Novel process windows - Concept, proposition and evaluation methodology, and intensified superheated processing

摘要

The concept of novel process windows has recently been proposed by Hessel (2009) and his major processing variant, the pressurised superheated processing, is the topic of several recent reviews in the field. Different from process intensification and micro-process technology enhancing mass and heat transfer to reveal intrinsic kinetics, novel process windows aim at speeding up kinetics, i.e. dramatically reducing reaction time. This idea is taken up more and more in micro-process technology, but origins as well from the encased processing practised since longer in microwave organic chemistry. Novel process windows as highly intensified processing approach tends to fully exploit the kinetics (reactivity) while maintaining selectivity at an acceptable level through use of harsh conditions, rather than to domesticate chemistry that is common practice in the process chemistry of the past. Reaction rates can be accelerated by orders of magnitude and reaction times shrink from hours to minutes and seconds. The accompanied large increase in productivity is a further cornerstone in making micro-process technology a competitive concept as opposed to the economics of scale, practised since decades in production chemistry aiming at increasing the vessel size more and more. Different to the content provided in recent reviews, this compilation focuses on the process chemistry potential of superheated processing (while still providing a short summary on the other processing options), a methodology how to find novel processing conditions and how to evaluate these. Two reactions, the Swern-Moffatt oxidation and the Claisen rearrangement, are discussed in detail, since these are ideal candidates for high-temperature investigations due to their eminent synthetic importance and well-known kinetics. As a practical reaction example with industrial guidance of a running European Project, the epoxidation of vegetable oils, the new methodology is exemplified beyond the level of the organic chemists' descriptions given so far.