Remarkable Promotion Effect of Sulfation over the SiO2-Supported Vanadium-Oxide-Based Catalysts for UHMWPE

The effects of sulfation on VO x /SiO 2 –MO y (M = Al, Zr, or Ti) are systemically studied for the synthesis of ultrahigh molecular weight polyethylene (UHMWPE), showing that the activity remains stable under the investigated polymerization temperature ( T p ) from 70 to 90 °C, and is almost doubled after sulfation. According to the results of NH 3 –TPD, pyridine-adsorption-fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), the enhancement effect in activity is likely related to the promoted acidity of the catalysts and the increased electron deficiency of the V center. Remarkable cocatalyst dependence is found and has the priority of diethylaluminum chloride (DEAC) > ethylaluminum sesquichloride > triisobutylaluminum > triethylaluminum, and the highest activity of 5200 kg PE mol −1 V could be obtained with DEAC as cocatalyst. The viscosity average molecular weight ( M v ) of the PEs can be regulated from 3 to 5 × 10 6 g mol −1 by decreasing T p from 90 to 70 °C. Based on the results of differential scanning calorimetry (DSC) annealing experiments, highly entangled UHMWPE is produced.