Статті в журналах: "Mixed Oxide Catalyst"

1

Mazaheri, Hoora, Hwai Chyuan Ong, Zeynab Amini, Haji Hassan Masjuki, M. Mofijur, Chia Hung Su, Irfan Anjum Badruddin, and T. M. Yunus Khan. "An Overview of Biodiesel Production via Calcium Oxide Based Catalysts: Current State and Perspective." Energies 14, no. 13 (July 1, 2021): 3950. http://dx.doi.org/10.3390/en14133950.

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Biodiesel is a clean, renewable, liquid fuel that can be used in existing diesel engines without modification as pure or blend. Transesterification (the primary process for biodiesel generation) via heterogeneous catalysis using low-cost waste feedstocks for catalyst synthesis improves the economics of biodiesel production. Heterogeneous catalysts are preferred for the industrial generation of biodiesel due to their robustness and low costs due to the easy separation and relatively higher reusability. Calcium oxides found in abundance in nature, e.g., in seashells and eggshells, are promising candidates for the synthesis of heterogeneous catalysts. However, process improvements are required to design productive calcium oxide-based catalysts at an industrial scale. The current work presents an overview of the biodiesel production advancements using calcium oxide-based catalysts (e.g., pure, supported, and mixed with metal oxides). The review discusses different factors involved in the synthesis of calcium oxide-based catalysts, and the effect of reaction parameters on the biodiesel yield of calcium oxide-based catalysis are studied. Further, the common reactor designs used for the heterogeneous catalysis using calcium oxide-based catalysts are explained. Moreover, the catalytic activity mechanism, challenges and prospects of the application of calcium oxide-based catalysts in biodiesel generation are discussed. The study of calcium oxide-based catalyst should continue to be evaluated for the potential of their application in the commercial sector as they remain the pivotal goal of these studies.

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Mohd Sidek, Haslinda, Irmawati Ramli, Norhazlin Zainuddin, Hossein Abbastabar Ahangar, and Yun Hin Taufiq-Yap. "Physicochemical Properties of MoVTeNb Mixed Oxide Catalysts Synthesized using Different Vanadium Sources." Sains Malaysiana 50, no. 8 (August 31, 2021): 2395–405. http://dx.doi.org/10.17576/jsm-2021-5008-21.

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The use of different vanadium sources in the synthesis of multi-metal MoVTeNb oxide catalysts has been investigated for their effect on the physicochemical properties of catalysts. Metal oxides were synthesized by slurry method assisted with a microwave irradiation. Vanadium pentoxide (V2O5), vanadyl sulphate (VOSO4) and ammonium metavanadate (NH4VO3) were used as the vanadium sources, respectively. X-ray diffraction (XRD) pattern showed the existence of orthorhombic (M1) phases in all catalysts. The catalyst prepared using V2O5 produced the highest formation of the phase. This was further supported by Inductive Couple Plasma-Atomic Emission Spectroscopy (ICP-AES), which showed that the V2O5 catalyst has the highest V: Mo ratio, mainly responsible for the high catalytic activity. Temperature Programmed Reduction in Hydrogen (H2-TPR) showed better reducibility for the catalyst when compared to the others. Temperature Programmed Reaction (TPRn) confirmed that the oxidants active for propane conversion into acrylic acid were originated from the lattice of the catalyst.

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3

Pacultová, Bílková, Klegova, Karásková, Fridrichová, Jirátová, Kiška, et al. "Co-Mn-Al Mixed Oxides Promoted by K for Direct NO Decomposition: Effect of Preparation Parameters." Catalysts 9, no. 7 (July 9, 2019): 593. http://dx.doi.org/10.3390/catal9070593.

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Fundamental research on direct NO decomposition is still needed for the design of a sufficiently active, stable and selective catalyst. Co-based mixed oxides promoted by alkali metals are promising catalysts for direct NO decomposition, but which parameters play the key role in NO decomposition over mixed oxide catalysts? How do applied preparation conditions affect the obtained catalyst’s properties?

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Kustov, Alexander L., Andrey L. Tarasov, Olga P. Tkachenko, Igor V. Mishin, Gennady I. Kapustin, and Leonid M. Kustov. "Ethanol to Acetaldehyde Conversion under Thermal and Microwave Heating of ZnO-CuO-SiO2 Modified with WC Nanoparticles." Molecules 26, no. 7 (March 31, 2021): 1955. http://dx.doi.org/10.3390/molecules26071955.

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The nonoxidative conversion of ethanol to acetaldehyde under thermal and microwave heating was studied on mixed oxide ZnO-CuO-SiO2 catalysts modified with additives of tungsten carbide nanoparticles. The results revealed that the WC-modified catalyst exhibited superior activity and selectivity under microwave heating conditions. It is assumed that when microwave heating is used, hot zones can appear at the contact points of WC nanoparticles and active centers of the mixed oxide ZnO-CuO-SiO2 catalyst, which intensively absorb microwave energy, allowing the more efficient formation of acetaldehyde at moderate temperatures. Thermodynamic calculations of equilibrium concentrations of reagents and products allowed us to identify the optimal conditions for effective acetaldehyde production. The initial catalyst and the catalyst prepared by the coprecipitation of the oxides with the addition of WC were characterized by physicochemical methods (TPR-H2, XRD, DRIFTS of adsorbed CO). The active centers of the oxide catalyst can be Cu+ cations.

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MIKHAILOVSKAYA, T. P., R. KURMAKYZY, D. K. TOLEMISOVA, and K. A. KADIRBEKOV. "OXIDATIVE AMMONOLYSIS OF 4-METHYLPYRIDINE ON OXIDE VANADIUM-TITANIUM-ZIRCONIUM CATALYST MODIFIED BY TIN AND TUNGSTEN OXIDES." Chemical Journal of Kazakhstan 73, no. 1 (March 14, 2021): 196–203. http://dx.doi.org/10.51580/2021-1/2710-1185.21.

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Catalysts based on vanadium pentoxide modified by Ti, Sn, Zr and W oxides were tested in the oxidative ammonolysis of 4-methylpyridine. The role of the main process parameters such as temperature, the ratio of the initial components in the conversion of the methyl group to the nitrile one, and the optimal conditions for the oxidative ammonolysis of 4-methylpyridine were determined. It is determined that the V-Ti-Zr-O-catalyst and the sample containing 9% of tungsten oxide are superior in catalytic activity to the V-Ti-Zr-Sn-O contact. Conditions that ensure a high selectivity for the formation of 4-cyanopyridine were found. The highest yield of the target product (85-86%) was obtained on V-Ti-Zr-W-O at 270 °C, and the yield of 4-cyanopyridine was 87.5% at 310° C on the V-Ti-Zr-Sn-O catalyst. The phase composition and structural changes occurring in modified vanadium oxide catalysts have been studied. It is determined that mixed V-Ti-Zr-Sn-O and V-Ti-Zr-W-O catalysts contain ZrV2O7, the monoclinic modification of ZrO2 (baddeleyite), TiO2 (anatase), SnO2, WO3, and V2O5. In catalysts, it can exist in small amounts as a separate VO2 phase. The V-Ti-Zr-W-O catalyst showed the best catalytic properties. It has highactivity and selectivity towards 4-cyanopyridine.

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6

Ali, Syed Danish, Isma Noreen Javed, Usman Ali Rana, Muhammad Faizan Nazar, Waqas Ahmed, Asifa Junaid, Mahmood Pasha, Rumana Nazir, and Rizwana Nazir. "Novel SrO-CaO Mixed Metal Oxides Catalyst for Ultrasonic-Assisted Transesterification of Jatropha Oil into Biodiesel." Australian Journal of Chemistry 70, no. 3 (2017): 258. http://dx.doi.org/10.1071/ch16236.

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The transesterification of edible and non-edible oils to produce biodiesel is traditionally carried out using homogeneous catalysts (such as NaOH, KOH, and H2SO4). However, these homogenous catalysts often suffer from multiple drawbacks including their corrosive nature and solubility in the reaction mixture, and high costs associated with their recovery. Recent studies have shown that heterogeneous catalysts based on mixed metal oxides have the potential to address the issues associated with conventional homogeneous catalysts, thereby emerging as an efficient class of catalyst materials for biodiesel production. In this study, we describe a heterogeneous strontium oxide/calcium oxide (SrO-CaO) mixed metal oxides catalyst, which displays remarkable efficiency towards the ultrasonic-assisted transesterification of Jatropha oil into biodiesel. The SrO-CaO heterogeneous catalyst was prepared by the wet impregnation method, and the structural morphology of the as-synthesized catalyst was revealed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and nitrogen sorption technique coupled with the Brunauer–Emmett–Teller and Barrett–Joyner–Halenda methods. The X-ray diffraction analysis confirmed the cubic structure of the SrO-CaO catalyst. The catalytic activity of this newly developed catalyst showed a high percentage conversion of triglyceride into the corresponding fatty acid methyl esters (98.19 %) as confirmed by 1H NMR spectroscopy. The chemical composition of the prepared biodiesel by this ultrasonic-assisted transesterification process was determined by the gas chromatography–mass spectrometry. Five major fatty acid methyl esters were identified, of which 9-octadecenoic acid methyl ester was obtained with the highest percentage ~38.22 %. Hence, the study reveals that the SrO-CaO catalyst exhibits high efficiency towards converting Jatropha oil into biodiesel by ultrasonic-assisted transesterification.

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Li, Xue, Zi Yuan Zhou, Li Wei Zhu, and Jian Xin Jiang. "Characterization of Lanthanum Nitrate Modified CaMgZn Mixed Oxide Catalysts for Synthesis of Biodiesel." Advanced Materials Research 581-582 (October 2012): 283–86. http://dx.doi.org/10.4028/www.scientific.net/amr.581-582.283.

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CaMgZn mixed oxide (CMZ) catalysts were modified by addition of lanthanum nitrate, and the use of modified catalysts (CMZL) for biodiesel synthesis were investigated. The conditions of biodiesel production with modified catalysts were optimized. Using optimized conditions, including lanthanum nitrate addition of 3wt.%, catalyst amount of 5wt.%, reaction temperature of 50°C, methanol to oil molar ratio of 15:1 and reaction time of 1h, the glycerol yield of 86.80% catalyzed by CMZL could be attained, which was higher compared with the CMZ catalyzed process of 82.94%. Brunauer–Emmett–Teller (BET), X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) were used to compare the modified CMZL catalyst with the CMZ bare catalyst. The results indicated that the lanthanum modified catalysts (CMZL) have excellent surface property. The modified catalysts could be suitable for commercial application.

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8

Al-Aani, Hussein Mahdi S., Mihaela M. Trandafir, Ioana Fechete, Lucia N. Leonat, Mihaela Badea, Cătălin Negrilă, Ionel Popescu, Mihaela Florea, and Ioan-Cezar Marcu. "Highly Active Transition Metal-Promoted CuCeMgAlO Mixed Oxide Catalysts Obtained from Multicationic LDH Precursors for the Total Oxidation of Methane." Catalysts 10, no. 6 (June 1, 2020): 613. http://dx.doi.org/10.3390/catal10060613.

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To improve the catalytic performance of an active layered double hydroxide (LDH)-derived CuCeMgAlO mixed oxide catalyst in the total oxidation of methane, it was promoted with different transition-metal cations. Thus, two series of multicationic mixed oxides were prepared by the thermal decomposition at 750 °C of their corresponding LDH precursors synthesized by coprecipitation at constant pH of 10 under ambient atmosphere. The first series of catalysts consisted of four M(3)CuCeMgAlO mixed oxides containing 3 at.% M (M = Mn, Fe, Co, Ni), 15 at.% Cu, 10 at.% Ce (at.% with respect to cations), and with Mg/Al atomic ratio fixed to 3. The second series consisted of four Co(x)CuCeMgAlO mixed oxides with x = 1, 3, 6, and 9 at.% Co, while keeping constant the Cu and Ce contents and the Mg/Al atomic ratio. All the mixed oxides were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with X-ray energy dispersion analysis (EDX), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption at −196 °C, temperature-programmed reduction under hydrogen (H2-TPR), and diffuse reflectance UV-VIS spectroscopy (DR UV-VIS), while thermogravimetric and differential thermal analyses (TG-DTG-DTA) together with XRD were used for the LDH precursors. The catalysts were evaluated in the total oxidation of methane, a test reaction for volatile organic compounds (VOC) abatement. Their catalytic performance was explained in correlation with their physicochemical properties and was compared with that of a reference Pd/Al2O3 catalyst. Among the mixed oxides studied, Co(3)CuCeMgAlO was found to be the most active catalyst, with a temperature corresponding to 50% methane conversion (T50) of 438 °C, which was only 19 °C higher than that of a reference Pd/Al2O3 catalyst. On the other hand, this T50 value was ca. 25 °C lower than that observed for the unpromoted CuCeMgAlO system, accounting for the improved performance of the Co-promoted catalyst, which also showed a good stability on stream.

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Liu, Fang, Li Yang, Jie Cheng, Xin Wu, Wenbin Quan, and Kozo Saito. "Low Temperature deNOx Catalytic Activity with C2H4 as a Reductant Using Mixed Metal Fe-Mn Oxides Supported on Activated Carbon." Energies 12, no. 22 (November 14, 2019): 4341. http://dx.doi.org/10.3390/en12224341.

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The selective catalytic reduction of NOx (deNOx) at temperatures less than or at 200 °C was investigated while using C2H4 as the reductant and mixed oxides of Fe and Mn supported on activated carbon; their activity was compared to that of MnOx and FeOx separately supported on activated carbon. The bimetallic oxide compositions maintained high NO conversion of greater than 80–98% for periods that were three times greater than those of the supported monometallic oxides. To examine potential reasons for the significant increases in activity maintenance, and subsequent deactivation, the catalysts were examined by using bulk and surface sensitive analytical techniques before and after catalyst testing. No significant changes in Brunauer-Emmett-Teller (BET) surface areas or porosities were observed between freshly-prepared and tested catalysts whereas segregation of FeOx and MnOx species was readily observed in the mono-oxide catalysts after reaction testing that was not detected in the mixed oxide catalysts. Furthermore, x-ray diffraction and Raman spectroscopy data detected cubic Fe3Mn3O8 in both the freshly-prepared and reaction-tested mixed oxide catalysts that were more crystalline after testing. The presence of this compound, which is known to stabilize multivalent Fe species and to enhance oxygen transfer reactions, may be the reason for the high and relatively stable NO conversion activity, and its increased crystallinity during longer-term testing may also decrease surface availability of the active sites responsible for NO conversion. These results point to a potential of further enhancing catalyst stability and activity for low temperature deNOx that is applicable to advanced SCR processing with lower costs and less deleterious side effects to processing equipment.

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10

Kis, Erne, Matilda Lazic, and Goran Boskovic. "Catalyst component interactions in nickel/alumina catalyst." Acta Periodica Technologica, no. 38 (2007): 61–68. http://dx.doi.org/10.2298/apt0738061k.

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The influence of nickel loading (5; 10; 20 wt% Ni), temperature of heat treatment (400; 700; 1100?C) and way of catalyst preparation on the catalyst component interactions (CCI) in the impregnated, mechanical powder mixed and co-precipitated catalyst was investigated. For sample characterization, low temperature nitrogen adsorption (LTNA) and X-ray diffraction (XRD) were applied. Significant differences were revealed, concerning CCI in dependence of nickel loading, temperature of heat treatment and way of catalyst preparation. The obtained results show that the support metal oxide interactions (SMI) in impregnated and co-precipitated catalysts are more intensive than in the mechanical powder mixed catalyst. The degree and intensity of CCI is expressed by the ratio of real and theoretical surface area of the catalyst. This ratio can be used for a quantitative estimation of CCI and it is generally applicable to all types of heterogeneous catalysts.

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Shah, Parag M., Liam A. Bailey, and Stuart H. Taylor. "The Influence of Cerium to Manganese Ratio and Preparation Method on the Activity of Ceria-Manganese Mixed Metal Oxide Catalysts for VOC Total Oxidation." Catalysts 13, no. 1 (January 4, 2023): 114. http://dx.doi.org/10.3390/catal13010114.

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A set of ceria-manganese mixed metal oxide catalysts with varying Ce:Mn ratios were prepared by coprecipitation using sodium carbonate and were evaluated for the total oxidation of propane and naphthalene. Manganese-rich samples were the most active, with Ce0.25Mn0.75Ox having the highest activity. Catalysts were characterised using X-ray diffraction, Brunauer-Emmett-Teller (BET) surface area, Raman spectroscopy, temperature programmed reduction (TPR), electron microscopy, and X-ray photoelectron spectroscopy (XPS), establishing that the high activity of Ce0.25Mn0.75Ox was due to the formation of phase-separated Mn-substituted ceria and Mn2O3 phases that were not simultaneously present in the other catalysts. The catalyst preparation technique for the most active ratio was investigated using co-precipitation by urea, oxalic acid and citric acid, and mechanochemical grinding. For propane, the mechanochemical and urea catalysts were more active than the carbonate coprecipitated catalyst, due to greater surface area and increased phase separation. This work demonstrates that ceria-manganese mixed metal oxides are more active than the parent oxide, but that preparation technique is also important for controlling activity.

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12

Mikulová, Zuzana, Květuše Jirátová, Jan Klempa, and František Kovanda. "Modification of Co-Mn-Al Mixed Oxide with Promoters and Their Effect on Properties and Activity in VOC Total Oxidation." Collection of Czechoslovak Chemical Communications 73, no. 8-9 (2008): 1000–1014. http://dx.doi.org/10.1135/cccc20081000.

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The activity and selectivity of the Co-Mn-Al mixed oxide catalyst modified with promoters (Pt, Pd, K and La) in total oxidation of volatile organic compounds (toluene and ethanol) were studied. The promoters were introduced at the stage of coprecipitation of a layered double hydroxide (LDH) precursor or impregnation of the mixed oxide obtained by LDH precursor calcination. In total oxidation of toluene, the most active Co-Mn-Al catalysts were those containing low amounts of potassium regardless of the mode of modification, while in total oxidation of ethanol the catalyst impregnated with a higher potassium concentration (3 wt.%) was the most active. Introduction of Pt and Pd in an amount of 0.5 or 0.1 wt.% into the Co-Mn-Al mixed oxide did not improve its catalytic activity. The impregnation method appears to be a more effective mode for preparation of active catalysts than the method using an addition of promoters at the stage of coprecipitation of the LDH precursor. Undesirable reaction intermediate (benzene) was formed when toluene oxidation was carried out over lanthanum- or palladium-containing catalysts. In total oxidation of ethanol, a number of reaction intermediates were produced acetaldehyde being the main one. The catalysts modified at the stage of LDH precursor coprecipitation exhibited a better selectivity (i.e., a lower acetaldehyde formation) than those modified by impregnation. The best results were obtained with the Co-Mn-Al mixed oxide catalyst modified with potassium.

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Samantaray, S. K., and K. M. Parida. "SO42−/TiO2-SiO2 mixed oxide catalyst." Applied Catalysis A: General 211, no. 2 (April 2001): 175–87. http://dx.doi.org/10.1016/s0926-860x(00)00868-1.

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14

Quevedo, Rodolfo, Camilo Perdomo, and Sonia Moreno. "Heterogeneous Catalysts in Pictet-Spengler-Type Reactions." Journal of Chemistry 2013 (2013): 1–5. http://dx.doi.org/10.1155/2013/125302.

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Several solid catalysts were evaluated as an alternative for 1,2,3,4-tetrahydroisoquinoline synthesis by means of the Pictet-Spengler reaction. The reaction catalysed by a mixed oxide (Mg and Al) led to the best yield and good regioselectivity; using an Al-pillared bentonite led to good yields and total regioselectivity. The results revealed no direct relationship between catalyst acidity and yield.

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15

Dang, Kavisha, Navneet Kumar, Vimal Chandra Srivastava, Jinsub Park, and Mu Naushad. "Efficient Propylene Carbonate Synthesis from Urea and Propylene Glycol over Calcium Oxide–Magnesium Oxide Catalysts." Materials 16, no. 2 (January 11, 2023): 735. http://dx.doi.org/10.3390/ma16020735.

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A series of calcium oxide–magnesium oxide (CaO–MgO) catalysts were prepared under the effects of different precipitating agents and using varied Mg/Ca ratios. The physiochemical characteristics of the prepared catalysts were analyzed using XRD, FE-SEM, BET, FTIR, and TG/DTA techniques. Quantification of basic active sites present on the surface of the CaO–MgO catalysts was carried out using the Hammett indicator method. The as-prepared mixed oxide samples were tested for propylene carbonate (PC) synthesis through the alcoholysis of urea with propylene glycol (PG). The effects of the catalyst composition, catalyst dose, reaction temperature, and contact time on the PC yield and selectivity were investigated. The maximum PC yield of 96%, with high PC selectivity of 99% and a urea conversion rate of 96%, was attained at 160 °C using CaO–MgO catalysts prepared using a Mg/Ca ratio of 1 and Na2CO3 as a precipitating agent. The best-performing catalysts also exhibited good reusability without any significant loss in PC selectivity. It is expected that the present study will provide useful information on the suitability of different precipitating agents with respect to the catalytic properties of the oxides of Ca and Mg and their application in the synthesis of organic carbonates.

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16

Jirátová, Květa, Kateřina Pacultová, Jana Balabánová, Kateřina Karásková, Anna Klegová, Tereza Bílková, Věra Jandová, et al. "Precipitated K-Promoted Co–Mn–Al Mixed Oxides for Direct NO Decomposition: Preparation and Properties." Catalysts 9, no. 7 (July 9, 2019): 592. http://dx.doi.org/10.3390/catal9070592.

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Direct decomposition of nitric oxide (NO) proceeds over Co–Mn–Al mixed oxides promoted by potassium. In this study, answers to the following questions have been searched: Do the properties of the K-promoted Co–Mn–Al catalysts prepared by different methods differ from each other? The K-precipitated Co–Mn–Al oxide catalysts were prepared by the precipitation of metal nitrates with a solution of K2CO3/KOH, followed by the washing of the precipitate to different degrees of residual K amounts, and by cthe alcination of the precursors at 500 °C. The properties of the prepared catalysts were compared with those of the best catalyst prepared by the K-impregnation of a wet cake of Co–Mn–Al oxide precursors. The solids were characterized by chemical analysis, DTG, XRD, N2 physisorption, FTIR, temperature programmed reduction (H2-TPR), temperature programmed CO2 desorption (CO2-TPD), X-ray photoelectron spectrometry (XPS), and the species-resolved thermal alkali desorption method (SR-TAD). The washing of the K-precipitated cake resulted in decreasing the K amount in the solid, which affected the basicity, reducibility, and non-linearly catalytic activity in NO decomposition. The highest activity was found at ca 8 wt.% of K, while that of the best K-impregnated wet cake catalyst was at about 2 wt.% of K. The optimization of the cake washing conditions led to a higher catalytic activity.

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17

Kupková, Květa, Pavel Topka, Jana Balabánová, Martin Koštejn, Květuše Jirátová, Jean-Marc Giraudon, Jean-Francois Lamonier, Jaroslav Maixner, and František Kovanda. "Cobalt-Copper Oxide Catalysts for VOC Abatement: Effect of Co:Cu Ratio on Performance in Ethanol Oxidation." Catalysts 13, no. 1 (January 3, 2023): 107. http://dx.doi.org/10.3390/catal13010107.

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The effect of the Co-Cu oxide catalysts composition on their physicochemical properties and performance in the deep oxidation of ethanol was studied. The catalysts with Co:Cu molar ratios of 4:1, 1:1, and 1:4 were obtained by calcination (4 h at 500 °C in air) of the coprecipitated precursors and characterized in detail using powder XRD, Raman spectroscopy, N2 physisorption, H2-TPR, and XPS. The powder XRD and Raman spectroscopy indicated the formation of Co3O4 and CuO mixtures rather than Co-Cu mixed oxides. The CuO promoted the Co3O4 reduction; the Co-Cu catalysts were reduced more easily than the single-component Co and Cu oxides and the main reduction maxima were shifted to lower temperatures with increasing cobalt content in the catalysts. The Co-Cu oxide catalyst with a Co:Cu molar ratio of 4:1 exhibited the best performance in ethanol gas-phase oxidation, showing the lowest T50 (91 °C) and T90(CO2) (159 °C) temperatures needed for 50% ethanol conversion and 90% conversion to CO2, respectively. The excellent catalytic properties of this Co-Cu oxide catalyst were ascribed to the synergistic effect of Co and Cu components. The high activity and selectivity of the Co-Cu catalyst was attributed to the presence of finely dispersed CuO particles on the surface of Co3O4.

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Obalová, Lucie, František Kovanda, Květuše Jirátová, Kateřina Pacultová, and Zdenek Lacný. "Application of Calcined Layered Double Hydroxides as Catalysts for Abatement of N2O Emissions." Collection of Czechoslovak Chemical Communications 73, no. 8-9 (2008): 1045–60. http://dx.doi.org/10.1135/cccc20081045.

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The results of catalytic decomposition of N2O over mixed oxide catalysts obtained by calcination of layered double hydroxides (LDHs) are summarized. Mixed oxides were prepared by thermal treatment (500 °C) of coprecipitated LDH precursors with general chemical composition of MII1-xMIIIx(OH)2(CO3)x/2·yH2O, where MII was Ni, Co, Cu and/or Mg, MIII was Mn, Fe and/or Al, and the MII/MIII molar ratio was adjusted to 2. The influence of chemical composition of the MII-MIII mixed oxide catalysts on their activity and stability in N2O decomposition was examined. The highest N2O conversion was reached over Ni-Al (4:2) and Co-Mn-Al (4:1:1) catalysts. Their suitability for practical application was proved in simulated process stream in the presence of O2, NO, NO2 and H2O. It was found that N2O conversion decreased with increasing amount of oxygen in the feed. The presence of NO in the feed caused a slight decrease in N2O conversion. A strong decrease in the reaction rate was observed over the Ni-Al catalyst in the presence of NO2 while no N2O conversion decrease was observed over the Co-Mn-Al catalyst. Water vapor inhibited the N2O decomposition over all tested catalysts. The obtained kinetic data for N2O decomposition in a simulated process stream over the Co-Mn-Al catalyst were used for a preliminary reactor design. The packed bed volume necessary for N2O emission abatement in a HNO3 production plant was calculated as 35 m3 for waste gas flow rate of 30 000 m3 h-1.

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Pranyoto, Nugroho, Yuni Dewi Susanti, Immanuel Joseph Ondang, Artik Elisa Angkawijaya, Felycia Edi Soetaredjo, Shella Permatasari Santoso, Maria Yuliana, Suryadi Ismadji, and Sandy Budi Hartono. "Facile Synthesis of Silane-Modified Mixed Metal Oxide as Catalyst in Transesterification Processes." Nanomaterials 12, no. 2 (January 13, 2022): 245. http://dx.doi.org/10.3390/nano12020245.

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The fast depletion of fossil fuels has attracted researchers worldwide to explore alternative biofuels, such as biodiesel. In general, the production of biodiesel is carried out via transesterification processes of vegetable oil with the presence of a suitable catalyst. A mixed metal oxide has shown to be a very attractive heterogeneous catalyst with a high performance. Most of the mixed metal oxide is made by using the general wetness impregnation method. A simple route to synthesize silane-modified mixed metal oxide (CaO-CuO/C6) catalysts has been successfully developed. A fluorocarbon surfactant and triblock copolymers (EO)106(PO)70(EO)106 were used to prevent the crystal agglomeration of carbonate salts (CaCO3-CuCO3) as the precursor to form CaO-CuO with a definite size and morphology. The materials show high potency as a catalyst in the transesterification process to produce biodiesel. The calcined co-precipitation product has a high crystallinity form, as confirmed by the XRD analysis. The synthesized catalyst was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). The mechanism of surface modification and the effects of the catalytic activity were also discussed. The biodiesel purity of the final product was analyzed by gas chromatography. The optimum biodiesel yield was 90.17% using the modified mixed metal oxide CaO-CuO/C6.

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Demidova, Yu S., I. L. Simakova, E. V. Suslov, K. P. Volcho, N. F. Salakhutdinov, A. Simakov, and D. Yu Murzin. "Catalytic myrtenol amination over gold, supported on alumina doped with ceria and zirconia." Catalysis for Sustainable Energy 5, no. 1 (December 1, 2018): 49–58. http://dx.doi.org/10.1515/cse-2018-0007.

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Abstract In the current work gold catalysts supported on both commercial oxides and oxides synthesized by the sol-gel method were used for the one-pot alcohol amination of myrtenol. In general, utilization of metal oxides synthesized by the sol-gel method as the gold catalyst support enhanced the knowledge regarding key parameters determining catalytic behavior. Synthesized alumina was characterized by stronger acid sites favoring primary amine accumulation on the catalyst surface, as compared to the commercial oxide. Utilization of mixed metal oxides synthesized by the sol-gel method resulted in the non-additive behavior of different oxides enhancing the catalytic activity. Introduction of ceria into alumina modified the support basicity resulting in more efficient alcohol activation.

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21

Ilieva, Lyuba, Dimitar Dimitrov, Elitsa Kolentsova, Anna Maria Venezia, Daniela Karashanova, Georgi Avdeev, Petya Petrova, Razvan State, and Tatyana Tabakova. "Gold-Based Catalysts for Complete Formaldehyde Oxidation: Insights into the Role of Support Composition." Catalysts 12, no. 7 (June 27, 2022): 705. http://dx.doi.org/10.3390/catal12070705.

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Formaldehyde (HCHO) is recognized as one of the most emitted indoor air pollutants with high detrimental effect on human health. Significant research efforts are focused on HCHO removal to meet emission regulations in an effective and economically profitable way. For over three decades, the unique electronic properties and catalytic abilities of nano-gold catalysts continue to be an attractive research area for the catalytic community. Recently, we reported that mechanochemical mixing is a relevant approach to the preparation of Co-Ce mixed oxides with high activity in complete benzene oxidation. A trend of higher surface defectiveness, in particular, oxygen vacancies, caused by close interaction between cobalt oxide and cerium oxide phases, was observed for a mixed oxide composition of 70 wt.% Co3O4 and 30 wt.% CeO2. These results directed further improvement by promotion with gold and optimization of mixed oxide composition, aiming for the development of an efficient catalyst for room temperature HCHO abatement. Support modification with potassium was studied; however, the K addition caused less enhancement of HCHO oxidation activity than expected. This motivated the preparation of new carrier material. In addition to Co3O4-CeO2 mixed metal oxides with preset ratio, γ-Al2O3 intentionally containing 33% boehmite and shortly named Al2O3-b was used for synthesis. Analysis of the role of support composition in HCHO oxidation was based on the characterization of nano-gold catalysts by textural measurements, XRD, HRTEM, XPS, and TPR techniques. Gold supported on mechanochemically treated Co3O4-CeO2-Al2O3-b (50 wt.% Al2O3-b) exhibited superior activity owing to high Ce3+ and Co3+ surface amounts and the most abundant oxygen containing species with enhanced mobility. This catalyst achieved oxidation to CO2 and H2O by 95% HCHO conversion at room temperature and 100% at 40 °C, thus implying the potential of this composition in developing efficient catalytic materials for indoor air purification.

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22

Demet, Atif Emre, Olinda Gimello, Rossella Arletti, Nathalie Tanchoux, Moulay Tahar Sougrati, Lorenzo Stievano, Françoise Quignard, Gabriele Centi, Siglinda Perathoner, and Francesco Di Renzo. "5-Hydroxymethylfurfural Oxidation to 2,5-Furandicarboxylic Acid on Noble Metal-Free Nanocrystalline Mixed Oxide Catalysts." Catalysts 12, no. 8 (July 25, 2022): 814. http://dx.doi.org/10.3390/catal12080814.

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Noble metal-free catalysts based on earth-abundant and inexpensive mixed oxides are active catalysts of all steps of the reaction cascade leading from 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) using tert-butyl hydroperoxide (TBHP) as oxidation agent. Catalysts covering the whole range of composition in the Cu-Mn and Co-Fe series have been prepared and characterised. The nature and composition of the catalyst strongly affect conversion and selectivity. The distribution of products indicates that radical-type oxygen species, deriving from the activation of TBHP, play a determining role in the reaction. The early steps of reaction mainly follow the pattern expected for heterogeneous Fenton catalysts. Mixed oxide catalysts are the most effective in further oxidation steps, leading to the formation of FDCA, both in the Cu-Mn and Co-Fe systems. This behaviour can be related to the distribution of charge in the mixed oxides, suggesting a possible implication of the lattice oxygen in the last reaction steps. The results provide indications on how to optimize the reaction and minimize the formation of byproducts (humins and oligomers).

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23

Al-Hazmi, Mohammed H., Taiwo Odedairo, Adel S. Al-Dossari, and YongMan Choi. "Revisiting Oxidative Dehydrogenation of Ethane by W Doping into MoVMn Mixed Oxides at Low Temperature." Advances in Physical Chemistry 2015 (January 27, 2015): 1–9. http://dx.doi.org/10.1155/2015/102583.

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The catalytic performance of MoVMnW mixed oxides was investigated in the oxidative dehydrogenation of ethane at three different reaction temperatures (235, 255, and 275°C) using oxygen as an oxidant. The catalysts were characterized by using X-ray diffraction, temperature-programmed reduction, and scanning electron microscopy. The MoVMnW mixed oxide catalyst showed the 70–90% of ethylene selectivity at the reaction temperatures. However, a significant decrease in the selectivity of ethylene was observed by increasing the reaction temperature from 235°C to 275°C.

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24

Zhi, Ke Duan, Quan Sheng Liu, Jing Li, Run Xia He, and Fang Wu. "The Effect of the Precipitator Concentration on the Activity of Mesoporous Cu-Ce-La Mixed Oxide Catalyst for Water-Gas Shift Catalyst." Applied Mechanics and Materials 291-294 (February 2013): 597–601. http://dx.doi.org/10.4028/www.scientific.net/amm.291-294.597.

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Cu-Ce-La mixed oxide catalysts were prepared by co-precipitation methods with a series of precipitator concentration and characterized using X-ray diffraction, BET, TPR, and catalytic reaction for the water-gas shift. The Cu-Ce-La mixed oxide prepared by 4.0 mol/L NaOH concentration presented the highest activity and thermal stability. the precipitator concentration influence the activity of catalyst via the stability of crystal structure and mesoporous structure. La3+or Ce4+substituted copper ion of CeO2framework during reaction process. The concentration of precipitator can control pore diameter of catalyst in synthetical process. The raising of precipitator concentration, from 0.5 to 2.0 mol/L, lead to enhancing of synergistic effects between CuO and CeO2.

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25

Dieterle, M., G. Mestl, J. Jäger, Y. Uchida, H. Hibst, and R. Schlögl. "Mixed molybdenum oxide based partial oxidation catalyst." Journal of Molecular Catalysis A: Chemical 174, no. 1-2 (October 2001): 169–85. http://dx.doi.org/10.1016/s1381-1169(01)00074-7.

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26

Ma, Yubo, Zhixian Gao, and Wumanjiang Eli. "Hydroformylation of Dicyclopentadiene over Rh Catalysts Supported on Fe2O3, Co3O4 and Fe2O3–Co3O4 Mixed Oxide." Progress in Reaction Kinetics and Mechanism 42, no. 1 (February 2017): 8–13. http://dx.doi.org/10.3184/146867817x14806858831947.

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Rh catalysts supported on Fe2O3, Co3O4 and Fe2O3–Co3O4 mixed oxide were prepared by the co-precipitation method. The effect of the support on the performance of the Rh catalysts for the hydroformylation of dicyclopentadiene was investigated using X-ray photoelectron spectroscopy, H2-temperature-programmed reduction, H2-temperature-programmed desorption and Brunauer–Emmett–Teller analysis techniques. The results indicated that the Fe2O3–Co3O4 supported catalyst had a higher dispersion of Rh and thus more Rh+ sites. As a result, the Fe2O3–Co3O4 supported Rh catalyst exhibited higher activity compared with counterparts supported on Fe2O3 and Co3O4.

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27

Al-ghamdi, Mohammed, and Hossein Bayahia. "Zinc-Chromium oxide catalyst for gas-phase ketonisation of pentanoic acid." Mediterranean Journal of Chemistry 6, no. 2 (November 13, 2016): 1–6. http://dx.doi.org/10.13171/mjc62/01611080121-bayahia.

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Oxides of Zinc and Chromium mixed catalyst with different atomic ratios of Zinc and Chromium were tested in the ketonisation of pentanoic acid in the gas phase. These catalysts were active to form 5-nonanone, at 300 – 400 oC and ambient pressure. It was found that Zn-Cr with an atomic ratio (10:1) gave the best catalytic performance in comparison with other oxides with higher or lower atomic ratio of Zn and Cr mixed oxides, ZnO and Cr2O3. In this test, Zn-Cr (10:1) gave 82% of selectivity for 5-nonanone as the main product at 86% of conversion of the acid at 350oC. The catalyst showed stable performance at the best selected conditions with a small decrease in acid conversion. For catalyst characterization, BET surface area and porosity technique, X-ray diffraction and DRIFTS of pyridine adsorption were used.

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28

Stoyanova, Maria, and Stoyanka Christoskova. "Novel Ni−Fe-oxide systems for catalytic oxidation of cyanide in an aqueous phase." Open Chemistry 3, no. 2 (June 1, 2005): 295–310. http://dx.doi.org/10.2478/bf02475998.

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AbstractCatalytic activity of mixed Ni−Fe oxide systems with respect to air oxidation of aqueous cyanide solution at 308 K was investigated. The catalysts employed were prepared by an oxidation-precipitation method at room temperature and were characterized by powder X-ray diffraction (XRD), Mössbauer spectroscopy, and chemical analysis. The cyanide oxidation rate was found to be dependent on the catalyst's calcination temperature, pH of the medium, and catalyst loading. Results revealed that the catalyst calcined at 120°C is the most active where up to 90% of free cyanide (4 mM) was removed after oxidation for 30 minutes in the presence of 2.5 g/L catalyst at pH 9.5. The cyanide conversion becomes less favorable as the pH of the solution increases (with other constant parameters). The selectivity data showed that carbon dioxide is the main oxidation product, regardless of pH of the solution.

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29

Kerenkan, Amir Enferadi, Aimé Serge Ello, Bousselham Echchahed та Trong-On Do. "Synthesis of Mesoporous Tungsten Oxide/γ-Alumina and Surfactant-Capped Tungsten Oxide Nanoparticles and Their Catalytic Activities in Oxidative Cleavage of Oleic Acid". International Journal of Chemical Reactor Engineering 14, № 4 (1 серпня 2016): 899–907. http://dx.doi.org/10.1515/ijcre-2015-0101.

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Abstract Unsaturated fatty acids can be converted into mono and dicarboxylic acids, which are applicably valuable materials, through oxidative cleavage reaction in the presence of a highly efficient catalyst/oxidant system. In this work, two types of advanced heterogeneous catalysts have been developed; (i) high surface area mesoporous tungsten oxide/γ-alumina mixed metal oxide, and (ii) surfactant-capped tungsten oxide nanoparticles. Various technique including N2 adsorption/desorption isotherms, XRD, SEM, EDS, TGA and catalytic test were used to monitor the physicochemical and catalytic properties of these materials. The characterization results revealed that type (i) materials exhibit high surface area and narrow particle size distribution, and the used surfactant could quantitatively enough cap the surface of type (ii) materials. The catalytic activities of these materials in the oxidative cleavage of oleic acid with H2O2 as oxidant were investigated. GC-MS was used to determine the produced amounts of desired products, azelaic and pelargonic acids. The catalytic test results showed more than 90 % conversion for type (ii) catalyst in 5 h reaction at 120 °C with acceptable production yields for azelaic and pelargonic acids. The significantly higher activity of this catalyst compared to type (i) arises from the interesting surface properties of tungsten oxides nanoparticles, which make them able to exploit the good features of homogeneous and heterogeneous catalysts.

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30

Alharbi, Khadijah H., Ali Alsalme, Ahmed Bader A. Aloumi, and Mohammed Rafiq H. Siddiqui. "Selective Catalytic Oxidation of Toluene to Benzaldehyde: Effect of Aging Time and Calcination Temperature Using CuxZnyO Mixed Metal Oxide Nanoparticles." Catalysts 11, no. 3 (March 9, 2021): 354. http://dx.doi.org/10.3390/catal11030354.

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Oxidation is an important organic transformation, and several catalysts have been reported for this conversion. In this study, we report the synthesis of mixed metal oxide CuxZnyO, which is prepared by a coprecipitation method by varying the molar ratio of Cu and Zn in the catalytic system. The prepared mixed metal oxide CuxZnyO was evaluated for catalytic performance for toluene oxidation. Various parameters of the catalytic evaluation were studied in order to ascertain the optimum condition for the best catalytic performance. The results indicate that aging time, calcination temperature, reaction temperature, and feed rate influence catalytic performance. It was found that the catalyst interfaces apparently enhanced catalytic activity for toluene oxidation. The XRD diffractograms reveal the crystalline nature of the mixed metal oxide formed and also confirm the coexistence of hexagonal and monoclinic crystalline phases. The catalyst prepared by aging for 4 h and calcined at 450 °C was found to be the best for the conversion of toluene to benzaldehyde while the reactor temperature was maintained at 250 °C with toluene fed into the reactor at 0.01 mL/min. The catalyst was active for about 13 h.

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Mohamad, Mardhiah, and Norzita Ngadi. "Effect of TiO₂ Mixed CaO Catalyst in Palm Oil Transesterification." Applied Mechanics and Materials 695 (November 2014): 319–22. http://dx.doi.org/10.4028/www.scientific.net/amm.695.319.

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Biodiesel is a promising alternative fuel. In this study, production of biodiesel from cooking oil (CO) was carried out via transesterification method. Heterogeneous catalyst, calcium oxide-titanium dioxide (CaO-TiO2) was selected as the best catalyst. The effects of CaO-TiO2 catalyst on catalyst amount and calcination temperature of catalyst towards the percentage conversion of oil to biodiesel were investigated. The catalysts were analyzed using Brunauer, Emmett and Teller (BET) test method. The results obtained showed that 76.67 % of oil was successfully converted into biodiesel using 800°C calcined CaO-TiO2 catalyst. This indicates that the CaO-TiO2 has potential as a future heterogeneous catalyst for biodiesel production. Catalyst dosage of 0.5 w/w% with molar ratio oil to methanol is 3:5, stirring speed of 250 rpm and temperature of 65°C in 1 hour reaction time are the best condition for the conversion of oil to biodiesel. It was found out that, calcination temperature of catalyst and catalyst amount gave significant effect on the conversion of oil.

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32

Kumari, Sudesh, Babajide Patrick Ajayi, Bijandra Kumar, Jacek B. Jasinski, Mahendra K. Sunkara та Joshua M. Spurgeon. "A low-noble-metal W1−xIrxO3−δ water oxidation electrocatalyst for acidic media via rapid plasma synthesis". Energy & Environmental Science 10, № 11 (2017): 2432–40. http://dx.doi.org/10.1039/c7ee02626a.

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Rapid plasma oxidation of a mixed-metal oxide catalyst with Ir metal content as low as 1% showed promising water oxidation catalysis in acid with significantly improved performance over an analogous thermally oxidized material.

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33

Chottiratanachote, Atikhun, Manaswee Suttipong, Umer Rashid, Vudhichai Parasuk, Junko Nomura Kondo, Toshiyuki Yokoi, Ali Alsalme, and Chawalit Ngamcharussrivichai. "Selective Synthesis of Renewable Bio-Jet Fuel Precursors from Furfural and 2-Butanone via Heterogeneously Catalyzed Aldol Condensation." Catalysts 13, no. 2 (January 20, 2023): 242. http://dx.doi.org/10.3390/catal13020242.

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This study aims to synthesize α,β-unsaturated carbonyl compounds with branched structures via aldol condensation of furfural and 2-butanone using magnesium–aluminum (MgAl) mixed oxides as heterogeneous acid–base catalysts. Regarding the molecular structure of 2-butanone, there are two possible enolate ions generated by subtracting the α-hydrogen atoms at the methyl or methylene groups of 2-butanone. The branched-chain C9 products, derived from the methylene enolate ion, can be applied as bio-jet fuel precursors. The most suitable catalyst, contributing the highest furfural conversion (63%) and selectivity of the branched-chain C9 products (77%), is LDO3, the mixed oxides with 3:1 Mg:Al atomic ratio, with a high surface area and a large number of medium basic sites. The suitable reaction conditions to produce the branched-chain C9 ketones are 1:5 furfural:2-butanone molar ratio, 5 wt.% catalyst loading, 120 °C reaction temperature, and 8 h reaction time. Additionally, this study investigates the adsorption of 2-butanone onto a mixed oxide using in situ Fourier transform infrared spectroscopy; the results of which suggest that the methylene enolate of 2-butanone is the likely dominant surface intermediate at elevated temperatures. Accordingly, the calculation, based on density functional theory, indicates that the methylene enolate ion of 2-butanone is the kinetically favorable intermediate on an MgO(100) as a model oxide surface.

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Jirátová, Květa, Kateřina Pacultová, Kateřina Karásková, Jana Balabánová, Martin Koštejn, and Lucie Obalová. "Direct Decomposition of NO over Co-Mn-Al Mixed Oxides: Effect of Ce and/or K Promoters." Catalysts 10, no. 7 (July 20, 2020): 808. http://dx.doi.org/10.3390/catal10070808.

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Co-Mn-Al mixed oxides promoted by potassium are known as active catalysts for the direct decomposition of nitric oxide (NO). In this study, the answer to the following question has been considered: does the presence of cerium in K-promoted Co-Mn-Al catalysts substantially affect the physical-chemical properties, activity, and stability in direct NO decomposition? The Co-Mn-Al, Co-Mn-Al-Ce, and Co-Mn-Al-Ce-K mixed oxide catalysts were prepared by the precipitation of corresponding metal nitrates with a solution of Na2CO3/NaOH, followed by the washing of the precipitate and calcination. Two other catalysts were prepared by impregnation of the Ce-containing catalysts with Co and Co+K nitrates. After calcination, the solids were characterized by chemical analysis, XRD, N2 physisorption, FTIR, temperature-programmed reduction, CO2 and O2 desorption (H2-TPR, CO2-TPD, O2-TPD), and X-ray photoelectron spectrometry (XPS). Cerium and especially potassium occurring in the catalysts affected the basicity, reducibility, and surface concentration of active components. Adding cerium itself did not contribute to the increase in catalytic activity, whereas the addition of cerium and potassium did. Catalytic activity in direct NO decomposition depended on combinations of both reducibility and the amount of stronger basic sites determined in the catalysts. Therefore, the increase in cobalt concentration itself in the Co-Mn-Al mixed oxide catalyst does not determine the achievement of high catalytic activity in direct NO decomposition.

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Jirátová, Květa, Martin Čada, Iryna Naiko, Alina Ostapenko, Jana Balabánová, Martin Koštejn, Jaroslav Maixner, et al. "Plasma Jet Sputtering as an Efficient Method for the Deposition of Nickel and Cobalt Mixed Oxides on Stainless-Steel Meshes: Application to VOC Oxidation." Catalysts 13, no. 1 (December 30, 2022): 79. http://dx.doi.org/10.3390/catal13010079.

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Hollow cathode plasma sputtering is an advantageous method of preparing catalysts in the form of thin oxide films on supports. Such catalysts are particularly suitable for processes such as catalytic total oxidation of volatile organic compounds (VOCs), representing an economically feasible and environmentally friendly method of VOC abatement. Catalysts with Ni:Co molar ratios of 1:4, 1:1, and 4:1 were prepared on stainless-steel meshes and compared with single-component Ni and Co oxide catalysts. The properties of the catalysts were characterized by EDX, SEM, powder XRD, temperature-programmed reduction (H2-TPR), Raman spectroscopy, and XPS. Powder XRD revealed the formation of various crystalline phases that were dependent on molar the Ni:Co ratio. NiO and Co3O4 were identified in the single-component Ni and Co oxide catalysts, whereas Ni-Co mixed oxides with a spinel structure, together with NiO, were found in the catalysts containing both Ni and Co. Raman spectra of the catalysts prepared at high working pressures showed a slightly lower intensity of bands, indicating the presence of smaller oxide particles. The TPR profiles confirmed the improved reducibility of the Ni-Co oxide catalysts compared to the single-component Ni and Co catalysts. Catalytic activity was investigated in the deep oxidation of ethanol and toluene, which were used as model volatile organic compounds. In ethanol oxidation, the activity of sputtered catalysts was up to 16 times higher than that of the commercial Cu-Mn oxide catalyst EnviCat® VOC-1544. The main benefits of the sputtered catalysts are the much lower content of Ni and Co oxides and a negligible effect of internal diffusion. Moreover, the process of plasma jet sputtering can be easily implemented on a large scale.

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Borovinskaya, Ekaterina S., Sebastian Trebbin, Felix Alscher, and Cornelia Breitkopf. "Synthesis, Modification, and Characterization of CuO/ZnO/ZrO2 Mixed Metal Oxide Catalysts for CO2/H2 Conversion." Catalysts 9, no. 12 (December 6, 2019): 1037. http://dx.doi.org/10.3390/catal9121037.

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CuO/ZnO/ZrO2 catalyst systems were synthesized in different ways and comprehensively characterized in order to study synthesis-to-property relations. A series of catalyst samples was prepared by coprecipitation, one-pot synthesis, and wet impregnation. The coprecipitation of multicomponent precipitates is usually a preliminary stage for preparation of mixed oxide catalysts. Cetyltrimethylammonium bromide (CTAB) was used in the surfactant-supported coprecipitation to improve the structural or textural characteristics of the catalytic samples. In the one-pot synthesis, all necessary components are simultaneously converted by evaporation from solutions into solids. During the wet impregnation, zirconium hydroxide is loaded with metal salts. After thermal treatment, all samples formed pure metal oxide forms, which was confirmed by XRD. The specific surface area of the investigated samples and their porous texture were determined by nitrogen adsorption. The reducibility of metal oxides and the kind of CuO phase was characterized by temperature-programmed reduction (TPR), and the surface acid properties by temperature-programmed ammonia desorption (TPAD). The CuO/ZnO/ZrO2 sample with the highest amount of strong acid sites is characterized by the formation of large CuO particles combined with the worst reducibility so that potentially catalytic active Cu/CuO pairs can be formed. One catalyst system was further characterized by in situ diffuse reflection Fourier transform infrared spectroscopy (DRIFTS) to identify surface intermediate species, which may occur during the conversion of CO2/H2 to methanol.

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Liu, Rong, Yi Fan Xu, Fei Ye, Ling Chen Ji, Hao Guan, and Ming Yang. "Low-Temperature Selective Catalytic Reduction with NH₃ over MnO_x-CeO₂ Catalysts Supported on Nano Tetragonal Zirconia." Materials Science Forum 852 (April 2016): 293–99. http://dx.doi.org/10.4028/www.scientific.net/msf.852.293.

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The MnOx-CeO2/t-ZrO2 catalyst was prepared by impregnation with nano t-ZrO2 as the support. The influence of active component and reaction temperature on denitration performance of catalyst was investigated. The results showed that denitration efficiency improved as active component increased and reaction temperature rose. The denitration efficiency of 2.5% MnOx-CeO2/t-ZrO2 at 100°C was 68.1% while 15% MnOx-CeO2/t-ZrO2 was 97.4%. The results of XRD, BET and H2-TPR showed that surface structure of loaded catalyst was good for oxidation-reduction and denigration. NH3-TPD test demonstrated that NH3 was mainly adsorbed at Lewis acid sites on the surface of catalysts and became coordination NH3. Intermediate product NH2NO generated from reactions between coordination NH3 and NO which finally changed into N2 and H2O.NOx are potentially harmful to humans as a kind of primary pollutants. And NOx are the main cause of many environment problems, such as acid rain, surface ozone pollution and Particulate Matter 2.5[1]. The emission of NOx was 2337.8 tons in China in 2011 and that was 2275.4 tons[2]. The environmental situation is grim although the emission of NOx had begun decreasing. Emission standard of air pollutants for thermal power plants which came into effect on January 1, 2012 require the emission concentration of NOx under 100mg·m-3. The task is arduous.Selective catalytic reduction (SCR) of NOx with NH3 is the most promising method to remove NOx and catalysts with high activity play a decisive part in low temperature SCR technology. Many researches about metal oxide as SCR catalyst support have been reported recently, such as TiO2[3], Al2O3[4], activated carbon[5] and molecular sieve[6]. Zirconium oxide has attracted considerable attention recently as a catalyst support because of its special characteristics. Takahashi et al.[7] investigated the influence of the various compositions of TiO2 and ZrO2 on the NOx removal ability over a sulfur-treated NSR catalyst and came to a conclusion that ZrO2 support suppressed the solid phase reaction with potassium. Reddy et al.[8, 9] investigated structural characteristics of nanosized ceria-silica, ceria-titania, and ceria-zirconia mixed oxide catalysts and found these mixed oxides exhibit better redox properties than pure CeO2. YAN Zhi-yong et al.[10] reported that the existence of ZrO2 in catalysts can raise its specific area and enhance the dispersion of CeO2 on catalysts which results in high activity of the catalysts. CeO2/TiO2-ZrO2 catalyst has strong tolerance to water vapor and sulfur dioxide.It is well known that ZrO2 exists mainly in three polymorphs with monoclinic (m-ZrO2), tetragonal (t-ZrO2) and (c-ZrO2) cubic structures[11]. ZrO2 polymorphs have different amphoteric character of its surface hydroxyl groups. The crystalline phase of ZrO2 has a great effect on the structure, activity and selectivity of catalysts. Therefore, it is valuable to investigate the effects of nanocrystalline zirconia polymorphs on catalytic properties of MnOx-CeO2/t-ZrO2 Catalysts which few researchers have concerned about. In this study, we try to investigate catalytic activity and microstructure of SCR catalysts with manganese oxide and cerium oxide supported on t-ZrO2.

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Malik, Muhammad Irfan, Nicolas Abatzoglou, and Inès Esma Achouri. "Methanol to Formaldehyde: An Overview of Surface Studies and Performance of an Iron Molybdate Catalyst." Catalysts 11, no. 8 (July 24, 2021): 893. http://dx.doi.org/10.3390/catal11080893.

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Formaldehyde is a primary chemical in the manufacturing of various consumer products. It is synthesized via partial oxidation of methanol using a mixed oxide iron molybdate catalyst (Fe2(MoO4)3–MoO3). This is one of the standard energy-efficient processes. The mixed oxide iron molybdate catalyst is an attractive commercial catalyst for converting methanol to formaldehyde. However, a detailed phase analysis of each oxide phase and a complete understanding of the catalyst formulation and deactivation studies is required. It is crucial to correctly formulate each oxide phase and influence the synthesis methods precisely. A better tradeoff between support and catalyst and oxygen revival on the catalyst surface is vital to enhance the catalyst’s selectivity, stability, and lifetime. This review presents recent advances on iron molybdate’s catalytic behaviour for formaldehyde production—a deep recognition of the catalyst and its critical role in the processes are highlighted. Finally, the conclusion and prospects are presented at the end.

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39

Samotaev, Nikolay, and Alexey Vasiliev. "Mixed Cerium/Zirconium Oxide as a Material for Carbon Monoxide Thermocatalytic Gas Sensor." Proceedings 2, no. 13 (December 4, 2018): 841. http://dx.doi.org/10.3390/proceedings2130841.

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Анотація:

The perspective catalysts usable for the fabrication of thermocatalytic gas sensors were studied. The analysis of CO oxidation kinetics by Pd decorated Al2O3, ZSM-5, SnO2, CeO2/ZrO2 and some other carriers of catalysts showed that the application of these catalysts leads to the ambiguity of sensor response (light-off effect). It was demonstrated that a catalyst based on CeO2/ZrO2 carrier could be used for the fabrication of sensors characterized by the univocal correspondence between CO concentration and sensor response. The developed model of the CO oxidation on all Pd catalysts with inert carrier enabled the description of the CO oxidation using a single value of activation energy.

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40

Kishore, Ramineni, Samudrala Shanthi Priya, Medak Sudhakar, Boosa Venu, Akula Venugopal, Jagjit Yadav, and Mannepalli Lakshmi Kantam. "Synthesis of fluorenones by using Pd(ii)/Mg–La mixed oxide catalyst." Catalysis Science & Technology 5, no. 6 (2015): 3363–67. http://dx.doi.org/10.1039/c4cy01732c.

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41

Srakeaw, Veeranuch, Siriporn Yodjai, and Unalome Wetwatana. "Catalytic Pyrolysis of LDPE Plastic Wastes over Mortar Cement Catalyst." Advanced Materials Research 931-932 (May 2014): 47–51. http://dx.doi.org/10.4028/www.scientific.net/amr.931-932.47.

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A CaO based catalyst synthesized from mortar previously used in construction was chosen for pyrolysis of LDPE plastic waste. The samples were calcined at temperatures of 500 and 800 °C for comparison purpose. After calcination, two mixed oxides were obtained, denoted as catalyst A and B. The chemical composition of the metal oxide catalysts and the liquid products of the pyrolysis were characterized by X-ray Fluorescence (XRF) and Simulated Distillation - Gas Chromatography (SD-GC), respectively. The XRF analysis indicated that the catalyst, reformed from the mortar cement, consisted of CaO, silica (silicon dioxide, SiO2) and alumina (aluminium (III) oxide, Al2O3) as the main constituents, though, the composition of each compound differed because of the influence of calcination temperature. Catalyst A had 41.96% of CaO, 4.27% of Al2O3 and 30.82% of SiO2 when the catalyst B had 37.04% of CaO, 2.38% of Al2O3 and 37.31% of SiO2. The amount of CaO in the catalyst B was found to be less in catalyst A. The catalyst A gave higher percentage yield of naphtha oil (48±1.14%v/v), compared to catalyst B (21±1.26%v/v). The performance of this catalyst (A) towards the pyrolysis of plastic wastes was compared to commercial grade ZSM-5 and FCC catalysts. It was found that the catalyst A, CaO based catalyst, reformed from the mortar cement, gave the highest yield of naphtha oil (48±1.14%v/v) compared to ZSM-5 (26±1.52%v/v) and FCC (16±1.09%v/v). The optimum operating temperature for the pyrolysis was found at 410 °C (in the temperature range 370 °C to 450 °C) and the optimum catalyst (A) composition was 0.3 %w/w of mortar cement catalyst in LDPE. This optimum condition gave 86.67± 0 %w/w of liquid, 12.49± 0.24 %w/w of gas and 0.84± 0.24 %w/w of solid. The catalyst A showed the best performance amongst all the catalysts towards the pyrolysis process of plastic wastes.

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42

Musci, M., M. Notaro, F. Curcio, C. Casale, and G. De Michele. "Laser synthesis of vanadium-titanium oxide catalysts." Journal of Materials Research 7, no. 10 (October 1992): 2846–52. http://dx.doi.org/10.1557/jmr.1992.2846.

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A laser-induced process has been studied and developed for the synthesis either of pure TiO2 powders for use as a catalyst support or of mixed Ti1−xVxO2 oxides to be used directly as catalysts in the selective catalytic reduction of nitrogen oxides with ammonia. The radiation source is a 600 W cw CO2 laser and the precursors are titanium and vanadium alkoxides whose vapors are carried under the laser beam by controlled flows of an inert gas and of a reaction sensitizer. The study of the process has been mainly devoted to the optimization of the production rate and of the reaction efficiency. The powder characteristics, related to the process parameters, have been investigated through different techniques. The results show that the particles are monodispersed, unaggregated, monocrystalline with anatase structure and their diameters can be as small as 50 A. Vanadium contents up to X = 0.25 have been obtained in Ti1−xVxO2 compounds, without V2O5 segregation. Finally, a comparison between the behavior of surface VOx active sites has been carried out in catalysts prepared by chemical impregnation of TiO2 and in the mixed Ti–V oxide powders.

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43

Jimenez, Juan, Kathleen Mingle, Teeraya Bureerug, Cun Wen, and Jochen Lauterbach. "Statistically Guided Synthesis of MoV-Based Mixed-Oxide Catalysts for Ethane Partial Oxidation." Catalysts 8, no. 9 (September 2, 2018): 370. http://dx.doi.org/10.3390/catal8090370.

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The catalytic performance of Mo8V2Nb1-based mixed-oxide catalysts for ethane partial oxidation is highly sensitive to the doping of elements with redox and acid functionality. Specifically, control over product distributions to ethylene and acetic acid can be afforded via the specific pairing of redox elements (Pd, Ni, Ti) and acid elements (K, Cs, Te) and the levels at which these elements are doped. The redox element, acid element, redox/acid ratio, and dopant/host ratio were investigated using a three-level, four-factor factorial screening design to establish relationships between catalyst composition, structure, and product distribution for ethane partial oxidation. Results show that the balance between redox and acid functionality and overall dopant level is important for maximizing the formation of each product while maintaining the structural integrity of the host metal oxide. Overall, ethylene yield was maximized for a Mo8V2Nb1Ni0.0025Te0.5 composition, while acetic acid yield was maximized for a Mo8V2Nb1Ti0.005Te1 catalyst.

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44

Al-ghamdi, Mohammed, and Hossein Bayahia. "Zinc-Chromium oxide catalyst for gas-phase ketonisation of pentanoic acid." Mediterranean Journal of Chemistry 6, no. 2 (November 13, 2016): 1. http://dx.doi.org/10.13171/mjc61/01611081426-bayahia.

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Oxides of Zinc and Chromium mixed catalyst with different atomic ratios of Zinc and Chromium were tested in the ketonisation of pentanoic acid in the gas phase. These catalysts were active to form 5-nonanone, at 300 – 400 oC and ambient pressure. It found that Zn-Cr with an atomic ratio (10:1) gave the best catalytic performance in comparison with other oxides with higher or lower atomic ratio of Zn and Cr mixed oxides, ZnO and Cr2O3. In this test, Zn-Cr (10:1) gave 82% selectivity of 5-nonanone as the main product at 86% conversion of acid at 350oC. The catalyst showed stable performance at the best selected conditions with a small decrease of acid conversion. For catalyst characterization, BET surface area and porosity technique, X-ray diffraction and DRIFTS of pyridine adsorption were used.

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45

Al-ghamdi, Mohammed, and Hossein Bayahia. "Zinc-Chromium oxide catalyst for gas-phase ketonisation of pentanoic acid." Mediterranean Journal of Chemistry 6, no. 2 (November 13, 2016): 1. http://dx.doi.org/10.13171/mjc62/01611081426-bayahia.

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Oxides of Zinc and Chromium mixed catalyst with different atomic ratios of Zinc and Chromium were tested in the ketonisation of pentanoic acid in the gas phase. These catalysts were active to form 5-nonanone, at 300 – 400 oC and ambient pressure. It found that Zn-Cr with an atomic ratio (10:1) gave the best catalytic performance in comparison with other oxides with higher or lower atomic ratio of Zn and Cr mixed oxides, ZnO and Cr2O3. In this test, Zn-Cr (10:1) gave 82% selectivity of 5-nonanone as the main product at 86% conversion of acid at 350oC. The catalyst showed stable performance at the best selected conditions with a small decrease of acid conversion. For catalyst characterization, BET surface area and porosity technique, X-ray diffraction and DRIFTS of pyridine adsorption were used.

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46

Pérez, J. J., D. J. Escalante, L. A. González, and J. A. Pérez. "Catalytic Activity of Polymetallic and Hydrotalcite-like Catalysts in the Synthesis of Methanol by Carbon Dioxide Hydrogenation." Renewable Energy and Power Quality Journal 20 (September 2022): 569–73. http://dx.doi.org/10.24084/repqj20.370.

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Two Cu-Zn-Al catalysts prepared by the coprecipitation method, both differing in their type of structure, one as a mixed oxide (polymetallic catalyst) and the other as a hydrotalcite-like catalyst, were used for the synthesis of methanol by hydrogenation of CO2 in a fixed bed reactor system, operating under conditions of low pressure (6 bar) and temperature of 265°C. The effect of the composition of the catalyst on its catalytic activity under low pressure conditions was investigated. The main results show that the highest CO2 conversion is found with Cu-ZnAl polymetallic catalyst, however, the best selectivity to methanol is shown for Cu-Zn-Al hydrotalcite-like catalyst.

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47

Zhang, Qiuyun, Xiaofang Liu, Tingting Yang, Quanlin Pu, Caiyan Yue, Shuya Zhang, and Yutao Zhang. "Catalytic Transfer of Fructose to 5-Hydroxymethylfurfural over Bimetal Oxide Catalysts." International Journal of Chemical Engineering 2019 (April 1, 2019): 1–6. http://dx.doi.org/10.1155/2019/3890298.

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Direct conversion of fructose into 5-hydroxymethylfurfural (HMF) is achieved by using modified aluminum-molybdenum mixed oxide (S-AlMo) as solid acid catalysts. The synthesized catalyst was characterized by powder XRD, nitrogen adsorption-desorption isotherm, NH3-TPD, and SEM. As a result, the presence of strong acidity, mesostructures, and high surface area in the S-AlMo catalyst was confirmed by nitrogen adsorption-desorption isotherm and NH3-TPD studies. A study by optimizing the reaction conditions such as catalyst dosage, reaction temperature, and time has been performed. Under the optimal reaction conditions, HMF was obtained in a high yield of 49.8% by the dehydration of fructose. Moreover, the generality of the catalyst is also demonstrated by glucose and sucrose with moderate yields to HMF (24.9% from glucose; 27.6% from sucrose) again under mild conditions. After the reaction, the S-AlMo catalyst can be easily recovered and reused four times without significant loss of its catalytic activity.

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48

Soongprasit, Kanit, Duangdao Aht-Ong, Viboon Sricharoenchaikul, and Duangduen Atong. "Effect of Complexing Agent on Morphology and Crystal Structure of La_1-xCe_xCoO₃ (x=0, 0.2, and 0.4) Perovskite-Type Mixed Oxides Catalyst Prepared by Sol-Gel Method." Materials Science Forum 658 (July 2010): 29–32. http://dx.doi.org/10.4028/www.scientific.net/msf.658.29.

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. La1-xCexCoO3 (x=0, 0.2, and 0.4) perovskite-type mixed oxides using polyvinyl alcohol (PVA) as complexing agent at two molar ratio of metal ion to PVA (1:1 and 1:2) were successfully prepared by sol-gel process. The precursor included lanthanum (II) nitrate hexahydrate, cerium (II) nitrate hexahydrate, and cobalt (II) nitrate hexahydrate where polyvinyl alcohol was added as complexing agent. The suitable condition of Cerium (Ce) substitution and PVA molar ratio were established for further application in hydrocarbon conversion to high value added products. TGA thermogram of as-prepared precursor showed that PVA absolutely decomposed at temperature higher than 500°C. XRD patterns of calcined catalyst showed both LaCoO3 rhombohedral and CeO2 cubic structures that confirmed the formation of mixed crystal structure. Nevertheless, Co3O4 slightly appeared with low peak intensity which came from the oxidation reaction of as-prepared catalyst during calcinations. XRD showed that PVA did not effect to crystal structure of synthesized catalyst. Higher PVA content added in the precursor cause the reduction of crystal growth of catalyst in calcinations step. In contrast, morphology of catalyst is directly related with PVA content such that the spongy and sheet-like structure were formed with increasing PVA content which prevented the agglomeration of particles. The results showed that PVA content play an important role in morphology of perovskite-type mixed oxide catalysts but did not affected to their crystal structures.

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49

Razali, Noraini, and Ahmad Zuhairi Abdullah. "Mixed Oxide Catalyst for the Oxidation of Glycerol to Lactic Acid: Influence of the Preparation Method and Calcination Temperature." Indonesian Journal of Chemistry 20, no. 3 (May 9, 2020): 608. http://dx.doi.org/10.22146/ijc.44137.

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The selective oxidation reaction of glycerol to produce lactic acid is a high-temperature reaction, and requiring a catalyst with high thermal stability. The mixed metal oxide is one of the potential catalysts to be explored. In this study, prepared CaCe supported on ZrO2 catalyst with two preparation methods (co-precipitation and impregnation), and calcination temperatures (800 and 600 °C) were investigated. The oxidation reaction of glycerol to lactic acid was carried out at 250 °C for 2 h in a base-free condition using pure glycerol as a reactant. The catalysts were characterized using XRD, TGA, XPS, SEM and basicity test to evaluate and correlate the physical and chemical properties with their catalytic performance. It was found that the catalyst prepared by co-precipitation and calcined at 800 °C exhibited the highest catalytic performance. The high lactic acid yield of 38.8 and 95% glycerol conversion were achieved. The catalyst was successfully developed with sufficient porosity and high intensity of mixed metal structure that contributed to the desired high performance. Improvement in the basicity and formation of surface oxygen vacancies was attributed to cationic Ce4+/Ce3+ elements leading to the promotion of lactic acid yield and high glycerol conversion.

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50

Wang, Jun, Mei Lin Jia, Meng Gen Tuya, Jiang Wang, and Zhao Ri Ge Tu Bao. "The Performance of Au-Pd/Ni-Al-O for Heck Reaction." Advanced Materials Research 955-959 (June 2014): 494–97. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.494.

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Au-Pd alloy nanoparticles supported on Ni-Al mixed oxide were prepared by impregnation-reduction method. Characterizations of the catalysts were applied by X-ray diffraction and UV-Vis spectrum. The bimetallic catalysts exhibited excellent catalytic activity in Heck reaction under mild conditions. Due to the easy separation of solid catalyst, it is thought as environmental friendly and these catalysts will be potential material in the synthesis of fine chemistry.

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