Authors Grönke, M. ; Arrozi, U.S.F. ; Bronkalla, N. ; Schmidt, P. ; Valldor, M. ; Oswald, S. ; Woodcock, T.G. ; Eckert, V. ; Hao, Q. ; Plüschke, L. ; Lederer, A. ; Nielsch, K. ; Buchner, B. ; Kaskel, S. ; Hampel, S.
Title Layered alpha-TiCl3: Microsheets on YSZ substrates for ethylene polymerization with enhanced activity
Date 21.09.2019
Number 57025
Abstract The transition metal halide alpha-titanium(III) chloride (alpha-TiCl3) is a layered two-dimensional compound and a well-established Ziegler-Natta catalyst for the polymerization of ethylene. A new synthesis technique is used to obtain thin sheets of alpha-TiCl3 that show exceptional physical properties in contrast to their bulk counterparts, due to an enlarged surface-to-volume ratio. Chemical vapor transport (CVT) of alpha-titanium(III) chloride directly on substrates results in microsheets that exhibit an improved catalytic effect. For rational planning of synthesis conditions, thermodynamic simulations of occurring gas-phase equilibria were performed. Based on these calculation results, crystal growth was achieved by adding GaCl3 via pure short term CVT in a temperature gradient of 700-600 K on yttrium-stabilized zirconia (YSZ) substrates. Phase pure, as-grown, single crystal sheets with high crystallinity and a thickness of around 4 mu m were obtained. These thin sheets of alpha-TiCl3 on YSZ substrates were implemented as catalysts for the ethylene polymerization reaction. A significant improvement of catalytic activity of 16% was achieved, probably due to an increased surface-to-volume ratio. As a highlight, the as-grown microsheets were exfoliated subsequently to a thickness lower than 200 nm and an even higher catalytic activity of up to 24% was confirmed experimentally due to delamination effects. This is the first time that an improved catalytic effect of alpha-TiCl3 is observed as a result of downscaling from bulk to microsheets by CVT.
Publisher Chemistry of Materials
Wikidata Q105198862
Citation Chemistry of Materials 31 (2019) 5305-5313

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