芳香族ニトリルの接触合成反応に関する研究 (第4報)
酸化剤としてSO2を用いるアンモ酸化反応の反応機構
1974 年 17 巻 9 号 p. 761-767
詳細
1974 年 17 巻 9 号 p. 761-767
The kinetics, the induction period, the changes of surface area of catalyst, amounts of chemisorption of SO2 and NH3 and the catalytic activity during the course of the reaction, and E.S.R. and infrared spectra of catalyst surface were investigated in order to elucidate the course of ammoxidation reaction using SO2.
(1) The reaction rate equations were obtained over γ-Al2O3 and γ-Al2O3-V2O5-MoO3 catalysts at 430°C as follows;
r=kP0.97NH3P0.95SO3P0.87Toluene (γ-Al2O3)
r=kP1.03NH3P0.93SO3P0.84Toluene (γ-Al2O3-V2O5-MoO3)
Arrhenius plot of the initial rate gave a similar pattern to that of the dehydrogenation reaction as shown in the previous paper. Namely the plot was composed of two straight lines divided by a bending point at 415°C and it was infrared that the process where a hydrogen atom of methyl group was abstracted by active species was a rate determinant.
(2) The activity induction period which was observed in the begining of the reaction, was appreciably shortened or disappeared by a preliminary treatment of catalyst with NH3, SO2, (H2+SO2), (H2+ SO2+NH3), Sx or (NH4)2Sx.
(3) From the measurement of the surface area of catalyst and the amounts of chemisorption of SO2 and NH3 in the course of the reaction, it was found that the adsorption amount of NH3 and the surface area of catalyst had no direct correlation with the catalytic activity, but it was reduced with decrease in the amount of chemisorption of SO2 over γ-Al2O3 catalyst.
(4) From the measurement of infrared and E.S.R. spectra, it was found that SO2 adsorbed strongly over γ-Al2O3 catalyst to form some active radicals of SO2 or Sx, over which NH3 adsorbed weakly.
From the above results, a route of benzonitrile formation was infrared as follows;
SO2→γ-Al2O3-Sx•→NH3γ-Al2O3NH3-Sx•
C6H5CH3→γ-Al2O3C6H5CH2→γ-Al2O3C6H5CH2NH2→-Sx•γ-Al2O3C6H5CN
; where -Sx• and NH2-Sx• represent sulfur containing radical and its complex with NH3 respectively.
Namely benzonitrile was formed through successive hydrogen abstraction with sulfur containing radicals.
