Abstract
The improvement of hydrocarbon resistance is a challenge for developing HBEA zeolite-based catalysts for NH3-SCR of NOx from diesel engine exhausts. HBEA zeolite was deactivated rapidly by propene during the NH3 selective catalytic reduction of NOx. The carbonaceous deposits formed by incomplete combustion of propene were responsible for the deactivation. The propene poisoning resistance of HBEA catalyst could be improved by doping CeO2. The Ce x/HBEA catalyst was prepared by impregnation method. The Ce48/HBEA catalyst showed the highest NOx conversion among the prepared catalysts. In the presence of propene, NOx conversion of Ce48/HBEA was above 92% in the temperature range of 300–450°C with GHSV of 150,000h−1. The N2 selectivity was above 96% between 175°C and 500°C for the Ce48/HBEA catalyst. Moreover, HBEA coated by CeO2 core-shell structure was formed in the Ce48/HBEA catalyst. Propene was mainly oxidized to CO2 by O2 over the CeO2 shell, which protected HBEA from propene poisoning. NH4+ and COO− as intermediates during NH3-SCR of NOx in the presence of C3H6 was observed on the DRIFTS spectra. These results show that the Ce48/HBEA catalyst with the core-shell structure is a potential candidate to control NOx emissions from diesel engine.
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