As-synthesized TEA-BEA zeolite: Effect of Si/Al ratio on the Knoevenagel condensation

作者：Chaves Thiago F; Pastore Heloise O; Hammer Peter; Cardoso Dilson^*

来源：Microporous and Mesoporous Materials, 2015, 202: 198-207.

DOI：10.1016/j.micromeso.2014.09.058

• Hydrothermal synthesis
• BEA structure
• Siloxy species
• Basic catalysis
• Knoevenagel condensation

The zeolite with BEA structure has been obtained using different Al amounts in the presence of tetraethylammonium as a structure directing agent. The effect of the Si/Al molar ratio on the crystal size, morphology, yield, chemical composition and catalytic properties was investigated. The materials have been characterized towards zeolitic properties by XRD, SEM, EDS, TGA, Si-29 MAS-NMR, XPS and TEM. The chemical composition of the crystals depends on the concentration of the initial reaction mixture and that a decrease in the Al content is associated with an increase in particle size. The characterization by TGA/DTA of as-synthesized zeolites with BEA structure showed that an increase of Si content resulted in the formation of [=Si-O-][TEA(+)] species, this was supported by Si-29 MAS-NMR. The XPS results also showed that the chemical composition of the surface differed from that of the bulk material, this was supported by TEM/EDS results. The results of catalytic activity tests indicated that a fraction of the [=Si-O-][TEA(+)]species was present on the external surfaces of the crystals, although the largest fraction appeared to be in the interior of the particles. As-synthesized BEA zeolite showed good catalytic activity and suggests that this material can be applied in other reactions involving basic sites.

• 出版日期2015-1-15