Catalytic combustion of soot particulates over rare-earth substituted Ln2Sn2O7 pyrochlores (Ln=La, Nd and Sm)

Zhongpeng Wang; Hongjian Zhu; Lijie Ai; Xuhui Liu; Min Lv; Liguo Wang; Zhenmin Ma; Zhaoliang Zhang

doi:10.1016/j.jcis.2016.06.010

Catalytic combustion of soot particulates over rare-earth substituted Ln2Sn2O7 pyrochlores (Ln=La, Nd and Sm)

J Colloid Interface Sci. 2016 Sep 15:478:209-16. doi: 10.1016/j.jcis.2016.06.010. Epub 2016 Jun 2.

Authors

Zhongpeng Wang¹, Hongjian Zhu², Lijie Ai², Xuhui Liu², Min Lv², Liguo Wang³, Zhenmin Ma², Zhaoliang Zhang⁴

Affiliations

¹ School of Resources and Environment, University of Jinan, 106 Jiwei Road, Jinan 250022, PR China. Electronic address: chm_wangzp@ujn.edu.cn.
² School of Resources and Environment, University of Jinan, 106 Jiwei Road, Jinan 250022, PR China.
³ School of Resources and Environment, University of Jinan, 106 Jiwei Road, Jinan 250022, PR China. Electronic address: chm_wanglg@ujn.edu.cn.
⁴ College of Chemistry and Chemical Engineering, University of Jinan, 106 Jiwei Road, Jinan 250022, PR China.

PMID: 27295323
DOI: 10.1016/j.jcis.2016.06.010

Abstract

Catalytic combustion is one of the most promising methods for diesel soot removal. Ln2Sn2O7 pyrochlores substituted with different rare-earth (RE) elements (Ln=La, Nd and Sm) were prepared through co-precipitation method for catalytic combustion of soot particulates. The structural, textural and redox properties, together with the oxygen vacancy of the catalysts were investigated systematically. Their catalytic activities were evaluated by both temperature-programmed oxidation and isothermal reaction techniques. With the increasing in RE ionic radius (r), the SnO bond strength in Ln2Sn2O7 pyrochlores evaluated from the stretching IR band was decreased, resulting in the improved reducibility and enhanced oxygen vacancies of catalysts. The increase of oxygen vacancy concentration was further confirmed by photoluminescence (PL) investigations wherein upon excitation with UV radiation, the pyrochlores nanoparticles exhibited strong and sharp transition at 408nm attributed to oxygen vacancies. Catalytic combustion and isothermal reactions revealed that the ignition activity (ignition temperature, T5) and the intrinsic activity (turnover frequency, TOF) were shown to depend correlatedly on redox properties and oxygen vacancy concentrations, both of which were influenced by the substitution of different RE elements. Among the pyrochlore oxides, the as-synthesized La2Sn2O7 sample displayed relatively the highest ignition activity and the largest intrinsic activity with TOF of 2.33×10(-3)s(-1).

Keywords: Catalytic activity; Oxygen vacancy; Pyrochlore; Soot combustion; Turnover frequency.