Ecofriendly production of ethylene by dehydration of ethanol over Ag3PW12O40 salt in nitrogen and air atmospheres

Neutral silver salt of tungstophosphoric acid Ag3PW12O40 center dot 3H(2)O (AgPW) was investigated as the catalyst in the gas-phase dehydration of ethanol, in the temperature range of 373-493K. The relative humidity of atmosphere (nitrogen or air) was changed from 2% to 10%. It was shown that relative humidity of both atmospheres strongly influences the catalytic activity of AgPW salt. The thermal stability of AgPW salt was determined with simultaneous DSC/TG analysis and high temperature XRD method. It was demonstrated that one molecule of water, which hydrates silver cation loses the salt structure in the temperature range of 473-523 K. The stability of primary and secondary structure of AgPW salt after reaction was investigated using FT-IR and XRD techniques. The AgPW salt is stable, when relative humidity attains at least 10% independent of atmosphere in which reaction is performed. In such conditions and at 473 K the AgPW catalyst exhibited the conversion of ethanol as well as the selectivity to ethylene about 99%. It can be concluded that Ag3PW12O40 center dot 3H(2)O salt can be used as an 'ecofriendly' catalyst for ethylene production by the dehydration of ethanol in nitrogen or air atmospheres in relatively low temperature and appropriate relative humidity. (C) 2012 Elsevier B.V. All rights reserved.