One-step embedding method for immobilized bifunctional and alkaline ionic liquids as effective catalysts applied in transesterification
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Lei
Shi
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Abstract
Ionic liquids (ILs) have shown good catalytic properties in transesterification reactions, but there is still the drawback of a homogeneous state that requires high energy consumption to separate. Therefore, it is very important to acquire an efficient heterogeneous catalyst that can be applied in industrial manufacture. Herein, we propose a novel attempt to immobilize 1-ethyl-3-methylimidazole imidazolium ([Emim]Im) ILs into silica by a one-step embedding method to synthesize a series of [Emim]Im@SG-A solid catalysts. A large specific surface area of silica with a mesoporous structure can be obtained from the hydrolysis of tetraethyl orthosilicate (TEOS) catalyzed by [Emim]Im. The catalytic performance was evaluated by the transesterification of dimethyl carbonate (DMC) with ethanol (EtOH) in a fixed-bed reactor, and the cause of catalyst deactivation was analyzed. In addition, the mechanism of TEOS hydrolysis promoted by [Emim] Im as well as transesterification over [Emim]Im@SG-A was investigated. For comparison, a similar catalyst [Emim]Im/SiO2 was prepared by an impregnation method. The results indicated that, among the as-prepared catalysts, [Emim]Im@SG-A12 exhibited the best catalytic performance with 49.0% DMC conversion and 39.0% ethyl methyl carbonate (EMC) yield under optimal reaction conditions. In addition, the results revealed that [Emim]Im can efficiently promote the hydrolysis of TEOS and enhance the transesterification of DMC with EtOH. This research provides a promising method to immobilize ILs and is enlightening for acquiring a heterogeneous catalyst.
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