Improved Low-Temperature Activity of V2O5-WO3/TiO2 for Denitration Using Different Vanadium Precursors

Abstract

This work tested two V 2 O 5 -WO 3 /TiO 2 catalysts with different vanadium precursors for selective catalytic reduction (SCR) of flue gas NO using NH 3 at 150-450˝C. While catalyst A was prepared using ammonium metavanadate (NH 4 VO 3 ) through incipient impregnation, catalyst B was made according to the solvothermal method using vanadyl acetylacetonate (VO(acac) 2 ) as the vanadium precursor. The catalytic evaluation for denitration was in a laboratory fixed bed reactor using simulated flue gas under conditions of a gas hourly space velocity (GHSV) of 40,000 h´1 and an NH 3 /NO molar ratio of 0.8. Without SO 2 and water vapor in the flue gas at 200˝C, the realized NO conversion was 56% for catalyst A but 80% for B. The presence of 350 ppm SO 2 and 10 vol. % water vapor in the flue gas slightly reduced the NO conversion over catalyst B, and its activity was stable in a 108-h continuous test at temperatures varying from 450˝C to 220˝C. Via fourier transformation infrared spectroscopy (FT-IR) and thermogravimetric (TG) analysis, it was shown that over catalyst B a dynamic balance between the formation and decomposition of ammonium sulfite or sulfate is built possibly at temperatures as low as 220˝C. For this catalyst there was a higher surface atomic concentration of vanadium and a higher ratio of V 4+ /(V 4+ + V 5+ ), while the NH 3 adsorption test revealed more acidic sites on catalyst B. The study discloses a potentially new approach to prepare a V 2 O 5 -WO 3 /TiO 2 catalyst with good performance for SCR of flue gas NO at 220-300˝C.

A Case Study for the Deactivation and Regeneration of a V2O5-WO3/TiO2 Catalyst in a Tail-End SCR Unit of a Municipal Waste Incineration Plant

“…This conclusion explains the reason why WW regeneration is more effective than thermal regeneration. In fact, the thermal treatment could only promote ammonium sulfate decomposition, which largely occurs at T < 400 • C, as also reported by Gan et al [26], whereas WW solubilized also the other more stable sulfates and easily removed ash debris poorly attached to the monolith walls. This result is roughly in agreement with data reported in Table 4 showing that only 1/3 of the total sulfates were removed through thermal regeneration, whereas with the washing treatment it was possible to remove the remaining fraction.…”

A Comparative Study of the NH3-SCR Reactions over an Original and Sb-Modified V2O5–WO3/TiO2 Catalyst at Low Temperatures

“…Specifically, the ammonium sulfate was chemisorbed on the catalyst surface, forming a bidentate SO4 2− and interacting with TiO2, thereby creating the mutual effect [35]. For the V 2p spectra, V with a binding energy of 515.4-516.0 eV was attributed to V 4+ , and V at 516.6-517 eV was attributed to V 5+ [25]. The ratio of V 4+ /V 5+ was a crucial factor affecting the denitrification activity of the catalyst.…”

Conventional and New Materials for Selective Catalytic Reduction (SCR) of NOx

“…Gan et al. reported that low‐temperature deNO x activity of V 2 O 5 ‐WO 3 /TiO 2 was improved in the presence of catalyst B instead of catalyst A. Catalyst A was prepared using NH 4 VO 3 as a precursor in a conventional aqueous impregnation method whereas catalyst B was prepared using VO(acac) 2 (acac=acetylacetonate, C 5 H 7 O 2 ) as a precursor in a solvothermal method . The vanadium in VO(acac) 2 is five‐coordinate with a square‐based pyramidal geometry and vanadium is in the oxidation state +4.…”