Heterogeneously Catalyzed Selective Oxidation Of Aromatics To Their Corresponding Aldehydes

Selective oxidation is one of privileged ways in petrochemical and finechemical production. It was reported that about 25% of industrial catalysisprocesses are through selective oxidation. Selective oxidation reaction isexothermal. Since deep oxidation to carbon dioxide and water is always thethermodynamically favored outcome of hydrocarbon oxidation, only selectiveoxidation of C-H bonds possesses applicable significance. The selectivity stillremains a challenge in these researches. This paper has proposed an effective wayto realize the high selectivity for target products by heterogeneously catalyzedselective oxidation employing molecular oxygen as oxidants in liquid phase.This paper has firstly reported heterogeneously catalyzed selective oxidationof toluene to benzaldehyde with molecular oxygen in liquid phase. It has beenfound that copper and iron oxides catalyst supported on ?-Al₂O₃ was beneficial forconversion and selectivity. Recycling tests showed that the catalyst could be usedfour times without losing activity and selectivity. Characterized by XRD, catalystremained intact after repeated use. In situ capping method (ICM) was employed inheterogeneous catalytic oxidation in this paper. Employing pyridine as in situcapping additive, the selectivity to benzaldehyde was increased from 45.6% to85.9% and the conversion of toluene was maintained above 7%. The selectivity tobenzyl alcohol and benzoic acid decreased remarkably.This paper has also firstly reported selective oxidation of cresols tocorresponding aldehydes employing heterogeneous catalysis and molecularoxygen in liquid phase. Copper and cobalt oxides catalyst supported on activecarbon (CuCo/AC) showed specific selectivity for salicylaldehyde and realized74% conversion of o-cresol and 57% selectivity for salicylaldehyde. Copper andmanganese oxides catalyst supported on active carbon was beneficial of selectiveoxidation of p-cresol. A conversion of 99% and a selectivity of 96% forp-hydroxybenzaldehyde were obtained based on CuMn/AC catalyst. TheCuMn/AC catalyst can be reused after washing and drying. Aiming at improving the yield of benzaldehyde in factory, this research hasdeveloped two catalysts: JY-3 and JY-4. The two catalysts were optimized underthe same reaction conditions with present industrial production installations on thespot. It was proved that JY-3 could greatly improve the yield of benzaldehydeunder mild reaction conditions and JY-4 could increase the yield of benzaldehydeand maintain the production of benzoic acid. More than five by-productsdisappeared and three kinds of by-products decreased.