Effect of potassium addition on catalytic activity of SrTiO3 catalyst for diesel soot combustion

• Published in: Applied catalysis. B, Environmental Vol. 101; no. 3-4; pp. 169 - 175
• Main Authors: Ura, B., Trawczyński, J., Kotarba, A., Bieniasz, W., Illán-Gómez, M.J., Bueno-López, A., López-Suárez, F.E.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 14.01.2011; Elsevier
• Subjects: Catalysis; Catalyst; Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Perovskite; Potassium stability; Soot combustion; Strontium titanate; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Strontium titanate; Soot combustion; Perovskite; Potassium stability; Catalyst; Perovskite type compound; Soot; Ignition; Oxides; Combustion; Decomposition; X ray; Laboratory; Promoter; Strontium; Work function; Synthesis; Photoelectron spectrometry; Structure; Catalytic reaction; Stability; Transition element compounds; Titanates; Desorption; X ray diffraction; Heterogeneous catalysis; Impregnation; Sol gel process; Potassium addition; Alkalinity; Cyclohexanol; Catalyst activity; Potassium; Environmental protection
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2010.09.018

[Display omitted] ▶ The positive effect of potassium addition on the catalytic activity of strontium titanate in soot oxidation can be interpreted in terms of two mechanisms of potassium action: enhancement of oxygen surface mobility and oxygen vacancies formation in the oxygen sublattice of perovskite structure depending on the potassium localization. ▶ The experimental results (potassium volatility, work function changes, basicity, XPS spectroscopy) revealed that the vacancy mechanism is the most efficient in stimulating the soot combustion catalytic reactivity of strontium titanate. SrTiO3 based mixed oxides with perovskite-like structure were prepared by sol–gel citric method. The potassium promoter (2mol%) was introduced into the material during the synthesis as well as via post-impregnation, leading to two different catalytic systems: Sr0.8K0.2TiO3, and K/SrTiO3, respectively. The obtained materials were characterized by XRD, SBET, cyclohexanol (CHOL) decomposition, XPS and SR-TAD (species resolved thermal alkali desorption), whereas their catalytic activity in soot combustion was examined in laboratory conditions. It has been shown that introduction of potassium substantially promotes the catalysts activity, which can be gauged by the lowering of the soot ignition temperature by 100°C for K/SrTiO3 and 120°C for Sr0.8K0.2TiO3. The effect is discussed in terms of potassium volatility, work function changes and basicity, however the experimental data revealed that the indirect effect is also involved. The most active system was obtained when potassium partially substituted strontium in the perovskite structure. As a consequence oxygen vacancies were created, leading to higher concentration of basic surface oxygen species. Since in the case of Sr0.8K0.2TiO3, K+ ions are located in the structural positions, this catalyst apart from the highest activity exhibits also the highest potassium stability.