Heterogeneous Ziegler–Natta catalysts with various sizes of MgCl2 crystallites: synthesis and characterization

Genesis of MgCl2‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy

“…Also in this case the first spectrum is dominated by the spectroscopic manifestations of the pure alcohol, whereas the last spectrum presents only a few bands due to residual ethoxy byproducts, whose formation has already been assessed in literature. [58,59,94,95] The slightly different evolution of the two alcoholate precursors may explain the different properties of the produced MgCl 2 , in terms of specific surface area, particles size and morphology.…”

Particle morphology and morphogenesis of nascent polyethylene produced with a spherical MgCl2‐supported Ziegler–Natta catalyst in slurry process

“…Judging by the submicron size of the knots and very high polymer/catalyst weight ratio (>1500), the primary catalyst particle (aggregation of MgCl 2 crystallites with adsorbed TiCl 4 ) forming a knot should be smaller than 100 nm. This size roughly falls in the size range of experimentally observed primary particles of MgCl 2 ‐supported Ziegler–Natta catalysts . Because of separations between the primary particles, each primary particle tends to form a single nodular structure.…”

“…The most widely applied industry catalysts for polyolefin production are spherical or nearly spherical granules with size ranging from several micrometers to 50 μm. The particles of MgCl 2 ‐supported Ziegler–Natta catalyst usually have complicated multilevel textures owing to different kinds of packing of their primary building‐blocks, nanosized crystallites of MgCl 2 that carry adsorbed TiCl 4 . In high activity catalyst particles there are numerous evenly distributed tiny pores and cracks, which act as the passages for monomer diffusion to the surfaces of most crystallites.…”

Kinetics of short‐duration ethylene–propylene copolymerization with MgCl2‐supported Ziegler–Natta catalyst: Differentiation of active centers on the external and internal surfaces of the catalyst particles

“…[41][42][43][44] Because each catalyst particle is composed of aggregations of MgCl 2 crystallites (the primary particles) of nanometer size, 45 a high proportion of Ti species adsorbed on the crystallites may become inaccessible to TiCl 4 in the repeated treatments of TiCl 4 /MgCl 2 particles with TiCl 4 , as some surfaces of the MgCl 2 crystallites carrying TiCl 4 may be closely attached with each other to reduce surface energy. [41][42][43][44] Because each catalyst particle is composed of aggregations of MgCl 2 crystallites (the primary particles) of nanometer size, 45 a high proportion of Ti species adsorbed on the crystallites may become inaccessible to TiCl 4 in the repeated treatments of TiCl 4 /MgCl 2 particles with TiCl 4 , as some surfaces of the MgCl 2 crystallites carrying TiCl 4 may be closely attached with each other to reduce surface energy.…”