摘要: Coal and char are essential energy sources for the process industry. Insightful understanding of those molecules is useful to explore reactivities of coal and char. Therefore, coal and char molecular structures were investigated at atomic level using Materials Studio 7.0 software. Firstly, coal and char initial structures were constructed based on reported literatures. Secondly, those structures were improved by molecular mechanics, where functional group fragments were added to satisfy the property of coal or char. Then, the subsequent structures were optimized by annealing dynamics simulation to adjust density and elementary composition. Finally, the potential energies of coal and char were calculated using energy minimization method. It was pointed out that the estimated densities and elementary composition were agreements with the published literatures, which indicated that those structures were valid and reasonable. From the simulated results, it was shown that the Coulomb energy and van der Waals energy played a much more important role than other energies during the stabilizing molecular construction process. Thus, it was inferred that the weak bond was predominant in the thermal processing of coal or char. In addition, this work demonstrated that the molecular simulation technology was meaningful to construct the complex macromolecular structure.
摘要: This work presents a synthesis of bimetallic NiMo and NiW modified ZSM-5/MCM-41 composites and their heterogeneous catalytic conversion of crude palm oil (CPO) to biofuels. The ZSM-5/MCM-41 composites were synthesized through a self-assembly of cetyltrimethylammonium bromide (CTAB) surfactant with silica-alumina from ZSM-5 zeolite, prepared from natural kaolin by the hydrothermal technique. Subsequently, the synthesized composites were deposited with bimetallic NiMo and NiW by impregnation method. The obtained catalysts presented a micro-mesoporous structure, confirmed by XRD, SEM, TEM, EDX, NH3-TPD, XRF and N2 adsorption-desorption measurements. The results of CPO conversion demonstrate that the catalytic activity of the synthesized catalysts decreases in the series of NiMo-ZSM-5/MCM-41 > NiW-ZSM-5/MCM-41 > Ni-ZSM-5/MCM-41 > Mo-ZSM-5/MCM-41 > W-ZSM-5/MCM-41 > NiMo-ZSM-5 > NiW-ZSM-5 > ZSM-5/MCM-41 > ZSM-5 > MCM-41. It was found that the bimetallic NiMo-and NiW-ZSM-5/MCM-41 catalysts give higher yields of liquid hydrocarbons than other catalysts at a given conversion. Types of hydrocarbon in liquid products, identified by simulated distillation gas chromatography-flame ionization detector (SimDis GC-FID), are gasoline (150-200 ℃; C5-12), kerosene (250-300 ℃; C5-20) and diesel (350 ℃; C7-20). Moreover, the conversion of CPO to biofuel products using the NiMo-and NiW-ZSM-5/MCM-41 catalysts offers no statistically significant difference (P > 0.05) at 95% confidence level, evaluated by SPSS analysis.
摘要: Polyoxymethylene dimethyl ethers (H3CO(CH2O)nCH3, PODEn or DMMn, n ≥ 2) with unique physical and chemical properties are a potential additive for diesel fuels, which can effectively enhance the combustion efficiency and reduce the emission of pollutants. In this work, a series of pure PODEn components (n=2-5) were synthesized from methylal and trioxymethylene and obtained with high purity through collaborative separation; their structure and properties were characterized by NMR, FT-IR, Raman, and DFT calculation and a detailed assignment of the expressions in the spectrogram to the various groups was performed. The density and viscosity of PODEn were measured at 298.15-323.15 K. The results indicate that the density and viscosity of PODEn decrease gradually with the increase of temperature. Meanwhile, with the increase in the number of -CH2O-units (n) from 2 to 5, the density, viscosity, flash point, pour point, and the heat of fusion and solidification of PODEn are all increased. These results are valuable for the practical synthesis and application of PODEn.
摘要: Utilizing microbial fuel cells (MFCs) is a promising technology for energy-efficient domestic wastewater treatment, but it still faces practical barriers such as low power generation. In this study, the LaMnO3 perovskite-type oxide nanoparticles and nickel oxide/carbon nanotube/polyaniline (NCP) nanocomposite (the cathode and anode catalysts, respectively) have been prepared and used to enhance power density of MFC. The prepared La-based perovskite oxide catalysts were characterized by X-ray diffraction (XRD) and scanning electron microscopies (SEM). The electrocatalytic properties of the prepared catalysts were investigated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and Tafel plot at ambient temperature. Results show the exchange current densities of LaMnO3/carbon cloth cathode and NCP nanocomposite/carbon cloth anode were 1.68 and 7 times more compared to carbon cloth cathode, respectively. In comparison to the bare carbon cloth anode, the MFC with the modified electrodes shows 11 times more enhancement in power density output which according to electrochemical results, it can be due to the enhancement of the electron transfer capability. These cathodic and anodic catalysts were examined in batch and semi-continuous modes to provide conditions close to industrial conditions. This study suggests that utilizing these low cost catalysts has promising potential for wastewater treatment in MFC with high power generation and good COD removal efficiency.