Electric field-induced mobilisation of multiphase solution systems based on the nitration of benzene in a micro reactor

This paper describes the electric field-induced flow characteristics of mul tiphase solutions in a micro reactor device using the nitration of benzene as a model process. Photolithographic and wet etching techniques were used to fabricate the micro reactor (channels, 200 mum id, 100 mum deep) in a bo rosilicate glass substrate. The results focus specifically on the flow para meters of reagents/reactants (i.e., voltage, solution concentration and pH ranges and current-voltage relationships) used in this study. The benzene w as introduced and mobilised by electroosmotic flow (EOF), as a microemulsio n using an appropriate surfactant (sodium dodecyl sulfate), whilst the nitr onium ions, produced in situ from mixed H2SO4-HNO3 (the nitrating agent), u nderwent electrophoretic-induced (electrokinetic) mobility. A co-surfactant , butan-1-ol, was used owing to (a) its relative solubility in the aqueous surfactant solution. (b) its ability to aid the solubilization of benzene, (c) the provision of a water-rich (oil-in-water) rather than oil-rich (wate r-in-oil) microemulsion system and (d) its lack of significant adverse effe cts on the EOF. The optimum conditions used for the nitration of benzene wi thin the micro reactor were a run of the microemulsion as main reagent stre am, then three 30 s segmented injections of mixed acid, with a 5 s push of the microemulsion into the system after each injection, and then a 60 s sto pped-flow reaction time before driving reaction product segments to a colle ction reservoir.