Relationship Between Structure And Performance Of Catalyst In M-Xylene Oxidized To Isophthalic Acid

Isophthalic acid?IPA?is an important chemical intermediate and chemical raw material,it is of great significance to study an environmentally friendly bromine-free catalytic system to produce IPA.In this paper,the surface chemical properties and physical structure of the coconut shell activated carbon?AC?are changed by different modification methods.Activated carbon that has been modified supported phosphotungstic acid?HPW?is used as a catalyst to catalyze m-xylene?MX?oxidized to isophthalic.Use H₂O₂?ZnCl₂?acetic acid,tartaric acid and oxalic acid to modify activated carbon can effectively improve the catalytic effect of the catalyst,the optimum modification conditions and experimental results is as follows:?1?H₂O₂:impregnation concentration:3.75%,impregnation temperature:40 ?,impregnation time:7 h,calcination temperature:700 ?,calcination time:4 h.The number of acidic groups on the surface of activated carbon modified in optimum modification conditions has an increase of 111.39%and the specific surface area of catalyst improved 13.01%.The conversion of MX reached 99.02%and the IPA mass concentration in the reaction solution increased by 40.56%after the reaction was carried out for 180 min.?2?ZnCl₂:impregnation concentration:0.1 mol/L,impregnation time:6 h?40 0C?,calcination temperature:600 ?,calcination time:4 h.The number of acidic groups on the surface of activated carbon modified in optimum modification conditions has an increase of 181.86%and the specific surface area of catalyst improved 4.02%.The conversion of MX reached 97.65%and the IPA mass concentration in the reaction solution increased by 78.89%after the reaction was carried out for 180 min.?3?Acetic acid:impregnation concentration:3.5 mol/L,impregnation time:24 h?40 ??,calcination temperature:500 ?,calcination time:4 h.The number of acidic groups on the surface of activated carbon modified in optimum modification conditions has an increase of 163.87%and the specific surface area of catalyst improved 9.31%.The conversion of MX reached 97.44%and the IPA mass concentration in the reaction solution increased by 76.67%after the reaction was carried out for 180 min.?4?Tartaric acid:impregnation concentration:2 mol/L,impregnation time:10 h?40 ??,calcination temperature:450 ?,calcination time:4 h.The number of acidic groups on the surface of activated carbon modified in optimum modification conditions has an increase of 201.35%and the specific surface area of catalyst improved 0.71%.The conversion of MX reached 96.54%and the IPA mass concentration in the reaction solution increased by 71.11%after the reaction was carried out for 180 min.?5?Oxalic acid:impregnation concentration:0.2 mol/L,impregnation time:16 h?40 ??,calcination temperature:450 ?,calcination time:4 h.The number of acidic groups on the surface of activated carbon modified in optimum modification conditions has an increase of 198.35%and the specific surface area of catalyst improved 8.76%.The conversion of MX reached 96.54%and the IPA mass concentration in the reaction solution increased by 56.67%after the reaction was carried out for 180 min.The content of acidic groups especially phenolic hydroxyl group and carboxyl group on activated carbon has a greater influence on the catalytic effect of the catalyst than the pore structure.Catalysts with better micropore specific surface area have better catalytic activity when the surface chemistry of activated carbon is similar.