Abstract 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).
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.
The exact location of bubbles with respect to the catalytic layer impacts the microreactor performance. In this work, we propose to control bubble nucleation using micropits to maximize the microreactor efficiency.
To obtain insight into transport phenomena in gas/liquid/solid catalytic microsystems, a theoretical model was developed to study heat and mass transfer at the microscale in such multiphase systems. In particular, systems were investigated in which the gaseous products nucleate and grow as microbubbles on the catalytic surface, whereas the reactants are dissolved in a liquid phase. A microfluidic platform providing spatial control on the bubble nucleation was designed and fabricated and applied to experimentally study the influence of bubbles on transport phenomena. The observations were compared with our theoretical model.
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