Highly Selective Preparation of Low Carbon Olefins Over PAMAM Grafted Carbon Nanotubes Supported Nickel Catalyst
Polyamide amine(PAMAM)dendritic nickel catalyst(PAMAM-Cat)and PMAMA functionalized grafted carbon nanotubes supported nickel catalyst(CNT-PAMAM-Cat)were successfully synthesized,and these two catalysts were characterized by Fourier transforms infrared spectroscopy,X-ray diffraction and photoelectron spectroscopy.Moreover,the effects of temperature,co-catalyst dosage,pressure,and time on the preparation of low-carbon α-olefins by catalytic ethylene oligomerization were also systematically investigated.The results indicate that under the optimal polymerization conditions(temperature 25 ℃,Al/Ni molar ratio 500(PAMAM-Cat)and 700(CNT-PAMAM-Cat),pressure 0.7 MPa,time 0.5 h),the two catalysts exhibit excellent ethylene oligomerization activities(5.75 × 104 and 3.75 × 104 g/(mol Ni·h))and low-carbonα-olefin selectivity.After three times of reutilization,CNT-PAMAM-Cat activity remains unchanged.The grey correlation analysis shows that pressure is a key factor affecting ethylene oligomerization over the two catalysts to produce low-carbon α-olefins.
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