Jianfen Li

ZnBr2 supported on silica-coated magnetic nanoparticles of Fe3O4 for conversion of CO2 to diphenyl carbonate

A magnetic Fe3O4@SiO2–ZnBr2 catalyst was prepared by supporting ZnBr2 on silica-coated magnetic nanoparticles of Fe3O4 and used as a recoverable catalyst for the direct synthesis of diphenyl carbonate (DPC) from CO2 and phenol in the presence of carbon tetrachloride. The as-prepared catalyst was characterized by infrared spectroscopy (IR), powder X-ray diffraction (XRD), a X-ray photoelectron spectrometer (XPS) and BET. Zn loading in the supported catalyst and leaching during the reaction process were determined by atomic absorption spectroscopy (AAS). It was found that Fe3O4@SiO2–ZnBr2 showed higher catalytic activity than homogenous ZnCl2 and ZnI2 as well as homogenous ZnBr2. With this new catalyst under optimized conditions, a yield of DPC at 28.1% was obtained. The heterogeneous catalyst Fe3O4@SiO2–ZnBr2 can also be recovered by a permanent magnet after the reaction and reused up to 4 times without noticeable deactivation.

Enhancement of CO2 capture performance of aqueous MEA by mixing with [NH2e-mim][BF4]

Alcohol amine solutions have a high absorption capacity and rate for CO2 capture, however, there are some shortcomings such as high energy-consumption and low stability. To enhance CO2 capture performance of aqueous MEA, a functional ionic liquid ([NH2e-mim][BF4]) was introduced based on the advantages for CO2 capture. Absorbents were prepared with the molar concentration ratio of [NH2e-mim][BF4] to the 30 vol% aqueous MEA of 0 : 10, 1 : 9, 2 : 8, 3 : 7, 4 : 6 and 6 : 4. The density and the viscosity of the investigated absorbents were measured and the effects of the molar fraction of [NH2e-mim][BF4] (nI) and temperature on CO2 absorption performance were investigated. CO2 desorption performance of the solvent at different temperatures was discussed. The stability performance of the absorbent with nI of 2 : 8 (I/M2:8) was examined by five consecutive cyclic tests. The results showed that for pure CO2, the I/M2:8 displayed the highest absorption performance at 303 K under 1 bar: a comparable CO2 absorption capacity of the 30 vol% aqueous MEA and a higher CO2 absorption rate at the later absorption stage. Moreover, with the increase of temperature, CO2 absorption capacity and rate decreased, while CO2 desorption efficiency and rate increased. 393 K was chosen as the optimum desorption temperature with the desorption efficiency of 99.31%. The introducing of IL contributed to CO2 desorption performance of the absorbents significantly. The properties (CO2 absorption capacity, mass loss, density and viscosity) of the I/M2:8 during the cycles suggested that the IL-MEA mixture had an excellent stability performance.

Nano-montmorillonite modified foamed paste with a high volume fly ash binder

This laboratory study explores a cost-effective and environmental friendly foamed paste with satisfactory physical properties and outstanding thermal insulation properties. Such a composite material was made by using a high volume of class F coal fly ash as a replacement of Portland cement (70% by mass) and nano-montmorillonite as an admixture. Replacing cement with fly ash at high levels is environmentally and economically desirable, as this not only reduces the energy and carbon footprint of the foamed paste, but also diverts the coal fly ash from the waste stream. A statistical design of experiments was adopted and executed to investigate the effects of various factors on the properties of the composite. At the age of 28 days, the pastes exhibited a high compressive strength ranging from 1.77 MPa to 6.51 MPa and a low thermal conductivity in the range of 0.071 W (m−1 K−1) to 0.173 W (m−1 K−1). Two foamed mixes were chosen for further investigation as they presented the best and worst performance as a thermal insulation material. The scanning electron microscopy shed light on the best foamed mix, which contains 70% fly ash, 30% cement, and 1% nano-montmorillonite, and how its microstructure differed from that of the worst mix without nano-montmorillonite. The Ca content, Si/Ca ratio and Al/Ca ratio were obtained from energy-dispersive X-ray spectroscopy of hardened samples, and used to help explain the observed strength difference between these two mixes. X-ray diffraction was also employed to elucidate the hydration mechanism of HVFC foamed paste.

Synthesis of 5-hydroxymethyl furfural from cellulose via a two-step process in polar aprotic solvent

The synthesis of 5-hydroxymethyl furfural (HMF) from cellulose via a two-step process was investigated. To optimize reaction conditions, the separate conversion of cellulose and glucose was first performed in tetrahydrofuran (THF) and N, N-dimethylformamide (DMF) via a one-step process using hosphotungstic acid (PHA) as catalyst. The direct conversion of cellulose to HMF was then performed via the two-step process. The first step and the second step were carried out in THF and the mixture solvent composed of THF/DMF, respectively. Cellulose was converted to HMF and glucose in the first step in THF. Both of cellulose and the as-formed glucose were then converted to HMF in the second step. The conversion of cellulose to HMF and glucose were significantly improved by the two-step process, and the total yield of HMF and glucose was elevated from 52.1 to 97.0%. A possible mechanism for the formation of HMF from cellulose via the two-step process was also proposed.