The Preliminary Study Of Direct Coal Liquefaction Under Methane Atmosphere

China is a country with vast indigenous reserves of coal while shortage of oil. It is necessary for the ensuring of the country’s energy supply by developing the direct coal liquefaction (DCL) technology. The direct coal liquefaction technology investment costs in our country are high, at about10,000yuan per ton, which is, about the same scale petrochemical enterprises6-7times. What’s more, thirty percent costs of direct coal liquefaction are used in hydrogen generation. If coal can be liquefied by using an alternative, less expensive gas, the economics of direct coal liquefaction technology will be greatly improved.In this paper, coal liquefaction under the mixture atmosphere of methane and hydrogen was studied to enhance the efficiency of coal liquefaction and reduce the overall cost. The effect of solvent on coal liquefaction under three kinds of gases including methane was studied, and the coal liquefaction behaviors with respect to different solvents and catalysts,both in methane and hydrogen, were also examined. Through the work, we draw the following conclusions:(1)In the presence of tetralin(THN), conversion is around54.0%, no matter under the H2, CH4,or N2atmospheres. It can be seen that if a sufficient amount of hydrogen-donating solvent is added in the experiment, the influence of atmosphere will be smaller on the total conversion.(2)Although the coal conversion of DCL reaction under methane is low than hydrogen, but the coal conversion is still significantly higher than under nitrogen, representing that methane atmosphere in DCL reaction having a certain activity.(3)When the liquefaction reaction solvent is pure methylnaphthalene (MN) or a mixed solvent of THN and MN, coal total conversion increased with the ratio of hydrogen in the mixture hydrogen and methane atmosphere. In the presence of THN, hydrogen promoting effect on the reaction is more obvious.(4)There is no synergistic effect in the reaction of hydrogen and methane while MN as a solvent. However, the synergistic effect of the hydrogen and methane atmosphere comes along with the added of hydrogen donor solvent, which indicating that the solvent certain synergies in DCL reaction of hydrogen and methane. The better solvent hydrogen donor ability is, the stronger the synergistic effect of hydrogen and methane.(5)The results show that Ni/SAPO-34is more effective than other catalysts in this paper. The total conversion of the coal liquefaction is57.6%, more over than the conversion of coal under the hydrogen (54.6%) in the same condition.(6)It appears that the carrier SAPO-34plays a leading role in catalytic ability of Ni/SAPO-34rather than nickel, which plays a role in transforming heavy components to light. And compared to nickel oxide, Ni was the active component in the reaction.(7)There is a clearly trend that the loaded metals had a significant effect on catalysts; the catalysts of loaded Ni on the surfaces of the zeolites were more effective under the methane, while the catalysts of PbO2were detrimental.(8)When the Ni/SAPO-34is used in the DCL reaction under a methane atmosphere, the best nickel loading and catalyst additive amount are7.0wt%and2.0wt%respectively.