Efficient dehydration of ethanol on the self-organized surface layer of H 3 PW 12 O 40 formed in the acidic potassium tungstophosphates

•Surface layer of HPW in K2 and K2.5 salts exhibits higher reactivity than bulk HPW.•Dehydrated protons transform ethanol to ethylene much easier than hydrated protons.•The [N2H7]+ are mostly formed on dehydrated protons while the NH4+ on hydrated ones.•Secondary structure of K2.5 salt is thermally stable in contrast to that of K2 salt.