SSZ-60: Synthetic investigation and catalytic application to the alkylation of biphenyl and naphthalene

Abstract

An aluminosilicate [Al]-SSZ-60 zeolite was prepared through borosilicate [B]-SSZ-60, which was synthesized using cis- and trans- N-ethyl- N-(3,3,5-trimethylcyclohexyl)pyrrolidinium hydroxide ([ETMCHP] +OH −). [B]-SSZ-60 was obtained by using an equimolar mixture of cis-/trans-[ETMCHP] +OH −. Only small amounts of [B]-SSZ-60 were formed in the presence of [ETMCHP] +OH − ( cis/trans ratio = 96/4, 76/24, and 21/79), and a SSZ-60 phase was not observed in the presence of [ETMCHP] +OH − ( cis/ trans = 4/96). [B]-SSZ-60 was aluminated to form [Al]-SSZ-60 with a SiO 2/Al 2O 3 ratio of 163, a surface area of 62.2 m 2/g, and a pore volume of 0.10 mL/g. The zeolite was used in the alkylation of biphenyl (BP) and naphthalene (NP). The selectivity for 4,4′-diisopropylbiphenyl (4,4′-DIPB) was less than 30% at temperatures of 200–300 °C in the isopropylation of BP, and the predominant isomers were 2,x′-DIPB. However, the selectivity for 4,4′-di- sec-butylbiphenyl (4,4′-DSBB) and 4,4′-di- tert-butylbiphenyl (4,4′-DTBB) was 50–60% and 70–80%, respectively in the sec- and tert-butylations. The selectivity for β,β-diisoprpylnaphthalene (β,β-DIPN) was less than 30% in the isopropylation of NP, and predominant isomers were α,β-DIPN and α,α-DIPN. The selectivities for β,β-di- sec-butylnaphthalene (β,β-DSBN) and β,β-di- tert-butylnaphthalene (β,β-DTBN) were enhanced using bulky agents. SSZ-60 channels are too large for shape-selective formation of the least bulky isomers in the isopropylation of BP and NP. The isopropylation occurs under operation of kinetic and/or thermodynamic controls. However, bulky agents enhance the exclusion of bulky product isomers by increasing steric interactions within the channels in the sec- and tert-butylations. These results indicate that the selectivity for the least bulky isomers is determined by the exclusion of bulky transition states by zeolite channels. Thus, the fit of the transition state in zeolite channels is essential for high selectivities.