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Composite Porous Materials in Catalysis

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (1 June 2022) | Viewed by 26681

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Prof. Dr. Margarita D. Popova

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Bulgarian Academy of Sciences, Institute of Organic Chemistry with Centre for Phytochemistry, Sofia, Bulgaria
Interests: synthesis and modification of mesoporous silicas; nanosized metal oxides; approaches for functionalization of mesoporous composites; valorization of biomass; VOC oxidation; CO2 capture; drug delivery systems
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Prof. Dr. Hristiyan A. Aleksandrov

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Faculty of Chemistry and Pharmacy, University of Sofia, 1126 Sofia, Bulgaria
Interests: transition metal surfaces; nanoparticles and small clusters; complexes of transition metal ions; drug delivery systems; quantum chemical modelling of materials and catalysts
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Special Issue Information

Dear Colleagues,

Over the last few decades, porous materials have attracted research interest due to their unique properties and wide range of applications, from catalytic and adsorption processes to the development of new drug delivery systems. Hierarchical zeolites, modified mesoporous silicas, and nanosized metal oxides are successfully applied in the processes for biomass valorization, processes for environmental protection such as VOC oxidation and water purification, and CO₂ capture and utilization. Moreover, new important chemicals, biofuels, and biopolymers could be synthesized in the presence of porous-based catalysts. The development of new porous materials requires the application of a complex of routine and advanced physicochemical methods for design purposes. Due to the notable progress in the accuracy and reliability the quantum-chemical methods can further support this process as well as help in clarifying the detailed structure of the zeolites and mechanisms of the catalytic reactions occurring on them. The application of these materials ensures the green and sustainable realization of many catalytic processes.

This Special Issue is intended to provide a forum for recent achievements in the synthesis and application of new porous materials. Experimental and theoretical studies on adsorption and catalytic processes in the presence of porous materials are welcome. Systematic studies on physicochemical properties as well as the large-scale application of new porous materials will also be considered. New catalytic routes in biomass and CO₂ valorization are of interest to show the scalability of porous materials for industrial applications. Design of processes and analysis of operation conditions on processes for air and water purification are also welcome.

We hope that this Special Issue will demonstrate the capacity of porous materials and new directions in their application benefits.

Prof. Dr. Margarita D. Popova
Prof. Dr. Hristiyan A. Aleksandrov
Guest Editors

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Keywords

Modified mesoporous silicas
Hierarchical zeolites
Nanosized metal oxides
Biomass valorization
CO₂ capture and utilization
Environmental processes (VOC oxidation and water purification)
Modeling of zeolites

Published Papers (10 papers)

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Research

15 pages, 2791 KiB

Open AccessArticle

Hydrodeoxygenation of Levulinic Acid to γ-Valerolactone over Mesoporous Silica-Supported Cu-Ni Composite Catalysts

by Margarita Popova, Ivalina Trendafilova, Manuela Oykova, Yavor Mitrev, Pavleta Shestakova, Magdolna R. Mihályi and Ágnes Szegedi

Molecules 2022, 27(17), 5383; https://doi.org/10.3390/molecules27175383 - 24 Aug 2022

Cited by 3 | Viewed by 1465

Abstract

Monometallic (Cu, Ni) and bimetallic (Cu-Ni) catalysts supported on KIT-6 based mesoporous silica/zeolite composites were prepared using the wet impregnation method. The catalysts were characterized using X-ray powder diffraction, N₂ physisorption, SEM, solid state NMR and H₂-TPR methods. Finely dispersed NiO and CuO were detected after the decomposition of impregnating salt on the silica carrier. The formation of small fractions of ionic Ni²⁺ and/or Cu²⁺ species, interacting strongly with the silica supports, was found. The catalysts were studied in the gas-phase upgrading of lignocellulosic biomass-derived levulinic acid (LA) to γ-valerolactone (GVL). The bimetallic, CuNi-KIT-6 catalyst showed 100% LA conversion at 250 °C and atmospheric pressure. The high LA conversion and GVL yield can be attributed to the high specific surface area and finely dispersed Cu-Ni species in the catalyst. Furthermore, the catalyst also exhibited high stability after 24 h of reaction time with a GVL yield above 80% without any significant change in metal dispersion. Full article

(This article belongs to the Special Issue Composite Porous Materials in Catalysis)

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15 pages, 4025 KiB

Open AccessArticle

Thermal Catalytic-Cracking Low-Density Polyethylene Waste by Metakaolin-Based Geopolymer NaA Microsphere

by Shanshan Tang, Yan He, Xingfa Deng and Xuemin Cui

Molecules 2022, 27(8), 2557; https://doi.org/10.3390/molecules27082557 - 15 Apr 2022

Cited by 4 | Viewed by 2001

Abstract

Metakaolin-based geopolymer microspheres (MGM) with hierarchical pore structures were prepared by suspension dispersion method in dimethicone at 80 °C. The hydrothermal modification of MGM was carried out at a lower temperature of 80 °C, and a NaA molecular sieve converted from metakaolin-based geopolymer (NMGM) with good crystal structure was prepared and applied in thermal catalytic cracking of low-density polyethylene (LDPE) reaction. The one-pot two-stage thermal catalytic cracking of LDPE was carried out in a 100 mL micro-autoclave under normal pressure. In this work, the optimal proportions and optimal reaction conditions of catalysts for NMGM thermal catalytic cracking of LDPE waste to fuel oil were investigated. The NMGM catalyst showed high selectivity to the liquid product of thermal catalytic cracking of waste LDPE. Under the reaction conditions of reaction time of 1 h and reaction temperature of 400 °C, the liquid-phase yield of thermal catalytic cracking of LDPE reached a high of 88.45%, of which the content of gasoline components was 10.14% and the content of diesel components was 80.97%. Full article

(This article belongs to the Special Issue Composite Porous Materials in Catalysis)

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12 pages, 2397 KiB

Open AccessArticle

On the Nature of Extra-Framework Aluminum Species and Improved Catalytic Properties in Steamed Zeolites

by Konstantin Khivantsev, Nicholas R. Jaegers, Libor Kovarik, Miroslaw A. Derewinski, Ja-Hun Kwak and Janos Szanyi

Molecules 2022, 27(7), 2352; https://doi.org/10.3390/molecules27072352 - 06 Apr 2022

Cited by 12 | Viewed by 3913

Abstract

Steamed zeolites exhibit improved catalytic properties for hydrocarbon activation (alkane cracking and dehydrogenation). The nature of this practically important phenomenon has remained a mystery for the last six decades and was suggested to be related to the increased strength of zeolitic Bronsted acid sites after dealumination. We now utilize state-of-the-art infrared spectroscopy measurements and prove that during steaming, aluminum oxide clusters evolve (due to hydrolysis of Al out of framework positions with the following clustering) in the zeolitic micropores with properties very similar to (nano) facets of hydroxylated transition alumina surfaces. The Bronsted acidity of the zeolite does not increase and the total number of Bronsted acid sites decreases during steaming. O₅Al(VI)-OH surface sites of alumina clusters dehydroxylate at elevated temperatures to form penta-coordinate Al₁O₅ sites that are capable of initiating alkane cracking by breaking the first C-H bond very effectively with much lower barriers (at lower temperatures) than for protolytic C-H bond activation, with the following reaction steps catalyzed by nearby zeolitic Bronsted acid sites. This explains the underlying mechanism behind the improved alkane cracking and alkane dehydrogenation activity of steamed zeolites: heterolytic C-H bond breaking occurs on Al-O sites of aluminum oxide clusters confined in zeolitic pores. Our findings explain the origin of enhanced activity of steamed zeolites at the molecular level and provide the missing understanding of the nature of extra-framework Al species formed in steamed/dealuminated zeolites. Full article

(This article belongs to the Special Issue Composite Porous Materials in Catalysis)

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21 pages, 2537 KiB

Open AccessArticle

Purification of Hydrogen from CO with Cu/ZSM-5 Adsorbents

by Mihail Mihaylov, Elena Ivanova, Videlina Zdravkova, Stanislava Andonova, Nikola Drenchev, Kristina Chakarova, Radoslav Kefirov, Rositsa Kukeva, Radostina Stoyanova and Konstantin Hadjiivanov

Molecules 2022, 27(1), 96; https://doi.org/10.3390/molecules27010096 - 24 Dec 2021

Cited by 2 | Viewed by 3075

Abstract

The transition to a hydrogen economy requires the development of cost-effective methods for purifying hydrogen from CO. In this study, we explore the possibilities of Cu/ZSM-5 as an adsorbent for this purpose. Samples obtained by cation exchange from aqueous solution (AE) and solid-state exchange with CuCl (SE) were characterized by in situ EPR and FTIR, H₂-TPR, CO-TPD, etc. The AE samples possess mainly isolated Cu²⁺ cations not adsorbing CO. Reduction generates Cu⁺ sites demonstrating different affinity to CO, with the strongest centres desorbing CO at about 350 °C. The SE samples have about twice higher Cu/Al ratios, as one H⁺ is exchanged with one Cu⁺ cation. Although some of the introduced Cu⁺ sites are oxidized to Cu²⁺ upon contact with air, they easily recover their original oxidation state after thermal treatment in vacuum or under inert gas stream. In addition, these Cu⁺ centres regenerate at relatively low temperatures. It is important that water does not block the CO adsorption sites because of the formation of Cu⁺(CO)(H₂O)_x complexes. Dynamic adsorption studies show that Cu/ZSM-5 selectively adsorbs CO in the presence of hydrogen. The results indicate that the SE samples are very perspective materials for purification of H₂ from CO. Full article

(This article belongs to the Special Issue Composite Porous Materials in Catalysis)

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17 pages, 4165 KiB

Open AccessArticle

Hydrodemethoxylation/Dealkylation on Bifunctional Nanosized Zeolite Beta

by Margarita Popova, Ágnes Szegedi, Manuela Oykova, Hristina Lazarova, Neli Koseva, Magdolna R. Mihályi, Daniela Karashanova, Yavor Mitrev and Pavletta Shestakova

Molecules 2021, 26(24), 7694; https://doi.org/10.3390/molecules26247694 - 20 Dec 2021

Cited by 3 | Viewed by 2639

Abstract

Mono-, and bimetallic Ni-, Ru-, and Pt-modified nanosized Beta zeolite catalysts were prepared by the post synthesis method and characterized by powder X-ray diffraction (XRD), nitrogen physisorption, HRTEM microscopy, temperature-programmed reduction (TPR-TGA), ATR FT-IR spectroscopy, and by solid-state MAS-NMR spectroscopy. The presence of nanosized nickel-oxide, ruthenium-oxide, and platinum species was detected on the catalysts. The presence of Brønsted and Lewis acid sites, and incorporation of nickel ions into zeolite lattice was proven by FT-IR of adsorbed pyridine. The structural changes in the catalyst matrix were investigated by solid state NMR spectroscopy. The catalysts were used in a gas-phase hydrodemethoxylation and dealkylation of 2-methoxy-4-propylphenol as a lignin derivative molecule for phenol synthesis. Full article

(This article belongs to the Special Issue Composite Porous Materials in Catalysis)

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13 pages, 3282 KiB

Open AccessArticle

Defect Formation, T-Atom Substitution and Adsorption of Guest Molecules in MSE-Type Zeolite Framework—DFT Modeling

by Petko St. Petkov, Kristina Simeonova, Iskra Z. Koleva, Hristiyan A. Aleksandrov, Yoshihiro Kubota, Satoshi Inagaki, Valentin Valtchev and Georgi N. Vayssilov

Molecules 2021, 26(23), 7296; https://doi.org/10.3390/molecules26237296 - 01 Dec 2021

Cited by 3 | Viewed by 1943

Abstract

We used computational modeling, based on Density Functional Theory, to help understand the preference for the formation of silanol nests and the substitution of Si by Ti or Al in different crystallographic positions of the MSE-type framework. All these processes were found to be energetically favorable by more than 100 kJ/mol. We suggested an approach for experimental identification of the T atom position in Ti-MCM-68 zeolite via simulation of infrared spectra of pyridine and acetonitrile adsorption at Ti. The modeling of adsorption of hydrogen peroxide at Ti center in the framework has shown that the molecular adsorption was preferred over the dissociative adsorption by 20 to 40 kJ/mol in the presence or absence of neighboring T-atom vacancy, respectively. Full article

(This article belongs to the Special Issue Composite Porous Materials in Catalysis)

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10 pages, 2332 KiB

Open AccessArticle

Fast and Selective Aqueous-Phase Oxidation of Styrene to Acetophenone Using a Mesoporous Janus-Type Palladium Catalyst

by Majid Vafaeezadeh, Ranja Saynisch, Andrea Lösch, Wolfgang Kleist and Werner R. Thiel

Molecules 2021, 26(21), 6450; https://doi.org/10.3390/molecules26216450 - 26 Oct 2021

Cited by 5 | Viewed by 2018

Abstract

A heterogeneous Janus-type palladium interphase catalyst was obtained by selective surface modification of a hollow mesoporous silica material. The catalyst comprises hydrophobic octyl groups on one side of the silica nanosheets and single-site bis-imidazoline dichlorido palladium(II) complexes on the other. The structure of this composite material has been analyzed by means of elemental analysis, atomic absorption spectroscopy, BET surface analysis, TGA, SEM and solid-state CP-MAS ¹³C and ²⁹Si NMR spectroscopy. The catalyst showed extraordinary activity for the aqueous-phase oxidation of styrene to acetophenone using 30% hydrogen peroxide as the oxidant. An 88% yield of acetophenone could be achieved after 60 min. Full article

(This article belongs to the Special Issue Composite Porous Materials in Catalysis)

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14 pages, 4390 KiB

Open AccessArticle

Catalytic Oxidation of CO and Benzene over Metal Nanoparticles Loaded on Hierarchical MFI Zeolite

by Totka Todorova, Petya Petrova and Yuri Kalvachev

Molecules 2021, 26(19), 5893; https://doi.org/10.3390/molecules26195893 - 28 Sep 2021

Cited by 2 | Viewed by 2071

Abstract

In order to obtain highly active catalytic materials for oxidation of carbon monoxide and volatile organic compounds (VOCs), monometallic platinum, copper, and palladium catalysts were prepared by using of two types of ZSM-5 zeolite as supports—parent ZSM-5 and the same one treated by HF and NH₄F buffer solution. The catalyst samples, obtained by loading of platinum, palladium, and copper on ZSM-5 zeolite treated using HF and NH₄F buffer solution, were more active in the reaction of CO and benzene oxidation compared with catalyst samples containing untreated zeolite. The presence of secondary mesoporosity played a positive role in increasing the catalytic activity due to improved reactant diffusion. The only exception was the copper catalysts in the reaction of CO oxidation, in which case the catalyst, based on untreated ZSM-5 zeolite, was more active. In this specific case, the key role is played by the oxidative state of copper species loaded on the ZSM-5 zeolites. Full article

(This article belongs to the Special Issue Composite Porous Materials in Catalysis)

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12 pages, 1981 KiB

Open AccessArticle

Adsorption of Toluene and Water over Cationic-Exchanged Y Zeolites: A DFT Exploration

by Etienne P. Hessou, Lucie A. Bédé, Hicham Jabraoui, Abderrahmane Semmeq, Michael Badawi and Valentin Valtchev

Molecules 2021, 26(18), 5486; https://doi.org/10.3390/molecules26185486 - 09 Sep 2021

Cited by 12 | Viewed by 3084

Abstract

In this study, density functional theory (DFT) calculations have been performed to investigate the adsorption mechanisms of toluene and water onto various cationic forms of Y zeolite (LiY, NaY, KY, CsY, CuY and AgY). Our computational investigation revealed that toluene is mainly adsorbed via π–interactions on alkalis exchanged Y zeolites, where the adsorbed toluene moiety interacts with a single cation for all cases with the exception of CsY, where two cations can simultaneously contribute to the adsorption of the toluene, hence leading to the highest interaction observed among the series. Furthermore, we find that the interaction energies of toluene increase while moving down in the alkaline series where interaction energies are 87.8, 105.5, 97.8, and 114.4 kJ/mol for LiY, NaY, KY and CsY, respectively. For zeolites based on transition metals (CuY and AgY), our calculations reveal a different adsorption mode where only one cation interacts with toluene through two carbon atoms of the aromatic ring with interaction energies of 147.0 and 131.5 kJ/mol for CuY and AgY, respectively. More importantly, we show that water presents no inhibitory effect on the adsorption of toluene, where interaction energies of this latter were 10 kJ/mol (LiY) to 47 kJ/mol (CsY) higher than those of water. Our results point out that LiY would be less efficient for the toluene/water separation while CuY, AgY and CsY would be the ideal candidates for this application. Full article

(This article belongs to the Special Issue Composite Porous Materials in Catalysis)

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16 pages, 3549 KiB

Open AccessArticle

Selective Production of Phenol on Bifunctional, Hierarchical ZSM-5 Zeolites

by Margarita Popova, Ágnes Szegedi, Manuela Oykova, Hristina Lazarova, Neli Koseva, Magdolna R. Mihályi and Pavletta Shestakova

Molecules 2021, 26(12), 3576; https://doi.org/10.3390/molecules26123576 - 11 Jun 2021

Cited by 5 | Viewed by 2332

Abstract

Mono- and bimetallic Ni-, Ru- and Pt-modified hierarchical ZSM-5 materials were prepared by impregnation technique and characterized by X-ray diffraction (XRD), N₂ physisorption, temperature-programmed reduction (TPR–TGA), ATR–FTIR and solid state NMR spectroscopy. Formation of finely dispersed nickel, ruthenium and platinum species was observed on the bimetallic catalysts. It was found that the peculiarity of the used zeolite structure and the modification procedure determine the type of formed metal oxides and their dispersion and reducibility. The samples’ acidity was studied via FTIR spectroscopy of adsorbed pyridine. The changes in the zeolite structure were studied via solid-state NMR spectroscopy. The catalysts were investigated in a gas-phase hydrodeoxygenation, transalkylation and dealkylation reaction of model lignin derivative molecules for phenol production. Full article

(This article belongs to the Special Issue Composite Porous Materials in Catalysis)

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