Microreactor catalyst-trap

Another solution was proposed by McGovern et al. [128]. Their microreactor is designed such that solid catalyst is suspended in the reaction channel by an arrangement of catalyst traps. The construction allows the use of commercial catalyst, and the pressure drop across the bed can be controlled by engineering the packing density. The reactor behavior was characterized by using the hydrogenation of liquid o-nitroanisole to o-anisidine as a model reaction. 

S. McGovern, G. Harish, C. S. Pai, W. Mansfield, J. A. Taylor, S. Pau, R. S. Bessei Multiphase flow regimes for hydrogenation in a catalyst-trap microreactor, Chem. Eng. J. 2008, 135, S229-S236. 

Fig. 9. Pulse microreactor system for use with 13C-labeled hydrocarbons. D, E, and J are microreactors J contains the catalyst to be used for hydrocarbon skeletal reaction D and E are used, when necessary, to generate the required reactant hydrocarbon from a non-hydrocarbon precursor (e.g., alcohol dehydration in D and olefin hydrogenation in E) reactant injected at C. F is a trap which allows the accumulation of products from several reaction pulses before analysis G is a G.P.C. column, K a katharometer. Traps H collect fractions separated on G for subsequent mass spectrometric study. When generating reactant hydrocarbon in D and E, a two-step process is preferable in which, with J below reaction temperature, the purified reactant hydrocarbon is collected in H, and this is recycled as reactant with D and E below reaction temperature but with J at reaction temperature. After C. Corolleur, S. Corolleur, and F. G. Gault, J. Catal. 24, 385 (1972).

The N-alkylation of 2-methyl-6-ethylaniline (MEA) with methoxy-2-propanol (MOIP) was investigated in the same flow microreactor under atmospheric pressure. Feed MEA MOIP = 0.5 (3 ml/h) and hydrogen (4,7 ml/min). The reaction product was condensed in a cooling trap. Each catalyst was tested for 24 h and 7 samples were collected and analyzed separately by GLC on a fused silica capillary column with methylsilicon fluid (Hewlett Packard) as stationary phase. 

The catalytic properties of the synthesised solids were determined during the partial oxidation of toluene (TO) to benzaldehyde (BA), p-methoxytoluene (MTO) to p-methoxybenzaldehyde (MBA, anisaldehyde) and p-chlorotoluene (CTO) to p-chlorobenzaldehyde (CBA). A microreactor set-up that contains a metering system for liquids and gases and a fixed bed quartz-glass reactor was used. The catalysts were introduced into the reactor as sieve fractions (1-1.25 mm) and mixed prior to oxidation runs with the equal portion of quartz glass (1 mm) to avoid local overheating. The product stream was analysed by on line-GC or it was trapped in aqueous ethanol and determined by off line-capillary GC. The formation of carbon oxides was continuously followed by non-dispersive IR photometry. 

Temperature-programmed reduction (TPR) experiments were carried out in a quartz-made microreactor connected to a thermal conductivity detector (TCD) equipped with active charcoal column, using 0.2 g calcined catalysts from 373 K to 1073 K. The gas stream, 5 % H2 diluted by nitrogen as reducing gas, was fed via a mass flow controller. After the reactor, the effluent gas was led via a 3 A molecular sieve trap to remove the produced water. 

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