Storage time effect on dynamic structure of MgCl2 nEtOH adducts in heterogeneous. Ziegler-Natta catalysts

Primary MgCl2.3.3EtOH adduct (PCT1) was prepared by melt quenching method and then submitted into a programmed thermal dealcoholation process using a fluidized bed reactor. During thermal dealcoholation program, different MgCl2.nEtOH support samples with n= 3.0, 2.7, 2.4, and 2.1 were selected and named as PCT2 to PCT5, respectively. Structural analysis of the support samples, by moving from PCT1 to PCT5, showed a significant increase in the surface area from 7.4 m2/g to 12.8 m2/g, together with reduced peak heights at 2? ? 8.9 and 9.7°. After characterization of support samples, the final catalysts were prepared by reaction of the samples with TiCl4 and tested in slurry phase propylene polymerization. The prepared catalysts showed similar stereospecificities but different activities in polymerization tests, so that, with progression of dealcoholation from PCT1 to PCT2 the catalyst activity was reached its maximum value of 2.9 kgPP/g Cat.h, and then by further dealcoholation, from PCT2 to PCT5, the activity decreased gradually. In the last stage of the project, the effect of time interval between thermal dealcoholation and catalyst preparation, termed as "storage time" was studied on crystal and morphological characteristics of the two best adduct samples, namely MgCl2.2.4EtOH and MgCl2.3.0EtOH. The storage time greatly affected the adducts and the resulting catalysts, and in this respect the best catalyst activity was achieved for those prepared immediately after adduct formation.