Isopropylation Of Naphthalene Research Articles

The isopropylation of naphthalene over ordered mesoporous aluminosilicate AlSBA-1: The formation of diisopropylnaphthalene and triisopropylnaphthalene isomers

We report on the catalytic activity of ordered mesoporous aluminosilicate, AlSBA-1 with 3D cage type porous structure, in the isopropylation of naphthalene (NP). The higher isopropylates: triisopropylnaphthalene (TriIPN) and tetraisopropylnaphthalene (TetIPN) isomers were formed over AlSBA-1 in addition to isopropylnaphthalene (IPN) and diisoprpylnaphthalene (DIPN) isomers. The higher isopropylates were started to form at 225 °C as primary products, which were produced by multi-step isopropylation from NP occurred during one stay on the catalytic site cooperated with the propene adsorbed neighbor acid sites. TriIPN isomers were composed of four isomers (1,3,7-. 1,3,5-, 1,3,6-, and 1,4,6-) formed from DIPN isomers. These formations of TriIPN isomers are controlled by the distribution of DIPN isomers. β,β-DIPN isomers lead to α,β,β-TriIPN isomers, and α,α-DIPN to α,α,β-TriIPN, respectively. However, α,β-DIPN isomers give both of α,α,β- and α,β,β-TriIPN isomers depending on the reaction conditions. The distribution of TriIPN isomers is operated by their kinetic and thermodynamic properties. Bulky and unstable α,α,β-TriIPN isomers (1,3,5- and 1,4,6-) were predominant at low temperatures, 175–250 °C, and at low NP/Cat ratio at 250 °C, where the catalysis mainly proceeded under kinetic control. However, the formation of slim and stable α,β,β-TriIPN isomers (1,3,7- and 1,3,6-) increased with raising the temperatures, and was primary at 300 °C, where the catalysis occurred under thermodynamic control. From these results, it is concluded that the isopropylation of NP over AlSBA-1 occurs under kinetic and/or thermodynamically controls based on the reactivity of the reactants and the stability of the products, and no steric control concerns by mesopores.

The Isopropylation of Naphthalene over H-MCM22 (MWW): The Formation of Triisopropylnaphthalenes

Abstract The isopropylation of naphthalene (NP) was carried out over H-MCM-22 (MWW), and the isomer distribution of the isopropylates: isopropylnaphthalene (IPN) diisopropylnaphthalene (DIPN), triisopropylnaphthalene (TriIPN), and tetraisopropyl-naphthalene (TetIPN) was investigated. The catalytic results revealed that MWW is very active for their formation of the isopropylates at the reaction temperatures of 175–300 °C. This rapid formation of DIPN, TriIPN, and TetIPN isomers is considered to occur by multi-step isopropylation of NP during one stay on the catalytic site cooperating with the neighbor propene adsorbed sites. TriIPN isomers were the predominant products. Among them, α,β,β-TriIPN (1,3,6- and 1,3,7-) was obtained as major isomers, which are principally formed from α,β- and β,β-DIPN by α- and β-attacks, and α,α,β-TriIPN (1,4,6- and 1,3,5-) were formed as minor isomers. The selectivities for α,β,β-TriIPN isomers were governed by the steric configuration of the side-pockets of MWW: the pockets favored slim and stable 1,3,6- and 1,3,7-TriIPN from α,β- and β,β-DIPN, and bulky and less stable 1,3,5- and 1,4,6-TriIPN from α,α- and α,β-DIPN are disfavored by their steric restriction with side-pockets. The selectivities for TriIPN isomers were almost constant with the change of reaction factors: temperature, period, and catalyst amount. TetIPN isomers also formed in high yield, particularly, by using large amounts of the catalyst. The comparison of H-MCM-22 (MWW) with H-Y (FAU) and H-AlSBA-1 clarified the roles of the side-pockets in the isopropylation of NP.

Substitutional isomerism of triisopropylnaphthalenes in the isopropylation of naphthalene. Assignment by gas chromatography and confirmation by DFT calculation

Substitutional isomerism of triisopropylnaphthalenes in the isopropylation of naphthalene. Assignment by gas chromatography and confirmation by DFT calculation

The isopropylation of naphthalene over a beta zeolite with BEA topology. The selectivity of the products

• Enhanced formation of unstable 1,4,6‐triisopropylnaphthane (1,4,6‐TriIPN) at low temperatures, and the increase of stable 1,3,6‐ and 1,3,7‐DIPN at higher temperatures. • The selectivities for TriIPN isomers keep constant during the reaction without their isomerization. • Enhanced selectivities for β,β‐diisopropylnaphthalene (β,β‐DIPN) in the initial stage of the catalysis. • New type of thermodynamic control favored the stable β,β‐DIPN over fresh catalyst. The isopropylation of naphthalene (NP) was carried out over a BEA zeolite (BEA38; SiO 2 /Al 2 O 3 = 38) focused on the selectivities for diisopropylnaphthalene (DIPN) and triisopropylnaphthalene (TriIPN) isomers. The isopropylation gave possible eight DIPN isomers including β,β- (2,6- and 2,7-), α,β- (1,3-, 1,6-, and 1,7-), and α,α- (1,4- and 1,5-). The catalysis over BEA works two types of controls: kinetic control operates to form predominantly bulky and unstable α,α-DIPN at low temperatures, and thermodynamic controls work for the predominant formation of the slim and stable β,β-DIPN at high temperatures, although the intermediately bulky and stable α,β-DIPN are the major products through both controls. The enhanced selectivities for β,β-DIPN were observed at the early stages of the catalysis in the range of 200−300 °C, which operate under new type of thermodynamic control over fresh catalyst through thermodynamically preferred transition states; however, they decreased with the increase in the selectivities for α,α- and α,β-DIPN, and converged after prolonged reaction period. The isopropylation of DIPN isomers gives TriIPN isomers: unstable and bulky 1,3,5- and 1,4,6-TriIPN with α,α,β-substitution, and stable and slim 1,3,7- and 1,3,6-TriIPN with α,β,β-substitution. The low temperatures favor the former isomers, whereas the selectivity for the latter isomers increases with increasing reaction temperature. These results indicate that TriIPN isomers principally form under kinetic control at low temperatures, and thermodynamic controls participate in the catalysis at high temperatures. The selectivities for TriIPN isomers kept constant during the reaction at all temperatures: 200, 250, and 300 °C. The catalysis occurs inside the BEA channels and allow even the formation of bulky 1,3,5- and 1,4,6-TriIPN; however, all isomers cannot be isomerized to the others in the channels and on the external surfaces. Severe coke-deposition occurred during the catalysis, particularly in the early stages; however, the catalyst is recovered by the calcination with a small change in catalytic activity.

The Isopropylation of Naphthalene over USY Zeolite with FAU Topology. The Selectivities of the Products

Abstract The isopropylation of naphthalene (NP) over USY zeolite (FAU06, SiO2/Al2O3 = 6) gave all eight possible diisopropylnaphthalene (DIPN) isomers: β,β- (2,6- and 2,7-), α,β- (1,3-, 1,6-, and 1,7-), and α,α- (1,4- and 1,5-). The catalyses are operated under kinetic and/or thermodynamic controls depending on the reaction temperatures because the cavities of FAU topology are wide enough to form all DIPN isomers. Enhanced selectivities for β,β-DIPN were observed at the early stages at 200, 250, and 300 °C although the selectivities decreased with the increasing periods, accompanying the increase in α,α- and α,β-DIPN. The enhancement occurs under new types of thermodynamic controls through thermodynamically preferred transition states to β,β-DIPN. Triisopropylnaphthalene (TriIPN) isomers are also formed in the isopropylation. Unstable α,α,β-TriIPN (1,4,6- and 1,3,5-) is predominantly formed at lower temperatures; however, decreased with the increase of stable α,β,β-TriIPN (1,3,6- and 1,3,7-) at higher temperatures. The predominant formation of 1,4,6-TriIPN was also observed in the initial stages in the range of 200, 250 and 300 °C, as reaction period was increased, while the selectivity for the isomer was decreased with concomitant increase in the selectivities for the other isomers. These changes of the selectivities operated under kinetic and/or thermodynamic controls. Large cavities of the zeolite allow the formation of all TriIPN isomers without steric restriction.

Comparison of methanol to gasoline conversion in one-step, two-step, and cascade mode in the presence of H-ZSM-5 zeolite

ABSTRACTIn this report, three technological modes for methanol-to-gasoline reaction in the presence of H-ZSM-5 catalyst are compared: (i) direct methanol transformation to hydrocarbons; (ii) two-step (methanol-dimethyl ether-hydrocarbons); and (iii) cascade pathway. Light hydrocarbon gases (methane, ethylene, propylene, and isobutene) and liquid aromatic hydrocarbons (benzene, toluene, xylene, cresol, durol, naphthalene, methylnaphthalene, ethyl naphthalene, isopropyl naphthalene, methyl isopropyl naphthalene, etc.) were found to be the main reaction products. The experimental results showed that the classical two-step methanol to gasoline (MTG) process nowadays remains the most effective for gasoline-range hydrocarbons production, while one-step and cascade schemes require further investigation and the development of reactor systems as well as the operating conditions. The product distribution of MTG synthesis after 120 h on stream in the case of two-step mode was found to be the following: liquid C6–C8 hydrocarbons – 23%; C1–C5 gaseous products – 65%; heavy C9–C12 hydrocarbons – 10%.

Synthesis of beta zeolite with mesopores from a milk containing precursor and its performance in naphthalene isopropylation

The synthesis of micro-/mesoporous beta zeolite by employing a solid precursor was described and its activity in the isopropylation of naphthalene was tested. The precursor was prepared by spray-drying of a homogenous mixture of silica sol, polyaluminum chloride solution and acidophilus milk, the presence of the latter induced formation of mesopores. The volume of mesopores of the synthesized beta zeolites ranged from 0.13 to 0.6 cm3/g and strongly depended on the concentration of tetraethylammonium hydroxide (TEAOH) in the reaction mixtures at the hydrothermal synthesis. Micro-/mesoporous beta zeolites exhibit positive effects of mesopores on the naphtalene conversion in its isopropylation by isopropyl alcohol, by improving the availability of active sites. With an increasing volume of mesopores, the conversion of naphthalene proportionally increases from 12 up to 27% for the volume of mesopores 0.6 cm3/g, while the selectivity to isopropylnaphthalene decreases from 92 to 55–66% for beta zeolites with 0.15–0.45 cm3 of mesopores/g, followed by selectivity increase up to mesopore volume 0.6 cm3/g reaching 81% at conversion 27%. A yield of isopropylnaphthalene is increasing in the whole range, particularly when the volume of mesopores exceeds 0.4 cm3/g. A zeolite with the highest volume of mesopores provides 1.8 times higher yield of isopropylnaphthalene then a microporous beta zeolite without mesopores. The increasing conversion of naphthalene is accompanied by a decrease in the selectivity to isopropylnaphthalene for zeolites with a low volume of mesopores, but an increasing selectivity to isopropylnaphthalene in the case of zeolites with a volume of mesopores above 0.4 cm3/g. This unusual effect can be explained by the mesoporosity of zeolites. Mesopores improve the availability of active centers, so they react faster, but the by-products are also formed faster and later undesired reactions run more easily as active centers are gradually blocked by by-products. Zeolites with the largest pores provide not only better availability of active centers, but the reaction products can also leave the zeolitic phase more easily and undesirable reactions have less chance to occur. This method of micro/mesoporous beta zeolite synthesis is advantageous for its low cost.

Highly Active and Coke‐Tolerant Hierarchical Mordenite Catalysts Synthesized by Recrystallization for the Isopropylation of Naphthalene

AbstractIn the isopropylation of naphthalene for the production of 2,6‐naphthalenedicarboxylate, the monomer of polyethylene naphthalate plastic, a shape‐selective mordenite (MOR) zeolite catalyst provides the best selectivity for the desired 2,6‐diisopropylnaphthalene. However, the small pore size of the zeolite limits the naphthalene conversion and lowers the stability because of pore‐mouth blocking by coke. We discovered that these problems could be mitigated by synthesizing a micro‐meso hierarchical pore structure in the MOR zeolite by the recrystallization of MOR with cetyltrimethylammonium bromide as a mesopore‐forming surfactant. The recrystallized catalysts allow the facile diffusion of bulky molecules through connected meso‐ and micropores to and from active catalytic sites located in the small MOR pores. Relative to microporous MOR, the hierarchical MOR catalyst demonstrated a greatly enhanced activity, stability, and coke tolerance, and the intrinsic high shape selectivity of MOR for 2,6‐diisopropylnaphthalene was maintained. Mild desilication enlarged the pore volume and formed additional acid sites to increase the activity further.

Lanthanide oxide modified H-Mordenites: Deactivation of external acid sites in the isopropylation of naphthalene

The external surface of the H-Mordenite (MOR) was modified with lanthanide oxides such as CeO2, La2O3, Pr2O3, Sm2O3, Dy2O3, and Yb2O3, to investigate the deactivation of external acid sites. It is confirmed that the modification with the oxides prevents the isomerization of 2,6-diisopropylnaphthalene (DIPN) during the isopropylation of naphthalene (NP). The oxides accumulated on the MOR surface deactivated the acid sites with keeping catalytic activities of the isopropylation when their loadings are in the range of 5–10 wt%; however, the differences in the activities were observed when the loading was increased to 20–30 wt%: CeO2 gave a high activity with a high selectivity for 2,6-DIPN, and Sm2O3 maintained moderate activities, whereas the other oxides lost the activities. The differences of the modified MORs are ascribed to the morphologies of mesopores formed by the accumulation of the oxides. CeO2 is accumulated as segregated nano-sized crystallites, and the pore-entrances of MOR are opened through their mesopores for the access of NP and its products, and the isopropylation occurs in the channels with a high selectivity for 2,6-DIPN without a significant loss of the activities. However, La2O3 is accumulated as amorphous glassy oxide with a low surface area, leading to the loss of the activities by disturbing the access of NP to MOR pores. Further, amorphous glassy Sm2O3 also supports the selective formation of 2,6-DIPN as the mesopores allow the access of NP to MOR channels.

Shape-Selective Catalysis in the Alkylation of Naphthalene: Steric Interaction with the Nanospace of Zeolites.

Steric interaction of reagents with nanospace of zeolites was studied in alkylation: isopropylation, sec-butylation, and tert-butylation of naphthalene (NP) over several large-pore zeolites to elucidate the mechanism of shape-selective catalysis. Selectivities for β,β- and 2,6-dialkylnaphthalene (DAN) were influenced by the type of zeolite and bulkiness of alkylating agent. Shape-selective formation of β,β- and 2,6-diisopropylnaphthalene (DIPN) occurred only over H-mordenite (MOR) in the isopropylation of NP. Bulky α,α- and α,β-DIPN are excluded because of steric restriction at their transition states by the MOR channels, resulting in the selective formation of β,β- and 2,6-DIPN. AFI (SSZ-24) gave also high selectivities for 2,6-DIPN, and CFI (CIT-5) and MSE (MCM-68) gave high selectivities for β,β-DIPN. The lower selectivities for 2,6-DIPN were observed over the zeolites, ATS (SSZ-55), LFR (SSZ-42), DON (UTD-1), SFH (SSZ-53), FAU (Y-zeolite), BEA (zeolite β), and CON (CIT-1). Their channels allow the accommodation of bulky isomers, resulting in the catalysis under kinetic and/or thermodynamic controls. The selectivities for β,β- and 2,6-DAN were enhanced with the increase in bulkiness of alkylating agents: 1-butene for sec-butylation and 2-methylpropene for tert-butylation, even over zeolites with large pores and channels: the transition states of the least bulky isomers only fit the channels, and the other bulky isomers are excluded by steric restriction of the channels. However, tert-butylation over FAU, BEA, and CON had selectivities of around 50-60% for 2,6-DTBN, and almost 100% selectivities for β,β-DTBN. These zeolites cannot recognize the differences between 2,6- and 2,7-DTBN, but they can differentiate β,β-DTBN from the other isomers. The results indicate that the fitting of the least bulky isomers to zeolite channels, resulting in the exclusion of other bulky isomers, is a key for highly shape-selective catalysis.

MOR/SBA‐15 Composite Catalysts with Interconnected Meso/Micropores for Improved Activity and Stability in Isopropylation of Naphthalene

AbstractThe isopropylation of naphthalene with isopropyl alcohol was studied over composites of MOR/SBA‐15 in a high‐pressure, fixed‐bed reactor. The MOR catalyst showed a high 2,6‐/2,7‐diisopropyl naphthalene (DIPN) ratio of 1.75, but a low naphthalene conversion (54 %) and fast deactivation of the catalyst. The composites of MOR/SBA‐15 were prepared by a hydrothermal recrystallization process to obtain hierarchical micro/mesopores. During the process, MOR recrystallized in the mesopores of SBA‐15, the structure of which was stabilized by carbon coating formed on the pore walls as a template. The best prepared MOR/SBA‐15 catalyst achieved a high conversion of 85 %, high stability, and less coking, while maintaining the high 2,6‐/2,7‐DIPN ratio (≈1.8). The modified micro/mesopore structure allowed facile diffusion of bulky molecules to and from active catalytic sites located in the small MOR pores as a result of the connection between the two types of pores in the MOR/SBA‐15 composite.

Characterisation of agarwood type resin of Gyrinops walla Gaertn growing in selected populations in Sri Lanka

Gyrinops walla is the only agarwood producing tree growing in Sri Lanka which is believed to be endemic. Agarwood is valuable resinous heartwood of Thymalaeaceae family. Present study is aimed to identify the characteristics of naturally formed agarwood type resins in G. walla stems. Samples were isolated from trees growing three different location in the wet zone of Sri Lanka. Naturally formed resinous part of wood was solvent extracted and analysed by GCMS. Further, the current study has developed an effective GCMS method to analyse agarwood type resin from G. walla. Tree diameters and the heights varied in the trees samples, which had no effect on resin formation. Resin contents were not significantly different between three populations although the chemical variations were considerably high. Among the 19 constituents identified by GCMS in the agarwood resins, free fatty acids and isopropyl naphthalene, 2-phenylethyl chromone compounds found to be common for most of the G. walla trees tested. Comonly found sesquiterpene compounds from the G. walla resin were Jinkhol, γ-eudesmol, valerenol and valerinal. Similar compounds have been reported in resin from Aquliaria spp. which is the more established source of agarwood. A future study would experiment on artificial resin induction methods and establishing plantations of G. walla to sustain its supply.

The isopropylation of naphthalene with propene over H-mordenite: The catalysis at the internal and external acid sites

The isopropylation of naphthalene (NP) with propene over H-Mordenite (MOR) was studied under a wide range of reaction parameters: temperature, propene pressure, period, and NP/MOR ratio. Selective formation of 2,6-diisopropylnaphthalene (2,6-DIPN) was observed at reaction conditions, such as at low reaction temperature, under high propene pressure, and/or with high NP/MOR ratio. However, the decrease in the selectivities for 2,6-DIPN was observed at reaction conditions such as at high temperature, under low propene pressure, and/or with low NP/MOR ratio. The selectivities for 2,6-DIPN in the encapsulated products were remained high and constant under all reaction conditions. These results indicate that the selective formation of 2,6-DIPN occurs through the least bulky transition state due to the exclusion of the bulky isomers by the MOR channels. The decrease in the selectivities for 2,6-DIPN are due to the isomerization of 2,6-DIPN to 2,7-DIPN at the external acid sites, directing towards thermodynamic equilibrium of DIPN isomers.

Keggin-type phosphotungstic acid supported on mesoporous SiO2–Al2O3 aerogel like beads and their application in the isopropylation of naphthalene

Spherical mesoporous silica–alumina aerogel like beads based on sol–gel technology and the drop wise addition have been synthesized and used as catalyst support for phosphotungstic acid (PWA). Their catalytic performances in the isopropylation of naphthalene with isopropanol were investigated in a batch reactor. It was found that PWA was highly dispersed on the silica–alumina support and their Keggin structure can be retained. In addition, PWA/SiO2–Al2O3 catalyst showed high surface area, both of Lewis acid sites and Bronsted acid sites. Because of having more Bronsted acid sites, silica–alumina supported acid catalysts showed much higher conversion (87.97 %) and selectivity to diisopropylnaphthalenes (41.41 %) and β,β-products (59.82 %) than pure acid and reactive supports in the isopropylation of naphthalene. The catalytic behavior has been discussed in relation with the physical chemical properties of catalysts, reaction and activation temperature and reaction time.

Isopropylation of naphthalene by isopropanol over conventional and Zn- and Fe-modified USY zeolites

Catalytic performances of USY, MOR, and BEA zeolites were compared for the isopropylation of naphthalene by isopropyl alcohol in a high-pressure, fixed-bed reactor. The USY catalyst showed a high conversion of 86% and good stability but a low 2,6-/2,7-DIPN shape selectivity ratio of 0.94. In contrast, over the MOR catalyst, 2,6-DIPN was selectively synthesized with a high 2,6-/2,7-DIPN ratio of 1.75, but low naphthalene conversions and fast deactivation of the catalyst were observed. The USY catalyst was modified by Zn and Fe using the wet impregnation method to enhance the selectivity for 2,6-DIPN. The highest conversion (~95%) and selectivity for 2,6-DIPN (~20%) were achieved with 4% Zn/USY catalyst. It appeared that small metal oxide islands formed in the USY pores to decrease the effective pore size and thus render it mildly shape-selective. Zn loading also decreased the number of strong acid sites responsible for coke formation and increased the number of weak acid sites. The high conversion and stability of Zn-modified catalysts were ascribed to the presence of a suitable admixture of weak and strong acid sites with less coke deposition. The Fe-modified USY catalysts were less effective because the modification increased the number of the strong acid sites.

Impregnated Molecular Sieves as a Catalyst for the Isopropylation of Naphthalene

At refluence temperature, ferric chloride impregnated molecular sieves were prepared by impregnation of FeCl3 through ion-exchanging methods. The above catalysts were characterized by the means of SEM/EDS (scanning electron microscope/energy dispersion spectrometer) and BET. The catalytic properties on isopropylation of naphthalene and effect of reaction conditions were carried out with fixed-bed flow micro-reactor. We obtained the optimum conditions of this reaction. At this condition, the conversion of naphthalene reaches 44.1%, the yield of 2, 6-DIPN is 41.2% and the selectivity of β,β-DIPN is 85.2%.

Shape-Selective Isopropylation of Aromatic Hydrocarbons over H-Mordenite in Supercritical Carbon Dioxide Medium

Abstract The isopropylation of aromatic hydrocarbons isobutylbenzene (IBB), naphthalene (NP), and biphenyl (BP) was examined over H-mordenite (MOR), H-β (BEA), and H-Y (FAU) zeolites in supercritical carbon dioxide (sc-CO2) medium. MOR was only selective for the formation of the least bulky 4-isobutylcumene (4-IBC) in the isopropylation of IBB. In particular, the catalytic activity and selectivity for 4-IBC were enhanced by the dealumination of MOR; MOR with 110 of SiO2/Al2O3 ratio rendered the highest performance; however, the catalytic activity was decreased by further dealumination. Thermogravimetric analyses confirmed the reduction of coke formation on the catalysts in sc-CO2 medium, preventing the deactivation of MOR. Shape-selective formation of the least bulky isomers, 2,6-diisopropylnaphthalene (2,6-DIPN) and 4,4′-diisopropylbiphenyl (4,4′-DIPB), was also observed in the isopropylation of NP and BP over MOR in sc-CO2. sc-CO2 works as an efficient medium to access and/or replace substrates and their products to/from acidic sites in the MOR channels. In particular, the removal of coke precursors from acidic sites on the zeolite is enhanced by the sc-CO2 medium, resulting in decreased coke formation.

ChemInform Abstract: Shape‐Selective Alkylation of Naphthalene over Zeolites: Steric Interaction of Reagents with Zeolites

AbstractReview: 53 refs.

SSZ-60: Synthetic investigation and catalytic application to the alkylation of biphenyl and naphthalene

An aluminosilicate [Al]-SSZ-60 zeolite was prepared through borosilicate [B]-SSZ-60, which was synthesized using cis- and trans- N-ethyl- N-(3,3,5-trimethylcyclohexyl)pyrrolidinium hydroxide ([ETMCHP] +OH −). [B]-SSZ-60 was obtained by using an equimolar mixture of cis-/trans-[ETMCHP] +OH −. Only small amounts of [B]-SSZ-60 were formed in the presence of [ETMCHP] +OH − ( cis/trans ratio = 96/4, 76/24, and 21/79), and a SSZ-60 phase was not observed in the presence of [ETMCHP] +OH − ( cis/ trans = 4/96). [B]-SSZ-60 was aluminated to form [Al]-SSZ-60 with a SiO 2/Al 2O 3 ratio of 163, a surface area of 62.2 m 2/g, and a pore volume of 0.10 mL/g. The zeolite was used in the alkylation of biphenyl (BP) and naphthalene (NP). The selectivity for 4,4′-diisopropylbiphenyl (4,4′-DIPB) was less than 30% at temperatures of 200–300 °C in the isopropylation of BP, and the predominant isomers were 2,x′-DIPB. However, the selectivity for 4,4′-di- sec-butylbiphenyl (4,4′-DSBB) and 4,4′-di- tert-butylbiphenyl (4,4′-DTBB) was 50–60% and 70–80%, respectively in the sec- and tert-butylations. The selectivity for β,β-diisoprpylnaphthalene (β,β-DIPN) was less than 30% in the isopropylation of NP, and predominant isomers were α,β-DIPN and α,α-DIPN. The selectivities for β,β-di- sec-butylnaphthalene (β,β-DSBN) and β,β-di- tert-butylnaphthalene (β,β-DTBN) were enhanced using bulky agents. SSZ-60 channels are too large for shape-selective formation of the least bulky isomers in the isopropylation of BP and NP. The isopropylation occurs under operation of kinetic and/or thermodynamic controls. However, bulky agents enhance the exclusion of bulky product isomers by increasing steric interactions within the channels in the sec- and tert-butylations. These results indicate that the selectivity for the least bulky isomers is determined by the exclusion of bulky transition states by zeolite channels. Thus, the fit of the transition state in zeolite channels is essential for high selectivities.

Isopropylation of naphthalene over H-mordenite, H-Y, and H-beta zeolites: Roles of isopropylnaphthalene isomers

Isopropylation of naphthalene (NP) was examined over H-mordenite (MOR), H-Y zeolite (FAU), and HBeta zeolite (BEA) in order to elucidate roles of isopropylnaphthalene (IPN) isomers during the catalysis. 2-IPN was the predominant isomer over MOR and works as a precursor for the selective formation of β,β-DIPN, particularly, 2,6-DIPN. In contrast, 1-IPN was predominant (with 2-IPN as a minor isomer) over FAU and BEA at low temperatures; dialkylation accompanied by the consumption of 1- and 2-IPN led to predominant formation of α,α- and α,β-DIPN. The formation of β,β-DIPN from 2-IPN was enhanced at higher temperatures. Bulky transition states of 1-IPN in IPN isomers and α,α- and α,β-DIPN among DIPN isomers were hindered by the interaction with MOR channels, resulting in the selective formation of β,β-DIPN, particularly 2,6-DIPN through the less bulky 2-IPN. FAU and BEA allow the formation of α,α- and α,β-DIPN from both of 1- and 2-IPN isomers because their channels are too large to exclude bulky transition states. The catalysis over FAU and BEA occurred under kinetic control at lower temperatures, and thermodynamic control also participates at higher temperatures.