Sulphated zirconia was prepared by

Sulphated zirconia was prepared by the method outlined by
Miao and Gao [6]. Zirconia powder was immersed in a 0.5 M
H2SO4 solution for 30 min, then, filtered and dried at 110 ◦C
for 24 h yielding the sulphate salt (SO4
2−/ZrO). Finally, it was
calcined at 500 ◦C for 2 h.
KNO3/KL zeolite was prepared by the impregnation method
with an aqueous solution of KNO3. It was reported that 21%
KNO3/KL zeolite exhibited the highest basic strength [7]. The
KL zeolite (40 g) was impregnated with KNO3 solution and followed
by drying at 100 ◦C. The KNO3/KL zeolite was, then,
calcined at 600 ◦C for 2 h.
Zirconia-supported potassium nitrate was prepared using the
method outlined by Wang et al. [8]. A 20% KNO3/ZrO2 was
prepared by grinding 40 g of ZrO2 with 8 g of KNO3, followed
by the addition of 24 ml of distilled water. The paste was kneaded
and then dried at 110 ◦C for 12 h, which was then calcined at
600 ◦C for 2 h