Storage time effect on dynamic structureof MgCl2.nEtOH adducts in heterogeneousZiegler-Natta catalysts

Primary MgCl programmed thermal dealcoholation process using a fluidized bed reactor. During thermal dealcoholation 2.3.3EtOH adduct (PCT1) was prepared by melt quenching method and then submitted into aprogram, different MgCl2.nEtOH support samples with n= 3.0, 2.7, 2.4, and 2.1 were selected and named as PCT2to PCT5, respectively. Structural analysis of the support samples, by moving from PCT1 to PCT5, showed asignifcant increase in the surface area from 7.4 m2/g to 12.8 m2/g, together with reduced peak heights at 2θ ≈ 8.9and 9.7°. After characterization of support samples, the fnal catalysts were prepared by reaction of the samples withTiCl4 and tested in slurry phase propylene polymerization. The prepared catalysts showed similar stereospecifcitiesbut different activities in polymerization tests, so that, with progression of dealcoholation from PCT1 to PCT2 thecatalyst activity was reached its maximum value of 2.9 kgPP/g Cat.h, and then by further dealcoholation, fromPCT2 to PCT5, the activity decreased gradually. In the last stage of the project, the effect of time interval betweenthermal dealcoholation and catalyst preparation, termed as storage time was studied on crystal and morphologicalcharacteristics of the two best adduct samples, namely MgCl2.2.4EtOH and MgCl2.3.0EtOH. The storage timegreatly affected the adducts and the resulting catalysts, and in this respect the best catalyst activity was achieved forthose prepared immediately after adduct formation. Polyolefns J (2014) 1:33-41

Keywords:

Ziegler-Natta , adduct , MgCl2 , thermal dealcoholation , polyolefn , dynamic structure