Given a set of three points X1; X2; X3 , the minimumpoint is determined by quadratic interpolationGiven a set of three points X1; X2; X3 , the minimumpoint is determined by quadratic interpolationGiven a set of three points X1; X2; X3 , the minimumpoint is determined by quadratic interpolationGiven a set of three points X1; X2; X3 , the minimumpoint is determined by quadratic interpolationGiven a set of three points X1; X2; X3 , the minimumpoint is determined by quadratic interpolation
GREEN CHEMISTRY Dr Nam T S Phan Faculty of Chemical Engineering HCMC University of Technology Office: room 211, B2 Building Phone: 38647256 ext 5681 Email: ptsnam@hcmut.edu.vn Chapter 4: REACTOR AND GREEN CHEMISTRY As early as the 18th century: Recent Advances Dimensions remain essentially unchanged !!! … and then micro reactors Micro-sized channels Why micro reactors? Safety: levels of risk to operators & neighbouring community are minimized Waste can be minimized • Typically 10-300 μm in diameter • Very high surface / volume ratio, 10 000 – 50 000 m2m-3 • Conventional lab vessels: only 1000 m2m-3 • Flow controlled by syringe pump, HPLC pump, peristaltic pump or electro-osmotic flow • Heat transfer coefficients exceed those of conventional heat exchangers • Significantly high surface-tovolume ratio ặ better heat transfer Mixing times in micro mixers amount to milliseconds (hardly achievable using stirring equipments) • Benefits for multiphase processes 10 But !!! Hazard of explosion on large scale !!! 26 27 Scale-out microwave reactor 28 Continuous flow microwave reactor • Fast heating and cooling minimize reaction byproducts • Advanced temperature and pressure control Run reactions at temperatures up to 200°C, and pressures up to 30 bar • Only relatively small quantities of reactants are moving through the continuous flow reactorỈ avoiding any risk associated with the handling of very large volumes 29 Ultrasound in organic synthesis 30 • Ultrasound waves consist of cycles of compression & expansion Compression ặ positive pressure on liquid Expansion ặ negative pressure on liquid During expansion cycles Ỉ sound wave generates micro bubbles (cavitation bubbles) 31 •Bubbles expand a little more during each E-C cycle ÆReach critical size Æ implode Æ gases & vapours inside bubble are compressed & create a hot spot • Heating / cooling rates: > 109 Ks-1 32 Three different temperature domains, in which peculiar chemical process will occur 33 • Volatile molecules Ỉ enter micro bubbles Ỉ high temperature & pressure break chemical bonds (thermolysis & oxidation) • Low volatility Æ energy from pressure changes / react with radicals generated by solvent sonolysis • High temperatures & pressures by cavitation: advantageous in multitude of common reactions where conventional conditions cannot achieve the same results 34 35 36 37 38 39 40 .. .Chapter 4: REACTOR AND GREEN CHEMISTRY As early as the 18th century: Recent Advances Dimensions