title: Unraveling the Catalytic Synergy between Ti(3+) and Al(3+) Sites on a Chlorinated Al2 O3 : A Tandem Approach to Branched Polyethylene.
abstract: An original step-by-step approach to synthesize and characterize a bifunctional heterogeneous catalyst consisting of isolated Ti(3+) centers and strong Lewis acid Al(3+) sites on the surface of a chlorinated alumina has been devised. A wide range of physicochemical and spectroscopic techniques were employed to demonstrate that the two sites, in close proximity, act in a concerted fashion to synergistically boost the conversion of ethylene into branched polyethylene, using ethylene as the only feed and without any activator. The coordinatively unsaturated Al(3+) ions promote ethylene oligomerization through a carbocationic mechanism and activate the Ti(3+) sites for the traditional ethylene coordination polymerization.
authors.affiliation: Department of Chemistry-INSTM and NIS Centre, University of Torino, via Giuria 7, 10125, Torino, Italy.
authors.forename: Alessandro
authors.identifier: 0000-0002-5784-6897
authors.initials: A
authors.lastname: Piovano
authors.affiliation: Department of Chemistry-INSTM and NIS Centre, University of Torino, via Giuria 7, 10125, Torino, Italy.
authors.forename: K S
authors.initials: KS
authors.lastname: Thushara
authors.affiliation: Department of Chemistry-INSTM and NIS Centre, University of Torino, via Giuria 7, 10125, Torino, Italy.
authors.forename: Elena
authors.identifier: 0000-0002-4044-5720
authors.initials: E
authors.lastname: Morra
authors.affiliation: Department of Chemistry-INSTM and NIS Centre, University of Torino, via Giuria 7, 10125, Torino, Italy.
authors.forename: Mario
authors.identifier: 0000-0001-8128-8031
authors.initials: M
authors.lastname: Chiesa
authors.affiliation: Department of Chemistry-INSTM and NIS Centre, University of Torino, via Giuria 7, 10125, Torino, Italy. elena.groppo@unito.it.
authors.forename: Elena
authors.identifier: 0000-0003-4153-5709
authors.initials: E
authors.lastname: Groppo
keywords: EPR spectroscopy; Ti3+ sites; Ziegler-Natta catalysts; operando FT-IR spectroscopy; tandem catalysis