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Yoshihiro Sugi - One of the best experts on this subject based on the ideXlab platform.
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Shape-Selective Catalysis in the Alkylation of Naphthalene: Steric Interaction with the Nanospace of Zeolites
Journal of nanoscience and nanotechnology, 2015Co-Authors: Yoshihiro Sugi, Ajayan VinuAbstract: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.
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Shape‐Selective Alkylation of Naphthalene over Zeolites: Steric Interaction of Reagents with Zeolites
Journal of the Chinese Chemical Society, 2010Co-Authors: Yoshihiro SugiAbstract:Steric interaction of reagents with zeolites was studied in isopropylation, sec-butylation, and Tert-Butylation of naphthalene (NP) over several large-pore zeolites to elucidate the mechanism of selective catalysis. Selectivities for dialkylnaphthalene (DAN) isomers were influenced by the type of zeolite and bulkiness of alkylating agent. Selective formation of β,β- and 2,6-diisopropylnaphthalene (DIPN) occurred only over H-mordenite (MOR) in the isopropylation of NP using propene; bulky transition states of α,α- and α,β-DIPN are excluded because of steric restriction by the channels, resulting in selective formation of β,β- and 2,6-DIPN. However, low selectivities for β,β- and 2,6-DIPN were observed over the zeolites, SSZ-24 (AFI), SSZ-55 (ATS), and SSZ-42 (IFR) with 12-membered-ring (12-MR) pore entrances of one-dimensional channels, CIT-5 (CFI), UTD-1 (DON), and SSZ-53 (SFH) with 14-membered-ring (14-MR) pore entrances of one-dimensional channels, and Y-zeolite (FAU), zeolite β (BEA), and CIT-1 (CON) with 12-MR pore entrances of three-dimensional channels, because their channels are too large for the exclusion of bulky isomers. Catalysis over these zeolites occurs under kinetic and/or thermodynamic control, resulting in predominant formation of α,α- and α,β-DIPN at lower temperatures and an increase of the stable isomer β,β-DIPN at higher temperatures. 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. In particular, β,β-di-tert-butylnaphthalene (DTBN) was selectively formed in the Tert-Butylation. The selectivities for β,β- and 2,6-DAN were enhanced even in large channels: the transition states of the least bulky isomers only fit the channels because other bulky isomers are excluded by steric restriction of the channels. However, Tert-Butylation over FAU, BEA, and CON had selectivities for 2,6-DTBN of around 50–60%, although selectivities for β,β-DTBN were almost 100% selectivity; these zeolites can hardly recognize the differences between 2,6- and 2,7-DTBN. The results indicate that the fitting of the least bulky isomers to zeolite channels, leading to the exclusion of other bulky isomers, is essential for highly shape-selective catalysis.
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synthetic investigation on mcm 68 zeolite with mse topology and its application for shape selective alkylation of biphenyl
Microporous and Mesoporous Materials, 2008Co-Authors: Tomoko Shibata, Kenichi Komura, Yoshihiro Kubota, Sayaka Suzuki, Hiroaki Kawagoe, Yoshihiro SugiAbstract:Abstract The synthesis of MCM-68 zeolite with MSE topology, which is a three-dimensional zeolite with 12 × 10 × 10 membered ring (MR) channel systems was tuned under the hydrothermal conditions using N , N , N ′, N ′-tetraethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium diiodide as SDA, and applied for the isopropylation of biphenyl (BP). The H + form zeolite (SiO 2 /Al 2 O 3 =26) was obtained by the ion-exchange of as-synthesized sample (SiO 2 /Al 2 O 3 = 20) after the calcination, and the zeolites with SiO 2 /Al 2 O 3 = 70–263 were prepared by the dealumination of calcined sample (SiO 2 /Al 2 O 3 = 20) by 1 N hydrochloric acid. Catalytic activities in the isopropylation of BP were enhanced by the dealumination of MCM-68 zeolite, and maximized at SiO 2 /Al 2 O 3 = 70. However, further dealumination accompanies the decrease in the catalytic activity. The selectivity for 4,4′-diisopropylbiphenyl was ca 75–80% for all MCM-68 zeolites at moderate temperatures up to 300 °C. These high selectivities are due to restricted transition state mechanism inside the 12-MR straight channels: BP cannot easily enter into the 10-MR channels and cages of the zeolites. The selectivity for 4,4′-di- sec -butylbiphenyl and 4,4′-di- tert -butylbiphenyl improved in sec -butylation and tert -butylation of BP compared to the isopropylation. The exclusion of bulky isomers was enhanced by increasing the bulkiness of the alkylating agents.
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The alkylation of naphthalene over three-dimensional large pore zeolites: The influence of zeolite structure and alkylating agent on the selectivity for dialkylnaphthalenes
Catalysis Today, 2008Co-Authors: Yoshihiro Sugi, Kenichi Komura, Hiroyoshi Maekawa, Yukio Hasegawa, Hiroaki Naiki, Yoshihiro KubotaAbstract:Abstract In order to elucidate how zeolite structure and alkylating agent play roles in the shape-selective catalysis, the alkylation, i.e. , isopropylation, sec -butylation, and tert -butylation, of naphthalene (NP) was examined over three-dimensional twelve-membered (12-MR) zeolites, Y (FAU), Beta (BEA), and CIT-1 (CON), and compared to that of H-mordenite (MOR). The β,β-selectivities (for β,β-dialkylnapthalene (β,β-DAN)) and the 2,6-selctivities (for 2,6-dialkylnaphthalene (2,6-DAN)) among DAN isomers varied with the types of zeolites and alkylating agents. FAU, BEA, and CON gave only low selectivities for 2,6-diisopropylnaphthalene (2,6-DIPN) in the isopropylation, and predominant isomers were bulky and thermodynamically unstable α,β-DIPN (1,3-, 1,6-, and 1,7-DIPN) and α,α-DIPN (1,4- and 1,5-DIPN) at lower temperatures, and the formation of the less bulky and thermodynamically stable β,β-DIPN (2,6- and 2,7-DIPN) increased with increasing the temperature: they have quite different features from the shape-selective catalysis over MOR. These results suggest that FAU, BEA, and CON are not shape-selective in the isopropylation, and that the isopropylation is principally controlled kinetically at lower temperatures, and thermodynamically at higher temperatures. The β,β-selectivities over FAU, BEA, and CON increased with increasing the bulkiness of alkylating agents, and were almost 100% in the tert -butylation. On the other hand, the 2,6-selectivities over these zeolites were much lower than those over MOR at a typically moderate temperature, 250 °C. These results mean that FAU, BEA, and CON have the shape-selective nature to give the less bulky isomers, β,β-DAN, in the sec -butylation and tert -butylation by using bulkier alkylating agents, particularly 2-methyl-2-propene: they can differentiate β,β-DAN from their isomers at the transition states by the steric restriction of zeolite channels. However, the channels of these zeolites are too large for differentiating 2,6- and 2,7-DAN even with 2-methyl-2-propene.
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Tungstophosphoric acid supported on MCM-41 mesoporous silicate: An efficient catalyst for the di-Tert-Butylation of cresols with tert-butanol in supercritical carbon dioxide
Applied Catalysis A: General, 2006Co-Authors: Gunda Kamalakar, Kenichi Komura, Yoshihiro SugiAbstract:Abstract Tungstophosphoric acid (HPW) supported on MCM-41 mesoporous silicate was an excellent catalyst for the tert -butylation of cresols in supercritical CO 2 . The tert -butylation of p -cresol gave 2,6-di- tert -butyl-4-methylphenol (2,6-DTBPC) in high yield (the best yield: 58%) in supercritical CO 2 ; however, zeolites, H-Y and H-beta, gave only 2- tert -butyl-4-methylphenol (2-TBPC) because of their limitation in pore size. The yield of 2,6-DTBPC over HPW(30)/MCM-41 was maximum at 110 °C, and further increase in temperature decreased the yield. There was the optimal CO 2 pressure on the yield of 2,6-DTBPC at 10 MPa, and further increase of the pressure resulted in rapid decrease in the yield. Thermogravimetric analysis of used catalysts showed that the deactivation is minimized in supercritical CO 2 compared to the other reaction media such as hexane as solvent and without solvent under N 2 atmosphere. HPW(30)/MCM-41 was recyclable without significant loss of catalytic activity, and retained mesoporous structure even after three recycles. The tert -butylation of o - and m -cresols over HPW(30)/MCM-41 gave the 2,4-di- tert -butyl-6-methylphenol, 2,4-di- tert -butyl-5-methylphenol, respectively, in good to moderate yields.
Nikunj Bhatt - One of the best experts on this subject based on the ideXlab platform.
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Solvent-free liquid phase Tert-Butylation of m-cresol using a solid acid catalyst comprising H4SiW12O40 and neutral Al2O3
Reaction Kinetics and Catalysis Letters, 2008Co-Authors: Nikunj Bhatt, Anjali PatelAbstract:Liquid phase Tert-Butylation of m-cresol was carried out using 12-tungstosilicic acid supported on neutral alumina by varying different parameters. The reaction has also been carried out by using calcined samples under optimized conditions. The present catalyst shows an excellent activity of 93.2%, conversion of 100% selectivity for the o-isomer, an important industrial product.
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Solvent-free liquid phase Tert-Butylation of m-cresol using a solid acid catalyst comprising H_4SiW_12O_40 and neutral Al_2O_3
Reaction Kinetics and Catalysis Letters, 2008Co-Authors: Nikunj Bhatt, Anjali PatelAbstract:Liquid phase tert -butylation of m -cresol was carried out using 12-tungstosilicic acid supported on neutral alumina by varying different parameters. The reaction has also been carried out by using calcined samples under optimized conditions. The present catalyst shows an excellent activity of 93.2%, conversion of 100% selectivity for the o-isomer, an important industrial product.
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Fresh and calcined supported 12-tungstosilicicacid: Synthesis, characterization and application to some acid catalyzed reactions
Journal of Molecular Catalysis A-chemical, 2007Co-Authors: Nikunj Bhatt, Anjali Patel, Parasuraman Selvam, Kalpesh SidhpuriaAbstract:Abstract A series of catalyst containing 20–70% of 12-tungstosilicicacid (TSA) supported onto neutral alumina (A) has been synthesized, characterized and evaluated for esterification of 1° and 2° alcohols. The best catalyst, TSA 3 /A (30% loading of 12-tungstosilicicacid onto neutral alumina) has been compared with TSA 3 /Z (30% loading of 12-tungstosilicicacid onto hydrous zirconia) in order to see the effect of nature of support. The catalytic activity of TSA 3 /A and TSA 3 /Z has also been explored for tert -butylation of phenol by varying different parameters. Both the catalysts were calcined in the temperature range of 300–500 °C and characterized by FT-IR, DRS and XRD to see the structural change in the calcined materials. Their catalytic activity was also evaluated for the esterification as well as tert -butylation of phenol under optimized conditions. An attempt has also been made to regenerate and to reuse the present catalysts, especially for tert -butylation of phenol.
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Liquidphase Tert-Butylation of cresols catalysed by 12-tungstophosphoricacid and 12-tungstosilicicacid supported onto neutral alumina
Catalysis Letters, 2007Co-Authors: Nikunj Bhatt, Anjali PatelAbstract:A comparative study on tert -butylation of cresols such as o-cresol, m-cresol and p-cresol with tert-butyl alcohol was carried out over 30% 12-tungstophosphoricacid and 12-tungstosilicicacid supported onto neutral alumina in liquid phase under mild conditions. The catalysts show high activity in terms of % conversion and % selectivity for the products, p - tert butyl o -cresol, o - tert butyl m -cresol, o - tert butyl p -cresol, under mild conditions.
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Fresh and calcined supported 12-tungstosilicicacid: Synthesis, characterization and application to some acid catalyzed reactions
Journal of Molecular Catalysis A: Chemical, 2007Co-Authors: Nikunj Bhatt, Anjali Patel, Parasuraman Selvam, Kalpesh SidhpuriaAbstract:A series of catalyst containing 20-70% of 12-tungstosilicicacid (TSA) supported onto neutral alumina (A) has been synthesized, characterized and evaluated for esterification of 1 degrees and 2 degrees alcohols. The best catalyst, TSA(3)/A (30% loading of 12-tungstosilicicacid onto neutral alumina) has been compared with TSA(3)/Z (30% loading of 12-tungstosilicicacid onto hydrous zirconia) in order to see the effect of nature of support. The catalytic activity of TSA(3)/A and TSA(3)/Z has also been explored for Tert-Butylation of phenol by varying different parameters. Both the catalysts were calcined in the temperature range of 300-500 degrees C and characterized by FT-IR, DRS and XRD to see the structural change in the calcined materials. Their catalytic activity was also evaluated for the esterification as well as Tert-Butylation of phenol under optimized conditions. An attempt has also been made to regenerate and to reuse the present catalysts, especially for Tert-Butylation of phenol. (c) 2007 Elsevier B.V
Anjali Patel - One of the best experts on this subject based on the ideXlab platform.
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Solvent-free liquid phase Tert-Butylation of m-cresol using a solid acid catalyst comprising H4SiW12O40 and neutral Al2O3
Reaction Kinetics and Catalysis Letters, 2008Co-Authors: Nikunj Bhatt, Anjali PatelAbstract:Liquid phase Tert-Butylation of m-cresol was carried out using 12-tungstosilicic acid supported on neutral alumina by varying different parameters. The reaction has also been carried out by using calcined samples under optimized conditions. The present catalyst shows an excellent activity of 93.2%, conversion of 100% selectivity for the o-isomer, an important industrial product.
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Solvent-free liquid phase Tert-Butylation of m-cresol using a solid acid catalyst comprising H_4SiW_12O_40 and neutral Al_2O_3
Reaction Kinetics and Catalysis Letters, 2008Co-Authors: Nikunj Bhatt, Anjali PatelAbstract:Liquid phase tert -butylation of m -cresol was carried out using 12-tungstosilicic acid supported on neutral alumina by varying different parameters. The reaction has also been carried out by using calcined samples under optimized conditions. The present catalyst shows an excellent activity of 93.2%, conversion of 100% selectivity for the o-isomer, an important industrial product.
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Fresh and calcined supported 12-tungstosilicicacid: Synthesis, characterization and application to some acid catalyzed reactions
Journal of Molecular Catalysis A-chemical, 2007Co-Authors: Nikunj Bhatt, Anjali Patel, Parasuraman Selvam, Kalpesh SidhpuriaAbstract:Abstract A series of catalyst containing 20–70% of 12-tungstosilicicacid (TSA) supported onto neutral alumina (A) has been synthesized, characterized and evaluated for esterification of 1° and 2° alcohols. The best catalyst, TSA 3 /A (30% loading of 12-tungstosilicicacid onto neutral alumina) has been compared with TSA 3 /Z (30% loading of 12-tungstosilicicacid onto hydrous zirconia) in order to see the effect of nature of support. The catalytic activity of TSA 3 /A and TSA 3 /Z has also been explored for tert -butylation of phenol by varying different parameters. Both the catalysts were calcined in the temperature range of 300–500 °C and characterized by FT-IR, DRS and XRD to see the structural change in the calcined materials. Their catalytic activity was also evaluated for the esterification as well as tert -butylation of phenol under optimized conditions. An attempt has also been made to regenerate and to reuse the present catalysts, especially for tert -butylation of phenol.
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Liquidphase Tert-Butylation of cresols catalysed by 12-tungstophosphoricacid and 12-tungstosilicicacid supported onto neutral alumina
Catalysis Letters, 2007Co-Authors: Nikunj Bhatt, Anjali PatelAbstract:A comparative study on tert -butylation of cresols such as o-cresol, m-cresol and p-cresol with tert-butyl alcohol was carried out over 30% 12-tungstophosphoricacid and 12-tungstosilicicacid supported onto neutral alumina in liquid phase under mild conditions. The catalysts show high activity in terms of % conversion and % selectivity for the products, p - tert butyl o -cresol, o - tert butyl m -cresol, o - tert butyl p -cresol, under mild conditions.
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Fresh and calcined supported 12-tungstosilicicacid: Synthesis, characterization and application to some acid catalyzed reactions
Journal of Molecular Catalysis A: Chemical, 2007Co-Authors: Nikunj Bhatt, Anjali Patel, Parasuraman Selvam, Kalpesh SidhpuriaAbstract:A series of catalyst containing 20-70% of 12-tungstosilicicacid (TSA) supported onto neutral alumina (A) has been synthesized, characterized and evaluated for esterification of 1 degrees and 2 degrees alcohols. The best catalyst, TSA(3)/A (30% loading of 12-tungstosilicicacid onto neutral alumina) has been compared with TSA(3)/Z (30% loading of 12-tungstosilicicacid onto hydrous zirconia) in order to see the effect of nature of support. The catalytic activity of TSA(3)/A and TSA(3)/Z has also been explored for Tert-Butylation of phenol by varying different parameters. Both the catalysts were calcined in the temperature range of 300-500 degrees C and characterized by FT-IR, DRS and XRD to see the structural change in the calcined materials. Their catalytic activity was also evaluated for the esterification as well as Tert-Butylation of phenol under optimized conditions. An attempt has also been made to regenerate and to reuse the present catalysts, especially for Tert-Butylation of phenol. (c) 2007 Elsevier B.V
Kalpesh Sidhpuria - One of the best experts on this subject based on the ideXlab platform.
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Fresh and calcined supported 12-tungstosilicicacid: Synthesis, characterization and application to some acid catalyzed reactions
Journal of Molecular Catalysis A-chemical, 2007Co-Authors: Nikunj Bhatt, Anjali Patel, Parasuraman Selvam, Kalpesh SidhpuriaAbstract:Abstract A series of catalyst containing 20–70% of 12-tungstosilicicacid (TSA) supported onto neutral alumina (A) has been synthesized, characterized and evaluated for esterification of 1° and 2° alcohols. The best catalyst, TSA 3 /A (30% loading of 12-tungstosilicicacid onto neutral alumina) has been compared with TSA 3 /Z (30% loading of 12-tungstosilicicacid onto hydrous zirconia) in order to see the effect of nature of support. The catalytic activity of TSA 3 /A and TSA 3 /Z has also been explored for tert -butylation of phenol by varying different parameters. Both the catalysts were calcined in the temperature range of 300–500 °C and characterized by FT-IR, DRS and XRD to see the structural change in the calcined materials. Their catalytic activity was also evaluated for the esterification as well as tert -butylation of phenol under optimized conditions. An attempt has also been made to regenerate and to reuse the present catalysts, especially for tert -butylation of phenol.
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Fresh and calcined supported 12-tungstosilicicacid: Synthesis, characterization and application to some acid catalyzed reactions
Journal of Molecular Catalysis A: Chemical, 2007Co-Authors: Nikunj Bhatt, Anjali Patel, Parasuraman Selvam, Kalpesh SidhpuriaAbstract:A series of catalyst containing 20-70% of 12-tungstosilicicacid (TSA) supported onto neutral alumina (A) has been synthesized, characterized and evaluated for esterification of 1 degrees and 2 degrees alcohols. The best catalyst, TSA(3)/A (30% loading of 12-tungstosilicicacid onto neutral alumina) has been compared with TSA(3)/Z (30% loading of 12-tungstosilicicacid onto hydrous zirconia) in order to see the effect of nature of support. The catalytic activity of TSA(3)/A and TSA(3)/Z has also been explored for Tert-Butylation of phenol by varying different parameters. Both the catalysts were calcined in the temperature range of 300-500 degrees C and characterized by FT-IR, DRS and XRD to see the structural change in the calcined materials. Their catalytic activity was also evaluated for the esterification as well as Tert-Butylation of phenol under optimized conditions. An attempt has also been made to regenerate and to reuse the present catalysts, especially for Tert-Butylation of phenol. (c) 2007 Elsevier B.V
Kenichi Komura - One of the best experts on this subject based on the ideXlab platform.
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synthetic investigation on mcm 68 zeolite with mse topology and its application for shape selective alkylation of biphenyl
Microporous and Mesoporous Materials, 2008Co-Authors: Tomoko Shibata, Kenichi Komura, Yoshihiro Kubota, Sayaka Suzuki, Hiroaki Kawagoe, Yoshihiro SugiAbstract:Abstract The synthesis of MCM-68 zeolite with MSE topology, which is a three-dimensional zeolite with 12 × 10 × 10 membered ring (MR) channel systems was tuned under the hydrothermal conditions using N , N , N ′, N ′-tetraethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium diiodide as SDA, and applied for the isopropylation of biphenyl (BP). The H + form zeolite (SiO 2 /Al 2 O 3 =26) was obtained by the ion-exchange of as-synthesized sample (SiO 2 /Al 2 O 3 = 20) after the calcination, and the zeolites with SiO 2 /Al 2 O 3 = 70–263 were prepared by the dealumination of calcined sample (SiO 2 /Al 2 O 3 = 20) by 1 N hydrochloric acid. Catalytic activities in the isopropylation of BP were enhanced by the dealumination of MCM-68 zeolite, and maximized at SiO 2 /Al 2 O 3 = 70. However, further dealumination accompanies the decrease in the catalytic activity. The selectivity for 4,4′-diisopropylbiphenyl was ca 75–80% for all MCM-68 zeolites at moderate temperatures up to 300 °C. These high selectivities are due to restricted transition state mechanism inside the 12-MR straight channels: BP cannot easily enter into the 10-MR channels and cages of the zeolites. The selectivity for 4,4′-di- sec -butylbiphenyl and 4,4′-di- tert -butylbiphenyl improved in sec -butylation and tert -butylation of BP compared to the isopropylation. The exclusion of bulky isomers was enhanced by increasing the bulkiness of the alkylating agents.
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The alkylation of naphthalene over three-dimensional large pore zeolites: The influence of zeolite structure and alkylating agent on the selectivity for dialkylnaphthalenes
Catalysis Today, 2008Co-Authors: Yoshihiro Sugi, Kenichi Komura, Hiroyoshi Maekawa, Yukio Hasegawa, Hiroaki Naiki, Yoshihiro KubotaAbstract:Abstract In order to elucidate how zeolite structure and alkylating agent play roles in the shape-selective catalysis, the alkylation, i.e. , isopropylation, sec -butylation, and tert -butylation, of naphthalene (NP) was examined over three-dimensional twelve-membered (12-MR) zeolites, Y (FAU), Beta (BEA), and CIT-1 (CON), and compared to that of H-mordenite (MOR). The β,β-selectivities (for β,β-dialkylnapthalene (β,β-DAN)) and the 2,6-selctivities (for 2,6-dialkylnaphthalene (2,6-DAN)) among DAN isomers varied with the types of zeolites and alkylating agents. FAU, BEA, and CON gave only low selectivities for 2,6-diisopropylnaphthalene (2,6-DIPN) in the isopropylation, and predominant isomers were bulky and thermodynamically unstable α,β-DIPN (1,3-, 1,6-, and 1,7-DIPN) and α,α-DIPN (1,4- and 1,5-DIPN) at lower temperatures, and the formation of the less bulky and thermodynamically stable β,β-DIPN (2,6- and 2,7-DIPN) increased with increasing the temperature: they have quite different features from the shape-selective catalysis over MOR. These results suggest that FAU, BEA, and CON are not shape-selective in the isopropylation, and that the isopropylation is principally controlled kinetically at lower temperatures, and thermodynamically at higher temperatures. The β,β-selectivities over FAU, BEA, and CON increased with increasing the bulkiness of alkylating agents, and were almost 100% in the tert -butylation. On the other hand, the 2,6-selectivities over these zeolites were much lower than those over MOR at a typically moderate temperature, 250 °C. These results mean that FAU, BEA, and CON have the shape-selective nature to give the less bulky isomers, β,β-DAN, in the sec -butylation and tert -butylation by using bulkier alkylating agents, particularly 2-methyl-2-propene: they can differentiate β,β-DAN from their isomers at the transition states by the steric restriction of zeolite channels. However, the channels of these zeolites are too large for differentiating 2,6- and 2,7-DAN even with 2-methyl-2-propene.
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Tungstophosphoric acid supported on MCM-41 mesoporous silicate: An efficient catalyst for the di-Tert-Butylation of cresols with tert-butanol in supercritical carbon dioxide
Applied Catalysis A: General, 2006Co-Authors: Gunda Kamalakar, Kenichi Komura, Yoshihiro SugiAbstract:Abstract Tungstophosphoric acid (HPW) supported on MCM-41 mesoporous silicate was an excellent catalyst for the tert -butylation of cresols in supercritical CO 2 . The tert -butylation of p -cresol gave 2,6-di- tert -butyl-4-methylphenol (2,6-DTBPC) in high yield (the best yield: 58%) in supercritical CO 2 ; however, zeolites, H-Y and H-beta, gave only 2- tert -butyl-4-methylphenol (2-TBPC) because of their limitation in pore size. The yield of 2,6-DTBPC over HPW(30)/MCM-41 was maximum at 110 °C, and further increase in temperature decreased the yield. There was the optimal CO 2 pressure on the yield of 2,6-DTBPC at 10 MPa, and further increase of the pressure resulted in rapid decrease in the yield. Thermogravimetric analysis of used catalysts showed that the deactivation is minimized in supercritical CO 2 compared to the other reaction media such as hexane as solvent and without solvent under N 2 atmosphere. HPW(30)/MCM-41 was recyclable without significant loss of catalytic activity, and retained mesoporous structure even after three recycles. The tert -butylation of o - and m -cresols over HPW(30)/MCM-41 gave the 2,4-di- tert -butyl-6-methylphenol, 2,4-di- tert -butyl-5-methylphenol, respectively, in good to moderate yields.
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Tert-Butylation of Phenol over Ordered Solid Acid Catalysts in Supercritical Carbon Dioxide: Efficient Synthesis of 2,4-Di-tert-butylphenol and 2,4,6-Tri-tert-butylphenol
Industrial & Engineering Chemistry Research, 2006Co-Authors: Gunda Kamalakar, Kenichi Komura, Yoshihiro SugiAbstract:The Tert-Butylation of phenol was carried out over ordered solid acid catalysts (zeolites and MCM-41-supported heteropolyacids and rare-earth-metal triflates) in supercritical CO2. The catalytic performances in supercritical CO2 were superior to those in other reaction media such as liquid-phase and N2 atmosphere conditions. The Tert-Butylation of phenol gave 2,4-di-tert-butylphenol (2,4-DTBP) in 65% yield over H−Y zeolites and 2,4,6-tri-tert-butylphenol (2,4,6-TTBP) in 40% yield over Sc(OTf)3 supported on MCM-41 [Sc(OTf)3/MCM-41]. The coke formation in supercritical CO2 was much lower than that in other reaction media. These high performances are due to the high solubilities of reactants and products and to the minimal coke formation: supercritical CO2 works as the reaction medium; removes coke precursors, which are heavy aromatics from phenol and/or isobutene oligomers, before they convert to coke materials; and keeps the catalytic sites clean during the catalysis. The spatial requirement for catalytic...
