The loading of KI, K2CO3, KBrO3 and C8H5O4K on the surface of ZrO2 generated weaker base sites with base strengths ranging in between 7.2 and 9.8. Considering the base strengths and the catalytic activities, it was obvious that the activities of ZrO2-supported catalysts related with their base strengths and yields. For catalytic sites of KOH/ ZrO2, K2O species were possibly formed by dehydroxylation of the OH groups which could have contributed to catalytic activity
of the catalyst.