Anchoring Via Covalent Binding Of Schiff Base Transition Metal In Nanometer Materials For Catalyzing Ethylene Oligomerization

Series of the complex transition metal catalysts based on Schiff base imine and a novel Cr?III?-PNP catalyst were synthesized using 3-aminopropyl triethoxysilane as the bridging group and with salicylaldehyde,chlorinated diphenylphosphine and transition metal compounds as materials.Series of transition metal catalyst based on Schiff base imine covalently modified nanomaterial and a novel modified nanomaterial-supported Cr?III?-PNP catalyst were synthesized.Fourier transform infrared spectrum?FT-IR?,X-ray diffraction?XRD?,nuclear magnetic hydrogen spectroscopy?¹H-NMR?,X-ray photoelectron spectroscopy?XPS?,thermogravimetric analysis?TGA?,scanning electron microscope?SEM?,energy dispersive X-ray spectroscopy?EDX?and other characterization methods were used to prove that the structures of the synthesized ligands and catalysts were consistent with their theoretical structures and the loading amount of active center on the carrier.On the basis of synthesis and characterization,the performance of Schiff base imine complexed nickel???catalyst for ethylene oligomerization was studied.The effects of polymerization reaction system and polymerization conditions on the activity of ethylene oligomerization and product distribution were investigated.The experimental results showed that when MAO was used as the cocatalyst and cyclohexane was used as the solvent,the complex transition metal catalyst based on Schiff base imine had good performance in ethylene oligomerization.And the optimal reaction conditions were as follows:Al/Ni molar ratio was 500,reaction temperature was 25?,pressure of ethylene was 0.1 MPa,and reaction time was 30min.The activity of the complex nickel???catalyst based on Schiff base imine was up to 7.40×10⁵g/?mol Ni·h?,and the selectivity to C₆ and C₈ was 38.03%.Under the optimal reaction conditions,the complex cobalt???catalyst based on Schiff base imine had the catalytic activity was 5.62×10⁵g/?mol Ni·h?,and the selectivity to C₆ and C₈ was 32.99%.Based on the research on the performance of nickel???complex based on Schiff base imine covalently modified nanomaterial to catalyze ethylene oligomerization,the effects of the polymerization reaction system and polymerizationconditions on its catalytic activity and product distribution of ethylene oligomerization were investigated in detail.The optimal reaction conditions for nickel???complex based on Schiff base imine covalently modified nanomaterial to catalyze ethylene oligomerization were as follows:cyclohexane was solvent,MAO was cocatalyst,Al/Ni molar ratio was 700,reaction temperature was 25?,the ethylene pressure was 0.1 MPa and the reaction time was 30 minutes.Under the conditions,the activity of the nickel???complex based on Schiff base imine covalently modified nanomaterial could reach 58.50×10⁵ g/?mol Ni·h?.The selectivity to C₆ and C₈ was 97.99%.After three recycling experiments,the activity of nickel???complex based on Schiff base imine covalently modified nanomaterial could still reach 52.70×10⁵g/?mol Ni·h?,which proved that nickel???complex based on Schiff base imine covalently modified nanomaterial had good stability and reusability.Based on the systematic study of nickel???complex based on Schiff base imine covalently modified nanomaterial in ethylene oligomerization,a novel modified nanomaterial-supported Cr?III?-PNP catalyst was used to catalyze ethylene oligomerization.When MAO was used as the cocatalyst and cyclohexane was used as the solvent,a novel modified nanomaterial-supported Cr?III?-PNP catalyst catalyzed the ethylene oligomerization.The preferred reaction conditions were as follows:cyclohexane was solvent,MAO was the cocatalyst,and Al/Cr mole ratio was 700,the amount of the main catalyst was 3?mol,the reaction temperature was 25?,the reaction pressure was 0.5 MPa,and the reaction time was 30 min.Under the conditions,this novel modified nanomaterial-supported Cr?III?-PNP catalyst had an activity of 1.03×10⁵ g/?mol Cr·h?and a selectivity to C₈⁺ of 81.63%.