The skeletal isomerization of 3,3-dimethyl-1-butene over AlPO₄ (Al/P=1), CrPO₄ (Cr/P=1), and CrPO₄−AlPO₄ (CrAlP, 5–10 wt.% AlPO₄) catalysts is a first order reaction. Catalytic performance is affected by the precipitation agent. CrPO₄ catalysts obtained in propylene oxide-aqueous ammonia showed the highest activity. Moreover, the incorporation of AlPO₄ to CrPO₄ developed CrAlP catalysts that exhibited increased activity, irrespective of the precipitation method, as compared with both AlPO₄ and CrPO₄ catalysts. Besides, CrAlP catalysts prepared in propylene oxide-aqueous ammonia were the more active ones.