Simulation & Modeling
Mehrsa Emami; Farzin Hormozi; Hossein Abedini
Abstract
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 ...
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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.
Reaction engineering
Mehrsa Emami; Mahmoud Parvazinia; Hossein Abedini
Abstract
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 ...
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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.
Catalysis
Hossein Bordbar; Ali Akbar Yousefi; Hossein Abedini
Abstract
Titanium (Ti) is the ninth most abundant element on earth. The titanium mineral ores are widely distributed in different parts of the world. The two main ores of titanium include rutile (TiO2) and ilmenite (FeO.TiO2). It is aimed to provide the readers with an insight to the main processes currently ...
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Titanium (Ti) is the ninth most abundant element on earth. The titanium mineral ores are widely distributed in different parts of the world. The two main ores of titanium include rutile (TiO2) and ilmenite (FeO.TiO2). It is aimed to provide the readers with an insight to the main processes currently employed to extract and recover titanium tetrachloride (TiCl4) from different titanium ores. Due to the crucial importance of TiCl4 catalyst in the synthesis and polymerization of polyolefins, the present work examines the literature and developments made in the processing of ilmenite and rutile ores for the extraction of TiCl4. The attention has been paid to the chlorination processes and the main parameters affecting the recovery of TiCl4. Different approaches developed to date are reviewed. Different processes, reaction mechanisms and conditions as well as the kinetic models developed for extraction and purification of TiCl4 in fluidized bed reactors are also reviewed. A literature survey on the combined fluidized bed reactor systems developed for achieving a high-grade synthetic rutile via selective chlorination of low-grade titanium ores having high metal oxides content such as magnesium oxide (MgO) and calcium oxide (CaO) is also reported. Different strategies adopted to avoid agglomeration process during the extraction process are discussed too.
