Catalysis Today最新文献

{"title":"Oligomerization of ethylene by dinuclear chromium catalysts bearing phenyl-bridged bifunctional imine-pyrrolide/thiophene ligands","authors":"Sabrina M. da Silva ,&nbsp;Harryson M. Capello ,&nbsp;Robson S. Oliboni ,&nbsp;Rafael Stieler ,&nbsp;Adriana C.A. Casagrande ,&nbsp;O.L. Casagrande Jr","doi":"10.1016/j.cattod.2024.115008","DOIUrl":"10.1016/j.cattod.2024.115008","url":null,"abstract":"<div><p>Dinuclear chromium(III) complexes [Cr(<em>Z</em>)-2-(HC<img>N)-2-OCH₃C₆H₄)(THF)Cl₂]₂ (Z= C₄H₃N, <strong>L1-Cr</strong>_{<strong>2</strong>}) or [Cr(<em>Z</em>)-2-(HC<img>N)-2-OCH₃C₆H₄)(THF)Cl₃]₂ (Z = C₄H₃S, <strong>L2-Cr</strong>_{<strong>2</strong>}; Z = 5-methyl-C₄H₂S, <strong>L3-Cr</strong>_{<strong>2</strong>}; Z = 5-phenyl-C₄H₂S, <strong>L4-Cr</strong>_{<strong>2</strong>}) were synthesized by reaction of the phenyl-bridged bifunctional imine-pyrrole/thiophene ligands with [CrCl₃(THF)₃]. DFT calculations for <strong>L2-Cr</strong>_{<strong>2</strong>} revealed that both isomers (<em>anti</em> and <em>syn</em>) are stable presumably due to the nonrigid skeleton of this class of ligands. On activation with MAO, all chromium complexes showed catalytic activity in ethylene oligomerization, providing a non-selective distribution of α-olefins (C₄-C₁₂⁺) together with varying amounts of polymer (3.6 – 45.0 wt%). The nature of the pendant heterocyclic moieties plays a substantial influence on the catalytic performances of these binuclear Cr catalysts. <strong>L1-Cr</strong>_{<strong>2</strong>} bearing pyrrolide unit yielded a significant quantity of polymer (45.0 wt%) while the binuclear chromium complexes based on thiophene unit showed higher productivities towards production of oligomers (up to 94.4 wt%). These latter Cr complexes showed higher productivities in comparison to their mononuclear analogues. DFT calculations, assuming the formation of cationic chromium (III) species after treatment with MAO in ethylene atmosphere, suggested the coordination of the thiophene group to the chromium metal center, and thus influencing the catalytic performance of <strong>L2Cr</strong>_{<strong>2</strong>} <strong>– L4-Cr</strong>_{<strong>2</strong>}. By adjusting the reaction conditions, <strong>L3-Cr</strong>_{<strong>2</strong>} showed TOF of 131,100 mol ethylene·mol Cr⁻¹·h⁻¹ producing predominantly oligomers (89.3 wt% of total products) with high selectivity for α-olefins (&gt;91.5 wt%).</p></div>","PeriodicalId":264,"journal":{"name":"Catalysis Today","volume":"444 ","pages":"Article 115008"},"PeriodicalIF":5.2,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142049499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Catalytic pyrolysis of polystyrene over rice husk silica-derived traditional and hierarchical green MWW zeolites","authors":"Thaís Schmitz ,&nbsp;Arthur Motta de Andrade ,&nbsp;Francieli Martins Mayer ,&nbsp;Isabel Cristina Tessaro ,&nbsp;Nilson Romeu Marcilio ,&nbsp;Maria do Carmo Rangel ,&nbsp;Anderson Joel Schwanke","doi":"10.1016/j.cattod.2024.115010","DOIUrl":"10.1016/j.cattod.2024.115010","url":null,"abstract":"<div><p>This work aimed at the green synthesis of MWW zeolites using rice husk silica as an alternative raw material. It was also performed a post-synthesis desilication procedure with NaOH and CTABr aiming to obtain MWW zeolites with improved accessibility. The set of characterization techniques (XRD, ²⁷Al MAS NMR, N₂ physisorption, SEM, TEM, and Pyridine-FTIR) revealed the phase purity and combined structure of micro-mesopores after desilication. The zeolites were evaluated as catalysts for polystyrene pyrolysis, producing benzene, toluene and ethylbenzene, besides styrene monomers, and dimers. Without any catalyst, polystyrene produces only styrene monomers, dimers and trimers. The desilication increases the amount of Brønsted and Lewis sites and the external area, catalyzing the production of polyaromatics and naphthalene derivatives. The activation energy decreased for the catalyzed reactions, reflecting other reaction pathways.</p></div>","PeriodicalId":264,"journal":{"name":"Catalysis Today","volume":"444 ","pages":"Article 115010"},"PeriodicalIF":5.2,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142049610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Monitoring the dynamics of nanozeolite formation by combined in situ coherent small angle X-ray scattering techniques","authors":"Paulo R.A.F. Garcia ,&nbsp;Paloma Vinaches ,&nbsp;João-Paulo Zerba ,&nbsp;Tiago A. Kalile ,&nbsp;Amélie Rochet ,&nbsp;Sibele B. Pergher ,&nbsp;Florian Meneau","doi":"10.1016/j.cattod.2024.114992","DOIUrl":"10.1016/j.cattod.2024.114992","url":null,"abstract":"<div><p>Understanding the dynamics of zeolite formation is key to synthesising high-quality zeolitic materials with controllable properties, in order to develop more efficient and performant materials. X-ray photon correlation spectroscopy (XPCS) using coherent X-rays offers new possibilities for <em>in situ</em> observation of nano to micron-scale fluctuation dynamics during crystal growth. An <em>in situ</em> cell, which is capable of collecting time-resolved coherent X-ray scattering data under hydrothermal conditions has been developed and used to study, by <em>in situ</em> XPCS combined with small and wide angle X-ray scattering, zeolite formation and dynamics. Analysis of the results using two-time correlations enables to accurately identify the successive growth and crystallisation steps, revealing the dissolution process of the LTA topology during the SOD growth. This approach opens a powerful new avenue for studying the dynamics of nanomaterials formation, phase transitions and growth processes under <em>in situ</em> conditions that will enable profound insights into the nanoscale synthesis mechanisms.</p></div>","PeriodicalId":264,"journal":{"name":"Catalysis Today","volume":"443 ","pages":"Article 114992"},"PeriodicalIF":5.2,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0920586124004863/pdfft?md5=52dbec7b52817e9337eec905270badda&pid=1-s2.0-S0920586124004863-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142012749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SnO2-TiO2 materials for photocatalytic degradation of cationic dye under UV and visible light and a chitosan composite film investigation","authors":"Lourdes A. Etshindo ,&nbsp;Célia Sousa ,&nbsp;Priscila Tamiasso-Martinhon ,&nbsp;Marcos V. Colaço ,&nbsp;Alexandre R. Camara ,&nbsp;Angela S. Rocha","doi":"10.1016/j.cattod.2024.114995","DOIUrl":"10.1016/j.cattod.2024.114995","url":null,"abstract":"<div><p>The possibility of SnO₂ incorporation and immobilization as films forming composites opens new perspectives for TiO₂ to profit visible light and to facilitate the photocatalytic process, respectively. In this study, 0 %, 1 % and 10 % wt. of SnO₂ was incorporated into TiO₂ (SnO₂-TiO₂) by coprecipitation in a sol-gel method by ammonia addition, followed for calcination at 500 °C. The photocatalysts were characterized by N₂ adsorption-desorption, FTIR spectroscopy, XRD Rietveld refinement, TG-DTG, SEM-EDS, DRS and elemental analysis. The performance of all solids was evaluated in the photocatalytic degradation of the cationic dye methylene blue in aqueous phase, under visible and UV irradiation, at 25 °C for 2 h. The results showed that the incorporation of Sn into TiO₂ improved the textural properties and decreased the bandgap. All solids presented only TiO₂ typical diffractograms, with anatase as the main phase, but catalyst with 10 % SnO₂ presented also brookite phase, inferring that Sn atoms were incorporated into TiO₂ structure, corroborated by MEV results. All tin-based photocatalysts show high activity under UV and visible light, with the 10 % SnO₂ material reaching 83 % and 88 % degradation after 2 h under UV and visible radiation, respectively. This material was tested as an immobilized film, achieving 14 % of decolorization, and the reuse was also evaluated. Our investigation demonstrates that SnO₂-TiO₂ catalysts could be used to decompose a dye under UV and Visible light as powder in a batch reactor and immobilized as a composite film with chitosan, that opens new perspectives to facilitate the application using solar light.</p></div>","PeriodicalId":264,"journal":{"name":"Catalysis Today","volume":"444 ","pages":"Article 114995"},"PeriodicalIF":5.2,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142098292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Synthesis of NiZn-based paddle-wheel metal-organic framework and its use as a catalytic precursor for ethylene dimerization","authors":"Tatiana Zanette ,&nbsp;Yuri Miguel Variani ,&nbsp;Bruna Pes Nicola ,&nbsp;Silvia Gutiérrez-Tarriño ,&nbsp;Christian Cerezo-Navarrete ,&nbsp;Giovanni Agostini ,&nbsp;Pascual Oña-Burgos ,&nbsp;Christian Wittee Lopes ,&nbsp;Katia Bernardo-Gusmão","doi":"10.1016/j.cattod.2024.114988","DOIUrl":"10.1016/j.cattod.2024.114988","url":null,"abstract":"<div><p>A bimetallic pillared-layered MOF based on Ni and Zn with improved catalytic activity was synthesized and applied in the ethylene oligomerization reaction. According to the XANES spectra, the MOF possesses Ni in the 2+ oxidation state, a well-known active catalytic precursor in oligomerization systems. In addition, Ni and Zn oxide or metallic species were not identified, indicating the absence of impurity phases. µ-XRF and SEM-EDS techniques showed the homogeneous distribution of Ni and Zn species across the SBUs of the bimetallic MOF. Ni/Zn-MOF was applied in the ethylene oligomerization reaction using EASC as the co-catalyst, and the results were compared to its monometallic counterpart Ni-MOF. The bimetallic material Ni/Zn-MOF obtained a TOF corresponding to 135 ×10³ h⁻¹, which accounts for a 60 % increase in the catalytic activity achieved by Ni-MOF (85 ×10³ h⁻¹) under 15 bar of ethylene in a Parr reactor. Moreover, the results obtained in this work are remarkable compared to literature reports for Ni-based MOFs, demonstrating that the co-catalyst employed plays an important role in the catalytic activity. However, Ni/Zn-MOF showed a lower selectivity to α-C₄ oligomers (36 %) against 58 % obtained by Ni-MOF. According to the reuse tests conducted, the bimetallic MOF can be reused for up to two reactions (under 5 bar ethylene in a glass reactor), although presenting a considerable loss in activity due to the formation of metallic Ni.</p></div>","PeriodicalId":264,"journal":{"name":"Catalysis Today","volume":"444 ","pages":"Article 114988"},"PeriodicalIF":5.2,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142077084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fe2O3/γ-Al2O3 and NiO/γ-Al2O3 catalysts for the selective catalytic oxidation of ammonia","authors":"Gabriel V. Oliveira ,&nbsp;Vinícius de Macedo ,&nbsp;Ernesto A. Urquieta-González ,&nbsp;Zuy M. Magriotis ,&nbsp;Cristiane A. Pereira","doi":"10.1016/j.cattod.2024.114991","DOIUrl":"10.1016/j.cattod.2024.114991","url":null,"abstract":"<div><p>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.</p></div>","PeriodicalId":264,"journal":{"name":"Catalysis Today","volume":"444 ","pages":"Article 114991"},"PeriodicalIF":5.2,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142098155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Challenges, prospects and comprehensive evolution of zeolite-based materials for the catalytic conversion of glycerol: A review","authors":"Felipe Fernandes Barbosa ,&nbsp;Adonay R. Loiola ,&nbsp;Sibele B.C. Pergher ,&nbsp;Tiago Pinheiro Braga","doi":"10.1016/j.cattod.2024.114998","DOIUrl":"10.1016/j.cattod.2024.114998","url":null,"abstract":"<div><p>The energetic demands of modern society urge a transition that relies on alternative and sustainable sources. Among the available possibilities focused on mitigating the use of fossil fuels, the biodiesel industry stands out. However, the excess of glycerol generated as a coproduct still raises debate regarding how it could be better used. A well-established approach is the use of the platform molecule, i.e., glycerol, in the presence of heterogeneous catalysts to obtain added value products. Zeolites are well-known for their versatility in numerous applications, such as in the oil industry. Besides, different types of aluminosilicates are being studied in the catalytic conversion of glycerol to acrolein, acetol, acrylic acid, allyl alcohol, solketal, etc. This review addresses the general properties, fundaments, synergetic aspects, theoretical modeling, resistance, and coke formation, as well as the zeolites limitations that pose obstacles for those reactions. This highlights the importance of developing zeolite materials with specific acid sites, synchronizing their amount and strength with the pore interconnectivity so that reagents diffusion within the zeolitic channels can be maximized, leading to a decrease in the obstruction of active sites and pores caused by coke deposition. A number of modifications, including hierarchization, isomorphic substitution, acidity tuning, and additional phases (SMSI effect), have been reported as alternatives for improving the performance of glycerol conversion and the resistance to deactivation. Several developments involving reactional mechanisms, coke deposition, and catalysts applied to glycerol conversion have been the subject of studies centered on process optimization, which is translated into the development of solids more resistant to deactivation. Among the zeolites with the best catalytic performance, the following stand out: BEA, MCM-22, MFI, ITQ-2, SAPO-34, and ZSM-5. Some complex technical aspects still need to be better understood so that the scalability of the catalytic conversion of glycerol becomes economically feasible, thereby arousing the interest of both the public and private sectors.</p></div>","PeriodicalId":264,"journal":{"name":"Catalysis Today","volume":"444 ","pages":"Article 114998"},"PeriodicalIF":5.2,"publicationDate":"2024-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142049500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cyclohexane dehydrogenation: Critical evaluation of parameter estimation procedures for kinetic modeling","authors":"Roger Kober ,&nbsp;Marcio Schwaab ,&nbsp;Elisa Barbosa-Coutinho ,&nbsp;André Luis Alberton ,&nbsp;José Carlos Pinto","doi":"10.1016/j.cattod.2024.114993","DOIUrl":"10.1016/j.cattod.2024.114993","url":null,"abstract":"<div><p>In the present paper a comparison between different parameter estimation procedures commonly used for the kinetic modeling of chemical reaction is performed, based on experimental measurements of the cyclohexane dehydrogenation to benzene. The obtained results show that, when the Arrhenius equation parameters are estimated from estimates of the rate constant taken at different temperatures, larger parameter uncertainties and correlations are obtained, particularly when the variances of the experimental measurements are not considered during the estimation process. It is also observed that an apparent kinetic compensation effect occurs when the experimental data are separated according to the inlet partial pressure and catalyst mass in the reactor, mainly due to the existing and unavoidable experimental uncertainties and parameter correlations. Additionally, it is shown that larger uncertainties and correlations are obtained when the parameter estimates are computed through the differential method, which can also lead to poorer model predictions of the experimental data. Finally, it is shown that the simultaneous one-step estimation of all model parameters through the integral method and considering the available experimental uncertainties can provide the most accurate parameter estimates, making use of mathematical expressions that describe how variances of the experimental measurements depend on the experimental conditions.</p></div>","PeriodicalId":264,"journal":{"name":"Catalysis Today","volume":"444 ","pages":"Article 114993"},"PeriodicalIF":5.2,"publicationDate":"2024-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142098291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Green Synthesis of carbon quantum dots for enhancing photocatalytic activity: Hydrogen/oxygen evolution and dye photodegradation","authors":"Claudio W. Backes ,&nbsp;Felipe B. Reis ,&nbsp;Guilherme B. Strapasson ,&nbsp;Marcelo Assis ,&nbsp;Elson Longo ,&nbsp;Daniel E. Weibel","doi":"10.1016/j.cattod.2024.114996","DOIUrl":"10.1016/j.cattod.2024.114996","url":null,"abstract":"<div><p>Carbon quantum dots (CQDs) have recently attracted attention across various fields due to their small size, high conductivity, fluorescence emission, low toxicity, and other desirable characteristics. In this study, highly fluorescent CQDs with an average diameter of 3.7 nm were prepared via microwave irradiation using a standard commercial microwave oven and glycerol as solvent. Several cation promoters were examined for CQD synthesis, with copper ions ultimately chosen for comprehensive characterization and application. The CQDs were impregnated onto both commercially available and microwave-synthesized TiO₂ nanoparticles. The photocatalytic activity was evaluated with respect to the hydrogen and oxygen generation. Under the employed conditions, the oxygen evolution reaction (OER) exhibited over 12 times higher efficiency than the hydrogen evolution reaction (HER). The enhanced OER activity is attributed to the high electronic conductivity of the small Cu doped CQDs@TiO₂ (Cu-CQDs@TiO₂) facilitating an efficient electron transfer for the OER . Visible light activity (λ ≥ 400 nm) was demonstrated by photodegradation of the indigo carmine (IC) solution used as a model pollutant. Irradiation in the presence of the Cu-CQDs@TiO₂ photocatalyst resulted in complete degradation of the dye in less than 3 hours. The results presented here provide a promising methodology for designing high-performance photocatalysts based on environmentally friendly CQD syntheses. Crucial applications, from renewable energy production to environmental remediation, will benefit from strategies using the carbon abundance on Earth.</p></div>","PeriodicalId":264,"journal":{"name":"Catalysis Today","volume":"443 ","pages":"Article 114996"},"PeriodicalIF":5.2,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0920586124004905/pdfft?md5=3bb19f2b63d812c21c44c470794d472d&pid=1-s2.0-S0920586124004905-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142040272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of the La/Ce ratio on La-Ce oxides promoted by Sr in the methane oxidative coupling reaction","authors":"G.L. Catuzo ,&nbsp;Y.L. de Lima ,&nbsp;D.D. Petrolini ,&nbsp;E.M. Assaf","doi":"10.1016/j.cattod.2024.114994","DOIUrl":"10.1016/j.cattod.2024.114994","url":null,"abstract":"<div><p>The high methane availability and its significant role as a greenhouse gas have led the scientific community to pursue methods for its use. This paper proposes the usage of the oxidative coupling of methane (OCM) as a promising path to transform methane directly into value-added hydrocarbons, mostly ethylene, which serves as a crucial compound in the petrochemical sector. An efficient OCM catalyst should contain substantial basicity and oxygen vacancies for providing surface electrophilic oxygen species, such as superoxides and peroxides, instrumental for boosting selectivity towards C₂ products. Mixed lanthanum-cerium oxide (La-Ce) catalysts have emerged as strong candidates in OCM due to their high thermal stability, oxygen mobility, and high alkalinity. In this study, they were prepared through a surfactant-assisted hydrothermal method with different La/Ce ratios for fine-tuning their basic properties and promoting oxygen mobility on the surface of the catalysts. Samples followed a volcano-shaped relationship between C₂ yield and La content, with optimal performance at a La/Ce molar ratio of 2.1, attributed to the interplay between the high amount of basic sites and oxygen vacancies, increasing the presence of superoxide species over lattice oxygen. Moreover, the Sr-promoted catalyst showed high density of strong basic sites while preserving the reactive oxygen species, achieving 20 % CH₄ conversion, with 57 % C₂ compounds selectivity at 750 °C and GHSV of 18.000 mL.g_cat⁻¹.h⁻¹.</p></div>","PeriodicalId":264,"journal":{"name":"Catalysis Today","volume":"444 ","pages":"Article 114994"},"PeriodicalIF":5.2,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142076816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}