Effects Of Modified Catalysts On Nitrous Oxide Nitrated Toluene

The traditional mixed acid nitrification process has severely corroded the equipment and caused serious environmental pollution.Nitrogen pentoxide is a new type of green nitrating agent,which has the advantages of mild reaction conditions,easy product separation,strong nitrification ability,and no need for waste acid treatment for nitration.Solid acid catalysts have been widely used in many industrial fields.Their unique acid sites and mesoporous structure can not only improve the yield of organic synthesis,but also have excellent selectivity.Combining the two for nitrification reaction is expected to provide a new type of green nitrification process.In this paper,the nitrification capacity of nitrous oxide / dichloromethane system for toluene was studied,and the effect of solid acid catalyst on toluene nitration was investigated.Using HZSM-5,diatomaceous earth,kaolin,4A molecular sieve and other solid acids as toluene nitration catalyst,the catalytic activity of the solid acid catalyst was investigated.Ion exchange method,impregnation method,alkali modification and mixed modification were used to modify HZSM-5 respectively,and characterized by XRD,pyridine infrared and other means to study the effect of modification on catalyst structure and acidity.The modified catalyst was used to nitrify toluene,the influence of the modified catalyst on the nitrification performance of nitrous oxide was investigated,and the best reaction conditions and modification scheme were obtained.The results showed that different catalysts showed good catalytic activity,and the conversion and selectivity of toluene were greatly improved,among which HZSM-5 had the best catalytic activity,and the yield and selectivity of mononitrotoluene reached 45.2% and 82.3%,respectively.Compared with the unused catalyst,it is greatly improved.The four modification schemes all improve the activity of the catalyst.The modification effect of the impregnation method is better than the ion exchange method.The modified B acid of the catalyst combines with the metal ion to form the metal ionL acid,which effectively improves the yield of mononitrotoluene.Among them,the catalyst activity after Cu and Fe modification is higher,the yield of mononitrotoluene is 67.7% and 59.1% respectively.After alkali modification,the catalyst pore size becomes larger.When the modification concentration does not exceed 0.3mol / L,it can effectively improve the catalytic activity.The mixed modified catalyst has the best activity,and the nitrification yield and selectivity of Cu-Z5-0.2M reached 72.3% and 98.7%,respectively.Through the control experiment,the best reaction conditions for nitrification are: reaction temperature 15?,catalyst dosage 20wt%,alkali modification optimal concentration 0.2mol / L,and impregnation method optimal loading 4wt%.