Preparation of novel uniform mesoporous alumina catalysts by the sol-gel method

A novel sol-gel process for preparing alumina sol is reported in this artic le. Ultrasound is used to prepare the alumina sol at room temperature. The study of the effect of ultrasound as a function of treatment time on the pH and the particle diameter distribution of the sol was also made. Al-27 NMR , TEM, XRD and DTA were used to detect the properties of the sol and the al umina materials. The result of Al-27 NMR shows that there existed Al-13(7+) species in the sol. The acid used not only acted as catalyst for peptizing , but also as reactant to react with aluminum hydroxide to produce the Al-1 3(7+) species. On the other hand, TEM results show that the morphology of t he particles was spherical in the sol, but transformed to needle-like as we ll as spherical when calcined at 450 degreesC. At the end, the morphology o f the particles changed to spherical again at 550 degreesC. By using this a lumina sol as precursor, an alumina material with uniform mesoporous distri bution was formed after calcination at 550 degreesC without adding any temp lates or other organic additives. The results of this work also show that t he formation of alumina with uniform mesoporous distribution is related to its crystalline phase, the morphology of the particles and the particle dia meter distribution of the precursor sol. (C) 2001 Elsevier Science B.V. All rights reserved.