ABSTRACT
In the mid-1950s a series of patents on a new ethylene polymer was issued. These patents were all similar in that solid catalysts were used to produce polyethylene at relatively low ethylene pressures. The Phillips catalysts are generally prepared from an amorphous silica gel and CrO3. The use of Ziegler catalysts to produce polyethylene initially grew at a much slower pace than the chromium oxide on silica catalysts. Catalysts prepared by reacting magnesium alkyls and titanium compounds started appearing in the late 1960s and have continued into the 1970s. The phrase "high activity catalyst," in regard to transition metal olefin polymerization catalysts, has been abused and often times misused. The advantages of highly active catalysts have been greatly overstated. The new generations of olefin polymerization catalysts generated a lot of excitement initially. However, to be a viable commercial alternative to the established catalysts, they will have to demonstrate better polymer properties as well as cost savings.
