The crystal quality and structure of AM-6

Microporous vanadosilicate AM-6, isostructural with titanosilicate ETS-10, is a no ve l pro mising material in the traditional zeolite applications such as catalysis, photocatalysis, gas separation, sorption and the monatomic-O-V-O-V-O chains have shown potential for use in quantum wire application. High purity vanadosilicate AM-6 products with different crystal quality (disorder, or average length of the V-O-V chains in the AM-6 framework) and sizes in the range of ∼50 nm to ∼6 μm were hydrothermally synthesized at 448-503 K using tetramethylammonium (TMA+) io n s. The combined SEM, EDX, XRD, Raman, TGA, XPS, and nitrogen adsorption isotherm data showed that by treating these as-synthesized materials in gaseous ammo nia at 673 K it is possible to completely remo ve TMA+ io n s fr o m t he AM-6 pores without adversely affecting product crystallinity and the micropore structure of AM-6, and with only minimal degradation of crystal quality of the resulting products. However, the success in a complete re mo va l o f TMA+ ions without affecting other crystalochemical characteristics of the product depended on its init ial crystal qualit y. TMA+ ions could not be completely remo ved from the lowest crystal qualit y product (FWHM=20.3 cm-1) without completely decomposing the V-O-V chains. The intermediate crystal quality product (FWHM=15.0 cm-1) could be successfully ammonia-treated only at 673 K to remove TMA+ ions, but higher temperatures resulted in a complete decomposition of the V-O-V chains. The highest crystal quality product (FWHM=12.7 cm-1) retained the integrity of V-O-V chains as well as the long range order and the micropore structure when ammonia-treated up to 748 K.