Dry re-forming of methane with CO2 was investigated over bimetallic W and Ni incorporated mesoporous alumina catalysts prepared by the one-pot sol–gel route. Powdered materials were thoroughly ...characterized (N2 physisorption, XRD, XPS, SEM-EDX, TGA-DTA, TPH) prior to and after catalytic runs performed at 600 and 750 °C. High surface area W–Ni incorporated mesoporous alumina catalysts (S BET = 178–192 m2/g) synthesized in this work showed excellent performance for the conversion of model biogas to synthesis gas. The Ni–W containing materials exhibited high catalytic activity, which was maintained throughout 150 h of time-on-stream (TOS) long-term operation at 750 °C. Increase of the W loading (0–10–15 wt %) at fixed nickel amount (5 wt %) resulted in prevented deactivation of the catalyst, most prominent at 600 °C, and minimization of coke formation on the surface of the catalyst. Tungsten incorporation was thus proven to significantly enhance and stabilize the overall catalyst performance.
To attain sustained activity and stability in CH4–CO2 dry reforming (CCDR), two nanocomposite materials comprising silicon carbide or alumina and ceria–zirconia were introduced to support ...cobalt–nickel (CoNi) catalysts. Following the sequential impregnation-ultrasonication–deposition precipitation procedure, catalysts were systematically characterized and their performances were tested at 1.2 bar and 750 °C, where undiluted CH4–CO2 (ratio = 1:1) streams simulating biogas and the real industrial conditions were fed into a continuous flow reactor. For CCDR reactions conducted at a weight hourly space velocity (WHSV) of 12 L/(gcat h), good activity and stability were shown for both catalysts. Carbon content as low as 0.3 wt % and high conversions (70%–78% and 78%–88% for CH4 and CO2, respectively) were recorded over 23 h and 550 h tests. Interestingly, by increasing the WHSV value to an order of magnitude higher, i.e., at 120 L/(gcat h) with all other conditions held constant, a 6 h short-term test showed remarkably high conversions near equilibrium values, implying that the reactions still occurred within the thermodynamic regime, despite a reduced 10-fold mass of catalyst bed. This infers that not all active sites available on the catalyst surface were fully exploited. Compared to previous catalyst performances, the progress made in this work is ascribed to the synergistic effects from selected support materials that contributed remarkable redox properties, high surface area, mechanical and thermal stability to the catalysts.
•High OSC of CeZrO2 solid solution provides the functionality to oxidize formed coke.•Marginal improvement in catalytic activity is obtained with excessive NiCo loading.•No coke had accumulated after ...400h TOS at 1023K and equimolar CH4/CO2 feed.•CH4/CO2 feed ratio higher that 1 drastically accelerates coke accumulation.
This study investigates how morphology, active metal content and oxygen storage capacity of various bimetallic NiCo/CeZrO2 materials influence their catalytic activity and stability in the methane dry reforming reaction. Catalyst preparation procedure and chemical composition were steered to finally obtain materials, which do not accumulate carbon during the CH4/CO2 reforming reaction. Oxygen storage capacity of the CeZrO2 catalyst support was identified to play a vital role in retarding carbon accumulation over the tested NiCo/CeZrO2 materials. This property can be fully developed when a nanocrystalline solid solution of CeO2 and ZrO2 is formed. Secondly, a high dispersion of nickel and cobalt is crucial for two reasons: (i) catalysts which contain larger NiCo bimetallic particles (for example with 12–18wt.% active metal loading) exhibit a low metal-support interphase that results in enhanced coke formation rates; (ii) additionally, only a marginal gain in methane reforming rates are achieved at higher loadings, compared to catalysts with a 3–6wt.% active metal content. We demonstrated that a NiCo/CeZrO2 catalyst under relevant operating conditions after 400h TOS maintains 79 and 84% conversion of CH4 and CO2, with negligible coke accumulation.
Propolis is a resinous compound made by bees with well-known biological activity. However, comparisons between encapsulated and non-encapsulated propolis are lacking. Therefore, the antibacterial ...activity, effect on the phase transition of lipids, and inhibition of UV-induced lipid oxidation of the two forms of propolis were compared. The results showed that non-encapsulated propolis produces quicker effects, thus being better suited when more immediate effects are required (e.g., antibacterial activity). In order to gain an in-depth introspective on these effects, we further studied the synergistic effect of propolis compounds on the integrity of lipid membranes. The knowledge of component synergism is important for the understanding of effective propolis pathways and for the perspective of modes of action of synergism between different polyphenols in various extracts. Thus, five representative molecules, all previously isolated from propolis (chrysin, quercetin,
-ferulic acid, caffeic acid, (-)-epigallocatechin-3-gallate) were mixed, and their synergistic effects on lipid bilayers were investigated, mainly using DSC. The results showed that some compounds (quercetin, chrysin) exhibit synergism, whereas others (caffeic acid,
-ferulic acid) do not show any such effects. The results also showed that the synergistic effects of mixtures composed from several different compounds are extremely complex to study, and that their prediction requires further modeling approaches.
To improve the activity of nickel–cobalt (NiCo) catalyst supported on ceria-zirconia (CeZr) in the dry reforming of methane (DRM) with carbon dioxide, and to lower the coking rate in this process, ...1.5 wt.% and 2.5 wt.% NiCo catalysts were prepared using two approaches, i.e. freeze-drying (FD) and NO calcination for comparison against oven-drying (OD) and air calcination (air), respectively. Their impact was studied for 20 h of DRM at 750 °C and 1.2 bar, with undiluted CH4–CO2 feed simulating the real conditions. NO-calcined samples show, on average, more pronounced improvement through increased conversion of CH4 (90%), followed by FD samples (85%) from the air and OD-prepared samples (both 82%). Coking content varied between 0.67 and 0.82 wt.%. The observed slow catalyst deactivation might be caused by sintering of the catalysts. Higher quantity of CO than H2 for syngas production was obtained, owing to concurrent reverse water-gas shift side reaction, and high redox properties of the defective CeZr lattice that enabled surface carbon gasification by continuous replenishment of oxygen from the support to produce CO, of which the latter phenomenon also explains the low carbon deposition. H2/CO ratio between 0.42 and 0.85 was achieved, with FD and NO samples fared better (0.83–0.85) over the ones prepared by conventional methods (0.73–0.82) for 2.5%NiCo loaded catalysts.
Display omitted
•CH4–CO2 conversion for NO and FD catalyst is higher than air and OD-prepared ones.•Selectivity of syngas is high (averaging at 75–85%) for the former catalysts.•Higher metal loading (2.5 > 1.5 wt.% NiCo) can better depress RWGS side reaction.•Low coking content (0.67–0.82 wt.%) were obtained for 20 h of dry reforming tests.
The encapsulation of proteins into core-shell structures is a widely utilised strategy for controlling protein stability, delivery and release. Despite the recognised utility of these ...microstructures, however, core-shell fabrication routes are often too costly or poorly scalable to allow for industrial translation. Furthermore, many scalable routes rely upon emulsion-techniques implicating denaturing or environmentally harmful organic solvents. Herein, we investigate core-shell protein encapsulation through single-feed, aqueous spray drying: a cheap, industrially ubiquitous particle-formation technology in the absence of organic solvents. We show that an excipient's preference for the surface of the spray dried particle is well-predicted by its hydrodynamic diameter (Dh) under relevant feed buffer conditions (pH and ionic strength) and that the predictive power of Dh is improved when measured at the spray dryer outlet temperature compared to room temperature (R2 = 0.64 vs. 0.59). Lastly, we leverage these findings to propose an adaptable design framework for fabricating core-shell protein encapsulates by single-feed aqueous spray drying.
Archaeosomes are vesicles made from archaeal lipids. They are characterized by remarkable thermostability, resistance to enzymatic degradation, long-term stability, and immunomodulatory properties. ...In this review the current status of physicochemical properties of archaeal lipids and their stability in biological systems is presented, focusing on total polar lipids from Aeropyrum pernix K1. The isolated total polar lipids from Aeropyrum pernix K1 consist exclusively of glycerol ether lipids with isoprenoid groups attached to glycerol via ether linkages. More specifically, the two major polar lipids extracted from the membranes are C25,25-achaetidyl(glucosyl)inositol and C25,25-achaetidylinositol. An overview of the results of the effects of temperature and pH on the stability, structural organization, fluidity, and permeability of archaeosomes composed of pure C25,25 was examined by a combination of techniques, including fluorescence emission spectroscopy, electron paramagnetic resonance, differential scanning calorimetry, and confocal microscopy. We also compared the physicochemical properties of pure vesicles composed of either archaeal lipids or conventional lipids (e.g., 1,2-dipalmitoyl-sn-glycero-3-phosphocholine) with mixed vesicles composed of both lipid types. Archaeal lipids are discussed in terms of their potential use as a targeted drug delivery system based on the results of in vivo and cytotoxicity studies.
Encapsulation provides efficient approaches to increase stability and delivery of poorly soluble bioactive components, predominantly for fortification of beverages and similar liquid-based foods. In ...this study, folic acid was encapsulated within conventional and emulsion-templated alginate-pectin hydrogels, proliposomes, and a combination thereof. The stability of these systems was examined under various environmental conditions (pH 1.2-9.0, 25-85 °C, dark/light). The techniques demonstrated efficient and relatively straightforward production of well-defined microparticles and nanoparticles (350 nm to 250 μm). Dispersed folic acid provided a delivery system with unique pH-responsive features, which offered prolonged stability during food storage, and indicated increased release at the site of absorption upon ingestion. This formulation had no limitation due to particle size, while at the same time it allowed high encapsulation efficiencies (80%-100%), as compared to the low encapsulation efficiency achieved by solubilisation (6%). At the low pH that is expected in the stomach, leaching of the dispersed folic acid was prevented, while at the pH that is expected in the intestine, there was complete release via solubilisation and carrier swelling. Overall, the optimum for food processing and storage was pH 3.0, where ≥70% of 50% to 200% of the recommended daily allowance of folic acid remained in the alginate-pectin beads after 6 months at room temperature in the dark. The thermal properties were enhanced by emulsion-templated alginate-pectin beads and proliposomes. In this way, 30% to 75% retention of folic acid was achieved at temperatures ≤90 °C, where the proliposomes reinforced within a polysaccharide network achieved the highest level of protection.
•Onion waste represents a quarter of the harvested onion dry mass.•Up to 400 mg quercetin kg−1 dry produce can be retrieved from these waste.•Yellow onion peel powder has good stability even under ...adverse storage conditions.•Tablets and ethanol extracts of waste onion peel provide functional food additives.
Onion production generates abundant waste with high contents of bioactive compounds. These might have several beneficial functional properties for fortification of foods. To understand the variety and potential for further use, we examined various parts of the plants (edible/inedible waste/outer skin of onion), as well as extraction in water/ethanol and by shaking/sonication. Quercetin content and antioxidant capacity were initially determined for extracts of edible and waste parts of red, yellow and white onions, and red shallots. Ethanol extracts of the waste fraction had the highest quercetin content and antioxidant capacity. Except white onion, which contained no quercetin, the dried waste ethanol extracts contained up to 15 mg quercetin g−1 and had an antioxidant capacity of nearly 40 mg Trolox equivalents g−1. Furthermore, the dried skin ethanol extract of yellow onion, which is commercially the most available fraction, contained 8 mg quercetin g−1, with antioxidant capacity of 25 mg Trolox equivalents g−1 and high antimicrobial activity. Dried yellow onion skin showed good stability for the quercetin content under various storage conditions (4, 25, 37, 40 °C; dark/light; dry/moist air/in water). Bacteria, bacterial spores, yeast and mould counts remained unchanged for dried onion skin over 5 days under storage conditions that can promote food spoilage, indicating exceptional microbial stability. Finally, two different applications are demonstrated for dried yellow onion skin: tablets for home use (tablets as more convenient form of storage and for simple dosing in cooking), and a stabilisation additive (prolonged shelf-life of olive oil). Both represent efficient and straightforward approaches through waste prevention and food fortification.
Lutein is a challenging compound to incorporate into food, as it is poorly soluble and unstable in aqueous solutions. In this study, the aim was to prepare stable encapsulates of lutein and lutein ...esters using feasible and straightforward techniques. Fine suspensions based on polyoxyethylene sorbitan monooleate and medium-chain triglyceride oil micelle-like units with 3.45% lutein esters or 1.9% lutein equivalents provided high encapsulation efficiencies of 79% and 83%, respectively. Lutein encapsulated in fine suspensions showed superior stability, as 86% was retained within the formulation over 250 days at 25 °C in the dark. Under the same storage conditions, only 38% of lutein remained in corresponding formulations. Higher encapsulation efficiencies were achieved with lecithin emulsions, at up to 99.3% for formulations with lutein, and up to 91.4% with lutein esters. In lecithin emulsions that were stored for 250 days, 17% and 80% of lutein and lutein esters, respectively, were retained within the formulations.
PDF