Effect of Ni-CNTs/mesocellular silica composite catalysts on carbon dioxide reforming of methane

Abstract

In this research, the novel composite catalysts between nickel and carbon nanotubes (CNTs) over mesocellular silica (MS) support were synthesized with an attempt to improve their stability to deactivation due to coke deposition in dry reforming reaction. Accordingly, the MS support was primarily prepared based on the synthesis of SBA-15 mesoporous silica with 1,3,5-trimethylbenzene (TMB) as a pore expanding agent. After that, nickel metal was loaded onto the MS support by using an incipient-wetness impregnation method, followed by CNTs synthesis via catalytic chemical vapor deposition (CCVD) technique through tip-growth mechanism. It was found that the existence of CNTs composite catalysts with nickel metal clusters on the tips of CNTs (Ni-CNTs/MS catalysts) could significantly improve the catalyst stability in dry reforming reaction (at 650°C for 24h) and simultaneously inhibit reverse water–gas shift reaction compared to that of Ni/MS catalyst. After 24h time on stream, CO2 and CH4 conversions of Ni/MS catalyst were approximately decreased by 10%, while those of Ni-CNTs/MS catalyst were increased by 3%. This outstanding performance could be attributed to selective formation of carbon by-products as the tube-length extension of the existing CNTs. Accordingly, the active surface of Ni-CNTs/MS catalysts were remained constant throughout the period of dry reforming reaction.