Investigation of vanadium sublimation from SCR catalysts 2015-24-2503

The aim of the study is to evaluate the possible vanadium emissions from different commercially available vanadium-based SCR monoliths. The vanadium sublimation was studied at laboratory scale using a monolith sample (16 mm diameter × 19 mm long). Vanadia vapors were disposed on an alumina bed placed downstream the catalyst sample, in the hot zone of a furnace. Experiments were carried out with a space velocity of 42 000 h⁻¹. The reactive gas flow was composed of 5%O₂, 5%H₂O, 500ppm NO and 500ppm NH₃. Catalyst samples and alumina bed were exposed to this reactive gas flow during 10 hours at 500°C, 600°C, 650°C, 675°C, 700°C and 750°C, successively. After each test, alumina samples were mineralized from HNO₃, HF and HCl mixture. The digests were then diluted with high purity water prior, to ICP-MS analysis.

The results revealed that, for full body type catalysts, sublimation of vanadium increases in a significant way from an exposure to the reactive gas flow at 675°C. From 650°C to 675°C the amount of vanadium emitted increases by a factor from 3 to 5. On a SCR monolith composed of a catalytic coated substrate a temperature higher than 700°C is necessary to obtain a significant increase of the amount of vanadium sublimated.