AbstractsChemistry

The first part of this study is concerned with setting up a reactive distillation process for production of tert-amyl-methyl ether (TAME). This work was linked to the development of etherification technology of Neste Oy. TAME production makes possible to upgrade some low value olefinic components to high value gasoline. Moreover, it has a significant impact in the reduction of the air pollution caused by the cars by introducing oxygen to the gasoline. However at the time of the study, there was no technology available for production of that component. Reactive distillation (RD) had been applied successfully to the production of the tert-butyl-methyl-ether (MTBE). Thus it seemed worth of trying to apply RD to TAME production as well. The actual work of setting up the process was accomplished using a simulation model of a reactive distillation column. Arrangement of the column and conditions of the experimental runs were determined with the model developed earlier by Aittamaa and Kettunen (1993). The pilot run was successful, so that ethers could be produced as planned and experiments verified with the existence of the operating regimes predicted by the model. The results of this study had a significant impact on the development of the highly successful NExTAME and NExETHERS technologies, even if the final solution was based on the Side Reactor Concept (SRC), i.e. a combination of a distillation column and a reactor connected to the column via side streams, rather than on RD. The second part is the development of a rate-based model of a reactive distillation column including the effects of incomplete lateral mixing on the trays. Most published tests with RD have been performed with small pilot or bench scale columns. In such columns vapour and liquid mixing is nearly complete. However, that is not the case in large industrial columns. On the other hand, making tests with reactive system in columns having diameter of two meter or more is very expensive and practically impossible for most research institutions. Not only the sheer size and utility consumption of such devices are large, but the feed and product volumes are huge even for a short run. With non-reacting systems it is often possible to recycle the products back to the feed, but when reaction takes place, that is much more difficult. If lateral mixing is suspected to have importance in some particular case, a mathematical model is probably the only viable way to estimate its significance before the full-scale plant is built. Two different models for the effects of the lateral concentration profiles on reactive distillation trays were developed. The first model is an eddy diffusion model, the other one is a mixed pool model of reactive distillation trays. The basic principles of both models are known already earlier but both include novel features. Similar models have not been applied earlier to the reactive distillation. The eddy diffusion equations are solved simultaneously and rigorously with the other equations of the equation group describing the…