Enhancement of the Sorption Ability of Aluminum Oxide Desiccants by Alkaline Modification

The influence of impregnation of aluminum oxide desiccants prepared by centrifugal thermal activation of hydrargillite with alkali (KОН and NaOH) and carbonate (Na₂CO₃ and K₂СО₃) solutions on the physicochemical properties of the products was studied. Impregnation with alkali solutions increases the dynamic capacity of the desiccants by a factor of 2 and more, whereas impregnation with carbonate solutions decreases the sorption characteristics of the desiccants at similar texture characteristics. Introduction of alkaline modifiers leads to a considerable decrease in the concentration of Lewis acid sites on the surface and to an increase in the concentration of strong base sites. Linear correlation was revealed between the concentration of strong base sites on the surface of the desiccants and their dynamic capacity in drying of humid air. The desiccants modified by impregnation exhibit not only high static and dynamic capacity, allowing improvement of the drying efficiency, but also considerably enhanced mechanical strength.     

Highly effective water adsorbents based on aluminum oxide

A method of preparation of a stable, high performance water adsorbent with the phase composition η-Al₂O₃ + γ-Al₂O₃ + χ-Al₂O₃ from thermally activated hydrargillite has been developed. The synthesis procedure does not involve a reprecipitation stage. The resulting adsorbent has a high specific surface area (400 m²/g) and a mean pore diameter of 3.5 nm or below. The static capacity of the adsorbent reaches 24.2 g H₂O per 100 g of sorbent, and its dynamic capacity is 8.2 g H₂O per 100 g of sorbent. Service life tests showed the stability of the adsorbent in multiple sorption-desorption cycles. The minimum dew point in drying is ?58.8°C.     

Calorimetric measurement of the heat of desorption of water vapor from amorphous and crystalline lactose

The heat required to release and vaporize bound H₂O from crystalline α-lactose monohydrate and from lactose glass, as determined by differential scanning calorimetry is 12.3±0.7 and 10.8±0.5 kcal·mole⁻¹ of H₂O, respectively. Water vapor sorption by anhydrous α-lactose leads to the formation of the α-monohydrate. The isotherm, obtained gravimetrically for this process is Langmuir type. β-Lactose is completely non-hygroscopic below 97% relative humidity. Thereafter, it sorbs H₂O rapidly to form a concentrated solution wherein the lactose is capable of mutarotation. Densites of lactose forms determined pycnometrically by helium displacement are: 1.535 g/cm³ for α-lactose·H₂O; 1.547 g/cm³ for anhydrous α-lactose; and 1.576 g/cm³ for β-lactose.     

Water-soluble double potassium and ammonium salts of iron(III) and manganese(II) with (hydroxyethylidene)diphosphonic acid

A method to multifold increase the water solubility of diiron(III) tris[(hydroxyethylidene)-diphosphonate) tetrahydrate Fe₂(H₂L)₃·4H₂O and manganese(II) (hydroxyethylidene)diphosphonate dihydrate MnH₂L·2H₂O, prepared by the reaction of 1-hydroxyethylidene-1,1-diphosphonic acid with iron(III)hydroxide and basic manganese carbonate. The method involves conversion of the phosphonates into their double salts Fe₂K₆L₃·4H₂O [Fe₂(NH₄)₆L₃·4H₂O] and MnK_1.3H_0.7L·2H₂O [Mn(NH₄)₂L·2H₂O] by treatment of their aqueous suspensions with potassium or ammonium hydroxides. The solubility of the iron salt increases from 0.2 to 4.0 g per 100 mL solution (20 times) and that of the manganese salt increases from 0.1 to 4.8 g per 100 mL solution (45 times).     

Fine Tuning of MOF‐505 Analogues To Reduce Low‐Pressure Methane Uptake and Enhance Methane Working Capacity

We present a crystal engineering strategy to fine tune the pore chemistry and CH₄‐storage performance of a family of isomorphic MOFs based upon PCN‐14. These MOFs exhibit similar pore size, pore surface, and surface area (around 3000 m² g⁻¹) and were prepared with the goal to enhance CH₄ working capacity. [Cu₂(L2)(H₂O)₂]_n (NJU‐Bai 41: NJU‐Bai for Nanjing University Bai's group), [Cu₂(L3)(H₂O)₂]_n (NJU‐Bai 42), and [Cu₂(L4)(DMF)₂]_n (NJU‐Bai 43) were prepared and we observed that the CH₄ volumetric working capacity and volumetric uptake values are influenced by subtle changes in structure and chemistry. In particular, the CH₄ working capacity of NJU‐Bai 43 reaches 198 cm³ (STP: 273.15 K, 1 atm) cm⁻³ at 298 K and 65 bar, which is amongst the highest reported for MOFs under these conditions and is much higher than the corresponding value for PCN‐14 (157 cm³ (STP) cm⁻³).     

Effect of Functionalized Groups on Gas‐Adsorption Properties: Syntheses of Functionalized Microporous Metal–Organic Frameworks and Their High Gas‐Storage Capacity

The microporous metal–organic framework (MMOF) Zn₄O(L1)₂ ? 9 DMF ? 9 H₂O ( 1‐H ) and its functionalized derivatives Zn₄O(L1‐CH₃)₂ ? 9 DMF ? 9 H₂O ( 2‐CH₃ ) and Zn₄O(L1‐Cl)₂ ? 9 DMF ? 9 H₂O ( 3‐Cl ) have been synthesized and characterized (H₃L1=4‐[N,N‐bis(4‐methylbenzoic acid)amino]benzoic acid, H₃L1‐CH₃=4‐[N,N‐bis(4‐methylbenzoic acid)amino]‐2‐methylbenzoic acid, H₃L1‐Cl=4‐[N,N‐bis(4‐methylbenzoic acid)amino]‐2‐chlorobenzoic acid). Single‐crystal X‐ray diffraction analyses confirmed that the two functionalized MMOFs are isostructural to their parent MMOF, and are twofold interpenetrated three‐dimensional (3D) microporous frameworks. All of the samples possess enduring porosity with Langmuir surface areas over 1950 cm² g^?1. Their pore volumes and surface areas decrease in the order 1‐H > 2‐CH₃ > 3‐Cl . Gas‐adsorption studies show that the H₂ uptakes of these samples are among the highest of the MMOFs (2.37 wt % for 3‐Cl at 77 K and 1 bar), although their structures are interpenetrating. Furthermore, this work reveals that the adsorbate–adsorbent interaction plays a more important role in the gas‐adsorption properties of these samples at low pressure, whereas the effects of the pore volumes and surface areas dominate the gas‐adsorption properties at high pressure.     

An Unexplored O2‐Involved Pathway for the Decarboxylation of Saturated Carboxylic Acids by TiO2 Photocatalysis: An Isotopic Probe Study

The aerobic decarboxylation of saturated carboxylic acids (from C₂ to C₅) in water by TiO₂ photocatalysis was systematically investigated in this work. It was found that the split of C¹? C² bond of the acids to release CO₂ proceeds sequentially (that is, a C₅ acid sequentially forms C₄ products, then C₃ and so forth). As a model reaction, the decarboxylation of propionic acid to produce acetic acid was tracked by using isotopic‐labeled H₂¹⁸O. As much as ≈42 % of oxygen atoms of the produced acetic acids were from dioxygen (¹⁶O₂). Through diffuse reflectance FTIR measurements (DRIFTS), we confirmed that an intermediate pyruvic acid was generated prior to the cut‐off of the initial carboxyl group; this intermediate was evidenced by the appearance of an absorption peak at 1772 cm^?1 (attributed to C?O stretch of α‐keto group of pyruvic acid) and the shift of this peak to 1726 cm^?1 when H₂¹⁶O was replaced by H₂¹⁸O. Consequently, pyruvic acid was chosen as another model molecule to observe how its decarboxylation occurs in H₂¹⁶O under an atmosphere of ¹⁸O₂. With the α‐keto oxygen of pyruvic acid preserved in the carboxyl group of acetic acid, ≈24 % new oxygen atoms of the produced acetic acid were from molecular oxygen at near 100 % conversion of pyruvic acid. The other ≈76 % oxygen atoms were provided by H₂O through hole/OH radical oxidation. In the presence of conduction band electrons, O₂ can independently accomplish such C¹? C² bond cleavage of pyruvic acid to generate acetic acid with ≈100 % selectivity, as confirmed by an electrochemical experiment carried out in the dark. More importantly, the ratio of O₂ participation in decarboxylation increased along with the increase of pyruvic acid conversion, indicating the differences between non‐substituted acids and α‐keto acids. This also suggests that the O₂‐dependent decarboxylation competes with hole/OH‐radical‐promoted decarboxylation and depends on TiO₂ surface defects at which Ti_4c sites are available for the simultaneous coordination of substrates and O₂.     

Properties of new inorganic membranes prepared by metal alkoxide methods Part II: New inorganic-organic anion-exchange membranes prepared by the modified metal alkoxide methods with silane coupling agents

Four types of inorganic-organic anion exchangeable membranes were prepared on a microporous alumina substrate by dipcoating with solution containing Si(OC₂H₅)₄, C₂H₅OH, H₂O, CH₃COOH, two silane coupling agents in molar ratio 1:6.8:2:0.03:0.02, and on a silica membrane by liquid-phase coupling method with two solutions containing C₆H₅CH₃, H₂O, 2-(trimethoxysilyl)ethyl-2-pyridine in molar ratio 11:0.06:0.04 or C₂H₅OH, H₂O, N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride in molar ratio 21:0.06:0.06. The alumina substrate and silica membrane showed cation exchangeability, but membranes dip-coated and liquid-phase coupled showed anion exchangeability and their ion-exchange capacity per unit area of membrane surface were in the range 4–9 × 10⁻³ meq. cm⁻². The static transport number for liquid-phase coupled membranes was in the range of 0.6–0.9, but for dip-coated membranes it was 0.5.     

NO2 removal on adsorbents prepared from coffee industry waste materials

A technology for obtaining carbonaceous adsorbents by physical and chemical activation of waste materials from coffee industry is described. The effect of pyrolysis temperature and type of activation procedure on the textural parameters, acid–base character of the surface and sorption properties of activated carbons has been tested. The resulting carbons were characterized by low-temperature nitrogen sorption, determination of pH and the number of surface oxygen groups. The sorption properties of the activated carbons obtained were characterized by evaluation of nitrogen dioxide adsorption in dry and wet conditions. The final products were adsorbents of specific surface area ranging from 5 to 2,076 m²/g and pore volume from 0.03 to 1.25 cm³/g, showing very diverse acidic–basic character of the surface. The results obtained in our study have proved that a suitable choice of the pyrolysis and activation procedure for coffee industry wastes permits production of adsorbents with high sorption capacity of nitrogen dioxide, reaching to 44.5 and 84.1 mg NO₂/g in dry and wet conditions, respectively.     

Synthesis of Polysiloxane Xerogels Using Tetraethoxysilane/(Diethylphosphatoethyl)triethoxysilane System

The xerogels, containing phosphonic acid groups ≡Si(CH₂)₂P(O)(OC₂H₅)₂ in the surface layer of their particles, are synthesized by the sol-gel method (ethanol as a solvent and fluoride ion as a catalyst). It is shown that, when 2 : 1, 3 : 1, and 4 : 1 tetraethoxysilane/(diethylphosphatoethyl)triethoxysilane ratios are used, nonporous substances are formed, whereas, at 6 : 1, 8 : 1, and 10 : 1 ratios, the xerogels with highly porous structures are produced (the specific surface area is 505–534 m²/g, the sorption pore volume is 0.34–0.53 cm³/g, and the pore diameter is 3.6–4.6 nm).     

Structure Cristalline du Phosphite Acide de Calcium,Ca(HPO3H)2 · H2O

Crystal Structure of Calcium Hydrogenphosphite Monohydrate, Ca(HPO₃H)₂ · H₂O Ca(HPO₃H)₂ · H₂O is triclinic, space group P1 , with a = 7.007(1), b = 8.100(1), c = 6.773(1) Å, α = 84.92(1), β = 95.72(2) and γ = 112.00(1)°; V = 354.1 ų, Z = 2; ?_x = 2.251 g/cm³ and ?_ob = 2.21(1) g³/cm³. The structure was refined to R = 0.019 for 1640 independent reflections. HPO₃H^? ions are linked together by hydrogen bonds (with acid hydrogen atoms) to form parallelograms. Chains of parallelograms are parallel to c axis. The coordination number of the calcium ion is seven; the mean values of Ca? O is 2.409 Å.     

Layer-By-Layer (LBL) hybrid MOF coating for graphene-based multilayer composite: Synthesis and application as anode for lithium ion batteries

The hybrid anodic materials with high porosity and low charge resistance exhibit high specific capacity and stable cyclic stability for lithium ion battery (LIBs). For this purpose, three-dimensional hollow material, metal organic framework (MOF-199) was coated over the active surface of oxidized derivative of graphene (Graphene oxide, GO), via layer-by-layer (LBL) coating method. Cupric acetate and benzene-1,3,5-tricarboxylic acid [Cu₃(BTC)₂], were alternatively coated on the active surface of GO as an anode material, to enhance the structural diversity and reduce the synergistic effect of insertion and extraction of Li⁺ ions for LIBs. Sharp absorption peaks from 1620 cm⁻¹ to 1360 cm⁻¹ and intense ring bends ∼1000 cm⁻¹ was identified through FTIR. Powder XRD provides the evidence for size reduction of Cu₃(BTC)₂@GO composite (32.6 nm) comparative to GO (43.7 nm). Outcome of EIS analysis shows the charge transfer resistance of simple GO is 2410 Ω, which is 4 times higher than R_ct of Cu₃(BTC)₂@GO composite (590 Ω). Similarly the Warburg impedance co-efficient for simple GO (448.8 Ωs^−1/2) is also higher than A_w of Cu₃(BTC)₂@GO composite (77.64 Ωs^−1/2). The synthesized material show high initial charge/discharge capacity, 1200/1420 mAh/g with 85% Coulombic efficiency and reversible discharge capacity, 1296 mAh/g after 100 cycles at 100 mA/g current density. The 98.9% Coulombic efficiency and 91% retaining capacity of composite at 100th cycle with cyclic stability, provides the phenomenon approach towards the rechargeable LIBs for industrial technology.     

Densimetric Studies of Binary Solutions Involving H2O or D2O as a Solute in Dimethylsulfoxide at Temperatures from (293.15 to 328.15) K and Atmospheric Pressure

Densities of H₂O and D₂O solutions in dimethylsulfoxide, with solute mole fractions ranging up to 0.037, were measured with an uncertainty of 1.5×10^?5?g?cm^?3 at eight temperatures between 293.15 and 328.15?K (with a step of 5?K) under atmospheric pressure using a sealed vibrating-tube densimeter. Apparent molar volumes and isobaric expansibilities (down to infinite dilution) of water isotopologues, as well as excess molar volumes of both solutes and solutions as a whole, were calculated. The temperature-dependent behavior of H₂O??D₂O solute isotope effects on the studied molar volumetric characteristics was interpreted by taking into account the structural and related interaction peculiarities of the dissolving medium in question.     

Capacitive and textural characteristics of manganese oxide prepared by anodic deposition: effects of manganese precursors and oxide thickness

The influence of manganese precursors on the deposition rate of hydrous manganese oxide in the amorphous form (denoted as a-MnO_x·nH₂O) and the effect of oxide thickness on the electrochemical properties of a-MnO_x·nH₂O, for application as electrochemical supercapacitors, were systematically investigated in this work. The results showed that Mn(CH₃COO)₂·4H₂O is a more promising precursor because of its high deposition rate at much lower potentials in comparison with MnSO₄·5H₂O, MnCl₂·4H₂O, and Mn(NO₃)₂·4H₂O. The capacitive characteristics of a-MnO_x·nH₂O were found to be independent of precursors, probably due to the fact that the mean oxidation state of Mn is not significantly affected by changing the anions of manganese precursors (from the XPS results). The capacity of oxide deposits was found to be proportional to the charge density of deposition (i.e., loading) of a-MnO_x·nH₂O when it was equal to or less than a critical value (ca. 3.5 C cm^–2), while poorer capacitive behavior with a lower capacity was clearly found beyond this critical value. The a-MnO_x·nH₂O deposit with 3.5 C cm^–2, exhibiting an acceptable capacitive performance, showed the highest capacity of energy storage for supercapacitors.     

Syntheses,Structures and Magnetic Properties of Three New Extended Iron‐containing Heteropolytungstates

Three new extended iron‐containing heteropolytungstates were synthesized and structurally characterized: K₆[{Fe^II(H₂O)₄}₂(H₂W₁₂O₄₂)]·15H₂O ( 1 ), Na₅[{Fe(H₂O)₃}₂{Fe(H₂O)₄}_0.5(H₂W₁₂O₄₂)]·30H₂O ( 2 ) and (H₃O)⁺₂[{Fe(H₂O)₄Fe(H₂O)₃}₂(H₂W₁₂O₄₂)]·20H₂O ( 3 ). 1 and 3 crystallize in the monoclinic system, space group P2₁/n with a = 14.9967(5), b = 10.3872(3), c = 18.8237(6)Å, β = 93.407(1)°, V = 2927.1(2)ų and D_c = 4.151 g cm^—3 for 1 , and space group P2₁/c with a = 12.1794(4), b = 22.4938(4), c = 11.6941(3) Å, β = 105.731(2)°, V = 3083.7(1) ų, and D_c = 4.043 g cm^—3 for 3 . 2 is triclinic, space group P1¯, with a = 12.121(2), b = 12.426(3), c = 13.247(3)Å, α = 68.33(3), β = 71.33(3), γ = 71.44(3)°, V = 1710.7(6)ų and D_c = 3.735 g cm^—3. In all cases, the structures are based on paradodecatungstate polyoxoanions, which are linked by iron ions into chains, layers and a three‐dimensional structure for 1 , 2 and 3 , respectively.     

Structures of Concentrated Sulfuric Acid Determined from Density, Conductivity, Viscosity, and Raman Spectroscopic Data

Addition of water to stoichiometric 100% sulfuric acid increases the density untila maximum results near 87 mole% H₂SO₄. The density and conductivity maximaand viscosity minimum, the latter two near 75 mole%, are direct macroscopicresponses to microscopic quantum mechanical properties of H₃O⁺ and of nearlysymmetric H-bond double-well potentials, as follows: (1) lack of H bonding tothe O atom of H₃O⁺; (2) short, 2.4–2.6 A, O—O distances of nearly symmetricH bonds; and, (3) increased mobility of protons in such short H bonds, give riseto the density maximum via (1) and (2); (1) produces the viscosity minimum;and the conductivity maximum results from (2) and (3). A pronounced minimumnear 1030 cm^–1 in the symmetric SO₃ stretching Raman frequency of HSO₄ ^–,observed near 45 mole% also results from double-well effects involving the shortH bonds of direct hydronium ion—bisulfate ion pair interactions. Estimates of theconcentrations of the (H₃O⁺)(HSO₄ ^–) and (H₂SO₄)(HSO₄ ^–) pair interactions weredetermined from Raman intensity data and are given for compositions between42–100 mole%     

Carbon dioxide and methane adsorption at high pressure on activated carbon materials

Granular and monolith carbon materials were prepared from African palm shell by chemical activation with H₃PO₄, ZnCl₂ and CaCl₂ aqueous solutions of different concentrations. Adsorption capacity of carbon dioxide and methane were measured at 298 K and 4,500 kPa, and also of CO₂ at 273 K and 100 kPa, in a volumetric adsorption equipment. Correlations between the textural properties of the materials and the adsorption capacity for both gases were obtained from the experimental data. The results obtained show that the adsorption capacity of CO₂ and CH₄ increases with surface area, total pore volume and micropore volume of the activated carbons. Maximum adsorption values were: 5.77 mmol CO₂ g^?1 at 273 K and 100 kPa, and 17.44 mmol CO₂ g^?1 and 7.61 mmol CH₄ g^?1 both at 298 K and 4,500 kPa.     

Stable isomers for trifluoroacetic acid (TFA) pentahydrates obtained from density functional calculations

Stable isomers of trifluoroacetic acid (TFA) pentahydrate clusters, TFA-(H₂O)₅, have been explored by using density functional theory calculations. As done for TFA-(H₂O)₄ (Ito, 2013), structure optimization and vibrational calculations were performed for 70 isomeric structures (68 for neutral and 2 for ion-pair species, respectively) at the B971/6–311++G(3df,3pd) level. We found that the edge-sharing bicyclic isomer is at the global minimum and that three other isomers lie energetically within 100 cm⁻¹. Two types of ion-pair species were found to be unstable by 1100 cm⁻¹ in comparison with the global minimum. The results were compared with infrared spectra observed in nitrogen matrix.     

Die Kristallstruktur des SrHg(SCN)4 · 3 H2O

Crystal Structure of SrHg(SCN)₄ · 3 H₂O SrHg(SCN)₄ · 3 H₂O is orthorhombic, space group Pcca, with a = 19.476(7), b = 8.150(1), c = 8.991(3) Å, V = 1427.1 ų, Z = 4, d_c = 2.67 g · cm^?3, μ(AgKα) = 77.95 cm^?1. The salt consists of nearly tetrahedral Hg(SCN)₄ groups, Sr has a tricapped trigonal prismatic coordination: four N and five O atoms. The thiocyanate groups form end-to-end bridges and connect the Hg and Sr coordination polyhedra.     

Alkaline–Acid Zn–H2O Fuel Cell for the Simultaneous Generation of Hydrogen and Electricity

An alkaline–acid Zn–H₂O fuel cell is proposed for the simultaneous generation of electricity with an open circuit voltage of about 1.25 V and production of H₂ with almost 100 % Faradic efficiency. We demonstrate that, as a result of harvesting energy from both electrochemical neutralization and electrochemical Zn oxidation, the as‐developed hybrid cell can deliver a power density of up to 80 mW cm^?2 and an energy density of 934 Wh kg^?1 and maintain long‐term stability for H₂ production with an output voltage of 1.16 V at a current density of 10 mA cm^?2.