State-of-Art Review of NO Reduction Technologies by CO, CH4 and H2

Abstract

Removal of nitrogen oxides during coal combustion is a subject of great concerns. The present study reviews the state-of-art catalysts for NO reduction by CO, CH4, and H2. In terms of NO reduction by CO and CH4, it focuses on the preparation methodologies and catalytic properties of noble metal catalysts and non-noble metal catalysts. In the technology of NO removal by H2, the NO removal performance of the noble metal catalyst is mainly discussed from the traditional carrier and the new carrier, such as Al2O3, ZSM-5, OMS-2, MOFs, perovskite oxide, etc. By adopting new preparation methodologies and introducing the secondary metal component, the catalysts supported by a traditional carrier could achieve a much higher activity. New carrier for catalyst design seems a promising aspect for improving the catalyst performance, i.e., catalytic activity and stability, in future. Moreover, mechanisms of catalytic NO reduction by these three agents are discussed in-depth. Through the critical review, it is found that the adsorption of NOx and the decomposition of NO are key steps in NO removal by CO, and the activation of the C-H bond in CH4 and H-H bonds in H2 serves as a rate determining step of the reaction of NO removal by CH4 and H2, respectively.

First-Principles Study of NO Reduction by CO on Cu2O(110) and Pd1/Cu2O(110) Surfaces

“…Currently, selective catalytic reduction (SCR) is considered as one of the most effective methods for NO elimination. The commonly used reducing agents are CO, H 2 , NH 3 , and C x H y . − Among them, SCR of NO with CO as reducing agent can simultaneously convert two pollutants (CO and NO) into harmless N 2 and acceptable CO 2 , which has attracted wide attention. − Platinum-based catalysts (Pt, Pd, and Rh) are the active components of three-way catalysts (TWCs) in automotive exhaust emission control systems. − However, the scarcity of resources and high prices limit their practical application prospects.…”

Single Ti3+ Ion Catalyzes NO Reduction on Stoichiometric Titanium Oxide Cluster Anions (TiO2)n– (n = 1–11)

“…We speculate that this catalytically reactive single Ti 3+ ion can exist on larger (TiO 2 ) n − (n > 11) clusters. This finding provides the much-needed and atomically precise insights into the surface chemistry of titanium oxide particles from the viewpoint of cluster science and gives an in-depth understanding of the atmospheric chemistry of NO reduction by CO, 29,30 an important subject in pollution abatement due to their negative impacts on the environment and human health.…”

Noble Metal Nanoparticles Decorated Boron Nitride Nanotubes for Efficient and Selective Low-Temperature Catalytic Reduction of Nitric Oxide with Carbon Monoxide

“…In oxygen-rich conditions, CO is preferentially oxidized to CO 2 , resulting in inhibiting the NO + CO reaction and reducing NO removal efficiency. 5,6 The reaction temperature also plays a decisive role in the N 2 selectivity. In general, at a low reaction temperature, N 2 O, another notorious toxic gas, is a dominant product.…”

“…As a result of the toxic nature of carbon monoxide (CO) and nitrogen oxides (NO x , mainly NO), direct NO reduction by CO (2CO + 2NO → 2CO 2 + N 2 ) over heterogeneous catalysts has been investigated for several decades. − However, there were two major challenges that were raised for this reaction to be successfully applied to industrial applications: (1) NO reduction and N 2 selectivity under oxygen-enriched conditions and (2) catalytic performance at a lower reaction temperature. In oxygen-rich conditions, CO is preferentially oxidized to CO 2 , resulting in inhibiting the NO + CO reaction and reducing NO removal efficiency. , The reaction temperature also plays a decisive role in the N 2 selectivity. In general, at a low reaction temperature, N 2 O, another notorious toxic gas, is a dominant product. − Hence, an efficient and robust deNO x catalyst suitable for catalyzing NO + CO reactions in oxygen-rich conditions and at low reaction temperatures is essentially sought.…”