The Liquid-phase Heterogeneous Oxidation Of Coking Toluene

The liquid-phase heterogeneously catalytic oxidation of the coking tolueneproduced by extraction distillation has been investigated in this study, and copared itwith petrotoluene. Results indicated that the conversion rates of the petrotoluene andthe coking toluene were high even under the moderate conditions （the pressure ofoxygen is1.0MPa, at413K）. Details of the studies are as follows:Firstly, the results of liquid-phase heterogeneous oxidation of petrotoluenesuggested that UOyhad the ability of inducing the liquid-phase oxidation of toluene,with the major product of benzoic acid at a temperature higher than433K.Petrotoluene conversion was66.37%, and benzoic acid selectivity was93.45%at463K and oxygen pressure of1.0MPa. On the other hand, the conversion rate oftoluene could reach100.00%if UOy was applied as catalyst, NaBr as promoter, aceticacid as solvent. Petrotoluene conversion was100.00%, and the selectivities ofbenzaldehyde and benzoic acid were64.06%and25.32%.Secondly, results of the liquid-phase heterogeneous oxidation of coking tolueneindicated that100.00%coking toluene has been converted into products in severalcatalytic systems. For example, a conversion rate （100.00%） of coking toluene couldbe achieved in the catalytic systems of [UOy/W（NO₃）₃·xH₂O]/[NaBr]/[atetic acid] or[Co（CH₃COO）₂·4H₂O/Mn（CH3COO）2·4H₂O/W（NO₃）₃·xH₂O]/[NaBr]/[acetic acid] at413K and oxygen pressure of1.0MPa. The whole selectivity of benzaldehyde andbenzoic acid was higher than99.52%in the formor system.Finally, the mechanisms of liquid-phase heterogeneous oxidation for bothpetrotoluene and coking toluene were explored by experiments. It is found that thecatalytic oxidation of coking toluene would be greatly facilitated by synergism ofU-W. The bromide was converted to Br2and promoted activation of toluene byradical mechanism.Thereby the initiative temperature was lowered and the reactionaccelerated.The experimental results indicated that both petrotoluene and coking tolueneconversions colud reach100.00%in [UOy/W（NO₃）₃·xH₂O]/[NaBr]/[acetic acid]catalytic oxidation system, and the theoretical analysis showed the reaction wereobeyed by radical mechanism. The production cost could be cut down with bettereconomic and environmental benefits if coking toluene is used.