Adsorption microcalorimetric studies of ammonia, toluene, and water over titania, titania-silica, titania-alumina, and titania-ferrica

We used adsorption microcalorimetry of ammonia, toluene and water to probe their binding strength distribution and compare it with the acidic profile of the oxides.; Although, titania presented the highest acid strength (140 kJ/mol), titania-silica showed a higher average surface acidity (116.6 kJ/mol). Titania-silica and titania-ferrica displayed similar initial acid strength values (135 kJ/mol). However, titania-silica showed a wider surface coverage of high acidity (60 mumol/g) with an average acid strength near 135 kJ/mol. Titania-silica adsorbed more toluene than any other oxide (96 mumol/g), but titania adsorbed more water (195 mumol/g) than titania-silica (177 mumol/g). However, toluene was more strongly held to the surface of titania (70.3 kJ/mol) and water was more strongly held to the surface of titania-silica (99.5 kJ/mol).; Experiments over water-saturated titania-silica were also performed. Only physical adsorption was observed suggesting the displacement of adsorbed toluene by water molecules.