| Abstract: | The catalytic behavior of three nickel catalysts, viz. nickel supported on η-alumina and nickel supported on zeolite Y (prepared by impregnation and ion exchange methods) were investigated for the methanation reaction. All the catalysts were reduced in flowing hydrogen at 723 K for times varying from 6 h to 24 h. The catalytic activities of these catalysts were determined using a differential flow reactor. The catalysts were characterized using the techniques of hydrogen chemisorption and x-ray diffraction. Nickel metal areas were found to increase with reduction time for all catalysts. X-ray diffraction studies showed that crystallite size varied with reduction time in the case of Ni/zeolite Y catalyst (both impregnated and ion exchanged). Turnover numbers were found to vary with crystallite size and the maximum values of the turnover number were obtained for the catalysts having crystallite sizes of 14-16 nm. There appears to be strong evidence that reduction time can have an effect on catalytic activity; possibly by its effect on crystallite size. The effect of support on catalytic activity was more complicated as there appeared to be an interaction with reduction time. However, nickel/η-alumina appeared to be a more active catalyst than nickel/zeolite Y. |
