| Coal gasification as a kind of effective utilization method of lignite always has some restrictions, such as high energy consumption and harsh reaction conditions. Suitable catalyst can reduce the reaction temperature effectively and lower the cost greatly. In order to provide theoretical basis for selection of catalyst, different meatal hydroxide（LiOH, NaOH, KOH, Ca（OH）2, Co（OH）2, Ni（OH）2, Cu（OH）2, and Zn（OH）2） were added into the lignite and then investigate its effect on the properties of steam gasification. Different characterization methods were used to determine structure translation and its corelation with reactivity. It was found that metal hydroxide loading play an important role in the process of steam gasification. Metal hydroxide could influence the existence of carbon form, in which the aromaticity was reduced and the content of C-O-C, C-OH, and C-O was improved. Overall, the effect of alkali metal hydroxide is better than that of Co（OH）2, Ni（OH）2, Cu（OH）2, Zn（OH）2, and Ca（OH）2 is in between LiOH and NaOH, which is highly accordance with the effect on lignite steam gasification.Ca（OH）2 has a good catalytic effect on steam gasification of Shengli lignite without heat pretreatment, and the effect is not remarkable any more when the lignite was pyrolysised under high temperature. In order to explore the catalytic mechanism and find the catalytic active functional group of calcium hydroxide, the demineralized chars prepared at different temperature（room temperature, 300 ℃, 500 ℃, 700 ℃, 900 ℃, and 1100℃）were gasified in an atmosphere of steam with calcium hydroxide addition, and then its structure translation during pyrolysis were characterized by different methods such as FT-IR, SSNMR, XPS, Raman, and XRD. High temperature pretreatment makes catalytic effect of Ca（OH）2 decrease gradually, especially at the temperature of 500 ℃ the decomposition of carboxyl group makes it a big difference and lead to release a large amount of CO2. |
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