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Using ferromagnetic resonance method, we performed measurements of two-dimensional periodic arrays of disc-shaped cobalt particles with different diameters a=450 and 900 nm and the distance between them l=2 a and 3 a with temperature variation in the range T = 140 −300 K. The first derivative of the microwave absorption spectrum was registered. With the increase of T additional peaks on both sides from the main peak that move aside from it, all peaks show an increase of the intensity and a decrease of the width. Dependences of the resonance field on T shows saturation-like behavior with increasing temperature. They move to higher temperatures and show sharper behavior with a increase and l decrease, respectively. An increase of a leads to the intensity decrease and width increase of all three adsorption peaks. [ABSTRACT FROM AUTHOR]

The effect of amines, imines and heterocycle compounds on conversion has been studied in transfer hydrogenation of camphor and 2-PrOH catalyzed by Raney® nickel. Small amount (5 mol% to nickel) of N-containing compound significantly decreases catalyst activity. It has been shown that the poisoning effect mostly depends on molecular size of amines and heterocyclic compounds. For aniline and cyclohexylamine the dependence of camphor conversion on poison/nickel ratio was obtained. Additionally, benzaldehyde, cinnamaldehyde demonstrated higher reactivity compared corresponding imines under transfer hydrogenation conditions. Obtained data explain low activity of nickel-based catalysts when N-containing compounds are presented in reaction mixture. [Display omitted] • Poisoning effect of N-containing compounds on Raney® Ni activity in TH was shown. • For amines and heterocycles poisoning effect correlates with molecular size. • Using cyclohexylamine as titrant TOF of Raney® Ni in TH was calculated as 1.0 h−1. • Low reactivity of imines compared to carbonyl compounds in TH was demonstrated. [ABSTRACT FROM AUTHOR]

Transfer hydrogenation (TH) is considered as one of the most promising ways to convert biomass into valuable products. This study aims to demonstrate the performance of high-loaded Ni-based catalysts in the TH of phenolic compounds such as guaiacol and dimethoxybenzenes. The experiments were carried out under supercritical conditions at 250 °C using 2-PrOH as the only hydrogen donor. Ni-SiO2 and NiCu-SiO2 were synthesized using the eco-friendly original method based on supercritical antisolvent coprecipitation. It has been found that guaiacol is rapidly converted into 2-methoxycyclohexanol and cyclohexanol, while the presence of Cu impedes the formation of the latter product. Transformations of dimethoxybenzene position isomers are slower and result in different products. Thus, 1,3-dimethoxybenzene loses oxygen atoms transform into methoxycyclohexane and cyclohexanol, whereas the saturation of the aromatic ring is more typical for other isomers. The Cu addition increases specific catalytic activity in the TH of 1,2-and 1,3-dimethoxybenzene compared to the Cu-free catalyst. [ABSTRACT FROM AUTHOR]

Abstract: Small bimetallic Pd–Fe particles supported on a well ordered alumina film grown on NiAl (110) were studied focusing on the geometric, electronic, adsorption, as well as magnetic properties. The morphology, growth mode and surface composition were investigated by combining scanning tunneling microscopy (STM), temperature-programmed desorption (TPD) and infrared spectroscopy (IRAS) using CO as a probe molecule. Information on the electronic properties of the bimetallic systems was obtained by means of X-ray photoelectron spectroscopy (XPS). These measurements were amended by in situ ferromagnetic resonance spectroscopy to address the magnetic properties of the bimetallic particles. The subsequent deposition of the metals at 300K varying the order of metal deposition resulted in two distinct bimetallic systems. Pd deposited on existing Fe particles forms a shell, however, FMR and XPS suggest that intermixing of Pd and Fe occurs to some extent. For the reverse order, a larger amount of Fe is required to coat Pd particles, due to the strong tendency of Pd to segregate to the surface of the particles. [Copyright &y& Elsevier]

The wax appearance temperature (WAT), being one of the key characteristics of waxy crude oil and other waxy substances, is used for the necessary assessment of the phase stability of materials during various technological processes. However, the determination of this parameter as well as peculiarities of wax formation under high gas pressure suffers from the lack of suitable techniques for this task. To address this issue, an attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) method has been applied for the first time to measure the WAT of waxy crude oil under high gas pressure. Carbon dioxide (CO2), nitrogen, and natural gas were used in the study due to their widespread applicability as injection gases in enhanced oil recovery methods. The S2/S1 versus temperature method based on changes in the band of rocking vibrations of the CH2 group was applied to determine WAT. It was found that the ATR FT-IR method based on the proposed dependence S2/S1 versus temperature gives lower WAT values compared to those observed by viscometry, magnetic resonance imaging inspection, and cross-polarized microscopy methods for the waxy crude oil studied. A detailed analysis was carried out using variable-temperature ATR FT-IR spectra of waxy crude oil in the temperature region near the WAT. Essentially different dynamics of wax crystal formation in waxy oil sample and model paraffin solution were demonstrated during the cooling process. The results obtained by high-pressure ATR FT-IR showed that CO2 and natural gas reduce the WAT, while nitrogen has virtually no effect. In addition, for the studied oil, it was found that high pressure of CO2 and natural gases leads to a visual decrease in the amount of wax crystals precipitated, but not to the complete disappearance of microcrystals at a certain temperature and pressure. The results obtained proved that ATR FT-IR can be an effective method for proper determinations of WAT under high-pressure conditions similar to those met in practice. [ABSTRACT FROM AUTHOR]

Highly dispersed Ni‐TiO2 catalyst has been studied in the process of preparation and under catalytic transfer hydrogenation reaction conditions in supercritical 2‐propanol (250°C, 70 bar) using electron spin resonance in situ. Electron spin resonance in situ has been used to study the process of the catalyst passivation and subsequent reduction of the oxide layer in the gas flow. Reduction of the NiO layer on the surface of passivated Ni nanoparticles has been detected in supercritical 2‐propanol, which is in agreement with kinetic modeling data. It has been found that the reduction of the nickel oxide layer in supercritical 2‐propanol occurs at a lower temperature compared with the reduction in hydrogen flow, according to in situ electron spin resonance study. [ABSTRACT FROM AUTHOR]

The influence of the reaction medium on the surface structure and properties of a Ni-based catalyst used for the reductive transformations of O-, N-, and S-containing aromatic substrates under hydrogen transfer conditions has been studied. The catalysts were characterized by XRD, XPS, and IR spectroscopy and TEM methods before and after the reductive reaction. It has been shown that the conversion of 1-benzothiophene causes irreversible poisoning of the catalyst surface with the formation of the Ni2S3 phase, whereas the conversion of naphthalene, 1-benzofuran, and indole does not cause any phase change of the catalyst at 250 °C. However, after the indole conversion, the catalyst surface remains enriched with N-containing compounds, which are evenly distributed over the surface. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Base-free transfer hydrogenation of menthone by primary and secondary alcohols as a hydrogen donor under sub- and sc conditions. • The similar H -donor activity of all alcohols under non-catalytic sc conditions. • Only secondary alcohols demonstrate a high H -donor activity in the presence of Raney® Ni under subcritical conditions. • A quasi-equilibrium of isomeric menthone/isomenthone mixture reached via enolization under sc conditions. Abstract The base-free transfer hydrogenation (THR) of menthone with six aliphatic alcohols as hydrogen source has been developed under sub- and supercritical conditions. Under sc conditions (at 350 °C and 78–210 atm) without any catalyst, all alcohols demonstrated the similar H -donor activity, which was high enough. The menthone conversion was about 64 ± 5% for 5 h of the reaction, whereas the selectivity on menthol reached 92–99% for all alcohols except MeOH (73%). The non-catalytic THR at 250 °C was very slow and the conversion in the most active 2-PrOH was only 7.0–7.5% for 9 h of the reaction. Under subcritical conditions at 150 °C, the non-catalytic menthone reduction was negligible in all alcohols. But in secondary 2-PrOH and 2-BuOH, the base-free THR catalyzed by Raney® nickel results in excellent conversion and selectivity of menthol at 150 °C, whereas no conversion of menthone was observed in primary alcohols under the same reaction conditions. A quasi-equilibrium of isomeric menthone/isomenthone mixture reached via enolization was evaluated under sub- and supercritical conditions and the Gibbs energies of the isomerization in each alcohol were calculated. [ABSTRACT FROM AUTHOR]

Mixed Co-Ni bimetallic systems with the structure of a solid substitution solution have been synthesized using the supercritical antisolvent precipitation (SAS) method, which uses supercritical CO2 as an antisolvent. The systems obtained have been characterized in detail using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared (FTIR) spectroscopy, and magnetostatic measurements. It has been found that Co-enriched systems have a defective hexagonal close-packed (hcp) structure, which was described by a model which embedded cubic fragments of packaging into a hexagonal close-packed (hcp) structure. It has been shown that an increase in water content at the precipitation stage leads to a decrease in the size of cubic fragments and a more uniform distribution of them in Co-enriched systems. It has also been shown that mixed systems have the greatest coercivity in the line of samples. Ni-enriched bimetallic systems have a cubic close-packed (ccp) structure with modified crystal lattice parameters. [ABSTRACT FROM AUTHOR]

This paper describes the chemical engineering aspects for the preparation of highly active and stable nanocomposite photocatalysts based on N-doped TiO2. The synthesis is performed using titanium oxysulfate as a low-cost inorganic precursor and ammonia as a precipitating agent, as well as a source of nitrogen. Mixing the reagents under a control of pH leads to an amorphous titanium oxide hydrate, which can be further successfully converted to nanocrystalline anatase TiO2 through calcination in air at an increased temperature. The as-prepared N-doped TiO2 provides the complete oxidation of volatile organic compounds both under UV and visible light, and the action spectrum of N-doped TiO2 correlates to its absorption spectrum. The key role of paramagnetic nitrogen species in the absorption of visible light and in the visible-light-activity of N-doped TiO2 is shown using the EPR technique. Surface modification of N-doped TiO2 with copper species prevents its intense deactivation under highly powerful radiation and results in a nanocomposite photocatalyst with enhanced activity and stability. The photocatalysts prepared under different conditions are discussed regarding the effects of their characteristics on photocatalytic activity under UV and visible light. [ABSTRACT FROM AUTHOR]

Mixed Ni-Al oxide catalytic precursors with different elemental ratios (20, 50, and 80 wt.% Ni0) were synthesized using green supercritical antisolvent co-precipitation (SAS). The obtained oxide precursors and metal catalysts were characterized in detail by X-ray diffraction (XRD) analysis, atomic pair distribution function (PDF) analysis, CO adsorption, and high-resolution transmission electron microscopy (HRTEM). It was found that the composition and structure of the Ni-Al precursors are related to the Ni content. The mixed Ni1−xAlxO oxide with NiO-based crystal structure was formed in the Ni-enriched sample, whereas the highly dispersed NiAl2O4 spinel was observed in the Al-enriched sample. The obtained metal catalysts were tested in the process of anisole H2-free hydrogenation. 2-PrOH was used as a hydrogen donor. The catalyst with 50 wt.% Ni0 demonstrated the highest activity in the hydrogenation process. [ABSTRACT FROM AUTHOR]

Binary Ni–Cu heterogeneous catalysts are known to demonstrate excellent activity in conventional hydrogenation of phenolic compounds, and Cu addition facilitates hydrodeoxygenation (HDO). In this study, we aimed to show the effect of Cu on the specific catalytic activity and selectivity of Ni–Cu catalysts in transfer hydrogenation, in which 2-PrOH was used as a solvent and an H donor. Catalytic transformations of anisole were studied in sub- and supercritical alcohol at 150 and 250 °C. The catalysts were prepared using an environmentally friendly supercritical antisolvent coprecipitation method, which makes it possible to obtain well-dispersed particles (less than 7 nm) at high metal loading (up to 50 wt.%). When copper is added, deactivation of the catalyst in transformations of anisole, including HDO, is observed. The experimental data and the appropriate kinetic analysis demonstrate that there is a decrease in the rate of anisole conversion accompanied by an increase in the concentration of acetone formed during the dehydrogenation of 2-PrOH. [ABSTRACT FROM AUTHOR]

[Display omitted] The spectral characteristics of ethylene absorbed by ionic liquids (ILs) containing silver ions were studied by in situ ATR-FTIR spectroscopy at high pressure. Three different states of ethylene were observed based on the band shift of out-of-plane bending vibrations (ωCH 2) due to van der Waals interactions, hydrogen bonds, and π-complex formation with silver ions. Thus, ethylene can be used as an IR-sensitive probe molecule for characterizing interactions with ILs and other substances. [ABSTRACT FROM AUTHOR]

• Ni/Al 2 O 3 and Ni-Co/Al 2 O 3 showed high activity in transfer hydrogenation of phenolics. • Ni/Al 2 O 3 primarily promotes hydrodearomatization of phenolic compounds. • The addition of Co to Ni facilitates hydrodeoxygenation of anisole and guaicol. The study investigated the transfer hydrogenation of guaiacol, anisole, phenol, and positional isomers of dimethoxybenezene using 2-PrOH as the H-donor over Ni, Co, and Ni-Co catalysts. The catalysts, which contained 5 wt% metal, were prepared by the deposition-precipitation method. The results showed that the catalysts had developed a pore structure and fine metal particles. The Ni and Ni-Co catalysts demonstrated exceptional activity in the transfer hydrogenation of phenolic compounds with a substrate to metal molar ratio of 100 to 1. Furthermore, the addition of Co to Ni significantly impacted the selectivity of transfer hydrogenation promoting hydrodeoxygenation of anisole and guaiacol. [Display omitted] [ABSTRACT FROM AUTHOR]

Five crude oil samples with different physical properties have been studied with respect to asphaltene stability. The attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic imaging approach of n-heptane-induced precipitation has been used to monitor crude oil behaviour under dilution with a flocculation agent. For each sample, the dynamics of asphaltene precipitation has been observed by applying this chemical imaging method. Based on these data, the stability of crude oil samples has been compared and the correlation between asphaltene stability and crude oil properties has been proposed. [ABSTRACT FROM AUTHOR]

A biotemplate method was used for the synthesis of self-doped TiO 2 photocatalysts via the impregnation of sheep wool fibers with a solution containing titanium hydroxocomplexes under mild hydrothermal conditions (115 °C, 170 kPa), followed by the removal of the wool template during calcination in air at 600 °C. An intermediate wool-TiO 2 composite, formed as a product of hydrothermal impregnation of a wool biotemplate, was comprehensively studied using IR spectroscopy, XRD, SEM, TG analysis, and DSC with mass spectrometric analysis of evaporation products to evaluate the mechanism of TiO 2 crystallization. The phase composition, morphology, texture, and optical properties of the synthesized TiO 2 photocatalysts were studied using XRD, SEM, nitrogen adsorption/desorption, and UV–Vis diffuse reflectance spectroscopy. High-temperature treatment after hydrothermal impregnation led to the formation of anatase and rutile TiO 2 nanocrystallites with a characteristic size of 15–20 nm. The as-prepared TiO 2 photocatalysts had an optical band gap of ∼3.0 eV due to the high content of the rutile phase but also absorbed visible light due to impurity atoms and defects. The samples exhibited very high photocatalytic activity in the degradation of Rhodamine B dye, which was used as a probe molecule, under both UV and visible light. Based on the XPS and EPR results, the enhanced photocatalytic activity of the prepared photocatalysts was attributed to the self-doping effect due to the many defects (Ti3+ sites and oxygen vacancies) formed during TiO 2 crystallization, probably via the reduction of Ti4+ to Ti3+ in disproportionation reactions of disulfide bonds involving titanium hydroxocomplexes. [Display omitted] • Visible-light TiO 2 photocatalysts are synthesized using wool as a biotemplate. • Ti hydroxocomplexes are used for efficient hydrothermal impregnation of wool fibers. • Self-doped TiO 2 provides fast degradation of Rhodamine B under UV and visible light. • The enhanced photocatalytic activity is attributed to Ti3+ and oxygen vacancy defects. • Strong self-doping effect occurs due to disproportionation of keratin disulfide bonds. [ABSTRACT FROM AUTHOR]

[Display omitted] • TMOS synthesis from SiO 2 materials and sc MeOH was developed in a flow reactor. • Both circulating flow and two-cascade continuous flow reactors were designed and used. • Molecular sieves 3 Å placed outside of a heated zone were applied to remote a released water. • The highest TMOS concentration was achieved for silica gel dissolution. • Equilibrium constant K eq of the reversible reaction was determined. An original method for direct synthesis of tetramethyl orthosilicate from SiO 2 raw minerals and supercritical methanol was developed for the first time in a flow mode. The process promoted by KOH was performed at 270 °C and 100 atm using 3 Å zeolite molecular sieves to shift the reversible reaction toward TMOS formation by removing released water. The equilibrium constant K eq of the reaction was determined as 0.839E-08. Silica gel (100 wt% SiO 2), quartz sand (97 wt% SiO 2), expanded perlite (73 wt% SiO 2) and vermiculite (38 wt% SiO 2) were tested as SiO 2 minerals. The highest equilibrium concentration of TMOS equal to 20.4 g/L was achieved for silica gel that can be increased using larger amount of water adsorbent. [ABSTRACT FROM AUTHOR]

Highlights: [•] Different forms of SiO2 react slowly with methanol at 350°C to give mainly TMOS. [•] Some N-unsubstituted benzazoles increase considerably the amount of reacted SiO2. [•] The key role of heterocycles is nucleophilic assistance to the reaction. [•] Azole ring of heterocycles is methylated by MeOH during the reaction. [•] Both SiO2-surface and TMOS catalyze the methylation of benzazole. [ABSTRACT FROM AUTHOR]

[Display omitted] • The simultaneous screening of multiple ionic liquids under controlled environment. • In situ ATR-FTIR spectroscopic imaging was used in high-throughput analysis of ILs. • ATR-FTIR imaging provides a platform for the simultaneous screening of multiple ILs. • Array of ILs was studied for sorption separately of water vapour and toluene vapour. • The information about ILs was obtained rapidly, quantitatively and simultaneously. In situ characterisation of ionic liquids under a controlled environment has been performed in a high throughput manner using macro ATR-FTIR spectroscopic imaging. 14 different ionic liquids with cations 1-butyl-3-methylimidazolium ([C 4 mim]), 1-butyl-2,3-dimethylimidazolium ([C 4 mmim]) and 1-butyl-3-methylpyrrolidinium ([C 4 C 1 pyrr]) and anions hexafluorophosphate ([PF 6 ]), tetrafluoroborate ([BF 4 ]), bis(trifluoromethylsulfonyl)imide ([NTf 2 ]), perchlorate ([ClO 4 ]), trifluoromethanesulfonate ([CF 3 SO 3 ]), nitrate ([NO 3 ]), methanesulfonate ([CH 3 SO 3 ]) and trifluoroacetate ([TA]) were studied. The ionic liquids were deposited onto the measuring surface of the ATR crystal in the corresponding accessory hosted in the FTIR imaging system. Then these samples were exposed to a controlled environment of toluene and water vapour and spectra acquired simultaneously. Changing the structure of the cation head group from [C 4 mim] to [C 4 mmim] or [C 4 C 1 pyrr] only had a small effect on the toluene absorption while increasing the length of the alkyl chain of the cation (e.g. [C 10 mim]) has shown a significant increase in toluene absorption. The ionic liquids with the anion [NTf 2 ] were found to absorb the highest amount of toluene followed by [CF 3 SO 3 ], then [PF 6 ], [ClO 4 ], [NO 3 ] and [TA], and the lowest amount of toluene was absorbed in ionic liquids with [BF 4 ] or [CH 3 SO 3 ] anions. The amount of water absorbed increases in the order: [C 4 mim][CH 3 SO 3 ] > [C 4 mim][TA] > [C 4 mim][NO 3 ] > [C 4 mim][CF 3 SO 3 ] > [C 4 mim][ClO 4 ] ~ [C 4 mim][BF 4 ] ~ [C 4 mmim][BF 4 ] > [C 10 mim][BF 4 ] > [C 4 mim][PF 6 ] ~ [C 4 mmim][PF 6 ] > [C 4 mim][NTf 2 ] ~ [C 4 mmim][NTf 2 ] ~ [C 4 C 1 pyrr][NTf 2 ]. This work has demonstrated that spectroscopic imaging provides a platform for the simultaneous screening of multiple ionic liquids in situ, when under controlled environments. [ABSTRACT FROM AUTHOR]

In this work ZrO 2 –SiO 2 aerogels with ZrO 2 content of 3, 6 and 10 mol. % in the form of transparent blocks were synthesized using the sol-gel method. The possibility of introducing ZrO 2 into a SiO 2 aerogel without considerable decline of the optical characteristics of the material was shown for the first time. Aerogel samples were studied by several techniques including UV–Vis, ATR-FTIR spectroscopy and nitrogen adsorption, the refractive index was determined using beam tests ("Extracted beams" of the VEPP-4M complex). It was shown that the addition of ZrO 2 to SiO 2 aerogel increases the refractive index without increasing of the aerogel density. For the first time, the possibility of obtaining highly transparent ZrO 2 –SiO 2 aerogel blocks with acceptable optical characteristics for radiator in Cherenkov detectors has been demonstrated. This result makes it possible to achieve high refractive indices in the production of aerogel blocks for Cherenkov detectors to increase their performance. [ABSTRACT FROM AUTHOR]

A series of monoterpenoids (citral, carvone, menthone, camphor) as well as cyclohexanone and hex-5-en-2-one were subjected to transfer hydrogenation with PriOH/Raney nickel system at 82 or 150 °C. Among monoterpenoids, citral and carvone underwent full conversion at 82 °C within 5 h. [ABSTRACT FROM AUTHOR]

A new ring opening reaction was found while attempting to isolate the imines from ortho‐heteroatom substituted anilines and camphor‐like bicyclic ketones. The benzoazoles containing a cyclopentanemethyl group at position 2 of the heterocycle were isolated instead of the expected imines. The detailed study of the transformation, including EPR experiments, revealed the most probable radical mechanism. The proposed reaction pathways were confirmed by quantum chemical calculations. The dichotomy of 1–2 and 2–3 bonds cleavage is discussed together with the evaluation of the stereochemical outcome of the reactions. The benzoazoles obtained via the new reaction are of particular interest for the medicinal chemistry. [ABSTRACT FROM AUTHOR]

• The Al-Si oxides were synthesized for the first time via supercritical antisolvent precipitation of Al-Si-containing sols. • The alumina and silicon-doped alumina obtained by the SAS method were shown to be mesoporous and thermal stable materials. • The alumina composed of X-ray amorphous particles (2-5 nm) forming a narrow pores size distribution (3-5 nm). A method of alumina and silica sols precipitation in supercritical CO 2 has been developed for the first time to prepare alumina and silica doped alumina. The silicon content of samples is varied within the range from 0 to 30 mol. %. The approach suggested can be considered as a development of supercritical antisolvent (SAS) method that is widely used to prepare powders from solutions but not sols. The alumina and silicon-doped alumina obtained are shown to be mesoporous materials with narrow size distribution in the range of 3–5 nm. The high-temperature treatment of the sample containing 10 mol. % of Si results in the formation of γ-Al 2 O 3 phase followed by its transition into the δ -Al 2 O 3 phase at 1200 °C without α-Al 2 O 3 phase formation. It is demonstrated that the gradual introduction of silica into the alumina allows one to fine-tune the strength and amount of acid sites existing in oxides. [ABSTRACT FROM AUTHOR]

The Si/Al ratio is a key parameter of acid-base, structural, textural and, consequently, catalytic properties of amorphous crystalline (micro- and mesoporous) aluminosilicates. The changes of structural and textural characteristics of Al-Si aerogels with gradual increase of aluminum content are investigated. Aerogels were prepared via sol-gel method using prehydrolysed tetraethoxysilane and aluminium isopropoxide stabilized by acetylacetone. The gelation of the obtained sols took place in the presence of ammonia with the following drying in supercritical isopropanol. It was shown all aluminum reacts with prehydrolyzed tetraethoxysilane forming spherical particles in case the content of Al in the samples is less than 20 mol %. Aluminum drives the increase of interparticle coupling leading to the particle agglomeration, which is associated with the increase of the particle size and decrease of specific surface area and pore volume. For the samples with the aluminum content of >50 mol % the formation of pseudoboehmite plate-like particles is observed. The pseudoboehmite particles prevent the sintering of SiO 2 particles that leads to the increase of the aerogel specific surface area and pore volume. In case the high aluminum content (>80 mol %) the silica particles serve as a connector between boehmite plates. The ratio between Brønsted and Lewis acid sites decreases gradually with the increase of aluminum content of the aluminosilicate aerogels. [ABSTRACT FROM AUTHOR]

Sub- and supercritical alcohols are known as effective hydrogen donors. In this work, transfer hydrogenation (TH) of furfural with C 1 -C 4 alcohols has been studied under sub- and supercritical conditions. In the range of 230–275 °C, the observed activation energy of catalyst-free transformations of furfural into furfuryl alcohol and some minor byproducts has been shown to be 98 ± 8, 64 ± 4 and 79 ± 6 kJ/mol for EtOH, 1-PrOH and 2-PrOH, respectively. The use of a Ni/γ-Al 2 O 3 catalyst results in higher rate constants compared to the catalyst-free TH. Nevertheless, the selectivity to furfuryl alcohol in the presence of the catalyst does not exceed 50% vs 70–80% for the catalyst-free transformations. Thus, this study shows the high donor potential of alcohols in TH under both catalytic and catalyst-free conditions. A special attention is paid to primary alcohols, because they are highly demanded as H-donors due to economic and environmental reasons. [Display omitted] • Primary C 1 -C 4 alcohols demonstrate high donor activity in furfural TH. • Catalyst-free TH of furfural and 1-PrOH has lower activation energy than 2-PrOH. • Selectivity to furfuryl alcohol of catalyst-free furfural TH reaches 70–80%. • Use of Ni/γ-Al 2 O 3 results in higher rate constants but the lower selectivity. [ABSTRACT FROM AUTHOR]

The silica-supported Fe-containing catalysts prepared using FeSO4 as a precursor exhibit high activity toward the reaction of benzene with benzyl chloride. [ABSTRACT FROM AUTHOR]

Transfer hydrogenation of anisole in 2-PrOH has been studied as a model reaction for lignocellulose processing. The reaction was studied over high-loaded Ni-based catalysts synthesized via supercritical antisolvent precipitation of a Ni precursor and sols of four oxides: Al 2 O 3 , SiO 2 , TiO 2 , and ZrO 2. It was demonstrated that the oxide support significantly affects the structure of the catalysts, their activity, and selectivity. The best performance in the transfer hydrodeoxygenation of anisole was shown by Ni supported on alumina at 250 °C, which was explained by the highest dispersion of Ni0 particles in this catalyst and by the highest concentration of acid centers. [Display omitted] • Well-dispersed high-loaded Ni catalysts were synthesized by SAS method. • Obtained catalysts show excellent activity in transfer hydrogenation of anisole. • Acid sites and the smaller Ni particles facilitate hydrodeoxygenation of anisole. [ABSTRACT FROM AUTHOR]

Abstract: A one-pot synthesis method for the controllable growth of magnetite nanoparticles directly during the process of co-precipitation using citrate ions was developed. The effects of the concentration of citrate ions and the solution pH on the characteristics of magnetite particles with sizes in the range of 4–10 nm synthesized by the method of co-precipitation were studied. The results showed that the specified concentration of citrate ions allowed the preparation of magnetite particles with a definite size that exhibited superparamagnetic behaviour in a particular temperature range. As the concentration ratio of citrate to iron ions was increased from 0 to 0.11, the average size of the prepared magnetite particles decreased from 10.5 to 4.4 nm. As a result, the superparamagnetic blocking temperature decreased from 300 to 20 K, the saturation magnetisation decreased from 50 to 20 emu g−1, and the average magnetic moment decreased from 8000 μB to 340 μB (at T = 300 K). The obtained experimental data proved that the size effects of the magnetite nanoparticles can be attributed to the capping of the magnetite surface by adsorbed citrate ions. Thus, the suggested approach allows magnetite nanoparticles to be prepared with an optimum particle size around superparamagnetic threshold that prevents their irreversible agglomeration and simultaneously allows them to be removed from a solution at an acceptable rate. [Copyright &y& Elsevier]

[Display omitted] • Poisoning titration is precise approach to quantify Raney® Ni active centers. • Effect of 15 poisons (thiols, amines, acids) on catalyst activity measured. • TOF of Raney® Ni probed by thiophenol titration was 2.4 h–1 at 82 °C. • C–S bond cleavage of thiophenol did not occur during poisoning of Raney® Ni. For the first time, the poisoning effect of 15 different chemical compounds on Raney® nickel catalyst has been comparatively studied in the transfer hydrogenation of camphor using 2-PrOH as a solvent and a hydrogen donor. It has been shown that thiophenol, HCl and H 3 PO 4 demonstrate the strongest poisoning action under the reaction conditions: no camphor conversion was observed at 5 mol.% of poison-to-nickel ratio. A strong chemical binding of thiophenol molecules to the catalyst surface without C S bond cleavage was proved by XRF, TPD methods, CHNS analysis, and FTIR spectroscopy. It was shown that the poisoning titration with thiophenol is an effective and convenient tool to calculate the number of active sites for Ni based catalysts directly, measuring catalytic activity in target chemical reaction, which was defined correspondently as 2.4 h−1 and 9.6 × 10–5 mole for Raney® nickel catalyst in the transfer hydrogenation. [ABSTRACT FROM AUTHOR]

Graphical abstract Detected by the in situ EPR spectroscopy immobilized nitro radical anions generated in the course of Au/Al 2 O 3 -catalyzed nitrobenzene hydrogenation demonstrate the abnormal hyper-fine splitting and serve as intermediates of the reaction. [ABSTRACT FROM AUTHOR]

In this work, in situ ATR-FTIR spectroscopy was used to study the interaction of CO 2 and a series of 1-alkyl-3-methylimidazolium tetrafluoroborate С n MIMBF 4 (n = 2, 4, 6, 8, 10) ionic liquids. A detailed analysis of the infrared spectra acquired from ionic liquids and sorbed СО 2 was performed as ionic liquids with different the alkyl chain lengths were subjected to changing pressures of СО 2 and temperature. With a longer alkyl chain length, an increase in the shift of the CH stretching vibrations bands of alkyl groups and BF stretching vibrations of BF 4 − anions is observed during CO 2 sorption. This indicates the disaggregation of alkyl chains and anions. There is a correlation with the position of the wavenumber of the ν 3 asymmetric stretching CO 2 band and the length of the alkyl chain. It was found that some of the CO 2 adsorbed by ionic liquids does not interact with the ionic liquid but is "free" in the bulk of the alkyl chains. For the first time, ATR-FTIR spectroscopy was used to determine the thermodynamic parameters of CO 2 sorption in ionic liquids. It was demonstrated that the values of enthalpy and entropy obtained by analysis of the ATR-FTIR spectra are consistent the data obtained by other methods. A correlation was found between the enthalpy of sorption of CO 2 and the wavenumber of the ν 3 band. This opens up the possibility of using CO 2 as an IR-sensitive probe molecule to characterize the acid-base properties of ionic liquids and determine the enthalpy of CO 2 sorption. Unlabelled Image • In situ ATR-FTIR spectroscopy was used to study CO 2 sorption in a homologous series of ionic liquids. • ATR-FTIR spectroscopy was used to determine the thermodynamic parameters of CO 2 sorption in ionic liquids. • A correlation was found between the enthalpy of CO 2 sorption and the wavenumber of the ν 3 band of CO 2. • CO 2 can be used an IR-sensitive probe molecule to characterize the properties of ionic liquids. [ABSTRACT FROM AUTHOR]

We demonstrate, for the first time, the application of FTIR spectroscopic imaging approach in situ to monitor the precipitation process of oil asphaltenes, induced by n-heptane under flow using microfluidic devices. The aggregation of asphaltenes induced by n-heptane flow with subsequent precipitation and formation of the deposits was studied for solution containing 5 wt % of asphaltenes in benzene. The FTIR spectroscopic approach with an array detector allowed us to assess the spatial distribution of the chemical components and their amounts in the system and display the process of aggregates formation with a spatial resolution of few micrometres. This chemical imaging technique shows that the flow of heptane results in non-equilibrium condition when the local content of the flocculants reaches the threshold amount needed for the asphaltenes aggregation. The relatively slow process of heptane diffusion into the benzene induces the asphaltenes aggregation followed by their precipitation and compaction. Fast asphaltene aggregation process under heptane flow leads to the formation of the deposit firmly fixed to the surface, while the precipitates formed during the diffusion process of heptane into the benzene can be easily taken from the channel. The FTIR spectroscopic imaging of the deposits formed revealed the spatial inhomogeneity of the precipitated asphaltenes in the direction of the heptane flow in microfluidic channel which is reflected in their different chemical composition and the presence of different functional groups (CH 2 –CH 3 , C O, S O). In particular, it was found that asphaltenes of different types and different CH 2 /CH 3 ratios gradually start to precipitate in the direction of n-heptane flow. The data obtained demonstrate the importance of local concentration of flocculants as well as local characteristics of the system for asphaltenes aggregation, and overall precipitation process in flow regime. Image 1 • Asphaltene deposition process was studied with FTIR spectroscopic imaging under flow in situ. • FTIR imaging monitor the changes of the amount and spatial distribution of solvent, asphaltenes and flocculent simultaneously. • The content and average length of alkyl groups increases in the asphaltene deposit in the direction of the heptane flow. • The deposit in different functional groups (CH2–CH3, C=O, S=O) is heterogeneous in the direction of the heptane flow. [ABSTRACT FROM AUTHOR]