Max Hefti

Magnetothermally responsive C/Co@PNIPAM-nanoparticles enable preparation of self-separating phase-switching palladium catalysts

We synthesized highly ferromagnetic, thermoresponsive nanomagnets with a graphene coated cobalt metal core to which amphiphilic N-isopropylacrylamide polymer branches were covalently attached. This novel hybrid material could be further end-group modified with a Pd–phosphine complex to catalyze Suzuki–Miyaura cross-coupling reactions. The heterogenized metal-complex could act as a ‘self-separating’ catalyst. Thermally triggered switching of poly-NIPAM coated C/Co-nanoparticles in typical biphasic water/toluene reaction systems allowed controlled shift from the organic to water phase and back. This enabled catalysis in the organic layer (reaction temperature) and return into the aqueous layer once the reaction mixture was cooled (ambient temperature; magnetic removal and reuse of the catalyst). Thus, the product phase was isolated via simple extraction/decantation. Moreover, the supported catalyst was recycled from the aqueous phase by taking advantage of the magnetic cores and reused over ten times.

On the potential of phase-change adsorbents for CO2 capture by temperature swing adsorption

We investigate the potential of a class of recently discovered metal-organic-framework materials for their use in temperature swing adsorption (TSA) processes for CO2 capture; the particularity of the considered materials is their reversible and temperature dependent step-shaped CO2 adsorption isotherm. Specifically, we present a comprehensive modeling study, where the performance of five different materials with step-shaped isotherms [McDonald et al., Nature, 2015, 519, 303] in a four step TSA cycle is assessed. The specific energy requirement of the TSA process operated with these materials is lower than for a commercial 13X zeolite, and a smaller temperature swing is required to reach similar levels of CO2 purity and recovery. The effect of a step in the adsorption isotherm is illustrated and discussed, and design criteria that lead to an optimal and robust operation of the considered TSA cycle are identified. The presented criteria could guide material scientists in designing novel materials whose step position is tailored to specific CO2 separation tasks.

Modeling water vapor adsorption/desorption cycles

This modeling work deals with the adsorption of water vapor on different porous materials where it undergoes capillary condensation and its adsorption/desorption isotherms exhibit hysteresis. The focus is on the description of the so called scanning curves, i.e. the adsorption/desorption isotherms observed when such an adsorbent is repeatedly loaded and unloaded in a range of conditions where hysteresis is observed, and on the simulation of fixed bed adsorption/desorption cycles. We use an approach originally developed by Štěpánek et al. (Chem Eng Sci 55(2):431–440, 2000), and expand it so as to include more general isotherms (not only the Dubinin–Radushkevich and Dubinin–Astakhov model, but also the Guggenheim–Anderson–de Boer model and the Do and Do model) and to allow for less than infinitely fast heat transfer, so as to consider non-isothermal situations. From a modeling point of view the results are satisfactory and highlight the need for better experimental data on water vapor adsorption, which need to be measured in enhanced experimental set-ups, capable to tightly control the relative humidity of the gas phase.

Perfusion settings and additives in liver normothermic machine perfusion with red blood cells as oxygen carrier. A systematic review of human and porcine perfusion protocols

Liver machine perfusion (MP) at normothermic temperature (NMP) is a promising way to preserve and evaluate extended criteria donor livers. Currently, no consensus exists in methodology and perfusion protocols. Here, the authors performed a systematic literature search to identify human and porcine studies reporting on liver NMP with red blood cells. A qualitative synthesis was performed concerning technical aspects of MP, fluid composition, gas supply, and liver positioning. Thirty‐seven publications including 11 human and 26 porcine studies were considered for qualitative synthesis. Control mode, pressure, flow, perfusate additives, and targeted blood gas parameters varied across human as well as porcine studies. For future analyses, it is advisable to report flow adjusted to liver weight and exact pressure parameters including mean, systolic, and diastolic pressure. Parenteral nutrition and insulin addition was common. Parenteral nutrition included amino acids and/or glucose without lipids. Taurocholic acid derivatives were used as bile flow promoters. However, short‐term human NMP without taurocholic acid derivatives seems to be possible. This finding is relevant due to the lack of clinical grade bile salts. Near physiological oxygen tension in the perfusate is doable by adjusting gas flows, while blood gas parameters regulation needs more detailed description.

Reply to “Ex situ normothermic machine perfusion of donor livers using a haemoglobin-based oxygen carrier: a viable alternative to red blood cells”

We highly appreciate the interest expressed in the letter by de Vries et all concerning our recent systematic review (1, 2), and congratulate for the successful transplantation using HBOC during normothermic perfusion. We agree, that ex situ normothermic and also subnormothermic liver perfusion using HBOC is per se an interesting option to spare red blood cells as oxygen carrier. This article is protected by copyright. All rights reserved.