Effect of support porosity on coke deposition and sintering of nickel based catalysts used for carbon dioxide reforming of methane

Abstract

Carbon dioxide reforming of methane has been investigated extensively in recent years since it converts two greenhouse gases into high-value added chemicals. It provides syngas production with H2:CO ratio of 1:1. The syngas produced is utilized in the production of hydrocarbons. However, the main problem for this application is the lack of a stable and effective catalyst. Nickel-based catalysts are widely tested in DRM due to their low cost, availability and high initial activity. The major drawback of such catalysts is that they suffer from coke deposition which leads to their deactivation. In this work, two series of Ni5/silica supports are tested: mesoporous and nonporous. Some of which are prepared at the laboratory and others which are commercial supports. Ni was deposited using two solvents method and incipient wetness impregnation techniques. Further to catalysts preparation, calcined samples were characterized by N2 sorption, TPR, XRD, TEM and SEM. The results showed a good dispersion of Ni in the pores of silica based supports. Catalysts were reduced in situ and their activity/stability were tested under an equimolar ratio of methane and carbon dioxide. The activity was directly related to the average size of particles for nonporous supported catalysts. For the porous catalysts, internal nickel particles showed higher activity than external ones. However, very small internal ones (3 nm) deactivate due to lack of carbon nanotubes formation. In the future, further advanced characterization techniques are required to determine the type of coke deposited and the reason of activity loss for some of the spent catalysts.