A novel method for synthesis of nonylated diphenylamine by alkylation of diphenylamine with nonene over Fe-promoted SO42-/ZrO2 catalysts

Abstract

As a green and efficient antioxidant, nonylated diphenylamine (NDPA) is of great significance to fields such as lubricants, synthetic rubber, and plastic. However, traditional catalysts for synthesizing NDPA still exhibit drawbacks of low efficiency, equipment corrosion, non-renewability, and environmental pollution. To overcome these challenges, a series of Fe-promoted SO42-/ZrO2 catalysts were successfully developed and employed for the first time in the alkylation of DPA and NON to synthesize NDPA in our present work. Both synthesis variables of catalysts and reaction conditions were well optimized. The as-synthesized NFe2.50S1.0Z catalyst possessed excellent catalytic performance with a high yield of mono- and di-nonyl-diphenylamine, as well as better reusability and stability than activated clay. After 5 reaction cycles, over 90 % of the catalytic activity could be recovered by the thermal treatment. These observations make the Fe-promoted SO42-/ZrO2 catalyst a promising candidate for industrials. Additionally, to systematically investigate and elucidate the promoting effects of Fe on sulfated zirconia catalysts, a thorough characterization of the physicochemical properties of these catalysts was conducted through various techniques, including XRD, SEM, TEM equipped with EDX, N2 adsorption-desorption isotherms, EA, ICP-OES, FT-IR, XPS, and NH3-TPD. The results indicated that the introduction of a small amount of Fe into the catalyst promoted the stabilization of T-ZrO2, smaller grain sizes, increased specific surface area, and strong acidity, which in turn positively affected the catalytic performance. In addition, a possible reaction mechanism of Fe-promoted SO42-/ZrO2 catalyst for catalyzing the alkylation of DPA with NON was proposed.