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Effect of Surface Properties and Mobility in Chemical Reactions and Catalysis

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

Deadline for manuscript submissions: closed (31 May 2022) | Viewed by 11544

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Special Issue Editor

Prof. Dr. Antonio Gil Bravo

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INAMAT^2-Departamento de Ciencias, Edificio de los Acebos, Universidad Pública de Navarra, Campus de Arrosadía, 31006 Pamplona, Spain
Interests: preparation, characterization, and catalytic activity of metal-supported catalysts; surface properties of solids; pollutants adsorption; environmental management; industrial waste valorization
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Special Issue Information

Dear Colleagues,

When the surface of a solid is exposed to a mixture of gases or liquids that would not react in the liquid or gas phases, adsorption can promote the reaction kinetics for at least two reasons: it increases the local concentration of the reactants on the surface, or it attracts one of the reactants or possibly both, generating a state that lowers the activation energy barrier due to the presence of active sites. These are the two simple basic principles on which catalysis is based.

Despite this apparent simplicity, there are many questions behind the notion of catalytic activity: What is the physical meaning of the concept of “active site”? How does the distribution and size of the “active site” influence on the surface affect the catalytic result? What is the role of surface diffusion and porosity? How do the chemical properties of the support/catalyst affect the catalytic result? Is it possible to differentiate the bifunctional character of a catalyst? These and many other questions will be dealt in this Special Issue.

Prof. Dr. Antonio Gil Bravo
Guest Editor

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Keywords

heterogeneous catalysis
textural properties
surface properties
active site
supported catalysts
chemical surface characterization
metal dispersion
species mobility
spillover
mobility
chemical and physical adsorption
remote control
stability

Published Papers (4 papers)

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Research

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12 pages, 2234 KiB

Open AccessArticle

Solketal Removal from Aqueous Solutions Using Activated Carbon and a Metal–Organic Framework as Adsorbents

by Leticia Santamaría, Sophia A. Korili and Antonio Gil

Materials 2021, 14(22), 6852; https://doi.org/10.3390/ma14226852 - 13 Nov 2021

Cited by 2 | Viewed by 1237

Abstract

The worldwide rise in biodiesel production has generated an excess of glycerol, a byproduct of the process. One of the most interesting alternative uses of glycerol is the production of solketal, a bioadditive that can improve the properties of both diesel and gasoline fuels. Even with its promising future, not much research has been performed on its toxicity in aqueous environments. In this work, solketal adsorption has been tested with two different commercial adsorbents: an activated carbon (Hydrodarco 3000) and a metal–organic framework (MIL-53). Diclofenac and caffeine were also chosen as emerging contaminants for comparison purposes. The effect of various parameters, such as the adsorbent mass or initial concentration of pollutants, has been studied. Adsorption kinetics with a better fit to a pseudo-second-order model, intraparticle diffusion, and effective diffusion coefficient were studied as well. Various isotherm equation models were employed to study the equilibrium process. The results obtained indicate that activated carbon is more effective in removing solketal from aqueous solutions than the metal–organic framework. Full article

(This article belongs to the Special Issue Effect of Surface Properties and Mobility in Chemical Reactions and Catalysis)

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23 pages, 4336 KiB

Open AccessArticle

Effect of Calcination Temperature and Chemical Composition of PAN-Derived Carbon Microfibers on N₂, CO₂, and CH₄ Adsorption

by Reyna Ojeda-López, Guadalupe Ramos-Sánchez, Cinthia García-Mendoza, Diana C. S. Azevedo, Ariel Guzmán-Vargas and Carlos Felipe

Materials 2021, 14(14), 3914; https://doi.org/10.3390/ma14143914 - 13 Jul 2021

Cited by 10 | Viewed by 2178

Abstract

This work investigates the interplay of carbonization temperature and the chemical composition of carbon microfibers (CMFs), and their impact on the equilibration time and adsorption of three molecules (N₂, CO₂, and CH₄). PAN derived CMFs were synthesized by electrospinning and calcined at three distinct temperatures (600, 700 and 800 °C), which led to samples with different textural and chemical properties assessed by FTIR, TGA/DTA, XRD, Raman, TEM, XPS, and N₂ adsorption. We examine why samples calcined at low/moderate temperatures (600 and 700 °C) show an open hysteresis loop in nitrogen adsorption/desorption isotherms at −196.15 °C. The equilibrium time in adsorption measurements is nearly the same for these samples, despite their distinct chemical compositions. Increasing the equilibrium time did not allow for the closure of the hysteresis loop, but by rising the analysis temperature this was achieved. By means of the isosteric enthalpy of adsorption measurements and ab initio calculations, adsorbent/adsorbate interactions for CO₂, CH₄ and N₂ were found to be inversely proportional to the temperature of carbonization of the samples (CMF-600 > CMF-700 > CMF-800). The enhancement of adsorbent/adsorbate interaction at lower carbonization temperatures is directly related to the presence of nitrogen and oxygen functional groups on the surface of CMFs. Nonetheless, a higher concentration of heteroatoms also causes: (i) a reduction in the adsorption capacity of CO₂ and CH₄ and (ii) open hysteresis loops in N₂ adsorption at cryogenic temperatures. Therefore, the calcination of PAN derived microfibers at temperatures above 800 °C is recommended, which results in materials with suitable micropore volume and a low content of surface heteroatoms, leading to high CO₂ uptake while keeping acceptable selectivity with regards to CH₄ and moderate adsorption enthalpies. Full article

(This article belongs to the Special Issue Effect of Surface Properties and Mobility in Chemical Reactions and Catalysis)

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Review

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44 pages, 10373 KiB

Open AccessReview

Progress and Recent Strategies in the Synthesis and Catalytic Applications of Perovskites Based on Lanthanum and Aluminum

by Helir Joseph Muñoz, Sophia A. Korili and Antonio Gil

Materials 2022, 15(9), 3288; https://doi.org/10.3390/ma15093288 - 04 May 2022

Cited by 20 | Viewed by 2971

Abstract

Lanthanum aluminate-based perovskite (LaAlO₃) has excellent stability at high temperatures, low toxicity, and high chemical resistance and also offers wide versatility to the substitution of La³⁺ and Al³⁺, thus, allowing it to be applied as a catalyst, nano-adsorbent, sensor, and microwave dielectric resonator, amongst other equally important uses. As such, LaAlO₃ perovskites have gained importance in recent years. This review considers the extensive literature of the past 10 years on the synthesis and catalytic applications of perovskites based on lanthanum and aluminum (LaAlO₃). The aim is, first, to provide an overview of the structure, properties, and classification of perovskites. Secondly, the most recent advances in synthetic methods, such as solid-state methods, solution-mediated methods (co-precipitation, sol–gel, and Pechini synthesis), thermal treatments (combustion, microwave, and freeze drying), and hydrothermal and solvothermal methods, are also discussed. The most recent energetic catalytic applications (the dry and steam reforming of methane; steam reforming of toluene, glycerol, and ethanol; and oxidative coupling of methane, amongst others) using these functional materials are also addressed. Finally, the synthetic challenges, advantages, and limitations associated with the preparation methods and catalytic applications are discussed. Full article

(This article belongs to the Special Issue Effect of Surface Properties and Mobility in Chemical Reactions and Catalysis)

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20 pages, 1717 KiB

Open AccessReview

Hydrothermal Liquefaction of Biomass as One of the Most Promising Alternatives for the Synthesis of Advanced Liquid Biofuels: A Review

by Lucía Grande, Ivan Pedroarena, Sophia A. Korili and Antonio Gil

Materials 2021, 14(18), 5286; https://doi.org/10.3390/ma14185286 - 14 Sep 2021

Cited by 29 | Viewed by 4367

Abstract

The use of biofuels offers advantages over existing fuels because they come from renewable sources, they are biodegradable, their storage and transport are safer, and their emissions into the atmosphere are lower. Biomass is one of the most promising sustainable energy sources with a wide variety of organic materials as raw material. Chemical, biochemical, and thermochemical methods have been proposed to obtain biofuels from raw materials from biomass. In recent years, a thermochemical method that has generated great interest is hydrothermal liquefaction. In this paper, a brief review of the main sources for liquid biofuels and the synthesis processes is presented, with special emphasis on the production of biofuels using hydrothermal liquefaction by using waste generated by human activity as raw material. Full article

(This article belongs to the Special Issue Effect of Surface Properties and Mobility in Chemical Reactions and Catalysis)

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