title: Subtle Microwave-Induced Overheating Effects in an Industrial Demethylation Reaction and Their Direct Use in the Development of an Innovative Microwave Reactor.
abstract: A systematic study of the conventional and microwave (MW) kinetics of an industrially relevant demethylation reaction is presented. In using industrially relevant reaction conditions the dominant influence of the solvent on the MW energy dissipation is avoided. Below the boiling point, the effect of MWs on the activation energy Eaand k0is found nonexistent. Interestingly, under reflux conditions, the microwave-heated (MWH) reaction displays very pronounced zero-order kinetics, displaying a much higher reaction rate than observed for the conventionally thermal-heated (CTH) reaction. This is related to a different gas product (methyl bromide, MeBr) removal mechanism, changing from classic nucleation into gaseous bubbles to a facilitated removal through escaping gases/vapors. Additionally, the use of MWs compensates better for the strong heat losses in this reaction, associated with the boiling of HBr/water and the loss of MeBr, than under CTH. Through modeling, MWH was shown to occur inhomogeneously around gas/liquid interfaces, resulting in localized overheating in the very near vicinity of the bubbles, overall increasing the average heating rate in the bubble vicinity vis-à-vis the bulk of the liquid. Based on these observations and findings, a novel continuous reactor concept is proposed in which the escaping MeBr and the generated HBr/water vapors are the main driving forces for circulation. This reactor concept is generic in that it offers a viable and low cost option for the use of very strong acids and the managed removal/quenching of gaseous byproducts.
authors.affiliation: Green Chemistry Centre of Excellence, University of York , YO10 5DD, Heslington, York, United Kingdom.
authors.forename: Mario
authors.initials: M
authors.lastname: De Bruyn
authors.affiliation: Green Chemistry Centre of Excellence, University of York , YO10 5DD, Heslington, York, United Kingdom.
authors.forename: Vitaliy L
authors.initials: VL
authors.lastname: Budarin
authors.affiliation: Process & Energy Department, Delft University of Technology , Leeghwaterstraat 39, 2628CB Delft, The Netherlands.
authors.forename: Guido S J
authors.initials: GSJ
authors.lastname: Sturm
authors.affiliation: Process Engineering for Sustainable Systems (ProcESS), Department of Chemical Engineering, Catholic University of Leuven (KULeuven) , Celestijnenlaan 200F, 3001 Leuven, Belgium.
authors.forename: Georgios D
authors.initials: GD
authors.lastname: Stefanidis
authors.affiliation: SAIREM , 12 Porte du Grand Lyon, 01702 NEYRON Cedex, France.
authors.forename: Marilena
authors.initials: M
authors.lastname: Radoiu
authors.affiliation: Process & Energy Department, Delft University of Technology , Leeghwaterstraat 39, 2628CB Delft, The Netherlands.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Stankiewicz
authors.affiliation: Green Chemistry Centre of Excellence, University of York , YO10 5DD, Heslington, York, United Kingdom.
authors.forename: Duncan J
authors.identifier: 0000-0003-2017-7076
authors.initials: DJ
authors.lastname: Macquarrie