Chinese Journal of Applied Chemistry ›› 2022, Vol. 39 ›› Issue (6): 949-959.DOI: 10.19894/j.issn.1000-0518.210239

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Catalytic Properties of Silylated⁃Salicylaldimine Transition Metal Complexes Functionalized Nano⁃silica Catalysts in Ethylene Oligomerization

Feng LI, Shi-Yu LU, Yu ZHANG, Li-Jun GUO, Xue ZHAI, Cui-Qin LI()   

  1. Provincial Key Laboratory of Petroleum and Natural Gas Chemical Engineering,College of Chemistry and Chemical Engineering,Northeast Petroleum University,Daqing 163318,China
  • Received:2021-05-17 Accepted:2021-08-29 Published:2022-06-01 Online:2022-06-27
  • Contact: Cui-Qin LI
  • About author:licuiqin78@163.com
  • Supported by:
    the Natural Science Foundation of Heilongjiang Province(E2018012);Heilongjiang Postdoctoral Research Foundation(16190023)

Abstract:

Three kinds of silylated-salicylaldimine transition metal complexes functionalized nano-silica catalysts were prepared with silylated-salicylaldimine transition metal complexes as precursors and with nano-silica as support. Three kinds of heterogeneous catalysts were characterized by elemental analysis, FT-IR, SEM and ICP. The effect of the reaction parameters and the kinds of catalytic active center on the catalytic properties of the three heterogeneous catalysts were investigated with methylaluminoxane (MAO) as the cocatalyst. The results show that when the precatalyst dosage is 7 μmol, the molar ratio of Al/M (M=Cr, Ni, Co) is 500, the reaction temperature is 35 ℃, the reaction pressure is 0.5 MPa and the reaction time is 30 min, the catalytic activities for Si-Schiff-SiO2-Cr, Si-Schiff-SiO2-Ni and Si-Schiff-SiO2-Co in ethylene oligonerization are 1.92×105 g/(mol Cr·h), 2.17×105 g/(mol Ni·h) and 2.07×105 g/(mol Co·h), respectively, and the main oligomers are C4 and C6 olefin. Si-Schiff-SiO2-M has lower catalytic activity and narrower product distribution compared to the corresponding homogeneous catalyst due to the low loading of metal active center and the confinement effect of the support. Si-Schiff-SiO2-M has the good repeatability and the better thermal stability, and the activity of the recovered catalyst is up to 1.39×105 g/(mol Cr·h), 1.68×105 g/(mol Ni·h) and 1.42×105 g/(mol Co·h), respectively after three oligomerization reactions.

Key words: Ethylene oligomerization, Nano-silica, Heterogeneous catalyst, Covalent modification, Silylated-salicylaldimine

CLC Number: