Xiuqin Dong

Preparation of a novel carbon-based solid acid from cassava stillage residue and its use for the esterification of free fatty acids in waste cooking oil

A novel carbon-based solid acid catalyst was prepared by the sulfonation of incompletely carbonized cassava stillage residue (CSR) with concentrated sulfuric acid, and employed to catalyze the esterification of methanol and free fatty acids (FFAs) in waste cooking oil (WCO). The effects of the carbonization and the sulfonation temperatures on the pore structure, acid density and catalytic activity of the CSR-derived catalysts were systematically investigated. Low temperature carbonization and high temperature sulfonation can cause the collapse of the carbon framework, while high temperature carbonization is not conducive to the attachment of SO3H groups on the surface. The catalyst showed high catalytic activity for esterification, and the acid value for WCO is reduced to below 2mg KOH/g after reaction. The activity of catalyst can be well maintained after five cycles. CSR can be considered a promising raw material for the production of a new eco-friendly solid acid catalyst.

One-step synthesis of hydrophobic fluorinated ordered mesoporous carbon materials

A series of fluorinated ordered mesoporous carbon (FOMC) materials were prepared by a one-pot method. The FOMC materials were characterized by X-ray diffraction, N2 adsorption–desorption isotherms, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The FOMC materials have well-ordered mesoporous structures with large specific surface areas and uniform pore sizes. Contact angle analysis showed that the FOMCs were more hydrophobic than the corresponding unfluorinated parent material. Thus the incorporation of fluorine improved the hydrophobicity of the carbon materials. This method provides a fast and easy-to-scale-up method for producing ordered mesoporous carbon materials with high hydrophobicity.

A novel highly ordered mesoporous carbon-based solid acid for synthesis of bisphenol-A

A novel highly ordered mesoporous carbon-based solid acid was prepared through controlled sulfonation of F127 type mesoporous carbons prepared via a solvent evaporation induced self-assembly method. The influence of sulfonation temperature was investigated, suggesting an optimum temperature of 180 °C. The sulfonated samples were characterized by means of N2 adsorption–desorption, XRD, TEM and FT-IR. The SO3H group-functionalized mesoporous carbon showed a specific surface of 393 m2 g−1, pore volumes of 0.33 cm3 g−1, an average pore size of 3.7 nm and a SO3H group density of 1.71 mmol g−1. The mesoporous carbon-based solid acid effectively catalyzed the condensation of phenol with acetone. The increased catalytic performance was attributed to a uniform mesoporous structure and hydrophobic surface properties.

Surface carbon species formation from ethylene decomposition on Pd(100): a first-principles-based kinetic Monte Carlo study

Based on the activation barriers and reaction energies from periodic density functional calculations, we conducted kinetic Monte Carlo (kMC) simulations of surface carbon species formation from ethylene decomposition on a Pd(100) surface. A comprehensive reaction network of ethylene decomposition involving such intermediates as CH2CH, CHCH, CH2C, CHC, CC, CH2 and CH was proposed. Our kMC simulations show that the most probable pathway of ethylene decomposition on Pd(100) is CH2CH2 → CH2CH → CH2C → CHC → CC, among which the dehydrogenation of CH2CH2 to CH2CH is the rate-limiting step with the activation barrier of 1.51 eV, followed by CH2CH2 → CH2CH → CHCH → CHC → CC, whose rate-limiting step is the dehydrogenation of CH2CH to CHCH with the activation barrier of 1.59 eV. The two most probable pathways produce a carbon dimer as the final product, since the activation barrier of the C–C bond cleavage reaction is so high (2.32 eV) that it is almost impossible for it to occur before the metal surface is totally poisoned by surface carbon species. Another three feasible pathways are: (i) CH2CH2 → CH2CH → CHCH → CH → C, (ii) CH2CH2 → CH2CH → CHCH → CHC → CH + C → C and (iii) CH2CH2 → CH2CH → CH2C → CHC → CH + C → C, whose final products contain surface carbon monomers. And the reactions involving C–C bond cleavage are the rate-limiting step of the three pathways. Simple as the reaction network of ethylene decomposition looks, it is still difficult to analyze the decomposition mechanism merely according to the activation barriers from DFT calculations. Our work here demonstrates that kMC simulations can nicely tackle the problem on competitive reaction pathways, each of which involves some reactions with relatively low activation barriers (e.g. the dehydrogenation reactions involved in ethylene decomposition) and some other reactions with relatively high activation barriers (e.g. the C–C bond cleavage reactions involved in ethylene decomposition).