Correlation between microstructure and performance of Pt/TiO2 catalysts for formaldehyde catalytic oxidation at ambient temperature:: Effects of hydrogen pretreatment

As long-term exposure to indoor air containing even a few ppm of formaldehyde may cause adverse effects on human health, catalytic oxidation is one of the most important and promising processes for the removal of formaldehyde. The catalyst adsorption and transport properties greatly affect its performance, which can be influenced by hydrogen pretreatment. For catalysts pretreated at 450 degrees C, the pore size distribution profile demonstrates the narrowest pore size distribution. Except for the catalyst pretreated at 900 degrees C, all catalysts exhibit a type H2 isotherm according to the IUPAC classification, characteristic of mesoporous materials. On the basis of calculations from the Mahnke and Mogel model, increasing the pretreatment temperature from 300 to 450 degrees C increases the fractal dimension d(f) from 2.23 to 2.39. However, a further increase from 700 to 900 degrees C causes the surface fractal dimension d(f) to decrease from 2.07 to 2.02, respectively. The volcano type of fractal dimension d(f) is also confirmed by the results calculated from Neimark's model, which is coincident with the performance of the catalysts pretreated at different temperatures.