In situ copolymerization of ethylene to produce linear low‐density polyethylene by Ti(OBu)4/AlEt3‐MAO/SiO2/Et(Ind)2ZrCl2

Linear low‐density polyethylene (LLDPE) is produced in a reactor from single ethylene feed by combining Ti(OBu)₄/AlEt₃, capable of forming α‐olefins (predominantly 1‐butene), with SiO₂‐supported Et(Ind)₂ZrCl₂ (denoted MAO/SiO₂/Et(Ind)₂ZrCl₂), which is able to copolymerize ethylene and 1‐butene in situ with little interference in the dual‐functional catalytic system. The two catalysts in the dual‐functional catalytic system match well because of the employment of triethylaluminum (AlEt₃) as the single cocatalyst to both Ti(OBu)₄ and MAO/SiO₂/Et(Ind)₂ZrCl₂, exhibiting high polymerization activity and improved properties of the obtained polyethylene. There is a noticeable increment in catalytic activity when the amount of Ti(OBu)₄ in the reactor increases and 1‐butene can be incorporated by about 6.51 mol % in the backbone of polyethylene chains at the highest Ti(OBu)₄ concentration in the feed. The molecular weights (M_w), melting points, and crystallinity of the LLDPE descend as the amount of Ti(OBu)₄ decreases, which is attributed mainly to chain termination and high branching degree, while the molecular weight distribution remains within a narrow range as in the case of metallocene catalysts. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2451–2455, 2004     

Ti alkoxide-based catalyst system in selective ethylene dimerization: High performance through modifying by alkylsilanes

Butene-1 production through a selective ethylene dimerization is one of the largest industrial processes, which is catalyzed by homogeneous catalyst system. The common industrial catalyst system is comprised of Ti alkoxide-based catalysts in combination with AlEt₃ as an activator. In this study, the alkylsilanes were used as novel improving agents in the catalyst system for highly selective ethylene dimerization to butene-1. The nature and concentration of alkylsilanes on the dimerization rate, catalyst yield, by-product production, and selectivity to butene-1 were investigated in detail. It was found that alkylsilanes improved the productivity and selectivity of the catalyst. Moreover, the content of the solid by-product considerably decreased. The performance of the modified catalyst system was noticeably higher than that of the nonmodified one. Totally, it was proved that alkylsilanes could play a modifying role in the selective ethylene catalytic dimerization process.     

New clay‐supported Ziegler–Natta catalyst for preparation of PE/Clay nanocomposites via in situ polymerization

Polyethylene/clay (PE/Clay) nanocomposites were prepared by the in situ polymerization of ethylene using the new Clay/butyl octyl magnesium (BOM)/Chloroform/EtOH/TiCl₄/tri ethyl aluminum (TEA) catalyst system in heptane where BOM and TEA were the support for the clay modification and cocatalyst, respectively. The influence of the modified clay using BOM on the catalyst and polymerization was investigated. Also, the effect of temperature, pressure, hydrogen, and the molar ratios of TEA/Ti on the catalyst yield and ethylene consumption (polymerization rate) were studied. It was found that the above clay‐supported catalyst was an efficient Ziegler–Natta type catalyst due to its suitable yield for the polymerization of ethylene toward the production of the PE/Clay nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Kinetic study of a highly active MgCl2‐supported Ziegler–Natta catalyst in liquid pool propylene polymerization. II. The influence of alkyl aluminum and alkoxysilane on catalyst activation and deactivation

The influence of alkyl aluminum and alkoxysilane on the kinetics in liquid pool propylene batch polymerization was investigated with a highly active Ziegler–Natta catalyst system that consisted of MgCl₂/TiCl₄/diester–alkoxysilane/AlR₃. In this study, diethyl phthalate and t‐BuEtSi(OMe)₂ were used as a diester and an alkoxysilane, respectively. The catalyst activity depended on the concentration of the alkyl aluminum when it came into contact with the catalyst. In addition, alkoxysilane as an external donor had a role in activating the catalyst. With respect to activity decay, the overreduction of Ti did not seem to be the cause. Instead, the decay rate decreased with an increasing alkoxysilane/catalyst ratio. This implied that activity decay was caused by the formation of dormant sites after 2,1‐misinsertion of propylene. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2669–2679, 2002     

Effect of cocatalysts on ethylene polymerization with fluorinated bisphenoxyimine titanium as a catalyst

In this study, we examined various alkylaluminums, including triethylaluminum (TEA), triisobutylaluminum (TIBA), and diethylaluminum chloride (DEAC), as cocatalysts for the activation of ethylene polymerizations in the presence of a fluorinated Fujita group invented titanium (FI‐Ti) catalyst, bis[N‐(3‐tert‐butylsalicylidene)‐2,3,4,5,6‐pentafluoroanilinato] titanium(IV) dichloride (complex 1 ). DEAC, because of the strong Lewis acidity, was an efficient cocatalyst for activating complex 1 for the ethylene polymerizations, whereas TEA and TIBA as cocatalysts could hardly polymerize ethylene. The effects of the polymerization temperature and Al/Ti molar ratio on the formation of active species, properties, and molecular weight of the resulting polyethylene were investigated. In the complex 1 /DEAC catalyst system, the oxidation states of Ti active species were determined by electron paramagnetic resonance. The results demonstrated that Ti(IV) active species were inclined to polymerize ethylene and yielded high‐molecular‐weight polyethylene. Comparatively, Ti(III) active species resulted from the reduction of Ti(IV) by DEAC and afforded oligomers. Moreover, the bigger steric bulk for the cocatalysts was necessary to achieve ethylene living polymerization with the fluorinated FI‐Ti catalyst. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Copolymerization of ethylene–propylene using high‐activity bi‐supported Ziegler–Natta TiCl4 catalyst

Heterogeneous Ziegler–Natta TiCl₄ catalyst using MgCl₂ and SiO₂ as supports was prepared under controlled conditions. Mg(OEt)₂ was used as a starting material and was expected to convert to active MgCl₂ during catalyst preparation. Due to the high surface area and good morphological control, SiO₂ was chosen as well. Slurry copolymerization of ethylene and propylene (EPM) was carried out in dry n‐heptane by using the catalyst system SiO₂/MgCl₂/TiCl₄/EB/TiBA or TEA/MPT/H₂ at temperatures of 40–70°C, different molar ratios of alkyl aluminum : MPT : Ti, hydrogen concentrations, and relative and total monomers pressure. Titanium content of the catalyst was 2.96% and surface area of the catalyst was 78 m²/g. Triisobutyl aluminum (TiBA) and triethyl aluminum (TEA) were used as cocatalysts, while ethyl benzoate (EB) and methyl p‐toluate (MPT) were used as internal and external donors, respectively. H₂ was used as a chain‐transfer agent. Good‐quality ethylene propylene rubber (EPR) of rubber was obtained at the ratio of [TiBA] : [MPT] : [Ti] = 320 : 16 : 1 and polymerization temperature was 60°C. When TiBA was used as a cocatalyst, a higher and more rubberlike copolymer was obtained. For both of the cocatalysts, an optimum ratio of Al/Ti was obtained relative to the catalyst productivity. Ethylene content of the copolymer obtained increased with increasing TiBA concentration, while inverse results were obtained by using TEA. Addition of H₂ increased the reactivity of the catalyst. The highest product was obtained when 150 mL H₂/L solvent was used. Increasing temperature from 40 to 70°C decreased the productivity of the catalyst, while irregular behavior was observed on ethylene content. Relative pressure of P_P/P_E = 1.4 : 1 and total pressure of 1 atm was the best condition for the copolymerization. Polymers with ethylene contents of 25–84% were obtained. Increasing ethylene content of EPR decreased T_g of the polymer obtained to a limiting value. Viscosity‐average molecular weight (M_v) decreased with increasing temperature and TiBA and H₂ concentration. However, increasing the polymerization time increased the M_v. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2597–2605, 2004     

Continuous Gas‐Phase Hydroformylation of 1‐Butene using Supported Ionic Liquid Phase (SILP) Catalysts

The concept of supported ionic liquid phase (SILP) catalysis has been extended to 1‐butene hydroformylation. A rhodium‐sulfoxantphos complex was dissolved in [BMIM][n‐C₈H₁₇OSO₃] and this solution was highly dispersed on silica. Continuous gas‐phase experiments in a fixed‐bed reactor revealed these SILP catalysts to be highly active, selective and long‐term stable. Kinetic data have been acquired by variation of temperature, pressure, syngas composition, substrate and catalyst concentration. A linear dependency in rhodium concentration could be established over a large concentration range giving another excellent hint for truly homogeneous catalysis in the SILP system. Compared to former studies using propene, the SILP system showed significantly higher activity and selectivity with 1‐butene as feedstock. These findings could be elucidated by solubility measurements using a magnetic microbalance.     

Organically modified inorganic sol‐gel materials for second‐order nonlinear optics

A series of the organically modified inorganic NLO sol‐gel materials based on the prepolymer of alkoxysilanes and an alkoxysilane dye (ASD) have been investigated. Optically clear samples exhibit large second‐order optical nonlinearity (d₃₃ = ∼10.8–54.0 pm/V at 1064 nm) after poling and curing at 220°C for 1 h. The thermal behavior of these NLO sol‐gel materials was studied by temperature‐dependent dielectric relaxation. The results indicate that the crosslinking density of cured NLO sol‐gel materials was increased with increasing alkoxysilane content. Subsequently, better temporal stabilities were obtained for the poled/cured NLO sol‐gel materials with a higher alkoxysilane content. Moreover, the structural influence of alkoxysilanes on the thermal behavior and second‐order nonlinearity was also studied for these NLO sol‐gel materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1852–1859, 2001     

Effective modification of Pd surfaces with TiO2 promoters using selective chemical vapor deposition and the effect on catalytic performance improvement

In this paper, we describe a novel method for selectively attaching TiO₂ promoters on Pd surfaces in Pd/SiO₂ catalysts using selective chemical vapor deposition (CVD). Ti was selectively deposited on Pd active sites over a SiO₂ support under a hydrogen atmosphere when titanium tetraisopropoxide was used as a Ti precursor. The Pd–Ti/SiO₂ catalyst modified by CVD exhibits approximately 1.8 times higher ethylene selectivity than the un-modified Pd/SiO₂ catalyst in the selective hydrogenation of acetylene due to the effective geometric modification of the Pd surface, which is beneficial to ethylene selectivity, by the selectively deposited Ti species.     

Mechanism and kinetics of esterification of adipic acid and ethylene glycol by tetrabutyl titanate catalyst

An eight-step mechanism of esterification reaction between adipic acid (AA) and ethylene glycol (EG) catalyzed by tetrabutyl titanate [Ti(OBu)₄] was studied in detail. The kinetic data for the esterification reaction between AA and EG catalyzed by tetrabutyl titanate [Ti(OBu)₄] were measured in the temperature range of 403 K-433 K. A second-order kinetic model was established, and the model parameters were obtained through an optimization procedure by minimizing the value differences between the simulated component concentrations in the reaction system with the experimental ones. The results demonstrate that the model is suitable for the esterification reaction between AA and EG catalyzed by tetrabutyl titanate [Ti(OBu)₄]. Furthermore, the esterification reaction rate increases with the increase of reaction temperature, concentration of catalyst and the initial reactant ratio of EG to AA.     

Epoxidation of a Series of C2–C6 Olefins in the Gas Phase

Epoxidation of ethylene, propylene, 2‐methylpropene, trans‐2‐butene, 2‐methyl‐2‐butene, and 2,3‐dimethyl‐2‐butene were carried out in a flow‐through reactor in the homogeneous gas phase at pressures of 0.25–1.0 bar in the temperature range of 250–375 °C. Residence times in the reactor varied from 8.3 to 38 ms. The oxidizing agent needed in the feed gas is ozone. The O₃ efficiency (reacted olefin/initial O₃) was found to be strongly dependent on the reactivity of the olefin used. For C₄–C₆ olefins, the O₃ efficiency was better than 75 % in each case. For 2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene, the O₃ efficiency exceeded the theoretical value of 100 % considerably. The selectivity to epoxide was about 90 % independent of the olefin used. Under conditions of nearly total olefin conversion, the high selectivity to the epoxide has been retained as unchanged. There were no indications for consecutive reactions of the epoxides.     

Simultaneous multi-objective optimization of a new promoted ethylene dimerization catalyst using grey relational analysis and entropy measurement

A hybrid approach between the Taguchi method and grey relational analysis (GRA) with entropy measurement was applied to determine a single optimum setting for reaction factors of the proposed ethylene dimerization catalyst having overall selectivity to 1-butene (S_1-btn (%)) and turnover frequency (TOF (h^-1)) as multiple quality characteristics. Titanium tetrabutoxide (Ti(OC₄H₉)₄) catalyst precursor in combination with triethyl aluminum (TEA) activator, 1,4-dioxane as a suitable modifier, and ethylene dichloride (EDC) as a novel promoter were used in the catalysis. Control factors of temperature, pressure, Al/Ti, 1,4-dioxane/Ti, and EDC/Ti mol ratios were investigated on three levels and their main effects were discussed. The effect of the binary interaction between temperature, pressure, and Al/Ti mol ratio was also examined. Weight of the responses was determined using entropy. Analysis of variance (ANOVA) for data obtained from GRA indicated that EDC/Ti mol ratio with 27.64% contribution had the most profound effect on the multiple quality characteristics. Development of the weighted Grey-Taguchi method used the Taguchi method as its basic structure, adopted GRA to deal with multiple responses, and entropy to enhance the reasonability of the comprehensive index produced by GRA to make the results more objective and accurate. Overall, these combined mathematical techniques improved catalytic performance for 1-butene production.     

Dimerization of 1‐butene via zirconium‐based Ziegler–Natta catalyst

A zirconium‐based Ziegler–Natta catalytic system has been tested in the dimerization of 1‐butene. It was found that the concentration of Et₂AlCl, Ph₃P and PhONa as well as the reaction temperature had great influences on the activity and selectivity of the catalyst. Under the optimum reaction conditions, the conversion of 1‐butene is 91.9%, and the selectivity of dimers is 76.7%. Basic ligands such as Ph₃P and PhONa can inhibit isomerization of 1‐butene to 2‐butene effectively. In addition, the metal hydride mechanism was also suggested and some indirect evidence was obtained in favor of this mechanism. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of blending time and catalyst on the properties of nylon 1010/acrylate rubber blends

Nylon 1010 and acrylate rubber (ACM) were prepared by melt blending. The effects of blending time and catalyst on the properties of the blends were studied. It was found that ester‐amide exchange reactions between the Nylon 1010 and ACM occurred during melt processing. Long blending time and Tetrabutyl titanate (Ti(OBu)₄) as a catalyst could promote the reactions, and grafted copolymer Nylon‐g‐ACM was in situ generated as a compatibilizer during processing procedure. The tensile strength of the blends increased from about 12.0–15.0 MPa when the blending time increased from 10 to 30 min. The presence of Ti(OBu)₄ led to the decrease in melt flow index (MFI), independent of the blending time (30 or 60 min). Glass transition temperature and heat of fusion of the blends increased after addition of the catalyst. Rheological behavior analysis provided evidence of formation of Nylon‐g‐ACM graft copolymer. Scanning electron microscopy (SEM) showed that the compatibility of the blends was improved by longer blending time and the addition of catalyst. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4587–4597, 2013     

Preparation of porous spherical MgCl2/SiO2 complex support as precursor for catalytic propylene polymerization

The MgCl₂/SiO₂ complex support was prepared by spray drying using alcoholic suspension, which contained MgCl₂ and SiO₂. The complex support reacted with TiCl₄ and di‐n‐butyl phthalate, giving a catalyst for propylene polymerization. The catalyst was spherical and porous with high specific surface area. TEA was used as a cocatalyst, and four kinds of alkoxysilane were used as external donors. The bulk polymerization of propylene was studied with the catalyst system. The effect of the reaction conditions and external donor on the polymerization were investigated. The results showed that the catalyst had high activity, high stereospecificity, and sensitive hydrogen responsibility. Polypropylene has good grain morphology because of duplicating the morphology of the catalyst. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1296–1299, 2005     

A Model Study of Ti(OBu)4 Catalyzed Reactions during Reactive Blending of Polyethylene (PE) and Poly(ethylene terephthalate) (PET)

Summary: The effect of metal catalysts in promoting the formation of the comb copolymer between a very low density polyethylene (VLDPE) grafted with diethyl maleate and PET has been studied in this paper following a model study based on low molecular weight molecules resembling the local structure of the reactive groups in the reference macromolecules. Ti(OBu)₄ was used as the catalyst and the reactions were carried out under the same conditions as in the case of the macromolecules species. The model mixtures have been analyzed by FT‐IR, ¹H and ¹³C NMR spectroscopy, thermogravimetric analysis (TGA) and GC‐MS and evidence of the degradation of ester bonds, deactivation of hydroxyl terminals of PET and the possible crosslinking of functionalized polyolefin have been observed. The molecular model process agrees with results obtained for the macromolecular system blending PET and VLDPE grafted with diethyl maleate in a Brabender mixer in the presence of Ti(OBu)₄, as evaluated by mixer torque values and selective extraction results. Therefore, the present model study allows us to both obtain information about reaction mechanism in the complex melt biphasic system and to suggest new strategies to optimize the process.

Brabender torque/time graphics of PET in presence of different amounts of Ti(OBu)₄.     

Oxidative dehydrogenation of butenes over Bi‐Mo and Mo‐V based catalysts in a two‐zone fluidized bed reactor

The oxidative dehydrogenation of a 1‐butene/trans‐butene (1:1) mixture to 1,3‐butadiene was carried out in a two‐zone fluidized bed reactor using a Mo‐V‐MgO and a γ‐Bi₂MoO₆ catalyst. The significant operating conditions temperature, oxygen/butene molar ratio, butene inlet height, and flow velocity were varied to gain high 1,3‐butadiene selectivity and yield. Furthermore, axial concentration profiles were measured inside the fluidized bed to gain insight into the reaction network in the two zones. For optimized conditions and with a suitable catalyst, the two‐zone fluidized bed reactor makes catalyst regeneration and catalytic reaction possible in a single vessel. In the lower part of the fluidized bed, the oxidation of coke deposits on the catalyst as well as the filling of oxygen vacancies in the lattice can occur. The oxidative dehydrogenation reaction takes place in the upper zone. Thorough particle mixing inside fluidized beds causes permanent particle exchange between both zones. © 2016 American Institute of Chemical Engineers AIChE J, 63: 43–50, 2017     

Highly active Ziegler–Natta catalyst for propylene polymerization

Polymerization of propylene was carried out by using a MgCl₂–EtOH–TiCl₄–ID–TEA–ED catalyst system in n‐heptane, where ID (internal donor) was an organic diester, ED (external donor) was a silane compound, and TEA (triethyl aluminum) was the activator. The influences of temperature, pressure, time, hydrogen, and the molar ratios of Al/Ti and ED/Ti on polymer isotacticity and catalyst activity were studied by solubility in boiling n‐heptane and measuring the polymer produced, respectively. The morphology of the polymers was evaluated through scanning electron microscopy and particle size distribution. The rheological properties of the poly(propylene) were determined by the melt flow index. It was found that the catalyst showed good morphology and high activity and also the produced polymers were characterized by high isotacticity and globulelike shapes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1744–1749, 2005     

Preparation of novel titania supported palladium catalysts for selective hydrogenation of acetylene to ethylene

Novel titania supports have been designed and elaborated with the hydrolysis precipitation method, by adjusting and controlling of the main preparation parameters, such as pH value, adding rate of tetrabutyl titanate Ti(OBu)₄, and calcining temperature of precursor during support preparation. The new titania supported Pd catalysts were prepared and investigated for selective hydrogenation of acetylene to ethylene. The catalyst samples have been characterized by temperature programmed reduction (TPR), XRD and BET techniques. The experimental results indicated that with MgO modification, the improved catalyst (0.5%Pd–MgO/TiO₂) showed better performance of high and stable activity.     

Comonomer enhancement effect of 1-hexene in ethylene copolymerization catalyzed over MgCl2/THF/TiCl4 catalysts

Homo- and copolymerization of ethylene were performed by using a catalyst system composed of TiCl₄/THF/MgCl₂ complex activated with AlEt₃ at 70°C and 3 atm. To investigate the effect of the compositional difference of the catalyst on the rates of homo- and copolymerization and on the reactivity in ethylene–hexene copolymerization, a series of six catalysts with different compositions (Mg/Ti = 0.4–16.5) were prepared by coprecipitation. The catalytic activity in ethylene polymerization increased sharply with the Mg/Ti ratio from 21 (Mg/Ti = 0.4) to 1477 kg PE/g-Ti h (Mg/Ti = 16.5). The activity in copolymerization with 1-hexene also increased with Mg/Ti ratio. The values of r₁ were 120, regardless of Mg/Ti ratios within the experimental error range. Enhancement of the polymerization rate by the addition of 1-hexene in the reaction medium was observed only for the catalysts of low Mg/Ti ratio. This unusual effect of 1-hexene on the polymerization rate was explained by chemical and physical processes that occurred during polymerization. © 1993 John Wiley & Sons, Inc.