(575g) Mesoporous Silica Supported Ionic Liquids Catalyst for the Alkylation of Benzene with 1-Dodecene

Linear
alkyl benzene (LAB), which is a major feedstock for synthetic detergent, is
synthesized via Friedel-Craft alkylation of benezene with 1-dodecene. LAB is
produced industrially over HF or AlCl₃ homogenous catalyst. Yet,
environmental contamination and difficulty in separation are still the concerns
shared by many manufacturers. The urge to solve such problems spurred us to
employ heterogeneous catalyst in this reaction.

Ionic
liquids, with their fine properties, attracted much interest in recent years.
In this work, ionic liquids consisted of Bis[(perfluoroalkyl)sulfonyl]imides
group was synthesized, which contained "weak-coordination" anion group. For the
stable and hydrophobic properties of perfluoroalkyl groups, these kinds of
ionic liquids catalysts exhibited characteristics, which were more durable, safe
and environment-friendly, comparing with HF or AlCl₃(Figure 1 (a)).
Moreover, with Ionic liquids entrapped in the channel of SiO₂, ionic
liquids catalyst were immobilized on ordered mesoporous silica, revealed by TEM
and BET (Figure 1 (b)). After immobilization, the pore size of mesoporous
silica decreases from 6.7nm to 5.5nm, and specific surface area decreases from
751m²/g to 323 m²/g. Larger specific surface area of the
immobilized catalysts created a larger reaction surface which enhanced mass
transfer and diffusion, led to higher catalytic activity. Such catalyst
structures shared properties from both the stability of ionic liquids and high reactivity
of mesoporous zeolites. The study of catalytic behavior proved the immobilized
catalysts to be active and stable over the alkylation of benzene with dodecene.
Dodecene conversion could reach nearly 100% in 1h with 2-LAB selectivity of more
than 50%. With advances in separation and recovery combined with high
selectivity and activity, these catalysts would be promising in industrial
production.

Figure
1. (a) The reusability of the ionic liquid catalyst. (b) Illustration to the
structure of mesoporous silica supported ionic liquids catalyst

*Corresponding
author. Tel.: 86-0571-87953382, 86-0571-87952728

E-mail:
qhzhang@zju.edu.cn
(Qinghua Zhang)