Titania incorporation efficiency

It is well established that the presence of fluoride on a Cr/silica-titania catalyst increases its 1-hexene incorporation efficiency, and lowers the amount of very low-MW material [605]. Table 43 shows one example of this. Two catalysts, Cr/silica and Cr/silica-titania, were activated at 600 °C, with and without fluoride. These catalysts were tested for polymerization activity in the presence of 0.5 mol L 11-hexene. In the absence of titania, no difference was observed in the amount of 1-hexene incorporated into the polymer. However, Cr/silica-titania exhibited a major increase in 1-hexene incorporation when it contained fluoride. 

FIGURE 222 The enhanced incorporation efficiency of a-olefins produced in situ during polymerization at 82 °C is apparent here as lower polymer density for a given comonomer to ethylene concentration ratio in the reactor. Cr/silica-titania (A) air 650 °C (B) air 650 °C, CO 350 °C (C) catalyst B tested with 3 ppm of BEt3. 

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