Stable poly (ionic liquids) with unique cross‐linked mesoporous‐macroporous structure as efficient catalyst for alkylation of o‐xylene and styrene

• Published in: Applied organometallic chemistry 2019-08, Vol.33 (8), p.n/a
• Main Authors: Sheng, Xiaoli, Gao, Huaying, Zhou, Yuming, Wang, Beibei, Sha, Xiao
• Format: Article
• Language: English
• Subjects: Alkylation; Anion exchanging; Catalysis; catalyst; Catalysts; Cations; Chemistry; cross‐linked polymer; Divinylbenzene; Ionic liquids; Ions; mesoporous‐macroporous structure; Monomers; poly acidic (ionic liquids); Polymerization; Specific surface; Styrenes; Surface area; Thermal stability; Xylene
• ISSN: 0268-2605; 1099-0739
• DOI: 10.1002/aoc.4979

In this work, using divinylbenzene (D), 1‐vinylimidazole (V) and 1‐vinyl‐3‐butylimidazolium bromide ([VBIM][Br]) as monomers, the binary‐monomer poly (ionic liquids) (PILs) and ternary‐monomer PILs were successfully synthesized, via hydrothermal polymerization and anion exchange, sequentially. Compared with each other, the ternary polymeric acidic IL catalyst has a clear spongy porous structure, while having a more stable macroporous structure, a larger specific surface area, more acidic groups and more active sites. Catalytic performance of catalyst was investigated through the alkylation of o‐xylene and styrene. The effect of the amount of IL added and the length of the cation chain on the ternary polymerization of acidic IL was systematically investigated. Under optimal reaction conditions (molar ratio of monomers was D:V:[VBIM][Br] = 2:1:1, the most suitable cation chain length was C4), the synthesized MPD‐[C4V]‐[VBIM][SO3CF3] has a larger specific surface area (89.47 m2/g), large pore volume (0.29 cm3/g), and abundant mesopores and macropores, which help to improve the contact between the active site and reactants. Moreover, the catalyst could maintain a relatively high conversion of styrene (99.0%), 1,2‐diphenylethane yield (98.7%) and high thermostability under reaction and be easily be divided from the solution, which is critical for heterogeneous solid catalysts. Using divinylbenzene (D), 1‐vinylimidazole (V) and 1‐vinyl‐3‐butylimidazolium bromide ([VBIM][Br]) as monomers, the binary‐monomer and ternary‐monomer poly ionic liquids were successfully synthesized via free‐radical polymerization and ion exchange. In comparison, the ternary polymeric acidic ionic liquid has a clear spongy porous structure, while having a more stable macroporous structure, a larger specific surface area, more acidic groups, and more active sites. The results show that the synthesized MPD‐[C4V]‐[VBIM][SO3CF3] has more activity when the molar ratio of raw materials is D:V:[VBIM][Br]=2:1:1.