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 bromidetriethanolamine. 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 10oO. 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-') 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 NH, sorption and from the TPD of NH,. The initial acid strengths of zeolite beta (up to 185 kJ mol-') 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-I), 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 Si02 layer structure at 368 K.

Synthesis of zeolite beta Part 2.—Formation of zeolite beta and titanium-beta via an intermediate layer structure

“…From thermal analysis three kinds of template molecules may be distinguished (see also ref. 13). TEAOH and TEA`interact with the aluminosilicate layer and are then degraded at ca.…”

Conversion of rice husk ash to zeolite beta

“…An amorphous silica aerogel has also been used in the synthesis of zeolite Beta with low template content (Maria et al, 1997). Other organic templating agents, such as dibenzyl-1,4-diazabicyclo(2,2,2) octane chloride dibenzyl-dimethylammonium ion (Calvert et al, 1987), 4,4 0 -trimethylenebis(N-benzyl-piperidine) (Lohse et al, 1996), TEA halide-diethanolamine (Saxton and Zajacek, 1996), TEAOH-TEA halide-triethanol-amine, TEABr-NH 4 OH and TEAOH-TEABr chelates were explored for the synthesis of zeolite Beta. A detailed study of the synthesis of zeolite Beta using silica gel as a low cost silica source has been published (Ramanath and Kumar, 1990).…”

Acidic sites in beta zeolites in dependence of the preparation methods

“…Method 1: Sample denoted as Beta(55), with SiO 2 /Al 2 O 3 = 55, was synthesized by hydrothermal crystallization of the appropriate gel as described in [9]. It was washed with deionized water and dehydrated at 373 K for 2 h. Next, the sample was treated at 523 K for 2 h and finally heated from 523 to 823 K in an electrical furnace to burn the template off, slowly increasing the temperature.…”