There is no acidic aluminum oxide. Aluminum oxide has amphoteric properties. It reacts with both acids and bases. Selective monoestherification of dicarboxylic acids should be done in an alkaline medium. Then the alumina will exhibit acidic properties.

Thanks Professor Yuri Mirgorod for your valuable answer.

Could you have a look to the attached file. 

You cannot convert neutral alumina to acidic. You can buy acidic alumina. other information you can take from SI of the article

Thanks

Acidic alumina is prepared is adjusted by adding HCl in aqueous suspension until the extract has a pH of 4-6.

can u please elaborate more precisely sir