Haiyang Cheng

Synthesis of urea derivatives from amines and CO2 in the absence of catalyst and solvent

Urea derivatives are obtained in mild to good yield from the reactions of primary aliphatic amines with CO2 in the absence of any catalysts, organic solvents or other additives. To optimize reaction conditions, experimental variables including temperature, pressure, the concentration of amine, reaction time etc. were studied. Satisfactory yields were obtained at the optimized conditions that are comparable to the presence of catalyst and solvent. The preliminary investigation of the reaction mechanism showed that alkyl ammonium alkyl carbamate was quickly formed as the intermediate, and then the final product was formed by the intramolecular dehydration.

Selective conversion of concentrated microcrystalline cellulose to isosorbide over Ru/C catalyst

Highly concentrated microcrystalline cellulose was directly converted to isosorbide with yields of 35–50%, providing a new approach for producing important fine chemicals from biomass.

Selective conversion of microcrystalline cellulose into hexitols on nickel particles encapsulated within ZSM-5 zeolite

A highly active and selective Ni/ZSM-5 catalyst was prepared by a simple method. A selectivity of 91.2% to hexitols was obtained at intermediate conversion in the hydrolytic hydrogenation of cellulose.

Polyethylene glycol-stabilized platinum nanoparticles: The efficient and recyclable catalysts for selective hydrogenation of o-chloronitrobenzene to o-chloroaniline

In the present work, platinum nanoparticles were prepared by in situ reduction with polyethylene glycols (PEGs). The catalytic performance of Pt nanoparticles immobilized in PEGs (Pt-PEGs) is discussed for the hydrogenation of o-chloronitrobenzene (o-CNB). A high selectivity to o-chloroaniline (o-CAN) of about 99.7% was obtained with the Pt-PEGs catalysts at the complete conversion of o-CNB, which is much higher than that (83.4%) obtained over the conventional catalyst of Pt/C. The Pt nanoparticles could be immobilized in PEGs stably and recycled for four times with the same activity and selectivity. It presents a promising performance in the hydrogenation and its wide application in catalytic reactions is expected.

An effective medium of H2O and low-pressure CO2 for the selective hydrogenation of aromatic nitro compounds to anilines

Chemoselective hydrogenation of water-insoluble aromatic nitro compounds can be achieved over Ni catalysts in a H2O–compressed CO2 system at 35–50 °C without using any environmentally harmful solvent. The effective CO2 pressure is much lower than the critical pressure of CO2. The hydrogenation of nitro group should be the rate-determining step.

Selective reduction of phenol derivatives to cyclohexanones in water under microwave irradiation

Selective reduction of phenol to cyclohexanone over the Pd/C catalyst in the presence of a hydrogen source of HCOONa/H2O has been studied. Surprisingly, phenol was transformed efficiently to cyclohexanone in an excellent yield of above 98% under microwave irradiation. The influence of some parameters like reaction temperature, time and amount of hydrogen donor, as well as the reaction pathway has been discussed. The combination of microwave irradiation and HCOONa/H2O was certified to be effective for the reduction of phenol as well as its derivatives to their corresponding cyclohexanones.

A new strategy for finely controlling the metal (oxide) coating on colloidal particles with tunable catalytic properties

In this contribution, we present an efficient, versatile and green strategy for finely controlling the metal (oxide) coating on core particles through in situ reaction of precursors in CO2 expanded ethanol without using any precipitants. It not only avoids the formation of free metal (oxide) and/or naked cores, but also permits individual dispersion of all the resultant particles without aggregation. With this method, the composition, thickness, uniformity, and structure of the metal (oxide) shell could be precisely controlled. A wide variety of unreported high-quality core-shell particles with a shell consisting of highly dispersed metal (oxide) nanocrystals or nanoalloys, such as C@Ni, CoO/C, C@Ni&Co and C@Ni&Pd particles have been fabricated, and the properties of the resultant particles were precisely tailored, such as the promising catalytic performance obtained over Ni/C and C@Ni particles in the hydrogenation of nitrobenzene. The present coating strategy is more simple and precisely controllable compared to the conventional deposition method and it is suitable for most precursors and even for multi-component materials, enabling the fabrication of nanostructured materials more easily and precisely.

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.

Knitting an oxygenated network-coat on carbon nanotubes from biomass and their applications in catalysis

In this work, we presented a new way for the functionalization of carbon nanotubes (CNTs) with the use of biomass as starting materials and introduced a novel concept of knitting process in the chemistry of CNTs for the first time. A mixture of aromatic compounds obtained from the hydrothermal treatment of biomass, rather than the traditional polymer monomers, was used as the nanoscale building blocks to knit an oxygenated network-coat on the CNTs layer-by-layer. It is an effective, mild, green and easily-controlled method for the functionalization of CNTs. The obtained f-CNTs were proved to be a promising catalyst support for metal catalysts, such as Ru/f-CNTs, showed high activity and selectivity for the hydrogenation of citral to unsaturated alcohol. More importantly, we opened a pioneering way for the conversion of low-cost, abundant and renewable biomass into a hydrophilic/chemical reactive network-coat on the inert surface of a wide range of sp2carbon materials, such as prevalent fullerene, carbon nanotubes, carbon nanohorns and hot grapheneetc.

Cyclization of citronellal to p-menthane-3,8-diols in water and carbon dioxide

A clean process has been developed for the synthesis of p-menthane-3,8-diols from cyclization of citronellal in CO2–H2O medium without any additives. With the addition of CO2, the reaction rate could be enhanced about 6 times for the cyclization of citronellal in H2O, because CO2 dissolved into water and formed carbonic acid inducing an increase of the acidity. Although, the reaction conversion in CO2–H2O is slightly lower compared to that obtained with sulfuric acid as catalyst, CO2–H2O could replace the sulfuric acid at a relative higher reaction temperature. The reaction kinetics studies showed that the hydration of isopulegols to p-menthane-3,8-diols is a reversible reaction. The equilibrium constant and the maximum equilibrium yield obtained in CO2–H2O at a range of CO2 pressures are similar to that with sulfuric acid catalyst.