Research Status and Prospect on Vanadium-Based Catalysts for NH3-SCR Denitration

Abstract

Selective catalytic reduction of NOx with NH3 is one of the most widely used technologies in denitration. Vanadium-based catalysts have been extensively studied for the deNOx process. V2O5/WO3(MoO3)TiO2 as a commercial catalyst has excellent catalytic activity in the medium temperature range. However, it has usually faced several problems in practical industrial applications, including narrow windows of operation temperatures, and the deactivation of catalysts. The modification of vanadium-based catalysts will be the focus in future research. In this paper, the chemical composition of vanadium-based catalysts, catalytic mechanism, the broadening of the temperature range, and the improvement of erosion resistance are reviewed. Furthermore, the effects of four major systems of copper, iron, cerium and manganese on the modification of vanadium-based catalysts are introduced and analyzed. It is worth noting that the addition of modified elements as promoters has greatly improved the catalytic performance. They can enhance the surface acidity, which leads to the increasing adsorption capacity of NH3. Surface defects and oxygen vacancies have also been increased, resulting in more active sites. Finally, the future development of vanadium-based catalysts for denitration is prospected. It is indicated that the main purpose for the research of vanadium-based modification will help to obtain safe, environmentally friendly, efficient, and economical catalysts.

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

“…XRF analysis of virgin monolith catalyst indicated that the loading of the two active metals (V and W) was 3.51% and 6.36% when expressed as oxides respectively (Table 1), which is typical of SCR catalysts for stationary applications [1,16]. SEM-EDS analysis of fresh monolith sample (not shown) indicated that vanadium, tungsten, and titanium were uniformly distributed, whereas the silica content was associated with the reinforcing glass fibers.…”

“…Selective catalytic reduction (SCR) of nitrogen oxides with ammonia is one of the most widely used technologies for reducing NOx from both stationary and mobile sources [1,2]. This technology and, in particular, its application to the exhaust of fossil fuel-fired power plants, is quite mature.…”

A study on the selective catalytic reduction of NOx by ammonia on sulphated iron-based catalysts

“…When the SO 4 2À content is constant, the addition of Fe 3+ to the catalyst will enhance its adsorption capacity of nitrogen oxides and NH 3 species at moderate and low temperatures. According to the references, 27,33,40,41 the mechanism of the SCR generally follows the Langmuir-Hinshelwood reaction path at moderate and low temperatures, and thus the Fe 3+ obviously adsorbed NH 3 and oxidized it to -NH 2 , which is the important intermediate species for the SCR reaction [42][43][44][45][46] and can react with the NO oxidation species (NO 2 À and NO 3 À ) to form the intermediate species, and then decompose to N 2 and H 2 O. Thus, the addition of Fe 3+ improved the redox ability, which affected the activity for the SCR at moderate and low temperatures.…”

Advanced Synthesis and Characterization of Vanadia/Titania Catalysts through a Molecular Approach

“…Although the VO x /TiO 2 catalytic system has been studied extensively in the past [21][22][23], the research effort to improve the efficiency of the SCR process over these catalysts is still of great topical interest, since the legislation becomes increasingly stricter, requiring emission control of NO x due to their very negative impact on the environment through to smog formation, acid rain formation, and depletion of the ozone layer. Moreover, their use for both stationary and mobile sources with different characteristics and requirements has kept the scientific research interest for these catalysts at a very high level, despite their long history [21,22,24]. The research effort is directed to the development of catalysts with high SCR efficiency, broad operation temperature window, superb durability, hydrothermal stability, and high resistance against SO 2 /alkali/heavy metals [21,22].…”

“…Moreover, their use for both stationary and mobile sources with different characteristics and requirements has kept the scientific research interest for these catalysts at a very high level, despite their long history [21,22,24]. The research effort is directed to the development of catalysts with high SCR efficiency, broad operation temperature window, superb durability, hydrothermal stability, and high resistance against SO 2 /alkali/heavy metals [21,22]. To achieve these goals as well as fully elucidate the SCR mechanism, the scientific community strives for structure-reactivity relationships by focusing on the study of the structural properties of the active sites [25][26][27][28][29], tries to find the optimum surface density of vanadium [30], synthesizes binary systems concerning either the active phase (VO x ) or the support (TiO 2 ) [18,[31][32][33][34], dopes the support [35], synthesizes metal vanadates [36], and tries to find the optimum thermal treatment of the catalysts [37] etc.…”