The use of reactive gases for syntheses on small laboratory scale is often avoided due to safety concerns so that expensive alternatives are required. The recent development of gas-permeable membrane-based reactors offers new options for safe handling of these gases in a continuous-flow system. A prototype of a gas/ liquid system was built to introduce gas in the microreactor. An integrated gas flow controller and inline FTIR analysis were used to safely handle the gas. With the system, the carboxylation of a Grignard reagent with carbon dioxide was chosen as a nonhazardous model reaction to validate the prototype reactor.

Hydrogen is a promising renewable energy source that can be produced from biomass using aqueous‐phase reforming (APR). Here, using data obtained from AspenPlus and the literature, we evaluated the phase state, temperature‐dependent enthalpy, and Gibbs free energy for the APR of small biomass model substrates. Phase equilibrium studies reveal that, under typical APR reaction conditions, the reaction mixture is in the liquid phase. Therefore, we show for the first time that the water‐gas shift reaction (WGSR), which is the second main reaction of APR, must be modeled in the liquid phase, resulting in an endothermic instead of an exothermic enthalpy of reaction. A significant implication of this finding is that, although APR has been introduced as more energy saving than conventional reforming methods, the WGSR in APR has a comparable energy demand to the WGSR in steam reforming (SR).

Aqueous‐Phase Reforming (APR) is a promising hydrogen production method, where biomass is catalytically reformed under high pressure and high temperature reaction conditions. To eventually study APR, in this paper, we report a high‐pressure and high‐temperature microfluidic platform that can withstand temperatures up to 200°C and pressures up to 30 bar. As a first step, we studied the phase transition of four typical APR biomass model solutions, consisting of 10 wt% of ethylene glycol, glycerol, xylose or xylitol in MilliQ water. After calibration of the set‐up using pure MilliQ water, a small increase in boiling point was observed for the ethylene glycol, xylitol and xylose solutions compared to pure water. Phase transition occurred through either explosive or nucleate boiling mechanisms, which was monitored in real‐time in our microfluidic device. In case of nucleate boiling, the nucleation site could be controlled by exploiting the pressure drop along the microfluidic channel. Depending on the void fraction, various multiphase flow patterns were observed simultaneously. Altogether, this study will not only help to distinguish between bubbles resulting from a phase transition and/or APR product formation, but is also important from a heat and mass transport perspective.

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.

The interplay of heat and mass transfer in a gas/liquid/solid or heterogeneous catalytic microreactor, in which bubbles grow on a surface, is highly complex. Specifically, distortion of the fluid due...