Plausibility of potassium ion-exchanged ZSM-5 as soot combustion catalysts

Chenxi Lu,Lei Zheng,Qian Li,Zhaoliang Zhang,Ying Xin,Taizheng Liu,Qiaolan Shi

doi:10.1038/s41598-017-03504-3

Abstract

Potassium (K) ion-exchanged ZSM-5 zeolites were investigated for catalytic soot combustion. X-ray absorption fine-structure (XAFS), Raman, in situ IR and NH3-temperature programmed desorption (NH3-TPD) confirmed the location of K+ at the ion-exchanged sites. Temperature-programmed oxidation (TPO) reactions showed that K-ZSM-5 decreased ignition tempeatures of soot combustion and increased selectivity to CO2. The improved activity for soot combustion by increasing K+-exchanged amounts via decreasing the Si/Al ratio reinforced the K+ ions participating in soot combustion. 18O2 isotopic isothermal reactions suggested the activation of gaseous oxygen by the K+ ions. This demonstrated a new appliction of alkali metal exchanged zeolites and the strategy for enhancement of catalytic soot combustion activity.

Highlights

Soot particulates are one of the main pollutants emitted from diesel engines, which represents a significant threat to environment and human health
Na-ZSM-5 zeolites were hydrothermally synthesized with Si/Al ratios of 100 (Na-ZSM-5-100) and 25 (Na-ZSM-5-25)[16], followed by ion-exchanges of H+ and K+, which results in H-ZSM5-100 and K-ZSM-5-100 (25) samples, respectively
K-ZSM-5 zeolites were prepared by ion-exchange and evaluated for soot combustion

Summary

Introduction

Soot particulates are one of the main pollutants emitted from diesel engines, which represents a significant threat to environment and human health. Zhao’s group has reported that gold nanoparticles supported on three-dimensionally ordered macroporous oxides exhibit outstanding activity[9]. Kimura et al reported that K2CO3 supported on aluminosilicate zeolite exhibited excellent catalytic activity[24, 25]. No one has reported ion-exchanged K-ZSM-5 as catalysts for soot combustion. K-ZSM-5 was first reported to increase both activity and selectivity to CO2 for soot combustion. This was confirmed by the fact that increasing K+-exchanged amounts via decreasing the Si/Al ratio led to the improved activity, which was attributed to the activation of gaseous oxygen by K+ at the ion-exchanged sites

Methods

Results

Discussion

Conclusion