Chondroitin sulfate (CS) is present in many animal tissues with various sulfation patterns and is important in biological events. Mechanisms of interaction between CS and signal proteins have been widely investigated to allow the chemical synthesis of CS oligosaccharides. Sophisticated synthetic approaches adopting de novo synthesis starting from the corresponding monosaccharide have mainly been performed. This strategy usually employs stepwise glycan elongation, protecting group manipulation, and regiospecific sulfate formation to systematically obtain different types of bioactive CS oligosaccharides. On the other hand, the semi-synthetic method via optimized hydrolysis of CS polymer was performed for obtaining repeating disaccharide as an alternative strategy. The disaccharide unit obtained was again manipulated to form the desired CS oligosaccharides equipped with sulfates at specific positions. In addition, chemical reconstruction including regiospecific sulfate formation of natural CS and CS-like polysaccharides has recently been explored. This review overviews the synthetic approaches to obtain biofunctional CS oligosaccharides emphasizing these aspects.
Verifiable and accurate prediction of reservoir pore sizes from well logs in a well with no previous exposure of core data is the desirable outcome for any technique intended to estimate pore size. Many methods are based on core and crushed rock samples such as thin section analysis, scanning electron microscope (SEM) and mercury intrusion capillary pressure (MICP) to characterize pore features but these methods are not commonly used because of their high cost. This study introduces a cost-effective approach to establish a relationship between hydraulic flow unit and pore size distribution using routine core analysis data and geophysical well logs. Multi-parameter cluster analysis is used to classify the reservoir rock volume into hydraulic flow unit with similar rock characteristics using reservoir quality index (RQI) and flow zone indicators. Well log and core analysis data were used to identify the hydraulic flow unit in the reservoir interval. The discriminant approach was then applied to the predicted hydraulic flow unit to access the range of pore sizes. The predicted hydraulic flow unit with high porosity and permeability and high RQI revealed a range of pore sizes (macro and mega pores). Comparing the obtained results with high-resolution rock thin section study and available empirical approaches indicated verifiable and satisfactory results. The study can extrapolate the pore size information vertically as well as in the neighboring wells in a quite simple and economical way.
Atmospheric residue fractions were characterized based on detailed structure analysis data obtained from petroleomics. The physical properties of each fraction were analyzed by applying the estimation method with molecular weight and specific gravity (Method 1) and by applying the group-contribution estimation method with the molecular structure data (Method 2). Vapor-liquid equilibria (VLE) for water + atmospheric residue (AR) systems were measured at 603-643 K and 2.0-10.2 MPa with a flow type apparatus and predicted using the Peng-Robinson equation. Average absolute relative deviations of predicted water content in the liquid phase were 25.4 % for Method 1 and 9.9 % for Method 2, suggesting that the group-contribution estimation method is more reliable.
Zeolite membranes can be used for separation and purification of natural gas. Natural gas contains mainly methane and carbon dioxide, but also contains acidic gases, such as hydrogen sulfide, and water. The application of conventional zeolite membranes containing aluminum to these separation processes is difficult because of poor acid durability and reduced flux in the presence of water. Pure silica zeolite membranes have high acid stability and are hydrophobic. In this study, STT-type zeolite was chosen as a membrane material for the relatively high pore volume and pure silica STT-type zeolite can be prepared. STT-type zeolite was milled in a ball mill for 8 h, and then coated on a porous alumina substrate. STT-type zeolite membranes were prepared by the secondary growth method. Times for synthesis of the STT-type zeolite particles and ball milling were optimized. The effects on permeance of synthesis time, and of the structure-directing agent/SiO2 and H2O/SiO2 ratios for secondary growth were investigated. STT-type zeolite membrane prepared from gel with a mole ratio of 1.0 SiO2 : 0.25 N,N,N-trimethyl-1-adamantane ammonium hydroxide : 54 H2O with hydrothermal synthesis for 8 days at 150 °C had high permeance ratio (169) for hydrogen to sulfur hexafluoride (SF6).
Organic chemical hydrides are one of the most promising methods for hydrogen storage, but aromatic compound remains unreacted after the hydrogenation process due to equilibrium limitations. We attempted to develop a solid-state adsorbent which could selectively adsorb toluene from methylcyclohexane (MCH)–toluene mixture. Several La-based oxides were tested and La0.8Ba0.2CoO3 − δ (LBCO) was found to exhibit high adsorption and selectivity for toluene. Analyses of the electronic state and adsorption state of toluene found part of the Co ions in the LBCO lattice were Co4+. Co4+ in the lattice and surface lattice oxygen are important for the selective adsorption of toluene.
Effects of ligand and ligand substituents in a series of (imido)vanadium(V) complexes containing monodentate anionic ancillary donor ligands of the type, V(NAr)Cl2(L) [Ar = 2,6-Me2C6H3; L = OAr, O-2,6-Ph2C6H3, N = CtBu2, 1,3-tBu2(CHN)2C = N, WCA-NHC (anionic N-heterocyclic carbenes with a weakly coordinating borate moiety)] and V(NAd)Cl2(OAr) (Ad = 1-adamantyl), were explored by the solution V K-edge XANES (pre-edge and edge region) spectra. No significant differences in the pre-edge (and the edge) peaks were observed between these complexes which fold a distorted 4 coordinate tetrahedral geometry around vanadium; the shoulder-edge peaks ascribed to the presence of V_Cl bonds were also observed in all cases. No significant spectral changes were observed when the phenoxy analogues (exhibiting catalytic activities for ethylene/norbornene copolymerization) were treated with MAO, and even addition of norbornene, suggesting preservation of the oxidation state. Remarkable changes in the XANES spectrum (decrease in the intensity of the pre-edge peak and low-energy shift of the edge region) were observed after addition of AliBu3 toward V(NAr)Cl2(WCA-NHC), and no notable changes were observed upon further addition of AliBu3 and norbornene; these results suggest that the formed species, presumably vanadium(III), act directly as the active species in this catalysis.
To establish guidelines for the development of high activity hydrodesulfurization catalysts, first-principles calculations were carried out with Al2O3 as the catalyst support and MoS2 as the supported metal species, focusing on the TiO2 coating and support-metal interaction. MoS2 clusters were modeled on the surfaces of Al2O3 and TiO2 and the adsorption energy was calculated. TiO2 showed stronger interaction with MoS2 than Al2O3. MoS2 clusters were also modeled on Al2O3 supports coated with thin films of TiO2, and the adsorption energy was calculated. Adsorption energy depended on the number of stacked film layers, suggesting that thin film thickness can be optimized. An amorphous Al2O3 support model was created to approach the real surface state and adsorption calculations were performed. Adsorption energy was higher than with a crystalline support, and the presence of sites where more stable adsorption would occur was confirmed.
We propose a novel method to upgrade heavy oil. This method utilizes dealkylation of alkyl polycyclic aromatic hydrocarbons on a silica monolayer solid acid catalyst to produce alkanes with preserved alkyl chain length and aromatic hydrocarbons without alkyl groups, resulting in maximization of the yields of value-added products, alkanes suitable for diesel fuel and alkylbenzenes suitable for gasoline and chemical feedstocks. Basic compounds in vacuum gas oil were found to inhibit the reaction, but were removed by treatment with solid acids such as strongly acidic cation exchange resin and amorphous silica_alumina. Drying of the silica_alumina significantly enhanced the removal rate. The silica_alumina was repeatedly usable by calcination in an oxygen flow. After the treatments for the removal of basic compounds, dealkylation of alkyl polycyclic aromatic hydrocarbons proceeded at 673 K. However, rapid catalyst deactivation was observed. Higher reaction temperature of 723 K suppressed deactivation of the catalyst and maintained the high selectivity. Even in the optimized conditions, slow deactivation of the catalyst was observed, but the catalyst was regenerated by calcination at 773 K in oxygen, and the catalytic performance was repeatedly demonstrated.
Utilization of lignocellulosic biomass for alternative fuels requires efficient and low-cost processes for deoxygenation and conversion to hydrocarbons. We propose a 2-step biomass conversion process consisting of solvolysis pretreatment and co-processing with heavy petroleum oil in catalytic cracking. High liquefied yield (> 90 C%) was achieved by solvolysis in guaiacol and water with acetic acid catalysts. Bio-oil was mainly converted to gaseous hydrocarbons and coke by co-processing with model heavy oil (n-eicosane). Deoxygenation pathway to H2O formation was accelerated by enhancing hydrogen-transfer activity even without supplying hydrogen. Hydrogen-transfer deoxygenation proceeded preferentially to olefin hydrogenation. Consequently, enhancing hydrogen-transfer activity in the co-processing of bio-oil and heavy petroleum oil was effective for efficient deoxygenation without lowering octane rating.
Metal-containing MFI-type zeolites were hydrothermally synthesized in the absence of Al species and alkali cations and used for the direct dehydrogenation of n-butane to evaluate the catalytic properties. Zn-, Fe-, and Ni-containing MFI zeolites exhibited high catalytic activities, and predominantly produced 1,3-butadiene. Furthermore, Zn-containing MFI zeolites prepared by hydrothermal treatment in the absence of alkali cations showed significantly higher yields of 1,3-butadiene compared to ZnO loaded on silicalite-1 by impregnation.
Catalytic direct decomposition of t-butyl mercaptan (TBM), which is a sulfur compound added to city gas as an odorant, was investigated over H-beta zeolite catalyst without hydrogen addition. High TBM conversion was achieved at the initial stage of the reaction at 60 °C, and hydrogen sulfide was only detected in the outlet gas. Subsequently, TBM conversion decreased and concentration of isobutene increased. TBM was stably decomposed to hydrogen sulfide and isobutene after 490 min, indicating that the activity of H-beta zeolite was sufficiently durable. Temperature programmed oxidation (TPO) analysis of the spent catalyst suggested that hydrocarbon species were desorbed below 300 °C and carbon species were oxidized to carbon dioxide above 300 °C. Spent catalyst heated under a flow of air at 300 °C completely recovered the catalytic activity. Therefore, hydrocarbon species formed at the initial stage of the reaction were oligomerized within the zeolite pores and caused the decrease in catalytic activity for TBM decomposition.