The isopropylation of biphenyl over H-mordenite - Roles of 3- and 4-isopropylbiphenyls

다국어 초록 (Multilingual Abstract)

The isopropylation of biphenyl (BP) and 3- and 4-isopropylbiphenyls (3- and 4-IPBPs) was examined over H-mordenites (MOR) to elucidate the mechanism of shape-selective formation of 4,4'-diisopropylbiphenyl (4,4'-DIPB).
The isopropylation of BP occurred predominantly to form 4-isopropylbiphenyl (4-IPBP) from BP and 4,4'-DIPB from 4-IPBP. However, 3-IPBP, a minor isomer from BP, cannot participate effectively in the formation of 3,4'-DIPB due to steric restriction of its isopropyl moiety with MOR channels. Selective formation of 4,4'-DIPB was observed at low to moderate temperatures: 225-275 oC. However, the selectivities for 4,4'-DIPB were decreased at high temperatures,300-350 oC under propene pressure, 0.8MPa, by the isomerization of 4,4'-DIPB at external acid sites. The isomerization of 4,4'-DIPB occurred under low propene pressure even at 250 oC. The roles of 3- and 4-IPBPs in the formation of DIPB isomers were examined in the isopropylation of their mixtures. 4-IPBP was consumed much faster than 3-IPBP in all cases examined. 4-IPBP was an exclusive precursor to DIPB isomers, particularly 4,4'-DIPB. 4,4'-DIPB was also found as a predominant isomer in encapsulated products at all conditions examined. These results show that 4-IPBP can preferentially establish active transition state with propene and acid site in MOR channels, resulting in selective formation of 4,4'-DIPB. It is concluded that the isopropylation of BP over MOR occurs through reactant selectivity mechanism and restricted transition state mechanism, but not through product selectivity mechanism.

참고문헌 (Reference)

1 S. M. Csicsery, 4 : 202-, 1984

2 P. B. Venuto, 2 : 297-, 1994

3 Y. Sugi, 189 : 251-, 1999

4 T. Matsuda, 83 : 295-, 1994

5 Y. Sugi, 5 : 43-, 2001

6 Y. Sugi, 53 : 263-, 2010

7 T. Matsuzaki, 4 : 413-, 1989

8 T. Matsuda, 131 : 215-, 1995

9 Y. Sugi, 304 : 22-, 2009

10 Y. Sugi, 31 : 3-, 1996

11 G. S. Lee, 2 : 243-, 1989

12 N. Sakamoto, "Jpn. Tokkyo Kokai Koho, 88-122635"

13 Y. Sugi, "Catalysis, a Specialist Periodical Report, 13" Royal Soc. Chem. 55-, 1997