Catalytic Urea Decomposition at Low-temperature for NH3-SCR

Lai  Wei, University of Virginia

Lai Wei, Yu-Ren Chen, Carlos Weiler, William S. Epling

Department of Chemical Engineering, University of Virginia


Improving the low-temperature (≤ 200ºC) NOx conversion of selective catalytic reduction (SCR) is critical to further reducing the cold-start NOx emissions. One of the biggest challenges for urea-SCR at low temperature is promoting urea decomposition to generate sufficient ammonia, which is the reductant in the NH3-SCR reaction. In the present study, Commercial Cu/CHA monolith catalysts were investigated for catalytic urea decomposition at low-temperature. A flow reactor with a specially designed micro-spray urea injection system was developed. This system allows urea water solution droplets to be directly sprayed on the monolith, which was more closely simulating the conditions of the real world. Thermal gravimetric analysis (TGA) was also conducted for characterization. The results showed that the process of urea decomposes into NH3, including urea thermolysis and isocyanic acid (HNCO) hydrolysis, was greatly improved by Cu/CHA catalysts.

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