Advancing Ziegler-Natta catalysis with internal donors

Abstract

Heterogeneous Ziegler-Natta catalysts are promising targets in rapidly growing polyolefin sector. The progressive developments in catalyst evolution are majorly attributed to the inclusion of internal donors for high productivity and improved stereospecificity. The catalyst performance in propylene polymerization is significantly affected by the structure of internal donors and their mode of interaction with MgCl₂ surface, and conformational arrangements at the vicinity of active Ti sites. Consequently, these donors play significant roles in controlling tacticity and MWD of polypropylene to further determine the critical polymer properties such as MFI, bulk density, crystallinity, flexibility, hardness, ductility etc. In this mini review, we have presented an overview of ZN catalyst system considering the mode of interactions of internal donors over MgCl₂ surface, comparative analysis of different classes of internal donors in terms of structure–activity relationship, rational design of new donors including bio-derived substrates, and salient features of industrial non-phthalate donors. The article concludes with dialogues over challenges and opportunities, and future outlook in the domain of new internal donors.