Low-Temperature Methane Activation Reaction Pathways over Mechanochemically-Generated Ce4+/Cu+ Interfacial Sites.

Methane is a valuable resource and its valorization is an important challenge in heterogeneous catalysis. Here it is shown that CeO2/CuO composite prepared by ball milling activates methane at a temperature as low as 250 °C. In contrast to conventionally prepared catalysts, the formation of partial oxidation products such as methanol and formaldehyde is also observed. Through an in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and operando Near Edge X-Ray Absorption Fine Structure Spectroscopy (NEXAFS) approach, it can be established that this unusual reactivity can be attributed to the presence of Ce4+/Cu+ interfaces generated through a redox exchange between Ce3+ and Cu2+ atoms facilitated by the mechanical energy supplied during milling. DFT modeling of the electronic properties confirms the existence of a charge transfer mechanism. These results demonstrate the effectiveness and distinctiveness of the mechanical approach in creating unique and resilient interfaces thereby enabling the optimization and refining of CeO2/CuO catalysts in methane activation reactions.

An exopolysaccharide from Leuconostoc mesenteroides showing interesting bioactivities versus foodborne microbial targets.

An exopolysaccharide (EPS_B3) produced by a Leuconostoc mesenteroides strain isolated from a semi-hard Italian cheese was chemically and biologically characterized. HPLC-SEC, NMR, FT-IR and monosaccharide composition experiments were performed. Antimicrobial, antibiofilm, bifidogenic, antioxidant, and DNA-protective activity of EPS_B3 were also studied. Results revealed that EPS_B3 was a mixture of two high-molecular-weight dextran with low branching degree. Moreover, EPS_B3 displayed significant antibacterial activity against eight foodborne pathogens and inhibited biofilm formation by Listeria monocytogenes. EPS_B3 also evidenced bifidogenic activity, stimulating the growth of three probiotic bifidobacteria, and improving the tolerance of Bifidobacterium animalis subsp. lactis to oxygen stress. It also protected plasmid DNA from hydrogen peroxide damage. Only limited antioxidant capacity was observed. In conclusion, data suggest that EPS_B3 might be exploited in the context of functional foods especially for its marked antimicrobial activity as well as for the ability to improve the viability of bifidobacteria in probiotic foods. However, further studies should be carried out to assess the ability of EPS_B3 to reach intact the target site (i.e., gastrointestinal tract) to consider the possibility of use it as a new functional ingredient in foods.

Ceria-Based Materials in Hydrogenation and Reforming Reactions for CO2 Valorization.

Reducing greenhouse emissions is of vital importance to tackle the climate changes and to decrease the carbon footprint of modern societies. Today there are several technologies that can be applied for this goal and especially there is a growing interest in all the processes dedicated to manage CO2 emissions. CO2 can be captured, stored or reused as carbon source to produce chemicals and fuels through catalytic technologies. This study reviews the use of ceria based catalysts in some important CO2 valorization processes such as the methanation reaction and methane dry-reforming. We analyzed the state of the art with the aim of highlighting the distinctive role of ceria in these reactions. The presence of cerium based oxides generally allows to obtain a strong metal-support interaction with beneficial effects on the dispersion of active metal phases, on the selectivity and durability of the catalysts. Moreover, it introduces different functionalities such as redox and acid-base centers offering versatility of approaches in designing and engineering more powerful formulations for the catalytic valorization of CO2 to fuels.