Preparation Of Coal-based Activated Carbon And Its Application In Catalytic Methane Decomposition To Hydrogen

Catalyticmethanedecomposition(CMD) process is a potential route of hydrogen production owing to its simple process, easy separation of products and no production of COx. Compared with the traditional methods of hydrogen production, the CMD method can decrease cost because of no COxsequestration, and is environmentally attractive. Transition metals and carbon materials can be usedas the catalysts. Compared to metal catalysts, the latter have been used in the CMD reaction due toits advantages such as low cost, high temperature resistance, etc.In this paper, activated carbons were prepared by KOHactivation and used as catalystsin hydrogen production. Coal samples with different contents of minerals, heat pretreated samples at200-700℃, and the pyrolysis chars under different atmospheres were chosen as the carbon precursors to prepare the activated carbons. The effect of the structure of precursors on the activated carbons and catalytic performance in methane decomposition was investigated.First, the preparation conditions of activated carbons were examined and used in the catalytic decomposition of methane. The results showed that appropriate conditions are the weight ratio ofKOH to the precursor being2:1, the activation temperature of900℃, the activation time of120min, the heating rate withl℃/min in the range of600-900℃.Four kinds of coal samples including Yima(YM), Pingdingshan(PDS), Jiaozuo coarse slime (JZ) and Shenmu(SM) were chosen as the carbon precursors to prepare activated carbons by KOH activation method. The resultant carbon materials were characterized by means of coal analysis, TG, N2adsorptionand XRD, and used to catalyze the decomposition of methane. The results showed that the ash and volatile mattercontents in coal influence the porositydevelopment of prepared activated carbons.The release of volatile matter is preferable to the porosity development and higher mineral matter contents result in higher V, of activated carbons. Treatment of coal with different acid solutions (HNO3, HF and HCl) resulted in the removal of different inorganic components, thus, the different catalytic performances in CMD of the prepared activated carbons.Shenmu coal was pretreated at the temperature of200to700℃, and used as the precursors to preparea series of activated carbons (ACs) by the activation by KOH. The resultant coal and carbon samples were characterized by proximate analysis, elemental analysis, FT-IR, TG and N2adsorption,and used as the catalysts for the methane decomposition to hydrogen. The results show that the ACs prepared from pretreated coals in low temperature range of200-500℃exhibited higher catalytic stability than that prepared from raw coal in methane decomposition. However, the catalytic activity and stability of resultant AC catalysts decreases with further increasing the heat pretreatment temperature from500to700℃, which is related with the variety ofthe BET surface area (SBET) and total volume (Vt) of ACs. Pretreatment at lower temperatures results in higher mesoporosity and larger pore volume. As a result, low temperature heat pretreatment can be used as an effective method to obtain coal-based activated carbons with high catalytic performance for methane decomposition to hydrogen.