Framework cobalt and manganese in MeAPO-31 (Me=Co, Mn) molecular sieves
✍ Scribed by Nataša Novak Tušar; Gregor Mali; Iztok Arčon; Venčeslav Kaučič; Afshin Ghanbari-Siahkali; John Dwyer
- Publisher
- Elsevier Science
- Year
- 2002
- Tongue
- English
- Weight
- 435 KB
- Volume
- 55
- Category
- Article
- ISSN
- 1387-1811
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✦ Synopsis
Pure phases of CoAPO-31 and MnAPO-31 were synthesized hydrothermally using di-n-propylamine as a structuredirecting agent. The incorporation of manganese(II) and cobalt(II) into framework aluminum sites of AlPO 4 -31 was suggested from elemental, thermogravimetric and X-ray powder diffraction analysis. Isomorphous aluminum substitution with cobalt(II) was confirmed from static 31 P NMR spectra. UV-VIS and XANES spectra revealed a partial oxidation of framework cobalt(II) and manganese(II) into cobalt(III) and manganese(III) in the calcined MeAPO-31 and thus the presence of redox centers in the products. The generation of acid sites (Brønsted and Lewis) in MeAPO-31 was supported by IR measurements of pyridine and by ammonium adsorption/desorption. The strength of the acid sites in the catalysts studied decreased in the following order: MnAPO-31 > CoAPO-31 > AlPO 4 -31.