Influence of Sulfur-Containing Sodium Salt Poisoned V2O5–WO3/TiO2 Catalysts on SO2–SO3 Conversion and NO Removal

Abstract

A series of poisoned catalysts with various forms and contents of sodium salts (Na2SO4 and Na2S2O7) were prepared using the wet impregnation method. The influence of sodium salts poisoned catalysts on SO2 oxidation and NO reduction was investigated. The chemical and physical features of the catalysts were characterized via NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FT-IR). The results showed that sodium salts poisoned catalysts led to a decrease in the denitration efficiency. The 3.6% Na2SO4 poisoned catalyst was the most severely deactivated with denitration efficiency of only 50.97% at 350 °C. The introduction of SO42− and S2O72− created new Brønsted acid sites, which facilitated the adsorption of NH3 and NO reduction. The sodium salts poisoned catalysts significantly increased the conversion of SO2–SO3. 3.6%Na2S2O7 poisoned catalyst had the strongest effect on SO2 oxidation and the catalyst achieved a maximum SO2–SO3-conversion of 1.44% at 410 °C. Characterization results showed sodium salts poisoned catalysts consumed the active ingredient and lowered the V4+/V5+ ratio, which suppressed catalytic performance. However, they increased the content of chemically adsorbed oxygen and the strength of V5+=O bonds, which promoted SO2 oxidation.

Catalyst Deactivation, Poisoning and Regeneration

“…The complexity of catalyst poisoning obviously increases along with the increasing use of biomass/waste-derived/residual feedstocks [2,3] and with requirements for cleaner and novel sustainable processes, such as those implementing a catalytic assisted chemical looping approach [4,5].This Special Issue provides insight for several specific scientific and technical aspects of catalyst poisoning and deactivation, proposing more tolerant catalyst formulations and exploring possible regeneration strategies. In particular, 14 research articles focus on heterogeneous catalysts by investigating thermal [6-8], physical [9,10] and chemical [11][12][13][14][15][16][17][18][19] deactivation phenomena, and also exploring less conventional poisons related to the increasing use of bio-fuels [17]. Some regeneration strategies [11,16], together with solutions to prevent or limit deactivation phenomena [7,9,11,16], are also discussed.…”

“…In addition, alkali and alkali earth metals are often responsible for the severe deactivation of SCR catalysts, especially when treating exhaust from the combustion of renewable fuels. Indeed, those elements can potentially come from bio-fuels or urea solutions in diesel engines [17] or even from fossil fuels in thermal power plants burning carbon [18]. Accordingly, in [18] the authors investigate the impact of the deposition of sulphur containing sodium salts onto a V 2 O 5 -WO 3 /TiO 2 SCR catalyst with special regards to the NO removal rate as well as to the oxidation of SO 2 to SO 3 .…”

“…Indeed, those elements can potentially come from bio-fuels or urea solutions in diesel engines [17] or even from fossil fuels in thermal power plants burning carbon [18]. Accordingly, in [18] the authors investigate the impact of the deposition of sulphur containing sodium salts onto a V 2 O 5 -WO 3 /TiO 2 SCR catalyst with special regards to the NO removal rate as well as to the oxidation of SO 2 to SO 3 . Moreover, as reported in [17], relatively high contents of sodium affect the hydrothermal stability of a Cu/SSZ-13 zeolite catalyst for the NH 3 -SCR of a diesel exhaust.…”