I&EC 50 |
| Michael A Matthews, John W. Weidner, and Inas M AlNashef. Department of Chemical Engineering, University of South Carolina, 301 Main, Columbia, SC 29208 |
| Ionic liquids have recently gained recognition as possible environmentally benign alternative chemical process solvents. They are nonvolatile, and non-flammable. The superoxide ion can be electrochemically generated in RTILs. We have shown that the superoxide ion in RTIL can be used to destroy polyhalogenated aromatic hydrocarbons, which represent a major environmental problem. It can also activate carbon dioxide to give a carboxylating reagent. The superoxide ion was then used to destroy polychlorinated aromatic compounds in RTILs. We also showed that superoxide ion reacts with primary and secondary alcohols to give the corresponding carboxylic acids and ketones, respectively. The yields depend greatly on the structure of the RTIL and its level of purity. When 1-butyl-3-dimethylimidazolium hexafluorophosphate, [bmim][HFP], was used the average yield of benzhydrol to benzophenone was 50%. That is, only half of the electrochemically generated superoxide ion went on to participate in the desired reaction, while the other half reacted with [bmim][HFP] as indicated by the detection of the corresponding ketone. In comparison, when purified 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, [bdmim][HFP] was used the average yield of benzophenone increased to 98%. Equally significant was that no degradation products were detected in this case. The only difference between [bmim][HFP] and [bdmim][HFP] is the additional methyl group in position 2 of the imidazolium ring for the latter. We used electrochemical techniques, particularly, double potential step voltammetry, to determine the pseudo first order rate constant for the reaction between the superoxide ion and primary and secondary alcohols at different temperatures. The activation energy for the reaction was then determined using Arrhenius plot. The vast majority of our results to date have been generated in conventional electrolytic two-compartment cell with fritted glass separating the cathode and anode compartments. We here discuss the design of a novel membrane reactor that will decrease the power requirements for the synthesis. The novel reactor will employ a thin polymer membrane, infiltrated with the RTIL, to separate the anode and cathode compartments. This membrane reactor will serve as a model system for simulating large-scale production aimed at reducing the energy needed for electrolysis.
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Recent Advances in Green Chemistry and Engineering (sponsored by Green Chemistry & Engineering subdivision)
8:30 AM-11:20 AM, Monday, March 29, 2004 Marriott -- Orange County 2, Oral
Division of Industrial and Engineering Chemistry |