Characterization of Mixing Processes Through the Consecutive-Competitive Bromination Of 1,3,5-Trimethoxybenzene

Characterization of Mixing Processes Through the Consecutive-Competitive Bromination Of 1,3,5-Trimethoxybenzene

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Parallel-competitive or consecutive-competitive chemical reactions whose product distributions are influenced by mass transport can be used to characterize mixing processes. Microstructured mixing devices can offer better mixing than conventional devices. The parallel-competitive reactions of 1-naphthol and 2-naphthol with diazotized sulfanillic acid and of iodate and dihydrogen borate with acid have been previously applied to micromixers. The consecutive-competitive bromination of 1, 3, 5-trimethoxybenzene was demonstrated by Bourne and Kozicki in 1977 to be very fast and yielded mixing-sensitive results in a stirred vessel; they obtained a maximum product ratio of 1-bromo-2, 4, 6-trimethoxybenzene to 1, 3-dibromo-2, 4, 6-trimethoxybenzene of 9.7 in a stopped flow apparatus. Bourne and Kozicki used a gas chromatographic analytical system that required several processing steps prior to analysis. The consecutive-competitive bromination of 1, 3, 5-trimethoxybenzene has been applied to static flow mixer devices described in this thesis. Mesoscale and microscale devices were tested. The bromination reaction was sensitive to mixing in all mixers tested. The best micromixer gave 1-bromo-2, 4, 6-trimethoxybenzene to 1, 3-dibromo-2, 4, 6-trimethoxybenzene product ratios up to 100. The devices were also characterized using the parallel-competitive reaction of iodate and dihydrogen borate with acid. Both reactions were able to characterize the mixers with stable results at room temperature. The iodide/iodate method required multiple concentration ranges to characterize all mixers, whereas the bromination reaction method was able to characterize all mixers at a single concentration. Both methods suffer from material limitations. Bromine is not compatible with metals and reacts with methanol in the presence of light, and iodine may stick to or clog glass or fluorinated polymer devices. An alternative analytical method based on high performance liquid chromatography has been established for the bromination reaction method. This alternative method can analyze reaction mixtures without additional processing. Property data useful for the establishment of the bromination reaction method for characterizing mixing devices have also been measured, including melting points, infrared spectra, ultraviolet/visible spectra, powder x-ray diffraction patterns, and solubilities.The TMB solution mass flow rate and solution density were measured with a Coriolis mass flow meter (Endress aamp; Hauser, Promass 63). The bromine feed system was constructed of polytetrafluoroethylene (PTFE). The bromine solutions wereanbsp;...


Title:Characterization of Mixing Processes Through the Consecutive-Competitive Bromination Of 1,3,5-Trimethoxybenzene
Author:Kristin Hecht
Publisher:Western Engineering, Inc. - 2007-05-13
ISBN-13:

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