Mass transfer characterisation of a microstructured falling film at pilot scale Jean-Noël Tourvieille, Frédéric Bornette, Régis Philippe, Quillaja Vandenberghe, Claude de Bellefon ⇑ Université de Lyon, CNRS, CPE Lyon, Laboratoire de Génie des Procédés Catalytiques, UMR 5285, BP 82077, 43 boulevards du 11, Novembre 1918, 69616 Villeurbanne, France highlights " Gas–liquid–solid mass transfer coefficients up to 9 s 1 are measured in a Micro-Falling Film Reactor. " The liquid film thickness is investigated by fluorescence confocal microscopy. " Full developed liquid film profiles are available. " A correlation is proposed to predict the average film thickness and mass transfer. article info Article history: Available online 28 July 2012 Keywords: Falling film Micro-structured reactor Film thickness Confocal microscopy Mass transfer abstract This work presents a first approach in the study of gas–liquid–solid mass transfer in a microstructured falling film at pilot scale based on experimental results of film morphology. The liquid film thickness is first investigated by fluorescence confocal microscopy by varying the physical properties of solvents such as viscosity and surface tension. A correlation is proposed that reveals a low effect of the capillary number Ca. Results are coupled with experimental gas–liquid–solid mass transfer determination using the catalytic hydrogenation of a-methylstyrene over 5% Pd/Al 2 O 3 . The overall gas–liquid–solid mass transfer coefficient K ov appears to be severely impacted by the liquid film thickness with values in the range from 0.7 to 4.3 s 1 at high and low flow rates respectively. Mass transfer coefficients determined from the film model are in good agreement with measured values when considering an average film thickness taking into account the microchannel profile. Ó 2012 Published by Elsevier B.V. 1. Introduction The interest of microstructured reactors for process intensifica- tion has been demonstrated through several applications [1,2] over many years. They are generally characterised by high surface to volume ratios leading to enhanced mass and heat transfer perfor- mances compared with traditional reactor technologies. One of these reactors is the well-known micro-structured fall- ing film (FFMR-standard) produced by IMM (Fig. 1a) and described elsewhere [3,4]. In this continuous reactor, a liquid is falling down a vertical grooved plate. The combination of capillary forces and small dimensions stabilizes the gas–liquid interface and thin liquid films bellow 100 lm can be obtained. Two operating regimes can be achieved. A gas can circulate over the liquid phase in counter or co-current flow and both flows are controlled separately. Gas– liquid–solid reactions are also considered by coating a channel with a catalyst [5]. Combined with a heat exchanger on the back of the plate, this provides a really interesting tool for very demanding reactions. A wide range of applications have been studied in FFMR such as fluorination [3], hydrogenation [6], separation of binary system [7] or CO 2 absorption. For this latter, numerical models have been proposed [8,9]. Despite interest sparked off by this improved contactor, only lab scale throughputs (in most cases about 1 ml min 1 ) are achieved. For industrial purposes, investigation of scale up is needed. From this perspective IMM has developed a tenfold scale up falling film micro-reactor (FFMR-L) presented in (Fig. 1a and b). Coating the micro-channels with a catalytic phase can also be of great interest for pharmaceutical applications. Assessment, control, and prediction of mass transfer perfor- mances are a fundamental step for successful industrial implemen- tation. Considering falling film technology, the key parameters for mass transfer control are the liquid film thickness and hydrody- namics of the liquid phase. Some works have been devoted to this latter point. The use of smart interfaces such as herringbones structures has shown that an interesting improvement can be obtained in mixing quality leading to better conversion for G/L systems [12–14]. At the scale of micro-structures, viscous and capillary forces are predominant with a Ca number below 10 3 . Understanding the 1385-8947/$ - see front matter Ó 2012 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.cej.2012.07.095 ⇑ Corresponding author. Tel.: +33 472 43 1754. E-mail address: claude.debellefon@lgpc.cpe.fr (C.de Bellefon). Chemical Engineering Journal 227 (2013) 182–190 Contents lists available at SciVerse ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej