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Alkylation, i.e., isopropylation, s-butylation, and t-butylation, of biphenyl (BP) was examined over one-dimensional twelve-membered (12-MR) zeolites: Mordenite (MOR) and SSZ-24 (AFI) with straight channels, and SSZ-55 (ATS) and SSZ-42 (IFR) with corrugated channels. Types of zeolites and alkylating agents highly influenced the selectivities for dialkylbiphenyl (DABP) isomers. Shape-selective formation of 4,4′-diisopropylbiphenyl (4,4′-DIPB) was observed over MOR and AFI; however, ATS and IFR gave 4,4′-DIPB only in low selectivities at 250 °C: 87% over MOR, 60% over AFI, 20% over ATS, and 30% over IFR. The selectivities for 4,4′-di-s-butylbiphenyl (4,4′-DSBB) in the s-butylation were higher than those for 4,4′-DIPB: 95% over MOR, 85% over AFI, 75% over ATS, and 50% over IFR. The t-butylation afforded selectively 4,4′-di-t-butylbiphenyl (4,4′-DTBB) over the zeolites: 96–97% over MOR and AFI, 90% over ATS, and 80% over IFR. These results in the alkylation indicate the exclusion of 4,4′-DABP from other bulky DABP isomers by steric restriction in zeolite channels is an important key for the high shape-selectivity. Even zeolites with large channels, such as ATS and IFR, can have shape-selective nature if the bulky moieties, such as s-butyl and t-butyl groups, are large enough to differentiate the transition state of the least bulky 4,4′-DABP from those of the other isomers inside their channels. The selectivity for 4,4′-DABP decreased at high temperatures in some alkylations: isopropylation over MOR, and s-butylation and t-butylation over MOR, AFI, and ATS. The decreases are due to the isomerization of 4,4′-DABP at external acid sites, because the channels are not large enough for the isomerization of 4,4′-DABP to bulkier 3,4′-DABP. However, the isopropylation over AFI was accompanied by the isomerization of 4,4′-DIPB at external and internal acid sites, because the channels are large enough for the isomerization of 4,4′-DIPB.

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Alkylation, i.e. isopropylation, s-butylation, and t-butylation, of biphenyl (BP) was examined over fourteen-membered ring (14-MR) zeolites, CIT-5, UTD-1, and SSZ-53, in order to elucidate the relationships between structure of zeolites and bulkiness of alkylating agents on the shape-selective catalysis. CIT-5 zeolite (CFI) yielded 4,4′-diisopropylbiphenyl (4,4′-DIPB) in the level of 50–60% in the isopropylation in the range of 150–300 °C. 2,2′-, 2,3′-, and 2,4′-DIPB (2,x′-DIPB) isomers were obtained as the predominant DIPB isomers at lower temperatures, and the formation of 3,4′- and 3,3′-DIPB isomers increased with an increase in the temperature. However, the selectivities were in the level of 10–15% for UTD-1 (DON) and SSZ-53 (SFH) zeolites in the range of 150–350 °C. The s-butylation with 1-butene gave results similar to the isopropylation, although the selectivities for 4,4′-di-s-butylbiphenyl (4,4′-DSBB) were higher than those for 4,4′-DIPB at 250 °C: 80–85% for CFI, 40–50% for DON, and 30–40% for SFH. High selectivity for 4,4′-di-t-butylbiphenyl (4,4′-DTBB) was observed in the t-butylation at 250 °C: 95% for CFI, 90% for DON, and 80% for SFH. These differences are due to the spatial difference in their channels, and also due to bulkiness of alkylating agents, propene, 1-butene, and 2-methylpropene. The selectivity for 4,4′-dialkylbiphenyl (4,4′-DABP) was governed by the exclusion of the bulky DABP isomers at the transition state by steric restriction in the zeolite channels.