Selective Catalytic Reduction Study with Alternative Reducing Agents

Abstract

Abstract

Diesel engine technology has been driven by increasingly stringent environmental legislation. To comply with these laws, emissions-control systems are being rapidly improved. Within this context, development of exhaust gas after-treatment systems undertakes a significant role. Among the techniques used is selective catalytic reduction (SCR), which converts nitrogen oxides (NO_x) into diatomic nitrogen (N₂) and water (H₂O). A reducing agent containing ammonia (NH₃) is added to the flow and absorbed by a catalyst. Different reducing agents are currently used, principally anhydrous NH₃, aqueous NH₃, and urea. This study analyzed behavior of different urea- and formamide-based agents to SCR. Results are compared to those obtained with Adblue. In relation to the SCR system as well as to NO_x reduction, we concluded that urea-based mixtures are the most efficient, although they present higher values of NH₃ slip. Formamide-based mixtures are significantly less efficient than urea-based mixtures, but the NH₃ slip levels produced by these mixtures are virtually none. A challenge is to find new reducing agent for SCR applications, considering that the deposits of urea formed during certain work conditions are a significant problem.