Application of Microstructured Reactor Technology for the Photochemical Chlorination of Alkylaromatics
Keywords:Gas/liquid reaction, Microstructured reactor, Photochlorination
AbstractThe advantageous application of a falling-film microreactor for a photochemical gas/liquid reaction was demonstrated by the selective photochlorination of toluene-2,4-diisocyanate (TDI). In the microstructured reactor the selectivity to the side-chain chlorinated product 1-chloromethyl-2,4-diisocyanatobenzene (1Cl-TDI) achieved a value of 80% at 55% TDI conversion, whereas the side product toluene-5-chloro2,4-diisocyanate (5Cl-TDI) was formed with only 5% selectivity. The yield of 1Cl-TDI was enhanced by increasing the residence time from 24% after 5 s to 54% after 14 s. At the same time the formation of consecutive products increased and the selectivity to 1Cl-TDI decreased to 67% after 14 s residence time. The influence of the reactor material was shown. In presence of a Lewis acid such as FeCl3, formed by chlorination using a reaction plate made of iron, consecutive products were formed and the selectivity to 1Cl-TDI was lowered. The microstructured reactor led to remarkably higher selectivities than the conventional batch reactor, where the selectivity to 1Cl-TDI was only 45% at 65% TDI conversion and the side product 5Cl-TDI was formed with 50% selectivity. The space-time yield of 1Cl-TDI achieved in the microstructured reactor (400 mol l?1 h?1) clearly exceeded the performance of the batch reactor (space-time yield 1.3 mol l?1 h?1). Based on the microreactor data, a kinetic model for the TDI chlorination including by-product formation was suggested and used to predict product selectivity at full TDI conversion.
How to Cite
H. Ehrich, D. Linke, K. Morgenschweis, M. Baerns, K. Jähnisch, Chimia 2002, 56, 647, DOI: 10.2533/000942902777680063.
Copyright (c) 2002 Swiss Chemical Society
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