New Proton-Conducting Membranes Based on Phosphorylated Polybenzimidazole and Silica
We have synthesized hybrid membranes based on N-phosphorylated polybenzimidazole, containing different percentages of silica (2–20 wt %). The materials have been characterized by scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, IR spectroscopy, and impedance spectroscopy. The membranes have been shown to contain silica nanoparticles with a bimodal size distribution: 3–5 and 20–60 nm. The hybrid membranes have high proton conductivity (9.7 mS/cm at 130°C), which has a maximum when the dopant content is 2–10 wt %. The phosphonic groups grafted onto the polymer ensure additional hydration of the membranes at increased humidity. The addition of silica helps to reduce the gas permeability of the membranes by a factor of ~1.5
A new perfluorinated sulfocationic polymer and a membrane based thereon have been produced using the thermally initiated high-pressure polymerization. The proton conductivity of obtained material is higher than that of commercial Nafion membranes and reaches 57 mS cm–1 at 21 C and 114 mS cm–1 at 79 C.
We have performed a comparative analysis of the bio-oil produced by thermal liquefaction of microalgae in different solvents using high-resolution Orbitrap mass spectrometry and GC-MS approach. Water, methanol, ethanol, butanol, isopropanol, acetonitrile, toluene, and hexane were used as solvents in which the liquefaction was performed. It was observed that all resulting oils demonstrate a considerable degree of similarity. For all samples, compounds containing 1 and 2 nitrogen atoms dominated in the positive ESI spectra, while a relative contribution of other compounds was small. In negative ESI mode, compounds having 2 to 7 oxygens were observed. Statistical analysis revealed that products can be combined in two groups depending on the solvent used for the liquefaction. To the first group, we can attribute the products obtained by using protic (alcohols) and to the second by using aprotic (acetonitrile, toluene) solvents. Nevertheless, based on our results, we concluded that solvent possesses a minor impact on molecular composition of bio-oil. We suggested that the driving force of the liquefaction reaction is the thermal dehydration of the carbohydrate in algae, resulting in water formation, which could be the trigger of the producing of bio-oil. To prove this hypothesis, we performed the reaction with the dry algae in the absence of the solvent and observed the formation of bio-oil.
The New Russian Encyclopedia is a fundamental reference publication in 18 volumes that characterizes nature, population, economy, history, science, art, technology and other important aspects. Contains about 60,000 articles, about 30,000 biographies, about 15,000 color illustrations, maps, charts, diagrams, tables. Leaves since 2003.
This volume, being the 55th of this Series, contains a wealth of information on bioactive natural products. In Chapter 1, Watson and colleagues have discussed the synthesis of monoterpene indole alkaloids, an important class of structurally diverse natural products, with respect to conventional and biomimetic synthetic approaches.
Titanocene(III) has been widely used in the synthesis of complex organic molecules and natural products including polyketides, phenylpropanoids, antibiotics, and alkaloids. Oltra and coworkers have provided a review on the stereoselective synthesis of natural products facilitated by titanocene(III) in Chapter 2.
About 70 biologically active macrocyclic bisbibenzyls (MBBs) have been isolated and structurally elucidated during the last 30 years. Song and Zhao, in Chapter 3, have provided a review on the synthesis of MBBs with diverse pharmacological properties.
Diabetes mellitus is the most common endocrine/metabolic disorder that poses a global health concern. Reyes and colleagues have discussed the hypoglycemic activity of some terrestrial and marine bioactive compounds with potential for treating type 2 diabetes in Chapter 4. In Chapter 5, Pietruszka and coworkers have highlighted the importance of some marine oxylipins that exhibit different bioactive properties.
Depression has become a psychiatric disorder, which leads to various disabilities. Natural compounds like polyphenols and terpenoids have antioxidant and neuroprotective properties and can be used for the treatment of depression. In Chapter 6, Rodrigues et al. review the clinical studies and trials on polyphenols and terpenoids for the treatment of various psychiatric disorders. The lipid A phosphate and their phosphorylated analogues found in Gram-negative bacteria are of major importance because they provide the host with defense against infections from various microorganisms. Paradies and Zimmermann have discussed physical characteristics, isolation, and bioactivity of lipopolysaccharides (lipid A) for developing new vaccines and therapeutics in Chapter 7.
Hydroxycinnamic acids (HCAs) are a group of phytonutrients with numerous beneficial effects on human health that are largely derived from plants. HCAs play important roles like defense against UV rays or pathogenic attack during growth and development of plants. In Chapter 8, El-Seedi and colleagues present a review focusing on the therapeutic effects of HCAs for the treatment of cancer, diabetes, pulmonary, hepatic, neuro-, and cardiovascular diseases. In Chapter 9, Pomilio and Mercader have presented the study of natural anthocyanins and other related flavonoids for the readers, highlighting their possible and preferable uses as health-protecting food dyes over synthetic ones. They have also discussed the anthocyanins isolated from Ipomoea cairica along with their QSAR studies.
Cardiovascular diseases are considered to be a major threat to health. Polyphenols and carotenoids are structurally diverse groups of bioactive compounds isolated from fruits and vegetables, carrying protective effects against endothelial dysfunction. These therapeutic effects have been explored by Yamagata in Chapter 10.
The roots of licorice and ivy leaves have been used in folk medicine and drugs since long. The biological activity of these complexes has been discussed by Yakovishin and Grishkovets in Chapter 11. In Chapter 12, the chemical and biological characteristics of amicoumacins and xenocoumacins are reviewed by Korshun et al. with reference to the preparation of antibiotics.
I hope that this volume will be received with the same enthusiasm as the earlier volumes of this long-standing series the first volume of which was published under my Editorship in 1988. I would like to express my gratitude to Ms. Taqdees Malik and Mr. Mahmood Alam for their assistance in the preparation of this volume.
The hydrogenation of diphenylacetylene (DPA) on palladium–silver catalysts with a single-atom structure was investigated. It has been shown experimentally that the reaction rate of alkene to alkane hydrogenation is substantially lower than the rate of DPA semi-hydrogenation. The kinetic barriers of all stages of hydrogenation were calculated by the DFT method.
In situ XRD and NMR experiments combined with molecular dynamics simulations using the grand canonical ensemble (GCMD) show that cation size, charge and solvation energy play critical roles in determining the interlayer expansion of smectite clay minerals when exposed to dry supercritical CO2 under conditions relevant to the earthâ€™s upper crust, petroleum reservoirs, and geological CO2 sequestration conditions (323 K and 90 bar). The GCMD results show that the smectite mineral, hectorite, containing interlayer alkali and alkaline earth cations with relatively small ionic radii and high solvation and hydration energies (e.g., Li+, Na+ Mg2+, and Ca2+) does not intercalate dry CO2 and that the fully collapsed interlayer structure is the energetically most stable configuration. With increasing cation size and decreasing cation solvation energy, the energy barrier to CO2 intercalation decreases. With K+, Rb+, Cs+, Sr2+, and Ba2+ the monolayer structure is the stable configuration, and CO2 should spontaneously enter the interlayer. With Cs+ there is not even an energy barrier for CO2 intercalation, in agreement with the experimental XRD and NMR results that show clay layer expansion and CO2 incorporation. The number of intercalated CO2 molecules decreases with increasing size of the alkali cation but does not vary with ion size for the alkaline earth cations. 13C NMR spectroscopy and the GCMD simulations show that the average orientation of the intercalated CO2 molecules is with their O-C-O axes parallel to the basal clay surface and that they undergo a combination of rapid rotation about an axis perpendicular to the main molecular axis and wobbling motion with respect to the basal surface. Incorporation of CO2 in the interlayer decreases the coordination of Cs+ by the oxygen atoms of the basal surfaces, which is compensated by CO2 molecules entering their solvation shell, as predicted based on previously published NMR results. The GCMD simulations show that the strength of the interaction between the exchangeable cation and the clay structure dominates the intercalation energetics in dry scCO2. With relatively small cations, the cation-clay interactions outcompete cation solvation by CO2 molecules. The computed residence times for coordination among of interlayer species are consistent with the computed energetics.