Catalysts for the selective catalytic reduction of NO_x with NH₃ at low temperature

Abstract

ARTICLE This journal isSelective catalytic reduction of NOx with NH3 (NH3-SCR) at low temperature is a major challenge in environmental catalysis. In recent years, great efforts have been applied to the development of low-temperature SCR catalysts for both stationary sources and diesel engines. Mn-based catalysts have attracted great attentions due to their excellent low-temperature activity. However, vulnerability to SO2 and H2O poisoning and preference for N2O formation make these catalysts still far away from industrial application. V2O5 loaded on carbon materials have shown both high SCR activity and SO2 tolerance at low-temperature. This type of catalyst is very promising for the applications in low-temperature SCR for stationary sources. Recently, Cu containing small pore zeolites, such as Cu-SSZ-13 and Cu-SAPO-34 with CHA structure and Cu-SSZ-39 and Cu-SAPO-18 with AEI structure, were shown to have very high activity at low temperature and excellent hydrothermal stability at high temperature and thus received much attention for the applications on diesel vehicles. In this review, we will focus on the recent studies of low-temperature NH3-SCR catalysts. In addition, the future directions of low-temperature SCR development will also be discussed. Challenges Inhibition of H2Oa.

A review of carbon-based and non-carbon-based catalyst supports for the selective catalytic reduction of nitric oxide

“…High Ce 3+ ion concentration contributed to the high amount of chemisorbed oxygen, which increased the redox cycle and enhanced the reducibility of hydrogen. This is because the Ce 3+ ions will assist the migration of O 2 from gas phase to the surface of the catalyst [8,23]. Afterwards, Wei et al [24] explained that NO x removal using FeCu/zeolite catalyst followed both Eley–Rideal and Langmuir–Hinshelwood mechanisms.…”

“…However, some problems are still evident with the use of this catalyst, e.g., the vanadium species is highly toxic to humans and the environment, and excessive dust pollution will usually result from the upstream flue gas, which can cause the deactivation of the catalyst. In addition, the catalyst also has a limited temperature window (300–400 °C) and poor thermal stability [7–8]. Hence, there is an urgent need to find other catalysts that can overcome these drawbacks and also have high resistance to water (H 2 O) and oxidation of SO 2 to SO 3 , so that high activity and selectivity, high thermal stability, and a temperature lower than 300 °C can be achieved, thus increasing the lifetime of the catalyst.…”

Sulfur and Water Resistance of Mn-Based Catalysts for Low-Temperature Selective Catalytic Reduction of NOx: A Review

“…As well known, the commercial catalysts (V 2 O 5 -WO 3 (or MoO 3 )/TiO 2 ) used in thermal power plant are in the monolithic form because the honeycomb monoliths are suitable for a high gas flow rate, reduce pressure drop problems, exhibit high tolerance to dust and attrition, and are easy to regenerate [103][104][105][106]. Recently, metal foam and wire mesh as novel monolithic support for Mn-based and other vanadium-free SCR catalysts are drawing an increasing amount of attention due to their high porosity, stability, thermal conductivity, and mass transfer ability [107,108].…”

Upgrading V2O5-WO3/TiO2 deNOx Catalyst with TiO2-SiO2 Support Prepared from Ti-Bearing Blast Furnace Slag

“…Among them, NH 3 -SCR is the most common technology for deep removal of NO x from various kinds of flue gas. In this process, the NO x in flue gas selectively reacts with gaseous ammonia over the catalyst to produce nitrogen and water without generating any secondary pollutants [5][6][7]. Currently, the global demand for SCR systems is increasing rapidly and China has the biggest market.…”

“…% silica introduced in catalyst molding [10,12]. Many reports in the literature [5,[16][17][18] have reported that TiO 2 -SiO 2 support can improve catalytic activity and SO 2 durability. Such superior low-temperature SCR activity was mainly attributed to the presence of polymeric vanadate species and high redox properties besides high surface area.…”