Proposal, design, and cost analysis of a hydrogen production process from cellulose via supercritical water gasification.

Hydrogen production from biomass, a renewable resource, has been attracting attention in recent years. We conduct a detailed process design for cellulose-derived hydrogen production via glucose using supercritical water gasification technology. Gasification of biomass in supercritical water offers advantages over conventional biomass conversion methods, including high gasification efficiency, elevated hydrogen molar fractions, and the minimization of drying process for wet biomass. In the process design, a continuous tank reactor is employed because the reaction in the glucose production process involves solids, and using a tube-type reactor may clog the reactor with solids. In the glucose separation process, glucose and levulinic acid, which cannot be separated by boiling point difference, are separated by using an extraction column. In the hydrogen separation process, the hydrogen purity, which could not be sufficiently increased with a single pressure swing adsorption (PSA) process, is increased to the target value by employing two sets of PSA columns. The overall utility cost is significantly reduced by $0.020/mol-H2 through heat integration. Our economic evaluation for this process results in a deficit of $0.015/mol-H2, as a price to be paid by the human for renewable hydrogen production from biomass at the present stage. By simply adopting the reported experimental condition, our process contains a large amount of water and sulfuric acid, which requires an enormous cost for the neutralizer, drying utility, and extractant. To improve the economic performance of the process, it is necessary to consider the reaction of cellulose solution at a higher concentration to reduce the burden of glucose separation. In addition, the effective use of the wasted hydrogen with a purity of about 95 vol% from the second PSA column may also improve the process economics. Whilst, the required energy cost for hydrogen production for our process is calculated to be significantly lower than those for other various representative hydrogen production methods: 0.37 (0.44) times less than that of steam reforming of methane with (without) CO2 capture, 0.15 times less than that of the water electrolysis by the electric power system, and 0.073 times less than that of electrolysis of water by wind power. This result implies the practical potential of our cellulose-based green hydrogen production scheme.

5-Hydroxymethylfurfural Synthesis from Monosaccharides by a Biphasic Reaction-Extraction System Using a Microreactor and Extractor.

5-Hydroxymethylfurfural (HMF) was synthesized from monosaccharides by a biphasic reaction system using a microreactor. The biphasic reaction system realized an immediate extraction and stabilization of product HMF, which further degrades under the reaction conditions. Segmented flow was utilized for an efficient reaction-extraction tool. The effect of extraction ability was evaluated based on the extraction phase/reaction phase partition coefficient of HMF. A Lewis acid catalyst was introduced to overcome the obstacle of the reaction, which was clarified as the isomerization of glucose to fructose, and improved the HMF yield to 85 mol % under the condition of T = 180 °C and τ = 47 min. The recovery of the product HMF was also examined using a constructed microextraction system, and HMF was selectively recovered from the extraction phase.

Contactless mass transfer for intra-droplet extraction.

This study demonstrates the possibility of "contactless" mass transfer between two aqueous slugs (droplets) separated by an oil slug in Taylor flow inside milli-channels. Separation of the alternating aqueous slugs at the outlet was performed by switching a couple of solenoid valves at branched outlets according to signals obtained by an optical sensor at the branch. Transfer of bromothymol blue (BTB) from acidic to basic aqueous slugs was performed for demonstration. In some cases, aqueous slugs separated by oil, merged catching on each other due to the velocity difference. Interfacial tension which was affected by the solute concentration was responsible for the velocity difference. Position-specific mass transfer activity at the rear end of the aqueous slugs was found on the course of the experiment. A meandering channel decreased the velocity difference and enhanced mass transfer. Almost complete (93%) transfer of BTB was achieved within a short residence time of several minutes under optimized conditions. The presented system opens a way for advanced separation using minimum amounts of the oil phase and allows concentrating the solute by altering relative lengths of the sender and receiver slugs.