Rotating bed reactors completely avoid grinding of molecular sieves
Photos showing how grinding caused by stirring of molecular sieves can be completely avoided by using a rotating bed reactor (RBR). Molecular sieves contained in a RBR for a 200 mL vessel can theoretically hold 0.23 moles of water. This allows synthesis of product in the range of 100 gram by ester condensation or drying of 25 litres of analytical grade organic solvent.
Conditions: Molecular sieve (3 Å, rods 3-5 mm, 15 g), placed either into a SpinChem® S221 rotating bed reactor (RBR) or free in solution agitated by a 3-blade stainless steel propeller (5 cm), both operated at 500 rpm within a SpinChem® V211 flower-baffled reaction vessel containing isopropanol (130 mL). Photos were taken after 24 hours of operation with the RBR and stirrer in place, respectively. The theoretical calculation assumed an RBR with space for 20 g molecular sieve with a 20% (w/w) water adsorption capacity, a synthesis yield of 99%, a product weight of 450 g/mol, and an organic solvent with a density of 0.8 kg/L and an initial moisture content of 200 ppm; data partly taken from literature; J. Org. Chem. 2010 (75) 8351-8354.