Alkylation Of Naphthalene Research Articles

Alkylation of naphthalene using three different ionic liquids

It is well known that room temperature ionic liquids (Ils) have the potential for serving as efficient reaction media in the Friedel–Crafts reactions of naphthalene. In this work, three ionic liquid systems prepared with AlCl 3 were used as reaction media for the alkylation of naphthalene with different reagents. The following cations were used to prepare the chloroaluminate(III) ionic liquids: 1-butyl-3-methylimidazolium [Bmim]; 8-butyl-1,8-diazabicyclo[5,4,0]-undec-7-enium [bDBU] and 5-butyl-1,5-diazabicyclo[4,3,0]-non-5-enium [bDBN]. Ionic liquid systems are easy to prepare and show interesting catalytic properties. The thermal stability and structural NMR spectra of the ionic liquids were studied. The Ils rendered this reaction green characteristics. The conversions and reaction yields produced by the alkylation reaction of naphthalene with ethyl bromide and isopropyl chloride in the three ionic liquid systems were compared.

Alkylation of naphthalene with isopropanol over a novel catalyst UDCaT-4: Insight into selectivity to 2,6-diisopropylnaphthalene and its kinetics

Numerous routes to 2,6-naphthalenedicarboxylic acid, a feedstock for high performance polyester polyethylene naphthalate, exist starting with the alkylation of an aromatic ring. However, the route beginning with naphthalenic compounds has an economic advantage because of reduction in the number of reaction steps to build the naphthalene ring. This has spurred a lot of interest in the shape selective dialkylation of naphthalene. Mono alkylation of naphthalene is simple, but its further shape selective dialkylation to 2,6-dialkylnaphthalene (2-DAN), is challenging. A variety of solid acid catalysts especially zeolites have been reported in studies to investigate the effect of acidity, pore geometry and shape selectivity in this reaction. However, the activity of most catalysts is susceptible to coke formation within a few hours of time on stream. It is in this perspective that we report the novelties of UDCaT-4, a synergistic combination of persulfated alumina and zirconia with hexagonal mesoporous silica, which exhibits tremendous stability, activity and selectivity in the vapour-phase isopropylation of naphthalene with isopropanol to 2,6-diisopropylnaphthalene (DIPN). It leads to better yields and selectivity in comparison with other catalysts reported in literature. A systematic investigation of the effects of various operating parameters was accomplished. Furthermore, a mathematical model was developed to describe the reaction pathway and the model validated with experimental results.

Alkylation of naphthalene with alcohols over acidic mesoporous solids

Mesoporous cubic MCM-48 was synthesized at a lower concentration of the surfactant. XRD, N 2 adsorption and electron microscopic studies confirmed the formation of cubic phase. Spectroscopic and electron spin resonance techniques confirmed the presence of heteroatom within the framework. The catalytic activities of various acid catalysts have been examined for vapour phase alkylation of naphthalene with alcohols and these studies revealed that aluminium substituted cubic MCM-48 was more active compared to Fe-MCM-48, Al-MCM-41 and H-Y zeolite.

Cerium-containing MCM-41 materials as selective acylation and alkylation catalysts

The synthesis of Ce–MCM-41, Al–MCM-41 and Ce–Al–MCM-41-type mesoporous materials was carried out hydrothermally by refluxing the gel with magnetic stirring under atmospheric pressure for 24–36 h. The samples were characterized thoroughly in order to obtain the structural and textural properties, which reveal the presence of well-ordered M41S-type materials. The Ce–MCM-41 samples were used for catalytic acylation of alcohols, thiols, phenols and amines show good activity and selectivity including high chemoselectivity towards selective monofunctional acylation of bifunctional compounds. Quite importantly the acylation of bulky molecules such as cholesterol, ergesterol and β-sitosterol could be achieved using Ce–MCM-41 as solid catalyst. The presence of Ce along with Al in Ce–Al–MCM-41 was found to have synergistic effect as Ce–Al–MCM-41samples were more active catalysts for alkylation of naphthalene compared to either Ce–MCM-41 or Al–MCM-41 with comparable Si/Al or Si/Ce molar ratio.

Molecular Shape, Dimensions, and Shape Selective Catalysis

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of Hexylnaphthalene, Characterization of the Products and the Reaction Mechanism

The structures of the compounds in the reaction of naphthalene with 1-bromohexane catalyzed by aluminium chloride were characterized by gas chromatography/mass spectrometry (GC/MS) and the reaction mechanisms, especially the side reaction, were discussed. The main products include three kinds of linear mono-hexylnaphthalenes (1-(β)naphthylhexane, 2-(β)naphthylhexane, and 3-(β)naphthylhexane) and 10 linear di-hexylnaphthalenes. The by-products mainly are tetralin, mono-hexyltetralin, isohexane, and hexylbenzene. The alkylation of naphthalene with bromohexane was a typical Friedel-Crafts reaction and the side reactions were the disproportionation reaction of naphthalene, tetralin, and 1-bromohexane.

Equatorial Preference in the C—H Activation of Cycloalkanes: GaCl3‐Catalyzed Aromatic Alkylation Reaction.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Molecular shape, dimensions, and shape selective catalysis

Molecular shape is a fundamental quantum mechanical property determined by the spatial distribution of electrons in the molecule. Enzymes, the catalysts of biology, and zeolites, the catalysts of inorganic chemistry, show remarkable shape selective properties. Generally, the active sites are confined within the three-dimensional structures of the catalysts, so the fate of the reactant/intermediate/product molecules depends primarily on their molecular shapes and dimensions. An ab initio method is applied for calculating molecular shapes and dimensions. Selective alkylation of naphthalene over various zeolites is reviewed and discussed in this paper from the viewpoints of these properties.

Isopropylation of naphthalene over modified faujasites: effect of steaming temperature on activity and selectivity

Naphthalene alkylation with isopropyl alcohol (IPA) to obtain 2,6-diisopropylnaphthalene (2,6-DIPN) was studied over HY and steam-treated HY zeolite catalysts in a continuous down flow micro reactor under atmospheric pressure with cyclohexane as the solvent. The catalytic performance of the catalysts for naphthalene conversion and yield for 2,6-DIPN increases with steaming temperature, suggesting higher acid strength is required for the dialkyaltion. Under reaction conditions, 250 °C, with a feed of naphthalene:isopropanol:cyclohexane=1:3:10 (molar ratio) and space velocity WHSV=4.86 h −1, 86% naphthalene conversion and a 2,6-DIPN yield of 40% was obtained with HY-700 catalyst.

Equatorial preference in the C[bond]H activation of cycloalkanes: GaCl3-catalyzed aromatic alkylation reaction.

GaCl(3) catalyzes the aromatic alkylation of naphthalene or phenanthrene using cycloalkanes. The C[bond]C formation predominantly takes place at the least hindered positions of the substrates, and equatorial isomers regarding the cycloalkane moiety are generally obtained. The reaction of bicyclo[4.4.0]decane and naphthalene occurs at the 2-position of naphthalene and at the 2- or 3-carbons of the cycloalkane, and the products possess a trans configuration at the junctures and an equatorial configuration at the naphthyl groups. Notably, cis-bicyclo[4.4.0]decane turns out to be much more reactive than the trans isomer, and a turnover number "TON" up to 20 based on GaCl(3) is attained. 1,2-Dimethylcyclohexane reacts similarly, and the cis isomer is more reactive than the trans isomer. Monoalkylcycloalkanes react at the secondary carbons provided that the alkyl group is smaller than tert-butyl. Adamantanes react at the tertiary 1-position. The alkylation reaction is considered to involve the C[bond]H activation of cycloalkanes with GaCl(3) at the tertiary center followed by the migration of carbocations and electrophilic aromatic substitution yielding thermodynamically stable products. The stereochemistry of the reaction reveals that GaCl(3) activates the equatorial tertiary C[bond]H rather than the axial tertiary C[bond]H.

A priori selection of shape-selective zeolite catalysts for the synthesis of 2,6-dimethylnaphthalene

Modeling tools based on molecular mechanics and molecular dynamics were used for selecting shape-selective zeolite catalysts for the synthesis of 2,6-dimethylnapthalene (2,6-DMN) through the alkylation of naphthalene (NAPH) or via isomerization of other DMN isomers. A number of medium- (MFI and EUO) and large-pore zeolites ( ∗ BEA, MOR, MAZ, FAU, LTL, OFF, and MTW) were considered and for each of them the minimum energy pathways for the diffusion of naphthalene, 1- and 2-methylnapthalene (MNs), and 1,5-, 1,6-, 2,6-, and 2,7-dimethylnapthalene (DMNs) were computed. The results of the simulations indicated that the diffusion of MNs and DMNs isomers in the medium-pore zeolites is impeded by high-energy barriers, leading to the conclusion that this kind of structure can be used neither in the isomerization nor in the alkylation reaction. In contrast, large-pore zeolites are more promising though their behavior strongly depends on the effective size of the pore openings. Among them, MTW was predicted to be the most promising candidate for the selective alkylation of NAPH to 2,6-DMN. In fact, the simulations indicated high-energy diffusion barriers not only for molecules bearing a CH 3 group in the α-position but also for the undesired 2,7-DMN molecule. Catalytic tests, performed in the presence of 1,2,4-trimethylbenzene as a solvent, confirmed the prediction since MTW gave the highest 2,6-DMN yields with a 2,6-/2,7-DMN ratio in the range 2.0–2.6, well above the thermodynamic value of ≈1 obtained with the other zeolites. The good catalytic performances of MTW were explained by the fact that, unique among the large-pore zeolites considered, this zeolite showed a better stabilization of the 1,1-diarylmethane intermediate molecules leading to 2-MN, 2,6-DMN, and 2,7-DMN. Their formation can be considered more probable than for those deriving from the electrophilic attack of the benzyl carbocation in the α-position of the naphthalene ring.

Supercritical Carbon Dioxide as a Reaction Medium for the Zeolite-Catalyzed Alkylation of Naphthalene

The alkylation of naphthalene with methanol and 2-propanol over the zeolite catalyst LaNaY-73 has been conducted in supercritical carbon dioxide as the reaction medium at 250 °C. Catalytic experiments under flow conditions have been performed at high dilution of the reactants (mole fractions < 0.05) and in the pressure range from 1 to 400 bar. Catalyst deactivation is strongly reduced at supercritical conditions as compared to the one in the gas phase. A pressure increase at supercritical conditions results in a higher catalyst activity. The yield ratio of the major reaction products, i.e., mono- and dialkylnaphthalenes, mainly depends on the alcohol/naphthalene ratio in the feed and is independent of the reaction pressure and the degree of catalyst deactivation. The distribution of isomers within the mono- and dialkylated products changes with time on stream, according to a shift from thermodynamically to kinetically controlled product formation, the extent being dependent on the reaction pressure and th...

Surface chemical modification of zeolites and their catalytic performance for naphthalene alkylation

Zeolites beta, Y and mordenite are modified with organic and inorganic cupric salts using a liquid phase deposit method, and their catalytic performance and the dispersion states of copper on the zeolites are characterized by using naphthalene isopropylation reaction and Xe-129 NMR, respectively. The experimental results indicate that naphthalene conversion on the catalysts decreases in the order of HY>Hbeta>HMCM-22>HM. The performance of the zeolites has been largely improved after the modification. Naphthalene conversion rate reaches 97% and 60%, and beta, beta'-selectivity 66% and 70% for CuHY and CuHbeta, respectively. Metal surfactants, such as hexanoic and octanoic copper, play a positive role in modifying the external surface and pore structure of zeolites beta and Y. Xe-129 NMR results demonstrate that the two types of the pore channels in Cu-Hbeta are unimpeded for xenon atoms, and there is a fast chemical. exchange between two xenon atoms located in different adsorption sites; Cu2+, ion is a strong adsorption site for xenon atoms and it is a strong active center as well; Cu2+ and Cu+ ions coexist in channels of zeolites, which are in agreement with the conclusions from ab initio quantum chemical calculations.

Zeolite Pore Entrance Effect on Shape Selectivity in Naphthalene Isopropylation

Naphthalene alkylation with propylene was studied over various large-pore zeolites and also over amorphous aluminosilicate catalysts. Isomeric distribution of isopropylnaphthalenes and diisopropylnaphthalenes were compared at different temperatures. Surprisingly, higher α-selectivity in monoalkylation and higher concentration of bulky isomers in diisopropylation was observed in the products obtained over zeolites than over amorphous aluminosilicate catalysts. The explanation of such results was proposed to be a specific shape-selectivity effect of alkylation reaction occurring in the entrances to the pores of zeolite. This type of shape selectivity can be very significant and conceal other shape-selectivity effects such as β-selectivity of reactions occurring inside the pores. Results available from the literature, indicating this type of shape selectivity, were also discussed.

Alkylation of naphthalene with t-butanol: use of carbon dioxide as solvent

Organic solvent free alkylation of naphthalene and t-butyl alcohol (TBA) over rare earth exchanged Y zeolite (REY) has been carried out in the presence of carbon dioxide at different process conditions (temperature between 418 and 458 K, pressure between 6 and 92 bar, TBA/naphthalene mole ratios of 1:4, and different periods of time (1.5–9 h)). The results suggest that fluid carbon dioxide can replace organic solvents as a medium for butylation of naphthalene over REY without loss of its shape selective characteristics.

Selective conversion of polycyclic hydrocarbons to specialty chemicals over zeolite catalysts

Recent studies demonstrate that high-value chemicals can be obtained by selective conversion of polycyclic hydrocarbons such as naphthalene,biphenyl,and phenanthrene, over some zeolite catalysts. This article gives examples of shape-selective alkylation of naphthalene into 2,6-dialkylnaphthalene,ring-shift isomerization of sym-octahydrophenanthrene into sym-octahydroanthracene,shape-selective alkylation of biphenyl into 4,4'-dialkylbiphenyl,conformational isomerization of cis-decalin into trans-decalin,selective hydrogenation of naphthalene into either cis-or trans-decalin, and regio-selective hydrogenation of heteroatom-containing aromatic compounds such as 1-naphthol.The products of such selective reactions are specialty chemicals, monomers of advanced polymer materials such as high-performance polyesters, advanced engineering plastics,and liquid crystalline polymers,or components of advanced thermally stable aviation jet fuels for high-Mach aircraft.

Mesoporous silica-immobilized aluminium chloride as a new catalyst system for the isopropylation of naphthalene.

Mesoporous MCM-41 silica immobilized aluminium chloride shows high catalytic activity and selectivity in the Friedel-Crafts alkylation of naphthalene with isopropanol.

Dialkylation of naphthalene with isopropanol over acidic zeolites: Influence of pore structure on selectivity

The liquid phase alkylation of naphthalene with isopropanol has been studied over various large pore zeolites with intermediate aluminum content. While H-Y zeolite exhibits the best activity, and shows a high selectivity in 2,6- and 2,7-diisopropylnaphthalenes, in agreement with previous studies, H-Beta displays a peculiar behavior under the same conditions. The latter produces little diisopropylnaphthalenes; instead, a series of unexpected compounds, consisting of (cyclopentyl)naphthalene derivatives (so-called cyclizates), are formed in high yields. H-Mordenite, which features low activity, also demonstrates such an unexpected behavior towards formation of multialkylated products. The results obtained over H-Beta are more particularly reported, and the identification of the cyclizates is confirmed. A mechanism is proposed to explain the formation of these compounds depending on the various catalytic materials used, and the impact of the pore structure on activity and product distribution is discussed.

THE NITROMETHANE INITIATOR OF THE FRIEDEL-CRAFTS NAPHTHALENE REACTION USING MICROWAVES

The alkylation of naphthalene using halogen derivatives may be achieved under very simple conditions by the Friedel–Crafts reaction. The products are obtained by irradiation of the paste containing the reaction mixture and a small quantity of nitromethane to initiate the reaction.

Shape-selective isopropylation of naphthalene over H–mordenite catalysts for environmentally friendly synthesis of 2,6-dialkylnaphthalene

Recent development of advanced polymer materials such as polyethylene naphthalate, polybutylene naphthalate and liquid crystalline polymers has created an increasing demand for 2,6-dialkylnaphthalene, which has spurred interest in shape-selective naphthalene alkylation. This work deals with mordenite-catalyzed shape-selective naphthalene isopropylation to produce 2,6-diisopropylnaphthalene (2,6-DIPN). Effects of dealumination of mordenite on the structural and acidic characteristics and on the shape selectivity and activity were examined by physicochemical analysis, TPD, solid-state 27 Al and 29 Si MAS NMR, XRD, as well as catalytic alkylation reactions. Dealumination removes octahedral Al species as well as tetrahedral Al species, decreases the unit cell dimensions and reduces the number of strong acid sites in mordenites. Proper dealumination can improve selectivity to 2,6-DIPN from 33 to 61 % and significantly increases 2,6/2,7 ratio. Improved selectivity to 2,6-DIPN upon proper dealumination was attributed to the decrease in mordenite acidity, reduction in unit cell dimension and removal of some strong acid sites. However, neither the change in selectivity nor that in activity is a simple function of dealumination degree or SiO 2 /Al 2 O 3 ratio. Some minor difference in the apparent framework SiO 2 /Al 2 O 3 ratio can result in a major difference in activity or selectivity. There exist optimum conditions of dealumination as well as optimum reaction conditions for achieving higher selectivity to 2,6-DIPN. Version française abrégée – Synthèse respectueuse de l'environnement du 2,6-diisopropylnaphtalène par isopropylation du naphtalène catalysée par la mordénite par effet de sélectivité de forme. Le développement récent de matériaux polymères tels que les polyéthylènes naphthalates, polybutylènes naphthalates et les polymères à cristaux liquides a créé une demande importante en 2,6-dialkylnaphthalène. Ceci a accru l'intérêt pour l'alkylation sélective de forme du naphthalène. Ce travail décrit l'isopropylation du naphtalène catalysée par la mordénite pour produire du 2,6-diisopropylnapthalène (2,6-DIPN). Les effets de la déalumination de la mordénite, sur les caractéristiques structurales, l'acidité, aussi bien que sur les réactions catalytiques d'alkylation (la sélectivité de forme et l'activité) ont été étudiés par les différentes techniques d'analyses, TDP, RMN solide du silicium et de l'aluminium. Les centres Al octaédriques et Al tetraédriques sont éliminés par déalumination, réduisant ainsi les dimensions de la maille cristalline et le nombre de sites à forte acidité de la mordénite. Ceci entraı&#x0302;ne, dans des conditions de déalumination bien choisies, une augmentation de la sélectivité en 2,6-DIPN de 33 à 61 % et du rapport 2,6-DIPN/2,7-DIPN. Cependant, aucune corrélation simple entre la variation de la sélectivité et de l'activité avec le degré de déalumination n'a pu être établie. Les conditions optimales varient pour chaque mordénite.