The prevalence of IBD has increased in Wuhan City, central China, but is not as high as in Western countries. The disease in Wuhan City has often been associated with young adult professional males with a high level of education. The clinical presentation of UC was often mild and had few extra intestinal manifestations.
Direct oxidation of glucose with enhanced selectivity to glucaric acid with tartronic and oxalic acids as coproducts is reported using bimetallic PtPd/TiO 2 catalysts under mild conditions. Bimetallic PtPd catalysts display significantly enhanced catalytic activity (turnover frequency (TOF) 2404 h −1 ) and improved selectivity to glucaric acid (S 44%) in glucose oxidation compared to monometallic catalysts (TOF 248 h −1 , S 4%). Oxidation of glucose follows a consecutive reaction with gluconic acid as an intermediate with inhibition of the second step (to glucaric acid and C−C cleavage reactions) by the presence of glucose. Surface characterization using TEM, SEM, chemisorption, UV−vis spectroscopy, and XRD distinguished the particle morphologies and provided insights into structure−activity relations. A reaction pathway for glucose oxidation is proposed based on the product distribution. These results provide new insights into the design of bimetallic catalysts for the oxidation of glucose to glucaric acid.
We report for the first time the performance of hybridized Cu/CaO-Al 2 O 3 catalysts for aqueous-phase hydrogenolysis of sorbitol to ethylene glycol (EG), 1,2-propanediol (1,2-PDO), and 1,2-butanediol (1,2-BDO) with linear alcohols as coproducts in a base-free liquid phase. These supported Cu catalysts with solid bases as promoters show significant activity for C−C cleavage and high selectivity (∼84%) to glycols and linear alcohols. The effects of Cu loading, catalyst pretreatment conditions, H 2 pressure, and temperature on activity and selectivity of Cu/CaO-Al 2 O 3 catalysts were investigated. The strong interaction between Cu and Ca 2+ cations in the solid support is found to facilitate C−C and C−O cleavage of sorbitol, as evidenced from TEM, SEM, and TPR studies of the catalysts. Surface characterization and activity tests further suggest that Ca x Cu y Al z O p (Phase I) promotes dehydrogenation and isomerization reactions, whereas spinal CuAl 2 O 4 (Phase II) species facilitates hydrogenation reactions. In addition, the overall activity and selectivity of the Cu catalysts may be easily tuned by the Cu/Ca 2+ molar ratio and catalyst preparation conditions. Cu/CaO-Al 2 O 3 catalysts also give higher overall yields of value-added glycols (63−82%) for facile conversion of various other sugar polyols such as glycerol (C 3 ), erythritol (C 4 ), xylitol (C 5 ), and mannitol (C 6 ) under similar reaction conditions. A surface reaction mechanism involving the formation of β-ketoses on multifunctional Cu−Ca 2+ sites is proposed.
Significant ethylene epoxidation activity was observed over Nb-and W-incorporated KIT-6 materials with aqueous hydrogen peroxide (H 2 O 2 ) as the oxidant and methanol as solvent under mild operating conditions (35°C and 50 bar) where CO 2 formation is avoided. The Nb-KIT-6 materials generally show greater epoxidation activity compared to the W-KIT-6 materials. Further, the ethylene oxide (EO) productivity observed with these materials [30-800 mg EO h −1 (g metal)] is of the same order of magnitude as that of the conventional silver (Ag)-based gas phase ethylene epoxidation process. Our results reveal that the framework-incorporated metal species, rather than the extra-framework metal oxide species, are mainly responsible for the observed epoxidation activity. However, the tetrahedrally coordinated framework metal species also introduce Lewis acidity that promotes their solvolysis (which in turn results in their gradual leaching) as well as H 2 O 2 decomposition. These results and mechanistic insights provide rational guidance for developing catalysts with improved leaching resistance and minimal H 2 O 2 decomposition.
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