摘要: 采用MS（Materials Studio 2017）软件中Forcite模块，对自主构建的抚顺油页岩干酪根二维结构模型进行能量最小化分子动力学模拟，通过能量最优化过程得到干酪根初始优化结构。在此基础上进行分子动力学退火模拟，获得全局能量最优化构型，即油页岩干酪根分子三维结构模型。基于密度泛函理论的量子力学模拟方法，计算分析干酪根三维结构模型的动力学、键能、键级、电荷密度等参数，分析化学活性位点，探讨了干酪根热解微观化学演化机理，进而预测了反应性。
摘要: Two NiMo catalysts using the nanosized zeolite HY-Al2O3 composite (labeled as NYA) prepared by mechanical mixing method and sol-gel method as the support were prepared and characterized by XRD, BET, TPD, H2-TPR, HRTEM and FT-IR spectroscopy. The former catalyst possessed larger pore volume and specific surface area, more acid amount, superior reducibility of metal phase and higher dispersion of edge and corner Mo atoms, and showed higher hydrodesulfurization (HDS) performance. Compared with the former catalyst, the latter catalyst had more MoO3 to be converted to active type-Ⅱ NiMoS phase, possessed higher stacking degree and bigger length of MoS2 slabs, and showed lower active phase dispersion. Although the sol-gel method was beneficial to increase the precursor ratio of type-Ⅱ NiMoS phase, the poor pore structure caused by this method inhibited this advantage and reduced the catalytic activity of the catalyst.
摘要: The effect of ethylene diamine tetraacetic acid (EDTA) modification on the physico-chemical properties and catalytic performance of silica nanosprings (NS) supported cobalt (Co) catalyst was investigated in the conversion of syngas (H2 + CO) to hydrocarbons by Fischer-Tropsch synthesis (FTS). The unmodified Co/NS and modified Co/NS-EDTA catalysts were synthesized via an impregnation method. The prepared Co/NS and Co/NS-EDTA catalysts were characterized before the FTS reaction by BET surface area, X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), differential thermal analysis (DTA) and thermogravimetric analysis (TGA) in order to find correlations between physico-chemical properties of catalysts and catalytic performance. FTS was carried out in a quartz fixed-bed microreactor (H2/CO of 2:1, 230℃ and atmospheric pressure) and the products trapped and analyzed by GC-TCD and GC-MS to determine CO conversion and reaction selectivity. The experimental results indicated that the modified Co/NS-EDTA catalyst displayed a more-dispersed phase of Co3O4 nanoparticles (10.9%) and the Co3O4 average crystallite size was about 12.4 nm. The EDTA modified catalyst showed relatively higher CO conversion (70.3%) and selectivity toward C6-18 (JP-8, Jet A and diesel) than the Co/NS catalyst (C6-14) (JP-4).
摘要: A static hydrothermal approach was adopted to synthesize nanosized SiO2-ZSM-5 zeolite in the media of F--OH- with double mineralizers, using tetraethoxysilane, sodium aluminate, and tetrapropylammonium hydroxide as the silicon source, aluminum source, and template agent, respectively. The physical and chemical properties of the synthesized ZSM-5 zeolites were characterized and their catalytic performance was evaluated in the conversion methanol to propene (MTP); the effect of F-/Al2O3 molar ratio on the catalytic performance of synthesized H-ZSM-5 was investigated. The results indicate that an increase in the F-/Al2O3 molar ratio of the synthesis mixture leads to an increase in the surface content of microcrystalline SiO2, accompanying with a decrease in the relative crystallinity, surface area, pore volume, and acid strength and density. With a F-/Al2O3 molar ratio of 12, the SiO2-ZSM-5 zeolite exhibits the best catalytic performance in MTP, with a selectivity of 45% to propene and a propene/ethene (P/E) ratio of greater than 10. It is further hypothesized that the transition state shape selectivity plays an important role in determining the product selectivity in MTP.
摘要: The transesterification of ethylene carbonate (EC) with methanol to synthesis dimethyl carbonate (DMC) and ethylene glycol (EG) over ZnO, La2O3 and Zn-La mixed oxides were explored. The catalysts were prepared by co-precipitation method and characterized by BET, XRD, TG-DSC, CO2-TPD and Hammett titration. The influence of Zn/La atomic ratio, calcination temperature and reaction parameters (reaction temperature, reaction time, catalyst amount) on the catalytic activity were investigated. The results indicated that the binary Zn-La mixed oxide with Zn/La atomic ratio of 2:1 calcined at 500℃ showed the highest catalytic performance for the title reaction due to its strongest basicity, and the amount of strong basic sites of the catalyst should be responsible for the high transesterification activity.
