Nitrogen Physical Adsorption Research Articles

Photocatalytic degradation of industrial acrylonitrile wastewater by F\u2013S\u2013Bi\u2013TiO2 catalyst of ultrafine nanoparticles dispersed with SiO2 under natural sunlight

Highly active photocatalyst, having certain anti-ionic interfering function, of F, S and Bi doped TiO2/SiO2 was used for the first time to degrade the organic pollutants in acrylonitrile industrial wastewater under natural sunlight. The photocatalyst were prepared and characterized by UV–Vis, XRD, TEM, EDS, Nitrogen physical adsorption and XPS technique. UV–Vis analysis revealed addition of F, S and Bi into the lattice of TiO2 led to the expansion of TiO2 response in the visible region and hence the efficient separation of charge carrier. The photocatalytic potential of as prepared catalyst to degrade acrylonitrile wastewater under simulated and natural sunlight irradiation was investigated. The extent of degradation of acrylonitrile wastewater was evaluated by chemical oxygen demand (CODCr). CODCr in wastewater decreased from 88.36 to 7.20 mgL−1 via 14 h irradiation of simulated sunlight and achieved regulation discharge by 6 h under natural sunlight, illuminating our photocatalyst effectiveness for refractory industrial wastewater treatment. From TEM results, we found that SiO2 could disperse the photocatalyst with different component distributions between the surface and the bulk phase that should also be responsible for the light absorption and excellent photocatalytic performance. The XPS analysis confirmed the presence of surface hydroxyl group, oxygen vacancies.

A Highly Dispersed Copper Nanoparticles Catalyst with a Large Number of Weak Acid Centers for Efficiently Synthesizing the High Value-Added 3-Methylindole by Aniline and Biomass-Derived Glycerin

An excellent catalyst with a large number of weak acid centers and highly dispersed copper nanoparticles embedded in mesoporous SBA-15 carrier was successfully constructed for the purpose of efficient conversion of aniline with biomass-derived glycerin to the high value-added 3-methylindole, in which the catalyst of Cu/SBA-15 was modified with Al2O3, La2O3 and CoO in sequence. The modified carrier and the copper-based catalysts were studied by scanning electron microscopy and energy-dispersive X-ray (SEM–EDX) spectroscopy, nitrogen physical adsorption, ammonia temperature programmed desorption (NH3-TPD), hydrogen temperature programmed reduction (H2-TPR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric and differential thermal analysis (TG–DTA) and inductively coupled plasma (ICP) emission spectroscopy. The research found that the Cu/CoO/La2O3/Al2O3/SBA-15 catalyst exhibited a very good catalytic performance with 3-methylindole yield up to 73.3% and selectivity reaching 86.4%. Besides, only a 3.9% yield decreased after the catalyst was circulated seven times. The characterizations revealed that Al2O3 could enhance the polarity of the carrier, thereby the interaction between the active component and the composite carrier was strengthened and the dispersion of copper was increased significantly. Adding La2O3 to Cu/SBA-15-Al2O3 could weaken the acidity and inhibit the formation of carbon deposits. CoO promoter could increase the number of weak acid centers, which was conducive to a good dispersion of active component and the high selectivity of 3-methylindole. Furthermore, the reaction pathway of gas-phase synthesis of 3-methylindole from glycerin and aniline on Cu/CoO/La2O3/Al2O3/SBA-15 was explored.

Preparation of Composite Monolith Supercapacitor Electrode Made from Textile-Grade Polyacrylonitrile Fibers and Phenolic Resin.

In this work a composite monolith was prepared from widely available and cost effective raw materials, textile-grade polyacrylonitrile (PAN) fibers and phenolic resin. Two activation procedures (physical and chemical) were used to increase the surface area of the produced carbon electrode. Characterization of the thermally stabilized fibers produced was made using differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and Carbon-Hydrogen-Nitrogen(CHN) elemental analysis, in order to choose the optimum conditions of producing the stabilized fibers. Characterization of the produced composite monolith electrode was performed using physical adsorption of nitrogen at 77 °K, cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrical resistivity in order to evaluate its performance. All the electrodes prepared had a mixture of micropores and mesopores. Pressing the green monolith during the curing process was found to reduce largely the specific surface area and to some degree the electrical resistivity of the chemically activated composite electrode. Physical activation was more suitable than chemical activation, where it resulted in an electrode with specific capacity 29 F/g, good capacitive behavior and the stability of the electrical resistivity over the temperature range −130 to 80 °C. Chemical activation resulted in a very poor electrode with resistive rather than capacitive properties.

Efficient no‐glycerol biodiesel production using a novel biotemplated hierarchical porous‐structure CaO(O)

AbstractBACKGROUNDIn order to obtain an effective solid base with high surface area and hierarchical distribution of pore size, CaO(O) was synthesized via an exotemplating method, using radish as template and calcium acetate as precursor.RESULTSThe CaO(O) obtained by calcination of the impregnated biomorphic template demonstrated effective catalytic activity for the coupling transesterification of vegetable oil to produce biodiesel under mild reaction conditions using tri‐components (methanol, oil and methyl acetate) as resources. High yield of biodiesel, 98.6%, was obtained with a molar rapeseed oil/methyl acetate/methanol ratio of 1:1:8 under 65 °C at 2 h, which is greatly shorter than 6 h over commercial calcium oxide (CaO).CONCLUSIONVarious techniques including nitrogen physical adsorption, X‐ray diffraction (XRD), Fourier‐transform infrared (FTIR), thermogravimetric (TG), carbon dioxide‐chemical adsorption and morphology have been employed to characterize the samples. These results demonstrated that the synthesized CaO derived from plant template has a large surface area and various pore diameter distribution which cause hierarchical basic sites over the solid base. © 2020 Society of Chemical Industry

Synthesis of Nanoporous Titanosilicates and Their Structural Characterization by Physical Nitrogen Adsorption

Mesoporous titanosilicate structures synthesized by the sol–gel method using the cetylpyridinium template at different Ti/Si ratios are characterized by high specific surface areas ABET ≈ 800 m2/g and Aext ≈ 900–1000 m2/g, as well as the shape of the isotherms of physical nitrogen adsorption characteristic of the mesoporous molecular sieve MCM-41 with an adsorption branch rising and a section of reversible capillary condensation at a relative pressure of 0.21 < p/p0 < 0.42. An increase in the Ti/Si ratio and pH values leads to a decrease in the dispersion and surface area of the samples. FTIR spectra confirm the presence of titanium(IV) in the silicate framework. The incorporation of titanium(IV) affects the morphology of titanosilicate samples and reduces the ordering of cylindrical mesopores characteristic of MCM-41.

ZIF-assisted construction of magnetic multiple core-shell Fe3O4@ZnO@N-doped carbon composites for effective photocatalysis

Magnetic Fe3O4@ZnO@nitrogen-doped carbon (Fe3O4@ZnO@N-C) composites with multiple core-shell structures have been successfully synthesized by calcination of ZIF-8 coated Fe3O4@ZnO core-shell nanocrystals. The morphologies and microstructural characteristics are investigated by X-ray diffraction, Fourier-transform infrared spectrometer, transmission electron microscopy, X-ray photoelectron spectroscopy, physical adsorption of nitrogen, and UV–vis diffuse reflectance spectroscopy. The photocatalytic performances are tested by degrading methylene blue (MB) in aqueous solutions under the irradiation of imitative sunlight. The photocatalytic trials indicate that the Fe3O4@ZnO@N-C composites exhibit improved degradation efficiency compared to the Fe3O4@ZnO precursor. The photocatalytic efficiencies of the as-prepared Fe3O4@ZnO@N-C composites towards MB are 93% under irradiation of imitative sunlight for 90 min and still maintained to be 87% after 6 recycles, which shows very good stability and recyclability. Nitrogen-doped carbon is believed to extend the absorption spectra to the visible-light region. The photodegradation kinetics via using the as-prepared Fe3O4@ZnO@N-C composite as a novel photocatalyst are systematically investigated.

Preparation of hydrophobic hierarchical pore carbon–silica composite and its adsorption performance toward volatile organic compounds

Carbon–silica materials with hierarchical pores consisting of micropores and mesopores were prepared by introducing nanocarbon microspheres derived from biomass sugar into silica gel channels in a hydrothermal environment. The physicochemical properties of the materials were characterized by nitrogen physical adsorption (BET), scanning electron microscopy (SEM), and thermogravimetric (TG), and the adsorption properties of various organic waste gases were investigated. The results showed that microporous carbon materials were introduced successfully into the silica gel channels, thus showing the high adsorption capacity of activated carbon in high humidity organic waste gas, and the high stability and mechanical strength of the silica gel. The dynamic adsorption behavior confirmed that the carbon–silica material had excellent adsorption capacity for different volatile organic compounds (VOCs). Furthermore, the carbon–silica material exhibited excellent desorption characteristics: adsorbed toluene was completely desorbed at 150°C, thereby showing superior regeneration characteristics. Both features were attributed to the formation of hierarchical pores.

Syngas production by dry reforming of methane using lyophilized nickel catalysts

In this work, lyophilized nickel catalysts were synthesized and compared with a commercial catalyst (CCom) in the process of dry reforming of methane. Ni-Al2O3 catalysts were prepared by epoxide-initiated gelation method and lyophilized with different percentage of active phase: 5 wt% (LNi5), 10 wt% (LNi10), 15 wt% (LNi15) and 20 wt% (LNi20). The catalysts were characterized by physical nitrogen adsorption, infrared spectroscopy, X-ray diffractometry, scanning electron microscopy and X-ray photoelectron spectroscopy. The catalytic tests were performed at 600 °C, 700 °C and 800 °C. All catalysts were active in the reforming reactions except the LNi5 and CCom catalysts at temperatures of 600 °C and 700 °C. The LNi10 catalyst at 800 °C has presented the highest syngas production. The CCom showed the highest carbon deposition at 600 °C with 2.26 mg which represents 4.52% of the initial weight of the catalyst. Increasing the nickel content from 5 wt% to 10 wt% resulted in a syngas gain of 1.31 μmol/min, 0.86 μmol/min and 1.25 μmol/min at 600 °C, 700 °C and 800 °C, respectively. The increase of the active phase from 10 wt% to 15 wt% and 20 wt% did not present significant effects in the syngas production. The lyophilization process in the drying stage of the catalyst has proved to be quite satisfactory in the dry reforming of methane.

Synthesis, characterisation and electrochemical evaluation of a functionalised coating for mild steel corrosion protection

ABSTRACTA functionalised coating for mild steel corrosion protection was prepared in this study. A composite material SBA-15 (silicon oxide) was used as a mild steel corrosion inhibitor. The porous matrix (SBA-15) was loaded with fluconazole (F), as an inhibitor container. A sol–gel technique was used to synthesise SBA-15; and the active molecule (F) was extracted from an outdated medication using methanol as solvent. The final composite was obtained by SO2 dispersion in a methanol-F solution. The composite material was dispersed in a nitrocellulose resin, and it was characterised by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), Fourier Transform Infrared Spectrometry (FTIR), and physical adsorption of Nitrogen. Coatings were electrochemically evaluated by electrochemical impedance spectroscopy (EIS) tests, using a chloride/sulphate solution prepared from NaCl and (NH4)2SO4. The results demonstrated the effectiveness of the inhibitor delivery system and the consequent protection of metal against the corrosion process.

Facile and low-cost fabrication of ZnO/biochar nanocomposites from jute fibers for efficient and stable photodegradation of methylene blue dye

The present work demonstrates the fabrication of ZnO loaded on biomass porous carbon through pyrolysis of jute fibers pretreated by Zn(OAc)2. XRD, Raman SEM, TEM, XPS and physical adsorption of nitrogen were used to characterize the products. Dark adsorption and photocatalytic degradation of methylene blue (MB) was run to evaluate their activities for removal of organic pollutants. It was demonstrated that the composition and structure of ZnO/JFC composites depended on the ratios of jute fibers to zinc salt. Through adjusting the mass ratio between raw materials, a fine composite of ZnO monocrystalline nanorods embedded on the porous carbon walls was obtained, which exhibited a much better efficiency for MB decolorization. The removal of MB was found to be pH dependent, and the optimized removal efficiency reached to 99% and the mineralization level was over 93% at pH 7.0 following 30 min under UV illumination. The kinetic studies showed the decolorization of MB followed pseudo first-order kinetics, and the rate constants were determined using the Langmuir–Hinshelwood model, indicating KLH = 0.024 L∙mg−1and kc = 4.01 mg∙L−1 min−1. Moreover, the ZnO nanorods/JFC composite was stable and showed a high efficiency of over 80% during seven cycles of utilization and regeneration. Examination for the real sample contaminated by MB proved that the presence of metal ions and other organic pollutants hardly affected its photocatalytic ability. It was demonstrated that ZnO/JFC composites could be fabricated through simultaneous pyrolysis of jute fibers and zinc acetate. These composites were provided with the advantages of high photocatalytic efficiency, convenient recycling and long-term stability, and were expected to be applied in environmental engineering and manufacturing for organic dyes removal.

Change of pore structure and uniaxial compressive strength of sandstone under electrochemical coupling

The effect of electrochemical modification of the physical and mechanical properties of sandstone from Paleozoic coal measure strata was investigated by means of liquid nitrogen physical adsorption, X-ray diffraction and uniaxial compressive strength (UCS) tests using purified water, 1 mol/L NaCl, 1 mol/L CaCl2 and 1 mol/L AlCl3 aqueous solution as electrolytes. Electrochemical corrosion of electrodes and wire leads occurred mainly in the anodic zone. After electrochemical modification, pore morphology showed little change in distribution, decrease in total pore specific surface area and volume, and increased average pore diameter. The total pore specific surface area in the anodic zone was greater than in the cathodic zone, but total pore volume was less. Mineralogical composition was unchanged by the modification. Changes in UCS were caused by a number of factors, including corrosion, weakening by aqueous solutions, and electrochemical cementation, and electrochemical cementation stronger than corrosion and weakening by aqueous solutions.

The Influence of Nano Fluid Compared With Polyethylene Glycol and Surfactant on Wettability Alteration of Carbonate Rock

The purpose of this research is to enhance oil recovery of the carbonate rock by wettability alteration using silica suspended in brine, polyethylene glycol (PEG), and sodium dodecyl sulfate (SDS). Hydrophilic silica with a different mean Nano size 52, 65 nm was synthesized from local sand by a chemical method. The synthesized Nano silica was characterized by AFM to determine the average particle size and distribution, and surface area was measured by physical adsorption of nitrogen. The wettability alteration was studied by dipping the carbonate rock in different concentrations of Nano silica (0.01-1wt. %) for a certain silica size suspended in brine for different dipping times as well as for PEG and SDS. The contact angle was measured before and after each run in order to recognize the extent of affinity change (wettability) of the carbonate. The results showed that the Nano particles were more reactive due to their high surface area these particles had the highest potential for wettability alteration. The contact angle decreased with decrease particle size and increase concentration. The PEG polymer and SDS surfactant showed less influence on wettability alteration compared with Nano fluids.

Preparation of highly cross‐linked hydrophilic porous microspheres poly(N,N′‐methylenebisacrylamide) and poly(N,N′‐methylenebisacrylamide‐co‐acrylic acid) with an application on the removal of cadmium

An effective polymerization system was developed for the synthesis of highly cross‐linked hydrophilic monodispersed microspheres with both the micropores and mesopores inside. A series of poly(N,N′‐methylenebisacrylamide) (PMBA) microspheres with the diameters ranging from 100 to 300 nm were synthesized by distillation precipitation polymerization with N,N‐dimethylacetamide (DMAC) as the porogen, acetonitrile as the solvent, and MBA as the cross‐linker and monomer. The particle size, morphology, and porosity varied according to the variation of the DMAC content. The porosity was determined by physical adsorption of nitrogen, and reached the maximum at 7.5 vol% of DMAC with the specific surface area at 135.8 m2 g−1 and the total pore volume at 0.43 cm3 g−1. The porous and hydrophilic microspheres showed excellent swelling property in water and adsorption property for the Cd(II) in aqueous solution. Meanwhile, carboxylic groups were incorporated into the porous microspheres to achieve porous poly(N,N′‐methylenebisacrylamide‐co‐acrylic acid) (P (MBA‐co‐AA)‐P), which exhibited obvious synergies of the pores and functional groups on the adsorption and provided a perspective application of the Cd(II) removal.

Efficient adsorption/reduction of aqueous hexavalent chromium using oligoaniline hollow microspheres fabricated by a template‐free method

AbstractBACKGROUNDUniform and well‐dispersed hollow microspheres of oligoaniline were synthesized by a facile and template‐free method in alkaline medium. The morphology of oligoanilines was controlled from hollow to hard microspheres, by simply changing the volumes of alkaline medium. SEM, TEM, XRD, FTIR and physical adsorption of nitrogen were used to characterize the products. Hexavalent chromium ion uptake experiments were run with these aniline oligomers.RESULTSAdsorption experiments showed that the removal of chromium ions was strongly dependent on the initial pH of the solution. The pseudo‐second‐order kinetic and Langmuir isotherm models were well correlated with the experimental data. The adsorption of Cr(VI) and synergistic reduction to Cr(III) were confirmed by analyzing remnant chromium in the liquid and XPS detection of the exhausted adsorbent. A redox/pseudo‐protonation process was suggested as the mechanism to explain the Cr(VI) removal. The adsorbed chromium ions could be desorbed by NaOH solution. The higher desorption efficiency of 96.2% was achieved by using 1.0 mol L‐1 NaOH as the desorption agent.CONCLUSIONSIt was observed that the hollow microsphere were the most effective adsorbent of the three adsorbents and its removal efficiency reached 99% to remove 60 mg L‐1 Cr(VI). The facile fabrication, efficient removal of Cr(VI) and simple regeneration offered an option to remove Cr(VI) contamination from natural water and industrial wastewater. © 2017 Society of Chemical Industry

Effect of TS-1 Treatment by Mixed Alkaline on Propylene Epoxidation

Titanium silicate-1 (TS-1) was treated with a mixed alkaline of tetrapropyl ammonium hydroxide (TPAOH) and NaOH. It was characterized by XRD, nitrogen physical adsorption, SEM, FT-IR, UV–Vis and ICP-OES, and studied in propylene epoxidation. The mixed alkaline treatment with TPAOH/NaOH solution did not destroy the MFI structure of TS-1. With increasing NaOH concentrations, the relative crystallinity and the framework titanium decreased to some extent while the mesopore volume, mesopore diameter, and extra-framework titanium increased appreciably. When NaOH concentration was 0.0333 mol L−1, the best catalytic performance was obtained.

One-pot synthesis of ZnO/oligoaniline nanocomposites with improved removal of organic dyes in water: Effect of adsorption on photocatalytic degradation

ZnO nanoparticles supported on hierarchical oligoaniline microstructures were synthesized in one pot at ambient condition. The ZnO/oligoaniline nanocomposites were characterized by SEM, TEM, XRD, FTIR, TG/DTA, and physical adsorption of nitrogen. The adsorption and photocatalytic efficiency of the resulting materials were evaluated for removal of dyes. The adsorption data for dyes removal met pseudo-second-order kinetic model. The role of adsorption on photocatalysis was investigated under different reaction conditions. Simultaneous adsorption and photocatalysis (SAP) emerged enhancing effect on cationic dyes, while equilibrium adsorption followed by photodegradation (EAP) improved the catalytic rate of anionic dye. The apparent first-order model was chosen as kinetic equation to estimate photocatalytic reaction. Under SAP mode, ZnO/oliganiline nanocomposite exhibited a higher catalytic rate compared to pure ZnO nanoparticles for dyes photodegradation. The incorporation of oligianiline support significantly enhanced the photocatalytic efficiency of ZnO nanoparticles.

Catalytic conversion of cellulose into polyols using carbon-nanotube-supported monometallic Pd and bimetallic Pd–Fe catalysts

A series of carbon nanotube (CNT)-supported monometallic Pd and bimetallic Pd–Fe catalysts were synthesized and employed for catalytic hydrogenolysis of cellulose into polyols, including hexitol, ethylene glycol (EG), 1,2-propanediol (1,2-PG), and glycerol (Gly). The physicochemical properties of the catalysts were characterized by nitrogen physical adsorption measurements, X-ray diffraction analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy. The total yield of hexitol, EG, 1,2-PG, and Gly in hydrolytic hydrogenation of cellulose was 37, 55, and 53% for Pd/CNTs, Pd–Fe/CNTs (Pd:Fe = 1:1), and Pd–Fe/CNTs (Pd:Fe = 1:2), respectively. Addition of Fe to Pd significantly modified the physicochemical properties of the nanoparticles and their catalytic performance, especially regarding hexitol selectivity. The promoting effect of Fe, especially for hexitol selectivity, compared with the monometallic catalyst is due to the fact that incorporation of Fe may stabilize Pd0 nanoparticles and lead to downshift of the d-band center of Pd metal nanoparticles by charge transfer from Fe to Pd. Recycling experimental results showed that leaching of Fe resulted in a significant decrease in the hexitol yield obtained using the Pd–Fe/CNTs after the first recycle, further demonstrating that Fe element plays a promoting role for hexitol formation.

CdS quantum dots confined in mesoporous TiO2 with exceptional photocatalytic performance for degradation of organic polutants

In this paper, the mesoporous TiO2 with different concentration of CdS quantum dots (i.e., x% CdS/TiO2) was successfully fabricated by the sol-gel method. The composition, structure and morphology of the nanocomposites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectroscopy (UV–Vis/DRS) and nitrogen physical adsorption test and so on. The proportion of CdS and TiO2 is very important for the photocatalytic performance. As a result, the photocatalytic degradation performance from the most to the least is in the order of 2% CdS/TiO2, 4% CdS/TiO2, 8% CdS/TiO2, pure TiO2 and 1% CdS/TiO2. The photocatalytic (PC) activity of the 2% CdSTiO2 is characterized by photocatalytic degradation of methyl orange, which can be completely degraded within 45 min better than 60 min TiO2 takes. It is also much better than CdS. Moreover, other four organic pollutants, such as methylthionine chloride, bisphenol A, rhodamine B, malachite green can also be degraded quickly on the condition of 2% CdS/TiO2. What's more, the chemical stability and cycling capability of 2% CdS/TiO2 are reflected by five cyclic degradation of methyl orange.

Fe 3 O 4 @SiO 2 ‐SO 3 H nanocomposites: an efficient magnetically separable solid acid catalysts for esterification reaction

Fe3O4@SiO2-SO3H nanocomposites were successfully synthesised as the efficient magnetically separable solid acid catalysts for an esterification reaction. The resultant catalysts were characterised by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, vibrating sample magnetometer (VSM), and nitrogen physical adsorption analyses [Brunauer–Emmett–Teller (BET) theory]. The catalytic activities of as-prepared Fe3O4@SiO2-SO3H nanocomposites were also investigated for the esterification of n-butyl acetate and isoamyl acetate. The acid esterification rate was confirmed by gas chromatography. The results showed that the Fe3O4@SiO2-SO3H nanocomposites can be as candidate cataysts for the concentrated H2SO4 for the esterification reaction of n-butyl alcohol or isoamyl alcohol. More importantly, the magnetic catalysts can be easily separated from the reaction system by a magnetic bar and reused at least three recycles without significant degradation of their activities.

Unsupported trimetallic Ni(Co)-Mo-W sulphide catalysts prepared from mixed oxides: Characterisation and catalytic tests for simultaneous tetralin HDA and dibenzothiophene HDS reactions

Unsupported A-Mo-W (A=Ni or Co) sulphide catalysts were obtained from mixed oxides containing different W:Mo ratios. An in situ liquid-phase sulphidation of the mixed oxides in a batch reactor was followed by catalytic tests in a liquid-phase reaction (at 613K and 70bar), using a mixture of dibenzotiophene (DBT) and tetralin (THN) as the feed. After the catalytic tests, the bulk sulphide catalysts were characterised by nitrogen physical adsorption, XANES/EXAFS, SEM and HR-(S)TEM. The HR-TEM images showed randomly oriented, stacked-layer particles typical of Mo (W) sulphides and an elemental HR-STEM mapping evidenced Mo/W homogeneous distribution in the trimetallic sulphides. The EXAFS results for the trimetallic catalysts are consistent with the presence of nickel or cobalt sulphide domains, and Mo1-xWxS2 solid solutions. The intralayer Mo:W solid solutions were confirmed to be thermodynamically stable with respect to phase separation by DFT calculations, which were also used to aid in the interpretation of the EXAFS results. The effect of the W:Mo ratio on the catalytic properties of the Ni- and Co-containing series was found to be different. For the Ni series, increasing the W content caused an activity increase in THN hydrodearomatization (HDA) relative to DBT hydrodesulphurization (HDS), while it had little influence on the relative contribution of the direct desulphurisation (DDS) route with respect to the previous hydrogenation (HYD) route for DBT HDS. In contrast, for the Co series, the activities and selectivities were essentially insensitive to the W content. Both the Ni and Co series of unsupported sulphides were more selective for the HYD route in DBT HDS than a supported NiMo/Al2O3 catalyst.