Huiquan Li

Cellulose extraction from wood chip in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl).

In the present study, 1-allyl-3-methylimidazolium chloride (AmimCl), an ionic liquid (IL), was used to extract cellulose from pine, poplar, Chinese parasol, and catalpa wood chips. Results show that pine is the most suitable wood species for cellulose extraction with ILs. Its cellulose extraction rate can reach as high as 62% under optimized conditions and its cellulose content is as high as 85% when DMSO/water is used as the precipitant. The dissolution process can be clearly observed by hot stage optical microscopy, and the reaction time can be significantly reduced by microwave irradiation. (13)C CP/MAS NMR, FTIR, XRD, and SEM were used to analyze the cellulose-rich extracts of pine. Results show that IL dissolves pine wood by destroying inter and intramolecular hydrogen bonds between lignocelluloses. The major component of pine extract is cellulose with a homogeneous and dense structure. After extraction, AmimCl can be easily recycled and reused.

A non-phosgene route for synthesis of methyl N-phenyl carbamate derived from CO2 under mild conditions

A non-phosgene route for the synthesis of methyl N-phenyl carbamate from dimethyl carbonate and N,N′-diphenyl urea was studied under the mild conditions of atmospheric pressure. A series of homogenous and heterogenous catalysts were screened, and the homogenous catalyst sodium methoxide exhibited excellent activity in the synthesis of methyl N-phenyl carbamate under atmospheric pressure. The parameters of molar ratio of reactants, catalyst concentration, reaction time, number of additions of catalyst, reaction temperature and solvents in the synthesis of methyl N-phenyl carbamate were also investigated. A possible reaction mechanism with catalyst sodium methoxide was proposed.

Homogeneous Preparation of Cellulose Acetate Propionate (CAP) and Cellulose Acetate Butyrate (CAB) from Sugarcane Bagasse Cellulose in Ionic Liquid

Cellulose acetate butyrate (CAB) and cellulose acetate propionate (CAP) were prepared homogeneously in a 1-allyl-3-methylimidazolium chloride (AmimCl) ionic liquid system from sugarcane bagasse (SB). The reaction temperature, reaction time, and molar ratio of butyric (propionic) anhydride/anhydroglucose units in the cellulose affect the butyryl (B) or propionyl (P) content of CAB or CAP samples. The (13)C NMR data revealed the distribution of the substituents of CAB and CAP. The thermal stability of sugar cane bagasse cellulose was found by thermogravimetric analysis to have decreased after chemical modification. After reaction, the ionic liquid was effectively recycled and reused. This study provides a new way for high-value-added utilization of SB and realizing the objective of turning waste into wealth.

Magnesium oxide nanosheets as effective catalysts for the synthesis of diethyl carbonate from ethyl carbamate and ethanol

A series of MgO catalysts were prepared by thermal decomposition and precipitation methods. Their catalytic performance was evaluated in the synthesis of diethyl carbonate (DEC) from ethyl carbamate (EC) and ethanol. Among them, MgO prepared using sodium carbonate as the precipitant and calcined at 450 °C (MgO-SC-450) exhibited much higher catalytic activity. An excellent DEC yield of 58.0% with a high DEC selectivity of 92.1% could be achieved over the MgO-SC-450 catalyst under optimized reaction conditions: 210 °C, ethanol/EC molar ratio of 10, and 3 h. Moreover, the catalytic activity could be essentially retained during recycling experiments. The structure and surface basicity of the MgO catalysts were characterized by X-ray diffraction (XRD), Mastersizer 2000, N2 adsorption, field-emission scanning electron microscopy (FE-SEM), and temperature-programmed desorption of CO2 (CO2-TPD). It was found that MgO-SC-450 possessed nanosheet morphology. Furthermore, a larger amount of appropriate medium basic β sites of MgO-SC-450 with the peak located between 225 °C and 275 °C was favourable for obtaining much superior catalytic activity. Quasi in situ FT-IR experiments were carried out to elucidate the adsorption behaviours of reactants. It was found that EC could be effectively activated and ethanol could be dissociated to a strong nucleophilic ethoxy group by MgO. In addition, theoretical calculation proved the co-adsorption of EC and ethanol on the MgO surface. Based on the results of quasi in situ FT-IR experiments and theoretical calculation, a plausible reaction mechanism has been proposed for the catalytic reaction.

Non-isothermal thermal decomposition reaction kinetics of dimethylhexane-1,6-dicarbamate (HDC)

The thermal decomposition behavior and reaction kinetics of dimethylhexane-1,6-dicarbamate (HDC) were investigated by TG-DTG, DSC and IR techniques. It is shown that the decomposition process can be divided into 3 main stages and the first stage is the thermal decomposition reaction for HDC to dimethylhexane-1,6-diisocyanate (HDI). The main gaseous products of the decomposition are CO(2) and CH(3)OH. The kinetic parameters of the reaction for HDC to HDI are Ea=119.51 kJ mol(-1), lg(A/s(-1))=14.82, respectively. The kinetic equation is d(α)/d(t) = 10(15.12)(1-α)(3/2)e(-1.4375×10(4)/T).

Influence of support on the performance of copper catalysts for the effective hydrogenation of ethylene carbonate to synthesize ethylene glycol and methanol

Hydrogenation of ethylene carbonate (EC) is an attractive and promising approach for indirect hydrogenation of CO2 to co-produce ethylene glycol (EG) and methanol (MeOH). In this work, thermodynamics of EC hydrogenation was firstly calculated, and the results disclosed that EC hydrogenation is exothermic (ΔrHθm = −71.59 kJ mol−1) and thermodynamically favorable (ΔrGθm = −25.62 kJ mol−1). The mesoporous silica supported copper catalysts were successfully prepared by facile ammonia evaporation method using KIT-6, MCM-41 and SBA-15 as support materials. The as-prepared Cu/KIT-6, Cu/MCM-41 and Cu/SBA-15 were thoroughly characterized by N2 physisorption, ICP-AES, N2O titration, FT-IR, XRD, H2-TPR, TEM, XPS and XAES. It was found that copper nanoparticles were well dispersed on these supports. Interestingly, a larger metallic Cu surface area with higher dispersion was obtained on SBA-15 when compared with KIT-6 and MCM-41. Furthermore, Cu0 and Cu+ species in various ratios were verified to co-exist on the surfaces of the three catalysts, which originated from CuO and copper phyllosilicate, respectively. The catalytic performances showed that Cu/SBA-15 exhibited a superior catalytic activity with a TON of 22.0 and 11.4 (mol mol−1) towards EG and MeOH, respectively. Importantly, 100% of EC conversion, 94.7% of EG yield and 62.3% of MeOH yield were achieved within a short reaction time of 4 h over Cu/SBA-15 under optimized conditions. The synergetic effect between Cu0 and Cu+ species, in which it was proposed that Cu0 species dissociated H2, while Cu+ species absorbed the carbonyl group of EC, was responsible for the higher catalytic activity of Cu/SBA-15.

High performance long chain polyamide/calcium silicate whisker nanocomposites and the effective reinforcement mechanism

PA1012/calcium silicate whisker nanocomposites with contents of whisker ranging from 10 wt% to 40 wt%, are prepared by twin screw extruder without any additions of coupling agent. The effect of whisker on the matrix is analyzed by the studies of morphology, the mechanical properties, water absorption and thermal stabilities. SEM micrographs obviously demonstrate, even under the high filler content of 40 wt% and without surface treatment, calcium silicate whisker can be homogeneously dispersed in polyamide, directly leading to the enhanced mechanical properties. The mechanism of higher efficiency of reinforcement is needle-like shape whisker, having access to be intercalated, and mutual affinity caused by hydrogen bonding interaction between carbonyl group in polyamide chain and hydroxyl group in whisker surface. Both aspects attach matrix with excellent stress-transfer properties. In addition, with the assistance of whisker, the nanocomposite favors an improved water absorption as well as thermal stability, which is intimately associated with physical performance.

The direct adsorption of low concentration gallium from fly ash

ABSTRACT This study is mainly focused on the direct adsorption of low concentration gallium from the feed solution in pre-desilication soda-lime sintering process from coal fly ash. The adsorption kinetics, mechanism, and the influence of impurities, cyclic times, and eluant content are systematically researched. Results showed that the adsorption capacity was 2.89 mg/g resin with gallium concentration of 50 mg/L. The adsorption mechanism could be explained by the interaction between the oxygen atoms and nitrogen atoms of amidoxime group. Gallium was eluted efficiently by NaOH and Na2S mixed solution and the concentration could be reached to 2400 mg/L.

Molecular-Level Investigation of the Adsorption Mechanisms of Toluene and Aniline on Natural and Organically Modified Montmorillonite.

The present work reports the adsorption mechanisms of aniline and toluene in dry and hydrated montmorillonite (MMT-Na and MMT-Na-W) and tetramethylammonium-cation-modified MMT (MMT-TMA) as determined through density functional theory. These theoretical investigations explicitly demonstrate that cation-π interactions between Na(+)/TMA(+) cations and aromatics play the key role in adsorption of organics over MMT-Na and MMT-TMA. Weak hydrogen bonds between the H atoms of organics and basal O atoms of tetrahedral silicate also stabilize the location of organics. The combination of interactions between water and basal O atoms and between organics and water molecules in hydrated MMT complexes strengthens the adsorption of organics on MMT, resulting in higher formation energies in hydrated organically intercalated MMTs than in the corresponding dry complexes. The adsorption of organics also changes frontier orbital distributions and consequently promotes the preferential occurrence of reactions on the organics rather than on the MMT layers. These adsorption mechanisms predicted by theoretical investigation can be used to explicate the adsorption of aromatic organics on aluminosilicates with different external environment.

Vanadium metabolism investigation using substance flow and scenario analysis

Vanadium is a vital strategic resource, and vanadium metabolism is an important part of the national socio-economic system of China. This study conducts accounting and scenario analysis on the life cycle of vanadium metabolism in China. Based on the characteristics of vanadium life cycle and substance flow analysis (SFA) framework, we present a quantitative evaluation of a static anthropogenic vanadium life cycle for the year 2010. Results show that anthropogenic vanadium consumption, stocks, and new domestic scrap are at 98.2, 21.2, and 4.1 kt, respectively; new scrap is usually discarded. The overall utilization ratio of vanadium is 32.2%. A large amount of vanadium is stockpiled into tailings, debris, slags, and other spent solids. A scenario analysis was conducted to analyze the future developmental trend of vanadium metabolism in China based on the SFA framework and the qualitative analysis of technology advancement and socio-economic development. The baseline year was set as 2010. Several indicators were proposed to simulate different scenarios from 2010 to 2030. The scenario analysis indicates that the next 20 years is a critical period for the vanadium industry in China. This paper discusses relevant policies that contribute to the improvement of sustainable vanadium utilization in China.