The influence of porosity on the Phillips Cr/silica catalyst 2. Polyethylene elasticity

Abstract

The Phillips Cr/silica catalyst produces low levels of long chain branching (LCB) in polyethylene, which have a powerful influence on industrial molding behavior. Although many catalyst and reactor variables determine the degree of LCB, perhaps the most significant of these is the morphology of the silica support. In this study many different types of silicas were converted into Cr/silica catalysts, which were tested in ethylene polymerization, and the resultant polymer elasticity was then determined. In some experiments, the surface area of the catalyst seemed to correlate quite well with polymer elasticity. In other tests, however, no connection with surface area was evident but the pore volume was quite influential. Together, all these studies suggest that it is the degree of structural reinforcement of the silica matrix, rather than any one physical measurement of porosity, that influences elasticity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 845–865, 2009

A Novel SiO2‐Supported Fluorine Modified Chromium–Vanadium Bimetallic Catalyst for Ethylene Polymerization and Ethylene/1‐Hexene Copolymerization

“…The porosity of support affects the microstructure and properties of the polyethylene products . The results of the surface area and pore structure parameters determined by nitrogen adsorption/desorption experiments are collected in Table .…”

Comprehensive Investigation of Catalyst Structure and Polymerization Conditions for Chain Branching in Ethylene Polymerization with Phillips‐Type Catalysts

“…Recently, McDaniel and Collins reported that the LCB formation is relevant to the local active site concentration. They also found a tendency that a higher LCB content is correlated with a larger pore volume of a catalyst 4…”

Morphological modifications of Cr/SBA-15 and Cr/Al-SBA-15 ethylene polymerization catalysts: Influence on catalytic behaviour and polymer properties

“…with an inorganic or organometallic chromium compound, followed by calcination at high temperature (500-1000°C) to produce Cr(VI) active species [2][3][4]. Nowadays, it is well known that physicochemical properties of the solid supports play an important role on the resulting properties of the polyethylene produced [2,3,[5][6][7]. In this sense, morphological properties of the catalytic support are particularly important since they determine the size and shape of polymer particles due to the fragmentation and replica phenomena produced during the polymerization [2].…”