Sulfur-containing deposits form on a monolithic V2O5-WO3/TiO2 (VWT) catalyst during SCR-DeNOx with NH3 at 473 and 523 K and pressures up to 500 kPa in the presence of SO2 with sulfate contents of 1.7 to 13.0 wt%. Using thermogravimetric analysis and diffuse reflectance infrared spectroscopy, these deposits are determined to be mainly NH4HSO4 for SCR temperatures > 523 K. At lower temperatures, (NH4)2SO4 is formed. The thermal stability of NH4HSO4 supported on different transition metal oxides including V2O5, WO3, TiO2, MoO3, and Al2O3 varies with decomposition temperatures from 620 to 820 K. Using DFT calculations, it is shown that the thermal stability of supported NH4HSO4 is mainly determined by hydrogen bonding of the HSO4 − anions with the metal oxide surface. Increasing electronegativity of the metal atoms of the support oxide leads to weakening of the S-O bonds in the HSO4 − anions and to lower decomposition temperatures of the supported NH4HSO4.
All Science Journal Classification (ASJC) codes
- Automotive Engineering
- Management, Monitoring, Policy and Law
- Health, Toxicology and Mutagenesis