Isopropylation of Naphthalene

Table 4 Isopropylation of naphthalene over typical zeolite...

Effect of the Dealumination of H-Mordenite - The catalytic activities of the isopropylation of naphthalene are not proportional to the acid density and are not enhanced by the dealumination, as is the case of the isopropylation of biphenyl.18,21 22 Figure 9 shows the yields of products and the distributions of... 

Figure 9 Effect of the dealumination of HM on the isopropylation of naphthalene. Reaction conditions naphthalene, 400 mmol HM, 5 g propylene pressure, 0.8 MPa temperature, 250 °C.

We suggest that the selectivity for the isopropylation of naphthalene is explained by restricted transition-state mechanism,68 However, Kikuchi and his co-workers proposed that the selectivity is due to a product selectivity mech-... 

Figure 10 Effect of reaction period on coke deposition in the isopropylation of naphthalene. Reaction conditions were the same as in Figure 9.

It is important to calcine at the appropriate temperature to enhance the deactivation and the catalysis for the ceria-modified HM.50,51 The catalyst calcined at 300 °C had no catalytic activity. The activity for the isopropylation of naphthalene appeared over the catalyst calcined at 450 °C and reached the maximum at 550 °C. However, the activity decreased at a temperature of 700 °C. These results show that calcination at an appropriate temperature is necessary to keep the HM pores open. The selectivity for 2,6-DIPN was as high as 70% over the catalysts regardless of their calcination temperature. These phenomena show that the isopropylation proceeds inside HM pores. This selective deactivation of HM pores was limited to modification with ceria. The modification with other rare-earth metal oxides, such as lanthanum and neodymium oxides, also deactivated the external acid sites but choked the HM pore to result in low catalytic activity. The isomerization of 4,4 -DIPB was also prevented by the ceria modification of HM in the isopropylation of biphenyl.49... 

Isopropylation over HY, HL and Other Zeolites - The catalysis over HY and HL was quite different from that over HM.61 63 The further isopropylation of IPN and DIPN isomers was quite rapid in spite of the higher number of bulky isopropyl groups. The yield of IPN had a maximum value during the initial stage of the reaction, and then decreased with reaction time. At longer periods, the product amounts decreased as follows DIPN > IPN > TrIPN. Because the catalytic activities correlate well with the pore surface areas of the zeolite, the isopropylation occurs predominantly inside the pores. These results indicate that HY and HL have enough space for the isopropylation of naphthalene inside their pores. Naphthalene and its alkylates can easily enter into and diffuse out of the pores. 

Computer-Assisted Screening of Zeolite Catalysts for the Selective Isopropylation of Naphthalene. 

Olah has found perfluoroalkanesulfonic acids, such as perfluorodecanesulfonic acid (PDSA, C10F21SO3H), to be very effective catalysts for regioselective isopropylation of naphthalene (equation 27). 

On the more spacious zeolite HY the isopropylation of naphthalene is faster but the main procucts are mono-, di- and tri-isopropylnaphthalene. 

Scheme 4. Shape-selective isopropylation of naphthalene using hydrogen-mordenite catalyst, and names of important products.

Isopropylation of Naphthalene at 300°C and Cracking of 1,3,5-Triisopropylbenzene at 350°C over H-Mordenites and Cerium Impregnated Mordenite [Sugi et al., 1994a 10m et al., 1995]. 

Horsley, J.A., J.D. Fellmann, E.G. Derouane and C.M. Freeman, Computer-Assisted Screening of Zeolite Catalysts for the Selective Isopropylation of Naphthalene. J. Catal., 1994, 147, 231-240. 

Kim, J.-H., Y. Sugi, T. Matsuzaki, T. Hanaoka, Y. Kubota, X. Tu and M. Matsumoto. Effect of Si02/Al203 Ratio of Mordenite on Isopropylation of Naphthalene with Propylene. Microporous Materials, 1995a, 5, 113-121. 

A. Kato, G. Seo and C. Pak. Cerium Impregnated H-Mordenite as a Catalyst for Shape-Selective Isopropylation of Naphthalene. Selective Deactivation of Acid Sites on the External Surface. Appl. Catal. A General, 1995b, 131, 15-32. 

Moreau, P., A. Finiels, P. Geneste, and J. Solofo. Selective Isopropylation of Naphthalene over Zeolites. J. Catal., 1992, 136,487-492. 

Schmitz, A., and C. Song. Shape-Selective Isopropylation of Naphthalene over Dealuminated Mordenite. Am. Chem. Soc. Div. Fuel Chem. Prepr., 1994, 39 (4), 986-991. 

Song, C. and A. Schmitz. Shape-Selective Isopropylation of Naphthalene over Dealuminated Mordenite. Key Factors Affecting Regioselectivity. Extended Abstracts, Program. 11th Internat. Congress on Catalysis, Baltimore, Maryland, June 30-July 5, 1996, Po-164. 

Isopropylation of Naphthalene over Cerium-Modified H-Mordenite. Stud. Surf. Sci. Catal., 1994a, 84, 1837-1844. 

The latter have been used in the gas phase methylation of naphthalene with methanol [12-14]. Large pore zeolites, such as H-mordenite or H-Y, led to a nonselective methylation of naphthalene, whereas a high p -selectivity was observed with the medium-pore H-ZSM-5. Liquid phase isopropylation of naphthalene with propene [3,15] or isopropylbromide [16] over zeolites was more recently reported. It was found that isopropylation could be carried out efficiently over such catalysts with a good selectivity for the formation of 2-isopropylnaphthalene and 2,6-/2,7-diisopropylnaphthalenes. We especially demonstrated that the use of zeolites modified by silanation of the external surface led to an improvement of the p -selectivity by suppressing the formation of triisopropyl derivatives [16]. 

P-06 - Isopropylation of naphthalene over large pore zeolites... 

AlJ-SSZ-31 was active in isopropylation of naphthalene, however, the selectivity was lower as compared to mordenite. Large pore zeolites viz. ZSM-12, CIT-5, SSZ-31, CIT-5 and HY were compared. CIT-5 and HY were very active, but, less selective. ZSM-12 and SSZ-31 showed better selectivity for 2,6-DIPN than CIT-5 and HY. Mordenite was the best catalyst. 

The selective alkylation of biphenyl and naphthalene is also possible, and is of commercial interest because 4,4 -diisopropylbiphenyl and 2,6-diisopropyl-naphthalene are used in the synthesis of speciality chemicals, for example for application as liquid crystal polymer materials for displays. For these larger molecules, large-pore zeolites such as mordenite give the best performance for isopropylation of naphthalene, introducing shape selectivity to linear (or more linear) dialkylated products over dialkylated products. 

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