Mouhua Wang

Synthesis of dimethyl carbonate by transesterification over CaO/carbon composites

A CaO/C composite, a new solid base catalyst, was prepared and served as a convenient and efficient heterogeneous catalyst for synthesis of DMC from methanol and propylene carbonate. Compared with pure CaO, the CaO/C shows the same basic properties and a high performance. In addition, the CaO/C catalyst, which is easily recovered, can be reused with little deactivation, if a suitable particle size is chosen.

Effect of base strength and basicity on catalytic behavior of solid bases for synthesis of dimethyl carbonate from propylene carbonate and methanol

MgO and CaO prepared from the dissociation of basic magnesium carbonate and calcium carbonate at elevated temperature were used to investigate the effect of base strength and basicity on the synthesis of dimethyl carbonate (DMC) from propylene carbonate (PC) and methanol (MeOH). It was found that the rise of base strength could reduce the temperature needed for this reaction remarkably. On the other hand, with the increase of the amount of base site, the reaction rate rises but DMC selectivity decreases.

Properties and evaluation of amidoxime-based UHMWPE fibrous adsorbent for extraction of uranium from seawater

An amidoxime-based ultra-high molecular weight polyethylene (UHMWPE) fibrous adsorbent was successfully prepared by γ-irradiation-induced graft copolymerization of acrylonitrile (AN) and acrylic acid (AA), followed by amidoximation. The grafting of AN and AA on the UHMWPE fiber and the amidoximation of the grafted fiber were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The mechanical property of the original and modified UHMWPE fibers was compared by single-filament strength test. The adsorption property of the UHMWPE fibrous adsorbent was evaluated by adsorption test in uranyl nitrate solution and seawater. The surface of the modified UHMWPE fibers was covered by the grafting layer and became rough. The tensile strength of the amidoxime-based UHMWPE fibrous adsorbent was influenced by the absorbed dose and hydrochloric acid elution, but was independent of the grafting yield and amidoximation. The uranium adsorption amount of the amidoxime-based UHMWPE fibrous adsorbent after immersing in seawater for 42 days was 2.3 mg-U/g.

Preparation and characterization of superhydrophobic organic-inorganic hybrid cotton fabrics via γ-radiation-induced graft polymerization

A new kind of non-fluorine-based organic-inorganic hybrid superhydrophobic cotton fabric was successfully prepared by simultaneous radiation-induced graft polymerization of γ-methacryloxypropyl trimethoxy silane (MAPS) and subsequent end-capping modification with hexamethyldisilazane (HMDS). The chemical structure and surface topography of the pristine and modified cotton fabrics were investigated in detail by ATR-FTIR, XPS, (29)Si NMR, SEM and TGA to confirm that the graft reaction and end-capping modification had taken place. The above results demonstrated that the grafting polymerization and following end-capping reaction were completed, and a grafting layer was immobilized onto the surface of the cotton fabric. Surface wettability measurement and oil-water separation showed that the modified cotton surface not only exhibited the superhydrophobicity with a water contact angle of 165°, but also afforded a high efficiency of oil-water separation (96%). In particular, this modified cotton fabric retains superhydrophobicity even after 30 laundering cycles or 400 cycles of abrasion.

Functionalized and reusable polyethylene fibres for Au(III) extraction from aqueous solution with high adsorption capacity and selectivity

A new chelating polyethylene fibre was synthesised by the radiation-induced graft copolymerisation of glycidyl methacrylate (GMA) onto ultrahigh-molecular-weight polyethylene (UHMWPE) fibres and subsequent ring-opening reaction with 4-amino-1,2,4-triazole. The chemical structure and surface morphology of the modified fibres were characterised by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The adsorption behaviour of the fibrous sorbent for Au(III) was investigated in terms of aqueous-solution pH, contact time, initial metal concentration and competition of coexisting metal ions. Resultant fibres exhibited much higher affinity and selectivity for Au3+ ions than all other metal ions (Mg2+, Fe3+, Cu2+, Ca2+, Ni2+ and Cr6+). The affinity coefficient obtained was as high as 97.5–99.9%. The maximum adsorption amount for Au3+ was 429.4 mg g−1. The adsorption of Au(III) followed the pseudo-second-order kinetics model controlled by chemical adsorption. The equilibrium data fitted the Langmuir isotherm model well. In particular, this fibrous adsorbent can be regenerated by treatment in 0.5 M thiourea and 0.5 M H2SO4 solution. The high adsorption capacity can be maintained after at least five adsorption–desorption cycles.

Supercritical CO2 Foaming of Radiation Cross-Linked Isotactic Polypropylene in the Presence of TAIC

Since the maximum foaming temperature window is only about 4 °C for supercritical CO2 (scCO2) foaming of pristine polypropylene, it is important to raise the melt strength of polypropylene in order to more easily achieve scCO2 foaming. In this work, radiation cross-linked isotactic polypropylene, assisted by the addition of a polyfunctional monomer (triallylisocyanurate, TAIC), was employed in the scCO2 foaming process in order to understand the benefits of radiation cross-linking. Due to significantly enhanced melt strength and the decreased degree of crystallinity caused by cross-linking, the scCO2 foaming behavior of polypropylene was dramatically changed. The cell size distribution, cell diameter, cell density, volume expansion ratio, and foaming rate of radiation-cross-linked polypropylene under different foaming conditions were analyzed and compared. It was found that radiation cross-linking favors the foamability and formation of well-defined cell structures. The optimal absorbed dose with the addition of 2 wt % TAIC was 30 kGy. Additionally, the foaming temperature window was expanded to about 8 °C, making the handling of scCO2 foaming of isotactic polypropylene much easier.

Preparation and Utilization of CaF2-ZrO2 as a Novel Solid base for the Synthesis of Dimethyl Carbonate from Methanol and Propylene Carbonate

Abstract: The effect of preparation method and calcination temperature on the structure and catalytic performance of CaF 2 -ZrO 2 catalysts was investigated. It was found that CaF 2 -ZrO 2 catalyst prepared by coprecipitation method and calcined at 800°C showed both high activity and stability for the synthesis of dimethyl carbonate from propylene carbonate and methanol.