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Deactivation of Cu-SAPO-34 by urea-related deposits at low temperatures and the regeneration
Yue Ma1, Xiaodong Wu2, Junyu Zhang3
1The Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
Abstract:
Selective catalytic reduction (SCR) with urea catalyzed by Cu-SAPO-34 is an effective method to eliminate NOx from diesel exhaust. However, urea-related deposits may form during cold-start and urban driving due to low exhaust temperatures. The activity of Cu-SAPO-34 at 175°C is significantly degraded by urea exposure, and 300°C is required for regeneration. Through in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature-programmed hydrolysis studies, the dominant stable deposit at 175°C is identified as biuret, which can be eliminated at 300°C. The urea-derived deactivation and regeneration mechanisms of Cu-SAPO-34 were compared with those of anatase-supported catalysts.
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