Heterogeneous catalytic processes channel reactors

Mkrostructured reactors (MSR) for heterogeneous catalytic processes mostly consist of a large number of parallel flow channels. At least one dimension of these channels is smaller than 1 mm, but rarely <100 pm. This leads to an increased heat transfer in the direction of the smallest dimension. The volumetric heat transfer performance in microstructured devices is several magnitudes higher than in conventional reactors. Therefore, even highly exothermic or endothermic reactions can be operated under near isothermal conditions and thermal runaway can be avoided (see Chapter 5). In addition, mass transfer between the bulk phase... 

The influence of different process and geometrical parameters on conversion was estimated in case of an irreversible first-order catalytic reaction. The influence of temperature nonuniformity (when temperature varies between the channels) had the largest impact on conversion in a nonideal reactor as compared to non-uniform flow distribution and nonequal catalyst amount in the channels. Obtained correlations were used to estimate the influence of a variable channel diameter on the conversion in a microreactor for a heterogeneous first-order reaction. It was found that the conversion in 95% of the microchannels varied between 59 and 99% at = 0.1 and Damkohler number of 2. Figure 9.1a shows conversion as a function of Damkohler number for an ideal microreactor and a microreactor with variations in the channel diameter (aj = 0.1). It can be seen that although the conversion in individual channels can vary considerably, the effect of nonuniformity in channel diameter on the overall reactor conversion is smaller. The lower conversion in channels with a higher flow rate is partly compensated by a higher conversion in channels with a lower flow rate. Due to the nonlinear relation between the channel diameter and the flow rate, the effects do not cancel completely and a decrease in reactor conversion is observed. 

---