Preparation Of Activated Carbon Supported Fe Catalyst And It Application In Catalytic Methane Decomposition

Catalytic methane decomposition (CMD) to hydrogen and carbon is an interesting alternative to other conventional hydrogen production routes, such as steam reforming of methane, partial oxidation of methane, etc., since COX emissions can be potentially avoided. Both transition metals such as Fe, Co, Ni and carbon material can be used as the catalyst for catalytic methane decomposition. Compared with metal catalyst with high initial catalytic activities and poor stability, carbon catalyst is relatively inexpensive, abundant raw materials and resistant to carbon deposition. However, low catalytic activity limits its industrial utility. Therefore, it is expected to prepare the activated carbon supported metal catalyst with good catalytic performances. In this paper, carbon supported Fe catalysts were prepared by directly adding the Fe salts to the carbon precursor or impregnation method by using commercial coconut shell carbon as the carrier, and characterized by XRD, H2-TPR, SEM analyses, and their catalytic performances in CMD were also examined.Fe catalysts supported on the activated carbon were directly prepared by KOH activation method using coal direct liquefication residue (CLR) as the carbon precursor, ferric nitrate as the Fe precursor. The characterization results showed that Fe(NO3)3added to the carbon precursor can be in-situ reduced to Fe by using the carbon reducibility at high temperature during the carbonization. The effects of the preparation conditions including the ratio of KOH to CLR, Fe sources, Fe loading and the carbonization program were also investigated. It was found that higher catalytic activity and stability were obtained on the carbon supported Fe catalyst prepared at the KOH/CLR ratio of2, ferric nitrate as the Fe precursor and the carbonization temperature of900℃. Low volumetric hourly space velocity and high reaction temperature are conducive to catalytic methane decomposition. The Fe loading also has obvious effect on the methane conversion. When Fe loading is25%, the prepared catalyst shows the best catalytic performance, where Fe plays a dominant role in the reaction. Compared with the activated carbon supported Fe catalyst by the traditional preparation process, the catalyst prepared by our method exhibited good catalytic performances.Commercial coconut shell activated carbon (AC) supported Fe-Al3O3catalysts were prepared by impregnation method in-situ reduced to Fe by using the carbon reducibility and used for catalytic methane decomposition to hydrogen. The XRD and H2-TPR results showed that ferric nitrate on AC support was directly reduced to Fe metal by the reducibility of carbon at870℃. The loading amount and Fe/Al2O3weight ratio affect the textural properties and catalytic methane decomposition. The surface area and pore volume of the catalyst decrease with the loading of Fe and Al2O3. Mesopores with size of about4.5nm can be formed at the loading of20%-60%and promote the catalytic activity and stability. When the Fe/Al2O3ratio is16/24to24/16at the loading of40%, the resultant catalysts show narrow mesopore distributions and relative high methane conversion. Al2O3as the promoter can improve catalytic activity and shorten transitional period of Fe supported AC catalyst.