Study On The Synthesis Of Keggin Heteropoly Compounds And Their Catalytic Performance For The Oxidation Of Benzene

Heteropoly compounds have great utilities in catalysis because of their acidity and oxidation-reduction quality.Compared with the traditional catalysts,it has the determination internal structure,a unique pseudo-liquid phase,in polar solution,such as the advantages of good solubility.In the organic catalytic reaction,the heteropoly compounds show high catalytic activity and selectivity.Because it is low in the response to equipment's corrosiveness,the response condition is temperate.Therefore, it received the widespread attention in recent years.In our work,three vanadium substituted heteropoly acid have been synthesized by acidification-etherization.Based on this work,we take(C₄H₉)₄N⁺ as the positive ion, and synthesized phosphorus molybdenum vanadium heteropoly compounds.Its internal structure was analyzed by FT-IR,XRD,³¹P-NMR.The analysis result indicated that this kind of varied compound has the Keggin-type structure.In order to study the heteropoly compound catalytic activity which we prepare,we inspected this kind of catalyst in the benzene to phenol and benzene to aniline reaction.1.Catalytic hydroxylation of benzene to phenolIn the benzene hydroxylation of phenol reaction,we choice of 30%H₂O₂ as oxidant in acetic acid as solvent,inspected the effects of reaction temperature,reaction time, oxidant dosage,the amount of catalyst on the reaction.Under the optimum condition, the phenol yield and selectivity were 27.87%,89.04%.2.Catalytic ammoniation of benzene to anilineTake the benzene as raw material,the oxammonlum hydrochloride is the ammonia source,choice of 10%NaClO as oxidant in acetic acid as solvent,we inspected the effects of reaction temperature,reaction time,oxidant dosage,the amount of catalyst on the reaction.Under the optimum condition,the aniline yield were 10.69%.The experimental results show that the vanadium-substituted P-Mo-V quaternary ammonium salts showed excellent catalytic oxidation capacity.In the heteropoly compound,the introduction vanadium element may enhance the catalyst oxidizing ability,the vanadium introduction quantity are more,the catalyst oxidizing ability is stronger,but Simultaneously will reduce the catalyst the selectivity.Take the organic positive ion as the counter-ion,may change the heteropoly compound in organic solvent solubility,simultaneously enhances the catalyst catalyzed oxidation activeness.