Special Issue "Feature Papers to Celebrate the Landmarks of Catalysts"

A special issue of Catalysts (ISSN 2073-4344).

Deadline for manuscript submissions: closed (15 December 2014)

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

Special Issue Editor

Guest Editor
Prof. Dr. Keith Hohn

Department of Chemical Engineering, Kansas State University, Manhattan, KS 66506, USA
Website | E-Mail
Phone: 7855324315
Fax: +1 785 532 7372
Interests: catalysis and reaction engineering; natural gas conversion; oxidative dehydrogenation of light hydrocarbons; millisecond contact time reactors; nanoparticle catalysts

Special Issue Information

Dear Colleagues,

As scientists and engineers, we publish papers because we want others to read and learn from our work. We hope to make substantial contributions to the body of knowledge. For this reason, it is critical that the journals we publish in are widely read and cited.

Since its start on 9 May2011, the editorial board and guest editors have been working to make Catalysts an outstanding journal that receives the highest quality submissions. Our goal has been to have Catalysts included in the major citation indices in order to provide its authors with the visibility and impact that they desire. I am pleased to relate that we have met this goal, as Catalysts has been selected for inclusion in the Scopus and Science Citation Index Expanded (SCIE). In 2015, Catalysts will receive its first impact factor. These are major milestones for our growing journal, and are worthy of celebration.

In celebration of Catalysts improving recognition as an outstanding journal in the field of catalysis, we are launching a special issue. In this issue, pre-eminent catalytic scientists are invited to contribute an article. To honor their contribution, Catalysts will be waiving its publication fee for this Special Issue.

Thank you to all who have contributed in the past. We welcome your contributions to Catalysts in the years ahead.

Prof. Dr. Keith L. Hohn
Editor-In-Chief

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. Catalysts is an international peer-reviewed Open Access quarterly journal published by MDPI.

 

Published Papers (20 papers)

View options order results:
result details:
Displaying articles 1-20
Export citation of selected articles as:

Editorial

Jump to: Research, Review

Open AccessEditorial Feature Papers to Celebrate the Landmarks of Catalysts
Catalysts 2015, 5(4), 2018-2023; doi:10.3390/catal5042018
Received: 6 November 2015 / Accepted: 13 November 2015 / Published: 24 November 2015
PDF Full-text (136 KB) | HTML Full-text | XML Full-text
Abstract
Catalysis is a critical scientific field that underpins much of the world’s chemical industry. For example, it is often quoted that catalysis plays a role in 90% of all industrial chemical products. This importance has led to numerous academic journals and specialized conferences
[...] Read more.
Catalysis is a critical scientific field that underpins much of the world’s chemical industry. For example, it is often quoted that catalysis plays a role in 90% of all industrial chemical products. This importance has led to numerous academic journals and specialized conferences on the subject, as practitioners seek outlets to publish their cutting-edge research on catalysis. [...] Full article

Research

Jump to: Editorial, Review

Open AccessArticle Investigation of Room Temperature Synthesis of Titanium Dioxide Nanoclusters Dispersed on Cubic MCM-48 Mesoporous Materials
Catalysts 2015, 5(3), 1603-1621; doi:10.3390/catal5031603
Received: 2 August 2015 / Revised: 1 September 2015 / Accepted: 11 September 2015 / Published: 18 September 2015
Cited by 3 | PDF Full-text (389 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Titania containing cubic MCM-48 mesoporous materials were synthesized successfully at room temperature by a modified Stöber method. The integrity of the cubic mesoporous phase was retained even at relatively high loadings of titania. The TiO2-MCM-48 materials were extensively characterized by a
[...] Read more.
Titania containing cubic MCM-48 mesoporous materials were synthesized successfully at room temperature by a modified Stöber method. The integrity of the cubic mesoporous phase was retained even at relatively high loadings of titania. The TiO2-MCM-48 materials were extensively characterized by a variety of physico-chemical techniques. The physico-chemical characterization indicate that Ti4+ ions can be substituted in framework tetrahedral positions. The relative amount of Ti4+ ions in tetrahedral position was dependent on the order of addition of the precursor. Even at relatively high loadings of titania, no distinct bulk phase of titania could be observed indicating that the titania nanoclusters are well dispersed on the high surface area mesoporous material and probably exist as amorphous nanoclusters. The TiO2-MCM-48 materials were found to exhibit 100% selectivity in the cyclohexene oxidation at room temperature in the presence of tert-butylhydroperoxide (t-BHP) as the oxidant. The results suggest that room temperature synthesis is an attractive option for the preparation of TiO2-MCM-48 materials with interesting catalytic properties. Full article
Open AccessArticle Bismuth Molybdate Catalysts Prepared by Mild Hydrothermal Synthesis: Influence of pH on the Selective Oxidation of Propylene
Catalysts 2015, 5(3), 1554-1573; doi:10.3390/catal5031554
Received: 20 July 2015 / Accepted: 25 August 2015 / Published: 10 September 2015
Cited by 10 | PDF Full-text (962 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A series of bismuth molybdate catalysts with relatively high surface area was prepared via mild hydrothermal synthesis. Variation of the pH value and Bi/Mo ratio during the synthesis allowed tuning of the crystalline Bi-Mo oxide phases, as determined by X-ray diffraction (XRD) and
[...] Read more.
A series of bismuth molybdate catalysts with relatively high surface area was prepared via mild hydrothermal synthesis. Variation of the pH value and Bi/Mo ratio during the synthesis allowed tuning of the crystalline Bi-Mo oxide phases, as determined by X-ray diffraction (XRD) and Raman spectroscopy. The pH value during synthesis had a strong influence on the catalytic performance. Synthesis using a Bi/Mo ratio of 1/1 at pH ≥ 6 resulted in γ-Bi2MoO6, which exhibited a better catalytic performance than phase mixtures obtained at lower pH values. However, a significantly lower catalytic activity was observed at pH = 9 due to the low specific surface area. γ-Bi2MoO6 synthesized with Bi/Mo = 1/1 at pH = 6 and 7 exhibited relatively high surface areas and the best catalytic performance. All samples prepared with Bi/Mo = 1/1, except samples synthesized at pH = 1 and 9, showed better catalytic performance than samples synthesized with Bi/Mo = 2/3 at pH = 4 and 9 and γ-Bi2MoO6 synthesized by co-precipitation at pH = 7. At temperatures above 440 °C, the catalytic activity of the hydrothermally synthesized bismuth molybdates started to decrease due to sintering and loss of surface area. These results support that a combination of the required bismuth molybdate phase and a high specific surface area is crucial for a good performance in the selective oxidation of propylene. Full article
Figures

Open AccessArticle Iron Fischer-Tropsch Catalysts Prepared by Solvent-Deficient Precipitation (SDP): Effects of Washing, Promoter Addition Step, and Drying Temperature
Catalysts 2015, 5(3), 1352-1374; doi:10.3390/catal5031352
Received: 10 April 2015 / Revised: 5 July 2015 / Accepted: 15 July 2015 / Published: 24 July 2015
Cited by 4 | PDF Full-text (8864 KB) | HTML Full-text | XML Full-text
Abstract
A novel, solvent-deficient precipitation (SDP) method for catalyst preparation in general and for preparation of iron FT catalysts in particular is reported. Eight catalysts using a 23 factorial design of experiments to identify the key preparation variables were prepared. The catalysts were
[...] Read more.
A novel, solvent-deficient precipitation (SDP) method for catalyst preparation in general and for preparation of iron FT catalysts in particular is reported. Eight catalysts using a 23 factorial design of experiments to identify the key preparation variables were prepared. The catalysts were characterized by electron microprobe, N2 adsorption, TEM, XRD, and ICP. Results show that the morphology of the catalysts, i.e., surface area, pore volume, pore size distribution, crystallite sizes, and promoter distribution are significantly influenced by (1) whether or not the precursor catalyst is washed, (2) the promoter addition step, and (3) the drying condition (temperature). Consequently, the activity, selectivity, and stability of the catalysts determined from fixed-bed testing are also affected by these three variables. Unwashed catalysts prepared by a one-step method and dried at 100 °C produced the most active catalysts for FT synthesis. The catalysts of this study prepared by SDP compared favorably in activity, productivity, and stability with Fe FT catalysts reported in the literature. It is believed that this facile SDP approach has promise for development of future FT catalysts, and also offers a potential alternate route for the preparation of other catalysts for various other applications. Full article
Figures

Open AccessArticle Effect of Microgravity on Synthesis of Nano Ceria
Catalysts 2015, 5(3), 1306-1320; doi:10.3390/catal5031306
Received: 19 May 2015 / Revised: 8 July 2015 / Accepted: 14 July 2015 / Published: 20 July 2015
Cited by 2 | PDF Full-text (11061 KB) | HTML Full-text | XML Full-text
Abstract
Cerium oxide (CeO2) was prepared using a controlled-precipitation method under microgravity at the International Space Station (ISS). For comparison, ceria was also synthesized under normal-gravity conditions (referred as control). The Brunauer-Emmett-Teller (BET) surface area, pore volume and pore size analysis results
[...] Read more.
Cerium oxide (CeO2) was prepared using a controlled-precipitation method under microgravity at the International Space Station (ISS). For comparison, ceria was also synthesized under normal-gravity conditions (referred as control). The Brunauer-Emmett-Teller (BET) surface area, pore volume and pore size analysis results indicated that the ceria particles grown in space had lower surface area and pore volume compared to the control samples. Furthermore, the space samples had a broader pore size distribution ranging from 30–600 Å, whereas the control samples consisted of pore sizes from 30–50 Å range. Structural information of the ceria particles were obtained using TEM and XRD. Based on the TEM images, it was confirmed that the space samples were predominantly nano-rods, on the other hand, only nano-polyhedra particles were seen in the control ceria samples. The average particle size was larger for ceria samples synthesized in space. XRD results showed higher crystallinity as well as larger mean crystal size for the space samples. The effect of sodium hydroxide concentration on synthesis of ceria was also examined using 1 M and 3 M solutions. It was found that the control samples, prepared in 1 M and 3 M sodium hydroxide solutions, did not show a significant difference between the two. However, when the ceria samples were prepared in a more basic medium (3 M) under microgravity, a decrease in the particle size of the nano-rods and appearances of nano-polyhedra and spheres were observed. Full article
Figures

Open AccessArticle Surface Reaction Kinetics of Steam- and CO2-Reforming as Well as Oxidation of Methane over Nickel-Based Catalysts
Catalysts 2015, 5(2), 871-904; doi:10.3390/catal5020871
Received: 17 March 2015 / Accepted: 19 May 2015 / Published: 29 May 2015
Cited by 21 | PDF Full-text (11752 KB) | HTML Full-text | XML Full-text
Abstract
An experimental and kinetic modeling study on the Ni-catalyzed conversion of methane under oxidative and reforming conditions is presented. The numerical model is based on a surface reaction mechanism consisting of 52 elementary-step like reactions with 14 surface and six gas-phase species. Reactions
[...] Read more.
An experimental and kinetic modeling study on the Ni-catalyzed conversion of methane under oxidative and reforming conditions is presented. The numerical model is based on a surface reaction mechanism consisting of 52 elementary-step like reactions with 14 surface and six gas-phase species. Reactions for the conversion of methane with oxygen, steam, and CO2 as well as methanation, water-gas shift reaction and carbon formation via Boudouard reaction are included. The mechanism is implemented in a one-dimensional flow field description of a fixed bed reactor. The model is evaluated by comparison of numerical simulations with data derived from isothermal experiments in a flow reactor over a powdered nickel-based catalyst using varying inlet gas compositions and operating temperatures. Furthermore, the influence of hydrogen and water as co-feed on methane dry reforming with CO2 is also investigated. Full article
Figures

Open AccessArticle Real-Time Raman Monitoring during Photocatalytic Epoxidation of Cyclohexene over V-Ti/MCM-41 Catalysts
Catalysts 2015, 5(2), 518-533; doi:10.3390/catal5020518
Received: 28 November 2014 / Revised: 6 March 2015 / Accepted: 17 March 2015 / Published: 30 March 2015
Cited by 5 | PDF Full-text (2174 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A series of V- and/or Ti-loading MCM-41 catalysts are successfully synthesized with a hydrothermal method. The photocatalytic and thermal epoxidations of cyclohexene in the presence of tert-butyl hydroperoxide (t-BuOOH) were investigated with real-time monitored by NIR-Raman spectroscopy. It suggests that
[...] Read more.
A series of V- and/or Ti-loading MCM-41 catalysts are successfully synthesized with a hydrothermal method. The photocatalytic and thermal epoxidations of cyclohexene in the presence of tert-butyl hydroperoxide (t-BuOOH) were investigated with real-time monitored by NIR-Raman spectroscopy. It suggests that both V- and Ti-loading can be responsible for the cyclohexene epoxidation. Moreover, the complementary behavior of V- and Ti-loading may be related to a similar role of activation. Interestingly, the progress of the photo-epoxidation on V0.25Ti2/MCM-41 photocatalyst was monitored by changes in intensity of the characteristic Raman bands without interference from the UV-light irradiation. The result, for the first time, reveals that cyclohexene was directly photo-epoxidized to 1,2-epoxycyclohexane by t-BuOOH during the reaction. A possible mechanism of cyclohexene photo-epoxidation is also proposed for this study. Full article
Figures

Open AccessArticle Structural Evolution under Reaction Conditions of Supported (NH4)3HPMo11VO40 Catalysts for the Selective Oxidation of Isobutane
Catalysts 2015, 5(1), 460-477; doi:10.3390/catal5010460
Received: 24 November 2014 / Revised: 28 February 2015 / Accepted: 6 March 2015 / Published: 23 March 2015
Cited by 7 | PDF Full-text (1156 KB) | HTML Full-text | XML Full-text
Abstract
When using heteropolycompounds in the selective oxidation of isobutane to methacrolein and methacrylic acid, both the keeping of the primary structure (Keggin units) and the presence of acidic sites are necessary to obtain the desired products. The structural evolution of supported (NH4
[...] Read more.
When using heteropolycompounds in the selective oxidation of isobutane to methacrolein and methacrylic acid, both the keeping of the primary structure (Keggin units) and the presence of acidic sites are necessary to obtain the desired products. The structural evolution of supported (NH4)3HPMo11VO40 (APMV) catalysts under preliminary thermal oxidizing and reducing treatments was investigated. Various techniques, such as TGA/DTG (Thermo-Gravimetric Analysis/Derivative Thermo-Gravimetry), H2-TPR (Temperature Programed Reduction), in situ XRD (X-Ray Diffraction) and XPS (X-ray Photoelectron Spectroscopy), were applied. It was clearly evidenced that the thermal stability and the reducibility of the Keggin units are improved by supporting 40% APMV active phase on Cs3PMo12O40 (CPM). The partial degradation of APMV takes place depending on temperature and reaction conditions. The decomposition of ammonium cations (releasing NH3) leads to the formation of vacancies favoring cationic exchanges between vanadium coming from the active phase and cesium coming from the support. In addition, the vanadium expelled from the Keggin structure is further reduced to V4+, species, which contributes (with Mo5+) to activate isobutane. The increase in reducibility of the supported catalyst is assumed to improve the catalytic performance in comparison with those of unsupported APMV. Full article
Figures

Open AccessArticle Activated Carbon, Carbon Nanofiber and Carbon Nanotube Supported Molybdenum Carbide Catalysts for the Hydrodeoxygenation of Guaiacol
Catalysts 2015, 5(1), 424-441; doi:10.3390/catal5010424
Received: 15 December 2014 / Revised: 3 March 2015 / Accepted: 10 March 2015 / Published: 16 March 2015
Cited by 22 | PDF Full-text (4980 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Molybdenum carbide was supported on three types of carbon support—activated carbon; multi-walled carbon nanotubes; and carbon nanofibers—using ammonium molybdate and molybdic acid as Mo precursors. The use of activated carbon as support afforded an X-ray amorphous Mo phase, whereas crystalline molybdenum carbide phases
[...] Read more.
Molybdenum carbide was supported on three types of carbon support—activated carbon; multi-walled carbon nanotubes; and carbon nanofibers—using ammonium molybdate and molybdic acid as Mo precursors. The use of activated carbon as support afforded an X-ray amorphous Mo phase, whereas crystalline molybdenum carbide phases were obtained on carbon nanofibers and, in some cases, on carbon nanotubes. When the resulting catalysts were tested in the hydrodeoxygenation (HDO) of guaiacol in dodecane, catechol and phenol were obtained as the main products, although in some instances significant amounts of cyclohexane were produced. The observation of catechol in all reaction mixtures suggests that guaiacol was converted into phenol via sequential demethylation and HDO, although the simultaneous occurrence of a direct demethoxylation pathway cannot be discounted. Catalysts based on carbon nanofibers generally afforded the highest yields of phenol; notably, the only crystalline phase detected in these samples was Mo2C or Mo2C-ζ, suggesting that crystalline Mo2C is particularly selective to phenol. At 350 °C, carbon nanofiber supported Mo2C afforded near quantitative guaiacol conversion, the selectivity to phenol approaching 50%. When guaiacol HDO was performed in the presence of acetic acid and furfural, guaiacol conversion decreased, although the selectivity to both catechol and phenol was increased. Full article
Open AccessArticle Structural Evolution of Molybdenum Carbides in Hot Aqueous Environments and Impact on Low-Temperature Hydroprocessing of Acetic Acid
Catalysts 2015, 5(1), 406-423; doi:10.3390/catal5010406
Received: 8 January 2015 / Revised: 2 March 2015 / Accepted: 6 March 2015 / Published: 13 March 2015
Cited by 5 | PDF Full-text (1439 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We investigated the structural evolution of molybdenum carbides subjected to hot aqueous environments and their catalytic performance in low-temperature hydroprocessing of acetic acid. While bulk structures of Mo carbides were maintained after aging in hot liquid water, a portion of carbidic Mo sites
[...] Read more.
We investigated the structural evolution of molybdenum carbides subjected to hot aqueous environments and their catalytic performance in low-temperature hydroprocessing of acetic acid. While bulk structures of Mo carbides were maintained after aging in hot liquid water, a portion of carbidic Mo sites were converted to oxidic sites. Water aging also induced changes to the non-carbidic carbon deposited during carbide synthesis and increased surface roughness, which in turn affected carbide pore volume and surface area. The extent of these structural changes was sensitive to the initial carbide structure and was lower under actual hydroprocessing conditions indicating the possibility of further improving the hydrothermal stability of Mo carbides by optimizing catalyst structure and operating conditions. Mo carbides were active in acetic acid conversion in the presence of liquid water, their activity being comparable to that of Ru/C. The results suggest that effective and inexpensive bio-oil hydroprocessing catalysts could be designed based on Mo carbides, although a more detailed understanding of the structure-performance relationships is needed, especially in upgrading of more complex reaction mixtures or real bio-oils. Full article
Open AccessArticle Influence of the Synthesis Method for Pt Catalysts Supported on Highly Mesoporous Carbon Xerogel and Vulcan Carbon Black on the Electro-Oxidation of Methanol
Catalysts 2015, 5(1), 392-405; doi:10.3390/catal5010392
Received: 21 January 2015 / Revised: 26 February 2015 / Accepted: 28 February 2015 / Published: 13 March 2015
Cited by 8 | PDF Full-text (5229 KB) | HTML Full-text | XML Full-text
Abstract
Platinum catalysts supported on carbon xerogel and carbon black (Vulcan) were synthesized with the aim of investigating the influence of the characteristics of the support on the electrochemical performance of the catalysts. Three synthesis methods were compared: an impregnation method with two different
[...] Read more.
Platinum catalysts supported on carbon xerogel and carbon black (Vulcan) were synthesized with the aim of investigating the influence of the characteristics of the support on the electrochemical performance of the catalysts. Three synthesis methods were compared: an impregnation method with two different reducing agents, sodium borohydride and formic acid, and a microemulsion method, in order to study the effect of the synthesis method on the physico-chemical properties of the catalysts. X-ray diffraction and transmission electron microscopy were applied. Cyclic voltammetry and chronoamperometry were used for studying carbon monoxide and methanol oxidation. Catalysts supported on carbon xerogel presented higher catalytic activities towards CO and CH3OH oxidation than catalysts supported on Vulcan. The higher mesoporosity of carbon xerogel was responsible for the favored diffusion of reagents towards catalytic centers. Full article
Open AccessArticle A Mechanistic Study of Direct Activation of Allylic Alcohols in Palladium Catalyzed Amination Reactions
Catalysts 2015, 5(1), 349-365; doi:10.3390/catal5010349
Received: 11 December 2014 / Revised: 25 February 2015 / Accepted: 28 February 2015 / Published: 11 March 2015
Cited by 3 | PDF Full-text (6340 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We here report a computational approach on the mechanism of allylicamination reactions using allyl-alcohols and amines as the substrates and phosphoramidite palladium catalyst 1a, which operates in the presence of catalytic amount of 1,3-diethylurea as a co-catalyst. DFT calculations showed a cooperative
[...] Read more.
We here report a computational approach on the mechanism of allylicamination reactions using allyl-alcohols and amines as the substrates and phosphoramidite palladium catalyst 1a, which operates in the presence of catalytic amount of 1,3-diethylurea as a co-catalyst. DFT calculations showed a cooperative hydrogen-bonding array between the urea moiety and the hydroxyl group of the allyl alcohol, which strengthens the hydrogen bond between the O-H moiety of the coordinated allyl-alcohol and the carbonyl-moiety of the ligand. This hydrogen bond pattern facilitates the (rate-limiting) C-O oxidative addition step and leads to lower energy isomers throughout the catalytic cycle, clarifying the role of the urea-moiety. Full article
Open AccessArticle Ni-CeO2/C Catalysts with Enhanced OSC for the WGS Reaction
Catalysts 2015, 5(1), 298-309; doi:10.3390/catal5010298
Received: 11 December 2014 / Revised: 6 February 2015 / Accepted: 3 March 2015 / Published: 6 March 2015
Cited by 10 | PDF Full-text (613 KB) | HTML Full-text | XML Full-text
Abstract
In this work, the WGS performance of a conventional Ni/CeO2 bulk catalyst is compared to that of a carbon-supported Ni-CeO2 catalyst. The carbon-supported sample resulted to be much more active than the bulk one. The higher activity of the Ni-CeO2
[...] Read more.
In this work, the WGS performance of a conventional Ni/CeO2 bulk catalyst is compared to that of a carbon-supported Ni-CeO2 catalyst. The carbon-supported sample resulted to be much more active than the bulk one. The higher activity of the Ni-CeO2/C catalyst is associated to its oxygen storage capacity, a parameter that strongly influences the WGS behavior. The stability of the carbon-supported catalyst under realistic operation conditions is also a subject of this paper. In summary, our study represents an approach towards a new generation of Ni-ceria based catalyst for the pure hydrogen production via WGS. The dispersion of ceria nanoparticles on an activated carbon support drives to improved catalytic skills with a considerable reduction of the amount of ceria in the catalyst formulation. Full article
Open AccessArticle Selective Oxidation of Raw Glycerol Using Supported AuPd Nanoparticles
Catalysts 2015, 5(1), 131-144; doi:10.3390/catal5010131
Received: 22 December 2014 / Revised: 4 February 2015 / Accepted: 6 February 2015 / Published: 13 February 2015
Cited by 13 | PDF Full-text (1048 KB) | HTML Full-text | XML Full-text
Abstract
Bimetallic AuPd supported on different carbonaceous materials and TiO2 was tested in the liquid phase oxidation of commercial grade and raw glycerol. The latter was directly obtained from the base-catalyzed transesterification of edible rapeseed oil using KOH. The best catalytic results were
[...] Read more.
Bimetallic AuPd supported on different carbonaceous materials and TiO2 was tested in the liquid phase oxidation of commercial grade and raw glycerol. The latter was directly obtained from the base-catalyzed transesterification of edible rapeseed oil using KOH. The best catalytic results were obtained using activated carbon and nitrogen-functionalized carbon nanofibers as supports. In fact, the catalysts were more active using pure glycerol instead of the one obtained from rapeseed, where strong deactivation phenomena were present. Fourier transform infrared (FT-IR) and TEM were utilized to investigate the possible reasons for the observed loss of activity. Full article
Open AccessArticle Supported Photocatalyst for Removal of Emerging Contaminants from Wastewater in a Continuous Packed-Bed Photoreactor Configuration
Catalysts 2015, 5(1), 77-87; doi:10.3390/catal5010077
Received: 4 November 2014 / Revised: 6 January 2015 / Accepted: 15 January 2015 / Published: 2 February 2015
Cited by 12 | PDF Full-text (6499 KB) | HTML Full-text | XML Full-text
Abstract
Water pollution from emerging contaminants (ECs) or emerging pollutants is an important environmental problem. Heterogeneous photocatalytic treatment, as advanced oxidation treatment of wastewater effluents, has been proposed to solve this problem. In this paper, a heterogeneous photocatalytic process was studied for emergent contaminants
[...] Read more.
Water pollution from emerging contaminants (ECs) or emerging pollutants is an important environmental problem. Heterogeneous photocatalytic treatment, as advanced oxidation treatment of wastewater effluents, has been proposed to solve this problem. In this paper, a heterogeneous photocatalytic process was studied for emergent contaminants removal using paracetamol as a model contaminant molecule. TiO2 photocatalytic activity was evaluated using two photocatalytic reactor configurations: Photocatalyst solid suspension in wastewater in a stirred photoreactor and TiO2 supported on glass spheres (TGS) configuring a packed bed photoreactor. The surface morphology and texture of the TGS were monitored by scanning electron microscope (SEM). The influence of photocatalyst amount and wastewater pH were evaluated in the stirred photoreactor and the influence of wastewater flowrate was tested in the packed bed photoreactor, in order to obtain the optimal operation conditions. Moreover, results obtained were compared with those obtained from photolysis and adsorption studies, using the optimal operation conditions. Good photocatalytic activities have been observed and leads to the conclusion that the heterogeneous photocatalytic system in a packed bed is an effective method for removal of emerging pollutants. Full article
Open AccessArticle Valorisation of Vietnamese Rice Straw Waste: Catalytic Aqueous Phase Reforming of Hydrolysate from Steam Explosion to Platform Chemicals
Catalysts 2014, 4(4), 414-426; doi:10.3390/catal4040414
Received: 7 October 2014 / Revised: 20 November 2014 / Accepted: 27 November 2014 / Published: 15 December 2014
Cited by 6 | PDF Full-text (3046 KB) | HTML Full-text | XML Full-text
Abstract
A family of tungstated zirconia solid acid catalysts were synthesised via wet impregnation and subsequent thermochemical processing for the transformation of glucose to 5-hydroxymethylfurfural (HMF). Acid strength increased with tungsten loading and calcination temperature, associated with stabilisation of tetragonal zirconia. High tungsten dispersions
[...] Read more.
A family of tungstated zirconia solid acid catalysts were synthesised via wet impregnation and subsequent thermochemical processing for the transformation of glucose to 5-hydroxymethylfurfural (HMF). Acid strength increased with tungsten loading and calcination temperature, associated with stabilisation of tetragonal zirconia. High tungsten dispersions of between 2 and 7 W atoms·nm−2 were obtained in all cases, equating to sub-monolayer coverages. Glucose isomerisation and subsequent dehydration via fructose to HMF increased with W loading and calcination temperature up to 600 °C, indicating that glucose conversion to fructose was favoured over weak Lewis acid and/or base sites associated with the zirconia support, while fructose dehydration and HMF formation was favoured over Brönsted acidic WOx clusters. Aqueous phase reforming of steam exploded rice straw hydrolysate and condensate was explored heterogeneously for the first time over a 10 wt% WZ catalyst, resulting in excellent HMF yields as high as 15% under mild reaction conditions. Full article
Open AccessArticle Catalytic Glycerol Hydrodeoxygenation under Inert Atmosphere: Ethanol as a Hydrogen Donor
Catalysts 2014, 4(4), 397-413; doi:10.3390/catal4040397
Received: 14 October 2014 / Revised: 24 November 2014 / Accepted: 27 November 2014 / Published: 15 December 2014
Cited by 6 | PDF Full-text (10693 KB) | HTML Full-text | XML Full-text
Abstract
Glycerol hydrodeoxygenation to 1,2-propanediol (1,2-PDO) is a reaction of high interest. However, the need for hydrogen supply is a main drawback of the process. According to the concept investigated here, 1,2-propanediol is efficiently formed using bio-glycerol feedstock with H2 formed in situ
[...] Read more.
Glycerol hydrodeoxygenation to 1,2-propanediol (1,2-PDO) is a reaction of high interest. However, the need for hydrogen supply is a main drawback of the process. According to the concept investigated here, 1,2-propanediol is efficiently formed using bio-glycerol feedstock with H2 formed in situ via ethanol aqueous phase reforming. Ethanol is thought to be a promising H2 source, as it is alcohol that can be used instead of methanol for transesterification of oils and fats. The H2 generated is consumed in the tandem reaction of glycerol hydrodeoxygenation. The reaction cycle proceeds in liquid phase at 220–250 °C and 1.5–3.5 MPa initial N2 pressure for a 2 and 4-h reaction time. Pt-, Ni- and Cu-based catalysts have been synthesized, characterized and evaluated in the reaction. Among the materials tested, Pt/Fe2O3-Al2O3 exhibited the most promising performance in terms of 1,2-propanediol productivity, while reusability tests showed a stable behavior. Structural integrity and no formation of carbonaceous deposits were verified via Temperature Programmed Desorption of hydrogen (TPD-H2) and thermogravimetric analysis of the fresh and used Pt/FeAl catalyst. A study on the effect of various operating conditions (reaction time, temperature and pressure) indicated that in order to maximize 1,2-propanediol productivity and yield, milder reaction conditions should be applied. The highest 1,2-propanediol yield, 53% (1.1 g1,2-PDO gcat−1·h−1), was achieved at a lower reaction temperature of 220 °C. Full article
Figures

Review

Jump to: Editorial, Research

Open AccessReview Acyclic Diene Metathesis (ADMET) Polymerization for Precise Synthesis of Defect-Free Conjugated Polymers with Well-Defined Chain Ends
Catalysts 2015, 5(2), 500-517; doi:10.3390/catal5020500
Received: 1 December 2014 / Revised: 26 January 2015 / Accepted: 9 March 2015 / Published: 30 March 2015
Cited by 9 | PDF Full-text (8635 KB) | HTML Full-text | XML Full-text
Abstract
This accounts introduces unique characteristics by adopting the acyclic diene metathesis (ADMET) polymerization for synthesis of conjugated polymers, poly(arylene vinylene)s, known as promising molecular electronics. The method is more suitable than the other methods in terms of atom efficiency affording defect-free, stereo-regular (exclusive
[...] Read more.
This accounts introduces unique characteristics by adopting the acyclic diene metathesis (ADMET) polymerization for synthesis of conjugated polymers, poly(arylene vinylene)s, known as promising molecular electronics. The method is more suitable than the other methods in terms of atom efficiency affording defect-free, stereo-regular (exclusive trans) polymers with well-defined chain ends; the resultant polymers possess better property than those prepared by the conventional methods. The chain ends (vinyl group) in the resultant polymer prepared by ruthenium-carbene catalyst(s) can be modified by treating with molybdenum-alkylidene complex (olefin metathesis) followed by addition of various aldehyde (Wittig type cleavage), affording the end-functionalized polymers exclusively. An introduction of initiating fragment, the other conjugated segment, and one-pot synthesis of end-functionalized block copolymers, star shape polymers can be achieved by adopting this methodology. Full article
Open AccessReview B-Site Metal (Pd, Pt, Ag, Cu, Zn, Ni) Promoted La1−xSrxCo1−yFeyO3–δ Perovskite Oxides as Cathodes for IT-SOFCs
Catalysts 2015, 5(1), 366-391; doi:10.3390/catal5010366
Received: 19 September 2014 / Revised: 22 February 2015 / Accepted: 3 March 2015 / Published: 12 March 2015
Cited by 10 | PDF Full-text (3358 KB) | HTML Full-text | XML Full-text
Abstract
Perovskite oxides La1−xSrxCo1−yFeyO3–δ (LSCF) have been extensively investigated and developed as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) due to mixed ionic–electronic conductivity and high electrooxygen reduction activity for
[...] Read more.
Perovskite oxides La1−xSrxCo1−yFeyO3–δ (LSCF) have been extensively investigated and developed as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) due to mixed ionic–electronic conductivity and high electrooxygen reduction activity for oxygen reduction. Recent literature investigations show that cathode performances can be improved by metal surface modification or B-site substitution on LSCF. Although the specific reaction mechanism needs to be further investigated, the promoting effect of metal species in enhancing oxygen surface exchange and oxygen bulk diffusion is well recognized. To our knowledge, no previous reviews dealing with the effect of metal promotion on the cathodic performances of LSCF materials have been reported. In the present review, recent progresses on metal (Pd, Pt, Ag, Cu, Zn, Ni) promotion of LSCF are discussed focusing on two main aspects, the different synthesis approaches used (infiltration, deposition, solid state reaction, one pot citrate method) and the effects of metal promotion on structural properties, oxygen vacancies content and cathodic performances. The novelty of the work lies in the fact that the metal promotion at the B-site is discussed in detail, pointing at the effects produced by two different approaches, the LSCF surface modification by the metal or the metal ion substitution at the B-site of the perovskite. Moreover, for the first time in a review article, the importance of the combined effects of oxygen dissociation rate and interfacial oxygen transfer rate between the metal phase and the cathode phase is addressed for metal-promoted LSCF and compared with the un-promoted oxides. Perspectives on new research directions are shortly given in the conclusion. Full article
Figures

Open AccessReview Fischer-Tropsch Synthesis on Multicomponent Catalysts: What Can We Learn from Computer Simulations?
Catalysts 2015, 5(1), 3-17; doi:10.3390/catal5010003
Received: 28 November 2014 / Accepted: 24 December 2014 / Published: 9 January 2015
Cited by 8 | PDF Full-text (2230 KB) | HTML Full-text | XML Full-text
Abstract
In this concise review paper, we will address recent studies based on the generalized-gradient approximation (GGA) of the density functional theory (DFT) and on the periodic slab approach devoted to the understanding of the Fischer-Tropsch synthesis process on transition metal catalysts. As it
[...] Read more.
In this concise review paper, we will address recent studies based on the generalized-gradient approximation (GGA) of the density functional theory (DFT) and on the periodic slab approach devoted to the understanding of the Fischer-Tropsch synthesis process on transition metal catalysts. As it will be seen, this computational combination arises as a very adequate strategy for the study of the reaction mechanisms on transition metal surfaces under well-controlled conditions and allows separating the influence of different parameters, e.g., catalyst surface morphology and coverage, influence of co-adsorbates, among others, in the global catalytic processes. In fact, the computational studies can now compete with research employing modern experimental techniques since very efficient parallel computer codes and powerful computers enable the investigation of more realistic molecular systems in terms of size and composition and to explore the complexity of the potential energy surfaces connecting reactants, to intermediates, to products of reaction. In the case of the Fischer-Tropsch process, the calculations were used to complement experimental work and to clarify the reaction mechanisms on different catalyst models, as well as the influence of additional components and co-adsorbate species in catalyst activity and selectivity. Full article
Figures

Back to Top