Direct oxidation of isooctanol to isooctanoic acid over molybdovanadophosphoric heteropoly acid
A series of molybdovanadophosphoric heteropoly acid catalysts were prepared by precipitation method.With oxygen as the oxidant,the catalyst was used for one-step oxidation of isooctanol to isooctanoic acid under atmospheric pressure.The effects of vanadium and cesium addition,as well as process conditions,on the catalyst performance and the reaction were investigated,and possible reaction mechanisms were deduced.The results showed that vanadium could accelerate the redox cycle of catalysts and improve their redox performance and catalytic efficiency,while cesium could affect the acidity and specific surface area of the catalyst by replacing protons in heteropolyacids.Appropriate acidity,high specific surface area,and rapid redox cycle processes were key factors for catalysts to have high activity and selectivity.Among all the prepared catalysts,Cs3H2PMo10V2O40 showed the best catalytic activity under the optimal reaction conditions(solvent is benzene,reaction temperature was 120℃,catalyst dosage was isooctanol mass 11%of,oxygen flow rate was 20mL/min,reaction time is 10h),and the conversion of isooctanol could reach 60.7%,and the selectivity of isooctanoic acid was 81.5%.The catalyst could be reused for 5 times with good stability.