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Supported Metal and Metal Oxide Catalysts by Sol-Gel Chemistry: Synthesis...
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Supported Metal and Metal Oxide Catalysts by Sol-Gel Chemistry: Synthesis and Applications

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Catalytic Materials".

Deadline for manuscript submissions: closed (28 February 2019) | Viewed by 42334

Special Issue Editor

Dr. Serena Esposito

E-Mail Website
Guest Editor
Department of Civil and Mechanical Engineering, University of Cassino and Southern Latium, Via G. Di Biasio 43, 03043 Cassino (FR), Italy
Interests: sol–gel synthesis; porous materials; surface chemistry; oxide-based catalysts; metal-ceramic nanomaterials; zeolite precursors
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Sol-gel method has been recognized as valuable procedure to design advanced catalytic formulations, based on metal and metal oxide nanostructure. Sol-gel chemistry originated with the hydrolysis and condensation of metal alkoxides, although it can also occur between hydrated metal species. By trapping the “randomness of the solution state” and thereby ensuring atomic level mixing of reagents, the sol-gel method is a unique technique for materials synthesis. Low-temperature chemistry, reproducibility and high surface to volume ratios of obtained products are features that add merit to this technology. Nowadays, the term ‘sol-gel’ is used more broadly as covering the synthesis of solid materials, such as metal oxides, from solution-state precursors. The great advantage of tailoring the physicochemical properties of these materials through mastering the synthesis parameters have triggered a progressive development of different and fascinating procedure exploring new molecular precursors, chelating agents and templates.

The upcoming Special Issue, entitled “Supported Metal and Metal Oxide Catalysts by Sol-Gel Chemistry: Synthesis and Applications” aims to cover an overview of the sol-gel synthesis of tailored and multifunctional materials and their application in the main domain of heterogeneous catalysis.

Dr. Serena Esposito
Guest Editor

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Keywords

  • Sol-Gel synthesis
  • Xerogel
  • Porous oxide
  • Aerogel
  • Solid acid catalyst
  • Ordered Mesoporous Sol–Gel Materials
  • Selective partial oxidation reactions
  • Biomass conversion
  • Total oxidation reaction
  • Green chemistry
  • Bio-catalysts
  • Nanostructure

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Published Papers (7 papers)

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Research

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14 pages, 6452 KiB  
Article
Application of Reverse Micelle Sol–Gel Synthesis for Bulk Doping and Heteroatoms Surface Enrichment in Mo-Doped TiO2 Nanoparticles
by Roberto Nasi, Serena Esposito, Francesca S. Freyria, Marco Armandi, Tanveer A. Gadhi, Simelys Hernandez, Paola Rivolo, Nicoletta Ditaranto and Barbara Bonelli
Materials 2019, 12(6), 937; https://doi.org/10.3390/ma12060937 - 21 Mar 2019
Cited by 27 | Viewed by 3922
Abstract
TiO2 nanoparticles containing 0.0, 1.0, 5.0, and 10.0 wt.% Mo were prepared by a reverse micelle template assisted sol–gel method allowing the dispersion of Mo atoms in the TiO2 matrix. Their textural and surface properties were characterized by means of X-ray [...] Read more.
TiO2 nanoparticles containing 0.0, 1.0, 5.0, and 10.0 wt.% Mo were prepared by a reverse micelle template assisted sol–gel method allowing the dispersion of Mo atoms in the TiO2 matrix. Their textural and surface properties were characterized by means of X-ray powder diffraction, micro-Raman spectroscopy, N2 adsorption/desorption isotherms at −196 °C, energy dispersive X-ray analysis coupled to field emission scanning electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance UV–Vis spectroscopy, and ζ-potential measurement. The photocatalytic degradation of Rhodamine B (under visible light and low irradiance) in water was used as a test reaction as well. The ensemble of the obtained experimental results was analyzed in order to discover the actual state of Mo in the final materials, showing the occurrence of both bulk doping and Mo surface species, with progressive segregation of MoOx species occurring only at a higher Mo content. Full article
(This article belongs to the Special Issue Supported Metal and Metal Oxide Catalysts by Sol-Gel Chemistry: Synthesis and Applications)
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10 pages, 1047 KiB  
Article
Room Temperature Synthesis of V-Doped TiO2 and Its Photocatalytic Activity in the Removal of Caffeine under UV Irradiation
by Olga Sacco, Diana Sannino, Mariantonietta Matarangolo and Vincenzo Vaiano
Materials 2019, 12(6), 911; https://doi.org/10.3390/ma12060911 - 19 Mar 2019
Cited by 23 | Viewed by 3309
Abstract
In this work, the influence of simple acids in the room temperature sol-gel synthesis of TiO2 was investigated and the efficiency of prepared photocatalysts was evaluated in the removal of caffeine. To improve the photoactivity of TiO2, vanadium-doped TiO2 [...] Read more.
In this work, the influence of simple acids in the room temperature sol-gel synthesis of TiO2 was investigated and the efficiency of prepared photocatalysts was evaluated in the removal of caffeine. To improve the photoactivity of TiO2, vanadium-doped TiO2 (VTiO2) samples were obtained starting from different amount of vanadyl sulphate as a dopant source. The samples were centrifuged, washed and finally dried at room temperature, and no calcination step was carried out. The prepared photocatalysts were characterized by different techniques (X-ray powder diffraction (XRD), specific surface area (SSA), ultraviolet-visible diffuse reflectance spectra (UV-vis DRS) and Raman). VTiO2 photocatalysts were tested in the photocatalytic removal of aqueous solutions containing caffeine. The photocatalytic tests were carried out in a recirculating batch cylindrical photoreactor irradiated by a UV LEDs strip (nominal power of 12 W and wavelength emission peak at about 365 nm) surrounding the external surface of the reactor. The optimized VTiO2 photocatalyst was able to reach a caffeine degradation of about 96% after 360 min of UV light irradiation with a total organic carbon (TOC) removal of 72%. Full article
(This article belongs to the Special Issue Supported Metal and Metal Oxide Catalysts by Sol-Gel Chemistry: Synthesis and Applications)
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14 pages, 3175 KiB  
Article
Structured Monolithic Catalysts vs. Fixed Bed for the Oxidative Dehydrogenation of Propane
by Ilenia Rossetti, Elnaz Bahadori, Antonio Tripodi and Gianguido Ramis
Materials 2019, 12(6), 884; https://doi.org/10.3390/ma12060884 - 16 Mar 2019
Cited by 3 | Viewed by 3046
Abstract
The deposition of V-based catalysts for the oxidative dehydrogenation of propane to propene on cordierite honeycomb monoliths was optimised as a strategy to decrease the contact time in a structured reactor with respect to a conventional fixed bed one. 10 wt% VOx [...] Read more.
The deposition of V-based catalysts for the oxidative dehydrogenation of propane to propene on cordierite honeycomb monoliths was optimised as a strategy to decrease the contact time in a structured reactor with respect to a conventional fixed bed one. 10 wt% VOx supported over SiO2 or Al2O3 were used as catalysts, deposed over the monolith using silica or alumina as primer, respectively. Both the alumina supported catalyst and the bohemite primer precursor were effectively deposed by dip-coating from stable powder suspensions, whereas insufficient adhesion was obtained when loading pre-synthesised SiO2 over the cordierite. A new method based on sol-gel production of SiO2 from tetraethylortosilicate (TEOS) over the monolith surface was set up. A correlation was derived for the prevision of the amount of silica deposed depending on the amount of TEOS. Both primer and catalyst loading were optimised as for uniformity and stability of the coating and resulted 0.5–1 wt % primer and 0.15 wt % of catalyst. Activity testing confirmed the strong improvement of propene productivity by increasing the time factor (i.e. Ncm3 of flowing reactant/min gcat), which ended in a one order of magnitude increase of productivity for the honeycomb-supported samples with respect to the fixed bed configuration. Full article
(This article belongs to the Special Issue Supported Metal and Metal Oxide Catalysts by Sol-Gel Chemistry: Synthesis and Applications)
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17 pages, 4602 KiB  
Article
Behavior of Molybdenum–Vanadium Mixed Oxides in Selective Oxidation and Disproportionation of Toluene
by Gheorghita Mitran, Florentina Neaţu, Octavian D. Pavel, Mihaela M. Trandafir and Mihaela Florea
Materials 2019, 12(5), 748; https://doi.org/10.3390/ma12050748 - 5 Mar 2019
Cited by 12 | Viewed by 3887
Abstract
This study deals with the behavior of molybdenum–vanadium (Mo/V) mixed oxides catalysts in both disproportionation and selective oxidation of toluene. Samples containing different Mo/V ratios were prepared by a modified method using tetradecyltrimethylammonium bromide and acetic acid. The catalysts were characterized using several [...] Read more.
This study deals with the behavior of molybdenum–vanadium (Mo/V) mixed oxides catalysts in both disproportionation and selective oxidation of toluene. Samples containing different Mo/V ratios were prepared by a modified method using tetradecyltrimethylammonium bromide and acetic acid. The catalysts were characterized using several techniques: nitrogen adsorption–desorption isotherms, X-Ray diffraction (XRD), ammonia temperature-programmed desorption (TPD-NH3), temperature-programmed reduction by hydrogen (H2-TPR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier-transform infrared-spectroscopy (FTIR) and ultraviolet-visible spectroscopies (UV–VIS). The XRD results evidenced the presence of orthorhombic α-MoO3 and V2O5 phases, as well as monoclinic β-MoO3 and V2MoO8 phases, their abundance depending on the Mo to V ratio, while the TPD-NH3 emphasized that, the total amount of the acid sites diminished with the increase of the Mo loading. The TPR investigations indicated that the samples with higher Mo/V ratio possess a higher reducibility. The main findings of this study led to the conclusion that the presence of strong acid sites afforded a high conversion in toluene disproportionation (Mo/V = 1), while a higher reducibility is a prerequisite to accomplishing high conversion in toluene oxidation (Mo/V = 2). The catalyst with Mo/V = 1 acquires the best yield to xylenes from the toluene disproportionation reaction, while the catalyst with Mo/V = 0.33 presents the highest yield to benzaldehyde. Full article
(This article belongs to the Special Issue Supported Metal and Metal Oxide Catalysts by Sol-Gel Chemistry: Synthesis and Applications)
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14 pages, 1824 KiB  
Article
Efficient Catalytic Production of Biodiesel with Acid-Base Bifunctional Rod-Like Ca-B Oxides by the Sol-Gel Approach
by Anping Wang, Hu Li, Heng Zhang, Hu Pan and Song Yang
Materials 2019, 12(1), 83; https://doi.org/10.3390/ma12010083 - 27 Dec 2018
Cited by 29 | Viewed by 3635
Abstract
The search for acid-base bifunctional catalysts has become a hot topic in the preparation of biofuels from renewable resources. In the present work, a series of novel acid-base bifunctional metal-boron catalysts were successfully prepared by a sol-gel method and characterized by XRD, IR, [...] Read more.
The search for acid-base bifunctional catalysts has become a hot topic in the preparation of biofuels from renewable resources. In the present work, a series of novel acid-base bifunctional metal-boron catalysts were successfully prepared by a sol-gel method and characterized by XRD, IR, SEM, TEM, TGA, BET, and TPD. Among those bifunctional solid materials, the Ca-B(700) catalyst had the highest density of both acid and base sites and showed excellent catalytic performance in the production of biodiesel from nonedible oils with high acid value. Under the optimal reaction conditions of 20/1 methanol/oil mole ratio and 4 wt % catalyst dosage at 105 °C for 2 h, a high biodiesel yield of 96.0% could be obtained from Jatropha curcas oil in one-pot. In addition, Ca-B(700) was also applicable to producing biodiesel from Firmiana platanifolia L.f. oil in a relatively low acid value, with an almost quantitative yield (98.5%) at 65 °C after 2 h. The Ca-B(700) catalyst had good stability and reusability, which is a promising acid-base bifunctional catalytic material for the preparation of biodiesel. Full article
(This article belongs to the Special Issue Supported Metal and Metal Oxide Catalysts by Sol-Gel Chemistry: Synthesis and Applications)
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12 pages, 3883 KiB  
Article
Boosted Visible-Light Photodegradation of Methylene Blue by V and Co Co-Doped TiO2
by Tianping Lv, Jianhong Zhao, Mingpeng Chen, Kaiyuan Shen, Dongming Zhang, Jin Zhang, Genlin Zhang and Qingju Liu
Materials 2018, 11(10), 1946; https://doi.org/10.3390/ma11101946 - 11 Oct 2018
Cited by 47 | Viewed by 3760
Abstract
In this work, TiO2 photocatalysts, co-doped with transition metal ions vanadium (V) and cobalt (Co) ((V,Co)–TiO2), were synthesized by the sol–gel method. The synthesized photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen [...] Read more.
In this work, TiO2 photocatalysts, co-doped with transition metal ions vanadium (V) and cobalt (Co) ((V,Co)–TiO2), were synthesized by the sol–gel method. The synthesized photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption and desorption measurement, UV-Vis absorption and photoluminescence spectrum (PL) spectra. The results show that V and Co co-doping has significant effects on sample average crystalline grain size, absorption spectrum, recombination efficiency of photo-induced electron-hole pairs (EHPs), and photocatalytic degradation efficiency of methylene blue (MB). (V,Co)–TiO2 photocatalyst exhibits an obvious red shift of the absorption edge to 475 nm. Photocatalytic degradation rate of (V,Co)–TiO2 sample for MB in 60 min is 92.12% under a Xe lamp with a cut-off filter (λ > 400 nm), which is significantly higher than 56.55% of P25 under the same conditions. The first principles calculation results show that V and Co ions doping introduces several impurity energy levels, which can modulate the location of the valence band and conduction band. An obvious lattice distortion is produced in the meantime, resulting in the decrease in photo-generated EHP recombination. Thus, (V,Co)–TiO2 photocatalyst performance is significantly improved. Full article
(This article belongs to the Special Issue Supported Metal and Metal Oxide Catalysts by Sol-Gel Chemistry: Synthesis and Applications)
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Review

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25 pages, 11010 KiB  
Review
“Traditional” Sol-Gel Chemistry as a Powerful Tool for the Preparation of Supported Metal and Metal Oxide Catalysts
by Serena Esposito
Materials 2019, 12(4), 668; https://doi.org/10.3390/ma12040668 - 23 Feb 2019
Cited by 231 | Viewed by 19885
Abstract
The sol-gel method is an attractive synthetic approach in the design of advanced catalytic formulations that are based on metal and metal oxide with high degree of structural and compositional homogeneity. Nowadays, though it originated with the hydrolysis and condensation of metal alkoxides, [...] Read more.
The sol-gel method is an attractive synthetic approach in the design of advanced catalytic formulations that are based on metal and metal oxide with high degree of structural and compositional homogeneity. Nowadays, though it originated with the hydrolysis and condensation of metal alkoxides, sol-gel chemistry gathers plenty of fascinating strategies to prepare materials from solution state precursors. Low temperature chemistry, reproducibility, and high surface to volume ratios of obtained products are features that add merit to this technology. The development of different and fascinating procedure was fostered by the availability of new molecular precursors, chelating agents and templates, with the great advantage of tailoring the physico-chemical properties of the materials through the manipulation of the synthesis conditions. The aim of this review is to present an overview of the “traditional” sol-gel synthesis of tailored and multifunctional inorganic materials and their application in the main domain of heterogeneous catalysis. One of the main achievements is to stress the versatility of sol-gel preparation by highlighting its advantage over other preparation methods through some specific examples of the synthesis of catalysts. Full article
(This article belongs to the Special Issue Supported Metal and Metal Oxide Catalysts by Sol-Gel Chemistry: Synthesis and Applications)
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