The Alkylation of Biphenyl over One-Dimensional Twelve-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 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.

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 …”

“…Dealuminated H-mordenite (MOR) enhanced shape-selective formation of the smallest 2,6-diisopropylnaphthalene (2,6-DIPN) and 4,4¢-diisopropylbiphenyl (4,4¢-DIPB) in the isopropylation of NP [7][8][9][10][11][12][13][14][15][16][17][18] and BP, [19][20][21][22][23][24] respectively. On the other hand, large-pore zeolites, such as Y zeolite (FAU) and zeolite b (BEA), resulted in only low selectivities in isopropylation of NP 11,[16][17][18]25,[27][28][29][30] and BP, [27][28][29][30]31,33 and the selectivities increased in alkylation of NP 25,[34][35][36][37] and BP 32,[38][39][40] even over these zeolites by the use of bulky alkylating agents. It is interesting how zeolite channels influence catalysis, particularly steric interaction of the transition state, in the alkylation of NP and BP.…”

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].…”

“…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].…”