Some reflections on the current state of Cr-based polymerization catalysts

The state of Phillips Cr/silica catalyst technology is discussed in this article, including recent advances in the science and also economic and environmental challenges to its continued viability. Although these catalysts have often been described as mature, many new innovations have been introduced in the past decade that reduce cost, improve quality, and expand the range of products that can be made. Polymers having unusually high, and low, levels of long-chain branching have been introduced. Several advances in the control of the short-chain branch distribution have also been made. Ways to lower the catalyst costs have been successfully implemented, such that Phillips-type catalysts are still the least expensive in the industry. Finally, new chromium-containing hybrid catalysts have been made that marry attributes from single-site and conventional Cr oxide catalysts.