Catalyst Testing for the BP Chemicals Gas Phase Process

Abstract

BP Chemicals has operated its commercial gas phase ethylene polymerisation process since 1975 and has licensed the process world wide. The process operates at pressures of about 20 bars and temperatures of about 100°C. Catalysts for use in this process must be tailored to obtain the desired products. The key parameters to be controlled are: 1. the catalyst activity, 2. its kinetic profile, 3. its ability to incorporate comonomers, 4. the catalyst and polymer morphology, 5. the polymer average molecular weight and 6. the polymer molecular weight distribution. In this paper we describe the methods used to screen the suitability of catalysts for the BP Chemicals Gas Phase Process. In the laboratory we use small stirred batch reactors. At this small scale effective fluidised bed technology is difficult to achieve and is not necessary. Other techniques used include powder characterisation (flow behaviour, particle size measurements, bulk density and shape factor determination, mechanical strength measurement, etc.), chemical analysis, polymer characterisation (molecular weight and molecular weight distribution, density, rheology, chain branching level and distribution, etc.). Finally, we present the main factors affecting the properties of the polymers and the process parameters which can be varied to influence them.