Surface structure changes of nickel-based catalysts in the syngas methanation process

摘要

In order to investigate the surface structure changes of nickel-based catalysts during the syngas methanation process, nickel-based catalysts were prepared with impregnation method and the tests were carried out in a fluidized bed reactor. The test results showed that the catalytic performance declined rapidly with the reaction time. Energy dispersive spectroscopy measurements of the reacted catalyst were carried out and the results indicated that there was carbon observed on the catalysts surface. The carbon deposited on the catalyst surface was removed in a thermogravimetric analyzer to obtain the regenerated catalyst and it was found that the amount of the accumulated carbon on the catalyst surface was 2.09 wt% of the reacted catalyst. N-2 adsorption-desorption measurements were conducted on the fresh catalyst, reacted catalyst and regenerated catalyst. The specific area of the reacted catalyst decreased significantly and could not restore to the original level even after removing the deposited carbon. The pore volume of reacted catalyst increased 16.67% compared to the fresh catalyst while the average pore diameter remained almost no change. The pores existing on the fresh catalyst were mainly the mesopores while the pore size distribution expanded and the macrospores came into being on the reacted catalyst. It can be concluded that a kind of stable carbon was produced on the catalyst surface after methanation process, which caused dramatic changes to the surface textural properties.