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Plasma-assisted dry reforming of methane (DRM) is considered as a potential way to convert natural gas into fuels and chemicals under near ambient temperature and pressure; particularly for distributed processes based on renewable energy. Both catalytic and photocatalytic technologies have been applied for DRM to investigate the CH4 conversion and the energy efficiency of the process. For conventional catalysis; metaldoped Ni-based catalysts are proposed as a leading vector for further development. However; coke deposition leads to fast deactivation of catalysts which limits the catalyst lifetime. Photocatalysis in combination with non-thermal plasma (NTP), on the other hand; is an enabling technology to convert CH4 to more reactive intermediates. Placing the catalyst directly in the plasma zone or using post-plasma photocatalysis could generate a synergistic effect to increase the formation of the desired products. In this review; the recent progress in the area of NTP-(photo)catalysis applications for DRM has been described; with an in-depth discussion of novel plasma reactor types and operational conditions including employment of ferroelectric materials and nanosecond-pulse discharges. Finally, recent developments in the area of optical diagnostic tools for NTP, such as optical emission spectroscopy (OES), in-situ FTIR, and tunable diode laser absorption spectroscopy (TDLAS), are reviewed.

Dedicated to Professor Rüdiger Lange on the occasion of his 65th birthday Hydrodynamics and mass transfer of both gas-liquid and liquid-liquid Taylor flow simulation in microchannels are reviewed. Theoretical approaches for description of hydrodynamic parameters and mass transfer characteristics are corroborated by comparison with available experimental results. Similarities and peculiarities of liquid-liquid flows versus gas-liquid Taylor flows in capillaries are discussed. Tools of mass transfer intensification of gas-liquid and liquid-liquid Taylor flow in microchannels are analyzed and optimal process conditions for gas-liquid Taylor flows are evaluated.

The results of the recent experimental work performed by Butler et al. (2016, 2018) are analysed based on the dominant phenomena: (i) small scale convection by means of Taylor vortices in the liquid slugs and (ii) diffusion in lubrication film. A main result shown here is that the Taylor circulation frequency is able to reflect the global mass transfer rate in gas-liquid Taylor flow through an almost linear relationship, which emphasizes the interest of the circulating motion in the slug, and gives a very simple correlation to predict the k L a value (at large Schmidt number). A mechanism of flow behavior during the bubble formation at the T-mixer is proposed as a possible explanation of unexpected concentration areas (called ''islands"). However, despite of these unusual concentration field structures in these cases, the mass transfer rate coefficient k L a is still accurately predicted by the Taylor circulation frequency in the slug.