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The continuous hydrogenation of a mixture of L-arabinose and D-galactose over a Ru/C catalyst was investigated in a miniaturized packed bed reactor. The reaction is one important step of the transformation process of the naturally occurring hemicellulose arabinogalactan (AG) into valuable sugar alcohols. Process intensification was accomplished by reducing the reactor dimensions to a few millimeters, thus leading to better mass and heat transfer performance. The effect of temperature, pressure and liquid flow rate on the yield as well as byproduct formation will be discussed. Based on a kinetic model derived from batch experiments, a model of the continuous reactor was developed and used for scale-up purposes.

Structured catalysts are a widely discussed approach for process intensification of chemical multiphase reactors. But equal to common catalyst structures, homogeneous educt distribution along the catalytic surface is mandatory for high reactor performance. Especially monolithic structures require a homogeneous initial fluid distribution. A novel distribution concept for gas-liquid flow through arbitrary channel matrices is presented. It is based on the injection principle where gas and liquid are inserted directly into the channels. A prototype for different cell densities was built and tested by various measurement techniques: gravimetry, X-ray tomography, and an optical fiber sensor. Additionally, the flow regime per channel was detected as equal to single-channel conditions.

Microbiological photosynthesis is a promising tool for producing hydrogen in an ecologically friendly and economically efficient way. Certain microorganisms (e.g. algae and bacteria) can produce hydrogen using hydrogenase and/or nitrogenase enzymes. However, their natural capacity to produce hydrogen is relatively low. Thus, there is a need to optimize their core photosynthetic processes as well as their cultivation, for more efficient hydrogen production. This review aims to provide a holistic overview of the recent technological and research developments relating to photobiological hydrogen production and downstream processing. First we cover photobiological hydrogen synthesis within cells and the enzymes that catalyze the hydrogen production. This is followed by strategies for enhancing bacterial hydrogen production by genetic engineering, technological development, and innovation in bioreactor design. The remaining sections focus on hydrogen as a product, that is, quantification via (in-process) gas analysis, recent developments in gas separation technology. Finally, a discussion of the sociological (market) barriers to future hydrogen usage is provided as well as an overview of methods for life cycle assessment that can be used to calculate the environmental consequences of hydrogen production.