Using Supported Metal Catalysts In Direct Coal Liquefaction And Pyrolysis Of Model Compounds Under Methane Atmosphere

Coal resources are relatively abundant in China. It’s of great strategic significance to reduce oil imports and maintain national energy safety by developing direct coal liquefaction (DCL) technology. But DCL technology is mainly conducted under hydrogen atmosphere; about thirty percent costs of DCL are used in hydrogen generation. If coal can be liquefied by using less expensive gas, the economics of DCL technology will be greatly improved.In this paper, supported metal catalysts with ferric nitrate, cobalt nitrate, nickel nitrate, ammonium molybdate and ruthenium chloride as metal catalysts precursors, two microporous molecular sieves of SAPO-11and SAPO-34, two mesoporous molecular sieves of MCM-41and SBA-15as catalyst supports were prepared by volume impregnation method for DCL and pyrolysis of model compounds under methane atmosphere. Through the work, mainly conclusions are as followings:1. In the condition of tetralin and1-methylnaphthalene mixed solvent (volume ratio3:1), the results show that Ni/SAPO-34have the best catalytic activity with oils and gases yield of32.1%, twice than without catalyst, total conversion of the coal liquefaction is37.4%, higher16%than without catalyst. As catalyst supports, SAPO-34is better than SAPO-11in microporous molecular sieves, MCM-41is better than SBA-15in mesoporous molecular sieves. Nickel-based catalysts have the best catalytic activity, while iron-based catalysts are the worst. Due to the influence of metals and supports, the order of supported mental catalysts activity is also different.2. X-ray diffraction (XRD), N2absorption-desorption, NH3temperature programmed desorption (NH3-TPD) and H2temperature programmed reduction (H2-TPR) were used to characterize the Nickel-based catalysts with different supports. It is showed that large specific surface area, moderate pore volume and pore diameter distribution, weak interaction between metal and support were feasible for high coal conversion under CH4atmosphere.3. Optimization of reaction conditions for Ni/SAPO-34as catalyst in DCL under CH4atmosphere are solvent/coal ratio2:1(wt/wt), reaction temperature450℃, initial pressure7.0MPa(cold), reaction time1h. With the Ni/SAPO-34catalyst the coal conversion and light components yields under CH4atmosphere are not less than those under H2atmosphere in the optimal conditions.4. The thermal cracking of model compounds was studied in the presence of nitrogen or methane with Ni/SAPO-34as catalyst. It is showed that the catalyst catalyses the decomposition of the aryl-alkyl and CH2-CH2bonds, inhibits the dehydrogenation and promotes active hydrogen transfer to the hydrocracking active sites of model compounds and to hydrogenate them. The pyrolysis under methane is superior to the nitrogen and temperature plays a key role in the pyrolysis, when increasing temperature, the pyrolysis is greatly promoted. The conversion of1,2-diphenylethane (DPE) is decreased when adding solvents, hydrogen donor solvents may inhibit the hydrocracking of DPE, tetralin gives the strongest inhibiting effect and other solvents are weak.