Liquid-phase isopropylation of biphenyl (BP) with propene was studied to understand the acidities resulting from lanthanoid exchanged sodium mordenite (Ln,NaMOR; Ln: La, Ce, Pr, Sm, Dy, and Yb). The acidities of La3+ exchanged sodium mordenite (La,NaMOR) appeared at around 0.6–0.8 exchange calculated from La/3Al molar ratio. Similar acidities appeared with all Ln,NaMORs. The resultant zeolites have Brønsted acidic sites appearing near unsaturated lanthanoid cations. The isopropylation of BP predominantly afforded 4,4′-diisopropylbiphenyl (4,4′-DIPB) among DIPB isomers over all Ln,NaMORs. These catalyses occur on the acidic sites in the channels. The exchanged catalysts had high selectivities for 4,4′-DIPB even at temperatures as high as 300 °C although the selectivities decreased by the isomerization of 4,4′-DIPB over H-mordenite (HMOR) with similar SiO2/Al2O3 ratio. These results indicate the external acid sites are lowly active for the isopropylation of BP and the isomerization of 4,4′-DIPB. The combustion of coke-deposits on Ln,NaMORs, particularly Ce,NaMOR, used for the isopropylation occurred at lower temperatures than that on HMOR because the lanthanoids dispersed in MOR channels work as an oxidation catalyst.
为了了解
镧系元素交换莫代森
钠(Ln,NaMOR;Ln:La、Ce、Pr、Sm、Dy 和 Yb)产生的酸性,对
联苯(BP)与
丙烯的液相异丙基化进行了研究。根据 La/3Al 摩尔比计算,La3+ 交换莫来石
钠(La,NaMOR)的酸度出现在 0.6-0.8 左右。所有 Ln,NaMOR 的酸度都相似。由此产生的
沸石具有布氏酸性位点,出现在不饱和
镧系阳离子附近。在所有 Ln、NaMORs 上,BP 的异丙基化反应主要产生 DIPB 异构体中的 4,4′-
二异丙基联苯(4,4′-DIPB)。这些催化作用发生在通道中的酸性位点上。交换催化剂对 4,4′-DIPB 的选择性很高,即使在高达 300 °C 的温度下也是如此,尽管在具有相似 SiO2/
Al2O3 比率的 H-莫代石(HMOR)上异构化 4,4′-DIPB 时选择性会降低。这些结果表明,外部酸性位点对 BP 的异丙基化和 4,4′-DIPB 的异构化活性较低。用于异丙基化的 Ln、NaMOR(尤其是 Ce、NaMOR)上的焦
炭沉积物的燃烧温度低于 HMOR,这是因为分散在 MOR 通道中的
镧系元素起到了氧化催化剂的作用。