Olefin oligomerization
Ahad Hanifpour; Mahdi Hashemzadeh Gargari; Mohammad Reza Rostami Darounkola; Zahra Kalantari; Naeimeh Bahri-Laleh
Abstract
Herein a quenched-flow kinetic technique was applied to calculate the rate constants of 1-hexene and 1-octene oligomerization catalyzed by the Cp2ZrCl2 and Cp2HfCl2/MAO catalyst systems, and subsequently a mechanism for the higher α-olefin oligomerization reaction was proposed. The oligomerization ...
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Herein a quenched-flow kinetic technique was applied to calculate the rate constants of 1-hexene and 1-octene oligomerization catalyzed by the Cp2ZrCl2 and Cp2HfCl2/MAO catalyst systems, and subsequently a mechanism for the higher α-olefin oligomerization reaction was proposed. The oligomerization results showed that Zr-based catalyst in the oligomerization of 1-octene had the highest activity of 17 in comparison to Hfbased one with an activity value of 15 g oligomer/(mmolCat.h)). According to the obtained results, increasing monomer length led to a shift in molecular weight and polydispersity index value (Mw/Mn) to lower values. Furthermore, the microstructure-viscosity relationship was followed by the calculation of branching ratio and short-chain branching percentage. The obtained results revealed that, the oligomers synthesized by the Cp2HfCl2 catalyst had lower short chain branching ratio value and short-chain branching percentages. According to the kinetic results, the initiation rate constant (ki) of Zr-based catalyst was higher than that of Hf-based catalyst, and the order of calculated propagation rate constants was Zr>Hf for both the 1-hexene and 1-octene-based oligomerizations.
Catalysis
Farshid Nouri-Ahangarani; Mehdi Nekoomanesh; Seyed Amin Mirmohammadi; Naeimeh Bahri-Laleh
Abstract
The aim of this study was to examine the effect of catalyst doping on the performance of MgCl2. EtOH/TiCl4 catalyst system. In this regard, a series of undoped as well as FeCl3-doped catalysts was prepared and employed in 1-hexene polymerization. A modified catalyst containing 10 wt. % of FeCl3 dopant ...
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The aim of this study was to examine the effect of catalyst doping on the performance of MgCl2. EtOH/TiCl4 catalyst system. In this regard, a series of undoped as well as FeCl3-doped catalysts was prepared and employed in 1-hexene polymerization. A modified catalyst containing 10 wt. % of FeCl3 dopant demonstrated the highest activity, with 32% activity increase compared to unmodified one, among the series. The GPC results showed a lower molecular weight as well as broader MWD for the poly1-hexenes obtained from FeCl3-doped catalyst. The distribution of active centers was analyzed using deconvolution of the MW profiles with using multiple Flory functions. It was demonstrated that the number of active sites increased by 10 wt. % FeCl3 doping, however, by more increasing the dopant amount to 15 wt.%, the number of active sites decreased. The 13C-NMR results indicated that, FeCl3 doping did not have a considerable effect on the polymer tacticity (with total tacticity of 53 %), however it increased by donor presence to the maximum value of 60 %.
Polyolefins Industry
Naeimeh Bahri-Laleh; Mehdi Nekoomanesh-Haghighi; Samahe Sadjadi; Ali Pajouhan
Abstract
Due to easy availability of cheaper raw material and increase in new applications, the use of polyolefins in various industries is becoming a major priority. The Middle East region, on account of its vast oil and gas reserves has, in the last decade or so, been developing many new petrochemical complexes ...
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Due to easy availability of cheaper raw material and increase in new applications, the use of polyolefins in various industries is becoming a major priority. The Middle East region, on account of its vast oil and gas reserves has, in the last decade or so, been developing many new petrochemical complexes with their expansion into colossal polyolefin production capacities. The predictions are that by 2020 the Middle East region will dominate the polyolefin industry as a whole. Furthermore, with proven oil reserves of about 21.7 thousand million tons (4th world ranking) and natural gas of 34.0 trillion cubic meters (1st world ranking), Iran’s petrochemical industry is supported by diverse and abundant feedstock reserves. In line with other polyolefin producers’ developments in the Middle East, Iran's National Petrochemical Company (NPC) has undergone massive structural and technological transformations in the last two decades in order to set up ambitious plans for further capacity increase and native technology developments. This article mainly focuses on Iran today’s position and its future plans in the polyolefins industry.
Catalysis
Najmeh Hadian; Shokoofeh Hakim; Mehdi Nekoomanesh-Haghighi; Naeimeh bahri-Laleh
Abstract
Primary MgCl2.3.3EtOH adduct (PCT1) was prepared by melt quenching method and then submitted into a programmed thermal dealcoholation project 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 ...
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Primary MgCl2.3.3EtOH adduct (PCT1) was prepared by melt quenching method and then submitted into a programmed thermal dealcoholation project 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 showed a significant increase in the surface area, from 7.4 m2/g to 12.8 m2/g, together with the decrease in peaks height at 2θ≈ 8.9 and 9.7˚ by moving from PCT1 to PCT5. After characterization of support samples, final catalysts were prepared by reacting these samples with TiCl4 and examined in slurry phase propylene polymerization. Prepared catalysts showed similar stereospecifities but different activities in the polymerization experiments, so that, with proceeding dealcoholation from PCT1 to PCT2 catalyst activity was reached a maximum amount of 2.9 kgPP/g Cat.h, and then by further dealcoholation, from PCT2 to PCT5, catalyst activity decreased gradually. In the last section, effect of time interval between thermal dealcoholation and catalyst preparation, which is called storage time, on the crystal and morphological characteristics of the two of the best adduct samples, namely MgCl2.2.4EtOH and MgCl2.3.0EtOH, was studied, as well. Storage time greatly affected the characteristics of the adducts together with resulted catalysts, and the best catalyst activity was achieved for the ones prepared immediately after adduct preparation.
