Yejun Guan

Aerobic oxidation of alcohols over hydrotalcite-supported gold nanoparticles: the promotional effect of transition metal cations

Chromium (III)-containing hydrotalcites show strong synergy with gold nanoparticles in achieving high activity in the aerobic oxidation of alcohols.

Basic metal carbonate supported gold nanoparticles: enhanced performance in aerobic alcohol oxidation

Gold nanoparticles supported by basic hydrozincite or bismuth carbonate are excellent catalysts for liquid-phase aerobic alcohol oxidation: the performance of a series of metal (Zn, Bi, Ce, La, Zr) carbonate supported gold catalysts depends strongly on the basicity of the support material.

Unprecedented Oxygenate Selectivity in Aqueous-Phase Fischer–Tropsch Synthesis by Ruthenium Nanoparticles

Not just for anglers: An unprecedented oxygenate selectivity of 70?% in the Fischer–Tropsch synthesis is achieved by using a Ru nanoparticle catalyst in the aqueous phase. A kinetic analysis of the anomalous temperature dependence of the chain growth probability shows that hydrocarbons and oxygenates are formed on different sites. Oxygenates (hydrocarbons) form on sites with high (low) barrier for CO dissociation.

Enhanced hydrogenation of ethyl levulinate by Pd–AC doped with Nb2O5

Gamma-valerolactone (GVL), as sustainable feedstock for high-value chemicals and fuel, has been produced by hydrogenation of levulinic acid (LA) or ethyl levulinate (EL). In this work, Pd nanoparticles supported on Nb2O5-doped activated carbon (AC) were prepared via wet incipient impregnation with PdCl2 followed by reduction with NaBH4. The dispersed niobia plays a bifunctional role in the catalytic process: stabilizing Pd nanoparticles and acting as an acidic co-catalyst. This synergistic effect between niobia and Pd leads to an unprecedented high activity of supported Pd catalysts in EL hydrogenation. The synergy is correlated with both the niobia loading and calcination temperature, with 10 wt% Nb2O5 calcined at 500 °C showing the best performance (EL conversion of 87% and GVL selectivity of 97%) under mild reaction conditions (100 °C and 0.5 MPa H2).

Preparation and characterization of ordered mesoporous carbons on SBA-15 template

Ordered mesoporous carbons with high surface area were synthesized using SBA-15 as template at different temperatures. In the process, the precursor ferric acetylacetonate serves as the carbon source for nanofiber formation. In comparison with the morphology of carbon nanotube-encapsulated iron prepared without templates, the orientation of the carbon materials is controlled by the pore direction of the template. The microstructures of the mesoporous carbons are strongly dependent on the temperature of synthesis. Higher synthetic temperatures resulted in ordered mesoporous carbons with larger BET surface areas, pore diameters and increased pore volumes.

Tuning the hydrogenation activity of Pd NPs on Al–MIL-53 by linker modification

The hydrogenation activity of 3 wt.% Pd nanoparticles supported on various mono-group (H, OCH3, NH2, Cl, and NO2) substituted Al–MIL-53 materials has been investigated. Substituents enhanced the dispersion of palladium nanoparticles on Al–MIL-53, leading to a narrow particle size distribution in the range of 2 to 4 nm. Pd nanoparticles on fresh catalysts were present as a mixture of Pd(II) and Pd(0) with different ratios. These Pd species readily became metallic in a hydrogen flow even at room temperature. Their activities in hydrogenation of phenol and phenylacetylene are linked to the substituents on the aromatic ring of the framework. Catalysts with electron-donating groups (OCH3 and NH2) show much higher activity than those containing electron-withdrawing groups (Cl and NO2). This behavior might be explained by the hydrogen dissociation abilities of metallic Pd nanoparticles affected by the organic linkers.

Hydrogenation of γ-valerolactone in ethanol over Pd nanoparticles supported on sulfonic acid functionalized MIL-101

A ligand-based solid solution approach is employed to incorporate sulphonic acid functional groups into the porous coordination polymer Cr-MIL-101. Loaded with Pd nanoparticles these Pd/MIL-101-SO3H materials act as bifunctional catalysts for the one-pot conversion of γ-valerolactone into ethyl valerate (up to 83% yield). The catalysts were extensively characterized before and after reaction. The influence of the sulfonic acid group density and the reaction conditions on the catalytic activity was systematically investigated and the reaction network for γ-valerolactone upgrading was discussed.

Ionic-liquid-stabilized rhodium nanoparticles for citral cyclodehydration.

Smells nice, too: The cyclodehydration of citral is achieved by using rhodium nanoparticles dispersed in an imidazolium-based ionic liquid. p-Cymene, p--dimethylstyrene, and limonene are obtained with selectivity greater than 75?%. The interaction between the imidazolium cations and the metal nanoparticles results in an acidic catalyst, which plays a similar function as a mineral acid but has a one order of magnitude higher activity.

Clean synthesis of furfural oxime through liquid-phase ammoximation of furfural over titanosilicate catalysts

The clean synthesis of furfural oxime (FO) has been realized through titanosilicate-catalyzed liquid-phase ammoximation of furfural with ammonia and hydrogen peroxide. A detailed investigation of furfural ammoximation over three representative titanosilicates Ti-MOR, TS-1 and Ti-MWW reveals that the reaction involves the hydroxylamine route and the imine route. The hydroxylamine route accounts for the formation of the target product (FO), while the imine route leads to the formation of undesired products such as 2-furylamide and 2-furoic acid. With a high efficiency for hydroxylamine formation, Ti-MOR proves to be superior to TS-1 and Ti-MWW. The catalytic performance of Ti-MOR depends greatly on the operating conditions of the reaction, which is closely related to its activity in catalyzing hydroxylamine decomposition. The decomposition of hydroxylamine and the non-catalytic oxidation of furfural can be effectively suppressed in Ti-MOR-catalyzed ammoximation when employing water as the solvent and adding H2O2 dropwise into the reaction system. Under optimized conditions, Ti-MOR is capable of providing furfural conversion and oxime selectivity both above 97%.

Low temperature hydrogenation of α-angelica lactone on silica supported Pd–NiO catalysts with synergistic effect

The hydrogenation of α-angelica lactone (α-AL) was achieved under mild conditions on silica supported Pd–NiO catalysts. NiO and palladium were sequentially loaded on silica by wet-impregnation and deposition–reduction, respectively. First a series of NiO/SiO2 supports with varying Ni contents were prepared by a wet-impregnation method with Ni(NO3)2 as the precursor followed by calcination in air. Then a minute amount of palladium (0.2 wt%) was loaded by a deposition–reduction method using NaBH4 as a reducing reagent. The Pd–NiO catalysts were characterized by nitrogen adsorption, XRD, H2-TPR, XPS and TEM. The NiO were heterogeneously dispersed on silica with particle sizes ranging from 10 to 50 nm, whereas Pd was finely loaded with a diameter less than 5 nm. Nanoscale intimacy between Pd and NiO was noticed by HRTEM, resulting in high catalytic activity in liquid phase hydrogenation of α-angelica lactone to γ-valero lactone (GVL) under mild conditions. 0.2Pd–9.9NiO/SiO2 showed the best activity among all the catalysts investigated, with 82% conversion and 100% selectivity to GVL within several minutes at 30 °C and 0.3–1 MPa H2 pressure.