Chaoyong Wu

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 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.

Selective hydrogenation of citral catalyzed with palladium nanoparticles in CO2-in-water emulsion

CO2-in-Water (C/W) emulsion was formed by using a nonionic surfactant of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (P123), and palladium nanoparticles were synthesized in situ in the present work. The catalytic performance of Pd nanoparticles in the C/W emulsion has been discussed for a selective hydrogenation of citral. Much higher activity with a turnover frequency (TOF) of 6313 h−1 has been obtained in this unique C/W emulsion compared to that in the W/C microemulsion (TOF, 23 h−1), since the reaction was taking place not only in the surfactant shell but also on the inner surface of the CO2 core in the C/W emulsion. Moreover, citronellal was obtained with a higher selectivity for that it was extracted to a supercritical carbon dioxide (scCO2) phase as formed and thus its further hydrogenation was prohibited. The Pd nanoparticles could be recycled several times and still retain the same selectivity, but it showed a little aggregation leading to a slight decrease in conversion.

Selective hydrogenation of unsaturated aldehydes in a poly(ethylene glycol)/compressed carbon dioxide biphasic system

Hydrogenation of α,β-unsaturated aldehydes (citral, 3-methyl-2-butenal, cinnamaldehyde) has been studied with tetrakis(triphenylphosphine) ruthenium dihydride (H2Ru(TPP)4) catalyst in a poly(ethylene glycol) (PEG)/compressed carbon dioxide biphasic system. The hydrogenation reaction was slow under PEG/H2 biphasic conditions at H2 4 MPa in the absence of CO2. When the reaction mixture was pressurized by a non-reactant of CO2, however, the reaction was significantly accelerated. As CO2 pressure was raised from 6 MPa to 12 MPa, the conversion of citral increased from 35% to 98%, and a high selectivity to unsaturated alcohols (geraniol and nerol) of 98% was obtained. The products were able to be extracted by high pressure CO2 stream and separated from the PEG phase, dissolving the Ru complex catalyst and the catalyst was recyclable without any post-treatment.

Highly selective and efficient catalytic conversion of ethyl stearate into liquid hydrocarbons over a Ru/TiO2 catalyst under mild conditions

An efficient Ru/TiO2 catalyst was successfully designed and synthesized for the deoxygenation of long chain fatty acid esters under mild conditions (200 °C, 3.0 MPa). This work provides an energy-economic route to upgrade the oils with high oxygen content into green biofuels.

Synthesis of polyurethane-urea from double CO2-route oligomers

A series of thermoplastic polyurethane-ureas were synthesized from a soft segment of a polycarbonate diol and a hard segment of an oligourea, and both the segments were derived from the CO2-route. The chemical structure of the synthesized segments and final polyurethane-ureas were identified by FT-IR and 13C-NMR. The average molecular weight of the oligourea was detected by potentiometric titration, MALDI-TOF and GPC. The Mn and Mw of the final polyurethane-ureas were nearly 0.7 × 104 Da and 1.0 × 104 Da, respectively, within a polydispersity index (PDI) of 1.27–1.44. Moreover, the X-ray diffraction (XRD) results showed that the as-synthesized polyurethane-ureas were amorphous and presented moderate thermo-stable properties with an initial decomposition temperature higher than 170 °C and a maximum decomposition temperature around 250 °C as examined by TGA. Furthermore, the amorphous polyurethane-ureas have a good solubility in some traditional organic solvents because the siloxane and carbonate groups were introduced into the main chain. The present novel polyurethane-urea, which possesses a high flexibility and fine compatibility with other polymeric materials, will have a wide application as a macromolecular plasticizer in plastic materials.