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Catalysts
Special Issues
Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes
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Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes

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

Deadline for manuscript submissions: closed (31 January 2023) | Viewed by 25847

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Maja Milojević-Rakić

E-Mail Website1 Website2
Guest Editor
Faculty of Physical Chemistry, University of Belgrade, 11000 Belgrade, Serbia
Interests: zeolites and zeolite-based composites; synthesis and characterization of materials for application in environmental studies; chemical kinetics and catalysis; adsorption of pollutants
Dr. Danica Bajuk-Bogdanović

E-Mail Website
Guest Editor
Faculty of Physical Chemistry, University of Belgrade, 11000 Belgrade, Serbia
Interests: heteropoly compounds, Raman and FTIR spectroscopy; synthesis and characterization of materials for application in environmental studies

Special Issue Information

Dear Colleagues,

Zeolites and porous materials, in general, are some of the most promising host materials for association with various active constituents. Zeolites represent a family of highly ordered systems with pores, which, along with high specific surface and negatively charged framework, enable the introduction of different functionalizing phases. Excellent adsorption and catalytic properties are often ascribed, and further research is increasingly being transferred to the domain of biological applications. Zeolites are currently regarded as dietary super-materials and this, sometimes, is an overstatement. Every drugstore is selling zeolite-based nutritional formulations enhanced with vitamins, enzymes, etc., often without any scientific basis to support the claims of high nutritional benefits. Antioxidant, antimicrobial, detoxifying, and anticancer activity is often attributed to both synthetic and natural zeolites. However, a strict survey of the available literature provides somewhat controversial findings—do zeolites represent the best choice, or do a series of improvements/added functionalities need to be incorporated to obtain efficient samples? This is a challenging question, and improvements in the area are quite versatile. This issue intends to highlight the true and essential applications of zeolites and porous materials primarily in adsorption and catalysis, but also in other areas of research.

Submissions to this Special Issue on “Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes” are welcome in the form of original research papers or short reviews that reflect the state of research in this field on the following topics: all studies related to the application of zeolites in industrial catalysis, separation technology, environmental protection, electrochemistry, membranes, sensors, optical devices, etc.; synthesis and physicochemical characterization of porous and zeolite-based materials; functionalization/modifications of zeolites, composites comprising natural and synthetic zeolites and porous matrices; adsorption (and other separation techniques) using porous adsorbents; Catalysis by zeolite-based materials and host/guest interactions; and theoretical modelling of catalysis/adsorption by porous materials.

Dr. Maja Milojević-Rakić
Dr. Danica Bajuk-Bogdanović
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • all studies related to the application of porous materials in industrial catalysis, separation technology, environmental protection, electrochemistry, membranes, sensors, optical devices, etc.
  • the synthesis and physico-chemical characterization of zeolite-based materials
  • functionalization/modifications of zeolites, composites comprising natural and synthetic zeolites/porous matrices
  • adsorption (and other separation techniques) using porous adsorbents
  • catalysis by zeolite-based materials and host/guest interactions
  • theoretical modeling of adsorption/catalysis comprising porous materials

Published Papers (14 papers)

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Editorial

Jump to: Research, Review

4 pages, 191 KiB  
Editorial
Recent Advances in Zeolites and Porous Materials Applications in Catalysis and Adsorption Processes
by Maja Milojević-Rakić and Danica Bajuk-Bogdanović
Catalysts 2023, 13(5), 863; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13050863 - 09 May 2023
Cited by 3 | Viewed by 1487
Abstract
Zeolites and porous materials are some of the most promising materials for various applications [...] Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)

Research

Jump to: Editorial, Review

18 pages, 3129 KiB  
Article
Tuning the Structure and Acidity of Pt/Hierarchical SSZ-32 Catalysts to Boost the Selective Hydroisomerization of n-Hexadecane
by Xinyue Yang, Wenli Zhao, Linlin Liu, Xiaopo Niu and Qingfa Wang
Catalysts 2023, 13(4), 702; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13040702 - 05 Apr 2023
Cited by 2 | Viewed by 1136
Abstract
Developing highly selective and efficient bifunctional catalysts is an important issue for the hydroisomerization of long-chain n-alkanes. It is vital to tailor the balance of isomerization and cracking reactions in hydroisomerization. Herein, a bifunctional Pt/hierarchical SSZ-32 catalyst was fabricated with a sequential [...] Read more.
Developing highly selective and efficient bifunctional catalysts is an important issue for the hydroisomerization of long-chain n-alkanes. It is vital to tailor the balance of isomerization and cracking reactions in hydroisomerization. Herein, a bifunctional Pt/hierarchical SSZ-32 catalyst was fabricated with a sequential desilication–dealumination treatment to boost the selective hydroisomerization of n-hexadecane (C16). The pore structure and acid sites of SSZ-32 zeolite were tailored. More mesopore and Brønsted acid sites were generated, and the ratio of weak to strong Brønsted acidity (Bw/Bs) was increased by the sequential desilication–dealumination. The generated hierarchical structure had little effect on the selectivity of the reaction pathways of hydroisomerization versus cracking. The ratio of isomers/cracking products increased almost linearly with the increase in the Bw/Bs ratios. Meanwhile, the synergetic effect of the hierarchical structure and acidity regulation promoted the selectivity of monobranched i-C16 products. Therefore, the resulting Pt/SSZ-0.6AS exhibited the highest activity with a total isomer yield of 71.5% at 255 °C and the enhanced formation mechanism of monobranched isomers occurred via the pore mouth. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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22 pages, 6490 KiB  
Article
Effects of the Acidic and Textural Properties of Y-Type Zeolites on the Synthesis of Pyridine and 3-Picoline from Acrolein and Ammonia
by Israel Pala-Rosas, José Luis Contreras, José Salmones, Ricardo López-Medina, Deyanira Angeles-Beltrán, Beatriz Zeifert, Juan Navarrete-Bolaños and Naomi N. González-Hernández
Catalysts 2023, 13(4), 652; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13040652 - 26 Mar 2023
Cited by 3 | Viewed by 1488
Abstract
A set of Y-type zeolites with Si/Al atomic ratios between 7–45 were studied as catalysts in the aminocyclization reaction between acrolein and ammonia to produce pyridine and 3-picoline. The catalytic activity tests at 360 °C revealed that the acrolein conversion increased in the [...] Read more.
A set of Y-type zeolites with Si/Al atomic ratios between 7–45 were studied as catalysts in the aminocyclization reaction between acrolein and ammonia to produce pyridine and 3-picoline. The catalytic activity tests at 360 °C revealed that the acrolein conversion increased in the order Z45 < ZY34 < ZY7 < ZY17, in agreement with the increase of the total acidity per gram of catalyst. In all cases, pyridine bases and cracking products (acetaldehyde and formaldehyde) were detected in the outflow from the reactor. The total yield of pyridines was inversely proportional to the total acidity for the catalysts, which presented large surface areas and micro- and mesoporosity. The selectivity towards 3-picoline was favored when using catalysts with a Brønsted/Lewis acid sites ratio close to 1. The formation of pyridine occurred more selectively over Lewis acid sites than Brønsted acid sites. The deactivation tests showed that the time on stream of the catalysts depended on the textural properties of zeolites, i.e., large pore volume and large BET area, as evidenced by the deactivation rate constants and the characterization of the spent catalysts. The physicochemical properties of the catalysts were determined by XRD, UV-vis, and Raman spectroscopies, infrared spectroscopy with adsorbed pyridine, N2 physisorption, and SEM-EDXS. After the reaction, the spent catalysts were characterized by XRD, Raman spectroscopy, TGA, and SEM-EDXS, indicating that the uniform deposition of polyaromatic species on the catalyst surface and within the porous system resulted in the loss of activity. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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18 pages, 4587 KiB  
Article
Insights into Synergy of Copper and Acid Sites for Selective Catalytic Reduction of NO with Ammonia over Zeolite Catalysts
by Wenyi Zhao, Menglin Shen, Yueran Zhu, Xudong Ren and Xingang Li
Catalysts 2023, 13(2), 301; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13020301 - 28 Jan 2023
Cited by 2 | Viewed by 1280
Abstract
Herein, we report the function of copper sites in Cu-SSZ-13, Cu-ZSM-5 and Cu-Beta catalysts with the same Si/Al ratio (14) and Cu/Al ratio (0.4) on selective catalytic reduction of NO with NH3 (NH3-SCR) and reveal the relationship between active sites [...] Read more.
Herein, we report the function of copper sites in Cu-SSZ-13, Cu-ZSM-5 and Cu-Beta catalysts with the same Si/Al ratio (14) and Cu/Al ratio (0.4) on selective catalytic reduction of NO with NH3 (NH3-SCR) and reveal the relationship between active sites (Cu sites, acid sites) and catalytic activity. The results show that the amount of isolated Cu2+ ions in the catalysts directly determines the formation of strong Lewis acid sites and reaction intermediate NO3− ions, thus affecting the low-temperature SCR performance, while the amount of highly stable Cu+ ions and Brønsted acid sites is related to the high-temperature SCR performance of the catalysts. Consequently, it contains enough isolated Cu2+ ions, highly stable Cu+ ions and Brønsted acid sites, which endows Cu-SSZ-13 with excellent NH3-SCR activity. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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17 pages, 1770 KiB  
Article
Influence of the Type and the Amount of Surfactant in Phillipsite on Adsorption of Diclofenac Sodium
by Danijela Smiljanić, Aleksandra Daković, Milena Obradović, Milica Ožegović, Marija Marković, George E. Rottinghaus and Bruno de Gennaro
Catalysts 2023, 13(1), 71; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13010071 - 30 Dec 2022
Cited by 4 | Viewed by 1340
Abstract
Modified phillipsite samples were prepared with two different amounts (monolayer and bilayer coverage) of surfactants octadecyldimethylbenzylammonium chloride (O) and dodecylamine (D). Composites were characterized by Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR–ATR), thermal analysis and determination of zeta potential, and subsequently [...] Read more.
Modified phillipsite samples were prepared with two different amounts (monolayer and bilayer coverage) of surfactants octadecyldimethylbenzylammonium chloride (O) and dodecylamine (D). Composites were characterized by Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR–ATR), thermal analysis and determination of zeta potential, and subsequently tested for removal of diclofenac sodium (DCF). Drug adsorption experiments were performed under different initial DCF concentrations and different contact times. In order to investigate the influence of the chemical structure of surfactants used for modification of phillipsite on the preparation and properties of composites and DCF adsorption, experimental data were compared with previously published results on DCF adsorption by composites containing phillipsite and the same amounts of surfactants cetylpyridinium chloride (C) and Arquad®2HT-75 (A). DCF adsorption isotherms for O and D composites showed a better fit with the Langmuir model with maximum adsorption capacities between 12.3 and 38.4 mg/g and are similar to those for C and A composites, while kinetics run followed a pseudo-second-order model. Composites containing either benzyl or pyridine functional groups showed higher adsorption of DCF, implying that surfactant structure has a significant impact on drug adsorption. Drug adsorption onto O, D, C and A composites was also confirmed by FTIR–ATR spectroscopy and zeta potential measurements. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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15 pages, 4381 KiB  
Article
Thermogravimetry Applied for Investigation of Coke Formation in Ethanol Conversion over Heteropoly Tungstate Catalysts
by Orsina Verdeş, Alexandru Popa, Silvana Borcănescu, Mariana Suba and Viorel Sasca
Catalysts 2022, 12(9), 1059; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12091059 - 16 Sep 2022
Cited by 3 | Viewed by 1949
Abstract
Thermogravimetric analysis (TGA) was used to evaluate the thermal stability and the amount of coke deposition resulting from the deactivation of catalysts during ethanol dehydration reaction in a fixed bed continuous flow reactor. In this study, a series of catalysts containing 30% of [...] Read more.
Thermogravimetric analysis (TGA) was used to evaluate the thermal stability and the amount of coke deposition resulting from the deactivation of catalysts during ethanol dehydration reaction in a fixed bed continuous flow reactor. In this study, a series of catalysts containing 30% of Pd doped and pure 12-tungstophosphoric acid and its insoluble Cs2.5H0.5PW12O40 salt supported on SBA-15 were prepared. The catalytic efficiency of ethanol dehydration reaction was also evaluated. Two types of coke are identified from the TPO (Temperature programmed oxidation) profiles and assigned to the coke precursor and hard coke, respectively. The results indicate that cesium salts reduced the formation of hard coke. The amount of total coke formed was significantly reduced by supporting the catalysts on mesoporous SBA-15 molecular sieves. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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11 pages, 4519 KiB  
Article
Xylene and n-Hexane Adsorption Performance of a Waste Methanol-to-Propylene Catalyst under Acid-Base Treatment
by Xiaojing Yong, Hui Su, Nana Zhao, Zhengwei Jin, Min Yao and Yulong Ma
Catalysts 2022, 12(9), 1028; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12091028 - 10 Sep 2022
Cited by 1 | Viewed by 1171
Abstract
Spent methanol-to-propylene (MTP) catalysts have a large specific surface area and high porosity but are usually directly disposed of in landfills, and recycling is rare. In this study, spent MTP catalyst was moderately dealuminized with acids and etched with an alkali solvent to [...] Read more.
Spent methanol-to-propylene (MTP) catalysts have a large specific surface area and high porosity but are usually directly disposed of in landfills, and recycling is rare. In this study, spent MTP catalyst was moderately dealuminized with acids and etched with an alkali solvent to increase its specific surface area. A novel adsorbent was obtained. XRD, SEM, FT-IR, XRD, XRF, and MAS-NMR characterization shows that the adsorbent maintains a typical ZSM-5 zeolite structure, and the dealumination effect of H2C2O4 is better than that of HCl. HCl mainly removes the framework aluminum of the molecular sieve; H2C2O4 not only removes the framework aluminum but also dissolves some of the nonframework aluminum, which increases the BET-specific surface area and pore diameter. The spent catalyst maintains an irregular ellipsoidal shape. After alkali treatment, the surface of the spherical particles becomes rough. With increasing alkali concentration, the damage degree increases. After treatment with 4 mol/L H2C2O4 and 0.1 mol/L NaOH, the p-xylene and n-hexane adsorption capacities reach the maximum, with values of 141.04 mg/g and 106.87 mg/g, respectively, 20.7% and 16.2% greater than those before treatment. These findings indicate that modified spent MTP catalyst has the potential for application in the removal of VOCs from the air. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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12 pages, 5490 KiB  
Article
Interventions to the Spontaneous Fabrication of Hierarchical ZSM-5 Zeolites by Fluorination-Alkaline Treatment
by Zifeng Guo, Meihua Hong, Yonghua Yu, Guanfeng Liu, Jiazong Zang, Dazhi Zhang, Huimin Gong, Keyu Yang and Shengjun Huang
Catalysts 2022, 12(9), 954; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12090954 - 28 Aug 2022
Cited by 1 | Viewed by 1083
Abstract
The sequential fluorination-alkaline treatment protocol has been applied for the tailoring of siliceous ZSM-5 zeolite. The original spontaneous growth of mesoporosity in alkaline medium is altered due to the antecedent fluorination step. The outcome is demonstrated by the apparent delay in the mesoporosity [...] Read more.
The sequential fluorination-alkaline treatment protocol has been applied for the tailoring of siliceous ZSM-5 zeolite. The original spontaneous growth of mesoporosity in alkaline medium is altered due to the antecedent fluorination step. The outcome is demonstrated by the apparent delay in the mesoporosity growth, whose essential duration for the well-defined mesoporosity is therefore extended from 30 min to 60 min. A low fluorination level decelerates the mesoporosity growth, whereas a high fluorination level enables the achievement of the mesoporosity. These impacts are closely linked with the alteration to the states of Al sites as the function of fluorination level. Compared to the states of Al sites in the pristine and steamed zeolites, the electronic and steric consequences on the environment of Al species by fluorination is proposed for the interplay with the alkaline medium for the mesoporosity growth. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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14 pages, 4316 KiB  
Article
The Effect of Y Zeolites with Different Pores on Tetralin Hydrocracking for the Production of High-Value Benzene, Toluene, Ethylbenzene and Xylene Products
by Ce Xian, Yichao Mao, Xiangyun Long, Ziming Wu, Xiang Li and Zhengkai Cao
Catalysts 2022, 12(8), 848; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12080848 - 02 Aug 2022
Cited by 3 | Viewed by 1449
Abstract
A series of Y zeolites with different pore properties was prepared as a support for hydrocracking catalysts for the production of BTEX (benzene, toluene, ethyl-benzene, and xylene) from tetralin. Some important characterizations, including N2 adsorption–desorption, NH3-TPD, Py-IR, and HRTEM, were [...] Read more.
A series of Y zeolites with different pore properties was prepared as a support for hydrocracking catalysts for the production of BTEX (benzene, toluene, ethyl-benzene, and xylene) from tetralin. Some important characterizations, including N2 adsorption–desorption, NH3-TPD, Py-IR, and HRTEM, were applied to obtain the properties of different catalysts. Meanwhile, the tetralin hydrocracking performances of those catalysts were investigated on a high-pressure fixed-bed microreactor. The results showed that Si/Al ratio is the core property of zeolites and that the increase in the Vmicro/Vmeso of zeolites could facilitate the formation of BTEX products by hydrocracking tetralin. The method of hydrocracking tetralin was proposed. It was also found that the hydrogenation–cracking path was controlled by aromatic saturation thermodynamics, and strong acidity aided the backward shift of equilibrium temperature. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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13 pages, 2507 KiB  
Article
How to Obtain Maximum Environmental Applicability from Natural Silicates
by Daliborka Popadić, Nemanja Gavrilov, Ljubiša Ignjatović, Danina Krajišnik, Slavko Mentus, Maja Milojević-Rakić and Danica Bajuk-Bogdanović
Catalysts 2022, 12(5), 519; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12050519 - 05 May 2022
Cited by 8 | Viewed by 1895
Abstract
Unmodified natural silicates (bentonite, kaolin, clinoptilolite and diatomites) were tested as adsorbents for the organic pollutants in water tables using Methylene Blue (MB) as the model adsorbate. Among the selected materials, bentonite adsorbed as much as 237 mg/g, confirming its excellent suitability for [...] Read more.
Unmodified natural silicates (bentonite, kaolin, clinoptilolite and diatomites) were tested as adsorbents for the organic pollutants in water tables using Methylene Blue (MB) as the model adsorbate. Among the selected materials, bentonite adsorbed as much as 237 mg/g, confirming its excellent suitability for pollutant removal. Spectral evidence confirmed successful MB immobilization at the bentonite surface. Furthermore, the thermal treatment of MB-saturated adsorbent in an inert atmosphere at 700 °C produced a carbon/silicate composite. EDX confirmed the formation of the nitrogen-doped carbon overlay on the silica scaffold and the obtained composite material was probed as an electrode material for oxygen reduction in an alkaline solution. Reduction proceeded via a two-electron mechanism with the main product being HO2−, a known nucleophile, which was subsequently used to degrade/demethylate MB. The composite showed a considerable 70% MB removal rate after an hour of electrochemical treatment. The synergy between the processes of adsorption of MB and the surface-generated HO2− dictates the efficiency of the method and points to a possible route for spent adsorbent reuse in the form of a durable product for environmental protection. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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8 pages, 1837 KiB  
Article
Three-Dimensional Graphene with Preserved Channeling as a Binder Additive for Zeolite 13X for Enhanced Thermal Conductivity, Vapor Transport, and Vapor Adsorption Loading Kinetics
by Evan Gildernew, Syed Tareq and Sungwoo Yang
Catalysts 2022, 12(3), 292; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12030292 - 04 Mar 2022
Cited by 5 | Viewed by 1830
Abstract
Atmospheric water vapor extraction through adsorption to highly porous materials holds promise for its incorporation into broader technologies, including potable water generation. These technologies require breakthroughs in synthesis and design. Here, we demonstrate a composite of zeolite 13X sorbent for high adsorption capacity [...] Read more.
Atmospheric water vapor extraction through adsorption to highly porous materials holds promise for its incorporation into broader technologies, including potable water generation. These technologies require breakthroughs in synthesis and design. Here, we demonstrate a composite of zeolite 13X sorbent for high adsorption capacity infiltrated with a light-weight three-dimensional graphene binder, which effectively networks a substrate structure into the sorbent. The composites described maintained fidelity when passing through the pore structure. This was accomplished by the utilization of a sacrificial polymer for safeguarding channel networking during sorbent infiltration of the binder for the extension of substrate networking. The performance measures for adsorbate loadings and thermal flux are evaluated with additional measurements taken for considering compactions of sorbent/substrates. Graphene/Zeolite 13X with preserved channeling demonstrated specific heat flux at 7664 W/kg, while samples without preserved channeling measured 4206 W/kg. A 0.6 g/cm3 compaction resulted in a 412% and a 368% improvement in mass transport while compaction at 1.2 g/cm3 resulted in a 333% and a 290% improvement in mass transport. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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Review

Jump to: Editorial, Research

16 pages, 3178 KiB  
Review
A Comparative Review of Binder-Containing Extrusion and Alternative Shaping Techniques for Structuring of Zeolites into Different Geometrical Bodies
by Zahra Asgar Pour, Marwan M. Abduljawad, Yasser A. Alassmy, Ludwig Cardon, Paul H. M. Van Steenberge and Khaled O. Sebakhy
Catalysts 2023, 13(4), 656; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13040656 - 27 Mar 2023
Cited by 7 | Viewed by 3301
Abstract
Zeolites are crystalline metallosilicates displaying unique physicochemical properties with widespread applications in catalysis, adsorption, and separation. They are generally obtained by a multi-step process that starts with primary mixture aging, followed by hydrothermal crystallization, washing, drying, and, finally, a calcination step. However, the [...] Read more.
Zeolites are crystalline metallosilicates displaying unique physicochemical properties with widespread applications in catalysis, adsorption, and separation. They are generally obtained by a multi-step process that starts with primary mixture aging, followed by hydrothermal crystallization, washing, drying, and, finally, a calcination step. However, the zeolites obtained are in the powder form and because of generating a pressure drop in industrial fixed bed reactors, not applicable for industrial purposes. To overcome such drawbacks, zeolites are shaped into appropriate geometries and desired size (a few centimeters) using extrusion, where zeolite powders are mixed with binders (e.g., mineral clays or inorganic oxides). The presence of binders provides good mechanical strength against crushing in shaped zeolites, but binders may have adverse impacts on zeolite catalytic and sorption properties, such as active site dilution and pore blockage. The latter is more pronounced when the binder has a smaller particle size, which makes the zeolite internal active sites mainly inaccessible. In addition to the shaping requirements, a hierarchical structure with different levels of porosity (micro-, meso-, and macropores) and an interconnected network are essential to decrease the diffusion limitation inside the zeolite micropores as well as to increase the mass transfer because of the presence of larger auxiliary pores. Thus, the generation of hierarchical structure and its preservation during the shaping step is of great importance. The aim of this review is to provide a comprehensive survey and detailed overview on the binder-containing extrusion technique compared to alternative shaping technologies with improved mass transfer properties. An emphasis is allocated to those techniques that have been less discussed in detail in the literature. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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23 pages, 4459 KiB  
Review
ORR Catalysts Derived from Biopolymers
by Jelena Rupar, Danijela Tekić, Aleksandra Janošević Ležaić and Kush K. Upadhyay
Catalysts 2023, 13(1), 80; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13010080 - 30 Dec 2022
Cited by 4 | Viewed by 1903
Abstract
Due to the limited reaction rate of the oxygen reduction reaction (ORR), it is considered as a limiting factor in the performance of fuel cells and metal-air batteries. Platinum is considered the benchmark catalyst for ORR; however, the scarcity of platinum, its high [...] Read more.
Due to the limited reaction rate of the oxygen reduction reaction (ORR), it is considered as a limiting factor in the performance of fuel cells and metal-air batteries. Platinum is considered the benchmark catalyst for ORR; however, the scarcity of platinum, its high price, the drift phenomenon, its insufficient durability, and its susceptibility to gas poisoning are the reasons for the constant search for new ORR catalysts. Carbon-based catalysts show exceptional promise in this respect considering economic profitability and activity, and, in addition, they have favorable conductivity and often a large specific surface area. The use of chitin, cellulose, lignin, coconut shell particles, shrimp shells, and even hair for this purpose was reported, as they had similar electrochemical activity regarding Pt. Alginate, a natural polymer and a constituent of brown algae, can be successfully used to obtain carbon materials that catalyze ORR. In addition, metal atomic-level catalysts and metal N-doped porous carbon materials, obtained from sodium alginate as a precursor, have been proposed as efficient electrocatalysts for ORR. Except for alginate, other biopolymers have been reported to play an important role in the preparation of ORR catalysts. In this review, recent advances regarding biopolymer-derived ORR catalysts are summarized, with a focus on alginate as a source. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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22 pages, 1721 KiB  
Review
Environmental and Pharmacokinetic Aspects of Zeolite/Pharmaceuticals Systems—Two Facets of Adsorption Ability
by Nataša R. Mijailović, Bojana Nedić Vasiljević, Maja Ranković, Vladimir Milanović and Snežana Uskoković-Marković
Catalysts 2022, 12(8), 837; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12080837 - 30 Jul 2022
Cited by 12 | Viewed by 3036
Abstract
Zeolites belong to aluminosilicate microporous solids, with strong and diverse catalytic activity, which makes them applicable in almost every kind of industrial process, particularly thanks to their eco-friendly profile. Another crucial characteristic of zeolites is their tremendous adsorption capability. Therefore, it is self-evident [...] Read more.
Zeolites belong to aluminosilicate microporous solids, with strong and diverse catalytic activity, which makes them applicable in almost every kind of industrial process, particularly thanks to their eco-friendly profile. Another crucial characteristic of zeolites is their tremendous adsorption capability. Therefore, it is self-evident that the widespread use of zeolites is in environmental protection, based primarily on the adsorption capacity of substances potentially harmful to the environment, such as pharmaceuticals, pesticides, or other industry pollutants. On the other hand, zeolites are also recognized as drug delivery systems (DDS) carriers for numerous pharmacologically active agents. The enhanced bioactive ability of DDS zeolite as a drug carrying nanoplatform is confirmed, making this system more specific and efficient, compared to the drug itself. These two applications of zeolite, in fact, illustrate the importance of (ir)reversibility of the adsorption process. This review gives deep insight into the balance and dynamics that are established during that process, i.e., the interaction between zeolites and pharmaceuticals, helping scientists to expand their knowledge necessarily for a more effective application of the adsorption phenomenon of zeolites. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)
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