Search

As a direct conversion route for the production of ethylene from methane, the oxidative coupling of methane (OCM) is highly promising. The Mn2O3‐Na2WO4/SiO2 catalyst doped with 44 μm anatase‐TiO2, consisting of 5 wt% TiO2, 5 wt% Mn2O3, 8 wt% Na2WO4 and balance SiO2 was prepared, achieving ∼22 % CH4 conversion with ∼72 % selectivity towards C2−C3 hydrocarbons even at the relatively low temperature of 700 °C. This catalyst was found to run stably for at least 300 h without signs of deactivation, which provides promising and comparable low‐temperature activity and selectivity but a more cost‐effective alternative to the previously‐reported Mn2O3‐Na2WO4/Ti‐MWW catalyst containing expensive Ti‐MWW zeolite. XRD and Raman analyses revealed that the in situ formation of MnTiO3 in the TiO2‐doped catalyst is responsible for the gains in low‐temperature OCM activity. In addition, TPR and TPO results also indicated that MnTiO3 activates O2 more readily at ∼650 °C, while three‐step switchover experiments clearly demonstrated that MnTiO3 could trigger facile redox behavior at low reaction temperatures. Thus, the MnTiO3‐induced redox cycle for O2 activation enables this TiO2‐doped catalyst to provide superior CH4 conversion at 700 °C. [ABSTRACT FROM AUTHOR]

Catalytic oxymethane reforming is an effective and efficient route to produce syngas, but the commonly used Ni catalysts suffer from coke deposition, Ni sintering, and heat-transfer limitations. A Ni-foam-structured NiO-MgO-Al2O3 nanocomposite catalyst was developed by thermal decomposition of NiMgAl layered double hydroxides (LDHs) in situ hydrothermally grown onto the Ni-foam. Originating from the lattice orientation effect and topotactic decomposition of the LDH precursor, NiO, MgO, and Al2O3 are highly distributed in the nanocomposite, and thus, this catalyst shows enhanced resistance to coke and sintering. At 700 °C and a gas hourly space velocity of 100 L g−1 h−1, 86.5 % methane conversion and selectivities of 91.8/88.0 % to H2/CO are achieved with stability for at least 200 h. We believe this type of tailoring strategy and the as-obtained materials can open up new opportunities for future applications in other high-throughput and high-temperature reactions. [ABSTRACT FROM AUTHOR]

Cu-fiber-structured ternary Pd-Au-CuO x catalysts engineered from nano- to macro-scales have been developed for the vapor-phase dimethyl oxalate (DMO) hydrogenation to ethylene glycol (EG), with the aid of galvanic deposition of Pd and Au onto a thin-sheet microfibrous structure using 8 μm Cu fiber. Effects of Pd and Au loadings and their ratio have been investigated on the catalyst performance as well as the reaction conditions including reaction temperature and pressure, liquid weight hourly space velocity, and H2/DMO ratio. The promising 0.1 Pd-0.5 Au-CuO x/Cu-fiber catalyst is capable of converting 97-99 % DMO into EG product at a selectivity of 90-93 %. This catalyst is stable for at least 200 h. The Pd-Au-Cu2O synergistically promotes the hydrogenation activity and stabilizes Cu+ sites to suppress deep reduction deactivation. [ABSTRACT FROM AUTHOR]

Thin-sheet sinter-locked Ti-microfiber-supported binary-oxide-nanocomposite catalysts engineered on the micro- to macroscales were developed for the gas-phase aerobic oxidation of benzyl alcohol to benzaldehyde. The catalysts demonstrated higher activity than single-oxide and noble-metal catalysts with good stability and regenerability. The catalysts were obtained by placing transient metal (e.g., Ni, Co, Cu, Mn) nitrates onto a Ti-microfiber surface by impregnation, and the supported nitrates were subsequently in situ transformed into the binary-oxide composites in the real reaction stream at 300 °C. Among them, CoO-2.5-CuO x-2.5/Ti-fiber was found to be the best catalyst; it delivered 93.5 % conversion of benzyl alcohol (b.p. 210 °C) with 99.2 % selectivity to benzaldehyde at 230 °C. In situ induced formation of 'CoO@Cu2O' ensembles (i.e., larger CoO nanoparticles partially covered with smaller Cu2O clusters and/or nanoparticles) was identified, which by nature resulted in a large Cu2O-CoO interface and led to a significant improvement in the low-temperature activity. [ABSTRACT FROM AUTHOR]