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Molybdenum carbide supported on activated carbon (β‐Mo2C/AC) has been tested as catalyst in the reductive catalytic fractionation (RCF) of lignocellulosic biomass both in batch and in Flow‐Through (FT) reaction systems. High phenolic monomer yields (34 wt.%) and selectivity to monomers with reduced side alkyl chains (up to 80 wt.%) could be achieved in batch in the presence of hydrogen. FT‐RCF were made with no hydrogen feed, thus via transfer hydrogenation from ethanol. Similar selectivity could be attained in FT‐RCF using high catalyst/biomass ratios (0.6) and high molybdenum loading (35 wt.%) in the catalyst, although selectivity decreased with lower catalyst/biomass ratios or molybdenum contents. Regardless of these parameters, high delignification of the lignocellulosic biomass and similar monomer yields were observed in the FT mode (13‐15 wt.%) while preserving the holocellulose fractions in the delignified pulp. FT‐RCF system outperforms the batch reaction mode in the absence of hydrogen, both in terms of activity and selectivity to reduced monomers that is attributed to the two‐step non‐equilibrium processes and the removal of diffusional limitations that occur in the FT mode. Even though some molybdenum leaching was detected, the catalytic performance could be maintained with negligible loss of activity or selectivity for 15 consecutive runs. [ABSTRACT FROM AUTHOR]

Two series of Ni and Co catalysts supported onto La-Al2O3 were prepared and the CO2 hydrogenation reactions investigated. The catalytic performance was evaluated in terms of the evolution with the reaction temperature of the CO2 conversion and product (CH4 and CO) yields, as well as specific activities (TOF) and apparent activation energies. CH4 was the favored product over both metals while the TOF for CH4 formation was about three times higher for Ni than Co at 240–265 °C. Metallic particle size effects were found, with the TOF for CH4 formation decreasing over both Ni and Co as the mean metallic size decreased. In contrast, the TOF for CO formation tended to increase at a decreasing particle size for the catalysts with the smallest Ni particle sizes. The apparent activation energies for Ni and Co were very similar and significantly decreased to values of 73–79 kJ/mol when the metallic dispersion increased. The catalysts were prepared using the all-in-one method, resulting in (poly)vinyl alcohol (PVA) being a key additive that allowed us to enhance the dispersion of Ni and Co to give very effective catalysts. This comparative study joins the few existing ones in the literature in which catalysts based on these metals operated under strictly the same reaction conditions. [ABSTRACT FROM AUTHOR]

Renewed interest in CO2 methanation is due to its role within the framework of the Power-to-Methane processes. While the use of nickel-based catalysts for CO2 methanation is well stablished, the support is being subjected to thorough research due to its complex effects. The objective of this work was the study of the influence of the support with a series of catalysts supported on alumina, ceria, ceria–zirconia, and titania. Catalysts' performance has been kinetically and spectroscopically evaluated over a wide range of temperatures (150–500 °C). The main results have shown remarkable differences among the catalysts as concerns Ni dispersion, metallic precursor reducibility, basic properties, and catalytic activity. Operando infrared spectroscopy measurements have evidenced the presence of almost the same type of adsorbed species during the course of the reaction, but with different relative intensities. The results indicate that using as support of Ni a reducible metal oxide that is capable of developing the basicity associated with medium-strength basic sites and a suitable balance between metallic sites and centers linked to the support leads to high CO2 methanation activity. In addition, the results obtained by operando FTIR spectroscopy suggest that CO2 methanation follows the formate pathway over the catalysts under consideration. [ABSTRACT FROM AUTHOR]

Fruit and vegetable wastes derived from the agri-food industry are generated in large amounts and they can cause great environmental contamination because they have a high moisture content and microbial load. However, both their structural parts (stems, leaves, peels, pulps, seeds, and roots) and the residues resulting after the extraction of their juices are rich in different valuable compounds such as antioxidants, oils, fiber, fatty acids, isoprenoids, lipids, proteins, saponins, and phytoestrogens. Such bioactive compounds can be used as pharmaceutical excipients, food additives, or included in pharmaceutical formulations or food matrices for obtaining nutraceutical products and functional foods, respectively. The aim of this review is to present the most promising alternatives for the valorization of selected fruit and vegetable wastes, currently underexploited, as well as the challenges that may arise when considering the valorization of these wastes in the form of value-added bioactive products. This is exemplified through the revision of the opportunities offered by artichoke, cardoon, asparagus, and pomegranate, which generate large amounts of waste during their processing. A final section is devoted to present the emerging technologies that are being developed for an efficient extraction of bioactive compounds from vegetable matrices. [ABSTRACT FROM AUTHOR]