A novel approach has been proposed for stabilization of potassium in combustion of carbonaceous soot matters emitted from diesel engine vehicles. Sodalite, a clathrate aluminosilicate zeolite, is employed as a support for holding catalytically active potassium species. This approach resulted in a high-catalytic activity and the activity is further enhanced after hydrothermal treatment at 800 degrees C. Such kinds of tectoaluminosilicate hold potassium strongly and possess high stability against high temperatures and alkaline conditions induced by hydrated potassium ions under practical driving conditions. (C) 2007 Elsevier B.V. All rights reserved.