Search

Mesoporous manganese oxide (MPMO) from reduction of KMnO4 with maleic acid, was obtained and characterized in detail. The characterization of the material was confirmed by high-resolution transmission electron microscopy (HRTEM), X-ray powder diffractometry (XRD) and N2 sorptometry. The results showed that MPMO is a pseudo-crystalline material with complex network pore structure, of which BET specific surface area is 297 m2/g and pore size distribution is approximately in the range of 0.7–6.0 nm. The MPMO material turns to cryptomelane when the calcinating temperature rises to 400 °C. The optimum sol–gel reaction conditions are KMnO4/C4H4O4 molar ratio=3, pH=7 and gelation time>6 h. [Copyright &y& Elsevier] more...

• CoPc-Mn(OAc) 2 -HBr catalytic system for selective oxidation shows high quinclorac selectivity and yield. • CoPc leads to more active species of Co3+, and thus facilitating the catalytic performance. • Experiments and theoretical calculations have proven the generation of 3,7-dichloro quinoline-CO radical species. • A Co2+/Co3+ mediated free radical mechanism is proposed. Nowadays, the use of quinoline derived synthons as precursors of quinclorac products is an important research topic in green chemistry. O 2 is a cheap, stable, and eco-friendly oxidant, holding promise for organic oxidation reactions. Herein, we have pioneered the discovery of CoPc-Mn(OAc) 2 -HBr (CoPc-Mn-Br) catalyst system for the selective oxidation of 3,7-dichloro-8-dichloro methyl quinoline (3,7-D-8-DMQ) into quinclorac with high 3,7-D-8-DMQ conversion at 59.3 %. The CoPc-Mn-Br exhibits excellent selectivity of quinclorac (up to 60.3 %), affording high quinclorac yield of 35.7 %, which is 3.1-fold higher than the yield of Co(OAc) 2 -Mn(OAc) 2 -HBr (Co-Mn-Br). Electron paramagnetic resonance (EPR) investigations and density functional theory (DFT) calculations indicate that CoPc promotes the adsorption and activation of O 2 in this oxidation process, which generates more Co3+, leading to producing the reactive intermediate species 3,7-dichloro-8-carbonyl quinoline free radicals via the radical process. The insight achieved from this fundamental study may be further applied to other organic syntheses via selective oxidation. [ABSTRACT FROM AUTHOR] more...

Methanol steam reforming (MSR) holds great potential for mobile hydrogen production, but it still requires an active and stable catalyst. In this work, we report a high-performance ZnZr-0.5 composite oxide catalyst for this reaction, with a hydrogen production rate of 2.80 mol·g cat −1·h−1 and CO 2 selectivity of 99.6% at a methanol space velocity of 22,762 mL·g cat −1·h−1. It also exhibits superior long-term durability in the TOS test for more than 100 h. Such good activity results from a synergistic effect of ZnO–ZrO 2 dual sites. ZrO 2 is capable of stabilizing and storing more CH 3 O∗ and HCOO∗ intermediates while ZnO is in charge of the dehydrogenation of these key intermediates. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and chemisorption results reveal that the MSR reaction experiences successively the hydrolysis of methyl formate and dehydrogenation of formate. More importantly, it is found that H 2 O significantly promotes the dehydrogenation of HCOO∗ intermediate by directly participating in this reaction from pulse chemisorption experiments. • A ZnZrO x oxide catalyst was developed for efficient and stable MSR reaction. • The best H 2 production rate reaches up to 2.80 mol·g cat −1·h−1 over ZnZr-0.5. • The high MSR activity results from synergistic effect between ZnO and ZrO 2 sites. • The MSR reaction follows a methyl formate/formate mediated pathway. • Water is verified to promote the formate dehydrogenation reaction as a direct reactant. [ABSTRACT FROM AUTHOR] more...

Surface modification of MCM-41 with the mixture of Cl(CH2)3SiCl3 and CH3SiCl3 produced chloropropyl–methyl-bifunctionalized MCM-41 in one pot. It was found that CH3SiCl3 as a small molecule silylating agent could be used as both a thinner to adjust chloropropyl group loading density and end-capping one to decrease the amount of silanol groups on mesoporous silica. The chloropropyl–methyl-bifunctionalized MCM-41 has a better hydrothermal stability than chloropropyl-functionalized MCM-41 due to improved surface hydrophobicity. [Copyright &y& Elsevier] more...

Methanol steam reforming (MSR) is deemed to be an effective way for hydrogen production and Pd/ZnO catalyst were found to exhibit high activity in this reaction. However, their activities are strongly related to the preparations methods. In most cases, these catalysts are synthesized by impregnation or co-precipitation methods, aiming to change the dispersion and stability of Pd nanoparticle to get better performance. Here we report an efficient Pd/ZnO catalyst that was synthesized with zeolitic imidazolate framework-8 (ZIF-8) as the precursor, on which Pd ions was supported after NaHB 4 reduction. Typically, when the catalyst reduced at 300 °C for 2 h, the methanol conversion could reach 97–98% and the CO 2 selectivity is around 86.3% under the reaction condition of 0.1 MPa, water/CH 3 OH = 1.2:1 (mol ratio), WHSV methanol = 43152ml/g cat *h, catalyst = 0.1 g, our catalyst was found to show much better performance than other Pd@ZnO catalysts prepared by other methods, especially in terms of selectivity which is particularly important for hydrogen fuel cell application considering that Pt electrode could be poisoned by even trace amount of CO. It turned out that the large surface area, enough holes, evenly distributed PdZn alloy activity sites and abundant oxygen vacancies lead to the overall excellent performance of our catalyst. • A PdZn alloy catalyst derived from ZIF-8 was synthesized successfully. • The PdZn catalyst shows both high stability and selectivity toward methanol steam reforming. • Different reaction conditions were investigated for optimal MSR hydrogen production. • Key parameters having great impact on performance of PdZn alloy catalyst was revealed. [ABSTRACT FROM AUTHOR] more...