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Special Issue "Zeolite Chemistry"

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

Deadline for manuscript submissions: closed (31 January 2015)

Special Issue Editor

Guest Editor
Prof. Geoffrey L. Price (Website)

Wayne Banes Rumley Endowed Chair in Chemical Engineering Department of Chemical Engineering, University of Tulsa, 800 S. Tucker Drive, Tulsa, OK 74104, USA
Interests: zeolites; zeolite catalysis

Special Issue Information

Dear Colleagues,

Zeolites are a class of industrially important materials. They have found utility in separations, water softening, and catalysis in particular. The high level of research into the field of zeolite chemistry indicates further potential for applications of these materials in the industrial sector.

Research articles in all areas of zeolite chemistry including synthesis, ion-exchange, structure, characterization, modification, and catalysis from both experimental and computational perspectives are encouraged. Articles focusing on either microporous or mesoporous materials are welcome.

Prof. Geoffrey L. Price
Guest Editor

Submission

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. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as 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 refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules 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 1800 CHF (Swiss Francs).


Keywords

  • zeolites
  • zeolite catalysis
  • zeolite characterization
  • zeolite synthesis
  • microporous and mesoporous materials

Published Papers (6 papers)

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Research

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Open AccessArticle Synthesis of Novel Perfluoroalkylglucosides on Zeolite and Non-Zeolite Catalysts
Molecules 2015, 20(4), 6140-6152; doi:10.3390/molecules20046140
Received: 9 February 2015 / Revised: 27 March 2015 / Accepted: 31 March 2015 / Published: 8 April 2015
PDF Full-text (1635 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Perfluoroalkylglucosides comprise a very important class of fluorine-containing surfactants. These compounds can be synthesized by using the Fisher reaction, starting directly from glucose and the required perfluoroalcohols. We wish to report on the use of zeolite catalysts of different structure and composition [...] Read more.
Perfluoroalkylglucosides comprise a very important class of fluorine-containing surfactants. These compounds can be synthesized by using the Fisher reaction, starting directly from glucose and the required perfluoroalcohols. We wish to report on the use of zeolite catalysts of different structure and composition for the synthesis of perfluoroalkylglucosides when using glucose and 1-octafluoropentanol as substrates. Zeolites of different pore architecture have been chosen (ZSM-5, ZSM-12, MCM-22 and Beta). Zeolites were characterized by XRD, nitrogen sorption, scanning electron microscopy (SEM) and solid-state 27Al MAS NMR spectroscopy. The activity of the zeolite catalysts in the glycosidation reaction was studied in a batch reactor at 100 °C below atmospheric pressure. The performance of zeolites was compared to other catalysts, an ion-exchange resin (Purolite) and a montmorillonite-type layered aluminosilicate. The catalytic performance of zeolite Beta was the highest among the zeolites studied and the results were comparable to those obtained over Purolite and montmorillonite type catalysts. Full article
(This article belongs to the Special Issue Zeolite Chemistry)
Open AccessArticle Propane Dehydrogenation Catalyzed by ZSM-5 Zeolites. A Mechanistic Study Based on the Selective Energy Transfer (SET) Theory
Molecules 2015, 20(2), 2529-2535; doi:10.3390/molecules20022529
Received: 18 November 2014 / Revised: 4 January 2015 / Accepted: 27 January 2015 / Published: 2 February 2015
PDF Full-text (759 KB) | HTML Full-text | XML Full-text
Abstract
Experimentally determined activation energies of propane dehydrogenation catalyzed by ZSM-5 zeolites have been used to test the SET theory. The basis of this theory is that the catalyst system transfers vibrational energy via a resonance process to a specific vibration mode of [...] Read more.
Experimentally determined activation energies of propane dehydrogenation catalyzed by ZSM-5 zeolites have been used to test the SET theory. The basis of this theory is that the catalyst system transfers vibrational energy via a resonance process to a specific vibration mode of the reacting molecule. Being excited up to a certain number of vibrational quanta the molecule is brought to reaction. By analyzing the above-mentioned activation energies we found the wave number of this “specific mode” to be 1065 cm−1. This is very close to the rocking vibration of propane (1053 cm−1). We suggest that the propane molecule reacts when excited so that the CH3 group has been forced towards a flat structure with a carbon atom hybridization that is more sp2 than sp3. Consequently there is no way for three H-atoms to bind to the carbon and one of them must leave. This is the starting point of the reaction. The isokinetic temperature of the system was found as Tiso = 727 ± 4 K. From the SET formula for Tiso when both energy-donating (ω) and energy-accepting (ν) vibrations have the same frequency, viz., Tiso = Nhcν/2R, we obtain ν = ω = 1011 ± 6 cm−1. This agrees rather well with the CH3 rocking mode (1053 cm−1) and also with asymmetric “TO4” stretching vibrations of the zeolite structure (ω). Full article
(This article belongs to the Special Issue Zeolite Chemistry)
Open AccessArticle Vapour Phase Hydrogenation of Phenol over Rhodium on SBA-15 and SBA-16
Molecules 2014, 19(12), 20594-20612; doi:10.3390/molecules191220594
Received: 22 September 2014 / Revised: 17 November 2014 / Accepted: 24 November 2014 / Published: 10 December 2014
Cited by 1 | PDF Full-text (4048 KB) | HTML Full-text | XML Full-text
Abstract
In the present work, mesoporous SBA-15 and SBA-16 were synthesised using classical methods, and their physicochemical properties were investigated by X-ray diffraction (XRD), FTIR, TEM and N2 adsorption–desorption. Rhodium (Rh, 1 wt %) was loaded on the mesoporous SBA-15 and SBA-16 [...] Read more.
In the present work, mesoporous SBA-15 and SBA-16 were synthesised using classical methods, and their physicochemical properties were investigated by X-ray diffraction (XRD), FTIR, TEM and N2 adsorption–desorption. Rhodium (Rh, 1 wt %) was loaded on the mesoporous SBA-15 and SBA-16 by an impregnation method. The Rh surface coverage, dispersion and crystallite size were determined by room temperature H2 chemisorption on reduced samples. The catalytic activity of Rh supported on mesoporous SBA-15 and SBA-16 was evaluated for the first time in the hydrogenation of phenol in vapour phase in a temperature range between 130 and 270 °C at atmospheric pressure. The reaction over Rh/SBA-15 at 180 °C produced cyclohexanone as the major product (about 60%) along with lower amounts of cyclohexanol (about 35%) and cyclohexane (about 15%). The influences of temperature, H2/phenol ratio, contact time and the nature of the solvent on the catalytic performance were systematically investigated. The Rh/SBA-16 system offered lower phenol conversion compared to Rh/SBA-15, but both have a very high selectivity for cyclohexanone (above 60%). Full article
(This article belongs to the Special Issue Zeolite Chemistry)
Open AccessArticle Proton Adsorption Selectivity of Zeolites in Aqueous Media: Effect of Si/Al Ratio of Zeolites
Molecules 2014, 19(12), 20468-20481; doi:10.3390/molecules191220468
Received: 25 September 2014 / Revised: 1 December 2014 / Accepted: 3 December 2014 / Published: 8 December 2014
Cited by 5 | PDF Full-text (1243 KB) | HTML Full-text | XML Full-text
Abstract
In addition to their well-known uses as catalysts, zeolites are utilized to adsorb and remove various cations from aqueous system. The adsorption of the cations is ascribed to the negative charge of zeolites derived from isomorphous substitution of Si by Al. The [...] Read more.
In addition to their well-known uses as catalysts, zeolites are utilized to adsorb and remove various cations from aqueous system. The adsorption of the cations is ascribed to the negative charge of zeolites derived from isomorphous substitution of Si by Al. The amount of Na+ adsorption on 4A, X, Y, Na-P1 and mordenite type zeolites were determined in aqueous media, in a two-cation (Na+ and H+) system. Although each zeolite has a constant amount of negative charge, the amount of Na+ adsorption of each zeolite decreased drastically at low pH−pNa values, where pH−pNa is equal to log{(Na+)/(H+)}. By using the plot of the amount of Na+ adsorption versus pH−pNa, an index of the H+ selectivity, which is similar to the pKa of acids, of each zeolite was estimated, and the index tended to increase with decreasing Si/Al ratio of zeolites. These indicate that zeolites with lower Si/Al and higher negative charge density have higher H+ adsorption selectivity, and in fact, such a zeolite species (4A and X) adsorbed considerable amount of H+ even at weakly alkaline pH region. The adsorption of H+ results in the decrease of cation adsorption ability, and may lead to the dissolution of zeolites in aqueous media. Full article
(This article belongs to the Special Issue Zeolite Chemistry)
Figures

Open AccessArticle The Epoxidation of Limonene over the TS-1 and Ti-SBA-15 Catalysts
Molecules 2014, 19(12), 19907-19922; doi:10.3390/molecules191219907
Received: 23 October 2014 / Revised: 19 November 2014 / Accepted: 21 November 2014 / Published: 28 November 2014
Cited by 10 | PDF Full-text (265 KB) | HTML Full-text | XML Full-text
Abstract
Limonene belongs to a group of very important intermediates used in the production of fine chemicals. This monoterpene compound can be obtained from peels of oranges or lemon which are a (biomass) waste from the orange juice industry. Thus, limonene is a [...] Read more.
Limonene belongs to a group of very important intermediates used in the production of fine chemicals. This monoterpene compound can be obtained from peels of oranges or lemon which are a (biomass) waste from the orange juice industry. Thus, limonene is a renewable, easy available and a relatively cheap compound. This work presents preliminary studies on the process of limonene epoxidation over zeolite type catalysts such as: TS-1 and Ti-SBA-15. In these studies methanol was used as a solvent and as an oxidizing agent a 60 wt % hydrogen peroxide solution was applied. The activity of each catalyst was investigated for four chosen temperatures (0 °C, 40 °C, 80 °C and 120 °C). The reaction time was changed from 0.5 to 24 h. For each catalyst the most beneficial conditions (the appropriate temperature and the reaction time) have been established. The obtained results were compared and the most active catalyst was chosen. These studies have also shown different possible ways of limonene transformation, not only in the direction of 1,2-epoxylimonene and its corresponding diol, but also in direction of carveol, carvone and perillyl alcohol—compounds with a lot of applications. The possible mechanisms of formation of the allylic oxidation products were proposed. Full article
(This article belongs to the Special Issue Zeolite Chemistry)

Review

Jump to: Research

Open AccessReview Nanoporous Materials as New Engineered Catalysts for the Synthesis of Green Fuels
Molecules 2015, 20(4), 5638-5666; doi:10.3390/molecules20045638
Received: 4 February 2015 / Revised: 18 March 2015 / Accepted: 23 March 2015 / Published: 31 March 2015
Cited by 5 | PDF Full-text (828 KB) | HTML Full-text | XML Full-text
Abstract
This review summarizes the importance of nanoporous materials and their fascinating structural properties with respect to the catalytic and photocatalytic reduction of CO2 to methane, toward achieving a sustainable energy supply. The importance of catalysis as a bridge step for advanced [...] Read more.
This review summarizes the importance of nanoporous materials and their fascinating structural properties with respect to the catalytic and photocatalytic reduction of CO2 to methane, toward achieving a sustainable energy supply. The importance of catalysis as a bridge step for advanced energy systems and the associated environmental issues are stressed. A deep understanding of the fundamentals of these nanoporous solids is necessary to improve the design and efficiency of CO2 methanation. The role of the support dominates the design in terms of developing an efficient methanation catalyst, specifically with respect to ensuring enhanced metal dispersion and a long catalyst lifetime. Nanoporous materials provide the best supports for Ni, Ru, Rh, Co, Fe particles because they can prevent sintering and deactivation through coking, which otherwise blocks the metal surface as carbon accumulates. This review concludes with the major challenges facing the CO2 methanation by nanoporous materials for fuel applications. Full article
(This article belongs to the Special Issue Zeolite Chemistry)

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