Sulfonated porous organic polymer supported Zeigler-Natta polypropylene catalysts with high stereoregularity and broad molecular weight distribution

Porous organic polymers (POPs) have received increasing attentions in a wide range of areas including adsorption, separation and catalysis. In this paper, a kind of sulfonated POP was designed, synthesized and used as Zeigler-Natta catalyst support for propylene polymerization. The prepared s-POP obtained highly porous structure with specific surface area of 542 m 2 /g (BET) and pore volume of 0.433 g/ml. The prepared s-POP based Zeigler-Natta catalysts with diisobutyl phthalate (ID-1) and 3-methyl-5-tert-butyl-1,2-phenylene dibenzoate (ID-2) exhibit good propylene polymerization activity, high stereoregularity and broad molecular weight distribution. The polymerization activity of Cat-2 with (ID-2) is 32.6 × 10 6  g.PP/mol.Ti. h with Mw/Mn of 13.8 and isotacticity index of 98.3%. The stereoregularity or isotactic sequence distribution of the prepared polypropylene (PP) was characterized by DSC、 13 CNMR and TREF techniques, and the results showed that the s-POP based catalyst (cat-2) with ID-2 obtained particularly higher isotatic sequence than the MgCl 2 -based Ziegler-Natta catalyst (cat-4) with the same internal donor. Pentad methyl sequence mmmm of PP-2 (94.1%) from cat-2 is 1.6% higher than that of PP-4 from cat-4, and the elution temperature of PP-2 (123.5 °C, 91%) is 1 °C higher than the isotactic fraction from PP-4 (122.5 °C, 87.2%). This characteristics of broad molecular weight and peculiar high stereoregularity of s-POP based catalyst could be attributed the modulation of chemical environment around Ti and Mg elements, and XPS analysis exhibited the minute difference of binding energy of Ti、Mg、C and O atoms. Furthermore, the plausible formation mechanism of active sites for the s-POP based Z-N catalyst was proposed.