A STUDY OF SURFACE-CATALYZED POLYMERIZATION OF ETHYLENE ON CHROMIC OXIDE-SILICA-ALUMINA CATALYSTS

This investigation was an exploratory study of the phenomena associated with the polymerization of ethylene on a chromic oxide–silica–alumina catalyst. The polymerization was carried out in a batch reactor fed on demand at 500 psi gage and at 135°C. The catalyst was 3% chromic oxide on an 87% silica–13% alumina support, activated at 450°C for 5.25 hr in dry air. The catalyst particles were found to reduce in size during the polymerization. The particles decreased in size from 18/20 mesh to an average diameter of 9.6 μ. This reduction in particle size was found to cease at a yield of 40.0 g per gram of catalyst. By determining the monomer reaction rate versus time, the catalyst activity was found to change greatly during the polymerization. The activity increased to a maximum, then decreased. The period of increasing catalyst activity corresponded to the period of catalyst particle size reduction. The period of decreasing activity was considered to be due to the build‐up of a polymer film diffusion layer and true catalyst deactivation. The molecular weight distributions for a series of samples from each polymerization test were determined on gel permeation chromatograph. These distributions for each test were characterized by an increase in the high molecular weight tail as the yield increased, while the peak position and low molecular weight end remained essentially constant. Copyright © 1969 John Wiley & Sons, Inc.