In this perspective, we argue that transition metal carbides such as molybdenum and tungsten hold great potential for the catalytic conversions of future feedstocks due to their ability to remain active in the presence of impurities in the feedstock.

The influence of the support‐oxygen groups and Pt particle size on the catalytic performance of Pt/AC for the aerobic oxidation of α‐D‐glucose to gluconic acid (glycolate) was studied. Surface‐oxygen groups were introduced by treating the activated carbon support with diluted HNO3 without significantly affecting the support porosity. The platinum particle size could be decreased on both the treated and untreated support by adding an additional calcination step to the synthesis. The presence of oxygen‐containing groups is shown to be highly beneficial (∼4 fold increase in the turnover frequency) only for the smallest Pt particle size (1.8–2.5 nm, determined by TEM). For the catalyst with the larger Pt size (3.4–3.6 nm), the presence of additional oxygen‐contacting groups does not significantly enhance the activity. Since the size of the smaller Pt particles is close to the product/substrate molecular diameter (glucose/gluconic acid, ∼0.9 nm) the observed effect can be attributed to the effective repulsion by the negatively charged oxygen groups in close proximity to the glycolate reaction product. The increase in activity originates from the resulting enhanced desorption of glycolate by alleviating the product inhibition presence due to the strong interaction of glycolate with Pt.

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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...

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.