Co-templated synthesis of polymorph A-enriched zeolite beta

• Polymorph A-enriched zeolite beta was synthesized with a co-template strategy.
• The synthesis cost for polymorph A-enriched zeolite beta was significantly reduced.
• The co-template strategy opens a new way to synthesize polymorph A-enriched beta.

The initial mixture containing fully hydrolysed tetraethyl orthosilicate (TEOS) and tetraethylammonium hydroxide (TEAOH) solution was treated either by heating at 80 °C or by freeze-drying. After adding an appropriate amount of concentrated hydrofluoric acid, the resulting mixture was crystallized at 150 °C. The heating treated mixture produced polymorph A-enriched zeolite beta while freeze-drying treated mixture gave only normal zeolite beta. The 13C magic angle spinning nuclear magnetic resonance (MAS NMR) analysis and thermogravimetric analysis (TGA) indicated that a partial decomposition of TEAOH to generate triethylamine (TEA) occurred during the heating dehydration process, which was the only difference compared with the freeze-drying process. Together with the reduced TEAOH, different monoamines as a co-template directed the polymorph A-enriched zeolite beta with the freeze-drying process. Diamines as a co-template directed only the normal zeolite beta. The synthesis cost of polymorph A-enriched zeolite beta can be significantly reduced by lowering the usage of expensive TEAOH and using cheaper monoamines.

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