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The kinetics of the vapor-phase ammoxidation of m-xylene over a chromium-vanadium catalyst and an antimony-vanadium catalyst, in which the atomic ratio of chromium or antimony to vanadium was unity, was studied in a flow system and compared with that over a vanadium catalyst. The reaction-rate data obtained were then correlated with the reaction kinetic model proposed for a vanadium catalyst. There was no great difference in the reaction rates of m-xylene over the various catalysts. The ratios of the specific rate constant of m-xylene to that of m-tolunitrile, kx/kMboth mixed vanadium catalysts were considerably smaller than that for a vanadium catalyst. The relative ratio for the formation of m-tolunitrile from m-xylene, k1/kx, was nearly equal for a vanadium catalyst and a chromium-vanadium catalyst, but it was larger for an antimony-vanadium catalyst. The order of the relative ratio for the direct formation of carbon oxides and hydrogen cyanide from m-xylene was: vanadium catalyst>chromium-vanadium catalyst>antimony-vanadium catalyst. The order of the selectivity for the formation of isophthalonitrile from m-tolunitrile on these catalysts was similar to the order of kx/kM. It seems that those results may be ascribed to the weaker adsorptivity for m-xylene on mixed vanadium catalysts.

The kinetics of the vapor-phase ammoxidation of xylene isomers over a vanadium oxide catalyst was studied in a flow system. The reaction-rate data obtained for each xylene were then correlated with the rate equations based upon the Langmuir-Hinshelwood mechanism; this correlation suggested that each xylene reacted by a parallel consecutive reaction scheme in which tolunitrile was involved as an intermediate. The order of the relative ease of reaction was: para>meta\fallingdotseqortho. The ratio of the specific rate constant of xylenes, kx, to that of tolunitriles, kM, was 6 for meta and para isomers and 4 for the ortho isomer at 400°C; this ratio decreased with an increase in the reaction temperature. The order of relative ratios for the direct formation of dicyanobenzenes from xylenes was ortho>meta>para, while that for the direct formation of carbon oxides and hydrogen cyanide was ortho\fallingdotseqmeta>para. The ratio of the specific rate constant for the formation of dicyanobenzenes from tolunitriles, k2, to kMdecreased with an increase in the ratio of kxto kM. These results seem to result from the adsorptivities of xylenes and tolunitriles on the catalyst surface.

The kinetics of the vapor-phase ammoxidation of m-xylene and m-tolunitrile over a vanadium oxide catalyst were studied in a flow system. The reaction rate data obtained were correlated by the rate equation based upon the Langmuir-Hinshelwood mechanism, where the adsorption of m-xylene was strong. From the result of the experiments it was suggested that the reaction scheme consisted of four parallel routes: (1) the step-by-step ammoxidation of m-xylene to isophthalonitrile viam-tolunitrile; (2) the direct ammoxidation to isophthalonitrile from m-xylene; (3) the formation of carbon oxides and hydrogen cyanide viam-tolunitrile and (4) the direct formation of carbon oxides and hydrogen cyanide from m-xylene. The activation energies for the reaction of m-xylene and m-tolunitrile were 43.7 and 31.2 kcal/mol respectively in the range from 396 to 420°C.