Special Issue "Iron and Cobalt Catalysts"

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

Deadline for manuscript submissions: 31 August 2019.

Special Issue Editors

Guest Editor
Prof. Wilson D Shafer

Science and Health Department, Asbury University, Lexington, KY 40390, USA
Website | E-Mail
Interests: clean energy; carbon dioxide utilization; heterogeneous catalysis processes such as Fischer-Tropsch synthesis, aromatization, steam reforming, and water–gas shift
Guest Editor
Prof. Gary Jacobs

University of Texas at San Antonio, Chemical Engineering Program – Department of Biomedical Engineering, Department of Mechanical Engineering, One UTSA Circle, San Antonio, TX 78249, USA
Website | E-Mail
Interests: heterogeneous catalysis; syngas conversion; hydrogen production

Special Issue Information

Dear Colleagues,

Since the turn of the last century—when the field of catalysis was born—iron and cobalt have been key players in numerous catalysis processes. These metals, because of their ability to activate CO and CH, remain a major economic impact worldwide. Several industrial processes and synthetic routes utilize these metals:

  • Biomass-to-Liquids (BTL),
  • Coal-to-Liquids (CTL),
  • Natural Gas-to-Liquids (GTL),
  • Water-Gas-Shift,
  • Alcohol Synthesis,
  • Alcohol Steam Reforming,
  • Polymerization Processes,
  • Cross-coupling Reactions,
  • Photocatalyst activated reactions.

A vast number of materials are produced from these processes, including oil, lubricants, waxes, diesel and jet fuels, hydrogen (e.g., fuel cell applications), gasoline, rubbers, plastics, alcohols, pharmaceuticals, agrochemicals, feed-stock chemicals and other alternative materials. However, given the true complexities of the variables involved in these processes, many key mechanistic issues are still not fully defined or understood.

This Special Issue of Catalysis will be a collaborative effort to combine current catalysis research on these metals, from experimental and theoretical perspectives on both heterogeneous and homogeneous catalysts.  We welcome contributions from the catalysis community on catalyst characterization, kinetics, reaction mechanism, reactor development, theoretical modeling, and surface science are all welcome. 

Prof. Wilson D Shafer
Prof. Gary Jacobs
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 papers will be 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 1600 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

  • Iron
  • Cobalt
  • Catalysis
  • CO activation
  • CH activation

Published Papers (7 papers)

View options order results:
result details:
Displaying articles 1-7
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle
Comparative Studies of Fischer-Tropsch Synthesis on Iron Catalysts Supported on Al2O3-Cr2O3 (2:1), Multi-Walled Carbon Nanotubes or BEA Zeolite Systems
Catalysts 2019, 9(7), 605; https://doi.org/10.3390/catal9070605
Received: 30 May 2019 / Revised: 1 July 2019 / Accepted: 8 July 2019 / Published: 15 July 2019
PDF Full-text (5996 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The main goal of the presented paper is to study the influence of a range of support materials, i.e., multi-walled carbon nanotubes (MWCNTs), Al2O3-Cr2O3 (2:1), zeolite β-H and zeolite β-Na on the physicochemical and catalytic properties [...] Read more.
The main goal of the presented paper is to study the influence of a range of support materials, i.e., multi-walled carbon nanotubes (MWCNTs), Al2O3-Cr2O3 (2:1), zeolite β-H and zeolite β-Na on the physicochemical and catalytic properties in Fischer-Tropsch (F-T) synthesis. All tested Fe catalysts were synthesized using the impregnation method. Their physicochemical properties were extensively investigated using various characterization techniques such as the Temperature-Programmed Reduction of hydrogen (TPR-H2), X-ray diffraction, Temperature-Programmed Desorption of ammonia (TPD-NH3), Temperature-Programmed Desorption of carbon dioxide (TPD-CO2), Fourier transform infrared spectrometry (FTIR), Brunauer Emmett Teller method (BET) and Thermogravimetric Differential Analysis coupled with Mass Spectrometer (TG-DTA-MS). Activity tests were performed in F-T synthesis using a high-pressure fixed bed reactor and a gas mixture of H2 and CO (50% CO and 50% H2). The correlation between the physicochemical properties and reactivity in F-T synthesis was determined. The highest activity was from a 40%Fe/Al2O3-Cr2O3 (2:1) system which exhibited 89.9% of CO conversion and 66.6% selectivity toward liquid products. This catalyst also exhibited the lowest acidity, but the highest quantity of iron carbides on its surface. In addition, in the case of iron catalysts supported on MWCNTs or a binary oxide system, the smallest amount of carbon deposit formed on the surface of the catalyst during the F-T process was confirmed. Full article
(This article belongs to the Special Issue Iron and Cobalt Catalysts)
Figures

Graphical abstract

Open AccessArticle
Investigation of C1 + C1 Coupling Reactions in Cobalt-Catalyzed Fischer-Tropsch Synthesis by a Combined DFT and Kinetic Isotope Study
Catalysts 2019, 9(6), 551; https://doi.org/10.3390/catal9060551
Received: 2 June 2019 / Revised: 13 June 2019 / Accepted: 17 June 2019 / Published: 19 June 2019
PDF Full-text (2617 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Understanding the chain growth mechanism is of vital importance for the development of catalysts with enhanced selectivity towards long-chain products in cobalt-catalyzed Fischer-Tropsch synthesis. Herein, we discriminate various C1 + C1 coupling reactions by theoretical calculations and kinetic isotope experiments. CH [...] Read more.
Understanding the chain growth mechanism is of vital importance for the development of catalysts with enhanced selectivity towards long-chain products in cobalt-catalyzed Fischer-Tropsch synthesis. Herein, we discriminate various C1 + C1 coupling reactions by theoretical calculations and kinetic isotope experiments. CHx(x=0−3), CO, HCO, COH, and HCOH are considered as the chain growth monomer respectively, and 24 possible coupling reactions are first investigated by theoretical calculations. Eight possible C1 + C1 coupling reactions are suggested to be energetically favorable because of the relative low reaction barriers. Moreover, five pathways are excluded where the C1 monomers show low thermodynamic stability. Effective chain propagation rates are calculated by deconvoluting from reaction rates of products, and an inverse kinetic isotope effect of the C1 + C1 coupling reaction is observed. The theoretical kinetic isotope effect of CO + CH2 is inverse, which is consistent with the experimental observation. Thus, the CO + CH2 pathway, owing to the relatively lower barrier, the high thermodynamic stability, and the inverse kinetic isotope effect, is suggested to be a favorable pathway. Full article
(This article belongs to the Special Issue Iron and Cobalt Catalysts)
Figures

Graphical abstract

Open AccessArticle
Liquid-Phase Catalytic Oxidation of Limonene to Carvone over ZIF-67(Co)
Catalysts 2019, 9(4), 374; https://doi.org/10.3390/catal9040374
Received: 15 March 2019 / Revised: 6 April 2019 / Accepted: 16 April 2019 / Published: 21 April 2019
PDF Full-text (4201 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Liquid-phase catalytic oxidation of limonene was carried out under mild conditions, and carvone was produced in the presence of ZIF-67(Co), cobalt based zeolitic imidazolate framework, as catalyst, using t-butyl hydroperoxide (t-BHP) as oxidant and benzene as solvent. As a heterogeneous catalyst, the zeolitic [...] Read more.
Liquid-phase catalytic oxidation of limonene was carried out under mild conditions, and carvone was produced in the presence of ZIF-67(Co), cobalt based zeolitic imidazolate framework, as catalyst, using t-butyl hydroperoxide (t-BHP) as oxidant and benzene as solvent. As a heterogeneous catalyst, the zeolitic imidazolate framework ZIF-67(Co) exhibited reasonable substrate–product selectivity (55.4%) and conversion (29.8%). Finally, the X-ray diffraction patterns of the catalyst before and after proved that ZIF-67(Co) acted as a heterogeneous catalyst, and can be reused without losing its activity to a great extent. Full article
(This article belongs to the Special Issue Iron and Cobalt Catalysts)
Figures

Figure 1

Open AccessArticle
The Effect of Potassium on Cobalt-Based Fischer–Tropsch Catalysts with Different Cobalt Particle Sizes
Catalysts 2019, 9(4), 351; https://doi.org/10.3390/catal9040351
Received: 15 February 2019 / Revised: 2 April 2019 / Accepted: 8 April 2019 / Published: 10 April 2019
PDF Full-text (1012 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The effect of K on 20%Co/0.5%Re/γ-Al2O3 Fischer–Tropsch catalysts with two different cobalt particle sizes (small, in the range 6–7 nm and medium size, in the range 12–13 nm) was investigated. The catalyst with the smaller cobalt particle size had a [...] Read more.
The effect of K on 20%Co/0.5%Re/γ-Al2O3 Fischer–Tropsch catalysts with two different cobalt particle sizes (small, in the range 6–7 nm and medium size, in the range 12–13 nm) was investigated. The catalyst with the smaller cobalt particle size had a lower catalytic activity and C5+ selectivity while selectivities towards CH4 and CO2 were slightly higher than over the catalyst with larger particles. These effects are ascribed to lower hydrogen concentration on the surface as well as the lower reducibility of smaller cobalt particles. Upon potassium addition all samples showed decreased catalytic activity, reported as Site Time Yield (STY), increased C5+ and CO2 selectivities, and a decrease in CH4 selectivity. There was no difference in the effect of potassium between the sample with small cobalt particles compared to the sample with medium size particles). In both cases the specific activity (STY) fell and the C5+ selectivity increased in a similar fashion. Full article
(This article belongs to the Special Issue Iron and Cobalt Catalysts)
Figures

Figure 1

Open AccessArticle
Fischer–Tropsch: Product Selectivity–The Fingerprint of Synthetic Fuels
Catalysts 2019, 9(3), 259; https://doi.org/10.3390/catal9030259
Received: 16 February 2019 / Revised: 3 March 2019 / Accepted: 7 March 2019 / Published: 14 March 2019
Cited by 1 | PDF Full-text (19782 KB) | HTML Full-text | XML Full-text
Abstract
The bulk of the products that were synthesized from Fischer–Tropsch synthesis (FTS) is a wide range (C1–C70+) of hydrocarbons, primarily straight-chained paraffins. Additional hydrocarbon products, which can also be a majority, are linear olefins, specifically: 1-olefin, trans-2-olefin, and [...] Read more.
The bulk of the products that were synthesized from Fischer–Tropsch synthesis (FTS) is a wide range (C1–C70+) of hydrocarbons, primarily straight-chained paraffins. Additional hydrocarbon products, which can also be a majority, are linear olefins, specifically: 1-olefin, trans-2-olefin, and cis-2-olefin. Minor hydrocarbon products can include isomerized hydrocarbons, predominantly methyl-branched paraffin, cyclic hydrocarbons mainly derived from high-temperature FTS and internal olefins. Combined, these products provide 80–95% of the total products (excluding CO2) generated from syngas. A vast number of different oxygenated species, such as aldehydes, ketones, acids, and alcohols, are also embedded in this product range. These materials can be used to probe the FTS mechanism or to produce alternative chemicals. The purpose of this article is to compare the product selectivity over several FTS catalysts. Discussions center on typical product selectivity of commonly used catalysts, as well as some uncommon formulations that display selectivity anomalies. Reaction tests were conducted while using an isothermal continuously stirred tank reactor. Carbon mole percentages of CO that are converted to specific materials for Co, Fe, and Ru catalysts vary, but they depend on support type (especially with cobalt and ruthenium) and promoters (especially with iron). All three active metals produced linear alcohols as the major oxygenated product. In addition, only iron produced significant selectivities to acids, aldehydes, and ketones. Iron catalysts consistently produced the most isomerized products of the catalysts that were tested. Not only does product selectivity provide a fingerprint of the catalyst formulation, but it also points to a viable proposed mechanistic route. Full article
(This article belongs to the Special Issue Iron and Cobalt Catalysts)
Figures

Figure 1

Open AccessArticle
Pilot-Scale Production, Properties and Application of Fe/Cu Catalytic-Ceramic-Filler for Nitrobenzene Compounds Wastewater Treatment
Catalysts 2019, 9(1), 11; https://doi.org/10.3390/catal9010011
Received: 4 December 2018 / Revised: 18 December 2018 / Accepted: 19 December 2018 / Published: 25 December 2018
PDF Full-text (5409 KB) | HTML Full-text | XML Full-text
Abstract
Iron powder, Kaolin powder and CuSO4∙5H2O were employed as the main materials for the pilot-scale production of Fe/Cu catalytic- ceramic-filler (CCF) by way of wet type replacement-thermo-solidification. The physical properties, half-life, microstructure, removal rate of nitrobenzene compounds and the [...] Read more.
Iron powder, Kaolin powder and CuSO4∙5H2O were employed as the main materials for the pilot-scale production of Fe/Cu catalytic- ceramic-filler (CCF) by way of wet type replacement-thermo-solidification. The physical properties, half-life, microstructure, removal rate of nitrobenzene compounds and the biodegradability-improvement of military chemical factory comprehensive wastewater were tested in comparison with commercial Fe/C ceramic-filler (CF). Catalytic micro-electrolysis bed reactors (CBRs) designed as pretreatment process and BAFs (Biological Aerated Filters) were utilized in a 90 days field pilot-scale test at last. The results showed the characteristics of optimum CCF were: 1150 kg/m3 of bulk density, 1700 kg/m3 of grain density, lower than 3.5% of shrinking ratio, 3.5% of 24 h water absorption, 6.0 Mpa of numerical tube pressure, 0.99 acid-resistance softening co-efficiency and 893.55 days of half-life. 25% addition of Fe with 1% of copper plating rate was efficient for the removal of nitrobenzene compounds and significant in promoting the biodegradability of military chemical factory comprehensive wastewater. The two-stage design of CBRs and BAFs showed high dependability and stability for the practical engineering application. Full article
(This article belongs to the Special Issue Iron and Cobalt Catalysts)
Figures

Figure 1

Review

Jump to: Research

Open AccessFeature PaperReview
Polynuclear Cobalt Complexes as Catalysts for Light-Driven Water Oxidation: A Review of Recent Advances
Catalysts 2018, 8(12), 602; https://doi.org/10.3390/catal8120602
Received: 5 November 2018 / Revised: 21 November 2018 / Accepted: 27 November 2018 / Published: 2 December 2018
Cited by 3 | PDF Full-text (8529 KB) | HTML Full-text | XML Full-text
Abstract
Photochemical water oxidation, as a half-reaction of water splitting, represents a great challenge towards the construction of artificial photosynthetic systems. Complexes of first-row transition metals have attracted great attention in the last decade due to their pronounced catalytic efficiency in water oxidation, comparable [...] Read more.
Photochemical water oxidation, as a half-reaction of water splitting, represents a great challenge towards the construction of artificial photosynthetic systems. Complexes of first-row transition metals have attracted great attention in the last decade due to their pronounced catalytic efficiency in water oxidation, comparable to that exhibited by classical platinum-group metal complexes. Cobalt, being an abundant and relatively cheap metal, has rich coordination chemistry allowing construction of a wide range of polynuclear architectures for the catalytic purposes. This review covers recent advances in application of cobalt complexes as (pre)catalysts for water oxidation in the model catalytic system comprising [Ru(bpy)3]2+ as a photosensitizer and S2O82− as a sacrificial electron acceptor. The catalytic parameters are summarized and discussed in view of the structures of the catalysts. Special attention is paid to the degradation of molecular catalysts under catalytic conditions and the experimental methods and techniques used to control their degradation as well as the leaching of cobalt ions. Full article
(This article belongs to the Special Issue Iron and Cobalt Catalysts)
Figures

Figure 1

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Fischer-Tropsch synthesis: Effect of potassium sources on FT activity and product selectivity”
Authors: M.K. Gnanamani, G. Jacobs, M. Martinelli, D. Sparks, W.D. Shafer
Affiliation: Center for Applied Energy Research, University of Kentucky, Lexington KY, USA

Title: Deuterium study of Fe and Ru catalyzed Fisher-Tropsch synthesis
Authors: Buchang Shi
Affiliation: Department of Chemistry, Eastern Kentucky University, USA

Title: Effect of co-feeding inorganic and organic molecules in the Fe and Co catalyzed Fischer–Tropsch synthesis: a review
Authors: Adolph Anga Muleja, Joshua Gorimbo, Prof. Cornelius Mduduzi Masuku
Affiliation: Department of Civil and Chemical Engineering, University of South Africa, Private Bag X6, Florida, 1710, South Africa
Abstract: This short review makes it clear that after 90 years, the Fischer–Tropsch synthesis (FTS) process is very far from understood. While it is agreed that it is primarily a polymerisation process giving rise to a distribution of mainly olefins and paraffins, the mechanism by which this occurs on catalysts is still the subject of much debate. Many of the FT features such as deactivation; product distributions; kinetics and mechanism; and equilibrium aspects of the FT processes are still subjects of controversy, regardless of the progress that has been made so far. The effect of molecules co-feeding in FTS on these features is the main focus of this study. This review will look at some of these areas and try to throw some light on some of the aspects of FTS since the inception of the idea to date with emphasis and recommendation made based on nitrogen, water, ammonia, and olefins co-feeding case studies.

Title: Cobalt pincer complex for catalysis
Author: Huiguang Dai
Affiliation: Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States

Title: Recent progress on heterogeneous Fe/Co-catalyzed biomass conversions
Author: Dr. Jiang Li
Affiliation: State Key Laboratory of Heavy Oil Processing, Institute of New Energy, China University of Petroleum (Beijing), Beijing, China

Title: Effect of Metallic Promoters on Cobalt Fischer-Tropsch Synthesis Catalyst
Authors: Mingsheng Luo*, He Li, Zuoxing Di*
Affiliation: Center for Applied Energy and Environmental Research, Beijing Institute of Petrochemical Technology, 19 Qing-Yuan North Road, Beijing 102600, China
Abstract: A series of studies were conducted to investigate the effect of some metallic promoters, i.e., Cu, La, Mg, Fe, Ce, on reducibility of an alumina supported cobalt Fischer-Tropsch Synthesis (FTS) catalyst.  Cobalt (20%) catalyst used in this study was prepared with alumina by incipient wetness.  Each of the promoters was added to the base cobalt catalyst at 4% loading.  It is found that iron promoted catalyst yielded the largest Co3O4 crystallite, while other promoters showed little effect on it.  The only amorphous Co3O4 crystallite was generated from iron promoted sample. BET data shows that the largest surface area was yielded from copper promoted sample, and copper also enhanced the reducibility of the catalyst; however, copper promoted catalyst produced the lowest CO conversion probably due to its thermal sensitivity to temperature in the reduction process. It also shows that only La significantly enhanced the CO conversion, while Fe and Mg lowered the CO conversion.
Keywords: Fischer-Tropsch Synthesis; Gas-to-Liquid, Cerium; Copper; Magnesium; Iron; Lanthanum; Cobalt Catalyst; Promotion; Syngas

Title: The effect of potassium on cobalt-based Fischer-Tropsch catalysts with different cobalt particle sizes
Authors: Ljubiša Gavrilović, Jonas Save and Edd A. Blekkan
Affiliation: Catalysis Group, Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway
Abstract: The effect of K on a 20%Co/0.5%Re/γ-Al2O3 catalysts with two different cobalt particle sizes (small, in the range 6-7 nm and medium size, in the range 12-13 nm) was investigated. The catalyst with the smaller cobalt particle size had a lower specific catalytic activity and C5+ selectivity while selectivities towards CH4 and CO2 were slightly higher than over the catalyst with larger particles. These effects are ascribed to lower hydrogen concentration on the surface as well as the lower reducibility of smaller cobalt particles. Upon potassium addition all samples showed decreased catalytic activity (reported as Site Time Yield (STY)), increased C5+ and CO2 selectivities, and a decrease in CH4 selectivity. There was no difference in the effect of potassium between the sample with small cobalt particles compared to the sample with medium size particles 12-13 nm). In both cases the activity (STY) fell and the C5+ selectivity increased in a similar fashion.

Title: Fischer-Tropsch synthesis: Catalytic performance of 0.27%Ag-25%Co/Al2O3 catalysts in slurry phase and micro-channel reactors
Authors: Wenping Ma, Sandeep Badoga, Gary Jacobs, Wilson D. Shafer, Dennis, Sparks, and Burtron H. Davis
Affiliation: Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, Kentucky, 40511 USA
Abstract: In this study, the FTS performance of 0.27%Ag-25%Co/Al2O3 catalysts in CSTR and a micro-channel reactor was comparatively studied using the same reduction and FTS conditions for example reduction: 350 oC, H2/He  for 36 h; FTS: 200-225 oC, 1.3 MPa, H2/CO ratio of 2.0 and ca. 50% CO conversion. In both reactors, the catalysts were examined for long period of time (550-1200 h). The catalyst activity and deactivation rate in the micro-channel reactor and CSTR reactor are comparable. During long time running, pressure drop in the micro reactor was low, less than 30 psig, and it demonstrated high hydrocarbon productivity and excellent heat change properties (temperature difference along bed: ± 0.5 oC). The results suggest that using micro-channel reactor is a viable path for the production of clean fuels through the XTL process. The effect of Al2O3 pore support and Ag promoter on the FTS performance were also investigated in this paper. The 0.27%Ag-25%Co/Al2O3 catalysts displayed ~50% higher activity than the unpromoted 25%Co/Al2O3 catalysts which was ascribed to the Ag significantly facilitated Co reduction. The activity and selectivity of the Ag-Co catalysts changed greatly with Al2O3 type. The wide pore HP14/150 Al2O3 benefited the formation of heavier hydrocarbon and catalyst stability, and greatly decreased methane formation. The better Co dispersion on the wide pore Al2O3 support could be a dominant reason for the favorite selectivity trend and good stability of the catalyst.  The narrow pore CS331-1 Al2O3 support displayed higher activity and higher 2-C4 olefin selectivity and C4 paraffin than the other two supports. It is postulated that the support has higher surface, and may contain more amount of acid sites, resulting higher activities of hydrogenation and secondary reaction of olefins.
Keywords: Fischer-Tropsch synthesis; Co/Al2O3; Ag; hydrocarbon selectivity; Micro-channel

Title: Iron-cobalt bimetal catalysts and their applications in energy-related electrochemical reactions
Authors: Yang Li, Xiaobin Fan
Affiliation: School of Chemical Engineering and Technology, Tianjin University, Tianjin 300354, China
Abstract: Since the persistently increasing trend of energy consumption, technologies for renewable energy production and conversion have drawn great attention worldwide. The performance and the cost of electrocatalysts play two crucial roles in the globalization of advanced energy conversion devices. Among the developed technics involving metal catalysts, transition-metal catalysts (TMC) are recognized the most promising materials due to the excellent properties and stability. Particularly, the iron-cobalt bimetal catalysts exhibit exciting electrochemical properties because of the interior cooperative effects. Herein, we summarize recent advances in iron-cobalt bimetal catalysts for electrochemical applications especially hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Moreover, the components and synergetic effects of the composites and catalytic mechanism during reaction processes are highlighted. On the basis of extant catalysts and mechanism, the current issues and prospective outlook of the field are also discussed.

Title: Reverse Water-Gas Shift Iron Catalyst Derived from Magnetite
Authors: Chen-Yu Chou, Jason A. Loiland, and Raul F. Lobo*
Affiliation: Center for Catalytic Science and Technology, Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716, USA
Abstract: The catalytic properties of unsupported iron oxides, specifically magnetite (Fe3O4), were investigated for the reverse water-gas shift (RWGS) reaction at temperatures between 723 K and 773 K and atmospheric pressure. This catalyst exhibited fast catalytic CO formation rate (35.1 mmol h-1 gcat.-1), high turnover frequency (0.180 s-1), high CO selectivity (>99%), and high stability (753K, 45000 cm3h-1gcat.-1) under 1:1 H2 to CO2 ratio. Reaction rates over Fe3O4 catalyst displayed a strong dependence on H2 partial pressure (reaction order of ~0.8) and a weaker dependence on CO2 partial pressure (reaction order of 0.33) under equimolar flow of both reactants. X-ray powder diffraction patterns and XPS spectra reveal that the bulk composition and structure of the post-reaction catalyst was formed mostly of metallic Fe and Fe3C while the surface contained Fe2+, Fe3+, metallic Fe, and Fe3C. Catalyst tests on pure Fe3C (iron carbide) suggest that Fe3C is not an effective catalyst for this reaction at the conditions investigated. Gas-switching experiments (CO2 or H2) indicate that a redox mechanism is the predominant reaction pathway.

Title: The evolution of catalysis for alkyd coatings: responding to impending cobalt reclassification with very active iron and manganese catalysts with polydentate nitrogen donor ligands
Authors: Neil Simpson, Devlin Riley and Ronald Hage
Affiliation: Borchers GmbH. Langenfeld, North Rhine-Westphalia, Germany
Abstract: Autoxidation processes to achieve curing of alkyd resins in paints, inks and coatings are ubiquitous in many applications. Cobalt soaps have been employed for these applications for many decades and most of the paint and ink alkyd resin formulations have been optimised to achieve optimal benefits of the cobalt soaps. However, cobalt soaps are under increased scrutiny because of likely reclassification as carcinogenic under REACH (Registration, Evaluation, Authorisation and Restrictions of Chemicals) legislation in Europe. This is critical, since such coatings are available for regular human contact. Alternative manganese- and iron-based driers have been developed to address this need for over a decade. They often show very high curing activity depending on the organic ligands bound to the metal centres. Recently, new classes of catalysts and modes of application have been published or patented to create safe paints, whilst delivering performance benefits via their unique reaction mechanisms. Besides the use of well-defined, preformed catalysts, paint formulations have also been developed with mixtures of metal soaps and ligands that form active species in-situ. The change from Co-soaps to Mn- and Fe-based driers meant that important coating issues related to radical-based curing, such as skinning, had to be rethought. In this paper we will review the new catalyst technologies and their performance and modes of action, as well as new compounds developed to provide anti-skinning benefits.

Catalysts EISSN 2073-4344 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top