TiCl4 Catalyst Research Articles

Direct mechanochemical synthesis of nano-LiAlH4 promoted by 0.696 wt% TiCl4 catalyst surface-modified Al powder

LiAlH4, known for its high hydrogen capacity and metastable nature, is a promising hydrogen source under mild conditions. However, its reversible regeneration from stable binary dehydrogenation phases (LiH/Al) is thermodynamically and kinetically hindered. By constructing a homogeneous and highly dispersed molecular layer of TiCl4 on the surface of the Al reactant to enhance the kinetics of the multiphase interfacial reaction, we achieved the direct mechanochemical synthesis of nano-LiAlH4, bypassing the intermediate phase Li3AlH6. Using the strong Lewis acidity of Ti4+, TiCl4 was chemically adsorbed onto the surface of the Al powder through Ti-O-Al bonds, with a loading capacity of only 0.696 wt%. The obtained TiCl4 surface-modified Al powder and LiH were hydrogenated by ball milling for 10 h under hydrogen pressure to synthesize nano-LiAlH4, which was then dehydrogenated at room temperature. This indicates that the crucial effects of the catalytic sites were dispersed on the reactant surface to ensure the local environment of the multiphase absorption/desorption hydrogen reaction interface and promote the reaction kinetics.

The Use of the Titanium Tetrachloride (Ticl4) Catalysts as a Reagent for Organic Synthesis

Abstract: TiCl4 is a widely utilized reagent in organic synthesis, often functioning through Lewis’s acid-promoted transformations. This review explores the potential for TiCl4 to catalyse various examples, adhering to the classic catalyst definition and allowing for the use of sub-stoichiometric quantities of the catalyst relative to the substrate. The use of metal catalysts in organic synthesis has witnessed a surge in interest due to their ability to facilitate a wide range of chemical reactions. This review article highlights the significance of titanium metal catalysts via comparison with other metal catalysts like Pd [NO3]2, IrO4, Au/Fe2O3, SnCl2, and AlCl3. Among these catalysts, titanium tetrachloride (TiCl4) has gained considerable popularity for its cost-effectiveness, eco-friendliness, enhancing reaction efficiency, and ability to accelerate reactions while reducing reaction times. This comparison helps in determining the most suitable catalyst for different chemical processes, considering efficiency, safety, and economic factors. TiCl4 operates as a non-consumable catalyst, allowing for the use of sub-stoichiometric quantities relative to the substrate. This review discusses TiCl4's applications, efficiency, and mechanisms in organic synthesis. It distinguishes itself by presenting new applications and comparative efficiencies of TiCl4, delving into detailed reaction mechanisms, and discussing its environmental, economic, and safety aspects. TiCl4's role in pivotal chemical reactions, such as Friedel-Crafts acylation and alkylation, epoxidation, cyclization, Mannich reactions, Suzuki-Miyaura reactions, Pechmann condensation, Knoevenagel condensation, anti-Markovnikov hydration, pinacol coupling, and Diels-Alder reactions. These reactions have led to the synthesis of biologically active compounds like zolmitriptan, ropinirole, risperidone, and rivastigmine. TiCl4-catalyzed reactions are characterized by their mild conditions, high efficiency, and selectivity, making them an attractive choice for modern organic cyclic, acyclic, and heterocyclic synthesis.

The evolution of stereoselective olefin polymerization modeling

We review the story of stereoselective 1-olefin polymerization with a focus on the production of isotactic polypropylene. Starting from the visionary modeling of early TiCl3 catalysts, this contribution will move to introduce briefly to the modeling of stereoselective propene polymerization by homogeneous catalysts and will conclude with an outlook on the type of modeling and techniques that will likely dominate the near future.

Highly Efficient Cationic Polymerization of β-Pinene, a Bio-Based, Renewable Olefin, with TiCl4 Catalyst from Cryogenic to Energy-Saving Room Temperature Conditions

Polymers based on renewable monomers are projected to have a significant role in the sustainable economy, even in the near future. Undoubtedly, the cationically polymerizable β-pinene, available in considerable quantities, is one of the most promising bio-based monomers for such purposes. In the course of our systematic investigations related to the catalytic activity of TiCl4 on the cationic polymerization of this natural olefin, it was found that the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl4/N,N,N',N'-tetramethylethylenediamine (TMEDA) initiating system induced efficient polymerization in dichloromethane (DCM)/hexane (Hx) mixture at both -78 °C and room temperature. At -78 °C, 100% monomer conversion was observed within 40 min, resulting in poly(β-pinene) with relatively high Mn (5500 g/mol). The molecular weight distributions (MWD) were uniformly shifted towards higher molecular weights (MW) in these polymerizations as long as monomer was present in the reaction mixture. However, chain-chain coupling took place after reaching 100% conversion, i.e., under monomer-starved conditions, resulting in considerable molecular weight increase and MWD broadening at -78 °C. At room temperature, the polymerization rate was lower, but chain coupling did not occur. The addition of a second feed of monomer in the polymerization system led to increasing conversion and polymers with higher MWs at both temperatures. 1H NMR spectra of the formed polymers indicated high in-chain double-bond contents. To overcome the polarity decrease by raising the temperature, polymerizations were also carried out in pure DCM at room temperature and at -20 °C. In both cases, rapid polymerization occurred with nearly quantitative yields, leading to poly(β-pinene)s with Mns in the range of 2000 g/mol. Strikingly, polymerization by TiCl4 alone, i.e., without any additive, also occurred with near complete conversion at room temperature within a few minutes, attributed to initiation by adventitious protic impurities. These results convincingly prove that highly efficient carbocationic polymerization of the renewable β-pinene can be accomplished with TiCl4 as catalyst under both cryogenic conditions, applied widely for carbocationic polymerizations, and the environmentally benign, energy-saving room temperature, i.e., without any additive and cooling or heating. These findings enable TiCl4-catalyzed eco-friendly manufacturing of poly(β-pinene)s, which can be utilized in various applications, and in addition, subsequent derivatizations could result in a range of high-added-value products.

Depolymerization of Polyesters by Transesterification with Ethanol Using (Cyclopentadienyl)titanium Trichlorides

Exclusive chemical conversions of polyesters [poly(ethylene adipate) (PEA), poly(butylene adipate) (PBA), poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT)] to the corresponding monomers (diethyl adipate, diethyl terephthalate, ethylene glycol, 1,4-butane diol) by transesterification with ethanol using Cp’TiCl3 (Cp’ = Cp, Cp*) catalyst have been demonstrated. The present acid-base-free depolymerizations by Cp’TiCl3 exhibited completed conversions (>99%) of PET, PBT to afford diethyl terephthalate and ethylene glycol or 1,4-butane diol exclusively (selectivity >99%) without formation of any other by-products in the NMR spectra (150–170 °C, Ti 1.0, or 2.0 mol%). The resultant reaction mixture after the depolymerization of PBA with ethanol via the CpTiCl3 catalyst (1.0 mol%, 150 °C, 3 h), consisting of diethyl adipate and 1,4-butane diol, was heated at 150 °C in vacuo for 24 h to afford high molecular weight recycled PBA with unimodal molecular weight distribution (Mn = 11,800, Mw/Mn = 1.6), strongly demonstrating a possibility of one-pot (acid-base-free) closed-loop chemical recycling.

Selective lead (II) sorption using aminophosphonate-based sorbents: Effect of amine linker, characterization and sorption performance

A one-pot synthesis procedure is designed for preparing two α-aminophosphonate-based-sorbents (DA and TA sorbents). The reaction takes place between amine precursors (two different aliphatic amines with different chain lengths and amino group content; i.e., ethylenediamine (DA) or diethylenetriamine (TA), respectively) and both salicylaldehyde and diphenyl phosphite. Ionic liquid may be used under controlled conditions as an alternative to TiCl4 catalyst. These materials are first characterized by SEM-EDX, AFM, BET, XRD, FTIR, 1H-, 13C-, and 31P NMR, XPS, TGA, elemental analysis (CHNP), and titration (PZC). Combined with the study of pH effect on Pb(II) sorption, FTIR and XPS analyses are used for exploring the mechanisms involved in metal binding. In a second step, the sorption properties are compared for Pb(II) recovery at pH ≈5. Maximum sorption is influenced by the length of the chain: DA (0.694 mmol Pb g−1) > TA (0.494 mmol Pb g−1). The sorption isotherms are modelled by the Sips equation for DA (and the Langmuir Dual Site equation) and by the Langmuir equation for TA. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) indicate the spontaneous, endothermic nature and randomness increases during the sorption process. The uptake kinetics (equilibrium reached ≈120 min) is almost equally fitted by the pseudo-first-order rate equation and the pseudo-second-order rate equation. The sorbents show selective Pb(II) sorption against heavy base metals in multi-component solutions. QSAR tools (quantitative activity structure–activity relationships) are used for evaluating the correlation between their intrinsic metal characteristics and their affinities for sorbents. The sorbents are efficiently recycled for at least 5 cycles using 0.2 M HCl as the eluent (loss in sorption and desorption performances ≈10-14% at the fifth cycle, compared with the first cycle).

Effect of ligands in TiCl3(OAr) catalysts for ethylene polymerization: Computational and experimental studies

Ethylene insertion into the TiC bond at the TiCl3(OAr) catalysts in ethylene polymerization was investigated with density functional theory (DFT), in order to explore the effect of different Ar- ligands, such as C6H5-, 2,6-Me2C6H3- or 2,6-iPr2C6H3-. The computational results showed the activation energy and reaction heat of the insertion of ethylene monomer into the TiC bond in the [TiClOArCH2CH3]+ active center were between those in the [TiClCpCH2CH3]+ and [TiCl2CH2CH3]+ active centers, due to that the aryloxy group could slightly change the chemical environment of the active titanium cation. Moreover, the ethylene polymerization was carried out using these TiCl3(OAr) catalysts supported by MgCl2 (TiCl3(OAr)/MgCl2), and polyethylene (PE) was obtained with higher molecular weight and relatively narrow molecular weight distribution, like the polymerization using metallocene catalysts. The experimental results were consist with the DFT computational results, indicating that the ethylene polymerization could be controlled by adjusting the Ar- ligand in the TiCl3(OAr) catalysts.

Mechanochemical synthesis and effect of various additives on the hydrogen absorption\u2013desorption behavior of Na3AlH6

Sodium aluminum hydride has been extensively investigated for hydrogen storage applications whereas its intermediate decomposition compound Na3AlH6 received much less attention, despite having a lower dissociation pressure and a reasonable hydrogen storage capacity of 3.0 wt%. In this work, Na3AlH6 is synthesized through ball milling, starting from NaAlH4 and 2 NaH in the presence of TiCl3 catalyst precursor, and evaluated on its hydrogen sorption properties and cycle stability. Further addition of 8 mol% Al and 8 mol% activated carbon (AC) and their effect on both the hydrogen sorption properties and cycle stability have been investigated. In order to explore whether the introduction of the Al and AC additives would be more beneficial (in terms of hydrogen sorption behavior and cycle stability) after the Na3AlH6 synthesis or during its synthesis, pre-synthesized Na3AlH6-based measurements were also included in this work. TiCl3-catalyzed NaAlH4 + 2 NaH sample showed a stable reversible hydrogen storage capacity of 1.7 wt%, which was further increased to 2.1 wt% with the addition of Al-powder and activated carbon AC.

Facile preparation of functionalized MoS2/polyethylene nanocomposites through in situ polymerization with MoS2 containing Ziegler–Natta catalyst

A facile method for preparing polyethylene (PE)/octadecylamine-functionalized MoS2 (ODA-MoS2) nanocomposites through in situ polymerization with an ODA-MoS2-MgCl-TiCl4 catalyst was developed. The catalyst was synthesized simply by the treatment of ODA-MoS2 with a Grignard reagent, followed by anchoring of a TiCl4 catalyst. The resulting catalyst exhibited higher activity toward ethylene polymerization than did an ODA-MoS2-free catalyst. After polymerization, the resultant PE/ODA-MoS2 nanocomposites reproduced the catalyst morphology, showing a flaked morphology. In addition, the thermal stability and mechanical properties of PE were significantly enhanced by the introduction of ODA-MoS2 fillers. These properties could result from the good dispersion and strong interfacial adhesion of ODA-MoS2 fillers and the PE matrix.

Synthesis of highly isotactic poly 1-hexene using Fe-doped Mg(OEt)2/TiCl4/ED Ziegler–Natta catalytic system

In this article, polymerization of 1-hexene with FeCl3-doped Mg(OET)2/TiCl4/electron donor (ED) catalytic system is presented. For this purpose, first a number of TiCl4 catalysts supported on Mg(OEt)2 and Fe-doped Mg(OEt)2 supports were prepared with ethylbenzoate or dibutylphthalate as the internal EDs. After successive catalysts synthesis, they were employed in 1-hexene polymerization using cyclohexyl methyl dimethoxysilane as external ED as well as without it. The catalysts activity and molecular weight distribution (MWD) of poly 1-hexenes (PHs) were influenced strongly by both FeCl3 doping and donor presence so that a remarkable increase in the catalyst activity was seen in doped catalysts. Deconvolution of MWD curves revealed that increase in the type of active centers by introducing FeCl3 into the support should be responsible for the broadening of MWD of PHs. 13CNMR analysis indicated that while isotacticity does not change considerably by Fe doping, EDs increase its amount as high as 8–21%. Second, the stereoselective behavior of active Ti species in doped and undoped catalysts was fully explored by molecular modeling using density functional theory (DFT) method. Finally, with the aid of rheological measurements, the processability of polymers were evaluated and then the gel permeation chromatography (GPC) results were approved through the values obtained from model fitting as well as changes in moduli crossover modulus.

Catalytic effect of Nb2O5 on dehydrogenation kinetics of NaAlH4

Sodium alanate is an important hydrogen storage material with high hydrogen content of 7.5 wt%, but it does not release hydrogen easily. In the present work niobium oxide (Nb2O5) and titanium cholride (TiCl3) catalysts are used to dehydrogenate NaAlH4. Structure and morphology of materials are characterized by XRD and SEM techniques. Sodium alanate was found to have tetragonal structure having a = 5.02 Å, b = 5.02 Å and c = 11.34 Å lattice parameters. Dehydrogenation of NaAlH4 at 250 °C converts it to a great extent to Na3AlH6 with lattice parameter a = b = c = 7.755 Å, living behind a very small amount of sodium alanate reflecting in XRD peak. Scanning electron microscopic studies shows reduction in particle size after dehydrogenation. The dehydrogenation kinetics of the samples was studied using dynamic Seivert type apparatus. The amount of desorbed hydrogen was found to be 4.8 and 5.0wt %.

ChemInform Abstract: SnCl4 or TiCl4: Highly Efficient Catalysts for the Detetrahydropyranylation and Demethoxymethylation of Phenolic Ethers and Sequential One‐Pot Asymmetric Synthesis of 3‐Aryl‐2‐hydroxy‐2,3‐dihydroindan‐1‐ones from Chalcone Epoxides.

SnCl4 or TiCl4 catalysts provided a rapid and efficient detetrahydropyranylation and demethoxymethylation of phenolic ethers and a sequential one-pot intramolecular Friedel–Crafts alkylation of chalcone epoxides under mild reaction conditions. The reaction took 2–3 min to give the phenols and 1-indanones in an excellent yield (90–98%) at 0 °C without affecting other functional groups. With these catalysts, our protocol gave regioselective products as trans-3-aryl-2-hydroxy-1-indanones in an excellent yield (76–98%) and an enantiomeric excess of up to 99.9% under the same conditions.

SnCl4 or TiCl4: highly efficient catalysts for the detetrahydropyranylation and demethoxymethylation of phenolic ethers and sequential one-pot asymmetric synthesis of 3-aryl-2-hydroxy-2,3-dihydroindan-1-ones from chalcone epoxides

SnCl4 or TiCl4 catalysts provide a rapid and efficient detetrahydropyranylation and demethoxymethylation of phenolic ethers and a sequential one-pot intramolecular Friedel–Crafts alkylation of chalcone epoxides under mild reaction conditions.

ChemInform Abstract: Polysubstituted Pyrrole Derivatives via 1,2‐Alkenyl Migration of Novel γ‐Amino‐α,β‐unsaturated Aldehydes and α‐Diazocarbonyls.

Tri-substituted pyrrole derivatives were successfully synthesized from aminoaldehyde and α-diazocarbonyl, using a TiCl4 catalyst. The reactions proceeded via 1,2-migration and condensation, leading to the corresponding pyrroles in moderate to excellent yields. Reaction susceptibility was subsequently demonstrated by the variation in substrates.

A first principles study on the synergistic catalytic mechanism of anion, cation ions in TiF3, TiCl3 catalysts for LiBH4 hydrogen-storage materials

The synergistic catalytic mechanism of anion, cation ions in TiF3, TiCl3 catalysts for LiBH4 has been studied by first-principles method based on density functional theory. According to the results, Ti metal doping in LiBH4 is not easy realized with respect to halogen elements. Co-doping with transition metal and elements in halogen family is achieved easier than doping with Ti alone. For TiF3 catalyst, to achieve doping with one kind of element is helpful to doping with another kind of element, which accordingly results in the increase of doping concentration. Based on the analysis of the electronic structure, we find that doping with halogen element alone can reduce the stability of LiBH4; while doping with Ti alone leads to the rise of Fermi level; the introduction of defect energy level and the weakening of B-H bond; these may be responsible for improving greatly the desorption kinetics of LiBH4 by titanium halide catalysts. The improvement of the dehydrogenating kinetics of LiBH4 with titanium halide catalyst additives is mainly due to the B-H bond weakening, which makes H atom diffuse easily. For TiF3, TiCl3 catalysts, in the reversible desorption process of LiBH4, F and Ti have synergistic action for the B-H bond weakening, but the synergistic action of Cl and Ti is not obvious, this may be the reason for the advantage of TiF3 over TiCl3 in LiBH4 catalytic reaction.

Polysubstituted pyrrole derivatives via 1,2-alkenyl migration of novel γ-amino-α,β-unsaturated aldehydes and α-diazocarbonyls

Tri-substituted pyrrole derivatives were successfully synthesized from aminoaldehyde and α-diazocarbonyl, using a TiCl4 catalyst. The reactions proceeded via 1,2-migration and condensation, leading to the corresponding pyrroles in moderate to excellent yields. Reaction susceptibility was subsequently demonstrated by the variation in substrates.

Preparation and properties of isotactic polypropylene obtained from MgCl2-supported TiCl4 catalyst bearing bifunctional internal donor

In this research, a novel MgCl2-supported TiCl4 catalyst in conjunction with bifunctional internal donor was synthesized. The effects of internal donor on propylene polymerization behaviors and polymer properties (morphology, M w and MWD) were investigated. It was found that the activity of novel catalyst was higher than that of the traditional DIBP-based Ziegler–Natta catalyst, while the catalyst activity was less influenced by the ether group length of the bifunctional internal donor. It was also observed that the MWD of PP obtained by bifunctional internal donor-based catalyst was broader than that of PP made by DIBP-based Ziegler–Natta catalyst.

Synthesis and characterization of new acetalized [60]fullerenes

Acetalized [60]fullerenes were synthesized from cyclohexanone-fused [60]fullerene, which was facilely prepared by Diels–Alder reaction of C60 with silylether diene, on treatment of various aliphatic alcohols under TiCl4 catalyst. The spiro-cyclic acetalized [60]fullerenes having five, six, and seven-membered rings were also synthesized by using the corresponding diols under the same condition. The slightly raised reduction potentials Ered (∼0.04 V) relative to those of PCBM were observed by cyclic voltammetry measurement, depending on the identity of alkyl group/chain. The noncyclic acetalized [60]fullerenes showed lower thermal stability up to 200 °C, while the cyclic ones exhibited the drastically improved thermal stability up to 350 °C under nitrogen atmosphere. The acid-catalyzed hydrolysis easily removed the acetal moiety quantitatively, resulting in a considerable change of solvent solubility of the fullerene.

Melamine-Formaldehyde-Supported Titanium-Based Heterogeneous Ziegler-Natta Catalyst for Ethylene Polymerization in Slurry Process

Ethylene was polymerized at 40°C temperature and 1 atm. pressure using melamine-formaldehyde (M-F) supported titanium tetrachloride (TiCl4) catalyst. Polymer-supported catalysts were prepared with a different weight ratio of TiCl4/ M-F in hexane. The wt% titanium incorporated in the polymer matrix was determined by UV-visible spectroscopy. In addition, the resulting catalysts were characterized by SEM-EDX, XRD, and TGA. The catalytic productivity is found to be 4721.09 g PE/g Ti/h. The productivity of the catalysts also depends on the titanium content in the polymer matrix. The catalyst with titanium content 3.5 wt% showed maximum activity. These catalysts also showed good storability.

Controlled radical polymerization of vinyl acetate in presence of mesoporous silica supported TiCl4 heterogeneous catalyst

The heterogeneous TiCl4 catalysts supported on mesoporous mobile composition of matter (MCM-41) and mesoporous silicone particles synthesized from block copolymer of PPG–PEG–PPG (SPB) complexed with dimethyl formamide (DMF) ligand were used in a controlled free radical reaction with benzoyl peroxide (BPO) initiator in bulk polymerization of vinyl acetate (VAc). In this polymerization process, mesoporous particle of SPB increased the reactivity of TiCl4 catalyst with DMF ligand. The active site formed on the surface and the pores of the catalyst produced specific sequences of VAc on the chain with different thermal and microstructural properties and crystallinity.