Synthesis of Al-Si-beta and Ti-Si-beta by the aging-drying method

Al-Si-beta and Ti-Si-beta were synthesized by the aging-drying method in fluoride medium without seeding and using tetraethylammonium hydroxide as organic structure-directing agent (OSDA). In the aging-drying method the gels are allowed to release some volatile species (mainly ethanol and water). Samples with molar batch composition: SiO2:0.54TEAOH:0.7HF:xH(2)O:yM(n+)F(n)(-) (where x approximate to 10, y = 0.02, M = Al or Ti) were aged and dried during about one week. Organic solvents were added to selected aged-dried gels to determine their role as complementary OSDA. All samples were hydrothermally treated at 140 degrees C during 1-12 days. After crystallization, samples were characterized by PXRD, SEM, TGA-DTG, FTIR, atomic absorption, low temperature nitrogen adsorption, Si-29 MAS NMR and Al-22 MAS NMR. Pure and well-crystallized zeolite beta samples were obtained in all experiments performed. Polymorph A enrichments of about 69% and 64% were reached for Ti and Al loaded samples, respectively. AI-loaded samples exhibited small average crystal sizes compared with Ti-loaded samples. The incorporation of Al in the beta framework was proven by several techniques and the Al/Si ratios were similar to those of the precursor gels. However, Ti incorporation was quite low. (C) 2011 Elsevier Inc. All rights reserved.