Biomass as a renewable and abundantly available carbon source is a promising alternative to fossil resources for the production of chemicals and fuels. The development of biobased chemistry, along with catalyst design, has received much research attention over recent years. However, dedicated reactor concepts for the conversion of biomass and its derivatives are a relatively new research field. Continuous flow microreactors are a promising tool for process intensification, especially for reactions in multiphase systems. In this work, the potential of microreactors for the catalytic conversion of biomass derivatives to value-added chemicals and fuels is critically reviewed. Emphases are laid on the biphasic synthesis of furans from sugars, oxidation and hydrogenation of biomass derivatives. Microreactor processing has been shown capable of improving the efficiency of many biobased reactions, due to the transport intensification and a fine control over the process. Microreactors are expected to contribute in accelerating the technological development of biomass conversion and have a promising potential for industrial application in this area.

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Homogeneous Co/Mn/Br catalyzed aerobic oxidation of benzyl alcohol in acetic acid to benzaldehyde was performed in polytetrafluoroethylene microreactors operated under slug flow at temperatures up to 150 C and pressures up to 5 bar. Depending on the bubble velocity and length, a wetted or dewetted slug flow was observed, characterized typically by a complete or partially wetting liquid film around the bubble body. The latter flow suffered from a limited interfacial area for mass transfer. Experiments at temperatures up to ca. 90 C were under kinetic control given no product yield difference under wetted and dewetted slug flows and were used to establish a simplified kinetic expression (first order in benzyl alcohol and zero order in oxygen). This allows to develop a mass transfer model combined with an instantaneous reaction regime that well described the experimental results at higher temperatures where mass transfer was limiting in the dewetted slug flow.

The quality of cocoa depends on both the origin of the cacao and the processing stages. The roasting process is critical because it develops the aroma and flavor, changing the beans' chemical composition significantly by chemical reactions induced by thermal energy. Aspects have been identified as the main differences between bulk cocoa and fine cocoa, the effect of time and temperature on the formation of the flavor and aroma, and the differences between conductive heating in an oven, convective with airflow, and steam flow. Thermal energy initially causes drying, then non-enzymatic browning chemical reactions (Maillard reaction, Strecker degradation, oxidation of lipids, and polyphenols), which produce volatile and non-volatile chemical compounds related to the flavor and aroma of cocoa roasted. This review identified that the effect of the heating rate on the physicochemical conversion of cocoa is still unknown, and the process has not been evaluated in inert atmospheres, which could drastically influence the avoidance of oxidation reactions. The effect of particle size on the performance of product quality is still unknown. A more in-depth explanation of energy, mass, and chemical kinetic transfer phenomena in roasting is needed to allow a deep understanding of the effect of process parameters. In order to achieve the above challenges, experimentation and modeling under kinetic control (small-scale) are proposed to allow the evaluation of the effects of the process parameters and the development of new roasting technologies in favor of product quality. Therefore, this work seeks to encourage scientists to work under a non-traditional scheme and generate new knowledge.