Inverse Micelle Method Research Articles

Performance Evaluation of Benzyl Alcohol Oxidation with tert-Butyl Hydroperoxide to Benzaldehyde Using the Response Surface Methodology, Artificial Neural Network, and Adaptive Neuro-Fuzzy Inference System Model.

The adaptive neuro-fuzzy inference system (ANFIS), central composite experimental design (CCD)-response surface methodology (RSM), and artificial neural network (ANN) are used to model the oxidation of benzyl alcohol using the tert-butyl hydroperoxide (TBHP) oxidant to selectively yield benzaldehyde over a mesoporous ceria-zirconia catalyst. Characterization reveals that the produced catalyst has hysteresis loops, a sponge-like structure, and structurally induced reactivity. Three independent variables were taken into consideration while analyzing the ANN, RSM, and ANFIS models: the amount of catalyst (A), reaction temperature (B), and reaction time (C). With the application of optimum conditions, along with a constant (45 mmol) TBHP oxidant amount, (30 mmol) benzyl alcohol amount, and rigorous refluxing of 450 rpm, a maximum optimal benzaldehyde yield of 98.4% was obtained. To examine the acceptability of the models, further sensitivity studies including statistical error functions, analysis of variance (ANOVA) results, and the lack-of-fit test, among others, were employed. The obtained results show that the ANFIS model is the most suited to predicting benzaldehyde yield, followed by RSM. Green chemistry matrix calculations for the reaction reveal lower values of the E-factor (1.57), mass intensity (MI, 2.57), and mass productivity (MP, 38%), which are highly desirable for green and sustainable reactions. Therefore, utilizing a ceria-zirconia catalyst synthesized via the inverse micelle method for the oxidation of benzyl alcohol provides a green and sustainable methodology for the synthesis of benzaldehyde under mild conditions.

Synthesis and Characteristics of Mesoporous Copper Cobalt Oxides Using the Inverse Micelle Method Fabricated for Supercapacitors.

Mesoporous materials have gained considerable attention in the fabrication of supercapacitor electrodes because of their large surface areas and controlled porosities. This study reports the synthesis of mesoporous CuCo2O4 powders using the inverse micelle method. X-ray diffraction, N2 sorption measurement, transmission electron microscopy, and X-ray photoelectron spectroscopy were performed to investigate the properties of the powders. After heat treatment at 250 °C in a vacuum atmosphere, the mesoporous CuCo2O4 powders exhibited a large specific surface area of 116.32 m2 g-1 and a high crystallinity. The electrode fabricated by using the as-prepared mesoporous CuCo2O4 powder exhibited enhanced electrical properties with a maximum specific capacitance of 140 F g-1 and capacitance retention of 91.4% after 3000 continuous charge-discharge cycles. Therefore, the as-prepared mesoporous CuCo2O4 powders hold great potential in the fabrication of supercapacitor electrodes to be used for a wide range of electrochemical applications.

Inverse micelle fabrication of ordered mesoporous manganese oxide and degradation of tetracycline hydrochloride

Ordered mesoporous manganese oxides (MnOx) were synthesized using the modified inverse micelle method. The crystal structure and surface morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The element content and changes in surface valence of catalysts were analyzed by X-ray photoelectron spectroscopy (XPS). The MnOx were used to activate peroxymonosulfate (PMS) to degrade tetracycline hydrochloride (TCH). The catalytic activity of MnOx was enhanced at a calcination temperature of 350 °C (MM-3). The degradation efficiency of TCH in MM-3/PMS system was 87.89% in 180 min. Appropriate dosages of catalyst and PMS improve the degradation efficiency of TCH. This system showed a wide range of pH application (3–9). In the presence of coexisting ions and humic acid, the degradation efficiency of TCH was still above 80%. The results of free radical capture experiment and electron paramagnetic resonance (EPR) test proved that the system activates PMS to produce three types of free radicals: SO4−, OH and 1O2. Therefore, MM-3 is a promising catalyst for the degradation of TCH in practical wastewater treatment.

Synthesis, characterization and non-enzymatic lactate sensing performance investigation of mesoporous copper oxide (CuO) using inverse micelle method

Lactate biosensors based on enzymes have been widely studied. However, they have limitations including low reliability, owing to biological degradation, and high cost. Therefore, transition metal oxides have been extensively investigated for non-enzymatic biosensors owing to their electrochemical catalytic properties and good stability. In this study, we synthesized mesoporous copper oxides (CuOs) by the inverse micelle sol-gel process and fabricated a lactate biosensor using mesoporous CuOs as the electrode material. It is difficult to synthesize mesoporous CuO using the inverse micelle method because Cu has more polymeric hydrolysis species under the same condition than other transition metals. Therefore, we controlled the formation of the polymeric hydrolysis species by setting the precursor and acid concentrations. The primary phase of copper oxalate hydrate was synthesized, and phase transformation to CuO with mesoporosity was achieved through heat treatment. The characteristics of the mesoporous CuO were analyzed by X-ray diffraction, N2 sorption isotherms, and transmission electron microscopy. Mesoporous CuO with a large specific surface area of 166.03 m2/g was successfully synthesized after heat treatment at 250 °C. The non-enzymatic lactate sensing characteristics were assessed using an amperometric response with a three-electrode system. The mesoporous CuO-based biosensor exhibited a maximum sensitivity of 80.33 μA/mM.

New insights on nanostructure of ordered mesoporous Fe[sbnd]Mn bimetal oxides (OMFMs) by a novel inverse micelle method and their superior arsenic sequestration performance: Effect of calcination temperature and role of Fe/Mn oxides

A series of ordered mesoporous FeMn bimetal oxides (OMFMs) were fabricated by using a novel inverse micelle method, and the texture, nanostructure and interface chemistry properties of OMFMs were closely correlated to the calcination temperature. Due to the amorphous regular inner-connected nanostructure and bimetallic synergistic effect, the obtained OMFMs exhibited superior arsenic sequestration performance than pure mesoporous Fe oxides (PMF) and Mn oxides (PMM). The optimum ratio of Fe/Mn and calcination temperature for arsenic removal was 3/1 and 350 °C (OMFM-3), and the maximum As(III) and As(V) adsorption capacities of OMFM-3 were 174.59 and 134.58 mg/g, respectively. Solution pH value negligibly affected the uptake of arsenic (ranged from 3.0 to 7.0), while SiO32−/PO43− ions and humic acid (HA) displayed significant inhibitory effect on arsenic removal by OMFM-3. According to the mechanism of arsenic removal, which simultaneously analyzed the arsenic redox transformation in aqueous phase and on solid phase interface, it was concluded that manganese oxides in OMFM-3 mainly played the role as a remarkable As(III) oxidant in water, whereas iron oxides dominantly acted as an excellent arsenic species adsorbent. Finally, the prominent arsenic sequestration behavior and performance in surface water suggested that OMFM-3 could be a promising and hopeful candidate for arsenic-contaminated (especially As(III)) surface water and groundwater remediation and treatment.

Surface properties vs activity of meso-ZrO2 catalyst in chemoselective Meerwein-Ponndorf-Verley reduction of citral: Effect of calcination temperature

The catalytic transfer-hydrogenation of citral is a vital chemical process in food flavoring, fragrance, and pharmaceutical industries, that necessitates a high degree of purity of the product. However, the heterogeneous catalyst that is mainly selective to α,β-unsaturated alcohol at atmospheric pressure is still lacking. Herein, we prepared a series of mesoporous ZrO2 via a soft-templated inverse micelle method, using different calcination temperatures 250–600 °C. The effect of the calcination temperature on the intrinsic surface properties of the meso-ZrO2 was revealed by analytical techniques such as N2 adsorption-desorption isotherms, pXRD (powder X-ray diffraction), TEM (transmission electron microscope), and CO2/NH3-TPD (temperature-programmed desorption). The meso-ZrO2 catalysts were compared in the Meerwein-Ponndorf-Verley (MPV) reduction of citral at atmospheric pressure. The meso-ZrO2 calcined at 350 °C presented a superior catalytic activity of 71% citral conversion and 100% selectivity to unsaturated alcohol after 10 h, under optimized reaction conditions. The superior activity is ascribed to the enlarged pore volume, increased surface area, and Lewis acidic sites. The calcination temperature has played a significant role in tailoring the surface properties of the meso-ZrO2, which in turn enhanced the catalytic activity. The meso-ZrO2 catalyst is recyclable, easily regenerated with simple calcination. The meso-ZrO2 shows excellent potential for industrial applications.

Synergistic catalysis by Mn promoted ceria for molecular oxygen assisted epoxidation

Mesoporous manganese doped cerium oxide catalysts were prepared by an inverse micelle method with different manganese loadings. These materials exhibited superior activity for epoxidation of alkenes with molecular oxygen. Highest active 10MnCe material showed an activity of 80 % conversion and >99 % selectivity for cyclooctene epoxidation. The fluorite crystal structure which facilitates the high oxygen mobility, low temperature reducibility, homogeneous distribution of manganese on ceria, nanoparticle nature, higher number of oxygen vacancies, low valent states of manganese and cerium, and the ability to generate reactive oxygen species of the manganese doped cerium oxide could be correlated to the high catalytic activity. The reaction followed first order kinetics with a rate constant of 0.31 h−1 at 100 °C, and the activation energy turned out to be 10.5 kJ/mol. The mechanistic study revealed that the reaction proceeds via a unique mechanism which involves in situ generated superoxide and singlet oxygen species.

Mesoporous Crystalline Niobium Oxide with a High Surface Area: A Solid Acid Catalyst for Alkyne Hydration.

A mesoporous crystalline niobium oxide with tunable pore sizes was synthesized via the sol-gel-based inverse micelle method. The material shows a surface area of 127 m2/g, which is the highest surface area reported so far for crystalline niobium oxide synthesized by soft template methods. The material also has a monomodal pore size distribution with an average pore diameter of 5.6 nm. A comprehensive characterization of niobium oxide was performed using powder X-ray diffraction, Brunauer-Emmett-Teller, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, UV-vis, and X-ray photoelectron spectroscopy. The material acts as an environmentally friendly, solid acid catalyst toward hydration of alkynes under with excellent catalytic activity (99% conversion, 99% selectivity, and 4.39 h-1 TOF). Brønsted acid sites present in the catalyst were found to be responsible for the high catalytic activity. The catalyst was reusable up to five cycles without a significant loss of the activity.

Supercapacitor behaviour of manganese dioxide decorated mesoporous silica synthesized by a rapid sol-gel inverse micelle method.

A new type of mesoporous silica (MS) with high surface area and large pore volume has been synthesised by employing a rapid sol-gel based inverse micelle method and electrochemically active metal center, manganese, has been incorporated into it. The MnO2 decorated silica composites are obtained through the wet impregnation technique using KMnO4 followed by their reduction under neutral conditions. The structure and surface area of the samples have been characterised by powder X-ray diffraction (XRD), BET surface area and pore size analysis, transmission and scanning electron microscopy (TEM and FE-SEM), FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS). Electrochemical techniques, i.e. cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS), have been used to evaluate the electrochemical properties of the composites. The resultant composite MS/MnO2-3 with a significantly high surface area (453 m2 g-1) is found to exhibit a superior specific capacitance of 1158.50 F g-1 at a scan rate of 5 mV s-1 which is very close to the theoretical value and retains 87.8% of its capacitance up to 1000 cycles at 1 A g-1 current density. The outstanding electrochemical performance of the composite can be attributed to the high surface area and uniform pore size distribution of the novel silica host which simultaneously increases the electrochemically active centres, promotes electrolyte penetration and enhances electron transport. The simplicity of the synthesis process developed here is interesting for wide-scale production of MnO2-based electro-active materials.

Mesoporous Co3O4 catalysts for VOC elimination: Oxidation of 2-propanol

Mesoporous cobalt oxides were prepared by an inverse micelle method and calcined at different temperatures. These materials exhibited superior activity for oxidation of 2-propanol as the model substrate for VOC elimination. Highest active Co3O4-350 material showed a maximum turnover frequency of 25.8 h−1 at 160 °C at a weight hourly space velocity of 60 L g-1 h−1. The apparent activation energies of mesoporous cobalt oxides ranged from 69.7 kJ/mol to 115.6 kJ/mol. In situ Diffuse Reflectance Infrared spectroscopy (DRIFTS) revealed that the reaction involves formation of carbonyl and carbonate species on the surface of the catalyst before complete oxidation to CO2 and H2O. The activities of the materials were correlated to better low temperature reducibility, large pore volumes, higher Co3+/ Co2+ ratios, and higher number of surface-active oxygen species.

Investigation on Surface Properties of Mn-Doped CdSe Quantum Dots Studied by X-ray Photoelectron Spectroscopy

In this work, we report on the effects of incorporating manganese (Mn) dopant into different sizes of cadmium selenide (CdSe) quantum dots (QDs), which improves the electronic and optical properties of the QDs for multiple applications such as light-emitting diodes, lasers, and biological labels. Furthermore, the greener inverse Micelle method was implemented using organic ligand, which is oleic acid. This binding of the surface enhanced the QDs’ surface trap passivation of Mn-doped CdSe, which then increased the quantity of the output. In addition, the inverse Micelle technique was used successfully to dope Mn into CdSe QDs without the risk of Mn dopants being self-purified as experienced by wurtzite CdSe QDs. Also, we report the X-ray photoelectron spectroscopy (XPS) results and analysis of zinc blended manganese-doped cadmium selenide quantum dots (Mn-doped CdSe QDs), which were synthesized with physical sizes that varied from 3 to 14 nm using the inverse Micelle method. The XPS scans traced the existence of the Se 3d and Cd 3d band of CdSe crystals with a 54.1 and 404.5 eV binding energy. The traced 640.7 eV XPS peak is proof that Mn was integrated into the lattice of CdSe QDs. The binding energy of the QDs was related to the increase in the size of the QDs.

Facile inverse micelle fabrication of magnetic ordered mesoporous iron cerium bimetal oxides with excellent performance for arsenic removal from water

In this study, magnetic ordered mesoporous Fe/Ce bimetal oxides (OMICs) were successfully synthesized via the modified sol-gel-based inverse micelle method. The textural/structure properties, surface chemistry and adsorption behavior of OMICs could be easily adjusted by using the calcination temperature. The sintering of samples would decrease the surface area, while expand the pore and crystallite size, which resulted in the formation of highly ordered inner-connected structure. Compared with pure mesoporous iron oxides (MI) and mesoporous cerium oxides (MC), this ordered mesoporous iron-cerium bimetal oxides (OMIC-3, 450 °C) exhibited remarkable arsenic adsorption performance. The maximum adsorption capacities of As(III) and As(V) for OMIC-3 were 281.34 and 216.72 mg/g, respectively, and both As(III)/As(V) adsorption kinetics were well described by the pseudo-second order. The ionic strength and coexisting ions (except SiO32− and PO43-) did not affect arsenic removal, while humic acid (HA) significantly influenced on the arsenic removal even at a lower concentration. The adsorption mechanism study revealed that both the surface charge and surface M-OH groups of OMIC-3 were played the key roles in arsenic removal. The reusable property suggested that this magnetic OMIC-3 was a promising excellent adsorbent for decontamination of arsenic-polluted (especially As(III)-polluted) wastewater.

Highly sensitive non-enzymatic lactate biosensor driven by porous nanostructured nickel oxide

Lactate sensors are increasingly used for applications in sports and clinical medicine, but currently have several shortcomings including low sensitivity. We demonstrate a highly sensitive and selective non-enzymatic lactate sensor based on porous nickel oxide by sol-gel based inverse micelle method. The porosity and surface area of nickel oxide depending on the calcination temperature (250, 350, and 450 °C) were compared using electron microscopy and a Brunauer-Emmett-Teller (BET) surface area analyzer. Furthermore, we also compared the chemical state of Ni3+ in porous nickel oxides, which is known to be strongly engaged with electrocatalytic lactate detection, with different calcination temperature. The sensing characteristics were assessed using an amperometric response with a three-electrode system. Owing to a relatively large surface area and high Ni3+/Ni2+ ratio, NiO calcined at 250 °C, exhibit maximum sensitivity at 62.35 μA/mM (cm2), and a minimum detection of limit of 27 μM, although, it has large amount of organic residue because of low calcination temperature. In addition to its sensitivity, a porous nickel oxide electrode also displays good selectivity against other interferents such as l-ascorbic acid, uric acid, and dopamine, further supporting its potential as a non-enzymatic lactate sensor.

Aerobic oxidative coupling of amines to imines by mesoporous copper aluminum mixed metal oxides via generation of Reactive Oxygen Species (ROS)

A mesoporous, monomodal copper aluminum mixed metal oxide (MMO) (average pore size 9.63 nm, surface area 140 m2/g) synthesized via a modified inverse micelle method, efficiently catalyzes aerobic oxidative coupling of amines to imines. This material exhibits excellent conversion (>99%) and selectivity (>99%) towards imine synthesis under mild, solvent free, green conditions utilizing atmospheric air as the sole oxidant. Catalytic activity is observed for a diverse range of amine substrates. The aerobic oxidation of amines to imines follows a unique mechanistic pathway which involves Reactive Oxygen Species (ROS).

Catalytic activity of different sizes of Ptn/Co3O4 in the oxidative degradation of Methylene Blue with H2O2

In this work, we demonstrate the catalytic activity and kinetic analyses of generation six poly(amido-amine) hydroxyl-terminated (PAMAM), G6-OH(Ptn) (n = 55, 140, 225) dendrimer-encapsulated nanoparticles (DENs) immobilized onto mesoporous cobalt oxide (Co3O4) for the catalytic oxidation of methylene blue (MB). Ultra-Violet Visible (UV–Vis) spectrophotometry showed the ligand to metal charge transfer (LMCT) band of metal precursor ions coordinated to the tertiary amines of the dendrimer. The size of fully reduced Pt DENs and supported Pt nanoparticles were investigated using High-Resolution Transmission Electron Microscopy (HR-TEM). The mesoporous Co3O4 was synthesized by inverse micelle method, prior to Ptn DENs being supported on the Co3O4 via wet impregnation procedure. The crystallite structure and size of Co3O4 was investigated by powder X-ray diffraction (p-XRD) spectroscopy. Immobilized Ptn/Co3O4 structural analysis was investigated for the pore size and pore volume using N2 sorption techniques. Thermal gravimetric analyses (TGA) also indicated the dendrimer decomposition on the G6-OH(Ptn)/Co3O4 materials to be 550 °C. Hydrogen temperature programmed reduction (H2-TPR) analyses were conducted and the reducibility of the supported cobalt oxide showed only one temperature peak that was ascribed to the reduction of surface lattice oxygens. The experimental kinetic data was analyzed and fitted to the Langmuir-Hinshelwood model using elementary first-order reaction kinetics and the thermodynamic parameters were calculated. Catalyst Pt55/Co3O4 showed stability during the reusability investigation of up to 8 cycles. The G6-OH(Ptn) were immobilized on silica and tested for catalytic oxidation of MB as a control experiment.

Enhanced Catalytic Properties of Molybdenum Promoted Mesoporous Cobalt Oxide: Structure‐Surface‐Dependent Activity for Selective Synthesis of 2‐Substituted Benzimidazoles

AbstractHigh‐valent molybdenum ions were substituted into the cobalt oxide lattice through a one step, sol‐gel method and investigated for selective synthesis of 2‐substituted benzimidazoles. Catalyst synthesis involves surfactant assisted soft templating inverse micelle method, which forms mesopores by interconnected intraparticle voids. Substitutional doping of Mo6+ resulted in materials with modified structural, morphological, surface, and redox properties. The catalytic activity increased with Mo concentration until an optimum amount (3 % Mo incorporation). Modified material shows lattice expansion, increased surface oxygen vacancies, and high surface area, which are responsible for the higher catalytic activity in selective benzimidazole synthesis reaction. A strong correlation between surface properties of the catalyst and the product selectivity was observed and plausible mechanistic and kinetic data are proposed and collected, respectively.

Silicon Quantum Dot-Based Fluorescent Probe: Synthesis Characterization and Recognition of Thiocyanate in Human Blood.

Allylamine-functionalized silicon quantum dots (ASQDs) of high photostability are synthesized by a robust inverse micelle method to use the material as a fluorescent probe for selective recognition of thiocyanate (a biomarker of a smoker and a nonsmoker). The synthesized ASQDs were characterized by absorption, emission, and Fourier transform infrared spectroscopy. Surface morphology is studied by transmission electron microscopy and dynamic light scattering. The synthesized material exhibits desirable fluorescence behavior with a high quantum yield. A selective and accurate (up to 10–10 M) method of sensing of thiocyanate anion is developed based on fluorescence amplification and quenching of ASQDs. The sensing mechanism is investigated and interpreted with a crystal clear mechanistic approach through the modified Stern–Volmer plot. The developed material and the method is applied to recognize the anion in the human blood sample for identification of the degree of smoking. The material deserves high potentiality in the field of bio-medical science.

Excellent product selectivity towards 2-phenyl-acetaldehyde and styrene oxide using manganese oxide and cobalt oxide NPs for the selective oxidation of styrene

MnOx and Co3O4 nanoparticles (NPs) were synthesized using the temperature controlled co-precipitation method and were immobilized on the mesoporous metal oxide supports that were synthesized using the inverse surfactant micelle method. The synthesized catalysts were characterized using TEM, SEM, pXRD, N2-sorption, XPS, and H2-TPR. From TEM the well-dispersed metal oxide NPs were observed and the interaction of the NPs with the support was confirmed with H2-TPR. These metal oxide NPs and immobilized metal oxide NPs were employed in the selective oxidation of styrene using tert-butyl hydrogen peroxide (TBHP) as an oxidant. Higher selectivity towards styrene oxide was obtained using Co3O4 NPs. MnOx NPs gave higher selectivity towards 2-phenyl-acetaldehyde while the immobilized metal oxide NPs gave a mixture of products. The catalytic activities of the compared catalysts followed the following decreasing order of MnOx NPs (646.9 h−1) > Co3O4 NPs (338.1 h−1) > Co-MnO2_350 (54.1 h−1) > Mn-Co3O4_350 (44.1 h−1) ˃ MnO2_350 (35.8 h−1) > Co3O4_350 (21.3 h−1) after 8 h of reaction. The catalytic activities and selectivity profiles under various reaction conditions such as solvent type, catalyst amount, styrene to TBHP ratio and temperature are discussed. The catalytic recyclability of immobilized metal oxide NPs on mesoporous metal oxides showed that they are stable, and the structure of the catalyst was retained.

Effect of alkali and alkaline earth metal dopants on catalytic activity of mesoporous cobalt oxide evaluated using a model reaction

Herein we report the synthesis of mesoporous cobalt oxides in pure (Co3O4) and alkali and alkaline earth metal doped form (Li-, Ca-, Cs-, and Na-, K-, and Mg/Co3O4) via the inverse micelle method. The as-prepared materials were characterized by powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen sorption (BET), hydrogen-temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). Characterization results suggested that the as-synthesized materials are of amorphous and mesoporous nature. Their catalytic activity was investigated using a model reaction, namely the liquid-phase morin oxidation. Results revealed pure cobalt oxide to be the better catalyst compared to its doped counterparts. The stability of Li/Co3O4 material was investigated exemplarily by recycling and reusing the catalysts for as many as four catalytic cycles. Conversion of morin was complete in all runs and no significant metal leaching could be detected by the use of inductively coupled plasma mass spectrometry (ICP-MS).

Catalytic evaluation of mesoporous metal oxides for liquid phase oxidation of styrene

Mesoporous manganese oxide, cobalt oxide, and hybrid Mn-Co oxide were synthesized using an inverse surfactant micelle method. The synthesized materials were monodispersed nanoparticle aggregates with connected and well defined intra-particle voids. An increase in the pore and crystallite size with increase in calcination temperature was observed with TEM, SEM, p-XRD, and N2-sorption. These mesoporous metal oxides were employed in the selective oxidation of styrene using tert-butyl hydrogen peroxide as an oxidant. Higher selectivity towards styrene oxide was achieved using manganese oxide followed by cobalt oxide while the hybrid oxide showed the lowest selectivity towards styrene oxide. The catalytic activities of the compared catalysts were decreasing in the order of Mn-Co_350 (66.6 h−1) > MnO2_350 (47.4 h−1) > Co3O4_350 (35.6 h−1). The catalytic activities and selectivity profiles under various reaction conditions such as solvent type, catalyst amount, styrene to TBHP ratio and temperature are discussed. The catalytic recyclability of metal oxides showed that they are stable, and the structure of the catalyst was retained.