Solvent-free preparation of well-dispersed and highly active CrOx/VOx/TiO2-SiO2 bimetallic catalyst for bimodal UHMWPE/ HDPE in-reactor blends

CrO x /VO x /TiO 2 -SiO 2 was prepared via solvent-free and conventional wet-impregnation process with ethanol as solvent. The results of ICP-OES, N 2 adsorption-desorption, SEM-EDX, Raman and DR-Uv-vis spectra indicate that well-dispersed Cr and V sites in isolated state were the main species. Bimodal ultra-high molecular weight polyethylene/high-density polyethylene in-reactor blends (UHMWPE/HDPE IRBs) could be synthesized with polymerization activity ＞ 1×10 7 gPE·mol −1 Cr·h −1 . Moreover, the two catalysts displayed similar catalytic behaviors in temperature sensitivity, H 2 response and 1-hexene copolymerization efficiency, and their polymer products also show comparable molecular weight and molecular weight distribution , which implies analogous structures of their well-dispersed active sites. By contrast, the catalyst prepared by wet-impregnation process with water as solvent exhibited poor dispersity, which is reflected by its much lower activity and very different catalytic behaviors and polymer properties when compared with the well-dispersed catalysts. Therefore, the economic and green solvent-free process is promising for preparing highly-active CrO x /VO x /TiO 2 -SiO 2 .