Metal−Support Interactions in Co/Al2O3 Catalysts: A Comparative Study on Reactivity of Support

Oxidative desulfurization of dibenzothiophene via layered graphitic carbon nitride-coordinated transition metal as a catalyst

In this study, graphitic carbon nitride (g-C3N4) has been synthesized. The cobalt-doped (CoO/g-C3N4) samples prepared by the impregnation method and their catalytic property were investigated on the ODS process.

Direct observation of the evolving metal-support interaction of individual cobalt nanoparticles at the titania and silica interface

Understanding the metal–support interaction (MSI) is crucial to comprehend how the catalyst support affects performance and whether this interaction can be exploited in order to design new catalysts with enhanced properties. Spatially resolved soft X-ray absorption spectroscopy (XAS) in combination with Atomic Force Microscopy (AFM) and Scanning Helium Ion-Milling Microscopy (SHIM) has been applied to visualise and characterise the behaviour of individual cobalt nanoparticles (CoNPs) supported on two-dimensional substrates (SiO_xSi(100) (x < 2) and rutile TiO₂(110)) after undergoing reduction–oxidation–reduction (ROR). The behaviour of the Co species is observed to be strongly dependent on the type of support. For SiO_xSi a weaker MSI between Co and the support allows a complete reduction of CoNPs although they migrate and agglomerate. In contrast, a stronger MSI of CoNPs on TiO₂ leads to only a partial reduction under H₂ at 773 K (as observed from Co L₃-edge XAS data) due to enhanced TiO₂ binding of surface-exposed cobalt. SHIM data revealed that the interaction of the CoNPs is so strong on TiO₂, that they are seen to spread at and below the surface and even to migrate up to ∼40 nm away. These results allow us to better understand deactivation phenomena and additionally demonstrate a new understanding concerning the nature of the MSI for Co/TiO₂ and suggest that there is scope for careful control of the post-synthetic thermal treatment for the tuning of this interaction and ultimately the catalytic performance.

Understanding the metal–support interaction (MSI) is crucial to comprehend how the catalyst support affects performance and whether this interaction can be exploited in order to design new catalysts with enhanced properties.

Catalytic Technologies for Solving Environmental Problems in the Production of Fuels and Motor Transport in Kazakhstan

This research is devoted to solving an environmental problem, cleaning of the Kazakhstan air basin, through treatment of auto-transport toxic exhaust by improving the hydrocarbon composition of motor fuels and neutralizing exhaust gas toxic components. The catalytic hydrodearomatization of gasoline fractions (from the reforming stage) of the Atyrau and Pavlodar Refineries and the neutralization of exhaust gas toxic components from an internal combustion engine (ICE) were studied. Two hydrotreated gasoline fractions were tested during ICE operation. The research shows that 100% benzene conversion is observed over Rh-Pt(9:1)/γ-Al2O3 catalysts; that is, benzene is completely removed from both fractions, and the aromatics content decreases from 56.24–58.12% to 21.29–21.89%, within the values of the Euro-5,6 standard. Catalytic treatment of fuels reduces fuel consumption of the ICE engine by 2–3% compared to the initial gasoline fractions, the CO content in the exhaust gases decreases by 6.6–16.2%, and the hydrocarbon content decreases by 7.8–24.7%. In order to neutralize the ICE exhaust gas toxic components, the catalyst 10% Co + 0.5% Pt/Al2O3 was used, with which the CO conversion reaches 100% and the hydrocarbon conversion 94.2% and 91.5% for both gasoline fractions. The catalysts were characterized by electron microscopy (EM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), thermoprogrammed desorption (TPD) and thermoprogrammed reduction (TPR) methods. It was shown by the TPD and EM methods that at the addition of Pt to the Rh-catalyst, the formation of mixed bimetallic Rh-Pt-agglomerates occurs, and hydrogen appears in the TPD spectrum, adsorbed in the form of a new single peak uncharacteristic for the Rh-catalyst. This leads to high activity and selectivity in the hydrogenation of benzene and aromatic compounds in the gasoline fractions. The XRD and TPR results show the formation of CoAl2O4 spinels, on which inactive oxygen is formed for the oxidation of CO and hydrocarbons. Modification of the catalyst by Pt and Mg prevents spinel formation, thereby increasing the activity of the catalysts.

Supported Cobalt Catalysts for Acceptorless Alcohol Dehydrogenation

The acceptor-less dehydrogenation of 2-octanol was tested over cobalt supported on Al₂ O₃ , C, ZnO, ZrO₂ and various TiO₂ substrates. The catalysts were characterized by ICP, XRD and TGA-H₂ . For Co/TiO₂ P25, the effects of passivation, aging (storage at room temperature), and in situ activation under H₂ were investigated. The catalysts must be tested shortly after synthesis in order to prevent deactivation. Cobalt supported on TiO₂ P25 was the most active and 69 % yield of 2-octanone was obtained, using decane as a solvent. Selectivities for 2-octanone were observed in the range of 90 % to 99.9 %. Small amounts of C16 compounds were also formed due to aldol condensation/dehydration reactions. The catalysts exhibited higher conversion in the dehydrogenation of secondary alcohols (65-69 %), in comparison to primary alcohols (2-10 %). The dehydrogenation of 1,2-octanediol led to 1-hydroxy-2-octanone, with a selectivity of 90 % and 69 % for Co/TiO₂ P25 and Co/TiO₂ P90, respectively.

A magnetic CoRu-CoOX nanocomposite efficiently hydrogenates furfural to furfuryl alcohol at ambient H2 pressure in water

A one-pot synthesized CoRu-CoOX nanocomposite was reported as a magnetically recoverable catalyst for selective hydrogenation of furfural to furfuryl alcohol in water at ambient H2 pressure.

Unifying double flame spray pyrolysis with lanthanum doping to restrict cobalt–aluminate formation in Co/Al2O3 catalysts for the dry reforming of methane

Atomic-sized lanthanum doping via double flame spray pyrolysis leads to remarkable dry reforming of methane performance.

Macroporous Ni foam-supported Co3O4 nanobrush and nanomace hybrid arrays for high-efficiency CO oxidation

Herein, we reported the synthesis of well-defined Co₃O₄ nanoarrays (NAs) supported on a monolithic three-dimensional macroporous nickel (Ni) foam substrate for use in high-efficiency CO oxidation. The monolithic Co₃O₄ NAs catalysts were obtained through a generic hydrothermal synthesis route with subsequent calcination. By controlling the reaction time, solvent polarity and deposition agent, these Co₃O₄ NAs catalysts exhibited various novel morphologies (single or hybrid arrays), whose physicochemical properties were further characterized by using several analytical techniques. Based on the catalytic and characterization analyses, it was found that the Co₃O₄ NAs-6 catalyst with nanobrush and nanomace arrays displayed enhanced catalytic activity for CO oxidation, achieving an efficient 100% CO oxidation conversion at a gas hourly space velocity (GHSV) 10,000hr^-1 and 150°C with long-term stability. Compared with the other Co₃O₄ NAs catalysts, it had the highest abundance of surface-adsorbed oxygen species, excellent low-temperature reducibility and was rich in surface-active sites (Co³⁺/Co²⁺=1.26).

A multifunctional Co-based metal-organic framework: heterogeneous catalysis, chemiluminescence sensing and moisture-dependent solvatochromism

Crystalline materials with multi-catalytic applications are of great value to both fundamental research and practical applications. The platform of metal-organic frameworks (MOFs) is utilized to fabricate a microporous versatile catalyst with high stability. Self-assembly of a flexible ligand, 4-(4-carboxybenzylamino)benzoic acid (H2CBBA), with Co(ii) resulted in a 3D framework, CBBA-Co, with Co3O clusters exposed in the zigzag channels. Upon in situ activation, CBBA-Co exhibited multiple heterogeneous catalytic activities. Theoretical calculations were carried out to give insights into the catalytic process. In addition, CBBA-Co also showed promising potential in optical sensing by virtue of its catalytic activity. The luminol chemiluminescence was greatly enhanced by CBBA-Co, and linear determination of the concentration of H2O2 in the range of 0-30% was established. The successful implementation of CBBA-Co indicates the feasibility and promising future of employing MOFs as an efficient platform for the fabrication and study of multifunctional catalysts, both experimentally and theoretically.

Formation and Coloring Mechanism of Typical Aluminosilicate Clay Minerals for CoAl2O4 Hybrid Pigment Preparation

Different kinds of aluminosilicate minerals were employed to fabricate CoAl₂O₄ hybrid pigment for studying its formation and coloring mechanism. It revealed that the color of the obtained hybrid pigments was determined by the content of Al₂O₃ and lightness of clay minerals. The higher the Al₂O₃ content and the lightness of clay minerals, the better the color parameters of hybrid pigments. During the preparation of hybrid pigments, CoAl₂O₄ nanoparticles were confined to be loaded on the surface of the aluminosilicate minerals, which effectively prevented from the aggregation and the size increase of CoAl₂O₄ nanoparticles. What's more, aluminosilicate mineral might be an ideal natural aluminum source to compensate the aluminum loss due to the dissolution of Al(OH)₃ at alkaline medium during precursor preparation, keeping an optimum molar ratio of Co²⁺/Al³⁺ for formation of spinel CoAl₂O₄ pigments in the process of high-temperature crystallization.

Low-temperature CO oxidation over integrated penthorum chinense-like MnCo2O4 arrays anchored on three-dimensional Ni foam with enhanced moisture resistance

Advanced integrated nanoarray (NA) catalysts have been designed by growing metal-doped Co₃O₄ arrays on nickel foam with robust adhesion.

Cobalt immobilized on hydroxyapatite as a low-cost and highly effective heterogeneous catalyst for alkenes epoxidation under mild conditions

Transition metal Co immobilized on hydroxyapatite with a loading of 0.05 wt% (denoted 0.05 wt% Co/HAP) could catalyze partial oxidation of cyclic alkenes, aromatic alkenes and aliphatic alkenes to yield epoxide products with excellent selectivity at 30 °C with O₂ and iso-butyraldehyde as co-oxidant. The TOF value was as high as 6261 h⁻¹ for epoxidation of cyclohexene. In addition, the prepared 0.05 wt% Co/HAP catalyst can be re-used at least 6 times without significant loss of catalytic activity and selectivity.

Transition metal Co immobilized on hydroxyapatite even with low loading of 0.05 wt% is a low-cost and highly effective heterogeneous catalyst for alkenes epoxidation at 30 °C with O₂ and iso-butyraldehyde as co-oxidant.

Mesoporous silica supported cobalt catalysts for gas phase hydrogenation of nitrobenzene: role of pore structure on stable catalytic performance

Mesoporous silica supported Co catalysts (Co/COK-12 and Co/SBA-16) are active for hydrogenation of nitrobenzene to aniline. The support pore architecture is decisive in maintaining stable catalytic performance.

Solvent-free oxidation of cyclohexane by oxygen over Al–Cu–Co alloys: influence of the phase structure and electrical conductivity on catalytic activity

Cu dissolved in the Al₁₃Co₄ phase promotes the electrical conductivity and catalytic activity of Al–Cu–Co alloys.

Metal–support interaction on cobalt based FT catalysts – a DFT study of model inverse catalysts

It is challenging to isolate the effect of metal–support interactions on catalyst reaction performance. In order to overcome this problem, inverse catalysts can be prepared in the laboratory and characterized and tested at relevant conditions. Inverse catalysts are catalysts where the precursor to the catalytically active phase is bonded to a support-like ligand. We can then view the metal–support interaction as a ligand interaction with the support acting as a supra-molecular ligand. Importantly, laboratory studies have shown that these ligands are still present after reduction of the catalyst. By varying the quantity of these ligands present on the surface, insight into the positive effect SMSI have during a reaction is gained. Here, we present a theoretical study of mono-dentate alumina support based ligands, adsorbed on cobalt surfaces. We find that the presence of the ligand may significantly affect the morphology of a cobalt crystallite. With Fischer–Tropsch synthesis in mind, the CO dissociation is used as a probe reaction, with the ligand assisting the dissociation, making it feasible to dissociate CO on the dense fcc Co(111) surface. The nature of the interaction between the ligand and the probe molecule is characterized, showing that the support-like ligands’ metal centre is directly interacting with the probe molecule.

Rich surface Co(iii) ions-enhanced Co nanocatalyst benzene/toluene oxidation performance derived from Co(II)Co(III) layered double hydroxide

A hierarchical CoCo layered double hydroxide (LDH) nanostructure was constructed through a facile topochemical transformation route under a dynamic oxygen atmosphere. Self-assembled coral-like CoAl LDH nanostructures via the homogeneous precipitation method were also inspected under different ammonia-releasing reagents and solvents. Benzene and toluene were chosen as probe molecules to evaluate their catalytic performance over the metal oxide CoCoO and CoAlO calcined from their corresponding LDH precursors. Nanocatalyst of trivalent Co ions replaced Al(3+) ions in the bruited-like layer had a higher catalytic activity (T99(benzene) = 210 °C and T99(toluene) = 220 °C at a space velocity = 60 000 mL g(-1) h(-1)). Raman spectroscopy, XPS and H2-TPR demonstrated the existence of abundant high valence Co ions that serve as active sites. TPD verified the types of active oxygen species and surface acid properties. It was concluded that the high valence Co ions induced excellent low-temperature reducibility. Surface Lewis acid sites and the surface Oads/Olatt molar ratio (0.61) played relevant roles in determining its catalytic oxidation performance. Our design in this work provides a promising approach for the development of nanocatalysts with exposed desirable defects.

A novel 3D oxide nanosheet array catalyst derived from hierarchical structured array-like CoMgAl-LDH/graphene nanohybrid for highly efficient NOx capture and catalytic soot combustion

A novel 3D oxide nanosheet array catalyst was fabricated using a graphene template induced strategy for highly efficient NO_x capture and catalytic soot combustion.

One-step synthesis of ordered mesoporous CoAl2O4 spinel-based metal oxides for CO2 reforming of CH4

Ordered mesoporous CoAl₂O₄ spinel-based metal oxides were facilely synthesized and utilized as the catalysts for CRM reactions.