Mixed Matrix Pt-Carbon Nanofiber Polyethersulfone Catalytic Membranes for Glucose Dehydrogenation.

The advancement of technologies for producing chemicals and materials from non-fossil resources is of critical importance. An illustrative example is the dehydrogenation of glucose, to yield gluconic acid, a specialty chemical. In this study, we propose an innovative production route for gluconic acid while generating H2 as a co-product. Our concept involves a dual-function membrane, serving both as a catalyst for glucose dehydrogenation into gluconic acid and as a means to efficiently remove the produced H2 from the reaction mixture. To achieve this two membranes were developed, one catalytically active and one dense aimed at H2 removal. The catalytic membrane showed significant activity, yielding 16 % gluconic acid (t=120 min) with a catalyst selectivity of 93 % and stable performance over five consecutive cycles. Incorporating the H2 separating membrane showed the significance of H2 removal in driving the reaction forward. Its inclusion led to a twofold increase in gluconic acid yield, aligning with Le Chatelier's principles. As a future prospect the two layers can be combined into a dual-layer membrane which opens the way for a new production route to simultaneously produce gluconic acid and H2, using high-throughput reactors such as hollow-fiber systems.

Toward the Rational Design of More Efficient Mo2C Catalysts for Hydrodeoxygenation-Mechanism and Descriptor Identification.

Viable alternatives to scarce and expensive noble-metal-based catalysts are transition-metal carbides such as Mo and W carbides. It has been shown that these are active and selective catalysts in the hydrodeoxygenation of renewable lipid-based feedstocks. However, the reaction mechanism and the structure-activity relationship of these transition-metal carbides have not yet been fully clarified. In this work, the reaction mechanism of butyric acid hydrodeoxygenation (HDO) over molybdenum carbide (Mo2C) has been studied comprehensively by means of density functional theory coupled with microkinetic modeling. We identified the rate-determining step to be butanol dissociation: C4H9*OH + * → C4H9* + *OH. Then we further explored the possibility to facilitate this step upon heteroatom doping and found that Zr- and Nb-doped Mo2C are the most promising catalysts with enhanced HDO catalytic activity. Linear-scaling relationships were established between the electronic and geometrical descriptors of the dopants and the catalytic performance of various doped Mo2C catalysts. It was demonstrated that descriptors such as dopants' d-band filling and atomic radius play key roles in governing the catalytic activity. This fundamental understanding delivers practical strategies for the rational design of Mo2C-based transition-metal carbide catalysts with improved HDO performance.

Cinnamaldehyde hydrogenation over carbon supported molybdenum and tungsten carbide catalysts.

The potential of carbon supported Mo and W carbides to replace Pt is shown for the hydrogenation of cinnamaldehyde. Although the carbide catalysts are 4-6 times less active, both the carbides and Pt are selective towards CC hydrogenation. Unlike Pt, the carbides additionally form ß-methylstyrene.

Shedding Light on Solid Sorbents: Evaluation of Supported Potassium Carbonate Particle Size and Its Effect on CO2 Capture from Air.

Solid sorbents are essential for developing technologies that directly capture CO2 from air. In solid sorbents, metal oxides and/or alkali metal carbonates such as potassium carbonate (K2CO3) are promising active components owing to their high thermal stability, low cost, and ability to chemisorb the CO2 present at low concentrations in air. However, this chemisorption process is likely limited by internal diffusion of CO2 into the bulk of K2CO3. Therefore, the size of the K2CO3 particles is expected to be an important factor in determining the kinetics of the sorption process during CO2 capture. To date, the effects of particle size on supported K2CO3 sorbents are unknown mainly because particle sizes cannot be unambiguously determined. Here, we show that by using a series of techniques, the size of supported K2CO3 particles can be established. We prepared size-tuned carbon-supported K2CO3 particles by tuning the K2CO3 loading. We further used melting point depression of K2CO3 particles to collectively estimate the average K2CO3 particle sizes. Using these obtained average particle sizes, we show that the particle size critically affects the efficiency of the sorbent in CO2 capture from air and directly affects the kinetics of CO2 sorption as well as the energy input needed for the desorption step. By evaluating the mechanisms involved in the diffusion of CO2 and H2O into K2CO3 particles, we relate the microscopic characteristics of sorbents to their macroscopic performance, which is of interest for industrial-scale CO2 capture from air.

Carbohydrate structure-activity relations of Au-catalysed base-free oxidations: gold displaying a platinum lustre.

This paper describes the base-free gold-catalysed oxidation of four different carbohydrates in a packed bed plug flow reactor. The influence of the carbohydrate structure on the catalytic activity and selectivity was investigated by comparing two neutral sugars (glucose (Glc) and galactose (Gal), both with primary alcohols at C6), with their sugar-acid analogues (glucuronic acid (GlcA) and galacturonic acid (GalA), both with carboxylic acids at C6). The orientation of OH-groups at the C4-position (equatorial in Glc/GlcA and axial in Glc/GlcA), and the C6-functionality (primary alcohols in Gal/Glc and carboxylic acids in GalA/GlcA) has a profound influence on the catalytic activity. When the OH-groups are in an axial position their reactivity was higher compared to the OH-groups in the equatorial position for both the sugars and the sugar acids. In addition the reactivity of carbohydrates over Au-catalysts under base-free conditions is different compared to alkaline conditions, and is more in line with a Pt-catalysed dehydrogenation mechanism.