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The solvent effect on H-BEA catalyzed cyclohexanol dehydration was investigated in water, dioxane, and cyclohexanol. The dynamic evolution of the Brønsted acid site of zeolite and its interaction with reactant molecules in different solvents were explored with ab initio molecular dynamics simulations, providing reliable configuration sampling to obtain configurations at equilibrium. Solvent profoundly changes the adsorption as well as the dehydration reaction of cyclohexanol in H-BEA, where the reaction is determined to follow the E2 mechanism in water and dioxane but the E1 mechanism in cyclohexanol untill saturation uptake. Near saturation uptake, all three solvents significantly reduce the cyclohexanol dehydration rates in H-BEA. Cyclohexanol loading also dramatically affects the kinetics of the dehydration reaction, displaying an overall decreasing trend with a local minimum present at intermediate loading of 6 molecules per unit cell, which is a result of the entropic effect associated with greater freedom of motion of the transition state. Rigorous quantification of enthalpy and entropy contributions to cyclohexanol adsorption and activation shed light on the solvent effect of zeolite-catalyzed alcohol dehydration. [ABSTRACT FROM AUTHOR]

Biomass is the most abundant and renewable resource in the pursuit of bio-value added chemicals. Platinum-group metals and typical nonprecious transition metals are considered as the active metals for catalytic conversion of biomass into value added chemicals and fuels. Rhenium (Re) in particular is a versatile, oxophilic element with a broad variety of easily accessible oxidation states ideally suited for catalytic applications. Taking advantage of Re's unique properties and the green concept of biomass, the catalytic transformation of lignocellulose with Re-based catalysts has gained considerable attention, leading to the preparation of value-added chemicals including olefins through deoxydehydration from the conversion of polyols, aromatics through depolymerization of lignin, and alkane fuels through a hydrodeoxygenation reaction. This review focuses on the catalytic conversion of lignocellulosic main components (cellulose, hemicellulose, and lignin) and their derived platform chemicals into value-added chemicals and fuels over homogeneous and heterogeneous Re-based catalysts. The reaction pathways for biomass conversion over Re-based catalysts are introduced based on different feedstocks or chemical bonds. The unique role of Re species in tailoring the active sites of catalysts for these reactions is summarized and possible reaction mechanisms are discussed. Finally, an outlook is provided to underscore both the challenges and opportunities associated with this interesting and important field, offering a comprehensive overview on the current state of Re catalysis with a low carbon footprint. [ABSTRACT FROM AUTHOR]

Carbon aerogels (CAs) have garnered significant attention due to their multifunctional applications. Biomass waste, abundantly generated by agriculture and industry, serves as a primary carbon source. However, developing a facile, sustainable, and efficient method to produce CAs from biomass waste remains challenging. In this study, a one‐step Zn2+ ion‐glue‐assisted carbonization technique was developed to produce large‐scale, high‐performance CAs. Various biomass materials (wood bits, peanut shells, bamboo bits, and straw waste) were treated in a molten salt system (ZnCl2/KCl) at 300 °C for 2 h to obtain large‐block CAs derived from biomass bits. Zn2+ ions cleave cellulose hydrogen bonds in natural biomass, facilitating the dehydration crosslinking reaction among cellulose, hemicellulose, and lignin, thus reconstructing the entire block structure. The resulting CAs exhibited high porosity (95 %) and low density (0.078 g/cm3). Numerous hydroxyl and carbonyl groups were preserved during the low‐temperature treatment, facilitating chemical modification for diverse applications. For instance, amidoxime functionalized CAs were utilized as filters for selective and highly efficient extraction of U(VI) from wastewater. The adsorption capacity and extraction efficiency reached 801.2 mg/g and 95 % with a flux rate of 6.1×103 L/m2 ⋅ h. [ABSTRACT FROM AUTHOR]

Carbon aerogels (CAs) have garnered significant attention due to their multifunctional applications. Biomass waste, abundantly generated by agriculture and industry, serves as a primary carbon source. However, developing a facile, sustainable, and efficient method to produce CAs from biomass waste remains challenging. In this study, a one‐step Zn2+ ion‐glue‐assisted carbonization technique was developed to produce large‐scale, high‐performance CAs. Various biomass materials (wood bits, peanut shells, bamboo bits, and straw waste) were treated in a molten salt system (ZnCl2/KCl) at 300 °C for 2 h to obtain large‐block CAs derived from biomass bits. Zn2+ ions cleave cellulose hydrogen bonds in natural biomass, facilitating the dehydration crosslinking reaction among cellulose, hemicellulose, and lignin, thus reconstructing the entire block structure. The resulting CAs exhibited high porosity (95 %) and low density (0.078 g/cm3). Numerous hydroxyl and carbonyl groups were preserved during the low‐temperature treatment, facilitating chemical modification for diverse applications. For instance, amidoxime functionalized CAs were utilized as filters for selective and highly efficient extraction of U(VI) from wastewater. The adsorption capacity and extraction efficiency reached 801.2 mg/g and 95 % with a flux rate of 6.1×103 L/m2 ⋅ h. [ABSTRACT FROM AUTHOR]

In single‐step conversion of glycerol to propene, the intricate catalytic pathways with molybdenum and niobium catalysts remain elusive. While these catalysts can effectively accelerate the hydrogenolytic cleavage of the glycerol CO bonds, resulting in a high selectivity to propene, the routes have not been thoroughly studied. This study explores the reaction routes and the role hydrogen plays in determining the product distribution. The hydrodeoxygenation (HDO) of glycerol was investigated using various glycerol purities in both batch and continuous reaction modes. Remarkably, Mo(PO4)x and Nb(PO4)x demonstrated catalytic performance with raw glycerol, indicating that impurities had no detrimental effect on the catalyst's activity. In batch mode, a propene selectivity of 53% was achieved over Mo(PO4)x as the catalyst, highlighting the catalyst's stability under these conditions. In continuous operation, the highest product selectivity to propene (12%) was observed at low temperatures (573 K), while more C2 to C6 alkanes were formed at increased temperatures (623 and 673 K). Whereas a hydrogen atmosphere promotes formation of 2‐propenol, as primary precursor to propene, an inert atmosphere leads to increased formation of propanal and dissociation products. Our work has elucidated new routes to upcycle biorenewable glycerol to propene over Mo(PO4)x and Nb(PO4)x catalysts. [ABSTRACT FROM AUTHOR]

Dielectric barrier discharge (DBD) nonthermal plasma is applied for the gasification of kitchen waste. The gas production performance of kitchen waste gasification based on DBD under different reaction ambientes is studied. Density functional theory (DFT) simulations are used to investigate the gas production mechanism via glucose and aspartate. Scanning electron microscopy (SEM) and Raman spectroscopy are used to investigate the physicochemical properties of the produced carbon materials and reveal the plasma reaction mechanism. The plasma treatment of millet and soybean has good gasification effect and can inhibit tar production. N2 and CO2 ambientes are more conducive to the gasification of millet and soybean. The H2 concentration in plasma‐treated millet gasification under plasma in N2 ambient can reach 4%. Glucose is finally decomposed through ring‐opening reaction, decarbonylation reaction, dehydration reaction, and carbon–carbon bond breaking. And the decomposition process of aspartic acid mainly includes decarbonylation and deammonia reaction. With the increase of gas ionization energy, the surface pore structure of the carbon material after plasma treatment is more developed, which indicates that the reaction between plasma and solid is on a layer by layer basis with the solid surface facing the inner surface. This paper aims to provide valuable theoretical support for the application of DBD in the treatment of kitchen waste. [ABSTRACT FROM AUTHOR]

The reliance on wasteful stoichiometric reagents to accomplish dehydration reactions such as esterification, amidation, and alcohol substitution is a longstanding challenge in synthetic chemistry. To address this problem, an electrochemical approach has been developed as a new conceptual platform for dehydration reactions. As a proof-of-concept demonstration, an electrochemical esterification protocol has been described that proceeds at room temperature, without acid or base additives, and without consuming stoichiometric reagents. This approach therefore overcomes key complications of esterification chemistry, and we envision that it will similarly enable improvements to a range of important, related transformations. 1 Introduction 2 An Electrochemical Design for Catalytic Dehydration 3 Electrochemical Esterification 4 Conclusions [ABSTRACT FROM AUTHOR]

Introduction of mesopore system into zeolite crystals is always deemed to be an effective strategy to improve diffusion and acidic accessibility. In this work, a hierarchically structured ZSM-5 with an ultra-small intracrystalline mesopore structure was prepared by using lysine as a pore-forming agent via a hydrothermal crystallization procedure. The structured and textured properties of the as-synthesized samples were characterized by XRD, SEM, EDS, TEM, NH3-TPD, FT-IR and N2 adsorption–desorption isothermals. The results showed that a purely-phased hierarchical ZSM-5 zeolite with a size of 2–6 nm mesopore can be obtained under the condition of lysine/Al2O3 = 2–8. The addition of lysine in the precursor not only generated an ultra-small mesopore system, but also had a significant effect on the acidity of the synthesized sample: With the increased amount of added lysine, the acid density and acid strength of the as-prepared zeolite catalyst were gradually weakened. The effects of the introduced hierarchical pore structure and the tailored acid sites on the catalytic performance of the catalysts were investigated during methanol dehydration to hydrocarbons reaction. The introduced hierarchical pores and the weakened strong acids significantly improved the stability of the catalyst. Meanwhile, the reduced acid density strongly inhibited hydrogen transfer of light olefins intermediate and then increased the selectivity toward light olefins on the hierarchical zeolite catalysts. [ABSTRACT FROM AUTHOR]

We synthesized ridaifen-B boron dipyrromethene (RID-B-BODIPY) using 2methyl-6-nitro benzoic anhydride (MNBA)-mediated dehydration condensation reaction between amino alkyl-tethered RID and BODIPY FL. Comparative experiments between dicyclohexylcarbodiimide (DCC) and MNBA for their coupling reactions demonstrated that MNBA is an effective condensation reagent for amines and BODIPY FL. A cell staining study with RID-B-BODIPY showed intracellular localization of BODIPY FL fluorescence, attributed to the RID-B structure, indicating the successful development of a tool for analyzing intracellular molecular behavior efficiently. [ABSTRACT FROM AUTHOR]

Tetrahydroquinolines are key structures in a variety of natural products with diverse pharmacological utilities and other applications. A series of 3,4-diaryl-5,7-dimethoxy-1,2,3,4-tetrahydroquinolines were synthesized in good yield by reacting 3-aryl-5,7-dimethoxy-2,3-dihydroquinolin-4-ones with different Grignard reagents followed by the dehydration of the intermediate phenolic compounds. Subsequent reduction and deprotection were carried out to achieve the desired tetrahydroquinolone moiety. The lead compound 3c showed low micromolar inhibition of various cancer cell lines. Demethylation under different reaction conditions was also investigated to afford the corresponding monohydroxy analogues. [ABSTRACT FROM AUTHOR]

5‐Hydroxymethylfurfural (HMF) was transformed into 2,5‐diformylfuran (DFF) with nitric acid as the oxidant. The initial HMF content was as high as 12.5 wt %, and water was the sole solvent. This is an intensely exothermic reaction along with the emission of NO2 gas. A high DFF yield of 83.2 % was achieved if the oxidation ability of nitric acid matched with the requirement of target oxidation reaction while mismatched those of side reactions by regulating the initial concentration of nitric acid (59.5 wt %) and reaction temperature (50–60 °C). The oxidation reaction of HMF, overoxidation of HMF, and skeleton‐cracking reaction of FDCA preferred concentrated HNO3, hot HNO3, and concentrated or hot HNO3, respectively. After liquid‐liquid extraction, filtration, and column chromatography, light‐yellow DFF powders with purity of 92.1 wt % and isolated yield of 40.2 % were obtained and confirmed by NMR, FTIR, UV‐Vis, and elemental analysis. HMF was the dominant impurity due to its affinity to DFF. In addition, chromogenic substances were obtained as a byproduct, and they were potential pH indicators. These chromogenic substances had highly conjugated molecular structures, and they were generated via successive β‐protonation‐based ring‐opening reaction of HMF, aldol reaction, and dehydration reaction. [ABSTRACT FROM AUTHOR]

D-K-type bauxite from Guizhou can be used as an unburned ceramic, adsorbent, and geopolymer after low-temperature calcination. It aims to solve the problem where the color of the D–K-type bauxite changes after calcination at different temperatures. Digital image processing technology was used to extract the color characteristics of bauxite images after 10 min of calcination at various temperatures. Then, we analyzed changes in the chemical composition and micromorphology of bauxite before and after calcination and investigated the correlation between the color characteristics of images and composition changes after bauxite calcination. The test results indicated that after calcining bauxite at 500 °C to 1000 °C for 10 min, more obvious dehydration and decarburization reactions occurred. The main component gradually changed from diaspore to Al2O3, the chromaticity value of the image decreased from 0.0980 to 0.0515, the saturation value increased from 0.0161 to 0.2433, and the brightness value increased from 0.5890 to 0.7177. Studies have shown that changes in bauxite color characteristics are strongly correlated with changes in composition. This is important for directing bauxite calcination based on digital image processing from engineering viewpoints. [ABSTRACT FROM AUTHOR]

Microbial non-phosphorylative oxidative pathways present promising potential in the biosynthesis of platform chemicals from the hemicellulosic fraction of lignocellulose. An L-arabinonate dehydratase from Rhizobium leguminosarum bv. trifolii catalyzes the rate-limiting step in the non-phosphorylative oxidative pathways, that is, converts sugar acid to 2-dehydro-3-deoxy sugar acid. We have shown earlier that the enzyme forms a dimer of dimers, in which the C-terminal histidine residue from one monomer participates in the formation of the active site of an adjacent monomer. The histidine appears to be conserved across the sequences of sugar acid dehydratases. To study the role of the C-terminus, five variants (H579A, H579F, H579L, H579Q, and H579W) were produced. All variants showed decreased activity for the tested sugar acid substrates, except the variant H579L on D-fuconate, which showed about 20% increase in activity. The reaction kinetic data showed that the substrate preference was slightly modified in H579L compared to the wild-type enzyme, demonstrating that the alternation of the substrate preference of sugar acid dehydratases is possible. In addition, a crystal structure of H579L was determined at 2.4 Å with a product analog 2-oxobutyrate. This is the first enzyme-ligand complex structure from an IlvD/EDD superfamily enzyme. The binding of 2-oxobutyrate suggests how the substrate would bind into the active site in the orientation, which could lead to the dehydration reaction. Key points: • Mutation of the last histidine at the C-terminus changed the catalytic activity of L-arabinonate dehydratase from R. leguminosarum bv. trifolii against various C5/C6 sugar acids. • The variant H579L of L-arabinonate dehydratase showed an alteration of substrate preferences compared with the wild type. • The first enzyme-ligand complex crystal structure of an IlvD/EDD superfamily enzyme was solved. [ABSTRACT FROM AUTHOR]

Increases in temperature and pressure caused by rapid burial of sediments seaward of the Sumatra subduction zone have been hypothesized to trigger dehydration reactions that diagenetically strengthen sediments and contribute to the formation of an over‐pressured pre‐décollement, which together facilitate the occurrence of large shallow earthquakes. We present paleomagnetic, rock magnetic, and electron microscopic analyses from drill cores collected offshore Sumatra at Site U1480 during IODP Expedition 362 that support this hypothesis. The older pre‐fan units (Late Cretaceous to early Paleocene) were deposited when Site U1480 was moving rapidly northward with the Indian plate from a paleolatitude of 50° to 30°S, which would equate to expected absolute paleomagnetic inclinations of 70°–43°. Most of the older pre‐fan sediments, however, have shallow observed inclinations (shallower than ±20°), indicating that the sediments were overprinted when Site U1480 was located near the paleoequator, as it has been since the early Oligocene. Electron microscopic observations reveal that the pre‐existing detrital magnetite grains have undergone pervasive dissolution and alteration by hydrothermal fluids. The diagenesis observed is consistent with mineral dehydration, possibly driven by rapid burial of pelagic sediments by the ∼1250 m thick Nicobar Fan sequence. In addition, the elevated burial temperature also facilitated the smectite to illite conversion reaction. We hypothesize that chemical reactions resulted in the formation of fine‐grained magnetite that records a chemical remanent magnetization overprint. This overprint is consistent with the alteration occurring after burial by the thick Nicobar Fan sequence sometime in the past few million years. Plain Language Summary: Sediments and rocks commonly contain magnetic minerals that record the direction and intensity of Earth's magnetic field as they are being emplaced, thus preserving an ancient record of the geomagnetic field. Subsequent alteration of the magnetic minerals caused by heating and/or fluid circulation can result in the acquisition of secondary magnetizations (i.e., remagnetization) that may overprint or completely reset the primary ancient magnetization. Such remagnetization provides evidence of the physical and chemical changes that have occurred. Here through paleomagnetic, rock magnetic, and microscopic analyses of the deeper older (pre‐fan) stratigraphic sequence cored offshore Sumatra, we find that hydrothermal fluids, resulting from mineral dehydration driven by rapid burial of this sequence by younger, thick Nicobar Fan sediments, led to pervasive secondary remagnetization. Consequently, the newly formed magnetite recorded a much younger paleomagnetic field, leaving a shallow overprint that probably occurred sometime in the past few million years. The dehydration reactions also increased the strength of the sediments entering the subduction zone and aided in the formation of slip surfaces (called décollements), possibly contributing to the shallow, large earthquakes that have generated tsunamis off Sumatra. Key Points: The 60–67 Ma pre‐fan sediments offshore Sumatra were most likely remagnetized since deposition of the Nicobar Fan sediments, which began at ∼9 MaRemagnetization of pre‐fan sediments caused by mineral dehydration may be linked to shallow seismogenic slip off SumatraMagnetic properties of input sediments in the subduction margin record conditions that may have facilitated the generation of earthquakes [ABSTRACT FROM AUTHOR]

The objective of this research was to convert xylose into furfural using flax straw‐based bifunctional solid acid catalyst. The catalyst was synthesized by impregnation‐carbonization and sulfonation processes. The characterization of biochar, Al‐biochar, and sulfonated Al‐biochar catalyst were carried out by using Brunauer–EmmetTeller (BET), Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). The results showed that the surface area, total acid density, and SO3H density of sulfonated Al‐biochar catalyst were 516.03 m2/g, 4.767 ± 0.23 mmol/g and 1.033 ± 0.1 mmol/g, respectively. The result of FTIR indicated that the presence of the different functional groups such as the phenolic group (‐OH), carboxylic group (‐COOH), sulfoxide group (‐SO3H), and Al‐O‐Al on the surface of the prepared catalyst. The catalytic performance of the synthesized catalyst was evaluated in a biphasic system of water and 2‐methyl tetra hydro furan. The effects of dehydration reaction parameters (reaction temperature, reaction time, and catalyst loading) on the formation of furfural were also studied. The maximum furfural formation was obtained at 180°C, 2 hr, and 0.2 gm of catalyst loading. Under this condition, the yield of furfural was around 64.7%, with a selectivity of 88.0%. The study demonstrated the effectiveness of the catalyst in the transformation of xylose into furfural. [ABSTRACT FROM AUTHOR]

Inorganic perovskites, with Cs+ substituting volatile organic components, show great promise in photovoltaic applications due to their outstanding optoelectronic properties and thermal stability. However, the black‐to‐yellow phase transition of CsPbI3 remains a challenge for realizing high‐performance inorganic perovskite solar cells (IPSCs). Herein, an effective approach is reported via incorporating the self‐assembled molecule Me‐4PACz to synergistically stabilize the [PbI6]4− octahedra and form a hydrophobic layer at interface and grain boundaries. An in situ dehydration condensation reaction of Me‐4PACz is observed during film annealing, which favors the reduction of undesired aggregation of Me‐4PACz in humid air, thus leading to enhanced anchoring interaction and more effective hydrophobic protection of CsPbI3. Therefore, the air‐processed CsPbI3 perovskite films show dramatically improved phase purity and humid stability. This strategy also improves the energy level alignment between perovskite and charge transport layers. As a result, a champion efficiency of 20.21% is realized, representing one of the highest reported values for air‐processed inverted IPSCs. Furthermore, it is demonstrated that by combining Me‐4PACz with the previously reported ethacridine lactate (EAL) additive, the device performance can be further boosted to 21.38%, which is a record efficiency for the inverted IPSCs reported to date. [ABSTRACT FROM AUTHOR]

The conversion of Methyl 3‐hydroxypropionate (3‐HPM) to 1,3‐propanediol (1, 3‐PDO) is an important step in the pathway towards the longterm sustainable production of the ethylene oxide hydroesterification. However, 3‐HPM is prone to side reactions like hydroxyl β‐dehydration and low reaction efficiency, which hinders its development. This study presents the first‐ever report on highly efficient gallium‐promoted Cu/SiO2 catalysts prepared using ethanol‐assisted ammonia‐evaporation (Et‐AE) for converting 3‐HPM to 1,3‐PDO. The prepared Cu‐1Ga/SiO2 catalyst exhibited satisfactory catalytic activity and 1,3‐PDO selectivity in the hydrogenation reaction, with a conversion of 3‐HPM of 94 % and a selectivity to 1,3‐PDO of 91 %. The characterisation results show that the addition of Ga increases the specific surface area and the pore volume of the catalyst, and also increases the dispersion of the Cu species. And the promotional effect likely originates from interactions between Ga3+ and Cu0 species though enhanced ability of the latter to activate H2. In addition, the introduction of Ga into the catalyst increases the interaction between Cu and the support, making it more difficult for Cu+ to be completely reduced to Cu0. This increases the content of Cu+ in the catalyst, which is beneficial for improving the activity and stability of the catalyst. This study investigates modifying Cu catalysts to provide guidelines for obtaining high performing hydrogenation catalysts. [ABSTRACT FROM AUTHOR]

Chromium and molybdenum incorporated MgO and MgO–C catalysts were synthesized for hydrogen production from a non-oxidative ethane dehydration reaction. Hydrogen production studies were carried out using a microwave-heated reactor system. The study investigated the effects of reaction temperature, type of active metal, and catalyst preparation method (physical mixture or core–shell structure) on hydrogen selectivity and ethane conversion during dehydrogenation reactions. The results showed that the optimal reaction temperature for the non-oxidative ethane dehydration reaction was 450 °C. Above this temperature, the selectivity of undesired byproducts increased. Catalysts containing molybdenum exhibited higher ethane conversion. Moreover, a comparison of MgO–C-supported catalysts with MgO-supported catalysts revealed that the core–shell catalysts exhibited superior ethane conversion. Notably, the 5Mo@MgO–C catalyst demonstrated exceptional catalytic activity, achieving a high ethane conversion rate of 72% along with excellent stability. [ABSTRACT FROM AUTHOR]

Aiming to optimize the product distribution of the Cu–Al catalytic system in the oxalate hydrogenation reaction as a way to optimize and improve the product structure of the coal-to-ethylene glycol process (Coal-Oxalate-EG), the researchers have investigated the two anchoring sites for anchoring the Cu component that is available in the Al2O3 support. The results show that the catalyst xSB synthesized from Al2O3 enriched with surface –OH functional groups is superior to the catalyst xSol synthesized from Al2O3 enriched with Al3+Penta sites for oxalate conversion, whereas xSol outperforms the xSB catalyst for the formation of alcohol-ether ester chemicals. Using diethyl oxalate (DEO) as feedstock, the reaction temperature of the 1Sol catalyst (235 °C) was higher than that of the 1SB catalyst (205 °C) for the conversion of the same amount of DEO at the same Cu loading. Meanwhile, the chemical selectivity of alcohol ether esters was higher for the 1Sol catalyst (~ 35%) than for the 1SB (~ 20%). Detailed characterization (XRD, NH3-TPD, XPS, in-situ FTIR, TEM, etc.) shows that the Al3+Penta sites are mainly present in the bulk phase of Al2O3, and the number of Al3+Penta sites present on the surface of the carriers is only sufficient to maintain the low content of Cu species in a highly dispersed state. A certain number of Al–OH is still required for the anchoring of the Cu species to the Al2O3 support surface. Therefore, hydroxyl-rich SB carriers are more favorable for the high dispersion of Cu species. Meanwhile, the stronger LAS distributed on the surface of the hydroxyl-rich SB carrier will lead to the decomposition or dehydration of the raw materials and intermediates during the reaction process, resulting in the formation of lower molecular weight products, which is unfavorable to the formation of the alcohol-ether ester products. Based on the detailed reaction data and characterization, a more complete product formation pathway of oxalate in the Cu–Al catalytic system is given, which provides a certain theoretical basis for the development of new coal-based chemical pathways. [ABSTRACT FROM AUTHOR]

This article discusses the use of iodine(III)-mediated ring-contraction reactions in both halogenated and non-halogenated solvents. The study compares the yields of ring-contraction reactions using different solvents and investigates the behavior of different derivatives of 1,2-dihydronaphthalene. The results show that using halogenated solvents leads to higher yields. The article also provides a detailed account of the synthesis and purification of various organic compounds, including their yields, physical properties, and spectroscopic data. Additionally, it provides information on the synthesis and characterization of three specific compounds, along with supporting information for further reference. [Extracted from the article]

A series of solvatomorphic structures of the anti-inflammatory drug diclofenac (dcfn−) and the dense hydrogen bond donor propane-1,3-diaminium (H2pn2+) are reported. Single crystal X-ray diffraction shows each structure contains a dcfn2·H2pn formula unit (1) with solvent of crystallisation [1·2H2O, 1·3H2O, 1·2MeOH, 1·EtOH·2H2O, 1·iPrOH, 1·2DMSO]. The propane-1,3-diaminium molecules evoke extensive networks of hydrogen-bonded interactions with the solvates and the dcfn carboxylate groups. All structures are lamellar with hydrophilic solvate-containing sheets separating hydrophobic layers of aromatic dcfn moieties. Supporting characterisations by powder X-ray diffraction, Fourier transform infrared and 1H NMR spectroscopies, thermal analysis (TG–DSC) and elemental microanalysis were used to reveal the sometimes delicate phase distributions amongst this set of compounds. TG–DSC showed a consistent pattern across the water and alcohol-containing compounds with desolvation occurring before melting to an anhydrous ionic liquid form around 140–150 °C. Heating to approximately 200 °C induces a minor dehydration reaction that covalently links diclofenac and propan-1,3-diaminium molecules via amide bond formation. A mechanochemical synthetic route to 1·3H2O was determined and this compound was selected for study by gravimetric water vapour adsorption. These studies showed the lamellar structure of 1·3H2O displays reversible but imperfect water adsorption between 0% and 50% relative humidity, which is ascribed to some crystal fatigue. This work expands crystal engineering strategies for new and existing active pharmaceutical ingredients to low molecular weight diamines. [ABSTRACT FROM AUTHOR]

Hierarchical SAPO-34 zeolite catalysts were successfully synthesized via a one-step hydrothermal synthesis approach with the assistance of excess triethylamine (TEA). Compared with conventional SAPO-34 (SP-T3), SAPO-34 synthesized with a TEA/Al2O3 molar ratio of 9 (SP-T9) presents high catalytic performance in the ethanol dehydration reaction due to its pseudocubic morphology with abundant butterfly-like large secondary pores and slightly decreased surface acidity. Afterwards, a cost-effective and green route is developed for synthesizing hierarchical SAPO-34 catalysts by recycling waste mother liquids. In recycling processes, residual organic templates in the mother liquids are reused in the next synthesis of SAPO-34 without adding fresh templates. After three recycles of mother liquids, the synthesized SP-R3 catalyst still retains its high crystallinity, hierarchical structure, moderate acidity, and excellent catalytic performance in ethanol dehydration as compared to the initial SP-T9 catalyst. [ABSTRACT FROM AUTHOR]

Polar stratospheric clouds (PSCs) form in polar regions, typically between 15 and 25 km above mean sea level, when the local temperature is sufficiently low. PSCs play an important role in the ozone chemistry and the dehydration and denitrification of the stratosphere. Lidars with a depolarization channel may be used to detect and classify different classes of PSCs. The main PSC classes are water ice, nitric acid trihydrate (NAT), and supercooled ternary solutions (STSs), the latter being liquid droplets consisting of water, nitric acid, and sulfuric acid. PSCs have been observed at the lidar observatory at Concordia Station from 2014 onward. The harsh environmental conditions at Concordia during winter render successful lidar operation difficult. To facilitate the operation of the observatory, several measures have been put in place to achieve an almost complete remote control of the system. PSC occurrence is strongly correlated with local temperatures and is affected by dynamics, as the PSC coverage during the observation season shows. PSC observations in 2021 are shown as an example of the capability and functionality of the lidar observatory. A comparison of the observations with the satellite-borne CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar has been made to demonstrate the quality of the data and their representativeness for the Antarctic Plateau. [ABSTRACT FROM AUTHOR]

Antigorite is the high‐temperature member of the serpentine group minerals and is broadly considered a primary carrier of water in the subducting oceanic lithosphere. It has a wavy crystal structure along its a‐axis and several polysomes with different m‐values (m = 13–24) have been identified in nature. The m‐value is defined as the number of tetrahedra in one wavelength and is controlled by the misfit between the octahedral and tetrahedral layers. The degree of misfit primarily depends on the volumes of the MgO6 octehedra and SiO4 tetrahedra within the layers, which vary as a function of pressure and temperature. However, it is not well understood which m‐values of antigorite are stable at different pressure and temperature conditions. To investigate the pressure dependence of the stability of different m‐values in antigorite, we performed first‐principles calculations for several polysomes (m = 14–19) at high pressure from 0 to 14 GPa and compared their enthalpies at static 0 K. We found that although the energy differences between polysomes are small, polysomes with larger m‐values are more stable at ambient pressure, while polysomes with smaller m‐values are more stable at elevated pressures. This suggests that the structure of antigorite in the oceanic lithosphere subducting into the deep Earth may gradually evolve into a different polysome structure than the antigorite samples observed at ambient or near‐surface pressure conditions. These changes in the m‐values are accompanied by a minor dehydration reaction. By modulating the available amount of free water in the system, antigorite polysomatism may influence the distribution of intermediate‐depth seismicity, such as the observance of double seismic zones. Plain Language Summary: Antigorite is a hydrous mineral known for being an important carrier of water into the Earth's interior and a seismicity trigger at intermediate‐depths down to ∼200 km. However, its crystal structure is complex (e.g., Uehara, 1998), and thus it is not well understood which structural variant (polysome) of antigorite is stable or dominant at high pressures and temperatures during subduction. In this study, several crystal structures of antigorite were calculated by first‐principles calculations, and their enthalpies (i.e., Gibbs free energy of a system at static 0 K) were compared to determine the stable structure as a function of pressure. The results indicate that the structure and chemical composition of antigorite likely changes under high pressure, resulting in the gradual release of water during the subduction process. As antigorite is thought to be the main trigger of seismicity in the subducting lithospheric mantle, its metasomatism may contribute to explain the reported distributions of intermediate‐depth earthquakes. Key Points: Antigorite crystal structures with various values of m (14–19) were determined by first‐principles calculation under pressureThe relative enthalpy shows that antigorite with smaller m‐values are stabilized with increased pressureAntigorite in suducting slabs may gradually dehydrate under high pressure as a result of changes to stable m‐values [ABSTRACT FROM AUTHOR]

An intramolecular electrochemical dehydration reaction of dicarboxylic acids to their cyclic anhydrides is presented. This electrolysis allows dicarboxylic acids as naturally abundant, inexpensive, safe, and readily available starting materials to be transformed into carboxylic anhydrides under mild reaction conditions. No conventional dehydration reagent is required. The obtained cyclic anhydrides are highly valuable reagents in organic synthesis, and in this report, we use them in‐situ for acylation reactions of amines to synthesize amides. This work is part of the recent progress in electrochemical dehydration, which – in contrast to electrochemical dehydrogenative reactions for example – is an underexplored field of research. The reaction mechanism was investigated by 18O isotope labeling, revealing the formation of sulfate by electrochemical oxidation and hydrolysis of the thiocyanate‐supporting electrolyte. This transformation is not a classical Kolbe electrolysis, because it is non‐decarboxylative, and all carbon atoms of the carboxylic acid starting material are contained in the carboxylic anhydride. In total, 20 examples are shown with NMR yields up to 71 %. [ABSTRACT FROM AUTHOR]

Zinc‐organic batteries (ZOBs) are receiving widespread attention as up‐and‐coming energy‐storage systems due to their sustainability, operational safety and low cost. Charge carrier is one of the critical factors affecting the redox kinetics and electrochemical performances of ZOBs. Compared with conventional large‐sized and sluggish Zn2+ storage, non‐metallic charge carriers with small hydrated size and light weight show accelerated interfacial dehydration and fast reaction kinetics, enabling superior electrochemical metrics for ZOBs. Thus, it is valuable and ongoing works to build better ZOBs with non‐metallic ion storage. In this review, versatile non‐metallic cationic (H+, NH4+) and anionic (Cl−, OH−, CF3SO3−, SO42−) charge carriers of ZOBs are first categorized with a brief comparison of their respective physicochemical properties and chemical interactions with redox‐active organic materials. Furthermore, this work highlights the implementation effectiveness of non‐metallic ions in ZOBs, giving insights into the impact of ion types on the metrics (capacity, rate capability, operation voltage, and cycle life) of organic cathodes. Finally, the challenges and perspectives of non‐metal‐ion‐based ZOBs are outlined to guild the future development of next‐generation energy communities. [ABSTRACT FROM AUTHOR]

The document titled "Thresholds of Temperature and Time for Mars Sample Return: Final Report of the Mars Sample Return Temperature-Time Tiger Team" provides valuable information on the potential risks and effects of exposing Mars Sample Return (MSR) samples to specific temperature ranges. The report was conducted by a team of scientists from various disciplines to assess the impact of temperature on the integrity and scientific value of the samples. It discusses the potential reactions and processes that may occur when samples collected from Mars are heated, including the release of volatiles, chemical reactions, and effects on inorganic and organic materials. The document also emphasizes the importance of preserving hydrated minerals and the potential impact of temperature changes on the scientific analysis and interpretation of the samples. Additionally, it discusses the potential risks and challenges associated with the MSR mission, including the presence of terrestrial contaminants and the assessment of potential Martian life in the samples. Overall, this document provides valuable insights for library patrons conducting research on Mars Sample Return and the impact of temperature on sample preservation and scientific analysis. [Extracted from the article]

High-performance Cu catalysts were developed for the selective hydrogenation of γ-butyrolactone (GBL) to 1,4-butanediol (BDO). Among the various catalysts prepared by ammonia evaporation (AE) and impregnation (IM) methods with silica or MFI zeolite supports, the 5% Cu-SiO2-AE catalyst was the best one. It exhibited 95% selectivity for BDO and 71% conversion of GBL after 2–8 h reaction at 200 °C and 4 MPa H2, with high stability in five-cycle runs. Comprehensive characterizations showed that the AE method favored generating nano Cu particles with an average size of 2.9 nm on the 5% Cu-SiO2-AE catalyst. The silica support derived from a sol demonstrated an advantage over the MFI zeolite in the preparation of a highly dispersed and stable Cu catalyst, in view of its anti-sintering and robust composition of Cu0, Cu+, and Cu2+ in the cycling operation. The reaction pathways for GBL to BDO over the Cu catalysts were found to commonly involve reversible reactions of hydrogenation and dehydrogenation, along with subsequent dehydration to form THF. The high performance of the Cu catalysts in the conversion of GBL to BDO was attributed to the high dispersion of Cu, the presence of stable active sites, and fewer strong acid sites in the catalyst. [ABSTRACT FROM AUTHOR]

Aldoxime dehydratases (Oxds) have received considerable attention recently due to their application in the asymmetric synthesis of nitriles without cyanide by catalyzing the dehydration of aldoxime. However, the low stability of Oxds remains a huge obstacle to achieving high conversions and productivities of hydrophobic substrates. OxdPsp was immobilized on a macroporous adsorption resin (IOP) via an ATPS coupled with in situ immobilization. IOP-catalyzed dehydration of 2-phenylpropanal oxime (1) to prepare (S)-2-phenylpropanenitrile ((S)-2) was successfully performed with 95.7% yield, 94.1% ee and 98.6% conversion. The enriched (S)-nitrile (ee 94.1%) was obtained by using (E)-enriched aldoximes (E/Z = 97/3) as the substrate, which is consistent with the Gröger enantiopreference rule. A kinetic model to predict the dehydration catalyzed by IOP was established with an average deviation of 7.6%. The IOP-catalyzed dehydration reaction follows a sequential mechanism including substrate and product inhibition. Developing a kinetic model is a key step in the application of artificial intelligence in chemical engineering. After three recycling steps of IOP, the yield of (S)-2 still reached 83.6%, indicating that the stability of IOP was greatly enhanced, which was attributed to employing an organic solvent with a higher lg P value as the working medium and the immobilization protocol. [ABSTRACT FROM AUTHOR]

Catalytic pyrolysis of low-rank coal is currently an effective method for producing high-quality tar and gas. In this study, catalytic upgrading of volatiles from Naomaohu (NMH) coal pyrolysis has been conducted in a two-stage fixed-bed reactor using combined CaO and Ni/olivine (Ni-loaded olivine) catalysts. The effect of catalyst distribution modes and catalytic temperature on the tar and gas quality has been investigated. Simulated distillation and GC-MS analysis have been used to investigate the distribution of tar components. The results indicated that the light oil fraction in tar dramatically increased due to the combination of CaO and Ni/olivine. The CaO-Ni/olivine mode is especially better compared to the layouts of the Ni/olivine-CaO mode and the mixed mode. The CaO-Ni/olivine mode ensures a higher light fraction in tar at 69.3% and a light oil fraction at 29.8% at a catalytic temperature of 450 °C, while the heavy tar fraction decreased to 30.7%. Meanwhile, the contents of benzene (heteroatomic substituents) in tar significantly increased from 2.55% to 6.45% compared with the blank test. In this scenario, CaO breaks down macromolecular compounds in tar and cleaves long-chain esters to produce aliphatic hydrocarbons. These hydrocarbons are then dehydrogenated to produce lighter aromatic hydrocarbons over the CaO surface. Subsequently, the volatiles pass through the Ni/olivine catalysis, where ether compounds are produced by means of dehydration reactions. In addition, the CaO absorbs the CO2 in the pyrolysis gas, leading to an elevation of CH4 and H2 concentration. Particularly, the concentration of H2 significantly increased from 16.2% to 30.37%, while the concentration of CO2 significantly decreased from 37.9% to 10.57%. These findings suggest that the usage of combined CaO and Ni/olivine catalysts is beneficial for improving both the tar and gas quality. [ABSTRACT FROM AUTHOR]

The stability and breakdown of mineral phases in subducting slabs control the cycling of trace elements through subduction zones. Stability of key minerals and the partitioning of trace elements between these minerals and liquid phases of interests have been charted by natural sample analysis and experimental constraints. However, systematic study from arc front to far back arc has rarely shown that the expected geochemical variations of the slab liquid are actually recorded by natural samples. Complexities arise by uncertainties on the nature of the slab component (melts, fluids and supercritical liquids), source heterogeneities and transport processes. Using data from olivine-hosted melt inclusions sampled along and across the NE Japan and southern Kurile arcs, we demonstrate that experimentally and thermodynamically constrained phase stabilities in subducted materials indeed control the trace element signatures as predicted by these models and experiments. The main reactions that can be traced across arc are progressive breakdown of light rare earth element-rich accessory phases (e.g. allanite), enhanced dehydration of the lithospheric mantle (serpentine breakdown) and changes in the nature of the slab component. This work elucidates subduction zone elemental cycling in a well-characterized petrogenetic setting and provides important constraints on the interpretation of trace element ratios in arc magmas in terms of the prograde metamorphic reactions within the subducting slab. [ABSTRACT FROM AUTHOR]

Mesoporous nano-sized γ–Al2O3 and γ–Al2O3–CeO2 (20 wt% CeO2) catalysts were successfully synthesized through a sol–gel surfactant-free process, using cerium nitrate and aluminum nitrate as precursors. The obtained γ-aluminas were then characterized by scanning and transmission electron microscopy, powder X-ray diffraction, thermogravimetric analysis (TGA), and temperature-programmed desorption with ammonia. Afterward, the structural properties of the prepared catalysts were monitored through surface area analysis measurements. Finally, the catalytic activity of the obtained aluminas were studied in methanol dehydration reaction. Methanol conversion and selectivities to different products were measured at different reaction temperatures by gas chromatography. The optimum temperature of catalytic reaction in the presence of alumina-ceria was 300 °C due to 100% DME selectivity and 91% methanol conversion. [ABSTRACT FROM AUTHOR]

Two 2,4,6-trimethylaniline-based trifuloromethanesulfonate (trifluoromethanesulfonate) salts were synthesized and characterized by single-crystal X-ray diffraction. N,2,4,6-Tetramethylanilinium trifluoromethanesulfonate, [C10H14NH2+][CF3O3S-] (1), was synthesized via methylation of 2,4,6-trimethylaniline. N-Isopropylidene-N,2,4,6-tetramethylanilinium trifluoromethanesulfonate, [C13H20N+][CF3O3S-] (2), was synthesized in a two-step reaction where the imine, N-isopropylidene-2,4,6-trimethylaniline, was first prepared via a dehydration reaction to form the Schiff base, followed by methylation using methyl trifluoromethanesulfonate to form the iminium ion. In compound 1, both hydrogen bonding and p-p interactions form the main intermolecular interactions. The primary interaction is a strong N--H...O hydrogen bond with the oxygen atoms of the trifluoromethanesulfonate anions bonded to the hydrogen atoms of the ammonium nitrogen atom to generate a one-dimensional chain. The [C10H14NH2+] cations form dimers where the benzene rings form a p-p interaction with a parallel-displaced geometry. The separation distance between the calculated centroids of the benzene rings is 3.9129 (8) Å, and the interplanar spacing and ring slippage between the dimers are 3.5156 (5) and 1.718 Å, respectively. For 2, the [C13H20N+] cations also form dimers as in 1, but with the benzene rings highly slipped. The distance between the calculated centroids of the benzene rings is 4.8937 (8) Å, and interplanar spacing and ring slippage are 3.3646 (5) and 3.553 Å, respectively. The major intermolecular interactions in 2 are instead a series of weaker C--H...O hydrogen bonds [C...O distances of 3.1723 (17), 3.3789 (18), and 3.3789 (18) Å], an interaction virtually absent in the structure of 1. Fluorine atoms are not involved in strong directional interactions in either structure. [ABSTRACT FROM AUTHOR]

X-ray computed tomography has established itself as a crucial tool in the analysis of rock materials, providing the ability to visualise intricate 3D microstructures and capture quantitative information about internal phenomena such as structural damage, mineral reactions, and fluid–rock interactions. The efficacy of this tool, however, depends significantly on the precision of image segmentation, a process that has seen varied results across different methodologies, ranging from simple histogram thresholding to more complex machine learning and deep-learning strategies. The irregularity in these segmentation outcomes raises concerns about the reproducibility of the results, a challenge that we aim to address in this work. In our study, we employ the mass balance of a metamorphic reaction as an internal standard to verify segmentation accuracy and shed light on the advantages of deep-learning approaches, particularly their capacity to efficiently process expansive datasets. Our methodology utilises deep learning to achieve accurate segmentation of time-resolved volumetric images of the gypsum dehydration reaction, a process that traditional segmentation techniques have struggled with due to poor contrast between reactants and products. We utilise a 2D U-net architecture for segmentation and introduce machine-learning-obtained labelled data (specifically, from random forest classification) as an innovative solution to the limitations of training data obtained from imaging. The deep-learning algorithm we developed has demonstrated remarkable resilience, consistently segmenting volume phases across all experiments. Furthermore, our trained neural network exhibits impressively short run times on a standard workstation equipped with a graphic processing unit (GPU). To evaluate the precision of our workflow, we compared the theoretical and measured molar evolution of gypsum to bassanite during dehydration. The errors between the predicted and segmented volumes in all time series experiments fell within the 2 % confidence intervals of the theoretical curves, affirming the accuracy of our methodology. We also compared the results obtained by the proposed method with standard segmentation methods and found a significant improvement in precision and accuracy of segmented volumes. This makes the segmented computed tomography images suited for extracting quantitative data, such as variations in mineral growth rate and pore size during the reaction. In this work, we introduce a distinctive approach by using an internal standard to validate the accuracy of a segmentation model, demonstrating its potential as a robust and reliable method for image segmentation in this field. This ability to measure the volumetric evolution during a reaction with precision paves the way for advanced modelling and verification of the physical properties of rock materials, particularly those involved in tectono-metamorphic processes. Our work underscores the promise of deep-learning approaches in elevating the quality and reproducibility of research in the geosciences. [ABSTRACT FROM AUTHOR]

The tobacco waste generated from the tobacco agriculture and industry, including the discarded stem and leaf, often needs dehydration pretreatment before thermal conversion utilization. In order to study the water activity and migration of tobacco waste during the pretreatment process, TG-NMR (Thermogravimetric Nuclear Magnetic Resonance) was used to obtain the drying curves and LF-NMR (Low Field Nuclear Magnetic Resonance) T2 inversion spectrum at each stage of tobacco drying. Meanwhile, the variation pattern of pore distribution during the dehydration process of two types of tobacco waste has been obtained. Combined with the pore distribution changes, a possible spatial migration mode of water was proposed. The change of adsorption energy of water during tobacco drying was calculated, and verified the above hypothesis. This study results provide reference for the optimization of dehydration pretreatment process for different tobacco waste in order to reduce energy consumption during recycling of tobacco biomass. [ABSTRACT FROM AUTHOR]

Upcycling biodegradable polyester waste into value-added chemicals can not only avoid CO2 emissions but also achieve sustainable carbon recycling. Herein, we report a one-pot catalytic process to deconstruct polycaprolactone into 6-aminocaproic acid (EACA) and caprolactam (CPL), two monomers of nylon-6, using aqueous ammonia and Ru catalysts. No additional hydrogen is required, and the total yield of EACA and CPL could reach 90.2% using a ternary catalyst, Ru/CeO2/RGO, at 140 °C. It is verified that 6-hydroxyhexanoic acid and 6-hydroxyhexanoamide are the initial intermediates resulting from polycaprolactone decomposition, which undergo dehydrogenation, amination and re-hydrogenation to transform into EACA and 6-aminohexanoamide over the Ru catalyst. The hydrolysis of 6-aminohexanoamide produces EACA, and the reverse reaction between dehydration of EACA and hydrolysis of CPL results in their coexistence. The protocol demonstrated here provides a novel route to recycle polycaprolactone to valuable chemicals. [ABSTRACT FROM AUTHOR]

In this study, a zero‐gap flow‐through microfluidic reactor was constructed for the degradation of tetracycline and norfloxacin in water using a porous Ti/RuO2‐IrO2@Pt electrode as the anode and porous titanium plate as the cathode. The operation parameters included electrolyte type, electrolyte concentration, current density, initial concentration of pollutants and pH, were investigated. The degradation efficiency and energy consumption were calculated and compared with traditional electrolyzer. In the zero‐gap flow‐through microfluidic reactor, 100 % of both tetracycline and norfloxacin can be decomposed in 15 min, and high mineralization rate were achieved under the optimized reaction condition. And the reaction was consistent with pseudo‐first‐order kinetics with k value of 0.492 cm−1 and 1.010 cm−1, for tetracycline and norfloxacin, respectively. In addition, the energy consumption was 28.33 kWh ⋅ kg−1 TC and 8.36 kWh ⋅ kg−1 NOR, for tetracycline and norfloxacin, respectively, which was much lower than that of traditional electrolyzer. The LC–MS results showed that tetracycline underwent a series of demethylation, dehydration and deamination reactions, and the norfloxacin went through ring opening reaction, decarboxylation and hydroxylation reaction, and finally both produced CO2 and H2O. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solvent recirculation is a feasible strategy to valorize the HTC aqueous waste. • HTC moderate temperatures favor additional hydrochar formation during recirculation. • HTC of blended biomasses enhances hydrochar recovery at 180 °C. • Process water recirculation promotes dehydration and decarboxylation reactions. • A significantly higher energy recovery is achieved by process water recirculation. This study aims at valorizing the residual aqueous phase from hydrothermal carbonization (HTC) of Sicilian agro-wastes in order to enhance the hydrochar recovery, positively affecting the process energy balance. Process waters (PW) obtained from HTC and co-HTC using orange peel waste and fennel plant residues were used as recycled solvent in experiments carried out at the temperatures of 180 and 230 °C. The results showed that an additional hydrochar formation was promoted during recirculation of solvent, leading to average increments of solid mass yield of 10.5 wt% for tests conducted at 180 °C and 3.9 wt% for 230 °C. After five consecutive recirculation phases in co-HTC runs, the hydrochar yield increased up to 18.2 wt%. The low H/C and O/C atomic ratios values, found after recirculation, indicate that organic acids, accumulated in the PW, may catalyze the process and promote the biomass deoxygenation by boosting dehydration and decarboxylation. The recovered PWs from conversion steps with deionized water were also carbonized in absence of the solid feedstock in order to quantify their contribution in hydrochar formation during recirculation and thus the synergistic interactions. After recirculation, energy recovery averagely augmented by more than threefold, showing that the proposed strategy could significantly improve the sustainability of HTC. [ABSTRACT FROM AUTHOR]

Bio-based acetaldehyde production by non-oxidative dehydrogenation of ethanol is a promising alternative for the fine chemistry industry, where acetaldehyde is an important part of the synthesis chain and co-production of hydrogen. In this paper, investigations on nickel containing alumina itterbia stabilized zirconia with microwave-assisted synthesis as catalysts for the ethanol dehydrogenation process to acetaldehyde are reported. Ni–xAl2O3–(100 − x)[Zr0,97Yb0,03]O2 (x = 35 and 65 mol%) were prepared by using microwave (MW) irradiation and by traditional heating steps during sol–gel preparation. The textural properties, structure, morphology, surface and phase composition, and RedOx properties (SEM–EDX, BET N2-physisorption, TG–DTA, XRD, EPR) of the samples were compared with the effect of the microwave-assisted synthesis and the Zr:Al ratio on the ethanol dehydrogenation is reported. Two synthesis routes were compared, and it was found that microwave pretreatment of hydrogel during sol–gel synthesis favors catalytic dehydrogenation, whereas catalysts prepared by pretreatment under uniform heating perform much worse. The microwave-assisted synthesis approach turned out to be more promising in terms of selectivity to acetaldehyde in the ethanol dehydrogenation due to form nickel oxide particles with strong support interaction in noncubic coordination catalyzing the ethanol dehydrogenation and at the same time to decrease the formation of nickel aluminate phase involved in competitive dehydration reaction to ethylene. Thus, the highest obtained selectivity to acetaldehyde was ≈ 70% at 400 °C on Ni–65AZ–MW sample. [ABSTRACT FROM AUTHOR]

A density functional theoretical (DFT) study is presented, implicating a 1O2 oxidation process to reach a dihydrobenzofuran from the reaction of the natural homoallylic alcohol, glycocitrine. Our results predict an interconversion between glycocitrine and an iso‐hydroperoxide intermediate [R(H)O+–O−] that provides a key path in the chemistry which then follows. Formations of allylic hydroperoxides are unlikely from a 1O2 'ene' reaction. Instead, the dihydrobenzofuran arises by 1O2 oxidation facilitated by a 16° curvature of the glycocitrine ring imposed by a pyramidal N‐methyl group. This curvature facilitates the formation of the iso‐hydroperoxide, which is analogous to the iso species CH2I+–I− and CHI2+–I− formed by UV photolysis of CH2I2 and CHI3. The iso‐hydroperoxide is also structurally reminiscent of carbonyl oxides (R2C=O+–O−) formed in the reaction of carbenes and oxygen. Our DFT results point to intermolecular process, in which the iso‐hydroperoxide's fate relates to O‐transfer and H2O dehydration reactions for new insight into the biosynthesis of dihydrobenzofuran natural products. [ABSTRACT FROM AUTHOR]

Pargasite stability was experimentally studied in IHPV at = 2 kbar and temperatures of 1000 to 1100oC, with equilibrium approached from above and below. Calcic amphibole was used to experimentally model processes that occur in a volcanic chamber at pressures up to 5 kbar. The phase diagram of pargasite has been refined. It has been established that the stability of pargasite is controlled by three reactions. (1) At low water pressures of less than 1 kbar, the dehydration reaction Prg = Fo + Sp + Di + Ne + An + H2O proceeds. (2) At water pressures higher than 1.2–1.5 kbar and a temperature of about 1100°C, the decomposition of pargasite is controlled by its incongruent melting Prg = Fo + Sp + {Di + Ne + An}L + H2O. (3) The third reaction Prg + L = Fo + Sp + Di + {Ne + Pl}L + H2O occurs within the same pressure range as the previous one but at lower temperatures of about ~1050°C. The reaction controls the pargasite liquidus and is caused by interaction between amphibole and coexisting melt. The liquidus of pargasite seems to most strongly depend on the activity of silica in the melt. [ABSTRACT FROM AUTHOR]

The electrolytic reduction of CO2 in aqueous media promises a pathway for the utilization of the green house gas by converting it to base chemicals or building blocks thereof. However, the technology is currently not economically feasible, where one reason lies in insufficient reaction rates and selectivities. Current research of CO2 electrolysis is becoming aware of the importance of the local environment and reactions at the electrodes and their proximity, which can be only assessed under true catalytic conditions, i.e. by in operando techniques. In this work, multinuclear in operando NMR techniques were applied in order to investigate the evolution of the electrolyte chemistry during CO2 electrolysis. The CO2 electroreduction was performed in aqueous NaHCO3 or KHCO3 electrolytes at silver electrodes. Based on 13C and 23Na NMR studies at different magnetic fields, it was found that the dynamic equilibrium of the electrolyte salt in solution, existing as ion pairs and free ions, decelerates with increasingly negative potential. In turn, this equilibrium affects the resupply rate of CO2 to the electrolysis reaction from the electrolyte. Substantiated by relaxation measurements, a mechanism was proposed where stable ion pairs in solution catalyze the bicarbonate dehydration reaction, which may provide a new pathway for improving educt resupply during CO2 electrolysis. The electrolytic reduction of CO2 in aqueous media promises a pathway for the utilization of the greenhouse gas by converting it to base chemicals, however, reactions at the electrodes and their proximity remain challenging to elucidate. Here, the authors use multinuclear in operando NMR to study CO2 electrolysis in aqueous media and find that stable ion pairs in solution catalyze the bicarbonate dehydration reaction. [ABSTRACT FROM AUTHOR]

Gem-quality rubies and sapphires are often commercially heat treated at about 800 °C or higher to enhance their color and clarity, and hence quality. For this study, selected corundum samples containing diaspore and goethite inclusions were heated step-by-step to a maximum of 1000 °C with the aim of monitoring the dehydration and phase transformation of these oxyhydroxides to corundum and hematite during heating. Based on our experiments and in agreement with the literature, the dehydration of diaspore in corundum occurs between 525 and 550 °C, whereas goethite transforms to hematite between 300 and 325 °C. As both diaspore and goethite may be present as inclusions in rubies, sapphires, and other corundum varieties (e.g., pink sapphires, padparadscha), these dehydration reactions and phase transformations can be considered important criteria to separate unheated from heated stones, specifically in cases in which other methods (e.g., microscopy, FTIR) are unsuccessful. [ABSTRACT FROM AUTHOR]

3-Hydroxypropionic acid (3-HP) is a key building block for value-added chemicals. A biological route for synthesizing this molecule is two-step enzymatic reactions; dehydration of glycerol to 3-hydroxypropanal (3-HPA) by glycerol dehydratase and then oxidation of 3-HPA to 3-HP by aldehyde dehydrogenase. Here, we report an aldehyde dehydrogenase, an engineered α-ketoglutaric semialdehyde dehydrogenase (KGSADH) from Azospirillum brasilense. The variant, named 2C10, was obtained by applying a large KGSADH library to a selection method based on a 3-HP-responsive transcription factor and then a screening method for observing the activities of individual clones. 2C10 exhibited a 4.65-fold higher catalytic activity (kcat/Km: 100 ± 7.1 s−1mM−1) toward 3-HPA than the wild-type enzyme. The flask culture of Pseudomonas denitrificans with 2C10 resulted in an approximately 30% increase in 3-HP titer (43.2 mM) compared with that obtained using wild-type KGSADH (33.1 mM). Molecular dynamics simulations suggested that compared to the wild-type enzyme, 2C10 has a less flexible and smaller binding pocket for aldehyde substrates. [ABSTRACT FROM AUTHOR]

In this study, SiC and Ga2O3 substrates were bonded under atmospheric conditions using an extremely thin amorphous layer (∼7 Å). Conventional wafer-bonding techniques employ an oxidizing treatment for surface functionalization, resulting in the formation of an oxide layer at the bonding interface. This study demonstrates the bonding of a hydrofluoric-acid-treated SiC surface with a plasma-activated Ga2O3 substrate, where the –OH groups on the SiC and Ga2O3 surfaces form direct bonding via a dehydration reaction at 250 °C. The interfacial analysis indicates that bonding using the reduction treatment instead of oxidization reduces the thickness of the intermediate layer at the SiC/Ga2O3 interface, which is a thermal and electrical barrier. In addition, it is remarkable that the SiC and Ga2O3 substrates are directly bonded by generally used surface cleaning processes, contacting the surfaces under atmospheric conditions, and annealing at 250 °C. We believe that the bonding process using the reduction process can contribute to future heterogeneous devices based on integrated dissimilar substrates. [ABSTRACT FROM AUTHOR]

Gentiopicrin, the main component of the famous Chinese patent medicine Long Dan Xie Gan Wan, has the characteristics of fast absorption in vivo and low bioavailability. Intestinal bacteria play an important role in the absorption and pharmacokinetics of oral drugs. In this study, the metabolic transformation of gentiopicrin by intestinal bacteria was examined. High-performance liquid chromatography coupled with ion trap time-of-flight mass spectrometry (LC/MSn-IT-TOF) and nuclear magnetic resonance (NMR) were used, and six metabolites were identified, including reduction products (G-M1, G-M2, G-M4, and G-M6), a hydrolytic product (G-M3), and a dehydration product (G-M5) of gentiopicrin aglycone after hydrolysis, reduction, and dehydration reactions were performed by the intestinal flora. This is the first time that chiral metabolites of gentiopicrin (G-M1 and G-M2) were found in this study. In addition, the precursors of glucuronic acid conjugates previously reported in vivo may have come from the intestinal bacterial metabolites G-M1, G-M2, and G-M3. In addition, the metabolic transformation of gentiopicrin in liver microsomes was studied in vitro, and it was found that gentiopicrin did not undergo metabolic transformation under the action of liver microsomes. It is suggested that gentiopicroside may be metabolized in the intestine. This study provides both new insight regarding the investigation of effective substances and an exploration of the pharmacodynamic and toxicological properties of gentiopicrin. [ABSTRACT FROM AUTHOR]

Grisemycin, salinipeptin, and cypemycin belong to the linaridin class of ribosomally synthesized and posttranslationally modified peptides that contain multiple dehydrobutyrine and D-amino acid residues. The biosynthetic gene clusters of these linaridins lack obvious candidate genes for the dehydratase and epimerase required to introduce dehydrobutyrine and D-amino acid residues, respectively. However, we previously demonstrated that the grisemycin (grm) cluster contained cryptic dehydratase and epimerase genes by heterologous expression of this biosynthetic gene cluster in Streptomyces lividans and proposed that two genes (grmH and grmL) with unknown functions catalyze dehydration and epimerization reactions. In this study, we confirmed that both GrmH and GrmL, which were shown to constitute a protein complex by a co-purification experiment, were required to catalyze the dehydration, epimerization, and proteolytic cleavage of a precursor peptide GrmA by in vivo experiments. Furthermore, we demonstrated that GrmH/GrmL complex accepted salinipeptin and cypemycin precursor peptides, which possess three additional amino acids. GrmH and GrmL in linaridin natural product biosynthesis constitute an enzyme complex catalyzing dehydration, epimerization, and leader peptide removal. [ABSTRACT FROM AUTHOR]

The pathways of dehydration reaction of both calcium atorvastatin trihydrate (CAT) and grinded CAT were investigated using CRTA technique under controlled residual water vapor pressure of 5 hPa using complementary analysis techniques, namely TG, DSC and XRD. The results show that the studied sample is a pure atorvastatin in its trihydrated form and that, under CRTA conditions, it dehydrates in three separated steps between 261 and 393 K, each corresponds to the loss of one water molecule. On the other hand, the grinded CAT dehydrates in one step. From the duration of the CRTA experiment and the X-ray diffraction technique, we have showed that the grinding partially dehydrates CAT, to obtain calcium atorvastatin 1.5 H2O, while decreasing its crystallinity. Also, examination by X-ray diffraction technique of the CRTA final products of both, CAT and grinded CAT, showed that the anhydrous phase of CAT is crystallized, whereas the one of the grinded CAT is amorphous. The apparent activation energies corresponding to the dehydration steps of intact CAT (39 kJ mol−1 and 34 kJ mol−1) and grinded CAT (126 kJ mol−1 and 289 kJ mol−1) were obtained by means of two CRTA curves realized at two different reaction rates without any hypothesis on the kinetic model of the reaction. [ABSTRACT FROM AUTHOR]

A green and straightforward electrosynthesis of substituted indoles has been developed through dehydration and intramolecular dehydrogenative C-N bond-forming radical cross-coupling from 1-(2-aminophenyl)alcohols under metal, iodine and oxidant-free conditions. This electrochemical indole synthesis strategy has an excellent functional group, water and air tolerance. And, a possible cyclization process was proposed based on the radical-trapping, intermediate verification, cyclic voltammetry, EPR and control experiments. [ABSTRACT FROM AUTHOR]