Adsorption of methanol on Si(1 0 0)/SiO2 and mesoporous SBA-15

Abstract

Adsorption of methanol on Si(1 0 0)/SiO2 substrate and mesoporous SBA-15 has been studied by using Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Contact angle technique is employed to study the adsorption kinetics of methanol on Si(1 0 0)/SiO2 and thermal stability of adlayer. Thermogravimetric (TGA) technique is used to understand the thermal behavior of methanol layer on SBA-15. Adsorption kinetics fit fairly well with Langmuir isotherms giving adsorption rate constant, ka = 0.0021M−1 s−1. FTIR results show formation of methoxy silicon (SiOCH3), silicon polyhydride (SiH2), carboxylate, molecular water and hydroxyl groups on Si(1 0 0)/SiO2 surface and only methoxy silicon on SBA-15. XPS results confirm methanol adsorption and support FTIR results. The methanol adlayers are found to be thermally stable up to a temperature of ∼262 ◦C on both Si(1 0 0)/SiO2 and SBA-15 and decompose between 262 and 450 ◦C.