CuO Species Research Articles

Material Design of Bimetallic Catalysts on Nanofibers for Highly Efficient Catalytic Reduction of 4-Nitrophenol.

In this study, CuO-TiO2 nanofiber catalysts were fabricated by an electrospinning process, followed by thermal annealing at various temperatures ranging from 300 to 700 °C. The phase transformation from CuO to metallic Cu was carried out through immersion treatment in NaBH4 solution. The resulting CuO-TiO2 and Cu-CuO-TiO2 nanofibrous mats were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) analysis. The results revealed that the crystalline phase composition of the nanofibrous mats considerably affected the efficiency of photocatalytic reduction, where the CuO-TiO2 catalysts with a predominant anatase content was found to be more photoactive than the rutile phase. Similarly, the presence of both Cu and CuO species was more beneficial for promoting the activity of fibers by acting as an interim location for facilitating the electron transfer. The fabricated Cu-CuO-TiO2 nanofibrous mat with a ratio presented high conversion (∼99%) within several minutes with the apparent pseudo-first-order rate constant of 0.42 and 0.50 min-1 in the absence and presence of UV light irradiation as well as excellent stability in recycling runs with a stable conversion efficiency of 97% or higher over five successive catalytic cycles.

Improved hydrothermal stability of Cu-SAPO-18 by Sm modification in the selective catalytic reduction of NOx with NH3

The Cu-SAPO-18 catalyst is efficient for the selective reduction of NOx with NH3 reaction. Nonetheless, enhancement of the hydrothermal stability of the Cu-SAPO-18 catalyst is needed to satisfy the stringent emission regulations. Sm with partially occupied 4 f orbitals and unoccupied 5d orbitals exhibits excellent physical and chemical properties and is often used as a catalyst promoter in catalytic reactions. In this study, we introduced Sm to Cu-SAPO-18 by a hydrothermal method, and when the added amount of Sm was 0.78 wt%, there was a significant improvement in hydrothermal stability. After Sm introduction, there was a decrease in Si(4Si, 0Al) amount and in unstable Cu(OH)+-Z concentration, thus inhibiting the formation of CuO species during hydrothermal aging. Simultaneously, the Sm replaced the hydrogens of a certain amount of Si–OH–Al bonds, stabilizing the Si–O–Al bonds and alleviating the Cu-SAPO-18 dealumination. Besides, after hydrothermal aging, there was an increase of isolated Cu2+ content in Sm0.78/Cu-SAPO-18, consequently promoting the adsorption of NH3 and NOx species and enhancing the Langmuir–Hinshelwood reaction rate.

Effect of Ce-BTC precursor morphology on CuO/CeO2 catalysts for CO preferential oxidation in H2-rich gas

In this paper, the precursors of the coordination polymer Ce(1,3,5-BTC)(H2O)6 with different morphologies have been successfully prepared via a facile and rapid method, and then the CuO/CeO2 catalysts were obtained by impregnation method to support copper species. The catalysts were characterized by scanning electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, ultraviolet Raman spectrscopy, N2 adsorption-desorption, H2 programmed temperature reduction and X-ray photoelectron spectroscopy, respectively. The results showed that U–CuCeO catalyst has stronger CuO dispersion and higher oxygen vacancy concentration on the surface. The high specific surface area of U–CuCeO catalyst facilitates the highly dispersed CuO species and enhances the interaction between copper and cerium, and improves the catalytic performance compared with the other catalysts. For U–CuCeO catalyst, the CO conversion reached 100% at 120 °C. It also exihibited the broadest complete reaction temperature window.

Oxidation of Methanol and Dichloromethane on TiO2-CeO2-CuO, TiO2-CeO2 and TiO2-CuO@VUKOPOR®A Ceramic Foams.

The application-attractive form of TiO2, CeO2 and CuO-based open-cell foam supported catalysts was designed to investigate their catalytic performance in oxidation of two model volatile organic compounds-methanol and dichloromethane. TiO2-CeO2, TiO2-CuO and TiO2-CeO2-CuO catalysts as thin films were deposited on VUKOPOR®A ceramic foam using a reverse micelles-controlled sol-gel method, dip-coating and calcination. Three prepared catalytic foams were investigated via light-off tests in methanol and dichloromethane oxidation in the temperature range of 45-400 °C and 100-500 °C, respectively, at GHSV of 11, 600 h-1, which fits to semi-pilot/industrial conditions. TiO2-CuO@VUKOPOR®A foam showed the best catalytic activity and CO2 yield in methanol oxidation due to its low weak Lewis acidity, high weak basicity and easily reducible CuO species and proved good catalytic stability within 20 h test. TiO2-CeO2-CuO@VUKOPOR®A foam was the best in dichloromethane oxidation. Despite of its lower catalytic activity compared to TiO2-CeO2@VUKOPOR®A foam, its highly-reducible -O-Cu-Ce-O- active surface sites led to the highest CO2 yield and the highest weak Lewis acidity contributed to the highest HCl yield. This foam also showed the lowest amount of chlorine deposits.

Production of 2-methyl furan, a promising 2nd generation biofuel, by the vapor phase hydrodeoxygenation of biomass-derived furfural over TiO2 supported Cu[sbnd]Ni bimetallic catalysts

This work investigates the vapor phase hydrodeoxygenation (HDO) of FFR to 2-MeF over a series of TiO2-supported mono and bimetallic Cu-Ni catalysts with a fixed Cu content (10 wt%) and varying Ni content (0–20 wt%). The catalysts were synthesized through a simple wet impregnation method, and their properties were studied in depth through an array of analytical techniques such as X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), Scanning Electron Microscopy (SEM), N2-physisorption, Raman spectroscopy, and NH3-temperature programmed desorption (TPD). The catalyst characterizations revealed that the addition of Ni in progressively larger amounts resulted in greater dispersion of Cu species and an increase in the surface area & porosity of the bimetallic catalysts, arising from the strong interactions between NiO and CuO species. Detailed studies were carried out to evaluate the effect of various process parameters such as Ni content, temperature, and contact time on the selectivity of 2-MeF. Ni content of the bimetallic catalysts and temperature played a significant role in product distribution than the contact time. The bimetallic catalyst with the composition 10%Cu-10%Ni was observed to be the optimum, providing a FFR conversion of 100%, and a 2-MeF selectivity of 84.5% at 200 °C, H2/FFR molar ratio = 15, and WHSV = 0.87 gFFR h−1 gcatalayst−1 after 6 h time-on-stream (TOS). During the long-term catalytic activity evaluation, the catalyst exhibited a stable 100% FFR conversion and ∼ 85% selectivity towards 2-MeF over a period of 12 h. Even after a period of 15 h, conversion and selectivity values remained >90% and 70%, respectively.

Role of oxygen species and active phase of CuCeZrOx prepared with bacterial cellulose for toluene catalytic oxidation

The present study investigates the active phases and the role of oxygen species in the toluene oxidation process over CuCeZrOx catalysts prepared with bacterial cellulose (BC), and compares them with nitric acid pickling CuCeZrOx-BC(H) and CeZrOx-BC catalysts. The investigation is carried out using in-situ DRIFT, O2-TPD, H2-TPR, XRD, and TEM techniques. Our findings suggest that dispersed CuO species on the catalyst surface, Cu-Ce-Zr-O, and Ce-Zr-O solid solutions are active for toluene oxidation over CuCeZrOx-BC, with corresponding activities decreasing successively. The in-situ DRIFT results demonstrate that gaseous oxygen facilitates the chemisorption of toluene on active oxygen species, forming benzoyl oxide species and partially oxidizing the absorbed intermediates to benzyl alcohol at room temperature. Furthermore, lattice oxygen is experimentally found to be involved in the deep oxidation of toluene, and the lattice oxygen present in dispersed CuO species dominates the toluene oxidation process over CuCeZrOx-BC.

One‐pot synthesis of CuO/TiO2 nanocomposites for improved photocatalytic hydrogenation of 4‐nitrophenol to 4‐aminophenol under direct sunlight

AbstractThe excellent photocatalytic hydrogenation of 4‐nitrophenol (4‐NP) to 4‐aminophenol (4‐AP) with NaBH4 in the aqueous medium is still a big challenge. Herein, we report a facile one‐pot evaporation‐induced self‐assembly (EISA) method to synthesize a series of CuO/TiO2 nanocomposites. The as‐synthesized CuO/TiO2 photocatalysts exhibit remarkable catalytic activity under direct sunlight in selective hydrogenation of 4‐nitrophenol (4‐NP) to 4‐aminophenol (4‐AP) due to the synergistic interaction of guest copper nanoparticles with host titanium dioxide (TiO2) species. Especially, 5 wt% CuO/TiO2 nanocomposite revealed superior reaction rate constant (k) value (0.306 min−1) when compared to 3 wt% CuO/TiO2 (0.192 min−1) and 7 wt% CuO/TiO2 (0.240 min−1). Moreover, several characterization techniques (XRD, TEM, N2 adsorption–desorption isotherm, DRS, and XPS) were executed to deeply investigate the effect of copper content on the bulk and interfacial properties of the catalysts. The characterization results proved that the superior photocatalytic hydrogenation over 5 wt% CuO/TiO2 catalyst can be ascribed to moderate CuO loading as well as even dispersion of CuO species on the surface of active TiO2 host, which can largely improve the light absorption ability within visible light region. Besides, the 5 wt% CuO/TiO2 catalyst exhibits remarkable recyclability and durability, retaining its superior activity (above 95%) up to several repeating cycles, proving its practical applicability for hydrogenation reactions at domestic and industrial levels.

Stepwise conversion of methane to methanol on Cu and Fe/zeolites prepared in solid state: the effect of zeolite type and activation temperature

AbstractBACKGROUNDGrand efforts have been recently devoted to the development of catalysts based on the excellent performance of Cu‐ and Fe‐dependent enzymes in methanotrophic bacteria for the partial oxidation of methane to methanol under ambient conditions. As a continuation of the study on the stepwise manner for this conversion over zeolite‐based catalysts, in this work, the effects of zeolite topology and activation temperature on the catalytic performance of Cu‐ and Fe‐containing zeolites were investigated.RESULTSCu species exchanged in the medium‐pore zeolites (mordenite, ZSM‐5, and ferrierite) afforded better methanol production, while large‐pore zeolites (zeolite β and zeolite γ) were inappropriate to accommodate active Cu sites. Notably, Cu/silicalite‐1 containing CuO species was also reactive to methane after the activation in O2, yielding a minor methanol amount. Furthermore, the activity of Fe/mordenite towards the methanol in the O2‐assisted procedure was reported for the first time but with a much lower yield as compared to that of Cu/mordenite. The methanol yield over Cu/mordenite increased with the activation temperature because increasing the activation temperature favored the Cu‐exchange degree with a higher priority at the side pockets as compared to the main channels of mordenite, as evidenced from infrared analysis.CONCLUSIONThe selective oxidation of methane to methanol by O2 via a stepwise manner can be obtained over both ion‐exchanged Cu species and well‐dispersed CuO nanoparticles with better activity being recorded for the former. The activity of Cu‐exchanged zeolites was considerably dependent on the zeolite topology and the charge‐balancing position of the Cu2+ cations. © 2023 Society of Chemical Industry (SCI).

Effect of CuO species and oxygen vacancies over CuO/CeO2 catalysts on low-temperature oxidation of ethyl acetate

The catalytic oxidation of ethyl acetate (EA) was studied over CuO/CeO2 catalysts which were prepared by ball milling with different precursors (copper oxide, cerium acetate, cerium dioxide, copper acetate and cerium hydroxide). The CuO/CeO2 catalyst (O-A) prepared with copper oxide and cerium acetate as precursors shows very high catalytic activity that 100% EA conversion is achieved at low temperature of 220 °C. It is found that specific surface area (112.8 m2/g), particle size of CuO (3.5 nm) and proportion of oxygen vacancies are prominent on the O-A catalyst. Oxygen vacancies in CeO2 support are beneficial to enhancing the adsorption and activation of the oxygen. More finely dispersed CuO particles and oxygen vacancies which are derived from the synergistic interaction of Cu–Ce species play an important role in the catalytic oxidation of EA.

Constructing a high concentration CuO/CeO2 interface for complete oxidation of toluene: The fantastic application of spatial confinement strategy

In this paper, CeO2 substrate was prepared by the sol-gel method, further CuO was introduced by adding the copper complexes with chelating agents into the sol-gel precursors of CeO2, in which different chelating agents (β-cyclodextrin, glucose and trimesic acid) were tried. This synthesis method helps the CuO species to disperse very uniformly in the CeO2 substrates. When the amount of copper oxide is up to 33 mol%, the CuO/CeO2 samples can still maintain a highly dispersed state. The CeO2 and CuO/CeO2 samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction of hydrogen (H2-TPR), temperature-programed desorption (O2-TPD), etc. It is found that the CuO/CeO2 catalyst prepared by β-cyclodextrin (βCuO/CeO2) exhibits better catalytic performance owing to the higher dispersion, higher specific surface area, more defects, more active Ce3+ and Cu+ ions, more oxygen vacancies, more surface active oxygen, relatively better low temperature reducibility, and the exposed (110) active facets. In the condition of 1000 × 10−6 toluene in air and WHSV = 60000 mL/(g·h), the T90 for toluene conversion is 227 °C. The reaction mechanism of toluene catalytic oxidation over CeO2 and βCuO/CeO2 is discussed by the study of in-situ DRIFTs. This work affords a simple and efficient method for the synthesis of highly dispersed bimetal oxide catalysts with high contents.

Different morphologies on Cu-Ce/TiO2 catalysts for the selective catalytic reduction of NOx with NH3 and DRIFTS study on sol-gel nanoparticles.

The copper-cerium binary oxide catalysts supported by titanium dioxide with nanosphere core-shell structures, nanotube (TNT) core-shell structures, impregnation (imp) nanoparticles and sol-gel nanoparticles were prepared for NH3-SCR of NOx under medium-low temperature conditions. The effect of different morphologies on the Cu-Ce/TiO2 catalysts was comprehensively studied through physicochemical characterization. The results showed that the sol-gel nanoparticles exhibited 100% NOx reduction efficiency in the temperature range of 180-400 °C. Compared with the other catalysts, the sol-gel nanoparticle catalyst had the highest dispersion and lowest crystallinity, indicating that morphology played an important role in the NH3-SCR of the catalyst. The in situ DRIFTS study on the sol-gel nanoparticle catalyst shows that cerium could promote Cu2+ to produce abundant Lewis acid sites, which would significantly increase the adsorption reaction of ammonia on the catalyst surface, thereby promoting the occurrence of the Eley-Rideal (E-R) mechanism. With the Ce-Ti interaction on the atomic scale, the Ce-O-Ti structure enhanced the redox properties at a medium temperature. In addition, cerium oxide enhances the strong interaction between the catalyst matrix and CuO particles. Therefore, the reducibility of the CuO species was enhanced.

Designing CuO–SiO2 and Cu0–SiO2 Monolithic Ceramics Bearing Hierarchical Porosity Toward Robust and Cycling CO Oxidation Properties

In the general context of environmental air remediation, copper-oxide-based self-standing porous catalysts (MUB-103(x)) and their reduced homologues (Red MUB-103(x)) have been synthesized and studied for the thermoconversion of CO to CO2. Catalytic experiments under dry air conditions reveal that for nonreduced catalysts, increasing the Cu content diminishes the light-off temperature T50 (corresponding to 50% conversion). The catalytic performances exhibited by the CuO phase dispersed in the silica pores of MUB-103(x) samples are the highest reached to date despite the limitations of the experimental conditions used. After reduction with H2, the native Red MUB-103(x) catalysts offer CO conversion efficiencies significantly more increased, leading to a lowering of the T50 values equal to at least 100°C. As such, the CO conversion reaches a T50 value of 160 °C for Red MUB-103(2) with 1.81 wt % Cu; this catalyst displays a specific rate of 8.6 mmolCO gCu–1 s–1 at 175 °C, largely higher than those observed to date. The performances of the Red MUB-103(2) sample were evaluated for CO oxidation under humid conditions with the addition of 5 vol % water vapor in the feed during four cycles, leading to the same efficiency when compared with that under dry experimental conditions, revealing robustness. A drastic increase in the CO conversion temperature was observed for the 4th cycle, i.e., after 8 h under humid conditions. Analyses of the spent Red MUB-103(2) catalyst after four cycles reveal a slight oxidation of copper, leading to Cu2O species. Importantly, after four cycles, the deactivated catalyst was able to partially recover its performance when reactivated through a 2 h reducing treatment under H2 at 400 °C.

Catalytic reduction of organic pollutants, antibacterial and antifungal activities of AgNPs@CuO nanoparticles-loaded mesoporous silica.

In this work, the mesoporous silica MCM-41 was prepared by a hydrothermal method and then modified using silver and copper. The obtained samples were used as antibacterial/antifungal agents and as catalysts for the reduction of the following dyes: Methylene Blue (MB), Congo Red (CR), Methyl Orange (MO), and Orange G (OG). Several parameters affecting the reduction of dyes were investigated and discussed such as the catalyst nature, the initial concentration of the dye, the dye nature, the selectivity of the catalyst in a binary system as well as the catalyst reuse. The catalysts were characterized using XRD, nitrogen sorption measurements, XRF, FTIR, XPS, SEM/EDS, and TEM. XRD, XPS, and TEM analysis clearly showed that the calcination of copper- and silver-modified silica leads to the formation of well-dispersed CuO and AgNPs having sizes between 5 and 10nm. As determined by XRF analysis, the content of silver nanoparticles was higher compared to CuO in all samples. It has been shown that the dye reduction is influenced by the size and the content of nanoparticles as well as by their dispersions. The catalytic activity was shown to be the highest for the Ag-Cu-MCM(0.05) catalyst with a rate constant of 0.114, 0.102, 0.093, and 0.056s-1 for MO, MB, CR, and OG dyes in the single-dye system, respectively. In the binary system containing MB/OG or MB/MO, the catalyst Ag-Cu-MCM(0.05) was more selective toward the MB dye. The reuse of the catalyst for three consecutive cycles showed higher MB conversion in a single system with an increase in reaction time. For antifungal and antibacterial properties, the application of calcined and uncalcined materials toward six different strains showed good results, but uncalcined materials showed the best results due to the synergistic effect between CuO and unreduced species Ag+ which are considered responsible for the antibacterial and antifungal action.

Graphene supported Pd–Cu bimetallic nanoparticles as efficient catalyst for electrooxidation of methanol in alkaline media

Interfacing non-noble metals with noble metal is considered to be the best strategy to balance efficient adsorption and corresponding electrochemical oxidation of fuel relevant for fuel cell reactions. Herein, copper is interfaced with palladium and deposited onto a reduced graphene oxide (RGO) support by employing a simple one-pot chemical reduction using combined advantages offered by l-ascorbic acid and ethylene glycol. Morphological features and elemental composition of Pd–Cu bimetallics on RGO are assessed by transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). The results revealed presence of well-dispersed Pd–Cu particles with an average particle size from 4 to 6 nm on RGO supports (Pd–Cu/RGO). From X-ray photoelectron spectroscopy (XPS) analysis it is understood that Pd–Cu/RGO catalyst owns metallic palladium surface state with a small fraction of CuO or Cu2O species. Methanol electro-oxidation reaction (MOR) is carried out in nitrogen-saturated solution containing KOH (1 M) + CH3OH (1 M) at room temperature on Pd–Cu/RGO, Pd/RGO and Pd/C commercial catalyst. Electrochemical activity descriptors suggest that compared with Pd/RGO and commercial Pd/C (20 wt%), bimetallic Pd–Cu/RGO exhibited 2.1 and 4.0 times higher Jmass, respectively indicating the advantage of interfacing copper with palladium in improving the kinetics of methanol electro-oxidation. The simple synthesis strategy demonstrated here is convenient to extend to fabricate other metallic particles with controlled particle sizes for fuel cell catalytic applications.

Poisoning mechanism of alkali metal on Cu–Fe2O3 catalyst for selective catalytic reduction of NOx with NH3

The poisoning mechanism of Na on Cu–Fe2O3 solid solution catalyst was studied by a series of characterization methods, such as X-ray diffraction (XRD), temperature-programmed reduction by hydrogen (H2-TPR), X-ray photoelectron spectroscopy (XPS), Temperature-programmed desorption (TPD) and in-situ Diffuse Reflectance Infrared Fourier Transform spectroscopy (in-situ DRIFT). The characterization results manifest that one part of Na ions can enter into the crystal lattice of Fe2O3, and replace the original Cu2+ in the crystal lattice of Fe2O3. The replacement results in the electrophilicity of Fe3+ species, thereby restraining the generation and adsorption of NO2, nitrate and nitrite species and reducing Lewis acid sites. In addition, the displaced Cu2+ ions form CuO species and lead to excessive oxidation of NH3 to NOx. In addition, Na2O covers the adsorption sites for NH3, NO2, nitrate and nitrite species. According to in-situ DRIFTS results, the reaction still proceeds through both “fast SCR” and Langmuir-Hinshelwood (L-H) reaction mechanism after sodium poisoning, but the reaction rate reduces obviously. This work reveals the influence and poisoning mechanism of alkali metal on the solid solution catalyst, establishes an alkali metal poisoning model, and offers a new way to develop low-temperature SCR catalysts with high alkali resistance.

Facile synthesis of CuO/Co3O4 nanoribbons with excellent catalytic performance for reduction of organic dyes

In this paper, a facile strategy for the synthesis of composited CuO/Co3O4 nanoribbons is presented based on the supramolecular co-assembly. Large-scale nanosized coordination polymers were obtained under the role of desolvation of the metal ions and ligands, which was used as precursors to construct CuO/Co3O4 nanoribbons. According to the x-ray diffraction (XRD) and inductive coupled plasma emission (ICP) measurements, CuO can be regarded as dispersion phase while Co3O4 can be identified as matrix. What's more, CuO species are homogeneously dispersed in Co3O4 matrix. The catalytic performance of this obtained composited material was measured based on the reduction of organic dye in the presence of NaBH4 as reduction agent, demonstrating that CuO species play the major role in catalytic reaction and the catalytic activity constant was concluded to be 549.02 s−1 g−1. As for Co3O4 species, excellent magnetic property makes it possible for magnetic separation from reaction system. This mass productivity of the CuO/Co3O4 materials with low cost and outstanding catalytic ability have great potential application prospect in water treatment.

Effect of Synthesis Conditions on the Catalytic Performances of CuO/Al2O3 in Microwave-enhanced Fenton-like System

Background: In previous work, we successfully prepared CuO/Al2O3 catalysts and evaluated their catalytic activity, kinetics and degradation mechanism for Fenton-like oxidation of p-nitrophenol (PNP) under microwave irradiation. However, we did not study the effect of important preparation parameters on the activities of catalysts. Objective: (1) The effect of preparation conditions: CuSO4 concentration of the impregnating solution, Al2O3 to CuSO4 solution ratio, type and concentration of precipitant and calcination temperature on the physico-chemical properties and catalytic activity were studied. (2) The catalytic performance of the Fenton-like oxidation reaction of PNP under microwave irradiation was evaluated and correlated with the characterization results. (3) The stability and catalytic mechanism of the catalysts were investigated. objective: (1) The effect of preparation conditions: CuSO4 concentration of impregnating solution, Al2O3 to CuSO4 solution ratio, type and concentration of precipitant and calcination temperature on the physico-chemical properties and catalytic activity were studied. (2) The catalytic performance of the Fenton-like oxidation reaction of PNP under microwave irradiation was evaluated and correlated with the characterization results.(3) The stability and catalytic mechanism of the catalysts were investigated. Methods: The CuO/Al2O3 catalyst was prepared by the impregnation deposition method. The 20 g pretreated Al2O3 particles were immersed in 0.6 mol/L Cu (NO3)2 solution and 0.4 mol/L NaOH solution for 24 h before and after. After cleaning and drying, the samples were calcined in an air muffle furnace for 4 h at a certain temperature to obtain CuO/Al2O3 catalyst. Then the catalyst was characterized and catalyzed. method: The CuO/Al2O3 catalyst was prepared by impregnation deposition method. The 20 g pretreated Al2O3 particles were immersed in 0.6 mol/L Cu (NO3)2 solution and 0.4 mol/L NaOH solution for 24 hours before and after. After cleaning and drying, the samples were calcined in an air muffle furnace for 4 hours at a certain temperature to obtain CuO/Al2O3 catalyst. Then the catalyst was characterized and catalyzed. Results: XRD, BET and FESEM results have demonstrated that the catalyst claimed at 300 and 350 ℃ showed a smaller size, a higher specific surface area and a better distribution of the CuO species than their counterparts prepared at higher calcination temperatures. The CuO/Al2O3 catalyst claimed at 300 and 350 ℃ also showed higher removal efficiencies for PNP than other catalysts prepared at higher calcination temperatures. result: XRD, BET and FESEM results have demonstrated that the catalyst claimed at 300 and 350 ℃ showed a smaller size, a higher specific surface area and a better distribution of the CuO species than their counterparts prepared at higher calcination temperatures. the CuO/Al2O3 catalyst claimed at 300 and 350 ℃ also showed higher removal efficiencies for PNP than other catalysts prepared at higher calcination temperatures. Conclusion: It was found that the catalysts prepared at 350 ℃ as calcination temperature showed higher surface area, smaller CuO particle size, and uniform CuO particle size distribution, and consequently showed better catalytic activities with better stability and reusability. Moreover, the XPS results of the catalysts showed a decrease in the Isat/Ip ratio after microwave enhanced Fenton-like reaction, confirming that CuO species has been reduced to Cu2O to some extent.

Catalase Like-Activity of Metal NPs–Enzyme Biohybrids

In this work, an efficient synthesis of bionanohybrids as artificial metalloenzymes (Cu, Pd, Ag, Mn) based on the application of an enzyme as a scaffold was described. Here we evaluated the effect of changing the metal, pH of the medium, and the amount of enzyme in the synthesis of these artificial metalloenzymes, where changes in the metal species and the size of the nanoparticles occur. These nanozymes were applied in the degradation of hydrogen peroxide for their evaluation as mimetics of catalase activity, the best being the Mn@CALB-H2O, which presented MnO2 nanostructures, with three-fold improved activity compared to Cu2O species, CuNPs@CALB-P, and free catalase.

β-Cyclodextrin promoted the formation of copper phyllosilicate on Cu-SiO2 microspheres catalysts to enhance the low-temperature hydrogenation of dimethyl oxalate

The formation of copper phyllosilicate is critical to the hydrogenation performance of Cu-SiO2 catalysts. A series of Cu-SiO2 microsphere catalysts modified with β-cyclodextrin (β-CD) prepared by the hydrothermal method were fabricated in this work. The results showed that Cu–β-CD complexes were favored to form during the hydrothermal process, which could promote the synthesis of copper phyllosilicate. Meanwhile, the introduction of an appropriate amount of β-CD also promoted the uniform dispersion of CuO species and reduced the size of copper nanoparticles. This could increase the ratio of Cu+/Cu0 after reduction. Thereby the synergistic effect between Cu0 and Cu+ and the stability of the catalyst could be enhanced. Eventually, the modified Cu-SiO2 microsphere catalyst exhibited better catalytic activity for hydrogenation of dimethyl oxalate to ethylene glycol. The dimethyl oxalate conversion of 99.9 % and ethylene glycol selectivity of 97.5 % could be obtained at a low temperature of 453 K. This work has considerable reference value for the subsequent construction of copper species on the catalyst surface.

Regulating the competitive reaction pathway in glycerol conversion to lactic acid/glycolic acid selectively

The numerous parallel reactions in glycerol conversion substantially challenge the effective synthesis of target chemical from oversupplied glycerol. Herein, we intensively studied the control of the complex reaction network in glycerol conversion, and realized the selective production of lactic acid or glycolic acid by integrating the use of different bases with Cu/γ-Al2O3 catalyst. The results indicated that base promoted the oxidation dehydrogenation of glycerol over Cu/γ-Al2O3 catalyst to glyceraldehyde intermediate. Remarkably, base significantly contributed to the control of the competitive reactions in the next glyceraldehyde transformation. DFT calculation revealed that strong base (NaOH) independently promoted the removal of H in C2 of glyceraldehyde, thereby facilitating the dehydration reaction and leading to the selective production of lactic acid. Combing with First-principles calculation, it was revealed that both NaHCO3 and CuO species contributed to increase the electrophilicity of C2 and C3 in glyceraldehyde, thereby directing the conversion of the resultant glyceraldehyde intermediate towards the cleavage of C2-C3 to glycolal. Cu/γ-Al2O3 then separately catalyzed the oxidation of glycolal selectively to glycolic acid. This work might provide a promising approach and give some clues for the valorization of glycerol in widespread applications, thus affording profitable possibilities for the sustainable biodiesel.