NO x control via H 2-selective catalytic reduction (H 2-SCR) technology for stationary and mobile applications

Abstract

This review paper provides an overview of the use of hydrogen (H 2) gas towards the selective catalytic reduction of nitrogen oxides (NO x) under strongly oxidizing conditions found in many industrial flue gas streams and in the exhaust emissions of diesel-powered vehicles. Patenting activities in the last 15 years are discussed. The advantages in using the H 2-SCR of NO x control technology especially at low-temperatures as to the current NH 3-SCR technology are also discussed. Regarding the stationary NO x control applications, Pd-based catalysts exhibit NO x conversion and N 2-selectivity values in the 80-95% range, depending on the chemical promoter and support composition used have been reported. On the other hand, Pt-based catalysts present lower NO x conversion and N 2-selectivity values (<90%) especially when 10-20 vol% water is present in the flue gas stream. For mobile applications, different formulations of Pd-based catalysts (support and promoter chemical composition) have been reported with NO x conversions higher than 85%. The issue of hydrogen supply has been tackled through the development of on-board hydrogen generation technologies, such as plasma reforming and partial oxidation of diesel fuel. © 2012 Bentham Science Publishers.