Effects of catalyst particle design on polyolefin synthesis using supported metallocene catalyst

A practical problem in gas-phase olefin polymerization is the formation of polymer sheets due to localized particle overheating. Optical and infrared imaging was used to study the effects of reaction temperature, feed composition, initial particle size, and catalyst particle distribution on the temporal temperature and the polymerization reaction rate. Infrared imaging showed that the maximum particle temperature is reached within 20 seconds of reaction initiation. A maximum particle temperature rise of 17 °C is observed. Clustering of particles creates the most significant increase in the initial particle temperature rise, thus creating the conditions most conducive to particle melting and sheet formation.; A kinetic model which accounts for the initiation, propagation and deactivation reactions is used to predict the impact of the kinetic parameters, catalyst loading and residence time in the reactor on the maximum productivity attained while preventing particle overheating. The maximum productivity decreases with an increase of the deactivation reaction modulus and is an increasing function of the propagation reaction modulus. The residence time at which the maximum productivity is attained, tm, depends m most strongly on the moduli for the initiation reaction and the deactivation reaction. The maximum productivity is rather insensitive to an increase of the residence time above tm. The processabiltiy of various polyolefins may be enhanced by using a dual-site catalyst to produce one having a bimodal molecular weight distribution. We show here how to utilize kinetic information about the two catalytic sites to predict the optimum loading of dual-site metallocene catalysts.