Three series of Al-promoted strong solid acid samples were synthesized and characterized. Their catalytic activity in benzoylation of toluene with benzoyl chloride was also investigated. Experimental results show that the incorporation of appropriate amounts of Al~2O~3 into SO~4^2^-/ZrO~2, SO~4^2^-/TiO~2 and SO~4^2^- /Fe~2O~3 is helpful for stabilizing the sulfur species and increasing the effective acid sites on the catalyst surfaces, which can improve the strong acidity and catalytic activity in benzoylation. Microcalorimetric measurements of NH~3 adsorption on catalysts reveal that the remarkable strong acidity and catalytic activity of the Al- promoted catalysts are caused by a change of distribution of acid site strengths and an enhancement in the number of strong and intermediate-strong acid sites effective for the n-butane isomerization and benzoylation of toluene.

Key words: ALUMINIUM, SULFURIC ACID, ZIRCONIUM OXIDE, TITANIUM OXIDE, IRON OXIDE, SUPERACID, METHYLBENZENE, BENZOYLATION