Abstract: An investigation into catalyst was conducted for one-step production of synthetic natural gas from coal in a fixed bed reactor using steam as gasification medium. The reactivity and stability of K-Fe catalyst in multi-cycles, as well as the kinetics model of methanation process and the effect of different coals on methanation, were studied. K15Fe10Ca5 catalyst showed significantly better activity in the coal gasification and methanation reactions at 650℃ and 2 MPa. Furthermore, X-ray diffraction data indicated that some highly active materials, such as K₆Fe₂O₅ were formed by interaction of active components and enhanced reactivity. With the addition of calcium promoter, combination of active components and minerals in coal was prevented and the sulfur in coal could be fixed effectively. In multi-cycle experiments, CH₄ yield remained stable. The methanation mechanism of Shenmu-coal with K15Fe10Ca5 could be described by the modified random pore model proposed, suggesting that interfacial reaction was the control step. The final yield was affected by volatile matter, ash content, and sulfur content.

Key words: coal chemical industry, fixed bed, catalyst, natural gas, reaction kinetics

摘要： 在固定床反应器中，以水蒸气为气化介质，考察了“一步法”煤制天然气K-Fe甲烷化催化剂的催化活性及稳定性，研究了反应动力学，并且考察了不同煤种对煤催化甲烷化的影响。在650℃、2 MPa下，K15Fe10Ca5对于煤气化及甲烷化均具有良好催化活性。XRD分析表明，活性组分K与Fe之间相互作用，形成的K₆Fe₂O₅促进了煤气化及甲烷化反应。Ca助剂的引入抑制了活性组分与煤中矿物质的结合，同时吸收了煤焦释放出的含硫气体，提高了催化剂的活性。在5次循环实验过程中，CH₄产率保持稳定，表明催化剂有较高的稳定性。修正随机孔模型很好地描述了K15Fe10Ca5催化神木煤焦甲烷化的行为，其中界面反应为控制步骤。煤中挥发分、灰分及含硫量等因素都会影响最终的产率。

关键词: 煤化工, 固定床, 催化剂, 天然气, 反应动力学