Solid-phase Synthesis Method Research Articles

A strategy for the preparation of super-hydrophilic molybdenum disulfide composites applied to remove uranium from wastewater.

Due to the radioactivity of uranium, the discharged nuclear wastewater not only causes certain damage to the ecology, but also causes certain harm to human life and health. Adsorption is considered to be one of the most effective ways to remove uranium. In this paper, a kind of MoS2 adsorbent was prepared by the solid phase synthesis method and functionalized with NiCo-LDH. The raw materials of MoS2 are cheap and easy to obtain, and the preparation conditions are simple, and large quantities can be obtained without limitations. MoS2 functionalized with NiCo-LDH provides more adsorption sites for the adsorbent and at the same time improves the hydrophilicity of the adsorbent, so that the active sites can fully combine with uranyl ions. The maximum adsorption capacity of the Langmuir isothermal adsorption model is 492.83 mg g-1. The selective adsorption capacity of uranium can reach 76.12% in the multi-ion coexistence system. By analyzing the adsorption mechanism with FT-IR and XRD, it is believed that on the one hand, UO22+ forms a covalent bond with Mo in MoS2 and coordinates with S on the surface of MoS2. On the other hand, UO22+ enters the NiCo-LDH layer for ion exchange with NO3- and coordinates with -OH on the surface of NiCo-LDH. The successful preparation of the MoS2/NiCo-LDH composite provides a certain application prospect for the uranium adsorption field.

Efficient automated solid-phase synthesis of recognition-encoded melamine oligomers.

Recognition-encoded melamine oligomers (REMO) are synthetic polymers with an alternating 1,3,5-triazine-piperazine backbone and side chains equipped with either a phenol or phosphine oxide recognition unit. Here, we describe an automated method for highly efficient solid-phase synthesis (SPS) of REMO of any specified length and sequence. These SPS protocols are amongst the most robust reported to date, as demonstrated by the synthesis of a mixed-sequence 42-mer, which was obtained in excellent crude purity on a 100 mg scale. Starting from loaded Wang resin and dichlorotriazine monomer building blocks, the SPS methods were automated and optimised on a commercial peptide synthesiser. Major side products were identified using LCMS, and the undesired side reactions were suppressed by the choice of resin, solvent and coupling conditions. REMO have been shown to form high-fidelity length- and sequence-selective H-bonded duplexes, analogous to nucleic acids, and automated synthesis will facilitate exploration of related functional properties, such as molecular replication and programmable self-assembly.

The synthesis and supercapacitor application of flexible free-standing Ti3C2Tx, Mo2TiC2Tx, and V4C3Tx MXene films.

MXenes represent a fascinating category of two-dimensional materials made up of transition metal carbides and nitrides, currently attracting significant research attention, especially in energy storage. However, the electrochemical properties of MXene materials with varying elemental compositions may exhibit significant differences. In order to optimally select types of MXenes that are more suitable for energy storage and explore their energy storage mechanisms, three kinds of different elemental compositions of delaminated MXenes (d-Ti3C2Tx, d-Mo2TiC2Tx, and d-V4C3Tx) were prepared by solid-phase synthesis, liquid-phase etching, and mechanical exfoliation method, successively. The obtained single-layer or few-layer MXene nanosheets were self-assembled into flexible free-standing film electrodes via vacuum-assisted filtration, and the detailed material preparation and characterization can guide the synthesis of more MXenes. Furthermore, we conducted a comprehensive study on the effects of various aqueous electrolytes (3 M H2SO4, 3 M KOH, and 3 M Na2SO4) and temperatures (0 °C, 20 °C, and 40 °C) on their electrochemical performance. This work optimized the MXene types that are more suitable for electrochemical energy storage application (d-Ti3C2Tx and d-V4C3Tx), and also found that the V4C3Tx MXene has excellent rate performance and long cycling performance, and has guiding significance for the development of MXene materials in energy storage. More significantly, the d-V4C3Tx MXene exhibits exceptional specific capacitance in both acidic and alkaline electrolytes, reaching 292.0 F g-1 in 3 M H2SO4, the highest among the three types of MXenes, and 184.3 F g-1 in 3 M KOH, far surpassing the performance of the d-Mo2TiC2Tx and d-Ti3C2Tx MXenes (less than 100 F g-1 at 2 mV s-1). Furthermore, this reveals that H+ intercalation/deintercalation, showing pseudocapacitance characteristics, along with the large interlayer spacing play a vital role in energy storage for MXenes, and an asymmetric configuration is an effective means to improve the energy density of aqueous supercapacitors. The comparative analysis aims to enhance the understanding of MXene materials' potential in advanced energy storage systems.

Effect of Ti-containing precursors on structure and adsorption performance of Li4Ti5O12 and Li2TiO3 oxides to Li+ ions

Using solid-phase synthesis method, Li4Ti5O12 and Li2TiO3 oxides were synthesized and used as adsorbents for Li+ ions. The physical–chemical properties were studied, using X-ray diffraction analysis, IR-spectroscopy, low-temperature adsorption–desorption of nitrogen, and scanning electron microscopy. It was shown that, using anatase as a Ti-containing precursor, single-phase oxides Li4Ti5O12 (d 26.5 nm, a 8.401 Å, V 569.5 Å3) and Li2TiO3 (d 26.5 nm, a 7.731 Å, V 462.1 Å3) with macro-mesoporous structure (ABET 11 and 16 m2/g, VBJH des 0.03 and 0.03 cm3/g, DBJH des 6 and 6 nm, respectively) and spherical-like morphology were obtained. For the samples obtained from rutile, an impurity of unreacted Ti-containing precursor was detected. The effect of the nature of Ti-containing precursors, concentration and temperature of HCl regeneration solution, and contact time on the degree of conversion to H-form and adsorption capacity of the obtained adsorbents was studied. The highest efficiency of ion exchange of Li+ ions with H+ (γH+ 96.7–100 %) was reached in conversion of adsorbents to H-form, during treatment with 0.1 M HCl at temperature of 70 °C for 48 h. Adsorbents H4Ti5O12 and H2TiO3 prepared from anatase showed higher adsorption efficiency of Li+ ions (qe 95.1 and 84.0 mg/g, α 34.7 and 32.9 %, respectively) compared to samples obtained from rutile (qe 75.7 and 81.2 mg/g, α 23.8 and 29.9 %, respectively). After three cycles of acid regeneration, the adsorption capacity was maintained at 40.6–47.0 mg/g for Li4Ti5O12, and at 34.8–38.4 mg/g for Li2TiO3, respectively. The hydrogen demonstration during adsorption–desorption cycles increased from 8.4 to 10.8 for Li4Ti5O12, and from 8.0 to 11.2 for Li2TiO3. Anatase Ti-containing precursor recrystallization into rutile modification and further amorphization was determined. The presented results are interesting for developing highly efficient adsorbents for Li+ ions recovery from aqueous solutions.

Solid-Phase Synthesis of Caged Luminescent Peptides via Side Chain Anchoring.

The synthesis of caged luminescent peptide substrates remains challenging, especially when libraries of the substrates are required. Most currently available synthetic methods rely on a solution-phase approach, which is less suited for parallel synthesis purposes. We herein present a solid-phase peptide synthesis (SPPS) method for the synthesis of caged aminoluciferin peptides via side chain anchoring of the P1 residue. After the synthesis of a preliminary test library consisting of 40 compounds, the synthetic method was validated and optimized for up to >100 g of resin. Subsequently, two separate larger peptide libraries were synthesized either having a P1 = lysine or arginine residue containing in total 719 novel peptide substrates. The use of a more stable caged nitrile precursor instead of caged aminoluciferin rendered our parallel synthetic approach completely suitable for SPPS and serine protease profiling was demonstrated using late-stage aminoluciferin generation.

The effect of high temperature aging on fluorescence properties of Eu3+-doped La2(Zr0.7Ce0.3)2O7

Introduction of luminescent rare earth ions into thermal barrier coatings (TBCs) for the study of TBCs failure mechanism is a very effective non-destructive method. In this paper, Eu3+ ions were doped into La2(Zr0.7Ce0.3)2O7 (LZ7C3) to form LZ7C3:Eu fluorescent material using a high-temperature solid-phase synthesis method. By analyzing the physical structure, fluorescence properties and thermophysical properties of LZ7C3:Eu powders synthesized with different Eu3+ dopant concentrations at different temperatures, we determined that a synthesis temperature of 1400 °C, a dopant concentration of 1 mol% are the optimal synthesis conditions for LZ7C3:Eu. Independent LZ7C3:Eu coating was prepared by atmospheric plasma spraying technology, and high temperature aging test was carried out at 1400 °C. The influence of high temperature aging on the 5D0→7F2 energy level transition peak of Eu3+ in LZ7C3 powder and its coating was examined by microscopic emission spectroscopy. The results show that the peak of the 5D0→7F2 energy level transition is red-shifted, and the peak intensity and the full width at half maxima (FWHM) of the powder decrease gradually with the increase of high temperature aging time. The peak of the 5D0→7F2 energy level transition of the coating exhibits a constantly fluctuating tendency of red-shifting and then blue-shifting, and the peak intensity and the FWHM also continue to decrease. High temperature aging has a negative effect on the fluorescence properties of LZ7C3:Eu materials.

Developing a solid-phase method for the enzymatic synthesis of heparan sulfate and chondroitin sulfate backbones.

Despite the recent progress on the solution-phase enzymatic synthesis of heparan sulfate (HS) and chondroitin sulfate (CS), solid-phase enzymatic synthesis has not been fully investigated. Here, we describe the solid-phase enzymatic synthesis of HS and CS backbone oligosaccharides using specialized linkers. We demonstrate the use of immobilized HS linker to synthesize CS, and the use of immobilized CS linker to synthesize HS. The linkers were then digested with chondroitin ABCase and heparin lyases, respectively, to obtain the products. Our findings uncover a potential approach for accelerating the synthesis of structurally homogeneous HS and CS oligosaccharides.

Protocol for Facile Synthesis of Fmoc-N-Me-AA-OH Using 2-CTC Resin as Temporary and Reusable Protecting Group.

One approach to enhance the bioavailability and half-life of peptides in vivo is through N-methylation of one or more of the amino acids within the peptide sequence. However, commercially available Fmoc-N-Me-AA-OHs are limited and often expensive. In this study, a solid-phase synthesis method for Fmoc-N-Me-AA-OH was developed using a 2-chlorotrityl chloride (2-CTC) resin as a temporary protective group for the carboxylic acid strategy. Two strategies for the alkylation step were compared, employing either dimethyl sulfate or methyl iodide in the Biron-Kessler method. In this work we tested the protocol with two amino acids: Fmoc-Thr(tBu)-OH and Fmoc-βAla-OH. The first one is an alpha amino acid, very hindered and with the amine group directly influenced by the electronic effects of the carboxy group, whereas in Fmoc-βAla-OH, the presence of a methylene group weakens this influence due to the intervening carbon atoms. The desired amino acids, Fmoc-N-Me-Thr(tBu)-OH and Fmoc-N-Me-βAla-OH, were synthesized by both strategies with high yield and purity.

Tailoring magnetic properties of SrFe12O19 ferrites through Dy–Ni Co-substitution: A comprehensive study

A solid-phase synthesis method was utilized to create a range of ferrite samples, specifically Sr1-xDyxFe12-xNixO19, where x values varied (0, 0.01, 0.02, 0.03, and 0.05). Through X-ray diffraction (XRD) analysis, it was found that up to x ≤ 0.03, the XRD pattern showed no discernible impurity phases. However, at x = 0.05, an observable impurity peak attributed to α-Fe2O3 emerged. Room temperature hysteresis loop measurements revealed consistent hard magnetic behavior across all samples. Notably, changes in coercive force directly correlated with magnetocrystalline anisotropy. As substitution increased, the initial saturation magnetization (MS) of 59.68 emu/g (at x = 0.00) moderately reduced to 57.79 emu/g (at x = 0.05), representing a modest decline of 3.17 %. A clear trend was observed: decreasing grain size led to diminishing dielectric constants. Moreover, a strong link between the Nyquist diagram's semicircle diameter and sample resistivity was evident, showing distinctive metal-semiconductor behavior. These findings shed light on the structural and magnetic characteristics of Dy and Ni co-substituted SrFe12O19 ferrites, suggesting potential for enhanced performance in advanced magnetic and electronic devices. This study significantly contributes to the field of ferrite materials, deepening our insights and paving the way for innovative applications in diverse technological domains.

Mechanochemical Oxidative Coupling of Amine to Azo-based Polymers by Hypervalent Iodine Oxidant.

Among porous organic polymers (POPs), azo-linked POPs represent a crucial class of materials, making them the focus of numerous catalytic systems proposed for their synthesis. However, the synthetic process is limited to metal-catalyzed, high-temperature, and liquid-phase reactions. In this study, we employ mechanochemical oxidative metal-free systems to encompass various syntheses of azo-based polymers. Drawing inspiration from the "rule of six" principle (six or more carbons on an azide group render the organic compound relatively safe), an azo compound featuring significant steric hindrance is obtained using the hypervalent iodine oxidation strategy. Furthermore, during the polymerization process, steric hindrance is enhanced in monomers to effectively prevent explosions resulting from direct contact between hypervalent iodine oxidants and primary amines. Indeed, this approach provides a facile and innovative solid-phase synthesis method for synthesizing azo-based materials.

Study of the Effect of Adding Nb2O5 on Calcium Titanate-Based Ferroelectric Ceramics

This paper considers the effect of adding niobium oxide (Nb2O5) to ferroelectric ceramics based on calcium titanate (CaTiO3), and establishes a connection between the observed alterations in strength and dielectric properties and the variation in the Nb2O5 dopant concentration in the ceramics’ composition. The method of mechanochemical solid-phase synthesis was used as the main method for obtaining the ceramics, followed by thermal sintering under specified conditions in order to form a stable phase composition of the ceramics, and to initialize phase transformations in the composition. Based on the assessment of the phase composition of the resulting ceramics, it was determined that a growth in the Nb2O5 dopant concentration beyond 0.10 mol results in the formation of an orthorhombic-phase CaNb2O4 of the Pbcm(57) spatial system, the weight contribution of which grows. A growth in the Nb2O5 additive concentration results in the formation of two-phase ceramics, the formation of which allows for an enhancement in the mechanical strength of ceramics and resistance to external influences. During the study of the dependence of the strength properties on the dopant concentration alteration, a three-stage change in hardness and crack resistance was established, regarding both structural ordering and phase transformations. The measurement of dielectric characteristics showed the direct dependence of dielectric losses and the dielectric constant on the phase composition of ceramics.

In Ukrainian

Double phosphates compounds may possess catalytic, magnetic, electrophysical, non-linear optical properties and are used as monocrystals or polycrystals, ceramics etc. The tailor-made synthesis of double phosphates of alkali and multivalent metals is the basis for the in-depth research and investigation of physical and chemical properties, composition and structure of the compounds to be used for the development of new materials for multi-purpose use. Episodic syntheses of compounds MI3MIІMIV(PO4)3, MI2MIIMIV(P2O7)2, MI2MII(PO3)4 and МІMІІ4(РО4)33 (where МI – Li, Na, K; МIІ – Mn, Co, Ni; MIV – Zr), were made from various starting materials by the sintering method. After all, the selection of compounds for the synthesis of compounds of this type is a rather difficult task, often impossible. A systematic approach to the selection of starting reagents, temperature regime, interaction time between components are factors that can be adjusted and operated to achieve the target. The work used the method of solid-phase synthesis, after working out the synthesis method on the “model” Na2NiZr(P2O7)2. The synthesis was carried out starting from Na2CO3, NiO, CoO, ZrO2, ammonium hydro- and dihydrogen phosphate. The synthesis of compounds was carried out based on preliminary derivatographic studies of the passage of processes according to the corresponding reaction schemes. Completeness of synthesis stages was monitored at all stages using physico-chemical research methods. The DTA method confirmed the possibility of solid-phase synthesis of complex phosphate compounds that contain several transition metals – MINi2MIV(PO4)3 (where МI – Li, Na, K; MIV – Ti, Zr, Sn). The optimal temperature conditions for obtaining a number of phosphate compounds based on various starting substances for their synthesis have been found. The synthesized compounds were investigated by X-ray diffraction, DTA and IR spectroscopy, and their complete chemical analysis was carried out. The influence of a number of factors on the conditions of production of phosphate compounds of the MINi2MIV(PO4)3 (where МI – Li, Na, K; MIV – Ti, Zr, Sn) has been found. It can be assumed that the ionic conductivity in the synthesized compounds is of the “NASICON” type, and therefore the synthesized substances can be used as functional materials with valuable electro-physical properties.

Low sintering temperature and microwave dielectric properties of H3BO3-added Li2Ti0.85(A1/3Ta2/3)0.15O3 (A = Zn, Mg) ceramics for patch antenna application

Li2Ti0.85(A1/3Ta2/3)0.15O3 + xwt.% H3BO3 (A = Zn, Mg; 1.0 ≤ x ≤ 5.0) (LTATBx) ceramics were fabricated by the traditional solid phase synthesis method. The LTATBx ceramics belong to monoclinic structure which was checked by the X-ray diffraction (XRD). The microstructure of Li2Ti0.85(A1/3Ta2/3)0.15O3 ceramics could be improved by the addition of H3BO3, which was directly observed by the scanning electron microscope (SEM). The optimum dielectric properties (107,490 GHz and 57,543 GHz) of Li2Ti0.85(A1/3Ta2/3)0.15O3 ceramics were obtained when the x values are equal to 1.0 and 3.0, respectively. Since the addition amount reached 5.0, the sintering temperature declined to 900 °C and 950 °C, respectively. The patch antennas prepared with LTZTB1.0 and LTMTB3.0 ceramics were simulated and measured. The results from measured indicated that the S11 parameters in LTZTB1.0 and LTMTB3.0 based patch antenna are less than −15.0 dB, and the VSWR is close to 1.0, which basically meets the application requirements of external antenna.

Ultrastable bifunctional multi-stage active metal catalysts for low concentration CO2 capture and in-situ conversion

Integrating CO2 capture and in-situ conversion is a promising means of processing low concentration CO2 in flue gas. The development of a low cost, highly stable catalyst to reduce the running cost is key to the development of this technology. The ultrastable bifunctional multi-stage active metal catalysts (Ca12Al14O33-y (Ca2Fe2O5)-CoxCaO) were synthesized by the solid phase synthesis method with low cost industrial powder raw materials. The catalyst was stabilized with calcium aluminate (Ca12Al14O33) and calcium ferrite (Ca2Fe2O5) as a substrate structural framework for CaO and enhanced the dispersion of CaO. It not only solved the problem of CaO deactivation due to sintering, pore collapse, and agglomeration in the continuous high-temperature reaction, but also showed excellent catalytic performance for reverse-water–gas-shift (RWGS) reaction. On the basis of calcium-looping and RWGS reaction, the high temperature CO2 capture and in-situ conversion process is realized in the same fixed-bed reactor for processing simulated flue gas with 16.7 vol% CO2. The results showed that at the optimum operating temperature of 610 °C, the catalyst still maintains a stable CO2 capture capacity, over 98% CO2 conversion rate and close to 100% CO selectivity after 100 cycles. The multi-stage active metal structure catalysts provided a unique construction idea for designing ultrastable catalysts for low concentration CO2 capture and in-situ conversion with great potential for industrial application.

Facile in-suit solid-phase synthesis of carbon-coated Ni2P nanospheres decorated on carbon nanotubes with high performance in both supercapacitors and lithium-ion batteries

Low specific surface area and severe agglomeration are the main defects of the energy storage materials (ESMs) fabricated by the solid-phase synthesis (SPS) method. If these defects could be well addressed, the SPS method would be a promising method for the fabrication of high-performance ESMs with the merits of convenience, eco-friendliness, and cost-effectiveness. In this work, an in-suit solid-phase synthesis method is developed for the synthesis of the Ni2[email protected]/CNT nanocomposite with high performance in both supercapacitor and lithium-ion battery. The carbon-coated Ni2P nanospheres are in-suit synthesized and decorated successfully on the porous high-conductive CNTs framework by the proposed method. An ultra-high specific capacity of 378.5 mAh g−1 at 1 A g−1 and a good rate capacity (189.3 mAh g−1 at 20 A g−1) are presented by the synthesized nanocomposite. Meanwhile, high performance is achieved in both supercapacitor and lithium-ion battery application. Compared to the transition metal phosphide-based nanocomposites reported in literature prepared by the traditional methods, the Ni2[email protected]/CNT nanocomposite prepared by the proposed in-suit SPS method exhibits very competitive performance in both supercapacitor and lithium-ion battery. The proposed in-suit SPS method is proved to be a promising method for the preparation of high-performance ESMs.

Microwave-Assisted Solid Phase Synthesis of Different Peptide Bonds: Recent Advancements

Abstract: Peptides are important as drugs and biologically active molecules. The synthesis of pep-tides has gathered considerable attention in recent years due to their various attractive properties. Conventional peptide synthesis is tedious and requires hazardous reagents and solvents. Micro-wave-assisted solid-phase peptide synthesis has several advantages compared with conventional batch synthesis. Herein, we have discussed various microwave-assisted solid-phase peptide bond synthesis methods developed over the last five years. Peptides are categorized into four groups - small, medium, large, and cyclic based on their length and structural characteristics to make it easier to understand. This review article also discusses the scope and limitations of microwave-assisted solid-phase peptide synthesis.

Abstract P320: Novel Alpha-calcitonin Gene Related Peptide Agonist Analogs In The Treatment Of Cardiovascular Disease

Alpha-calcitonin gene related peptide (α-CGRP) is a potent vasodilator and protects against heart failure and hypertension in various animal models; however, rapid clearance of the peptide from the circulation makes it difficult to use as a therapeutic agent. Recently, we have synthesized two α-CGRP agonist analogs linked with two n-methoxyethylglycine (NMEG) peptoid molecules at either end: 1)- α-CGRP with NMEG molecules at the N-terminal end (N-ter NMEG), and 2)- α-CGRP with NMEG molecules at the C-terminal end (C-ter NMEG). Bioactivity and toxicity of modified peptides were evaluated in in vitro and in vivo conditions. Peptide-peptoid hybrids, N-ter NMEG and C-ter NMEG, were synthesized using a solid-phase peptide synthesis method with a >98% purity. To test the in vitro cell viability of the analogs, rat H9C2 cardiac myocyte cells were treated with 1 μM, 3 μM, and 10 μM concentrations of N-ter NMEG and C-ter NMEG peptides for 4 days followed by an MTT assay. Our in vitro results demonstrated that neither α-CGRP analogs were toxic to H9C2 cells. To test the bioactivity of these peptides, blood pressure (BP) was measured in wild-type C57BL6 mice using a tail-cuff BP analysis system. A bolus dose of 1.2, 3.6, and 12 (in mg/kg b.wt./mouse) of either peptide was injected subcutaneously (n= 4 mice/dose) followed by BP measurement at increasing time points. Our results demonstrate that there is a variance in the bioactivity of the two peptides. Subcutaneous delivery of N-ter NMEG reduced BP similar to the native peptide. After ten minutes of N-ter NMEG delivery, the BP (in mmHg ±SD) at a dose of 1.2 mg/kg was 76 ±5 (baseline BP= 118 ±15), at a dose of 3.6 mg/kg was 79 ±7 (baseline BP= 113 ±9), and at a dose of 12 mg/mg was 83 ±12 (baseline BP= 104 ±6). In contrast, C-ter NMEG administration did not reduce BP at any peptide concentration tested. In summary, in this study we determined that the α-CGRP analog N-ter NMEG, but not C-ter NMEG, is bioactive. Furthermore, N-ter NMEG showed no toxic effects on H9C2 cardiac myocytes in an in vitro viability assay. These results demonstrate that the analog N-ter NMEG is an effective α-CGRP agonist and a promising candidate molecule to treat cardiac diseases.

A novel high activity MnXFe3−XO4 spinel catalyst for selective catalytic reduction of NO using NH3 prepared by a short process from natural minerals for low-temperature sintering flue gas: Effect of X value on catalytic mechanism

The process of smelting and purifying the catalyst precursor salt from minerals is extremely complex, which directly leads to high catalyst costs and serious secondary pollution. In order to achieve energy saving and emission reduction in the catalyst preparation process, in-situ synthesis of catalyst materials from natural minerals is a new research direction. In this study, we firstly explored the optimal X value of MnXFe3-XO4 for the NH3 selective catalytic reduction of NO (NH3-SCR) reaction, i.e., the Mn, Fe ratio, and then prepared a novel highly active mineral-based pure phase MnXFe3-XO4 spinel NH3-SCR catalyst by natural ferromanganese ore fines with iron-red fines (Fe2O3) allotment through in situ solid-phase synthesis and magnetic separation methods according to this ratio. The results show that the X value of 1.5 (Mn1.5Fe1.5O4) is the best for NH3-SCR reaction. Mn1.5Fe1.5O4 nano-particles (201 nm) has nearly 100 % NO conversion (with 5 % H2O(g)) at 125–300 °C. The combination of characterizations and density functional theory (DFT) calculation shows that the catalytic process of Eley-Rideal (E-R) dehydrogenation is enhanced at both the active site Mn site and Fe site, which is a key factor in the acceleration of the NH3-SCR reaction with increasing X value at the MnXFe3-XO4 surface.

Features of the Phase Formation of Cr/Mn/Fe/Co/Ni/Cu Codoped Bismuth Niobate Pyrochlore

The phase formation process of Bi2Cr1/6Mn1/6Fe1/6Co1/6Ni1/6Cu1/6Nb2O9+Δ containing 3d-ions of transition elements in equimolar quantities was studied in a wide temperature range (400–1050 °C). The complex oxide crystallizes in the structural type of pyrochlore (sp. gr. Fd-3m:2, a = 10.4937(2) Å). The investigation of the multi-element pyrochlore phase formation process showed that the synthesis goes through a series of successive stages, during which the transition from Bi-rich to Bi-depleted compounds takes place. The predecessor of the pyrochlore phase is bismuth orthorhombic modification orthoniobate (α-BiNbO4) with an equimolar ratio of Bi(III)/Nb(V) ions. The pyrochlore phase is formed as a result of bismuth orthoniobate doping with transition element ions. The complex oxides Bi14CrO24, Bi25FeO40, BiNbO4, and Bi5Nb3O15 appeared as intermediate phases during the synthesis. The interaction between the initial oxide precursors is fixed at temperatures above 500 °C. The phase transition of α-Bi2O3 into β-Bi2O3 near 500 °C is observed. Varying the heat treatment duration at each synthesis step did not qualitatively change the phase composition of the sample but had an effect on the quantitative phase ratio. Phase-pure pyrochlore of the given composition by solid-phase synthesis method can be obtained at a temperature no lower than 1050 °C. Ceramics are characterized by low-porous dense microstructure with blurred outlines of grain boundaries.

Thermodynamic and High-Temperature Properties of KFe0.33W1.67O6

This paper presents the results of a study of the KFe0.33W1.67O6 system. The compound was obtained by a solid-phase synthesis method at a temperature of 1073 K. The structural, morphological, and spectroscopic properties of KFe0.33W1.67O6 were characterized using XRD, SEM-EDS. The compound crystallizes in a cubic lattice with the space group Fd–3m (227). The obtained lattice parameter a = 10.3697 (3) Å. The phase transitions of KFe0.33W1.67O6 were determined by low-temperature and high-temperature X-ray diffraction. The temperature dependence of heat capacity of KFe0.33W1.67O6 has been measured for the first time in the range from 5 to 638 K by precision adiabatic vacuum calorimetry and differential scanning calorimetry. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity C∘p∘(T), enthalpy H°(T) − H°(0), entropy S°(T) − S°(0), and Gibbs function G°(T) − H°(0), for the range from T → 0 to 630 K.