Guangsen Song

Amberlyst 15 as a new and reusable catalyst for the conversion of cellulose into cellulose acetate

The acetylation of cellulose using sulfonated Amberlyst 15 as a new and reusable catalyst was investigated. Optimization of the acetylation process was carried out by variation in the amount of added catalyst, acetic acid, and acetic anhydride as well as the reaction conditions, which includes reaction time and reaction medium. Cellulose acetate, with a degree of substitution (DS) value of 2.38 and yield of 54.1%, was obtained under the optimized conditions and characterized using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis-derivative thermogravimetry (TGA-DTG), and differential scanning calorimetry (DSC). The sulfonated polymer catalyst could be easily recovered by centrifugation after acetylation. Both the fresh and recovered catalysts were characterized by means of FTIR, TGA-DTG, DSC, and scanning electron microscopy (SEM), and the recovered catalyst could be successfully reused without further treatment. It was found that Amberlyst 15 possessed excellent catalytic stability, no significant changes in the DS values, and consistent yields of cellulose acetate observed over four reaction cycles.

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.

Mesoporous silica nanoparticles as high performance anode materials for lithium-ion batteries

A facile sol–gel/emulsion approach was employed for the fabrication of mesoporous silica nanoparticles with a large BET specific surface area of 1594 m2 g−1. The as-prepared SiO2 electrode delivers a highly stable specific capacity of as large as 1060 mA h g−1 at a current density of 100 mA g−1 after 90 cycles, exhibiting a good cycling stability.

SiO2@NiO core–shell nanocomposites as high performance anode materials for lithium-ion batteries

SiO2@NiO core–shell nanocomposites of ca. 80 nm in diameter with a thin NiO shell were assembled via a facile online deposition of NiO and investigated as an anode for lithium ion batteries. The results indicated that the specific discharge capacity of the obtained SiO2@NiO core–shell nanocomposite electrode still retains 585 mA h g−1 at a discharge current density of 100 mA g−1 after 60 cycles and presents a coulombic efficiency of almost 100%, exhibiting good cycling stability and excellent rate capability after the first few cycles. This might be accounted for by the reversible lithiation/delithiation of the product Si due to the irreversible lithiation of SiO2 while the irreversible lithiation of NiO to produce metal Ni nanoparticles is responsible for the activation of SiO2, which is demonstrated by comparing the cyclic voltammetries (CVs) and electrochemical impedance spectra (EIS) of SiO2, NiO and SiO2@NiO electrodes.

A facile synthesis of hierarchical MoS2 nanotori with advanced lithium storage properties

MoS2 with a 2D layered structure and high theoretical capacity has been regarded as a promising candidate for anode materials in lithium ion batteries. But its poor cyclic stability and low rate capability hinder its practical applications. Herein, hierarchical MoS2 nanotori consisting of MoS2 nanosheets with an increased interlayer distance were synthesized by a facile hydrothermal reaction for the first time. A possible formation mechanism of the hierarchical MoS2 nanotori is proposed based on the scanning electronic microscopy (SEM) results and the influence of the MoO3 precursor on the morphology of the MoS2 obtained. The hierarchical MoS2 nanotori display superior reversible capacity, good rate capability and improved cyclic performance, which can be attributed to their hierarchical surface, hollow structure feature and increased layer distance. The formation mechanism of hierarchical MoS2 nanotori proposed here should offer a new technique for the design and synthesis of MoS2 with different morphologies using MoO3 as the growth template.

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.