Oxidation of methacrolein over 12-molybdophosphoric acid and its salt catalysts at 300℃ was investigated by use of micropulse reaction system.
Effects of pyridine adsorbed on 12-molybdophosphoric acid catalyst and variation of acidic sites on $Al^{3+}$, $Ag^+$ salt catalysts were studied, and carbonyl stretching vibration of methacrolein adsorbed on 12-molybdophosphoric acid was observed using Fourier-transform infrared spectrometer, to obtain information about active sites in the catalytic oxidation.
The catalytic activity decreased with increasing amount of pyridine adsorbed on the catalyst and increased with increasing of acidic sites on the salt catalysts. The carbonyl stretching vibration of methacrolein shifted to a low frequency (about 20cm$^{-1}$) upon adsorption on the catalyst.
