Olefin polymerization and copolymerization
Mohsen Javaheri; Mehdi Nekoomanesh; Yousef Jahani
Abstract
The concentration of ethylene and 1-butene in n-hexane as polymerization media was calculated at five different pressure levels (4, 6, 8, 10, and 12 bar) and four different 1-butene concentrations (0.13, 0.26, 0.39, and 0.52 mol/L) in n-hexane at T= 80°C using the Peng-Robinson thermodynamic equation ...
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The concentration of ethylene and 1-butene in n-hexane as polymerization media was calculated at five different pressure levels (4, 6, 8, 10, and 12 bar) and four different 1-butene concentrations (0.13, 0.26, 0.39, and 0.52 mol/L) in n-hexane at T= 80°C using the Peng-Robinson thermodynamic equation of state. Some combinations of conditions were selected to perform the copolymerization reaction in the presence of an industrial TiCl4/MgCl2 Ziegler-Natta catalyst. The forms of the synthesized products were visually and qualitatively classified as either powder or sticky. The percentage of incorporated 1-butene comonomer into the polyethylene chains was analyzed using calibrated FTIR tests. It was shown that for ethylene/1-butene concentration ratios (β) in n-hexane above approximately 1.80, the product forms as a powder. For values below 1.30 threshold, the product was sticky. Thus, this ratio could be used as a criterion for selecting the proper combination of copolymerization pressure and 1-butene concentration when aiming to achieve a powdered form of the product. It was shown that β has a strong correlation with the weight percentage of 1-butene in the final LLDPE polymer. Therefore it can be used as an accurate prediction for wt.% of incorporated 1-butene into the LLDPE chain within the studied concentration ranges with the specific catalyst system utilized.
Mehdi Nekoomanesh
Abstract
Editorial Notes
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Editorial Notes
Olefin polymerization and copolymerization
Aliasghar Mahdavi Akerdi; Mehdi Nekoomanesh
Abstract
The condition of oligo-micelle formation of sodium di-isodecyl sulfosuccinate (SDIDS) emulsifier in hydroalcoholic solutions is used to study particle formation of vinyl chloride emulsion polymerization in a batch reactor. The change on micellization behavior was investigated by critical micelle concentration ...
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The condition of oligo-micelle formation of sodium di-isodecyl sulfosuccinate (SDIDS) emulsifier in hydroalcoholic solutions is used to study particle formation of vinyl chloride emulsion polymerization in a batch reactor. The change on micellization behavior was investigated by critical micelle concentration (CMC) and zeta potential parameters. To detect the occurrence of secondary nucleation or particle aggregation, or both the particle size and number of particles were investigated as a criterion for the particle nucleation and growth process. The results showed that the alcohol (co-solvent) content had a strong effect on the oligo-micelles formation and emulsion polymerization performance. Namely, decreasing the alcohol content and increasing the anion content in the SDIDS samples increased the overall reaction rate and latex stability. This also decreased the chain growth rate, the particle size, and the coarse particle formation. Also, the results showed that different condition of oligo-micelle formation would lead to different particle growth history
Polyolefin degradation
Abbas Kebritchi; Mehdi Nekoomanesh; Fereidoun Mohammadi; Hossein Khonakdar; Udo Wagenknecht
Abstract
In this work, the effect of hexyl branch content on thermal behavior of a fractionated ethylene/1-octene copolymer with emphasis on high temperatures was investigated. The ethylene/1-octene copolymer was carefully fractionated to different fractions with homogenous hexyl branch (HB) content by preparative ...
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In this work, the effect of hexyl branch content on thermal behavior of a fractionated ethylene/1-octene copolymer with emphasis on high temperatures was investigated. The ethylene/1-octene copolymer was carefully fractionated to different fractions with homogenous hexyl branch (HB) content by preparative temperature rising elution fractionation (P-TREF) method. The P-TREF fractions were thermally analyzed via differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and evolved gas analysis (EGA). The P-TREF profile showed a short chain branch distribution (SCBD) of around 1.24. A linear relationship between P-TREF elution temperature (ET) and methylene sequence length (MSL) was presented. The DSC curves exhibited a monolithically increase in melting temperature (Tm) as well as crystallization temperature (Tc) by decreasing short chain branch (SCB) content. The calculated values of lamellae thickness suggested a linear function of SCB content and Tm. The TGA studies of P-TREF fractions depicted a two-stage thermal degradation behavior: pre-degradation and main degradation stages. Tmax for both pre-degradation and main degradation stages was increased for fractions with less hexyl branch content. As an interesting point the pre-degradation stage was found more intensified for more linear fractions. The concentration of main products was found to be affected by the content of hexyl branches using Py-GC-MS.
Structure and property relationship
Shokoufeh Hakim; Mehdi Nekoomanesh; Ali Shahrokhinia
Abstract
Three polypropylene samples (1-3) were synthesized with a 4th generation Ziegler-Natta catalyst in the presence of cyclohexyldimethoxymethylsilane (donor c), dicyclopenthyldimethoxysilane (donor d) and diisopropyldimethoxysilane (donor p), respectively, as external electron donors. The physical properties ...
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Three polypropylene samples (1-3) were synthesized with a 4th generation Ziegler-Natta catalyst in the presence of cyclohexyldimethoxymethylsilane (donor c), dicyclopenthyldimethoxysilane (donor d) and diisopropyldimethoxysilane (donor p), respectively, as external electron donors. The physical properties of the synthesized polypropylenes were determined. For samples 1 to 3, Successive self-nucleation and annealing (SSA) and Fourier transform infrared spectroscopy (FT-IR) analyses indicated that the relative content of the fraction with high isotacticity and regularity in conformational structure decreased in contrast with the fraction of low isotacticity and low uniformity in stereo-defect distribution from sample 1 to 3. The results demonstrated that the longer the isotactic sequence length and the less uniform the stereo-defect distribution, the greater the conformational order. Deconvolution of the molecular weight distribution curves indicated that the stability of the active centers increased from samples 1 to 3, but the participation of stereo-specefic active centers in the polymerization decreased. DMA tests showed that samples 3 and 1 had the highest damping ability and storage modulus, respectively.
Polyolefin degradation
Zaher Tamri; Ali Vaziri Yazdi; Mehdi Nekoomanesh Haghighi; Mehrdad Seifali Abbas-Abadi; Amir Heidarinasab
Abstract
Pyrolysis of high impact polystyrene (HIPS) waste has been investigated under different process parameters, such as temperature, heating rate and types of zeolitic catalysts to produce valuable liquid products. Liquid, gas and coke as products of pyrolysis and aromatic, naphthene, olefin and paraffin ...
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Pyrolysis of high impact polystyrene (HIPS) waste has been investigated under different process parameters, such as temperature, heating rate and types of zeolitic catalysts to produce valuable liquid products. Liquid, gas and coke as products of pyrolysis and aromatic, naphthene, olefin and paraffin as liquid components were obtained and their molecular weight distributions were studied with changing the process parameters in a stirred reactor. Aromatic-rich hydrocarbons within the gasoline range were the main pyrolysis products. Type of zeolitic catalysts, temperature and heating rate had significant effects on the products quality and quantity. Non-isothermal mass losses of high impact polystyrene were measured using a thermo-gravimetric analyzer (TGA) at heating rates of 5, 15, 30, 45 and 90°C min-1 until the furnace wall temperature reached 600°C. The DTG (differential thermal gravimetric) curves showed that heating rate had no obvious effect on the degradation trends in the studied range, and by increasing heating rate, the activation energies were decreased obviously from 222.5 to183.6 kJ mol-1.
Catalysis
Alikhani Ali; Shokoufeh Hakim; Mehdi Nekoomanesh
Abstract
This study presents methods for treating a kind of nanoclay and investigates the effects of methylaluminoxane (MAO) exposure time and or dodecylamine (DDA) reflux time on in-situ polymerization of ethylene in the presence of nanoclay and examines the morphology and properties of the prepared polyethylene/clay ...
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This study presents methods for treating a kind of nanoclay and investigates the effects of methylaluminoxane (MAO) exposure time and or dodecylamine (DDA) reflux time on in-situ polymerization of ethylene in the presence of nanoclay and examines the morphology and properties of the prepared polyethylene/clay nanocomposites. The results revealed that by increasing MAO exposure time productivity decreased. Modification of nanoclay by NH3/MAO led to formation of exfoliated structures. In treatment with NH3/DDA, the change in reflux time resulted in different structures. SEM demonstrated that the morphology of the nanocomposites strongly depended on the modification method and treatment time. Dynamic mechanical analysis indicated that the elastic modulus of the nanocomposites increased by increasing MAO exposure time. The nanocomposites treated with different MAO exposure times showed similar thermal degradation behavior. The nanocomposite modified under the condition of 24 h DDA reflux time indicated the lowest thermal decomposition temperature due to poor dispersion of nanoclay in the synthesized nanocomposite. The nanocomposites modified by NH3/MAO had higher degree of crystallinity compared to those modified by NH3/DDA, which could be attributed to the difference in dispersion level of the modified clays. A relationship between the rheological properties, weight fraction and dispersion of modified nanoclay was observed. The findings showed that the modification condition had a significant influence on the morphology and properties of the synthesized nanocomposites.
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
Gholam-Reza Nejabat; Mehdi Nekoomanesh; Hassan Arabi; Hamid Salehi-Mobarakeh; Gholam-Hossein Zohuri; Mohammad-Mahdi Mortazavi; Saeid Ahmadjo; Stephen A. Miller
Abstract
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 ...
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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.
Polyolefin degradation
Mehrdad Seifali Abbas-Abadi; Mehdi Nekoomanesh Haghighi; Armando G. McDonald; Hamid Yeganeh
Abstract
Pyrolysis of low density polyethylene (LDPE) by equilibrium fluid catalytic cracking (FCC) was studied in a stirred reactor under different process parameters. In this work, the effect of process parameters such as degradation temperature (420-510°C), catalyst/polymer ratio (0-60%), carrier gas type ...
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Pyrolysis of low density polyethylene (LDPE) by equilibrium fluid catalytic cracking (FCC) was studied in a stirred reactor under different process parameters. In this work, the effect of process parameters such as degradation temperature (420-510°C), catalyst/polymer ratio (0-60%), carrier gas type (H2, N2, ethylene, propylene, Ar and He), residence time and agitator speed (0-300 rpm) on the condensate yield (liquid, gas and coke) and product composition were considered. Reaction products were determined by GC analysis and shown to contain naphthenes (cycloalkanes), paraffins (alkanes), olefins (alkenes) and aromatics. Higher temperature and more catalyst amount enhanced LDPE cracking. The maximum “fuel like” condensed product yield was attained at 450°C and 10% catalyst, respectively and gaseous products increased with increases in temperature. Hydrogen as a reactive carrier gas increased the condensed and paraffinic product yield. Appropriate heat transfer (by stirring) increased the catalyst efficiency in a stirred reactor.
Polyolefin degradation
Abbas Kebritchi; Mehdi Nekoomanesh; Fereidoon Mohammadi; Hossein Ali Khonakdar
Abstract
In this work, the role of comonomer content of 1-hexene-medium density polyethylene (MDPE) copolymer, synthesized using Phillips catalyst, on thermal behavior parameters such as: crystallization, melting temperature and thermal degradation was investigated in detail. The copolymer was fractionated to ...
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In this work, the role of comonomer content of 1-hexene-medium density polyethylene (MDPE) copolymer, synthesized using Phillips catalyst, on thermal behavior parameters such as: crystallization, melting temperature and thermal degradation was investigated in detail. The copolymer was fractionated to homogenous short-chain branching (SCB) fractions by "preparative temperature rising elution fractionation" (P-TREF) method and then it was subjected to thermal analyses. A broad chemical composition distribution (CCD) in terms of SCB content and molecular weight (Mw) was observed by P-TREF and gel permeation chromatography (GPC), respectively. Based on P-TREF results, a parabolic relationship between methylene sequence length (MSL) and elution temperature (ET) was presented. Differential scanning calorimetry (DSC) showed distinct, well-defined melting peaks over a 22 °C temperature range for SCB contents of about 3-12 (br/1000 C). The variations in physical characteristics such as melting temperature (Tm), crystallinity (Xc), crystallization temperature (Tc) and lamellae thickness (Lc) against SCB content were correlated. Thermogravimetric analysis (TGA) suggested linear relationships between the temperature at maximum degradation rate (Tmax) as well as the degradation initiation temperature (T5%) versus SCB content. Moreover, the TGA curves exhibited distinct differences at both initiation and propagation stages of thermal degradation at dissimilar comonomer contents.
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.
