Showing papers by "Rolf Fricke published in 1996"

Synthesis of zeolite beta. Part 1.—Using tetraethylammonium hydroxide/bromide with addition of chelates as templating agents

Abstract: The synthesis of zeolite beta has been studied using the following templating agents: (i) tetraethylammonium hydroxide (TEA;)(ii) tetraethylammonium bromide–diethanolamine; and (iii) tetraethylammonium hydroxide–tetraethylammonium bromide–triethanolamine. TEA+ ions and TEAOH molecules only have a structure-directing effect. The ratio (Si + Al)/TEA+ in the gel was varied from 2 to 10, the Si/Al ratio from 12 to 1000. The temperature of crystallization was chosen in the range 368–443 K. The samples were characterized using X-ray diffraction, micrographs, chemical analysis, thermal analysis, IR spectroscopy and nitrogen adsorption. Zeolite beta of good crystallinity (micropore volume = 0.28 cm3 g–1) was obtained with Si/Al ratios from 14 to 72. The acid strength and number of acid sites were determined from the calorimetrically measured heat of NH3 sorption and from the TPD of NH3. The initial acid strengths of zeolite beta (up to 185 kJ mol–1) are higher than those of other high-silica zeolites.Polycrystalline agglomerates are formed instead of small single crystals on the addition of diethanolamine to the synthesis gel. The agglomerates are characterized by a high intercrystalline volume (> 0.47 cm3 g–1), which can be influenced in a definite manner by variation of the TEABr/diethanolamine ratio. The presence of triethanolamine initiates the transformation of zeolite beta into a SiO2 layer structure at 368 K.