Studies of Al₂O₃-K catalysts prepared using various precursors for diesel soot elimination

The optimal calcination temperature was 600 °C and the highest activities were obtained at Al:K molar ratios of 3:1, 1:1 and 1:1 for Al₂O₃/KNO₃, Al(NO₃)₃/KNO₃ and Al₂O₃/KOH precursor combinations, respectively. The active compound in the catalyst prepared by Al(NO₃)₃/KNO₃ was KNO₃ exclusively. However, the catalytic activity of the catalysts prepared by Al₂O₃/KOH was affected by the formation of K₂Al₂O₄ and K₂CO₃ compounds. The catalysts prepared by all precursor combinations behaved a comparable thermal stability. High temperature aging of the catalysts would result in the loss of surface area and/or active compounds, and hence the deterioration of their catalytic activities.