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

Several metal oxides were modified with gamma -anilinopropyltrimethoxysilan e (AnPS). Variations in the physicochemical properties with the modificatio n were investigated in detail. The adsorptivity of 12-tungstophosphate anio n (PW12) was shown to be greatly improved in the carriers such as SiO2, TiO 2, 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 isoe lectric point. With TiO2-carrier, quantitative studies on the adsorptivity were carried out further, and the interaction modes of PW12 on the AnPS-mod ified 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 a scribed to the anilino group deformed considerably and the N1s-peak in XPS shifted along with the PW12-adsorption. From the findings it was strongly s uggested that PW12 was effectively fixed through an acid-base interaction o n the AnPS-TiO2. Catalytic activity of PW12 fixed on AnPS-TiO2 for 2-propan ol dehydration as a test reaction were examined; in the pretreatment at 300 degreesC the activity was limited to a low level but after the treatment a t 450 degreesC it increased in proportion to the PW12-loading on the AnPS-T iO2 surfaces. Thus, it was inferred that PW12 was quite regularly dispersed over the modified surface. In conclusion, it is suggested that the modific ation technique is applicable to the preparation of a metal oxide-supported heteropolyacid catalyst.