Abstract
In this study, IR studies of the coadsorption of ethanol and CO on Cu+ cations evidenced the transfer of electrons from ethanol to Cu+, which caused the lowering of the frequency of the band attributed to CO bonded to the same Cu+ cation due to the more effective π back donation of d electrons of Cu to antibonding π* orbitals of CO. The reaction of ethanol with acid sites in zeolite HFAU above 370 K produced water and ethane, polymerizing to polyethylene. Ethanol adsorbed on zeolite Cu(2)HFAU containing acid sites and Cu+exch also produced ethene, but in this case, the ethene was bonded to Cu+ and did not polymerize. C=C stretching, which is IR non-active in the free ethene molecule, became IR active, and a weak IR band at 1538 cm−1 was present. The reaction of ethanol above 370 K in Cu(5)NaFAU zeolite (containing small amounts of Cu+exch and bigger amounts of Cu+ox, Cu2+exch and CuO) produced acetaldehyde, which was further oxidized to the acetate species (CH3COO−). As oxygen was not supplied, the donors of oxygen were the Cu species present in our zeolite. The CO and NO adsorption experiments performed in Cu-zeolite before and after ethanol reaction evidenced that both Cu+ox and Cu2+ (Cu2+exch and CuO) were consumed by the ethanol oxidation reaction. The studies of the considered reaction of bulk CuO and Cu2O as well as zeolites, in which the contribution of Cu+ox species was reduced by various treatments, suggest that ethanol was oxidized to acetaldehyde by Cu2+ox (the role of Cu+ox could not be elucidated), but Cu+ox was the oxygen donor in the acetate formation.
Highlights
In our earlier paper [39], we reported that the way of preparation of copper containing faujasite-type zeolite of Si/Al = 31 determined the status and properties of Cu sites in these catalysts
Ethanol adsorbed on zeolite HFAU underwent dehydration toward ethane, which polymerized
Ethanol adsorbed on Cu(5)NaFAU containing mostly Cu+ox, Cu2+exch and Cu2+ox (CuO) was oxidized to acetaldehyde, and further to the acetate species
Summary
Cu-containing zeolites gained a great deal of attention because of their activity in the decomposition or reduction of nitrogen oxides [1,2,3,4,5,6,7,8,9,10,11,12,13], the ability of activation of multiple bonds in organic molecules [14,15,16,17,18,19,20] and the catalytic activity in various organic molecules. The increase in broad absorption band around 1600–1700 cm−1 may be due to water formation These results can be explained by the dehydration of ethanol on very strong protonic sites, increased upon heating to 510 K. These results can be explained by the dehydration of ethanol on very strong protonic sites, producing water and ethene, wwhhiich ppoollyymmeerriizzees, ffoorrmmiinngg ppoollyyeetthhyylleennee. The heating of the zeolite with reactants (ethanol, acetaldehyde and water) to 510 K caused the decrease in the bands of acetaldehyde with a simultaneous increase in the 1630 cm−1 band of water, evidencing the further reaction of acetaldehyde at higher temperature, in which water was produced. All these Cu-oxide forms may act as oxygen donors
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
