(23g) Life Cycle Assessment of Microreaction Technology Versus Conventional Batch Technology

The pros and cons of microreaction technology were investigated using a life cycle assessment (LCA) method. The ecological advantages associated with the transfer of a chemical synthesis from a macro-scale discontinuous batch process to a continuous micro-scale set-up were researched. The two-step production of m anisaldehyde from m-bromo anisole was taken as an example reaction. This lithium-organic synthesis, due to its highly exothermic behavior, can only be carried out under significant safety precautions and high cooling energy consumption in conventional batch reaction equipment. We analyzed two scales of producing m-anisaldehyde, the laboratory scale and the industrial scale, to get in-depth information about possible ecological advantages of microreaction technology. On the one hand the reaction was carried out in a discontinuous 10 L double-wall reactor as well as in the continuous Cytos® Lab System. One the other hand we compared the synthesis of m-anisaldehyde in a 400 L vessel, cooled down to 193 K by evaporating liquid nitrogen, and in the continuous Cytos® Pilot System at T = 273 K. The results of the LCA, expressed as environmental impact potentials, clearly indicate significant ecological advantages achieved with the continuous synthesis in the microreactor. This outcome can be clearly related to the savings in energy consumption, the reduction of solvents, and (in the case of laboratory scale) the increase of reaction yield in the microreactor. Compared to these saving potentials, the fabrication of reactors, thermostats, distillation units etc. only plays a minor role. Upon frequent exchange of microreactors, toxicity potentials, resulting from the stainless steel production, become increasingly important. These toxicity potentials surmount in certain cases those of the alternative discontinuous process.