Review on SCR catalysts by focusing impacts of sulfur on SCR performance

Abstract

Marine diesel engines are extensively used for transportation and as well as for power generation purpose because of its high durability, thermal and fuel efficiency than the gasoline engines. But the marine diesel engine produced severe NO_x emissions that are currently well discussed issue needed to be solved due to its serious health and environmental problems. At the same time, because of increasing stringent regulations of NO_x emissions it is necessary for ships to meet the international maritime organization (IMO) Tier III regulations in NO_x emission control areas (ECA). It is enforced for the vessels that are constructed on and after the 1^st January 2016. Therefore, a demand for well functioning NO_x reduction technology is required. Currently SCR is the most dominant and mature technology used to reduce the NO_x with ammonia over the SCR catalyst.  SCR catalyst is the core part of SCR system; hence this review described the different types of catalysts and their behavior under different conditions. Furthermore, the deactivation of SCR catalyst occurs by different mechanisms; however, the most significant mechanism is sulfur poisoning. Reaction temperature and availability of ammonia is also significant parameter for sulfur poisoning. Therefore it is necessary to investigate how sulfur behaves with SCR catalysts. Even though many studies have been performed on sulphur poisoning of catalysts but still requires complete understanding.  This review covers the sulfur poisoning of vanadium and Cu-zeolites based SCR catalysts with mainly focus on Cu-zeolites because of its sulfur sensitivity.