Special Issue "Structure–Activity Relationships in Catalysis"

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Environmental Catalysis".

Deadline for manuscript submissions: closed (30 November 2018).

Special Issue Editor

Guest Editor
Dr. Anna Maria Venezia Website E-Mail
Institute of Nanostructured Materials (ISMN) of CNR (Consiglio Nazionale delle Ricerche), Via Ugo La Malfa 153, 90146 Palermo, Italy
Interests: Surface Science; X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES); Heterogeneous Catalysis; Supported metal catalysts

Special Issue Information

Dear Colleagues,

Catalysis, a technology devoted to the modification of chemical reactions with increased conversion and selectivity, relies very much on the structural design and on the surface properties of the materials used as catalysts. Any catalytic process involves a sequence of elementary steps, including adsorption, surface diffusion, chemical rearrangement of the adsorbed reaction intermediate and desorption of the products. The nature of the catalyst, in terms of chemical formulation, physical, textural and morphology properties, strongly affects each of these steps. Understanding the relationship between a single feature of a catalyst and its activity behavior is mandatory in order to regard catalysis as an exact science rather than as a trial-and-error approach.

The present Special Issue will be a compendium of original research papers and reviews, focused on special aspects of the structure–activity relationship in chemical reactions relevant to both industrial and environmental catalysis. The development of new materials, new synthetic routes, advanced characterization tools and modelling are among the included topics.

Dr. Anna Maria Venezia
Guest Editor

Manuscript Submission Information

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Keywords

  • Support effects
  • Particle size effects
  • Metal-support charge transfer
  • Alloying
  • Core-shell catalysts
  • Surface properties

Published Papers (5 papers)

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Research

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Open AccessArticle
The ZSM-5-Catalyzed Oxidation of Benzene to Phenol with N2O: Effect of Lewis Acid Sites
Catalysts 2019, 9(1), 44; https://doi.org/10.3390/catal9010044 - 04 Jan 2019
Abstract
The oxidation of benzene to phenol (BTOP) with N2O as the oxidant has been studied with a variety of Fe/ZSM-5 catalysts. The literature has conclusively proven that Fe2+ sites are the active sites. However, some studies have suggested that the [...] Read more.
The oxidation of benzene to phenol (BTOP) with N2O as the oxidant has been studied with a variety of Fe/ZSM-5 catalysts. The literature has conclusively proven that Fe2+ sites are the active sites. However, some studies have suggested that the Lewis acidic sites (LAS) are responsible for the generation of the active chemisorbed oxygen. Nevertheless, there is no clear relationship between the LAS and the N2O selectivity to phenol. In an effort to elucidate the effects of LAS on BTOP with various ZSM-5 catalysts, we investigated the initial N2O selectivity to phenol. Here we show that the initial N2O selectivity to phenol is negative with the amount of LAS over a certain range. The catalyst H-ZSM-5-ST (H-ZSM-5 treated with water vapor) showed a remarkable initial N2O selectivity to phenol as high as 95.9% with a 0.021 mmol g−1 LAS concentration on the surface of the catalyst, while the Fe/ZSM-5 catalyst demonstrated the lowest initial N2O selectivity to phenol (11.7%) with the highest LAS concentration (0.137 mmol g−1). Another remarkable feature is that steaming was more effective than Fe ion exchange and high temperature calcining. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), N2-adsorption-desorption, UV-vis, NH3-TPD and pyridine Fourier transform infrared (FT-IR) techniques. Our results demonstrate how the concentration of LAS is likely to affect the initial N2O selectivity to phenol within a certain range (0.021–0.137 mmol g−1). This research has demonstrated the synergy between the active Fe2+ sites and LAS. Full article
(This article belongs to the Special Issue Structure–Activity Relationships in Catalysis)
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Open AccessArticle
Structure–Activity Relationship Study of Mn/Fe Ratio Effects on Mn−Fe−Ce−Ox/γ-Al2O3 Nanocatalyst for NO Oxidation and Fast SCR Reaction
Catalysts 2018, 8(12), 642; https://doi.org/10.3390/catal8120642 - 09 Dec 2018
Cited by 2
Abstract
A series of Mn−Fe−Ce−Ox/γ-Al2O3 nanocatalysts were synthesized with different Mn/Fe ratios for the catalytic oxidation of NO into NO2 and the catalytic elimination of NOx via fast selective catalytic reduction (SCR) reaction. The effects [...] Read more.
A series of Mn−Fe−Ce−Ox/γ-Al2O3 nanocatalysts were synthesized with different Mn/Fe ratios for the catalytic oxidation of NO into NO2 and the catalytic elimination of NOx via fast selective catalytic reduction (SCR) reaction. The effects of Mn/Fe ratio on the physicochemical properties of the samples were analyzed by means of various techniques including N2 adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H2-temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD) and NO-TPD, meanwhile, their catalytic performance was also evaluated and compared. Multiple characterizations revealed that the catalytic performance was highly dependent on the phase composition. The Mn15Fe15−Ce/Al sample with the Mn/Fe molar ratio of 1.0 presented the optimal structure characteristic among all tested samples, with the largest surface area, increased active components distributions, the reduced crystallinity and diminished particle sizes. In the meantime, the ratios of Mn4+/Mnn+, Fe2+/Fen+ and Ce3+/Cen+ in Mn15Fe15−Ce/Al samples were improved, which could enhance the redox capacity and increase the quantity of chemisorbed oxygen and oxygen vacancy, thus facilitating NO oxidation into NO2 and eventually promoting the fast SCR reaction. In accord with the structure results, the Mn15Fe15−Ce/Al sample exhibited the highest NO oxidation rate of 64.2% at 350 °C and the broadest temperature window of 75–350 °C with the NOx conversion >90%. Based on the structure–activity relationship discussion, the catalytic mechanism over the Mn−Fe−Ce ternary components supported by γ-Al2O3 were proposed. Overall, it was believed that the optimization of Mn/Fe ratio in Mn−Fe−Ce/Al nanocatalyst was an extremely effective method to improve the structure–activity relationships for NO pre-oxidation and the fast SCR reaction. Full article
(This article belongs to the Special Issue Structure–Activity Relationships in Catalysis)
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Open AccessArticle
Effect of Y Modified Ceria Support in Mono and Bimetallic Pd–Au Catalysts for Complete Benzene Oxidation
Catalysts 2018, 8(7), 283; https://doi.org/10.3390/catal8070283 - 16 Jul 2018
Cited by 4
Abstract
Mono metallic and bimetallic Pd (1 wt. %)–Au (3 wt. %) catalysts were prepared using two ceria supports doped with 1 wt. % Y2O3. Yttrium was added by impregnation or co-precipitation. The catalyst synthesis was carried out by deposition–precipitation [...] Read more.
Mono metallic and bimetallic Pd (1 wt. %)–Au (3 wt. %) catalysts were prepared using two ceria supports doped with 1 wt. % Y2O3. Yttrium was added by impregnation or co-precipitation. The catalyst synthesis was carried out by deposition–precipitation method, with sequential deposition–precipitation of palladium over previously loaded gold in the case of the bimetallic samples. The obtained materials, characterized by X-ray powder diffraction (XRD), High resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (TPR) techniques, were tested in the complete benzene oxidation (CBO). The results of the characterization analyses and the catalytic performance pointed to a close relationship between structural, redox, and catalytic properties of mono and bimetallic catalysts. Among the monometallic systems, Pd catalysts were more active as compared to the corresponding Au catalysts. The bimetallic systems exhibited the best combustion activity. In particular, over Pd–Au supported on Y-impregnated ceria, 100% of benzene conversion towards total oxidation at the temperature of 150 °C was obtained. Comparison of surface sensitive XPS results of fresh and spent catalysts ascertained the redox character of the reaction. Full article
(This article belongs to the Special Issue Structure–Activity Relationships in Catalysis)
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Open AccessArticle
Effects of Synthesis on the Structural Properties and Methane Partial Oxidation Activity of Ni/CeO2 Catalyst
Catalysts 2018, 8(5), 220; https://doi.org/10.3390/catal8050220 - 21 May 2018
Cited by 4
Abstract
Nickel catalysts supported on homemade CeO2 oxide were prepared by two procedures intending to achieve different degree of metal-support interaction. One method consisted of a co-precipitation that was assisted by microwave; the other method was based on a modified wetness impregnation in [...] Read more.
Nickel catalysts supported on homemade CeO2 oxide were prepared by two procedures intending to achieve different degree of metal-support interaction. One method consisted of a co-precipitation that was assisted by microwave; the other method was based on a modified wetness impregnation in the presence of the organic complexing ligand, nitrilotriacetic acid (NTA). The support and catalysts were characterized by temperature programmed reduction (TPR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. Significant differences in the structure, in redox properties and in the elemental surface composition emerged. The catalytic behavior in the partial oxidation of methane was tested at atmospheric pressure, in a range of temperature between 400–800 °C, using diluted feed gas mixture with CH4/O2 = 2 and GHSV= 60,000 mL g−1 h−1. Moreover, the effect of the catalyst reduction pretreatment was investigated. The better catalytic performance of the microwave-assisted sample as compared to the NTA prepared sample was attributed to the stronger interaction of nickel with CeO2. Indeed, according to the structural and reducibility results, an adequate electronic contact between the metal and the support favors the formation of oxygen vacancies of ceria and inhibits the sintering of the catalyst active species, with an improvement of the catalytic performance. Full article
(This article belongs to the Special Issue Structure–Activity Relationships in Catalysis)
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Review

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Open AccessFeature PaperReview
Recent Insights in Transition Metal Sulfide Hydrodesulfurization Catalysts for the Production of Ultra Low Sulfur Diesel: A Short Review
Catalysts 2019, 9(1), 87; https://doi.org/10.3390/catal9010087 - 15 Jan 2019
Cited by 2
Abstract
The literature from the past few years dealing with hydrodesulfurization catalysts to deeply remove the sulfur-containing compounds in fuels is reviewed in this communication. We focus on the typical transition metal sulfides (TMS) Ni/Co-promoted Mo, W-based bi- and tri-metallic catalysts for selective removal [...] Read more.
The literature from the past few years dealing with hydrodesulfurization catalysts to deeply remove the sulfur-containing compounds in fuels is reviewed in this communication. We focus on the typical transition metal sulfides (TMS) Ni/Co-promoted Mo, W-based bi- and tri-metallic catalysts for selective removal of sulfur from typical refractory compounds. This review is separated into three very specific topics of the catalysts to produce ultra-low sulfur diesel. The first issue is the supported catalysts; the second, the self-supported or unsupported catalysts and finally, a brief discussion about the theoretical studies. We also inspect some details about the effect of support, the use of organic and inorganic additives and aspects related to the preparation of unsupported catalysts. We discuss some hot topics and details of the unsupported catalyst preparation that could influence the sulfur removal capacity of specific systems. Parameters such as surface acidity, dispersion, morphological changes of the active phases, and the promotion effect are the common factors discussed in the vast majority of present-day research. We conclude from this review that hydrodesulfurization performance of TMS catalysts supported or unsupported may be improved by using new methodologies, both experimental and theoretical, to fulfill the societal needs of ultra-low sulfur fuels, which more stringent future regulations will require. Full article
(This article belongs to the Special Issue Structure–Activity Relationships in Catalysis)
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