Intra‐ and Interparticle Heterogeneities in Solid Activators for Single‐Site Olefin Polymerization Catalysis as Revealed by Micro‐Spectroscopy

Abstract

Methylaluminoxane (MAO) is an activator for single-site olefin polymerization catalysts. Structural characterization of MAO, and in particular the influence of its heterogenization on a silica support, is pivotal for the understanding and optimization of this versatile co-catalyst. In this work, we demonstrate that by varying the MAO loading on a silica support, we can tune the single particle characteristics in terms of MAO distribution and consequent activity. At low MAO loading we reveal two possible intraparticle MAO distributions: a homogeneous and an Al-shell type distribution. With increasing MAO loading, the interparticle MAO distribution becomes more homogeneous. Acidity probing measurements on the single particle level explain how a different intraparticle MAO distribution results in a different activity in metallocene activation. Al-shell particles contain remaining silanol groups and a negligible amount of acid sites and are, therefore, considered inactive for metallocene activation. Only the solid activator particles with a homogeneous intraparticle MAO distribution contain a sufficient number of acid sites, capable of activating the deposited metallocenes.

Single Particle Assays to Determine Heterogeneities within Fluid Catalytic Cracking Catalysts

“…The large spread in zeolite content is most probably due to the used spray drying technique and again highlights the importance of a method that can perform diagnostics on many single particles: bulk methods cannot give enough information on a sample as complex as an FCC ECAT material. This characterization method can be extended to other systems with a large inter‐particle heterogeneous catalysts, such as olefin polymerization catalysts or metal (oxide) impregnated support oxides …”

“…This characterization method can be extended to other systems with al arge inter-particle heterogeneous catalysts, such as olefin poly- merization catalysts or metal (oxide) impregnated support oxides. [19,31]…”

“…and try to further correlate the single particle mapping data on ECAT fractions sorted by a classical density separation. We have previously reported such a correlation to reveal interparticle heterogeneities in polymerization catalysts . We use these correlations to identify relationships as well as special FCC catalyst particles.…”

“…We have previously reported such acorrelation to revealinterparticle heterogeneities in polymerizationc atalysts. [19] We use these correlationst oi dentify relationshipsa sw ell as special FCC catalyst particles.…”

Physicochemical surface-structure studies of highly active zirconocene polymerisation catalysts on solid polymethylaluminoxane activating supports

“…Furthermore, inert carrier supports possess -OH groups which provide a pathway for complex deactivation. 32,38 Comparison of the [Al sMAO ] 0 /[Zr] 0 data for chloride and methide complexes with the same Cp R ligands, Cp 2 ZrX 2 and Me 2 Si(C 5 H 4 ) 2 ZrX 2 (X = Cl, Me), reveals that both chloride and methide leaving groups result in nearquantitative complex immobilisation. However, the sMAO-Cp 2 ZrX 2 catalysts derived from metallocenes with aryl and aryloxide s-donor groups (X = Ph, C 6 F 5 , OC 6 F 5 ) show slightly higher [Al sMAO ] 0 /[Zr] 0 values, suggesting the larger leaving group limits the extent of complex immobilisation under these conditions.…”