Qifan Wu

Highly selective Pt/ordered mesoporous TiO2–SiO2 catalysts for hydrogenation of cinnamaldehyde: The promoting role of Ti2+

A highly selective and stable catalyst based on Pt nanoparticles confined in Mesoporous TiO2-SiO2 frameworks were prepared and employed for selective hydrogenation of cinnamaldehyde to cinnamyl alcohol. The as-prepared Pt/MesoTiO2-SiO2-M catalyst displayed excellent selectivity to cinnamyl alcohol (around 91%) at nearly complete conversion. Ti(2+) and stronger metal-support interaction (SMSI) played key roles on the adsorption behavior of cinnamaldehyde and activation of CO bonds. The existence of amorphous SiO2 and mixed TiO2 phases (anatase and rutile) was helpful for the formation of Ti(2+) sites and SMSI. The electron-enriched Pt surfaces and the formed Pt-TiOx system benefited the enhanced activity and selectivity.

Synthesis of Ni/mesoporous ZSM-5 for direct catalytic conversion of cellulose to hexitols: modulating the pore structure and acidic sites via a nanocrystalline cellulose template

Efficient utilization of cellulose is of scientific significance and a great challenge for both fundamental and industrial studies. Herein, we synthesized MesoZSM-5 zeolites by using nanocrystalline cellulose as a template for the first time, and reported the exciting performance of the corresponding non-noble metal catalysts (Ni/MesoZSM-5) for efficient conversion of cellulose to hexitols. By modulating the ratio of the template to precursor, MesoZSM-5 supports were produced with tunable pore structure and acidic sites. With the cooperation of active Ni sites and acidic sites of MesoZSM-5, hexitols were obtained with a high yield of around 60% in the direct conversion of commercial microcrystalline cellulose (MCC). The corresponding correlation between the structural characteristics and catalytic performance was established. This work provides a new approach for efficient utilization of cellulose, as well as gives rise to a sustainable templating method for the synthesis of mesoporous zeolites.

PdGa/TiO2 an efficient heterogeneous catalyst for direct methylation of N-methylaniline with CO2/H2

An effective sustainable heterogeneous PdGa/TiO2 catalyst was prepared for direct methylation of N-methylaniline with CO2/H2 to N,N-dimethylaniline. The PdGa/TiO2 catalyst exhibited 98% conversion and 94% selectivity under the reaction conditions (180 °C, 5 MPa H2, 5 MPa CO2, 10 h), which are one of the best results reported to date for the heterogeneous N-methylation with CO2 as methylation reagent over the supported metal catalysts. The PdGa/TiO2 catalyst was well characterized using TEM, TPR, XPS, CO-adsorption IR studies and high-pressure in situ FTIR studies. It was confirmed that PdGa bimetallic alloy nanoparticles were formed and highly dispersed on the TiO2 support, and the electron-deficient Pd derived from the interaction with Ga could activate CO2 and transform it to formic acid, which is the key step for the discussed methylation, and high activity was obtained over the PdGa/TiO2 catalyst. The activating properties of the PdGa/TiO2 catalyst will open a new route for transfer and utilization of CO2 in the fields of energy and environmental fields.

A Study on the Oxygen Vacancies in ZnPd/ZnO-Al and their Promoting Role in Glycerol Hydrogenolysis

The relationship between catalyst structure and catalytic activity is an important and challenging topic for researchers in the field of catalysis. In this work, the effect of oxygen vacancies on the activity of ZnPd/ZnO‐Al catalysts was studied in an important reaction—glycerol hydrogenolysis. Interestingly, the catalytic activity improved significantly with the addition of a small amount of Al, and high selectivity to 1,2‐propanediol (>90 %) was achieved in glycerol hydrogenolysis over ZnPd/ZnO‐Al catalysts. Importantly, the formation of oxygen vacancies benefits from the substitution of Al atoms, and the Al content in the ZnO lattice is related to the oxygen vacancies density and catalytic activity. Moreover, the important role played by oxygen vacancies in glycerol hydrogenolysis has been discussed in detail.

Macroporous–mesoporous carbon supported Ni catalysts for the conversion of cellulose to polyols

Carbon based materials are some of the most commonly studied catalysts for the conversion of cellulose to polyols. The catalytic performance of these materials, however, is typically limited by the access of the substrate to the active sites, which is governed by the poor solubility of cellulose in aqueous solutions. In an attempt to resolve this, we presented a novel hierarchical carbon material which was synthesized by a dual-templating method. Transmission electron microscopy and porosity measurements confirmed that the resultant materials consisted of both spherical macropores and well-defined mesoporous channels. Additional characterisation of this material revealed that it has an exceptionally high surface area (>1110 m2 g−1) and a high concentration of acidic sites, which are considered to be crucial for the hydrolysis of cellulose. Ni nanoparticles were subsequently immobilised onto this material and some additional carbon supports. It was determined that the high surface area and porosity of the synthesised carbon material assisted with the dispersion of the Ni nanoparticles. This Ni catalyst was found to be highly efficient for the one-pot conversion of cellulose to polyols, which is proposed to be a consequence of both the high number of acid sites and excellent Ni dispersion. This approach to catalyst design, offers a novel method for the valorisation of cellulose.

Solvent effects on heterogeneous catalysis in the selective hydrogenation of cinnamaldehyde over a conventional Pd/C catalyst

Solvent effects in the selective hydrogenation of an α,β-unsaturated aldehyde of cinnamaldehyde (CAL) were investigated under gas–liquid–solid reaction conditions. A conventional 5 wt% Pd/C catalyst and twelve organic solvents were used, including apolar solvents (three) and protic (two) and aprotic (seven) polar ones. The total rate of CAL hydrogenation strongly depended on the solvents used. The relationship between the rate of CAL hydrogenation observed and a few different solvent parameters was examined. The main product was hydrocinnamaldehyde (HCAL) with a selectivity of 80% or higher in most of the solvents examined except for pyridine and 4-methylpyridine. In these two solvents, the CAL hydrogenation was slow and the main product was changed to cinnamyl alcohol (COL) with a selectivity of about 60%. The addition of a small volume of pyridine to other solvents such as 2-propanol and tetrahydrofuran could change the rate of hydrogenation and switch the main product from HCAL to COL. Possible interactions among the solvents, CAL substrate, and Pd/C catalyst were examined by FTIR (attenuated total reflection (ATR-) and diffuse reflectance modes (DR-)) and TPD to discuss the solvent effects observed in the Pd-catalyzed heterogeneous CAL hydrogenation.

A Robust Ru/ZSM-5 Hydrogenation Catalyst: Insights into the Resistances to Ruthenium Aggregation and Carbon Deposition

A long‐life topic in the field of heterogeneous catalysis has been to develop supported catalysts that are stable against the aggregation of active metal and carbon deposition. Herein, we report a highly stable Ru/ZSM‐5 catalyst for the hydrogenation of levulinic acid in water, which can be recycled at least 10 times without apparent loss of activity (conv. >95 %, yield >85 %). The influences of types of Al species, structure of support, Ru sizes, Ru leaching, and carbon deposition, etc. on activity and stability were discussed in detail. It was confirmed that the tetrahedral‐coordinated framework Al in ZSM‐5 contributed to the favorable metal–support interaction, and thus suppressed the aggregation and leaching of ruthenium during recycling. Besides, the suitable pore volume and channel network connectivity successfully prevent from deposition of carbonaceous residues.