In this work, the effect of using an additive of dawsonite NH4Al(OH)2CO3 or scarbroite Al5(OH)13(CO3)·5H2O in the preparation of alumina supports on the properties of CoMo/Al2O3 catalysts was investigated. It was established that the key factor influencing the composition and properties of the active component of the catalyst was the phase composition of the support, which changed depending on the added dawsonite and/or scarbroite powder. According to XRD and UV spectroscopy data, it was found that with the addition of dawsonite, the amorphous phase predominated in the support, which altered the nature of the interaction of the support and the active metals, namely, it reduced the amount of inactive cobalt aluminate compared to the catalyst sample based on the support with scarbroite. Furthermore, the change in the phase composition of the support affected the formation of the active component. For the sample prepared with dawsonite, XPS data showed the formation of more reactive sulfide sites. The addition of dawsonite led to the formation of a looser support surface, which increased the dispersion of the active component particles from 0.35 to 0.58 compared to the catalyst sample based on the support with scarbroite. The described changes in the characteristics of the catalyst with dawsonite led to an increase in catalyst activity, both in the hydrodesulfurization reactions of model feedstock and of real blended gasoil.

The study focuses on the effect of 1-70 wt % silica gel addition on the properties of CoMo/Al2O3 catalyst for fluid catalytic cracking gasoline hydrotreating. An increase in silica gel content results in an increase in the specific surface area and pore volume in the supports and catalysts. According to the IR spectroscopy of adsorbed CO and pyridine, the addition of any amounts of silica gel leads to the decrease in LAS concentration, while 30 wt % of silica gel leads to the formation of BAS typical for amorphous aluminosilicate. According to UV-vis spectroscopy and TPR-H-2, the dispersity of oxygen-containing compounds of active metals decreases when silica gel is added. The addition of 5-70 wt % of silica gel results in an increase in the average particle length of the active component from 2.1 to 2.2-2.7 nm and the stacking number from 1.8 to 1.9-2.2. Moreover, there is a correlation between Mo4+ content and catalyst's HDS activity. The catalyst with 30 wt % of silica gel had the highest Mo4+ content and the highest HDS activity. The formation of BAS in the catalysts with 30-70 wt % of silica gel leads to improved activity in isomerization of alkanes and alkenes, aromatization (or cyclization) of alkanes and alkenes, and alkylation of aromatics, and increased octane number of products from 89 to 92-93 points.

In order to manage the environment and perform noninvasive disease diagnostics, it is necessary to continuously identify harmful and highly toxic gases, such as nitrogen dioxide (NO2). This study demonstrates how to design nanocomposites and build a cost-effective NO2 gas sensor based on exfoliated tungsten disulphide and functionalized multiwalled carbon nanotubes (f-MWCNTs) as a highly efficient sensing material operating at room temperature (RT) in humid conditions. The composite sensor's response under various humidity levels, ranging from 2% to 65%, as well as at different temperatures ( 25 C-degrees- 80( degrees)C), was studied. Scanning electron microscopy (SEM), Raman spectroscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX) were used to analyze the sensing material. The composite-based sensor showed an improved response Delta R/R0 of 52% at RT for 50-ppm NO2 with good selectivity to other gases (e.g., ammonia, methane, benzene, isobutene, and hydrogen). The composite sensor exhibited a low detection limit of 1.39 ppm for NO2 at RT. Furthering this advancement, we delve into the integration of machine learning, specifically the CatBoost regression model, with the NO(2 )sensor. This integration elevates the sensor from a conventional passive detector to an advanced analytical system, significantly boosting its predictive accuracy and adaptability for real-time environmental monitoring and nuanced data interpretation, thereby opening new frontiers in sensor technology and applications in environmental monitoring and health diagnostics.

This paper is focused on the solution combustion synthesis (SCS) of a set of 90Ni/10Al2O3 2 O 3 (wt. %) catalysts for the production of hydrogen and carbon nanofibers through methane decomposition. A novel approach was employed to optimize the SCS of the catalysts in order to enhance the yields of hydrogen. The obtained catalysts were tested in methane decomposition at 550 degrees C and 1 bar. Transmission electron microscopy, energy-dispersive X-ray spectroscopy, low temperature nitrogen adsorption, and X-ray diffraction were utilized to investigate the catalysts. The SCS process involved programmable heating of a mixture of Ni(NO3)2 & sdot;6H2O 3 ) 2 & sdot; 6H 2 O and Al(NO3)3 & sdot;9H2O 3 ) 3 & sdot; 9H 2 O with citric acid (C6H8O7) 6 H 8 O 7 ) from room temperature to 350-450 degrees C at a heating rates 1-10 degrees C/min and exposure durations of 0-20 min. It was discovered that a high specific yield of hydrogen (17.1 mol/gcat.) cat. ) and carbon nanofibers (171 g/gcat.) cat. ) can be achieved by synthesizing at 450 degrees C using a heating rate of 1 degrees C/min without additional exposure.

Highly dispersed LaCo1-x-yCuxTiyO3/KIT-6 perovskites were synthesized by the citrate method with inert mesoporous KIT-6 addition. The KIT-6 matrix was removed by dissolution in 7% NaOH aqueous solution. The dispersity of perovskites probably varies depending on the largest cation and its content at the B position of the perovskite ABO3 structure. The CoS=23+/CoS=03+ ratio increases with the increase in copper content and in the presence of Ti4+. It may be explained by the compensation of the distortion of the perovskite structure. The maximum syngas conversion is achieved at nCo/nCu = 7/3. At a higher copper content, the activity of the samples decreases due to the formation of large copper particles (up to 40 nm) in the course of the reduction. The selectivity for alcohols increases with an increase in the proportion of copper and reaches maximum values at a ratio of nCo/nCu close to 1. The distribution of alcohols is the same for all samples, except for LaCo0.35Cu0.35Ti0.3O3/KIT-6. It can be assumed that the synthesis of alcohols proceeds on bimetallic CoCu particles 3 nm in size and cobalt particles 4-6 nm in size, most likely enriched with copper on the surface.

In this paper, room-temperature chemiresistive gas sensors for NO2 detection based on CVD-grown carbon nanofibers (CNFs) were investigated. Transmission electron microscopy, low-temperature nitrogen adsorption, and X-ray diffraction were used to investigate the carbon nanomaterials. CNFs were synthesized in a wide range of pressure (1–5 bar) by COx-free decomposition of methane over the Ni/Al2O3 catalyst. It was found that the increase in pressure during the synthesis of CNFs induced the later deactivation of the catalyst, and the yield of CNFs decreased when increasing pressure. Sensing properties were determined in a dynamic flow-through installation at NO2 concentrations ranging from 1 to 400 ppm. Ammonia detection was tested for comparison in a range of 100–500 ppm. The obtained sensors based on CNFs synthesized at 1 bar showed high responses of 1.7%, 5.0%, and 10.0% to 1 ppm, 5 ppm, and 10 ppm NO2 at 25 ± 2 °C, respectively. It was shown that the obtained non-modified carbon nanomaterials can be used successfully used for room temperature detection of nitrogen dioxide. It was found that the increase in relative humidity (RH) of air induced growth of response, and this effect was facilitated after reaching RH ~35% for CNFs synthesized at elevated pressures.

Among the known synthesis procedures and reagents for unsupported Ni–Mo–W catalysts, there is no consensus about optimal preparation conditions of their precursors. In the present work, Ni–Mo–W precursors were prepared via three preparation techniques—hydrothermal synthesis, precipitation method and spray drying—after the synthesis of complex compounds in solution. Ni–Mo–W precursors were studied by the XRD analysis, SEM methods, Raman and UV-vis spectroscopies and XPS measurements and used for the hydrotreatment of straight-run gasoil. Precursors prepared by hydrothermal synthesis contain particles with stacked plate shapes, while other methods provide spherical particles. The formation of different amounts of individual molybdates, tungstates or mixed phases such as W1−xMoxO3 possibly doped by Ni was detected. The precipitation technique results in the formation of spheres, with W located at the center and is unavailable for catalysis. The catalytic activity increased when all active metals are available for the feedstock, and a more mixed phase containing Ni, Mo and W is formed. This mixed phase is realized when the synthesis of the Ni–Mo–W precursors is carried out in solution followed by spray drying. The resulting catalyst has 1.2–4 times higher activity than catalysts prepared by other methods.

Two new isomeric complexes [CuBr2(R-bian)] (R = 4-Me-Ph (1), 2-Me-Ph (2)) were obtained by reacting copper(II) bromide with 1,2-bis[(2-methylphenyl)imino]acenaphthene ligands and characterized. The crystal structure of 2 was determined by X-ray diffraction analysis. The copper atom has a distorted square-planar environment; the ω angle between the CuN2 and CuBr2 planes is 37.004°. The calculated ω parameters for optimized structures 1 and 2 were 76.002° and 43.949°, indicating significant deviations from the ideal tetrahedral and square-plane geometries, respectively. Molecules 2 form dimers due to non-covalent Cu···Br contacts, which were analyzed by DFT calculations. The complexes were also characterized by cyclic voltammetry and UV-Vis spectroscopy. A quasi-reversible Cu(II)/Cu(I) redox event with E1/2 potentials of 0.81 and 0.66 V (vs. SHE) was found for 1 and 2, respectively. The electronic absorption spectra showed the presence of Cu(I) species as a result of the partial reduction of the complexes in the acetonitrile solution. Both complexes were tested as homogenous catalysts for the oxidation of isopropylbenzene (IPB) in acetonitrile at low temperatures. Differences in the mechanism of the catalytic reaction and the composition of the reaction products depending on the oxidizing ability of the catalyst were revealed.

Perovskite-type samples La1-xCaxCo1-xTixO3/KIT-6 (x = 0-0.5) were synthesized by citrate method. KIT-6 is partially embedded in the perovskite structure. The complete reduction of cobalt in perovskites in the presence of KIT-6 occurs at a temperature of ca. 670 degrees C due to the formation of a cobalt silicate phase. With the substitution of titanium for cobalt cations, the complete reduction of cobalt occurs at temperatures above 720 degrees C. The pro-portion of cobalt that is reduced at temperatures below 500 degrees C increases with an increase in the ratio of Co3+/Co2+ cations. Partial substitution of cobalt cations with titanium cations decreases the selectivity ratios S-CH3OH/SC2+OH and S-CH4/SC2-8. The introduction of calcium cations leads, proportionally to its content, to a strong decrease in selectivity to methanol and an increase in selectivity for light hydrocarbons C2-8 in syngas conversion. It was shown that the maximum selectivity for higher alcohols with a low selectivity for methanol is observed at x = 0.3 on a sample containing calcium. A significant amount of the cobalt carbide phase Co2C in the used KIT-6 -free sample of LaCoO3 is accompanied by the predominance of the methanation reaction (CH4 selectivity 58.7%). The synthesized samples on KIT-6 have higher selectivity to alcohols compared to a conventional CoAl oxide catalyst and somewhat lower activity in syngas conversion.

Nanostructured powders xFe/nano-Al2O3 with the Fe loading of x = 0.0 – 5.0 wt

Nanostructured powders xFe/nano-Al 2 O 3 with the Fe loading of x = 0.0 – 5.0 wt% were obtained using laser vaporization by CO 2 laser. XRF, XRD, HRTEM, PL and UV–Vis DRS techniques were employed to investigate physicochemical, structural and optical properties of the synthesized nanopowders with the average particle size of 9 nm. Nanopowders xFe/nano-Al 2 O 3 as model catalysts were tested in isobutane dehydrogenation reaction. The results obtained were compared with similar data for the xFe/γ Pb -Al 2 O 3 systems synthesized by the conventional sol–gel method. According to XRD and UV–Vis DRS data, in the series of xFe/nano-Al 2 O 3 samples a great part of Fe 3+ ions is in the disordered environment of subsurface layers of Al 2 O 3 nanocrystallites, predominantly in the tetrahedral coordination. In distinction to samples of the xFe/γ Pb -Al 2 O 3 series, in the case of nanostructured xFe/nano-Al 2 O 3 powders the formation of Fe 2 O 3 phase does not occur at any concentrations of iron or conditions of testing. The analysis of the PL spectra of xFe/nano-Al 2 O 3 powders also showed the presence of surface sites of Fe 3+ ions, which were not detected for xFe/γ Pb -Al 2 O 3 . Catalytic testing of the xFe/nano-Al 2 O 3 series samples in isobutane dehydrogenation revealed the formation of the iron active sites that ensure catalytic activity of the samples. Differences in the catalytic properties of FeO x /Al 2 O 3 samples obtained by the sol–gel method and laser vaporization are related to different states of Fe 3+ ions. Thus, the xFe/nano-Al 2 O 3 nanopowders, in contrast to xFe/γ Pb -Al 2 O 3 , contain a large amount of active Fe 3+ sites. These sites, being involved in the dehydrogenation reaction, are present predominantly on the surface of the nanopowders.

The optimal conditions for the synthesis of platinized graphitic carbon nitride (Pt/g-C3N4) have been found. It was investigated as a catalyst for the production of hydrogen from aqueous solutions of triethanolamine (TEOA) under irradiation with visible light. The highest photocatalytic activity of 450 μmol h−1 g−1 and an apparent quantum efficiency of 1.1% were demonstrated by the 1% Pt/g-C3N4 sample prepared from melamine by calcining at 600 °C for 2 h.

Laser vaporized xCr/Al2O3 nanopowders with the particle size of ca. 15 nm were studied by XRF, EDX, HRTEM, XRD, DD, BET, TGA, UV-Vis DRS, Raman and PL spectroscopy methods as a catalytic system in dehydrogenation of isobutane. The nanopowders were found to contain not only the Cr6+ ions located on the surface of nano -particles, but also two different types of Cr3+ sites as components of the gamma-Al2O3 solid solution. One type consists of the bulk Cr-b(3+) sites in a strong crystal field. Another type is represented by the Cr3+s sites residing near the surface of xCr/Al2O3 nanoparticles. Such sites are in a weak crystal field. It was shown that catalytic activity of the nanostructured xCr/Al2O3 system is provided by the high content of surface Cr-s(3+) sites. The results obtained make it possible to propose the nanopowders obtained by laser synthesis as a promising catalytic system that can be used in the development of highly active catalysts for dehydrogenation of alkanes with the decreased chromium content.

Commercial NiMoP/Al2O3 catalyst was reactivated by a solution of citric acid and orthophosphoric acid after a commercial operation and oxidative regeneration. Catalysts were described with using of many different methods, such as N-2 adsorption, UV-vis DRS, FTIR, Raman, XPS spectroscopy, and HRTEM. Catalytic properties were measured in hydrotreating of dibenzothiophene and SRGO using a fixed bed high-pressure flow reactor. Reactivation with citric and orthophosphoric acids resulted in the significantly recovery of HDS activities. The maximal recovery of activity was overseen for the catalyst treated with a solution of orthophosphoric acid in the concentration corresponded to the ratio P/Ni = 0.2.

Isotherms of Ge(IV) and Cu(II) ions sorption on to the weakly basic anion-exchange resin AN-31 from chloride solutions have been constructed and described. The dependence of equilibrium parameters of Ge(IV) and Cu(II) ions sorption from chloride ions concentration was shown. Based on the electron spectra of diffuse reflectance of copper-containing sorbent, isotherms of sorption and isomolar copper–germanium ions distribution diagram in solutions with different chloride concentrations the nature of extracted particles has been established, and the effect of the mineral background on the sorbent capacity has been determined. The synergistic effect of Cu(II) ions sorption in the presence of Ge(IV) ions has been established. It was found that the ionic and uncharged associates formed by hydroxy-chloride polynuclear cuprate(II) cations and methagermanate anions extract from the chloride solutions onto AN-31. The possibility of selective Cu(II) ions sorption from germanium containing 1 M chloride solutions in wide range of Ge(IV):Cu(II) molar ratios from 1:3 to 1:1 has been established.

The effect of alumina structure (γ‐, η‐, χ‐Al2O3) on the long‐term stability of industrial‐like Cr2O3/Al2O3 dehydrogenation catalysts under industrial dehydrogenation conditions is studied. It is shown that the type of alumina support determines physicochemical and catalytic stability of the catalyst: η‐Al2O3 is the most stable against irreversible deactivation, whereas χ‐Al2O3 is the least stable. One of the possible reasons of predominant stability of η‐Al2O3‐based catalyst is its relatively high sintering stability under real plant conditions. High‐temperature (>800 °C) calcination, sometimes used to compare stabilities of chromia/alumina catalysts, appears to be unable to simulate industrial aging because of the inconsistency of the phase composition of industrially and artificially aged catalysts.

BACKGROUND Preparation of homogeneous oxide coatings on the surface of fiberglass is a difficult task due to hydrophobicity of the fiberglass support. NiO-TiO2 cannot coat the fiberglass surface homogeneously. In the present study, SiO2 was added in the NiO-TiO2. A sol-gel method was used to prepare Ni-Si-Ti sol and this was used to coat fiberglass and form a complex Ni-Si-Ti oxide system supported on its surface. The catalyst was tested for hydrocarbon oxidation reaction. RESULTS The as-prepared material is a mixture of TiO2 in the anatase modification and SiO2 in the amorphous phase. UV-visible diffusion reflectance spectroscopy confirmed the presence of Ni-Oh(2+) cations in the film bulk. Introduction of silica to the sample ensured a uniform distribution of the Ni-Ti oxide system on the fiberglass surface and its durable retention there at 600 degrees C. The Ni-Si-Ti mixed oxide supported on fiberglass demonstrated a higher catalytic activity in the oxidation of n-heptane, compared to Ni-Ti oxide/fiberglass catalyst. It is stable even at 600 degrees C, the temperature at which the maximum n-heptane conversion of 93% was reached. CONCLUSION Adding SiO2 in NiO-TiO2 can coat fiberglass homogeneously as SiO2 can coat hydrophobic surfaces such as fiberglass. This research provides a method with which to coat metal oxide catalyst on fiberglass that is very active and stable for oxidation of hydrocarbons even at high temparatures, compared to that without adding SiO2. (c) 2019 Society of Chemical Industry

A comprehensive study of optical and catalytic properties of highly dispersed single-phase eta-, gamma- and gamma*-Al2O3 ([Cr3+] similar to 10(-4) wt.%) powders and the related model chromia-alumina catalysts with different chromium content ([Cr3+] = 0.25, 0.5 and 1 wt%) was carried out. The catalytic characteristics (product yield, conversion and selectivity) in isobutane dehydrogenation to isobutylene were measured for all the samples under consideration. The surface Cr-s(3+) luminescence centers were detected by photoluminescence spectroscopy in all the samples. The content of Cr-s(3+) centers in the samples was estimated before and after isobutane dehydrogenation. It was shown that the amount of surface Cr-s(3+) centers correlates with isobutylene yields of the reaction. Among the studied samples, the maximum amount of Cr-s(3+) luminescence centers was found for the model 1% Cr/gamma-Al2O3 catalyst. This sample has the highest values of isobutane conversion and isobutylene yield. The comprehensive study of the Cr/Al2O3 systems made it possible to propose a method for predicting the catalytic activity of nanostructured materials using the photoluminescence detection of surface luminescence centers and their quantitative evaluation.

Diffusion of water into Zr-containing silica fiberglass materials was studied at room temperature by infrared spectroscopy. Several types of experiments were performed: (a) rehydration with H2O of fiberglass materials previously calcined in air at 450 degrees C and under vacuum at 180 degrees C; (b) isotopic experiments for uncalcined fiberglass materials using D2O with and without the presence of sodium. Water diffusion coefficients were determined in each case. It was suggested that the transfer of the protons and water molecules occurred by different mechanisms: the protons diffused through the hydroxyl groups via the relay mechanism like in liquid water, whereas water diffused more slowly in the form of molecular water.

During the preparation of stoichiometric LaAlO3 type oxide from an aqueous solution of La and Al nitrate salts, using starch as template, a layered intermediate - disordered mixed lanthanum and aluminum hydroxycarbonate exists in the 300-700 degrees C calcination temperature range. According to calcination temperature a variable content of anions/OH is observed as well as changes in the coordination environment of La and Al cations are providing distortions in the structure. The nuclei of LaAlO3 appears within a mixed La-Al hydroxycarbonate matrix at similar to 700 degrees C. This phase crystallizes at 900 degrees C after decomposition of the major part of bulk carbonates. The surface layer of perovskite particles formed by stacked nanocrystallites is enriched in La cations and contains residual hydroxyls and carbonates, which results in distortion of the local environment of both cations creating oxygen defect sites as well. Such a microheterogeneity is partly retained up to 1300 degrees C. (C) 2017 Elsevier B.V. All rights reserved.