Improved SO2 Tolerance of Cu-SAPO-18 by Ce-Doping in the Selective Catalytic Reduction of NO with NH3

Shuai Han,Qi Gao,Qing Ye,Hongxing Dai

doi:10.3390/catal10070783

Abstract

The Ce-Cu-SAPO-18 catalysts were prepared using the ion exchange method. The impact of sulfur dioxide on catalytic performance of Ce-Cu-SAPO-18 for the selective catalytic reduction (SCR) of NO with NH3 was examined. Detailed characterization of the fresh and sulfur-poisoning Cu-SAPO-18 and Ce-Cu-SAPO-18 samples was conducted. XRD and BET results show that SO2 treatment of the Ce-doped Cu-SAPO-18 (Ce-Cu-SAPO-18-S) sample did not induce a remarkable change in structure, as compared with that of the fresh counterpart. According to in situ DRIFT, H2-TPR, SEM, and EDS results, it is found that the sulfation species attached preferentially to the cerium species, rather than the isolated Cu2+ species. In particular, the TG/DSC results confirm that the sulfate species on the Ce-Cu-SAPO-18-S sample was easier to decompose than that on the Cu-SAPO-18-S sample. The catalytic active sites of Ce-Cu-SAPO-18 were less influenced after SO2 treatment, as demonstrated by the TPR and XPS results. All of the above results show that the Ce-Cu-SAPO-18 sample exhibited better sulfur-resistant performance than the Cu-SAPO-18 sample.

Highlights

IntroductionNOx in diesel exhaust is harmful to human health. Selective catalytic reduction of NOx with NH3 (NH3 -selective catalytic reduction (SCR)) is a commonly used method in controlling NOx emissions [1,2,3,4], and the key issue is the availability of high-performance catalysts
Among air pollutants, NOx in diesel exhaust is harmful to human health
It can be seen that the sulfur resistance of Ce-Cu-SAPO-18 was better than that of Cu-SAPO-18

Summary

Introduction

NOx in diesel exhaust is harmful to human health. Selective catalytic reduction of NOx with NH3 (NH3 -SCR) is a commonly used method in controlling NOx emissions [1,2,3,4], and the key issue is the availability of high-performance catalysts. The Cu-exchanged zeolite (e.g., ZSM-5 [5], SSZ-13 [6], SAPO-34 [7], and SAPO-18 [8,9]) catalysts have been studied intensively and extensively, with the emphasis being putting on the wide temperature ranges with high NOx conversions. The high-temperature hydrothermal conditions (>650 ◦ C) can destroy the zeolitic framework structures and result in catalyst deactivation [10,11]. The catalysts were sulfated to form the sulfate species [12], resulting in a decrease in SCR activity [13]. The poor resistance to SO2 poisoning of the zeolite-based catalysts still remain a primary problem in commercial applications of the diesel after-treatment systems [14,15]

Methods

Results

Conclusion