Preparation of Activated Carbon-SnO2, TiO2, and WO3 Catalysts. Study by FT-IR Spectroscopy

Abstract

[EN] The chemical changes produced in the surface of activated carbon as a result of the process of preparation of activated carbon−metal oxide catalysts from SnCl2, TiO2, and Na2WO4 in water at pH 1.37 for SnCl2, 5.84 for TiO2, and 9.54 for Na2WO4 are studied. The samples were first prepared by the wet impregnation method in two successive steps of soaking at 80 °C for 5 h and oven-drying at 120 °C for 24 h. Then, they were analyzed by elemental analysis, FT-IR spectroscopy, and measurement of pH of the point of zero charge (pHpzc). The process yield was 149 wt % with SnCl2, 103 wt % with TiO2, and 106 wt % with Na2WO4. The impregnation of the carbon with the catalyst precursors in water entails the oxidation of chromene and pyrone type structures with formation of carboxylic acid groups. pHpzc is 10.50, activated carbon; <1.60, SnCl2; 9.35, TiO2; and 7.90, Na2WO4. The changes originating in the surface chemistry of AC with influence on the acid−base character are stronger by the order SnCl2 ≫ Na2WO4 > TiO2.