(582af) Silicagel Confined Carboxylic Functionalized Imidazolium Salt for One-Step Catalytic Hydration of Ethylene Oxide

Silicagel Confined Carboxylic Functionalized
Imidazolium Salt for One-Step
Catalytic Hydration of Ethylene Oxide

Qian Su, Wei-Guo Cheng and Suo-Jiang
Zhang

Key Laboratory of Green Process and Engineering, Institute of
Process Engineering, Chinese Academy of Sciences, P.O. Box 353, Beijing,
100190, China

*Corresponding author: sjzhang@home.ipe.ac.cn

  Carbon
dioxide (CO₂) fixation has not only eased the concerns on decreasing
fossil energy but also provided a new perspective to solve industrial problems.
Typically, as a main approach to polyester resin raw materials, ethylene glycol
(EG) production is on the way of technical innovation with CO₂
participation. The traditional ethylene oxide (EO) hydration process could be
substituted by two-step process via first fixation of CO₂ into
ethylene carbonate and then release of CO₂ in water for higher EG
selectivity.¹ Inspired by this process wherein CO₂ acts
as an intermediate, from the perspective of atom-economy, the synthesis of EG
might be simplified as one-step catalytic EO hydration with a catalyst
functioning as CO₂ (Scheme 1). Besides, the catalyst could be
further confined for high catalytic selectivity and stability.

Scheme
1 Silicagel
confined DMIC for one-step catalytic hydration of EO into EG

In
this work, we designed a kind of silicagel confined carboxylic functionalized imidazolium
salt (DMIC@Silicagel) with 1,3-dimethyl-imidazolium-2-carboxylate (DMIC) as
catalytic center and silicagel as confined space, and investigated the effect
of confinement and DMIC amounts on catalytic activities for EO
hydration. The results showed that DMIC owned higher catalytic activity than
common ionic liquids and confined space could improve the EG selectivity synergistically
as well as ensure catalyst stability. However, it is not a linear relationship
between the confined amounts of DMIC and their catalytic selectivity for EG
because there exists a balance between reaction and diffusion rate. The key to
control EG selectivity is to adjust the proportion of confined space and DMIC
for fast EO hydration and slow EG movement under proper conditions. This work
reported here provides a molecular level control of the reaction process and
form the basis of CO₂ application in catalysis.

Keywords: CO₂,
confined space, ethylene glycol

References

1.    Zhang
SJ, Sun J, Zhang XC, Xin JY, Miao QQ, Wang JJ. Ionic liquid-based green
processes for energy production. Chemical Society Reviews, 2014, 43:
7838-7869.