^(2-)/ZrO_(2-)TiO_2 calcined at different temperatures on its surface properties and glucose reactivity in near-critical methanol

Effects of Zr/Ti molar ratio in SO42-/ZrO2-TiO2 solid acid catalyst calcined at different temperatures on its surface properties and catalytic activity were thoroughly investigated in this paper. The physicochemical characteristics of prepared samples were determined by N2 adsorptiondesorption, XRD, NH3-TPD and XPS techniques, respectively. It was found that the crystallization temperature of the samples increased after the combination of ZrO2 and TiO2; and phase transformations from the anatase to the rutile of TiO2 species and the tetragonal to the monoclinic of ZrO2 species were effectively suppressed at higher temperature. The sample with a Zr/Ti molar ratio of 3/1 calcined at 450℃ showed the highest surface area and the most acid sites among all the tested samples. The acid site densities of samples were relatively closed to each other if they were calcined at the same temperature, however, decreased with the calcination temperature. The result indicates that the sulfur content in samples is a crucial factor to control the acid site density. Calcining the sample at 650℃ and higher temperatures resulted in a significant desorption of sulfate ion on the samples. The synthesized samples were evaluated as a potential catalyst for glucose conversion under the near-critical methanol conditions （200℃/4 MPa）. The results suggested that the relatively weaker acid sites of the catalyst were more favorable for the accumulation of methyl glucosides, while the moderate acid sites were responsible for the formation of methyl levulinate. The catalytic activity for methyl levulinate production almost increases linearly with the catalyst acid site density. The catalyst deactivation is due to the loss of sulfate ion and the two catalysts with Zr/Ti molar ratios of 3/1 and 1/3 could effectively alleviate the deactivation caused by sulfate solution in the reaction medium and can be reused after calcination with the reuse rate of over 90% in terms of the methyl levulinate selectivity.