Oligomerization Of 1-hexene Research Articles

MCM-22 zeolite-based system to produce jet fuel from the 1-hexene oligomerization

The oligomerization of light olefins is an alternative for generating clean liquid fuels. In this study, the MCM-22 zeolite featuring a partially disordered layered structure with framework combined 10 membered ring (10 MR) was discussed for 1-hexene oligomerization. MCM-22 and Y zeolite were compared to investigate the influences of the framework and acidity strength on the activity and yield in the 1-hexene oligomerization. The results indicated that the MCM-22 zeolite was an efficient catalyst for oligomerization compared to Y zeolite. The MCM-22 zeolite was characterized in detail by NMR, Py-FTIR, and TG analyses. The catalytic performance and deactivation properties of MCM-22 zeolite in the oligomerization reaction of 1-hexene were investigated. Structure–activity relationships were established through the kinetic study. Although the density of strong acid sites was essential for the oligomerization of 1-hexene, the presence of low pressure was also necessary for the formation of dimers. Thus, MCM-22 zeolite demonstrates a substantial improvement in initial conversion and catalyst lifespan for 1-hexene oligomerization.

Catalytic Properties of Zirconocene-Based Systems in 1-Hexene Oligomerization and Structure of Metal Hydride Reaction Centers

Despite large-scale investigations of homogeneous single-site metallocene catalysts and systems based on them, there are still unsolved problems related to the control of their activity and chemo- and stereoselectivity. A solution to these problems is required to develop efficient methods for the synthesis of practically useful products of alkene transformations, such as dimers, oligomers, and polymers. Here we studied the catalytic activity of structurally diverse zirconocenes (L2ZrCl2, L = Cp, C5Me5, Ind, L2 = Me2CCp2, Me2SiCp2, Me2C2Cp2, rac-Me2CInd2, rac-H4C2Ind2, BIPh(Ind)2, H4C2[THInd]2), and co-catalysts activating the system, namely HAlBui2, MMAO-12, and (Ph3C)[B(C6F5)4], at low activator/Zr ratios in a 1-hexene oligomerization reaction. The influence of catalyst structure and system composition on the alkene conversion, the type of products, and the reaction stereoselectivity were investigated. The composition of hydride intermediates formed in the L2ZrCl2-HAlBui2-activator system (L2 = ansa-Me2CCp2, Ind) was studied by NMR spectroscopy. Participation of the bis-zirconium hydride complex as the precursor of catalytically active sites of the alkene dimerization reaction was shown.

Fluoride-treated IM-5 zeolite as a highly active catalyst for the production of jet fuels by the oligomerization of 1-hexene

Light alkenes oligomerization, performed in the presence of solid acid catalysts, is an important alternative for the production of clean jet fuels. For 1-hexene oligomerization, the current catalyst often suffers from low activity and selectivity. The developed process is upgraded by zeolite catalyst, targeting high-concentration of jet-range hydrocarbons. An efficient and selective IM-5 zeolite-derived catalytic system has been developed for the oligomerization of 1-hexene. The treatment in an aqueous NH4F solution led to dealumination without structure degradation. The IM-5 zeolite with a unique two-dimensional IMF structure and 2.5 nm nanoslab showed rapid diffusion ability than ZSM-5 zeolite. Enhance acidities were observed in the NH4F-treated IM-5 zeolites owing to fluoride residue and the removal of Al atoms. The strong Brønsted acid sites exerted a positive effect on both the cracking and the oligomerization reactions with the increasing of the yields of dimers. The contact time and partial pressure between the 1-hexene and the IM-5 zeolites were used to analyze the competition of cracking reactions. High 1-hexene conversion (62%), optimal oligomerization to C3-C5 ratio (O/C = 32), and reasonable stability were obtained over the etched IM-5 catalyst at 240 °C, 4 MPa, and the flow rate of N2 was 50 mL/min.

Investigation of the interactions for the 1-hexene oligomerization and the catalytic cracking reactions

Using 1,3,5-triisopropylbenzene (1,3,5-TIPB) and n-octane as the catalytic cracking feedstocks and 1-hexene as the oligomerization feedstock, the coupling mechanism of catalytic cracking reaction and olefin oligomerization reaction over the synthesized hierarchical ZSM-5 zeolite catalyst was evaluated. The results of catalytic cracking reaction of model compounds showed that the catalytic cracking performance of molecules with different sizes was inhibited on the synthesized hierarchical ZSM-5 zeolite. The cracking activity of 1,3,5-TIPB decreased, and the initial activity of n-octane reduced from 70% to 20%. However, enhanced 1-hexene oligomerization activity was observed over the hierarchical ZSM-5 zeolite, with dimer as the main product. The reduction of the strong acid sites in the zeolite can inhibit the catalytic cracking reaction and promote the oligomerization of C6 olefin into dimer and trimer (ideal components of jet fuel). Therefore, the designing of the catalyst from the perspective of inhibiting the activity of catalytic cracking can effectively improve the oligomerization performance of the catalyst.

Plasma activated 1-hexene oligomerization in a gas–liquid microreactor

The oligomerization of 1-hexene under argon plasma was investigated in a gas–liquid, continuous flow microreactor.

Mesoporous ZSM-5 catalysts for the synthesis of clean jet-fuels by 1-hexene oligomerization

Zeolite is one kind of the solid acid catalysts for the oligomerization process but surfers from rapid deactivation. In this specific study, a series of mesoporous ZSM-5 catalysts have been synthesized and evaluated in the 1-hexene oligomerization. XRD, BET, SEM, TEM, 27Al MAS NMR, 29Si MAS NMR, NH3-TPD, Py-FTIR and TGA analysis were used to characterize the physicochemical properties of zeolites. The synthesized mesoporous zeolites were found to be more stable in the reaction and the initial activity increase significantly compared with the common ZSM-5 zeolite. Moreover, the catalytic activity of mesoporous ZSM-5 zeolite is found to be closely related to the number and the distribution of acid sites. The mesoporous ZSM-5 zeolites with the lower amount of acid sites, moderate strength of Brønsted acid sites inhibiting the cracking and coke products. High L/B ratio enhanced the dimers formation. The efficiency was further highlighted by a high space–time yield (STY) of 557 mg·gcat−1h−1 in the average stage at 260 °C. Compared to conventional ZSM-5 catalyst, the synthesized catalyst displayed excellent resistance to coke deposit.

Synthesis, Structure, and Reactivity of Dicationic Bimetallic Tetrabenzyldihafnium Complexes Bearing a Chelating (2-Hydroxyethyl)amido Ligand

We prepared the bimetallic hafnium complex 1 by reaction of Hf(CH2Ph)4 with the alcohol-imine proligand L via deprotonation and subsequent benzyl migration from the hafnium atom to the imine moiety of L. The complex 1 was obtained as a diastereomeric mixture of 1a (SR, heterochiral) and 1b (RR and SS, homochiral); the SR isomer 1a was readily isolated by simply washing with toluene. Treatment of 1a with [Ph3C][B(C6F5)4] in C6H5Cl afforded the dicationic complex 2a, which was characterized by spectroscopic data and an X-ray diffraction study, revealing the η6 coordination of the phenyl group bound to the chelating ligand to the cationic hafnium center. Complex 2a showed catalytic activity for 1-hexene oligomerization at 100 °C in combination with 2 equiv of [Ph3C][B(C6F5)4], while 4,4′-dimethoxydiphenylacetylene reacted with 2a to quantitatively afford alkene 3 at room temperature after hydrolysis. The addition of PMe2Ph and pyridine to 2a dissociated the η6-arene coordination of the ligand to give the corresponding adducts 5a and 6a, whose structures were fully characterized by X-ray diffraction analysis.

Carbazolyl-Substituted [OSSO]-Type Zirconium(IV) Complex as a Precatalyst for the Oligomerization and Polymerization of α-Olefins

The dibenzyl zirconium(IV) complex (4) incorporating with a carbazolyl(Cbz)-substituted [OSSO]-type bis(phenolate) ligand was synthesized. Upon activation with dried modified methylaluminoxane (dMMAO), precatalyst 4 at relatively low catalyst loadings was found to promote the 1,2-regioselective oligomerization of 1-hexene to produce the corresponding vinylidene-ended oligomers with moderate turnover frequencies (TOFs) up to 2080 h−1. The 13C NMR analysis of the resulting oligomers revealed the formation of dimer-enriched oligo(1-hexene)s in 39–62% distributions. The precatalyst 4 with dried methylaluminoxane (dMAO) also exhibited good performance in the polymerization of styrene yielding isotactic polystyrenes ([mm] > 99%) with quite large molecular weights (Mw < 508,100 g mol−1) and relatively high catalytic activity (up to 2810 g mmol(4)−1 h−1).

Oligomerization of lower olefins to fuel range hydrocarbons over texturally enhanced ZSM-5 catalyst

Abstract Zeolites with various pore structures and sizes such as microporous ZSM-5, desilicated ZSM-5, Beta zeolite and ZSM-48 were investigated as catalysts in the oligomerization of propylene and 1-hexene to fuel-range hydrocarbons. Mesoporous ZSM-5 was prepared via a post-synthesis alkaline treatment. Physicochemical properties of the zeolite catalysts were characterized by XRD, XRF, SEM, TEM, MAS NMR, BET, and NH3-TPD techniques to analyze the crystallinity, element composition, morphology, textural properties as well as acidity distribution. The catalyst characterization confirmed that NaOH post-treatment by mild desilication is an effective method to tune the pore structure of medium pore ZSM-5 zeolite by introducing mesoporosity without damaging the microporous structure. Enhanced activity and selectivity to jet fuel/diesel range (C12) products of ˜90% and 55% respectively was achieved over a modified ZSM-5 catalyst at optimum reaction conditions of 220 °C and weight hourly space velocity (WHSV) of 4 h−1 in the oligomerization of 1-hexene. Good selectivity to gasoline-range hydrocarbons with high octane number was achieved over modified ZSM-5 in the oligomerization of propylene. The spent catalysts were characterized by thermogravimetric and NH3-TPD analyses which confirmed that carbonaceous deposits were prevalent inside the micropores of the catalysts but its effects were less severe on the modified ZSM-5.

Highly Efficient and 1,2-Regioselective Method for the Oligomerization of 1-Hexene Promoted by Zirconium Precatalysts with [OSSO]-Type Bis(phenolate) Ligands

A mixture of zirconium complex 7, which carries a phenyl-substituted [OSSO]-type bis(phenolate) ligand, and dried modified methylaluminoxane (dMMAO) catalyzes the 1,2-regioselective oligomerization of 1-hexene at relatively low catalyst loadings (0.0056 mol %) to produce the corresponding vinylidene-terminated dimer, 5-methyleneundecane (74–80%), and trimer, 7-butyl-5-methylenetridecane (8–11%). The observed turnover frequencies (TOFs) are relatively high (up to 11 100 h–1). When a mixture of 2,6-dimethylphenyl-substituted precatalyst 8 and dMMAO was used, the oligomerization of 1-hexene proceeded effectively to afford predominantly the dimer (87–91%) together with a small amount of the trimer (8–11%) at remarkably high TOFs (up to 6640 h–1).

Oligomerization of 1-hexene over designed SBA-15 acid catalysts

SBA-15 acid catalysts were prepared using two different post-synthesis methods, alumination followed by ion-exchange (H-Al/SBA-15) and styrene polymerization followed by sulfonation (H-SP/SBA-15). For the H-Al/SBA-15, 1-hexene conversion and C10+ selectivity tended to increase with increasing pore size, although there were no significant differences higher than 7nm. For the H-SP/SBA-15, the conversion and C10+ selectivity increased with increasing amounts of polymers but there was also an optimum range (20–25wt.%). The overall results demonstrate that controlling the acid properties of the mesoporous SBA-15 is much more critical to 1-hexene oligomerization than improving diffusion limitation by modifying textural properties.

Tin Dioxide-Based Superacid Aerogels Produced Using Propylene Oxide

Tin dioxide-based aerogels were produced by supercritical drying of gels, synthesized using propylene oxide, in CO2 and isopropanol. Aerogels consisted of nanocrystalline cassiterite and had a specific surface area of 210–270 m2/g. Sulfation with sulfuryl chloride imparted superacidic properties to the aerogels (the Hammett acidity function H0 reached values within the range – 11.99 ≥ H0 ≥ –12.7). Superacid SnO2 aerogels demonstrated high catalytic activity in 1-hexene oligomerization and isomerization.

Oligomerization of light olefins over ZSM-5 and beta zeolite catalysts by modifying textural properties

The oligomerization of ethene and 1-hexene was performed under 35 bar and 200 °C over NiH- and H-forms of ZSM-5 and beta zeolite catalysts which had similar Si/Al and Ni content, but different textural properties. Among the H-zeolites, H-ZSM-5 and H-beta composed of nanometer scale (ca. 10 nm) sheet-like crystals, as well as intercrystalline mesoporosity (ca. 5 nm), were found to be much more efficient for the oligomerization of 1-hexene to liquid fuel range products higher than C10 (C10 + ). In the oligomerization of ethene, identically prepared ZSM-5 and beta zeolites but with further exchange with Ni ion, also showed higher activity with remarkable C10+ product selectivity (>80%) after a single stage oligomerization, as compared to the corresponding cation form of ZSM-5 and beta zeolites without nanocrystalline and mesoporous morphology (conversion < 50% and C10+ selectivity < 30%). These results demonstrate that both small crystal size and the mesoporosity of the zeolite catalyst are critical factors for improving the diffusion limitation during the oligomerization of light olefins. This improvement was accompanied by a shift in major oligomeric product selectivity toward C10+ hydrocarbons.

Operando micro-spectroscopy on ZSM-5 containing extrudates during the oligomerization of 1-hexene

The influence of the binder material in an industrial-type catalyst material is often neglected, although the addition of a binder can cause a significant change in the performance of the catalyst.

Vanadium (V) and titanium (IV) compounds with 2-[hydroxy(diaryl)methyl]-8-hydroxyquinolines: Synthesis, structure and catalytic behaviors to olefin polymerization

A series of oxovanadium (V) and titanium (IV) complexes stabilized by [ONO]2− type ligands-2-[hydroxy(diaryl)methyl]-8-hydroxyquinolines (2–3) were synthesized in high yields and characterized by elemental analysis, NMR-, IR spectroscopy and mass spectrometry. The molecular structures of the representative complexes 4 and 7 were confirmed by single-crystal X-ray diffraction, and revealed distorted octahedral geometry at Ti and tetragonal pyramid in V complex. Titanium-based catalytic systems were found to be active in the ethylene and 1-hexene polymerization and copolymerization, but only in the presence of a binary co-catalyst Et2AlCl/Bu2Mg. Vanadium-based systems were active in the same reactions in the presence of Et3Al2Cl3 or Et2AlCl mixed with CCl3CO2Et reactivator. The amount of co-monomer incorporated by these systems have reached 23mol%. When applied in the presence of aliphatic solvents vanadium complexes catalyze 1-hexene oligomerization yielding dimers and trimers. When the same process is carried out in toluene, the solvent got alkylated by monomers and light oligomers (Friedel–Crafts reaction).

Sulfated alumina aerogel-based superacid catalysts for 1-hexene oligomerization

Al2O3 aerogel samples were synthesized by supercritical drying in two different media: isopropanol and methyl tert-butyl ether. After sulfation in a SO2Cl2 vapor, the aerogel acquired superacid properties (–12.4 ≤ H0 ≤–11.99) and efficiently catalyzed 1-hexene oligomerization and dimerization.

Novel bi- and hexanuclear titanium (IV) complexes: Synthesis, structure and catalytic activities in oligo- and polymerization of 1-hexene

Novel bi- and hexanuclear titanium (IV) complexes with 2,2′-bis-(hydroxymethyl)-1,1′-biphenole derivative were synthesized. Structure of complexes 4–5 were established by X-ray diffraction. Resulting catalytic systems obtained by pre-catalysts activation by diethylaluminum chloride or ethyl aluminum sesquichloride were active in the 1-hexene oligomerization. Replacement of alkylaluminumchlorides by a {3Et2AlCl + Bu2Mg} binary system results in formation of predominantly isotactic, high molecular weight poly-1-hexene (content of isotactic pentad mmmm 70%). Systems treated with “traditional” activators – MAO and AlR3 were not active.

Polystyrene-based viscosity additives

Synthesis of viscosity additives based on polystyrene and 1-hexene is described. The first step consists in 1-hexene oligomerization in the presence of aluminum chloride. Then, a solution of polystyrene in chlorobenzene is added into the system in which a carbocation has been formed. In this system, polystyrene undergoes oligoalkylation with 1-hexene oligomers to yield a product soluble in petroleum oils. The synthesized oligoalkylpolystyrene was tested as heat-resistant viscosity additive to petroleum oils.

1-hexene oligomerization by fluorinated tin dioxide

Fluorinated tin dioxide has been shown to exhibit catalytic activity for 1-hexene oligomerization. The physicochemical and functional properties of nanocrystalline fluorinated SnO2 have been studied.

1-Hexene: a renewable C6 platform for full-performance jet and diesel fuels

A highly efficient and selective process has been developed for the conversion of 1-hexene to jet and diesel fuels. In combination with commercial processes for the dehydration of ethanol and trimerization of ethylene, this work provides a basis for the synthesis of full-performance hydrocarbon fuels from bio-ethanol. Selective oligomerization of 1-hexene with a Cp2ZrCl2/MAO catalyst at ambient temperature and pressure resulted in 100% conversion of 1-hexene with >80% selectivity to a mixture of the dimer and trimer. The hydrogenated dimer had a −20 °C viscosity of only 3.5 mPa s, an exceptionally low freezing point of −77 °C, and a cetane number of 67 suggesting that it has performance characteristics suitable for both jet and diesel fuels. The hydrogenated trimer had a flash point of 128 °C, a cetane number of 92, a 40 °C viscosity of 3.1 mPa s, and a −20 °C viscosity of 24.5 mPa s. These properties suggest that the trimer has applications as a high-performance diesel fuel. In addition to the fuel-range hydrocarbons, heavier oligomers have potential as biolubricants which improves the carbon yield of useful products to near quantitative levels.