Chemical modification of metal oxide carrier's surfaces with a silane coupling agent and an application of the method to catalyst preparation

Abstract Several metal oxides were modified with γ-anilinopropyltrimethoxysilane (AnPS). Variations in the physicochemical properties with the modification were investigated in detail. The adsorptivity of 12-tungstophosphate anion (PW12) was shown to be greatly improved in the carriers such as SiO2, TiO2, and Al2O3, which are porous and have a high surface area, but it was not increased in SnO2 and MgO, which have a small surface area and a high isoelectric point. With TiO2-carrier, quantitative studies on the adsorptivity were carried out further, and the interaction modes of PW12 on the AnPS-modified surfaces were discussed based on FT-IR and XPS analyses. The isotherm attained quite steeply to a monomolecular layer of PW12. The FT-IR bands ascribed to the anilino group deformed considerably and the N1s-peak in XPS shifted along with the PW12-adsorption. From the findings it was strongly suggested that PW12 was effectively fixed through an acid–base interaction on the AnPS-TiO2. Catalytic activity of PW12 fixed on AnPS-TiO2 for 2-propanol dehydration as a test reaction were examined; in the pretreatment at 300°C the activity was limited to a low level but after the treatment at 450°C it increased in proportion to the PW12-loading on the AnPS-TiO2 surfaces. Thus, it was inferred that PW12 was quite regularly dispersed over the modified surface. In conclusion, it is suggested that the modification technique is applicable to the preparation of a metal oxide–supported heteropolyacid catalyst. Keywords: MODIFICATIONMETAL OXIDESSILANE COUPLING AGENTCATALYST PREPARATIONHETEROPOLYACID