Aqueous‐Phase Reforming in a Microreactor: The Role of Surface Bubbles

Abstract

In heterogeneous catalysis, the creation of gaseous products as bubbles in a liquid phase on the catalytic surface is associated with slip phenomena. In a microreactor, the slip length at the gas‐liquid interface is in the same order of magnitude as the reactor dimensions, which can affect fluid dynamics and transport phenomena. Here, the interplay of momentum, heat and mass transfer in a microreactor, when bubbles form on the catalytic surface, was investigated using two‐dimensional simulations. The effect of bubbles on the endothermic process of aqueous‐phase reforming of a glycerol solution was evaluated in terms of conversion and conversion and temperature in the reactor. Altogether, this study highlights the impact of bubbles, not only on the transport phenomena but also on the reactor performance.

Influence of the Catalyst Particle Size on the Aqueous Phase Reforming of n-Butanol Over Rh/ZrO2

“…Theoretical work of Datsevich (2003a;2003b;2004;2005, Oehmichen et al, 2010 has shown that formation of gas bubbles can influence transfer inside particles dramatically, whereas we have recently demonstrated in a microfluidic device, mimicking pores in a catalyst support, that both retardation as well as enhancement of transport on the pore is possible (Espinosa et al, 2018). Very recently, a simulation using APR of glycerol as model reaction showed the effect of bubbles on the kinetics and transport phenomena in a 2D system (Ripken et al, 2019). This clearly needs further research to decide if such effects experimentally contribute in practical 3D porous catalysts.…”

Towards controlled bubble nucleation in microreactors for enhanced mass transport

“…23 In previous work, we numerically investigated the influence of bubbles on the momentum, heat and mass transfer for APR of a 10 wt% glycerol aqueous solution, assuming a 2Dconfiguration for a microchannel reactor. 24 In that work, hemispherical or elliptical bubbles with contact angles of up to 90°against the catalytic surface were modeled, resulting in a significant coverage of the catalytic surface. This first study indicated that the conversion and the temperature profile in the microreactor are mainly determined by the fraction of the catalytic surface covered by bubbles, with no effect of the bubble protrusion angle.…”