Alkylation Of Naphthalene Research Articles

Selectivity of large pore zeolites in the alkylation of naphthalene with tert-butyl alcohol: analysis of experimental results by computational modelling

Liquid phase alkylation of naphthalene with tert-butanol has been studied using HY and H-beta zeolites with varying silicon to aluminium ratios. Both series of zeolites underwent efficient activities and high selectivities for the mono- and di-( tert-butyl) derivatives. In all cases, 2-( tert-butyl)naphthalene (2-TBN) was the only monoalkylated product (100%,β-selectivity). Over H-beta zeolites, 2-TBN was obtained as the main product with relatively small amounts of dialkylated compounds. Over HY samples, a 2,6-di( tert-butyl)naphthalene (2,6-DTBN) selectivity up to 84% was obtained, with a 2,6-DTBN/2,7-DTBN ratio of 5.6–5.9 and β,β′-selectivity (2,6-+2,7-) of 98–99%. This constitutes the first published observation of such high β,β′ selectivity and 2,6-/2,7- ratio in the liquid phase alkylation of naphthalene. In order to understand such a differentiation in the formation of the two di-( tert-butyl)naphthalenes over the HY zeolites, computational analysis of both energies and molecular dimensions of these derivatives and of the monoalkylated counterparts has been performed, using quantum mechanics (AM1 and PM3) and molecular mechanics (MM +) methods. The energy calculations are in agreement with the experimental results regarding the selective formation of the β and β,β′ isomers. The determination of the kinetic diameters shows that, in their most stable conformation, 2,6-DTBN has a smaller kinetic diameter (7.1 Å) than 2,7-DTBN (7.5 Å), which may explain the selective formation of the 2,6-isomer against the 2,7- within the faujasite framework.

Molecular Electrostatics, Energetics, and Dynamics of the Alkylation of Naphthalene: Positional Isomerization of Monoalkylnaphthalenes at Hartree−Fock and Correlated Levels with BSSE Corrections

The energetics and dynamics of the protonation of the naphthalene molecule were investigated at the Hartree- Fock (HF) and correlated levels. Calculations at correlated levels reproduced the experimental gas-phase proton affinity and basicity of naphthalene quite well. Positional isomerizations of monoalkylnaphthalenes were studied at various theoretical levels. The calculated thermodynamic equilibrium compositions at correlated levels are in good agreement with the experimental results. According to the calculations, intramolecular shifts are possible for the methyl, ethyl, and isopropyl groups. By contrast, the bulky tert-butyl group transfers exclusively intermolecularly. In accordance with the experimental results, the activation energies of the 1,2- alkyl shifts decrease with the increase in the size of the alkyl group. This indicates that the rate-determining step of the isomerization reactions is the rearrangement of the monoalkylnaphthalenium ions via 1,2-alkyl shifts. An intermolecular methyl group transfer between two naphthalene molecules is energetically much less favored than the relevant intramolecular one. However, an appropriate basis set superposition error correction to the total energy of the three-body transition state complex is of utmost importance at secondorder Moller-Plesset level.

ChemInform Abstract: Alkylation of Naphthalene and Toluene by Ethylene in Naphthalene/Alkali Metal Systems in THF

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Isopropylation of naphthalene over modified HMCM-41, HY and SAPO-5 catalysts

The alkylation of naphthalene with isopropanol was carried out over modified MCM-41, HY and SAPO-5 catalysts. The catalysts were characterized by XRD, IR, sorption techniques and temperature programmed desorption of ammonia. The yields of 2-isopropylnaphthalene were 32.1, 47.2 and 52.6 wt.% at 74.7, 55.9 and 81.0% conversion over HMCM-41, CeMCM-41 and LaKY, respectively. The yields of 2,6-diisopropyl naphthalene were in the range of 8 to 35.3%.

Sodium-potassium synergism in the alkylation of toluene and naphthalene with ethene in C10H8−Na−K systems in THF

Sodium-potassium synergism in the alkylation of toluene and naphthalene with ethene in naphthalene-alkali metal systems in THF was discovered. In the case of toluene, the maximum synergistic effect is observed at an Na∶K molar ratio of 1∶1. With this Na∶K molar ratio, the yields of the products of toluene alkylation with ethene considerably increase. The efficiency of naphthalene alkylation (in the presence of toluene) is also markedly enhanced on replacement of sodium or potassium by their mixture.

Alkylation of naphthalene and toluene by ethylene in naphthalene/alkali metal systems in THF

Alkylation of naphthalene and toluene by ethylene in naphthalene/alkali metal systems in THF

99/00390 Catalytic synthesis of high-value chemicals and materials from coal

This paper gives an account of the authors` recent experimental studies on catalytic synthesis of value-added organic chemicals, monomers for advanced polymer materials, and graphitic materials. Not only does carbon dominate the elemental composition of coal, but for most coals the major fraction of that carbon is already in aromatic structures. Thus coal may be a better feedstock for aromatic chemicals than alternative feedstocks in which much of the carbon is aliphatic. Liquids derived from coal carbonization, gasification (tar) and liquefaction contain numerous aromatic compounds. Many of the 1 to 4-ring aromatic and polar compounds can be converted into valuable chemicals. The authors will demonstrate in this paper that high-value chemicals can be obtained from aromatic compounds by shape-selective catalytic conversion over certain zeolite catalysts. They are studying shape-selective alkylation of naphthalene, shape-selective isopropylation of biphenyl, ring-shift isomerization of phenanthrene derivatives into anthracene derivatives, shape-selective hydrogenation of naphthalene, and conformational isomerization of decahydronaphthalene. The products of such selective reactions are intermediates for making value-added chemicals, monomers of advanced polymer materials, or components of advanced jet fuels. Furthermore, catalytic graphitization of anthracites has also been studied. The results demonstrates that using some metal compounds promote the graphitization, but the nature ofmore » the metal is less important.« less

Shape-selective Isopropylation of Naphthalene over Hydrogen-Mordenite Catalysts. Effect of Mordenite Dealumination.

An increasing demand for 2,6-dialkylnaphthalene 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 At species as well as tetrahedral At species, decrease the unit cell dimensions, and reduce 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 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 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.

Liquid-phase alkylation of naphthalene by isopropanol over zeolites. Part 1: HY zeolites

The title reaction has been studied on various HY-based catalysts. Surface acidity has been evaluated by adsorption microcalorimetry and FTIR analysis, using pyridine as probe molecule. Catalytic tests were carried out at 623 K and 40 bar in liquid phase, with decalin as solvent, in flow reactor. Isopropylation is accompanied by oligomerisation/cracking of the reactant alcohol, cracking of the solvent, isomerization of the products of the main reaction. Pore filling by coke is fast for non-dealuminated HY, where naphthalene conversion remains high due to the occurrence of transalkylation between polyisopropylnaphthalenes trapped in the pores and naphthalene; this does not occur on dealuminated HY, owing to the low density of the acid sites and the presence of a secondary mesoporous system which allows easy diffusion of the reaction products in the zeolite pores.

Zeolite HNU-87 : synthesis, characterization and catalytic properties in the shape-selective conversion of methylnaphthalenes

The synthesis of the high-silica zeolite NU-87 and its physicochemical characterization are reported. The catalytic properties of zeolite HNU-87 were investigated in the conversion of 1- and 2-methylnaphthalene. Both isomerization to the corresponding methylnaphthalene and transalkylation to naphthalene and dimethylnaphthalenes are observed. The influence of reaction temperature and the modified residence time on the product distributions is reported and discussed in terms of shape selectivity effects in the peculiar pore system of NU-87. For comparison, typical results obained with zeolite HMCM-22, which possesses a similar pore architecture, are also included. The results of methylnaphthalene conversion over HNU-87 are compared to those obtained in the alkylation of naphthalene with methanol on the same zeolite catalyst.

Unusual results in the liquid phase alkylation of naphthalene with isopropyl alcohol over zeolite H-beta

Unexpected compounds are formed with high selectivity in the liquid phase alkylation of naphthalene with isopropyl alcohol over large pore zeolite H-beta; these have been confirmed to be cyclized products from naphthalene derivatives.

Evidence of transalkylation during liquid-phase isopropylation of naphthalene

The alkylation of naphthalene with isopropanol was investigated over a HY (Si/Al=4) zeolite under the following conditions: flow reactor, liquid phase with decalin as solvent, 623 K, 40 bar. Despite complete filling of the zeolite pores by coke during the first hour of reaction, the rate of formation of isopropylnaphthalene remained very high. This is due to the development of a new reaction process involving transalkylation between the polyisopropyl naphthalenes entrapped in the pores and naphthalene followed by the realkylation of the former compounds with isopropanol.

5629463 Naphthalene alkylation with RE and mixed H/NH3 form catalyst

5629463 Naphthalene alkylation with RE and mixed H/NH3 form catalyst

Liquid phase selective alkylation of naphthalene with t-butanol over large pore zeolites

Liquid phase alkylation of naphthalene with t-butanol has been studied using HY and H-beta zeolites with varying silicon to aluminum ratios. Over both series of zeolites,2-( t-butyl)naphthalene (2-TBN) was observed as only monoalkylated product. Up to 84%2,6-di( t-butyl)naphthalene (2,6-DTBN) selectivity with β,β′-selectivity (2,6-+2,7-) 98–99% and2,6-/2,7- ratios from 5.6 to 5.9 were obtained on silica rich HY zeolites HY(20) and HY(6) under mild reaction conditions (160°C, 2 h reaction). H-beta zeolites show selective effect only for the formation of 2-TBN. For the different zeolites, the activity order isHY(20)≈HY(6)>H-beta(26)≈H-beta(13)>HY(2.5), while the selectivity to 2,6-DTBN stands in the orderHY(20)≈HY(6)>HY(2.5)>H-beta(26)≈H-beta(13). Kinetic parameters (temperature, t-butanol/naphthalene ratio) influencing the reaction were investigated using HY zeolites. Higher temperatures than 160°C cause a decrease in 2,6-DTBN selectivity due to secondary reactions; large t-butanol/naphthalene ratio results in lower activity, possibly caused by counter diffusion effect. The results show that alkylation of naphthalene with t-butanol should be much practical attractive not only because of the high activity, 2,6-DTBN selectivity and relatively mild reaction conditions but also due to an easy separation of the desired product (2,6-DTBN) from the reaction mixtures by crystallization.

Synthesis of mesoporous zeolites and their application for catalytic conversion of polycyclic aromatic hydrocarbons

Three series of mesoporous aluminosilicate (Al-MCM-41) samples were synthesized using different aluminum sources including aluminum isopropoxide, pseudo boehmite and aluminum sulfate. Their catalytic activities were tested in the conversion of aromatic hydrocarbons including hydrocracking of 1,3,5-triisopropylbenzene, alkylation of naphthalene, and hydrogenation of naphthalene and phenanthrene. The three series of Al-MCM-41 samples behaved differently in acting as acidic catalysts and as supports. The Al-MCM-41 synthesized using aluminum isopropoxide was found to be the most promising acidic catalyst and good support for Pt catalyst.

Selective dialkylation of naphthalene with hindered alkylating agents over HM and HY zeolites under liquid phase conditions

Liquid-phase alkylation of naphthalene with cyclohexyl derivatives as alkylating agents has been studied over HM and HY zeolites. The reaction can be carried out efficiently over HY zeolites, for which high conversions and good selectivities in 2,6- and 2,7-dicyclohexyl naphthalenes (DCN) are obtained after very short reaction times. The ratio 2,6-DCN/2,7-DCN is near to 1, as in the case of the isopropylation reaction over the same catalysts. Such a result is in agreement with the values of critical diameters of 2,6- and 2,7-dicyclohexyl and diisopropyl naphthalenes, calculated by molecular mechanics. The 2,6-dicyclohexyl-naphthalene is a crystalline compound which is easily separated from the reaction mixture by crystallization, which constitutes an interesting advantage of cyclohexylation in comparison with isopropylation.

Alkylation of naphthalene with alcohols over mesoporous MCM-41

Mesoporous MCM-41 is found to promote alkylation of naphthalene by alcohols. In addition to the preferred branched side chain productsn-alkylated product is also observed in the case of propylation of naphthalene.

Selective alkylation of naphthalene with tert-butyl alcohol over large pore zeolites

HY zeolites exhibit high activity and selectivity for 2,6-di-(tert-butyl)naphthalene in the liquid phase alkylation of naphthalene with tert-butyl alcohol; moreover, the desired 2,6-isomer is easily separated from the reaction mixture by crystallization.

Shape-selective alkylation of naphthalene with isopropanol over large pore zeolites

Isopropylation of naphthalene was carried out over various zeolites such as USY, H-beta, H-mordenite, and ZSM-5. A non-microporous catalyst, fluorinated resin, was also included for comparison. The influence of the zeolite structure and reaction parameters was studied for this reaction. A high β,β- and 2,6-selectivity was observed with twelve-member ring zeolite. Under the reaction conditions, 1 atm, 200°C, with a feed of naphthalene:isopropanol:cyclohexane=1:2:10 (mole ratio) and space velocity WHSV = 3.02h −1, 92% naphthalene conversion and a β,β-selectivity of 90% was obtained with USY catalyst. In any case, USY zeolite exhibits the highest activity and stability of all the catalysts. Although the selectivity to 2,6-diisopropylnaphthalene on USY is somewhat less than those on H-beta and H-mordenite, its high activity and stability can overcome this weak point. For USY, the reaction temperature of 200°C gives the highest naphthalene conversion.

Shape-selective alkylation of naphthalene with isopropanol over mordenite catalysts

Naphthalene alkylation with isopropanol was studied at 250°C using several proton-form mordenites (HM) and Y-zeolites. HM catalysts afforded 2-isopropylnaphthalene (2-IPN) as the dominant product, whereas the Y-zeolites (HY and LaHY) gave 1-IPN as a major product. HM displayed better selectivity to 2-IPN and 2,6-diisopropylnaphthalene (2,6-DIPN), although HY showed higher activity for naphthalene conversion. HM catalysts with SiO 2/Al 2O 3 ratios of 20–35 appear to be effective for shape-selective synthesis of 2-IPN and 2,6-DIPN. These catalysts displayed over 73% β-selectivity to 2-IPN among the two IPN isomers, and over 65% β,β′-selectivity to the desired 2,6-DIPN among all DIPN isomers with 2,6-DIPN/2,7-DIPN ratios of about 3. The isopropanol-to-naphthalene ratios and the solvent type are also influential for both activity and selectivity of mordenite catalysts.