Multi-injection microstructured reactor for intensification of fast exothermic reactions: proof of concept

Julien Haber, Bo Jiang, Thomas Maeder, Albert Renken, Lioubov Kiwi-Minsker
2013 Green Processing and Synthesis  
Quasi-instantaneous exothermic reactions lead to the formation of unwanted hot spots even when carried out in conventional microstructured reactors (MSR) with tube diameter of 100-1000 μm. For this reason, alternative MSR designs are warranted to enable process intensification of fast reactions with characteristic reaction times < 1 s. The continuous multi-injection MSR, where one of the reactants is successively added to the main flow of reactants along reactor length, may improve temperature
more » ... ontrol. The latter was studied first theoretically using numerical simulations and then experimentally with the cyclisation of pseudoionone to αand β-ionones as a model reaction. The multi-injection MSR made of low temperature co-fired ceramics (LTCC) led to a yield of α-ionone and β-ionone > 0.98 reaching a 500-fold process intensification as compared to the conventional semibatch process. The temperature profiles monitored by quantitative infrared thermal imaging confirmed an 8-fold reduced temperature rise compared to adiabatic temperature rise, which was achieved by injecting the reactants at three different injection points. Nomenclature c Concentration [mol/m 3 ] c p Heat capacity [J/(kg K)] d Diameter [m] d h Hydraulic diameter [m] E A Activation energy [J/mol] F Process intensification factor [-] H Channel height [m] H r Reaction enthalpy [J/mol] j Index designating the injection point [-] k 0 Frequency factor [(m 3 /mol) n-1 /s] k Rate constant [(m 3 /mol) n-1 /s] L Channel length/Distance between two injections [m] n Reaction order [-] N Total amount of injection points [-] q Groove wave factor [-] Q Volumetric flow rate [m 3 /s] r Reaction rate [mol/(m 3 ‧s)] t r Characteristic reaction time [s] T Temperature [K] T max Hot spot temperature after the injection [K] u Flow velocity [m/s] Ua Global volumetric heat transfer coefficient, [W/(m 3 K)] W Channel width [m] X Conversion [-] z Axial coordinate/Theoretical distance between two injections [m] Greek α Factor describing the ratio of herringbone height to void channel height [-] α Designates the α-ionone molecule β Designates the β-ionone molecule ∆ Symbol for difference ε Emissivity [W/kg] ν Kinematic viscosity [m 2 /s]
doi:10.1515/gps-2013-0060 fatcat:rwmcxqdywrg3lfaxopkbfqv37e