Exploring halloysite nanotubes as catalyst support for methane combustion: Influence of support pretreatment

Abstract

Catalytic combustion of methane is considered an environmentally friendly route for energy generation owing to the high H/C ratio of methane and low CO2 emissions compared to other hydrocarbons fuels. The utilization of heterogeneous catalysts permits combustion at lower temperatures compared with thermal combustion. Herein, we developed new catalysts of palladium-supported halloysite nanotubes (HNTs) for methane combustion. This was performed via chemical modification of HNTs using four different species i.e. H2SO4 (HNTs-H2SO4), NaOH (HNTs-NaOH), sodium dodecyl sulfate (HNTs-SDS), and cetyltrimethylammonium bromide (HNTs-CTAB). After chemical modification, Pd was deposited on the pretreated HNTs and the impact of chemical treatment on the morphology, crystal structure, textural properties, and methane oxidation activity was studied. All catalysts based on chemically modified HNTs exhibited enhanced catalytic performance towards methane combustion compared to Pd-supported on pristine HNTs, in particular, Pd/alkali-treated HNTs (Pd/HNTs-NaOH) revealed the highest catalytic activity towards methane combustion with the temperature of complete conversion (T100) equals 385 °C and activation energy of 79.15 kJ mol−1. Furthermore, the same sample displayed enhanced stability compared to other counterparts. This was assigned to the confinement of Pd nanoparticles at the inner surface which enhances the catalyst-support interaction, increases the number of surface active sites, and enhances the resistance to sintering at high temperatures.