Low-temperature CO oxidation on Ag/ZSM-5 catalysts: Influence of Si/Al ratio and redox pretreatments on formation of silver active sites

E. Kolobova, A. Pestryakov, G. Mamontov, Yu Kotolevich, N. Bogdanchikova, M. Farias, A. Vosmerikov, L. Vosmerikova, V. Cortes Corberan

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Abstract

Silver catalysts supported on ZSM-5 (Si/Al = 30, 50 and 80) were investigated for low-temperature CO oxidation to study the nature of the silver active sites and their formation under the influence of the support chemical composition and redox pretreatments. The catalysts were characterized by HRTEM, FTIR, XPS, diffuse reflectance UV–Vis spectroscopy, NH3 thermodesorption (NH3 TPD) and temperature-programmed reduction (H2 TPR). The chemical composition (Si/Al ratio) of the ZSM-5 zeolite support significantly affects catalytic properties of Ag/ZSM-5 samples: the lower the Broensted acidity of the zeolite support, the higher the activity of the catalysts. Interestingly, while oxidizing pretreatment of catalysts led to a significantly better performance than reducing pretreatments, the consecutive reducing treatment of the preoxidized samples significantly promoted the catalytic activity for low-temperature CO oxidation. Thus, Ag/ZMS-5 catalyst with Si/Al = 80, pretreated consecutively in oxidizing and reducing conditions, showed the highest activity, reaching 90% CO conversion at just 40 °C. Comparison of activity and characterization results showed that silver particles with size below 2 nm are the most active; larger particles are just “spectators”. The most probable silver active centers in the low-temperature CO oxidation are ionic species, mostly charged clusters Agnδ+, strongly interacting with the support. The obtained results in low-temperature CO oxidation might be of particular interest for neutralization of exhaust gases of car engines during “cold start”.

Original languageEnglish
Pages (from-to)121-131
Number of pages11
JournalFuel
Volume188
DOIs
Publication statusPublished - 15 Jan 2017

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Keywords

  • Effect of pretreatments
  • Low temperature CO oxidation
  • Si/Al ratio
  • Silver catalysts
  • ZSM-5

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Organic Chemistry

Cite this

Kolobova, E., Pestryakov, A., Mamontov, G., Kotolevich, Y., Bogdanchikova, N., Farias, M., Vosmerikov, A., Vosmerikova, L., & Cortes Corberan, V. (2017). Low-temperature CO oxidation on Ag/ZSM-5 catalysts: Influence of Si/Al ratio and redox pretreatments on formation of silver active sites. Fuel, 188, 121-131. https://doi.org/10.1016/j.fuel.2016.10.037