Advances in High-Temperature Non-Metallocene Catalysts for Polyolefin Elastomers

Despite the great successes achieved by metallocene catalysts in high-value-added polyolefin elastomer, the challenging preparation conditions and undesirable high-temperature molecular weight capabilities have compromised the efficiency and cost of polyolefin in industrial production. Recently, non-metallocene catalysts have received considerable attention due to their high thermostability, especially when coordinated with early transition metals. This review provides an overview of these early transition metal non-metallocene catalysts, which are mainly composed of N,N'-, N,O-, and N,S-bidentate complexes and tridentate complexes. The structural characteristics, catalytic performance, advantages, and disadvantages of the relevant non-metallocene catalysts, as well as their applications, are discussed. Candidates for commercialization of non-metallocene catalysts are proposed-focusing on imine-enamine, amino-quinoline, and pyridine-imine catalysts-by comparing the successful industrialization cases of metallocene catalysts. Finally, the trend in the research on non-metallocene catalysts and the strategies to address the challenges limiting their commercialization are considered.