Topics in Catalysis最新文献

This work aimed to assess and model the kinetics of bisphenol-S (BPS) removal and mineralization achieved by photo-Fenton-like treatment catalyzed by Cu₂O/Al₂O₃. For this purpose, Cu₂O nanoparticles were prepared by Laser Ablation in Liquid (LAL) and supported on commercial Al₂O₃ powder to be used as catalyst in the degradation of bisphenol S (BPS) via a photo-Fenton-like oxidation process. The produced nanoparticles were characterized by Transmission Electronic Microscopy (TEM) and determined to have an average size of 11 nm. For reference, the BPS removal was also monitored and modelled under photolysis with UV-C and UV-C plus H₂O₂. It was found that the experimental data for both BPS concentration and total organic carbon (TOC), are well fitted by a first-order kinetic model. Regarding temporal BPS concentration profiles, the pseudo-first order kinetic constant values were 0.961, 0.402 and 0.035 min⁻¹ for photo-Fenton, UV-C + H₂O₂ and photolysis, respectively; while for the temporal TOC concentration profiles the estimated pseudo-first order kinetic constant values were 0.086, 0.026 and 0.021 min⁻¹ for photo-Fenton, UV-C + H₂O₂ and photolysis, respectively. The effect of Cu content was also studied in the range of 0 to 2%. The kinetic constant was found to be approximately twice with the 2% Cu₂O/Al₂O₃ system than with the 0.5% Cu content, for both cases, temporal BPS concentration and TOC profiles. Thus, it was concluded that the prepared 2%Cu₂O/Al₂O₃ system is an excellent alternative to catalyze H₂O₂ dissociation and conduct BPS mineralization by a photo-Fenton like process which leads to a near complete mineralization, ca. 94% in 30 min.

The increasing global population and the poor disposal of emerging contaminates have caused water pollution, damaging the environment and the lives of living beings. In this sense, carbon nanostructures have been widely used for electrochemical sensor development and employed in the determination of this species because they improve the electrocatalytic characteristics of sensors, promoting the emergence of new physical-chemical characteristics when combined with other nanomaterials, increasing Lewis basic-acid sites and enhancing the mass transference process. In this context, a variety of electrochemical sensors constructed with different carbon hybrid nanomaterials will be described in the review article, such as carbon black nanostructures, carbon dots, graphene oxide species, carbon nanotubes, rGO/Carbon dots, AgNP/CarbonDot/MWCNT, SiO₂/ZrO₂/Cdot-N, polypyrrole-3-carboxylic acid/Sb₂O₅/reduced graphene oxide, rGO/Carbon dots/AuNPs, CuONPS/Cdot(N) nanostructures, SiO₂/Sm₂O₃/Carbon Modified with Meldola Blue, and others carbon nanocomposites. These modified electrodes performed excellently in the different water pollution determinations.

We discuss activation and reaction of CO₂ on oxide-supported Au nanoparticles in connection with the preparation and characterization of model systems for heterogeneous catalysts, referring mostly to our own studies in the field. These systems are based on crystalline oxide thin films grown on metal substrates, which allows us to characterize them at the atomic scale. Depending on preparation conditions, the oxide-supported Au nanoparticles assume a particular morphology that is largely controlled by electron transfer from the metal substrate through the oxide film or from dopants in the oxide film. If such an electron transfer to the Au nanoparticles is possible, they assume a two-dimensional morphology and electrons can flow from the particle rim to attached CO₂ molecules. This electron transfer leads to the formation of oxalate species that may spill over to the oxide substrate and are available for further reactions. The required structural parameters and the possibilities to monitor the spill-over process are discussed in detail in this paper.

Reactive (photo, electro and plasma) catalysis requires the development of new concepts and approaches that are different from those in use for thermal catalysis, while the common practice is to translate methodologies and modelling from thermal to reactive catalysis. This perspective contribution aims to shed light on the difference between them because their understanding is a conditioning factor in accelerating the progress of reactive catalysis. They play a crucial role in developing technologies for low-carbon chemical production. Emphasis is given to the role of strong localised electrical fields (LEF) generated by the coupling of charges with localised phonon modes, i.e. catalyst vibrations. They play a role in low-temperature catalytic processes, typical of reactive catalysis, which is different from higher-temperature conditions (thermal catalysis). The role of the electrical field in catalytic processes is an emerging area, influencing the chemisorption and surface mobility of adspecies. However, LEFs play a more critical role because they determine the rate and selectivity of the reaction. They are a distinct feature which differentiates reactive from thermal catalysis and, thus, a key feature for their understanding and modelling. However, it is an area still largely unexplored. We discuss some case examples and concepts related to photocatalytic water splitting on TiO₂ (showing that the water layer restructures in the presence of an electric field), the generation of LEFs and relation to electrode nanostructure, as well as their importance to understanding electro-catalysis, and the consequent need to include these aspects in a new modelling approach. The examples provide evidence that explains why new concepts and models are required for reactive catalysis. The discussion spotlights the difference with respect to thermal catalysis and aims to stimulate researchers to view reactive catalysis from a novel research perspective.

Single-Atom Catalysis (SACs) is an emerging frontier with significant potential to bridge the gap between homogeneous and heterogeneous catalysis. Among various chemical processes of interest, the reduction of CO₂ (CO2RR) into valuable chemicals has garnered particular attention. The analogy between SACs and coordination chemistry compounds has highlighted the importance of the supporting matrix. In this study, we explored CO₂ activation on SACs using density functional theory (DFT) calculations. Our analysis focused on nine transition metals (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) and three distinct support materials: nitrogen-doped graphene (4N-Gr), a gold surface (Au(111)), and titanium nitride (TiN), an emerging material with unique properties. Our findings indicate that CO₂ activation on SACs is generally challenging, often requiring dual active centers. SACs based on 4N-Gr and Au(111) showed limited ability to bind CO₂ molecules. Conversely, TiN emerged as a highly promising support, effectively promoting CO₂ activation. This capability stems from the formation of bidentate adducts involving both the dopant and a surface titanium atom of the matrix. Furthermore, TiN-based SACs demonstrated the ability to favour *CO*OH adduct formation (* indicates an adsorbed species) over *COOH or *OCHO during the first electrochemical reduction step, showcasing enhanced reactivity. These results underscore the potential of TiN as a robust support material for SACs in CO2RR, offering new perspectives for efficient CO₂ conversion.

Heterogeneous photocatalysis is a highly efficient process for degrading recalcitrant and emerging pollutants. This work investigates the properties of gallium-indium oxides heterojunction photocatalysts synthesized from a gallium-based liquid metal (Ga_75.5In_24.5 alloy) doped with Cu ions at 5, 7 and 10 wt (Cu_xIG) and without doping (IG). Cu_xIG were synthesized by simple precipitation assisted by a hydrothermal process and subjected to a thermal treatment at 1000 °C. These materials were characterized by XRD, XPS, FT-IR, UV-Vis-IR spectroscopy in diffuse reflectance mode, TGA, and SEM/EDX. These photocatalysts reveal a Cu_xO/In₂O₃/Ga₂O₃ heterojunction. The copper content influences the structural, morphological, optical, and photocatalytic properties. The photocatalytic activity of these materials was investigated in degrading acetaminophen (Ac), a nonbiodegradable and highly recalcitrant compound persistent to conventional treatment processes, at pH 3, 5, 7, and 9. IG photocatalyst showed photocatalytic activity under UVB light (~ 90% Ac degradation at pH 5 and 7). Cu_xIG heterojunction photocatalysts have photocatalytic activity under visible illumination (at pH 5), and the optimal concentration of copper species is at 5% wt. However, Cu_xIG photocatalysts exhibited low stability in cycling; the photoactivity decreased considerably after the first cycle. Different scavengers were used to propose an Ac degradation route.

Flavouring ketones play a significant role in drugs and the flavouring industry. Typically, these ketones are present in berries and their isolation causes significant environmental damage and incurs considerable extraction costs. Therefore, it is essential to synthesize these ketones using green and sustainable routes. This study reports the synthesis of Ni supported on boron nitride-doped carbon catalyst by simple chelation, followed by pyrolysis and reduction. P-XRD diffraction peaks at 44.2, 51.6, and 76.2° of synthesized catalyst corresponding to the (111), (002), and (022) hkl planes for planes of metallic nickel; also, the XPS analysis confirmed the presence of Ni²⁺ and Ni⁰ oxidation states. HR-TEM analysis reveals the core-shell appearance of the catalyst, with Ni nanoparticles surrounded by a graphitic carbon layer. Thus, the synthesized catalyst was utilized as a bifunctional catalyst for the one-pot synthesis of raspberry and zinger ketones via cross-aldol condensation and hydrogenation. Under optimized reaction conditions, the Ni/BNC catalyst showed good activity for both cross aldol condensation of p-hydroxybenzaldehyde with acetone and hydrogenation of PHBA, achieving 99% conversion with 86% selectivity towards raspberry ketone and the catalyst showed good recyclability and a wider range of substrate compatibility.

Graphical Abstract

NiMoW/Zr-SBA-15 supported catalysts have been investigated for modification of SBA-15 by using zirconia incorporation method, with variation of theoretical molar ratio Zr/Si = 0.07. The beneficial effect of EDTA insertion at neutral pH on NiMoW/Zr-SBA-15 oxide catalysts was studied by sol-gel method. EDTA was used as a chelating agent during the impregnation step with a theoretical molar ratio Ni: EDTA = 1:1 adjusting at neutral pH. Then, trimetallic catalysts were characterized at each step of the preparation (drying and calcination). X-Ray diffraction, Transmission electron microscopy and N₂ physisorption results demonstrated that the incorporation of metals did not significantly impact the mesoporous morphology, as evidenced by the persistence of the support’s characteristic reflections. Both synthesized catalysts demonstrate adsorption-desorption isotherms type IV and H1-type hysteresis characteristic of mesoporous materials with uniform morphology. The Atomic absorption spectroscopy and X-ray photoelectron spectroscopy analyses agree that the impregnation of the metallic phases deposited on the surface of the catalysts was effective. By X-ray photoelectron spectroscopy, Raman spectroscopy, and Ultraviolet-Visible diffuse reflectance spectroscopy confirm that the addition of EDTA at neutral pH modifies the nature of the nickel, molybdenum, and tungsten oxide species. Moreover, the formation of nickel oxide species with well-defined octahedral symmetry is enhanced, and the dispersion of molybdenum and tungsten oxide species is optimized. Finally, a change in the oxidation state of the molybdenum oxide species was observed, which has the potential to contribute to more effective HDS catalytic formulations.

Graphical Abstract

Schematic representation of the addition of ethylene diamine tetraacetic acid (EDTA) at a neutral pH, which allows for the effective dispersion of the oxide phase species of molybdenum (Mo) and tungsten (W) on the Zr-SBA-15 support.

Advances in technology have resulted in the vast production of low-cost plastics with tailored properties for many applications in our daily lives. However, the single-use culture coupled with the slow degradation of plastic waste had resulted in the rapid generation of its waste. Limited landfills and traditional incineration methods that attributes to carbon emissions had propelled many researchers to source for alternative chemical upcycling methods to manage plastic waste while enhancing resource recovery. Catalytic hydroconversion which involves the valorisation of plastic to low emission fuels or chemicals with selectivity and lower energy demand had garnered much interest. Specifically, polypropylene which is a major source of plastic waste due to its utilization in numerous products will be focused for this mini review. The current progresses in the catalytic hydroconversion reactions to generate fuels and chemicals from polypropylene will be discussed with emphasis to the catalytic performance, conditions utilized, and the distribution of products obtained. This review will serve to summarize the catalytic developments in the hydrocracking, hydroliquefaction and hydrogenolysis of polypropylene and aid future research discoveries in the modifications and enhancements of the existing processes for chemical upcycling of single and mixed sources of polypropylene to develop low energy intensive, low-cost and less waste generating depolymerization technologies towards the selective production of sustainable fuels and chemicals.

Sulfonamides and their derivatives are being used as potent chemosensors for various ions. Sensing ability of 4-methyl-N-(pyridin-2-yl) benzene-1-sulfonamide (S) was tested towards different cations i.e. Zn²⁺, Fe²⁺, Pb²⁺, Ni²⁺, Sr²⁺, Cd²⁺, Cu²⁺, Co²⁺, Hg²⁺ and Al³⁺ in Dimethyl Sulfoxide (DMSO). S exhibited sensitivity towards ferrous (Fe²⁺) and cupric (Cu²⁺) ions. Solution of S turned yellow from colorless upon interaction with iron and copper ions and a corresponding bathochromic shift was observed. Electronic spectra showed new absorbance peaks at 310 nm and 370 nm after interaction with Fe²⁺ and Cu²⁺ respectively, compared with S absorbance peak at 270 nm. Binding studies indicated 1:1 binding stoichiometry of both metal ions with S. Detection limits for iron and copper were determined to be 0.74 µM and 0.60 µM, respectively. However, their binding constant values came out to be 1.3 × 10⁶ M⁻¹ and 1 × 10⁶ M⁻¹ respectively for Fe²⁺ and Cu²⁺.