Preparation of silica-alumina catalyst by the sol-gel method and its activity for the Diels-Alder reaction of isoprene and acrylaldehyde Original Research Article

In the presence of 2-PrOH and oxalic acid, a porous silica-alumina has been prepared by the sol-gel method from Si(OEt)4 and Al(NO3)3 · 9H2O. The surface area, the average pore size, the pore volume and most importantly, the number of the acidic sites in the range of pKa ≤ −3.0 are greatly increased by the use of oxalic acid as the organic additive. The silica-alumina prepared by the new method is found to catalyze the Diels-Alder reaction of isoprene and acrylaldehyde efficiently, improving the yield and the regioselectivity.