2O3 Catalyst Research Articles

PET Glycolysis to BHET Efficiently Catalyzed by Stable and Recyclable Pd-Cu/γ-Al2O3.

Glycolysis of poly(ethylene terephthalate) (PET) is a prospective way for degradation of PET to its monomer bis(hydroxyethyl) terephthalate (BHET), providing the possibility for a permanent loop recycling. However, most reported glycolysis catalysts are homogeneous, making the catalyst difficult to recover and contaminating the products. Herein, we reported on the Pd-Cu/γ-Al2O3 catalyst and applied it in the glycolysis of PET as catalyst. The formed structure gave Pd-Cu/γ-Al2O3 a high active surface area, which enabled these micro-particles to work more efficiently. The PET conversion and BHET yield reached 99% and 86%, respectively, in the presence of 5 wt% of Pd-Cu/γ-Al2O3 catalyst within 80 min at 160 °C. After the reaction, the catalyst can be quickly separated by filtration, so it can be easily reused without significant loss of reactivity at least five times. Therefore, the Pd-Cu/γ-Al2O3 catalyst may contribute to an economically and environmentally improved large-scale recycling of PET fiber waste.

Evolution of the Active Phase of Pt/Sn-Al2O3 Catalysts During Acidic Impregnation and Their Use in Propane Dehydrogenation.

Alumina-supported PtSn is an industrialized catalyst for propane dehydrogenation. During the catalyst impregnation, the acidic impregnation solution with chloroplatinic acid as a precursor inevitably leads to the partial dissolution of the surface of amphoteric alumina support and finally varies catalytic performance. Herein, the structure evolution of the active phase, induced by an impregnated acidic solution, was studied with special care. According to the diffused double layer theory, we proposed a model of microgels during impregnation. The microgels formed in the solution with suitable acidity on the surface of the catalysts evolved into a structure of Al2O3-coated oxidized Pt by reprecipitation during drying and calcination. The covered Pt species could be exposed by Ar+ sputtering or migrate to the surface during reduction to serve as active sites for propane dehydrogenation. Noticeably, the surface Sn0 species was generated when the pH of the impregnated solution was around 0.56, which is solid proof for the unique active phase with the PtSn alloy present on SnOx species existing on the surface of the Sn-Al2O3 support. The synthesized catalyst exhibited high propylene selectivity (99.4%) and superior stability (kd = 0.002 h-1). This study provides new insight for the precise preparation of Pt/Sn-Al2O3 catalysts.

Non-Oxidative Coupling of Methane via Plasma-Catalysis Over M/γ-Al2O3 Catalysts (M = Ni, Fe, Rh, Pt and Pd): Impact of Active Metal and Noble Gas Co-Feeding

Plasma-catalysis has attracted significant interest in recent years as an alternative for the direct upgrading of methane into higher-value products. Plasma-catalysis systems can enable the electrification of chemical processes; however, they are highly complex with many previous studies even reporting negative impacts on methane conversion. The present work focuses on the non-oxidative plasma-catalysis of pure methane in a Dielectric Barrier Discharge (DBD) reactor at atmospheric pressure and with no external heating. A range of transition and noble metals (Ni, Fe, Rh, Pt, Pd) supported on γ-Al2O3 are studied, complemented by plasma-only and support-only experiments. All reactor packings are investigated either with pure methane or co-feeding of helium or argon to assess the role of noble gases in enhancing methane activation via energy transfer mechanisms. Electrical diagnostics and charge characteristics from Lissajous plots, and electron temperature and collision rates calculations via BOLSIG+ are used to support the findings with the aim of elucidating the impact of both active metal and noble gas on the reaction pathways and activity. The optimal combination of Pd catalyst and Ar co-feeding achieves a substantial improvement over non-catalytic pure methane results, with C2+ yield rising from 30% to almost 45% at a concurrent reduction of energy cost from 2.4 to 1.7 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\ ext{M}\ ext{J}\\:{\ ext{m}\ ext{o}\ ext{l}}_{\ ext{C}{\ ext{H}}_{4}}^{-1}$$\\end{document} and from 9 to 4.7 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\ ext{M}\ ext{J}\\:\ ext{m}\ ext{o}{\ ext{l}}_{{\ ext{C}}_{2+}}^{-1}$$\\end{document}. Pd, along with Pt, further displayed the lowest coke deposition rates among all packings with overall stable product composition during testing.

Reforming of methane over two-dimensional Mo2C-Ni/γ-Al2O3 catalyst

The impact of two-dimensional Mo2C (2D-Mo2C) on the activity and stability of a Ni/γ-Al2O3 catalyst for the dry reforming of methane (DRM) is reported. 1.1 wt% 2D-Mo2C added to 13 wt% Ni/γ-Al2O3 increased activity by ∼40 %. Characterization results showed an interaction between 2D-Mo2C and Ni that resulted in the formation of a NixMoy bulk phase (XRD) and Ni-Mo-oxycarbide surface species (XPS). The presence of 2D-Mo2C also improved the stability of the catalyst compared to Ni/γ-Al2O3 by reducing coke deposition. H2 space-time-yields (STYs) were independent of CO2 partial pressure and were lower than the CO STYs. Power law kinetic models were consistent with a DRM reaction pathway via CH4 decomposition (MD) and the reverse Boudouard (RBD) reactions.

Boosting the active sites of Cu/Ce0.8Zr0.2O2 catalysts through tailored precipitation method

A reverse co-precipitation method was employed to increase the surface area of Ce0.8Zr0.2O2, resulting in boosting the active sites of Cu catalysts in the water–gas shift reaction (WGS). Active Cu sites and oxygen vacancy have been systematically controlled through the modification of physical properties and geometric configuration via a reverse co-precipitation of Ce0.8Zr0.2O2 support. The catalytic activity in WGS is primarily dependent on the number of active Cu species and is partially on the oxygen storage capacity. The kinetic results with Cu loadings revealed that the efficiency of active metal utilization was effectively enhanced by a reverse co-precipitation method, compared to the normal precipitation method, owing to the moderate metal–support interactions. The turnover frequency values were independent of Cu dispersion, highlighting the structure-insensitivity of Cu/Ce0.8Zr0.2O2 catalysts. This work suggests the possibility of controlling metal–support interactions through support synthesis methods.

The study of design and performance improvement of catalysts for the stepwise production of bicyclohexane from benzene and cyclohexene

Bicyclohexane is a hydrogen storage reagent with high hydrogen density and low boiling point. Compared with the hydrogenation of biphenyl, the alkylation of benzene and cyclohexene to cyclohexylbenzene and hydrogenation is a promising way to prepare cyclohexane on a large scale. The research and development of high-efficiency cyclohexyl benzene hydrogenation catalyst should be further developed based on mature alkylation technology. This paper used an acidified USY molecular sieve to catalyze the alkylation of benzene and cyclohexene to cyclohexylbenzene, which achieved 100% conversion and selectivity. Furthermore, Pt/TiO2/γ-Al2O3 catalyst is prepared by pre-deposition TiO2 film of different thicknesses on γ-Al2O3 surface and then supported with platinum particles by Atomic layer deposition (ALD). The role of TiO2 film in improving the cyclohexylbenzene hydrogenation performance of the catalyst is studied. TEM, CO pulse chemisorption, CO-DRIFTs, quasi-in situ XPS, H-D exchange, and H2-TPR characterization show that compared with Pt/γ-Al2O3, TiO2 thin films on Pt/TiO2/γ-Al2O3 do not change the dispersion of Pt particles, but can form new Pt-TiO2 interactions. The hydrogenation performance of cyclohexylbenzene was improved by increasing the electron density and the proportion of planar active sites on the surface of platinum and reducing the energy barrier of hydrogen spillover. The research provides theoretical support for further bicyclohexane organic liquid hydrogen storage reagent development. The relevant metal-support interaction regulation strategy can be applied to the development of efficient catalysts for other aromatic molecules hydrogenation.

Optimization of Metal-Support Cooperation for Boosting the Performance of Supported Gold Catalysts for the Borylation of C-O and C-N Bonds.

The cooperation of multiple catalytic components is a powerful tool for intermolecular bond formation, specifically, cross-coupling reactions. Supported metal catalysts have interfacial sites between metal nanoparticles and their supports where multiple catalytic elements can work in cooperation to efficiently promote intermolecular reactions. Hence, the establishment of novel guidelines for designing active interfacial sites of supported metal catalysts is indispensable for heterogeneous catalysts which enable efficient cross-coupling reactions. In this article, we performed kinetic and theoretical studies to elucidate the effect of metal-support cooperation for the borylation of C-O bonds by supported gold catalysts and revealed that the Lewis acid density of the supports determined the number of active sites at which metal nanoparticles (NPs) and Lewis acid at the surface of the supports work in cooperation. Furthermore, DFT calculations revealed that strong adsorption of diborons at the interface between Au NPs and supports and a decrease in the LUMO level of adsorbed diboron were responsible for efficient C-O bond borylation. Supported Au catalysts with the optimized metal-metal oxide cooperation sites, namely, Au/α-Fe2O3 catalyst, showed excellent activity for C-O bond borylation, and also enabled the synthesis of organoboron compounds by using continuous-flow reactions. Furthermore, Au/α-Fe2O3 showed high activity for direct C-N bond borylation without the transformation of amino groups to ammonium cations. The results described herein suggest that the optimization of metal-metal oxide cooperation is beneficial for taking full advantage of the potential performance of supported metal catalysts for intermolecular reactions.

Morphology-dependent support effect of PdCu/alpha-Fe2O3 catalysts on Suzuki-Miyaura cross-coupling reaction

The palladium-catalyzed Suzuki-Miyaura cross-coupling (SMC) reaction has received worldwide attention as a powerful and convenient synthetic tool for the formation of biaryl compounds. However, these reactions are highly dependent on the activity and stable of catalysts. Herein, the support morphology-dependent catalytic performance of SMC reactions was investigated. The truncated hexagonal bipyramid (α-Fe2O3-O) and rod-shaped morphologies of alpha-Fe2O3 (α-Fe2O3-R) were used as support to prepare PdCu nanoparticles (NPs) catalysts by NaBH4 reduction method. For PdCu/α-Fe2O3-R catalysts, the smaller size of PdCu NPs and more low coordination Pd sites leading to its superior catalytic performance for SMC reactions. Furthermore, it can be easily recycled through centrifugation and reused several times without obvious loss on its catalytic performance. Identical location transmission electron microscopy method was used to investigate the structural evolution of PdCu/α-Fe2O3-R catalysts. The results found that its structure almost unchanged during the catalytic reaction.

Unveiling the Mechanism of Plasma-Catalytic Low-Temperature Water-Gas Shift Reaction over Cu/γ-Al2O3 Catalysts.

The water-gas shift (WGS) reaction is a crucial process for hydrogen production. Unfortunately, achieving high reaction rates and yields for the WGS reaction at low temperatures remains a challenge due to kinetic limitations. Here, nonthermal plasma coupled to Cu/γ-Al2O3 catalysts was employed to enable the WGS reaction at considerably lower temperatures (up to 140 °C). For comparison, thermal-catalytic WGS reactions using the same catalysts were conducted at 140-300 °C. The best performance (72.1% CO conversion and 67.4% H2 yield) was achieved using an 8 wt % Cu/γ-Al2O3 catalyst in plasma catalysis at ∼140 °C, with 8.74 MJ mol-1 energy consumption and 8.5% H2 fuel production efficiency. Notably, conventional thermal catalysis proved to be ineffective at such low temperatures. Density functional theory calculations, coupled with in situ diffuse reflectance infrared Fourier transform spectroscopy, revealed that the plasma-generated OH radicals significantly enhanced the WGS reaction by influencing both the redox and carboxyl reaction pathways.

Co3O4-modified 3DOM LaFe0.6Mg0.4O3 perovskite as robust catalysts for soot oxidation

In this study, 3DOM LaFe0.6Mg0.4O3 perovskite was prepared using a colloidal crystal template technique and subsequently decorated with Co3O4 for soot combustion. The results indicated that the LaFe0.6Mg0.4O3 perovskite with three-dimensional ordered macropores structure could facilitate the dispersion of Co3O4, boost the number of active sites for soot combustion, and significantly enhance the contact efficiency between the catalyst and soot. The interaction between Co3O4 and perovskite created additional oxygen vacancies and enhanced the redox ability of the catalysts. Meanwhile, the presence of Co3O4 facilitated the adsorption and activation of O2, which could accelerate the oxidation of soot particles. Notably, the 2.5 %Co/LaFe0.6Mg0.4O3 catalyst exhibited the highest performance, achieving a T50 of 407 °C for soot combustion in the presence of 500 ppm NO and 5 % O2. The catalyst also demonstrated excellent stability and water resistance, making it a promising candidate for practical applications.

Biomass-incorporated KNO3-C/γ-Al2O3 bifunctional catalyst for efficient biodiesel production

Biodiesel has gained attention as a promising renewable and sustainable alternative to fossil fuels, which necessitated the development of an effective and eco-friendly catalyst for transesterification processes. Herein, this research reported the development of a highly efficient bifunctional catalyst by incorporating carbon from oil palm leaves (OPLs) into KNO3/γ-Al2O3 catalyst, synthesized through a facile method, to concurrently catalyze the waste cooking oil (WCO) transesterification and free fatty acids (FFAs) esterification in a one-pot reaction. Proposed Box-Behnken Design (BBD) model's ideal conditions, experimentally yielded an average of 93.74 % biodiesel yield. Meanwhile, analysis revealed that the catalyst with 30 wt% KNO3 loadings and 1.0 g oil palm leaves dosage (OPLD), calcined at 700 °C, has a BET surface area of 46.93 m2/g and exhibited the presence of K2O, K2O2 and K2C2 active species on the catalyst surface. In addition to exhibiting high total basicity and acidity of 2.9 mmol/g and 2.1 mmol/g, respectively, environmental studies suggested this catalyst generated less waste, highlighting its significant potential of being used for efficient biodiesel production. Therefore, present research introduces a new approach for synthesizing a fruitful and ecofriendly bifunctional catalyst to attain one-pot biodiesel production from low-grade oils.

Fe2O3/γ-Al2O3 and NiO/γ-Al2O3 catalysts for the selective catalytic oxidation of ammonia

Ammonia, a significant atmospheric pollutant, requires effective emission control due to its inherent toxicity and the generation of secondary pollutants like particulate matter. This control can be achieved through various methods, including catalytic processes. Therefore, our study focuses on evaluating the potential of catalysts based on iron oxide and nickel oxide supported on γ–Al2O3 for the selective catalytic oxidation of NH3 to N2 (NH3-SCO). The γ–Al2O3 was obtained by thermal decomposition of aluminum hydroxide, and 5 or 10 wt% of Fe or Ni was added through wetness incipient impregnation. XRD diffractograms confirmed the formation of the γ–Al2O3 phase. XRD, H2-TPR, and UV–vis DRS data showed the presence of Fe2O3, NiO, and NiAl2O4 in the catalysts. Introducing metal oxides onto the support led to a drop in the specific area, pore size, pore volume, and NH3 desorption, which was higher for the catalysts containing Fe. The catalysts were active in NH3-SCO, and the insertion of Fe or Ni was essential because it promoted a significant increase in the NH3 conversion (∼75 % Fe and ∼55 % Ni), compared to pure support (∼8 %), mainly from 400 °C. However, doubling the metal content has not resulted in a considerable increase in NH3 conversion. The N2 selectivity was higher for the catalysts containing Ni (∼85 %) from 400 °C compared to catalysts containing Fe (∼76 %). Such behavior was due to the larger surface area of the Ni-containing catalysts. Despite that, the 5Fe/γ–Al2O3 catalyst emerged as the most effective option for NH3-SCO applications, combining higher NH3 conversion and good N2 selectivity.

Direct conversion of biogas to syngas over bimetallic nickel–cobalt supported on α-alumina catalysts

Syngas is an essential feedstock for many valuable chemicals, produced primarily by steam reformation of methane. Recently, dry reformation (reaction between methane and carbon dioxide) has gained importance as both the reactants are greenhouse gases (GHGs). However, dry reformation (DRM) produces syngas with a low H2/CO (<1.0). The DRM requires catalyst such as nickel supported on alumina, which results in higher coke. In this study, 6Ni–6Co/α-Al2O3 and 12Ni/α-Al2O3 catalysts were prepared by wetness impregnation. The catalysts were characterized using FESEM, XRD, XPS, BET, H2-TPR, NH3-TPD and H2-Chemisorption. The catalyst performance under DRM conditions were carried out in a fixed bed reactor at 20,000 ml/gcat.hr GHSV, between 600 °C and 700 °C, at atmospheric pressure. The performance of the catalysts was compared based on conversion of methane and carbon dioxide, hydrogen to carbon monoxide and coke deposition. The rates of consumption of methane carbon dioxide were found to be equal, and higher rates were observed for 6Ni–6Co/α-Al2O3, which is attributed to NiAl2O4/CoAl2O4 phase of active metals, higher surface area, smaller crystallite size and higher dispersion. This active phase of catalyst also responsible for higher rate of CO2 adsorption and reduced coke deposition. Highest H2/CO was found to be 1.26 for 6Ni–6Co/α-Al2O3.

Elevating catalyst performance: How hierarchical Alumina's phases enhance Cu/Al2O3 in reverse water-gas shift (RWGS) reaction

A hierarchical structure alumina with high surface area was synthesized using a sol-gel method assisted by propylene oxide (PO), which was subsequently converted into alumina exhibiting different transitional phases (γ, δ, θ) through varying calcination temperatures. These aluminas were employed as substrates for the active copper phase in the RWGS catalyst, facilitating a systematic exploration of how the alumina phase influences catalyst performance. The characterized catalysts underwent assessments using techniques such as N2 adsorption-desorption, XRD, H2-TPR, CO2-TPD, FESEM, and HRTEM. An examination of the impact of copper loading (ranging from 5.0 to 20.0 wt%) in the Cu/γ-Al2O3 catalyst on RWGS performance revealed that the catalyst containing 15.0 wt% Cu exhibited the highest CO2 conversion rate, achieving 8% at 300 °C under a 1CO2:1H2 ratio at atmospheric pressure. This specific catalyst demonstrated 100% selectivity for CO. Evaluating the extended stability of Cu catalysts supported by γ-, δ-, and θ-Al2O3 phases, all loaded with the same amount of Cu (15.0 wt%), was carried out at 450 °C. The δ- and θ-Al2O3-supported catalysts were able to maintain approximately 100% of their initial catalytic activities after 72 h, whereas the activity of the catalyst supported by γ-Al2O3 decreased. The examination of the crystalline phases of the catalyst support and stability testing demonstrated the significant impact of porosity on mass transfer and the diffusion processes of reactants and production on the structure of the catalyst. This study revealed how adjusting the macropore size and porosity within various crystalline phases can optimize the filling degree and achieve an ideal balance between reaction and mass transfer rates.

Global Optimization of Cation Ordering in Perovskites by Recommendation-Based Basin-Hopping.

Cation ordering in multication perovskites is related to many important material properties and performances, but computational determination of the cation ordering remains a major challenge. Here, we propose a new computational approach by introducing a machine learning recommender system into the basin-hopping framework (RBH) for optimizing cation ordering. Taking the electrocatalyst Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF5582) as a showcase example, we found that the efficiency of RBH in identifying low-energy configurations outperforms the methods of cluster expansion and conventional basin-hopping. The RBH results revealed that the BSCF5582 catalyst tended to have a layered ordering of A-site cations and disordered B-site cations both in bulk and on the surfaces. Further, on the A-site-terminated surface, we found the segregation of large Ba atoms. Similarly, on the A-site- terminated surface of the recently developed Cs0.2Sr0.8Co0.4Fe0.6O3 (CSCF2846) catalyst, layered ordering at the A-site and surface enrichment of large Cs atoms were also found. The layered ordering was robust against thermal effects, as found from molecular dynamics simulations at 800 K. This work provides a new approach for thermodynamic global optimization of chemical ordering in multicomponent materials.

Combining Solid FePc Immobilized on Py-Functionalized Carbon Matrix with Soluble Redox Mediator FePc As an Efficient Cathode Catalyst for Non-Aqueous Li-O2 Batteries

It is important to develop bifunctional catalysts with high activity and stability for reversible oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) in lithium-oxygen (Li-O2) batteries. Recently, the iron phthalocyanine (FePc) complex has been considered a promising candidate for bifunctional (ORR/OER) O2 catalysts due to its low cost, high catalytic properties, and ease of preparation. In this work, two different structural types of FePc-based solution-phase catalysts as soluble redox mediators (SRMs) and solid FePc immobilized on pyridine-functional carbon supports (multi-walled carbon nanotube, MWCNT and graphene, GR) are investigated to evaluate the influence of FePc structural design on their catalytic activity and kinetics.Our work demonstrated that FePc(solid)/Py/MWCNT exhibited better bifunctional catalytic activity than FePc(solid)/Py/GR in the same electrolyte because of the stronger axial bonding between FePc(solid) and Py/MWCNT. The combination of FePc(solid)/Py/MWCNT and FePc(sol) displays the best cyclability, which can be attributed to the highly efficient solid-liquid interface. Moreover, FePc(solid)/Py/MWCNT without FePc(sol) shows the lowest overpotential owing to the surface-grown thin film Li2O2 is structurally less order than the solution-grown toroidal Li2O2.

Deep oxidation of CH2Cl2 over Mo-doped CoAl2O4 spinel oxides: Unravelling the promoting roles of Brønsted acidity and H2O

A series of Mo-doped CoAl2O4 spinel oxides were prepared and tested for deep oxidation of dichloromethane (CH2Cl2). The Mo-doping resulted in much improved surface acidity of the catalyst, and thus significantly enhanced the catalytic activity. The best performance was obtained on a CoAl1.7Mo0.3O4 catalyst, which gave a nearly 3-fold higher reaction rate than the pristine CoAl2O4 (26.5 x 10-8 versus 10.5 x 10-8 mol g−1 s−1 at 230 °C). Moreover, the Mo-doped catalyst remarkably suppressed the formation of organic byproduct of CH3Cl. The good catalytic performance of the catalysts was ascribed to the fact that abundant Brønsted acid sites derived from Mo5+–OH in the Mo-doped catalysts facilitated the C-Cl bond cleavage of the CH2Cl2 and CH3Cl reactants and their further oxidation. Water in the reaction feed was found to enhance the activity, due to its dissociation on the catalyst surface to hydroxyl groups that could react with CH2Cl2. Therefore, our findings revealed the vital roles of surface Brønsted acidity and H2O in the catalytic combustion of chlorinated volatile organic compounds.

Operando Soft X-ray Absorption of LaMn1-x Co x O3 Perovskites for CO Oxidation.

We employed operando soft X-ray absorption spectroscopy (XAS) to monitor the changes in the valence states and spin properties of LaMn1-x Co x O3 catalysts subjected to a mixture of CO and O2 at ambient pressure. Guided by simulations based on charge transfer multiplet theory, we quantitatively analyze the Mn and Co 2p XAS as well as the oxygen K-edge XAS spectra during the reaction process. The Mn sites are particularly sensitive to the catalytic reaction, displaying dynamics in their oxidation state. When Co doping is introduced (x ≤ 0.5), Mn oxidizes from Mn2+ to Mn3+ and Mn4+, while Co largely maintains a valence state of Co2+. In the case of LaCoO3, we identify high-spin and low-spin Co3+ species combined with Co2+. Our investigation underscores the importance to consider the spin and valence states of catalyst materials under operando conditions.

Mechanistic insights on the preparation of 5-methyl-2-hexanone by hydrogenation of 5-methyl-3-hexen-2-one using Pd/Al2O3 catalysts

5-methyl-2-hexanone is used as a versatile polymerization solvent for industrial preparation processes of bulk and fine chemicals. An efficient catalyst, Pd/γ-Al2O3, is reported for the preparation of 5-methyl-2-hexanone by selective hydrogenation of 5-methyl-3-hexen-2-one. The catalyst exhibits remarkable activity and selectivity even at atmospheric pressure and low temperature (1 atm, 80 °C). The influence weight of reaction conditions on the reaction process was obtained through the Artificial Neural Network model, which were reaction pressure, reaction temperature and liquid hourly space velocity in order. The reaction kinetics and mechanism of 5-methyl-2-hexanone preparation by hydrogenation over Pd/γ-Al2O3 catalyst were investigated. The hydrogenation reaction pathway of 5-methyl-3-hexen-2-one was obtained by using Density functional theory calculations, and the mechanism of selective hydrogenation of CC double bonds and CO double bonds was revealed. A kinetic model based on the LHHW model assumption was also proposed and compared with experimental results demonstrating good predictability.

The effect of calcination gas atmosphere on the structural organization of Ru/Ce0.75Zr0.25O2 catalysts for CO2 methanation

In this study, supported 5 wt% Ru/Ce0.75Zr0.25O2 catalysts were prepared by sorption-hydrolytic deposition technique, followed by calcination under different conditions, namely in reductive H2/N2 (Ru/CeZr_red) and oxidative air (Ru/CeZr_ox) atmospheres. A thorough characterization of the catalysts was carried out by XRD, CO chemisorption, HRTEM, Raman spectroscopy, XPS, and in situ DRIFTS. The findings showed that the choice of the calcination atmosphere has a great impact on the structural organization of the catalyst. Calcination in air results in the formation of the larger crystalline RuO2 particles, which tend to enlarge upon reduction under CO2 methanation conditions. The reductive treatment results in a much higher dispersion of supported Ru species and a more pronounced metal-support interaction (MSI). In the Ru/CeZr_red catalyst, a large amount of atomic scale Ru species was detected along with metallic Ru nanoparticles and clusters. However, it was found that the superiority of the Ru/CeZr_red catalyst in the Ru dispersion did not result in the significant advantage in the CO2 methanation activity. In situ DRIFTS results suggested that the MSI affects the ability of Ru species to adsorb and activate reagent molecules, in particular, enhances the adsorption strength of the intermediate CO species.