University of Oldenburg, Germany
Title: How are wastes entirely avoided in solid-state productions?
Biography: Gerd Kaupp
The top "waste management" requires entire avoidance of wastes in chemical manufacture. Thus, processes must run to completion giving pure products not requiring solvents for removal of excess reagents, unwanted side products, or catalysts by solvents for chromatography. Solid-solid and gas-solid syntheses (since 1984) are the techniques of choice, which upon proper milling can be scaled. For example, horizontal Simoloyer® ball-mills from 1 to 900 liters size are suitable and contain all technical requirements for waste-free industrial production. Lab-scale syntheses are preferably tested in double-walled ball-mills with temperature control at the 100 − 200 mg scale. Since the solids shall not melt during milling the suitable temperature below the eutectic one can be found by cooling or (if necessary) by heating (−78 to +120°C). Cooling and avoiding catalysts profits from activation energy decrease in solid-state reactions (including frozen liquids). This advantage is lost upon melting above the eutectic temperature leaving reactions incomplete and unspecific. Virtually all reaction types (also multi-cascade ones) across chemistry with reactive molecular solids, salts, ductile metals, and gases have been waste-free realized, and numerous scaled to 200 g batches, and some of industrial interest scaled to auto-batches (e.g. manufacture of Al + CNT) or continuous technical manufacture. The temperature control and the product-collection is essential and will be discussed in detail. Transfer of milling impact energy to the reacting system is only necessary for direct mechanical breakage of sigma bonds. The Simoloyer® ball-mills are also suitable for true mechanochemistry and for comminution when recycling by leaching.