Gas phase polymerization of Propylene was carried out in a semi-batch minireactor using a commercially supported Ziegler– Natta (ZN) catalyst. The influence of variables including monomer partial pressure, external electron donor, reaction temperature and time on the particle morphology and size distribution was investigated. Generally, more uniform fragmentation and particle densities were obtained at lower reaction rates. Monomer partial pressure showed a significant role of particle size and its distribution, the higher the monomer partial pressure, the broader particle size distribution was obtained. polymerization pressure had a significant role on the morphology of particles. Wider cracks and more porosity were resulted from the polymerizations at higher pressures. Furthermore, a broader particle size distribution was obtained from the polymerization at higher pressures. The particle size analysis revealed the monomer partial pressure as the most effective parameter on the distribution of particles. The SEM images showed that three different steps could be distinguished in the development of particle morphology within the particle, showing the initiation and development of cracks and appearance of fragments inside the particle.

Bulk phase polymerization of Propylene with a 4th generation of Ziegler-Natta catalyst was kinetically investigated by means of heat flow calorimetry. The assumptions and modifications on isothermal calorimetric method were demonstrated. Our calibration method showed that heat exchange with the reactor cover plate is not constant over time. Therefore, the dynamic of cover plate temperature was considered in the calorimetric method. The polymerization rate profiles depending on hydrogen and external electron donor concentration have been investigated. Normalized polymerization profiles (Rp/Rpmax) are plotted and expressed as an exponential function of time. Effects of hydrogen and external electron donor (ED) concentration on Rpmax and polymerization rate were investigated as well. The results showed that by increasing hydrogen concentration, initial polymerization rate (Rpmax) increased. Hydrogen increased productivity by increasing the initial polymerization rate, while it had no negative effect on the rates of decay or its effect was small. The ED concentration was optimized so that the catalyst deactivation rate was at its lowest level. Also, changes in the ratio of activation to inactivation with ED concentration were examined, and a proportional change was observed

Hydrogen in spite of having a chain transfer agent role is one of the most important factors which directly affecting on kinetic of Propylene polymerization. Hydrogen causes to dramatically increase the percentage of activated sites in proportion to being total potential sites on the catalyst surface. On the other hand, the chain transfer agent role of hydrogen gives rise to changing some vital indices of final product properties. This study has attempted to present a validated mathematical model that able to predicting profile polymerization rate and also calculating some of the vital indices of the final product, properties to be derived from kinetic equations. Furthermore, in this paper, we present a developed model that calculates fraction activated sites catalyst via hydrogen concentration based on dormant site theory and determining the best process condition. The modeling approach is based on the polymer moment balance method, i. e. population balance technique and validated by experimental works. The main aim of this study is assigned to investigate the behavior change of polymerization rate to hydrogen. The experimental data and model outputs were compared and concluded that the global errors were in the acceptable range.

Spray-dry granulation of clay minerals was studied to obtain clay mineral base support material for metallocene supported olefin polymerization catalysts. The morphology of the granules was strongly influenced by the nature of the clay mineral itself. Because of swelling characteristics of montmorillonite, its water dispersion was highly viscous even in the low slurry concentration (<4 wt %). Therefore, it was very difficult to control the granule characteristics such as size, shape, and inside structure by the spray drying of the clay mineral slurry. Then we examined some methods in order to change the clay mineral surface properties for getting less viscous dispersion. It was found that the milling of montmorillonite increased the amount of surface OH groups. This surface characteristic change should promote the interaction between the edges and basal planes of the primary particles of milled montmorillonite, resulting in the lowering the slurry viscosity. The milling is effective for overcoming difficulty in use of high concentration montmorillonite slurry in spray-dry granulation which is indispensable for producing granules in the wide range of size (10-50 mm). The spray-dried montmorillonite granules are useful as a "support-activator" for an olefin polymerization catalyst combined with metallocenes.

In this study we have tested the ability of a standard DFT computational protocol to reproduce the experimentally obtained stereoselectivity of 26 different C2-symmetric zirconocene catalysts active in Propylene polymerization. The catalysts were chosen for their relevance in metallocene catalyzed polymerization of Propylene. To this end, primary insertion of both si - and re -Propylene enantiofaces into the Zr-CH2-CH (CH3) 2 bond was considered to simulate the growing chains step. The energy difference between these two transition states, DE re-si, was taken as a measure of the stereoselectivity (pentad: mmmm%) of different catalysts. The results clearly indicated that there was a good agreement between DE re-si and the mmmm% values, so that greater DE re-si could correspond to higher mmmm%. A model was fitted to the experimentally obtained mmmm% against theoretical DE re-si. The coefficient of determination (R2) of the resultant plot was 0.9793, which indicated a good accuracy of the model. Finally, to quantify the steric role of the studied ligands in the observed stereoselectivity, the analysis of the buried volume (VBur) and of the steric maps was performed for two representative complexes. The images revealed that a greater asymmetric localization of the %VBur around the metal center led to a higher mmmm% in the resultant polymer.

Different chemical components in traditional Ziegler–Natta catalytic system include: (1) titanium and vanadium containing compounds, mostly TiCl4, as an active centre, (2) trialkylaluminium-based Lewis acid compounds, especially triethylaluminium, as precatalyst and alkylating agent, and (3) inorganic compounds, specifically MgCl2 and silica, as catalyst supports. Besides these compounds, shortly after the first discovery of Ziegler-Natta catalysts, electron donors have been considered as the key components for MgCl2-supported Ziegler-Natta catalysts, as they improve the stereospecificity and activity of these types of catalysts. Most electron donor compounds have oxygen atom and only a few contain nitrogen atom in their structure. Starting from benzoate for third-generation Ziegler–Natta catalysts, the discovery of new donors has always updated the performance of Ziegler–Natta catalysts. Since the first discovery of these compounds numerous efforts have been devoted in both industry and academic laboratories, not only to discover new electron donors but also to understand their roles in Ziegler–Natta olefin polymerization and suitable MgCl2-alcohol adducts formation. This article reviews the history of such research and development efforts. The first part of the article describes the historical developments of catalyst, with a special focus on donors of industrial importance, followed by an account given on recent trends in the latest donors developed. The next part of the article covers the historical progress toward mechanistic understanding of how donors improve the performance of Ziegler–Natta catalysts and how they undergo decomposition by interaction with Lewis acidic species such as the AlEt3 and TiCl4.

Several types of hybrid catalysts are made through mixing of 4th generation Ziegler-Natta (ZN) and (2-PhInd) 2ZrCl2 metallocene catalysts using triethylaluminum (TEA) as coupling agent. Response surface methodology (RSM) is used to evaluate the interactive effects of different parameters including amounts of metallocene and TEA and temperature on metallocene loading. Analyzing the amounts of Al and Zr elements in the hybrid catalysts through ICP-OES and EDXA reveals that temperature plays a crucial role on anchoring of the metallocene catalyst on ZN while TEA has the least determining effect. The ICP analysis shows that as the concentration of Al goes up in the hybrid catalyst the concentration of Zr passes a maximum, while EDXA shows a direct relationship between the Al and Zr contents. Using triisobutylaluminum (TIBA) and methylaluminoxane (MAO) as the coupling agents, almost similar metallocene loadings are observed. Finally, the performance of hybrid catalysts is investigated in Propylene polymerization and the obtained polymers are characterized using DSC and DMTA through which the presence of two types of polymers in the final product are confirmed.