The Alkylation of Biphenyl over Fourteen-Membered Ring Zeolites. The Influence of Zeolite Structure and Alkylating Agent on the Selectivity for 4,4′-Dialkylbiphenyl

Abstract

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.

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

“…A more precise fitting of the transition state with the zeolites, however, was required for the recognition of 2,6-DTBN, even with bulky alkylating agents. Similar results of shape-selective catalysis were observed in alkylation of BP over the zeolites examined in this paper: 21,32,33 the selectivities for 4,4¢-dialkylbiphenyl …”

Alkylation of Biphenyl over Zeolites: Shape-Selective Catalysis in Zeolite Channels

“…These mechanisms are keys to achieving highly shapeselective catalysis in the alkylation of BP [5,7,[11][12][13]. In particular, it is important that molecular dimensions of reactants and products can precisely fit zeolite pores and channels.…”

“…These controls work under sterically less hindered conditions. 4,4 0 -DIPB, the least bulky isomers, appears as the principal product by shape-selective catalysis only under appropriate steric controls by zeolite channels [5,7,[11][12][13][14][15][16][17][18][19][20][21].…”

“…We examined the isopropylation of BP over zeolites with different structures [11][12][13][14][15][16][17][18][19][20][21]. Figure 6 shows the effects of reaction temperature on the isopropylation over SSZ-24 (AFI), SSZ-55 (ATS), UTD-1 (DON), and FAU with SiO 2 /Al 2 O 3 : 202, 160, 200, and 30, respectively, as typical examples of zeolites [12][13][14]. They have different channel structures: one-dimensional straight channels of 12-MR pore entrances for AFI, one-dimensional corrugated channels of 12-MR pore entrances for ATS, one-dimensional straight channels with 14-MR pore entrances for DON, and three dimensional channels of 12-MR entrances with super cages for FAU [37].…”

“…However, large pore zeolites with three-dimensional channels of 12-MR pore entrances, such as Y zeolite (FAU) and zeolite b (BEA) afford non-selective products with the low selectivities for 4,4 0 -DIPB [13,14]. The bulky alkylating agents, such as 1-butene and 2-methylpropene, enhanced the selectivities for 4,4 0 -dialkylbiphenyl (4,4 0 -DAB): 4,4 0 -disec-butylbiphenyl (4,4 0 -DSBB) in the sec-butylation and 4,4 0 -di-tert-butylbiphenyl (4,4 0 -DTBB) in the tert-butylation, respectively, with the increase in the interaction with the channels even over large pore zeolites [11][12][13].…”