Study On The Catalytic Synthesis Of N,N’-di-alkyl-p-phenylene Diamines

p-Phenylene diamine derivatives are an important class of organic intermediatesand products, which are widely applied in fine chemical, pharmaceuticals, agriculturalchemicals, pigments, rubber antioxidants and antiseptics. Among the syntheticmethods for N,N’-di-alkyl-p-phenylene diamines, the reductive alkylation ofp-nitroaniline with ketone is of most applied value. The preparation ofN,N’-di-alkyl-p-phenylene diamines is investigated systematically in this paper basedon the reductive alkylation of p-nitroaniline with butanone to N,N’-di-sec-Butylp-phenylenediamine(DBPD).1. The synthesis of DBPD by the reductive alkylation of p-nitroaniline withbutanone was studied as a basic reaction. A series of Cu-based catalysts were designed,prepared and examined for this reductive alkylation, thereinto, Cu20Cr5Ca5/γ-Al2O3showed excellent results and was chosen for this reaction. The reaction parameterswere optimized. Under the optimum reaction conditions:130℃,3.0MPa,0.3ml/min,the conversion of p-nitroaniline was100%and DBPD was obtained in a98.0%yield.The catalytic process proceeded under optimum reaction conditions for100h and stillkept higher catalytic activity and selectivity2. The catalysts were studied by XRD, XPS, H2-TPR, NH3-TPD, TEM and SEM.It was found that doped Cr remarkably enhanced the activity and stability ofCu/γ-Al2O3due to the better dispersion of Cu0which can supply more active centersand prevent the sintering and aggregation of copper. Additionally, it was found thatthe introduction of Ca to Cu-Cr/γ-Al2O3led to a higher selectivity because of aremarkable decrease of the catalyst acidity.3. The reductive alkylation of p-nitroaniline with ketones to di-alkyl-p-phenylenediamines over Cu20Cr5Ca5/γ-Al2O3was systematically studied and satisfactory yieldswere obtained. Under the optimized reaction conditions, the selectivity ofN,N’-di-isopropyl-p-phenylenediamine was only92.1%, while the selectivity of otherN,N’-dialkyl-p-phenylenediamines were obtained over97.0%. It demonstrated thatCu20Cr5Ca5/γ-Al2O3may be used in large-scale industries.