Nature and mode of addition of phosphate precursor in the synthesis of aluminum phosphate and its influence on methanol dehydration to dimethyl ether

• Published in: Catalysis communications 2006-10, Vol.7 (10), p.745-751
• Main Authors: Siva Kumar, V., Padmasri, A.H., Satyanarayana, C.V.V., Ajit Kumar Reddy, I., David Raju, B., Rama Rao, K.S.
• Format: Article
• Language: English
• Subjects: 27Al and 31P MAS NMR; Aluminum phosphate; Dehydration; Dimethyl ether; Methanol; NH 3-TPD
• ISSN: 1566-7367; 1873-3905
• DOI: 10.1016/j.catcom.2006.02.025

Four aluminum phosphate catalysts with Al/P = 1 were prepared by precipitation of mixture of aluminum nitrate and phosphate precursor (either phosphoric acid or diammonium hydrogen phosphate) with NH 3 and precipitation of aluminum nitrate with NH 3 followed by impregnation of phosphate precursor (either phosphoric acid or diammonium hydrogen phosphate). The catalysts were characterized, using different physico-chemical methods viz., BET-S.A., XRD, FT-IR, and NH 3-TPD. 27Al and 31P MAS NMR spectroscopy was used to characterize selected catalysts in order to find out the presence of Al and P environments. The catalytic conversion of methanol to dimethyl ether was conducted over these catalysts in a temperature range of 448–548 K at atmospheric pressure. AlPO 4 prepared by precipitating the mixture of aluminum nitrate and (NH 4) 2HPO 4 with aq. NH 3 generated more number of moderate acid sites and showed higher methanol dehydration activity with 100% selectivity to DME at 548 K.