Retrofitting of industrial olefin polymerization plants: producing broad MWDs through multiobjective periodic operation

Abstract

The drop-in of metallocene catalysts (MCs) in existing industrial polymerization plants is the current goal of most polymer producers. However, the narrow molecular weight distribution (MWD) of the polymers produced by MCs prevent them of moving into commodities market dominated by conventional Ziegler-Natta catalysts, where ease of processing is an essential property. Broader MWDs may be obtained through mixing of different MCs or blending of different resins, but resin-compatibility problems and complex undesirable catalyst interactions pose technological problems that have yet to be solved. For these reasons, modern olefin polymerization plants have to work with both catalysts to respond to market demands, resulting in costly operations of grade/catalyst change. In this article, we describe how periodic control of short residence-time reactors operating with an MC (Me 2 Si(2-Me-Benz[e]Ind) 2 ZrCl 2 /MAO) can lead to polymers with broad MWD and, consequently, to high processability.