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.
Characterization
Mina Ahsani; Meisam Dabiri Havigh; Reza Yegani
Abstract
A polypropylene microporous membrane (PPMM) was fabricated by thermally induced phase separation (TIPS) method. The effects of protein size and structure as well as filtration pressure on the membrane performance and fouling mechanisms were investigated using two different proteins, bovine serum albumin ...
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A polypropylene microporous membrane (PPMM) was fabricated by thermally induced phase separation (TIPS) method. The effects of protein size and structure as well as filtration pressure on the membrane performance and fouling mechanisms were investigated using two different proteins, bovine serum albumin (BSA) and collagen, in dead-end filtration setup. Obtained results showed that, for each protein filtration, increasing the operational pressure led to higher irreversible fouling ratio (IFR) and consequently lower flux recovery (FR). Moreover, in collagen filtration, the higher portion of the total fouling ratio (TFR) belonged to reversible fouling ratio (RFR) and the FR of membrane in collagen solution filtration was higher than that in BSA solution filtration at the same operational pressure. The FR values were about 42.48 and 56.32% at 2 bar, 52.28 and 64.53% at 1.5 bar and 65.97 and 75.83% at 0.75 bar for BSA and collagen solutions filtrations, respectively. Investigation of the fouling mechanisms using Hermia's models showed that the cake filtration mechanism of fouling turned to pore blocking mechanism in both proteins filtrations by increasing the operational pressure. Obtained results using combined fouling models for all filtration processes confirmed that the cake filtration-standard blocking model (CFSBM) was the prevailing mechanism, whilst the contribution of standard blockage increased by increasing the operational pressure.
Catalysis
Feng He; Peiyuan Li; Anyang Wu; Tao Xu; Zhisheng Fu; Liang Zhu; Zhiqiang Fan
Abstract
In this paper, a series of well-defined polyethylene-b-polytetrafluoroethylene diblock copolymers (PE–b– PTFEs) were prepared by a coupling reaction of hydroxyl-terminated polyethylene (PE–OH) and isocyanateterminated 1H,1H-perfluoro-1-tetradecanol (PFDO–NCO). PE–OH was ...
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In this paper, a series of well-defined polyethylene-b-polytetrafluoroethylene diblock copolymers (PE–b– PTFEs) were prepared by a coupling reaction of hydroxyl-terminated polyethylene (PE–OH) and isocyanateterminated 1H,1H-perfluoro-1-tetradecanol (PFDO–NCO). PE–OH was prepared by the coordination chain transfer polymerization using 2,6-bis[1-(2,6-diisopropylphenyl)imino ethyl] pyridine iron (II) dichloride /dry ethylaluminoxane/ZnEt2 as catalyst and subsequent in situ oxidation with oxygen. PFDO–NCO was synthesized through the condensation reaction of 1H,1H- perfluoro-1-tetradecanol (PFDO) with isophoronediisocyanate (IPDI). Subsequently, the thermal characterization and the application of these diblock copolymers were investigated. The relationship between the molecular structure and the properties was disclosed. The results indicated that the diblock copolymers were effective surface modification agents for linear low density polyethylene (LLDPE). After that the PE–b–PTFE being spin-coated onto the surface of LLDPE film, the film was dramatically turned into a superhydrophobic film with a water contact angle as high as 151.4º. This kind of film is potential to be used as selfcleaning, anti-icing and anticorrosion material.
Ali Behboudi; Yoones Jafarzadeh; Reza Yegani; Ali Akbari
Abstract
Grinded glass fiber (GGF) embedded high density polyethylene (HDPE) membranes were prepared via thermally induced phase separation method. FESEM images showed that all the membranes had leafy structure, indicating a solid-liquid mechanism during phase separation. The results of EDX and TGA analyses confirmed ...
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Grinded glass fiber (GGF) embedded high density polyethylene (HDPE) membranes were prepared via thermally induced phase separation method. FESEM images showed that all the membranes had leafy structure, indicating a solid-liquid mechanism during phase separation. The results of EDX and TGA analyses confirmed that the fibers were dispersed in the HDPE matrix uniformly. Normalized water flux of the membranes increased from 1 for the neat HDPE membrane to more than 4 for 10 wt% GGF/HDPE membrane. Moreover, the contact angle decreased from 129° to 94° as the GGF content increased in the membranes, showing an improvement in the surface hydrophilicity of the membranes. The AFM results revealed that the surface roughness of the membranes was increased with increasing the GGF content. The results of abrasion test revealed that the GGF/HDPE membranes had a more abrasion resistance than the neat HDPE membrane. Finally, the fouling behavior of the membranes was investigated by the filtration of BSA protein solution and the results showed that with increasing the glass fiber content, total fouling ratio decreased from 90% for the neat HDPE membrane to 62% for 10 wt% GGF/HDPE membrane, indicating that the antifouling properties of the membranes were improved due to the presence of glass fiber.
Structure and property relationship
Somaye Akbari; Niloofar Eslahi; Mohammad Haghighat Kish
Abstract
The present study investigates the hydrophilic properties of acrylonitrile/acrylic acid P(AN/AA) copolymer films with various acrylic acid (AA) contents dendrigrafted with citric acid from zero to fourth generation numbers. It was found that the hydrophilicity of the dendrigrafted films was a complicated ...
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The present study investigates the hydrophilic properties of acrylonitrile/acrylic acid P(AN/AA) copolymer films with various acrylic acid (AA) contents dendrigrafted with citric acid from zero to fourth generation numbers. It was found that the hydrophilicity of the dendrigrafted films was a complicated phenomenon. Various parameters such as intermolecular hydrogen bonding, roughness and active functional groups affected the wettability of the film samples measured via static contact angle. The results revealed that the hydrophilicity decreased with increasing the generation number owing to the steric hindrance of terminal groups. However, active functional group increased by rising generation numbers which was confirmed using zeta potential measurement. Furthermore, the percentage conversion of the reactions showed a reduction with increasing generation number and AA content which was in agreement with the reduction in wettability corresponding to the higher contact angle. On the other hand, zeta potential as well as roughness of the films increased with successive generations.
Catalysis
Qiaoqiao Sun; Ruihua Cheng; Zhen Liu; Xuelian He; Ning Zhao; Boping Liu
Abstract
Chromium-vanadium (Cr-V) bimetallic catalysts are prepared by the introduction of vanadium into the Phillips catalyst which is one of the most significant industrial ethylene polymerization catalysts for tuning the Phillips catalyst performances and improving polyethylene properties. In the present work, ...
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Chromium-vanadium (Cr-V) bimetallic catalysts are prepared by the introduction of vanadium into the Phillips catalyst which is one of the most significant industrial ethylene polymerization catalysts for tuning the Phillips catalyst performances and improving polyethylene properties. In the present work, titanium species were introduced into the fluorine-modified chromium-vanadium bimetallic catalysts (Cr-V-F) and the prepared catalysts were systematically explored. The element content results of multi-component catalysts showed that a competitive inhibition interaction existed between chromium and vanadium, whereas chromium was more preferable to attach to the Ti-SiO2 than vanadium. In addition, ethylene homopolymerization and ethylene/1-hexene copolymerization were carried out and examined with different catalysts. The introduction of titanium into fluorine-modified bimetallic catalysts enhanced the molecular weight (MW) and broadened the molecular weight distribution (MWD) of polyethylene. The MW of the titanium- and fluorine-modified bimetallic catalysts (Cr-V-F/Ti) firstly rose up and then dropped down with the increasing of the Al/Cr molar ratio. The Cr-V-F/Ti catalysts showed slightly depressed hydrogen response and incorporation of 1-hexene. The short-chain branch distribution (SCBD) results, which were characterized by TREF/SSA, showed that the introduction of the titanium species increased the SCB content in low MW fractions and decreased the SCB content in the high Mw fractions of ethylene/1-hexene copolymers obtained from (Cr-V-F/3Ti)600 in contrast to that from (Cr-V-F)600.
Characterization
Setareh Heidari; Yoones Jafarzadeh; Mahdi Seyfollahi Samarin; Reza Yegani
Abstract
In this study, neat HDPE and HDPE/PE-g-MA/EVA blend membranes were fabricated via thermally induced phase separation (TIPS) method and their fouling behaviors were examined using filtration of BSA protein. Membranes were characterized using FESEM, AFM, ATR-FTIR analyses and porosity measurement. Fouling ...
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In this study, neat HDPE and HDPE/PE-g-MA/EVA blend membranes were fabricated via thermally induced phase separation (TIPS) method and their fouling behaviors were examined using filtration of BSA protein. Membranes were characterized using FESEM, AFM, ATR-FTIR analyses and porosity measurement. Fouling behavior of membranes was analyzed using the resistance-in-series (RIS), classic and combined pore blocking models. The results of RIS model revealed that the magnitude of inherent, reversible and irreversible resistances decreased from 0.611 ×1013m-1 and ,1.578 ×1013m-1 and 0.525 ×1013m-1 for the neat membrane to 0.237 ×1013m-1, 0.789 ×1013m-1 and 0.154×1013m-1 for the blend membrane, respectively. None of the classical Hermia’s models were able to accurately predict fouling during the entire filtration run. The results obtained from the combined pore blocking model indicated that the combined cake formation-intermediate blocking model provided good prediction of fouling mechanism for both the membranes. However, comparison between fitted parameters showed that much greater fouling occurred for pure HDPE membrane. The key reasons for such different fouling behaviors were mainly attributed to the difference in hydrophobicity as well as the distribution of pore size on the surface of the pure and blend membranes.
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 %.
