Special Issue "Structured and Micro-Structured Catalysts and Reactors"

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

Deadline for manuscript submissions: closed (15 September 2017)

Special Issue Editors

Guest Editor
Prof. Dr. Luis M. Gandía

Institute for Advanced Materials (INAMAT), Universidad Pública de Navarra, Pamplona, Spain
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Interests: heterogeneous catalysis; structured catalytic reactors engineering; natural gas conversion; fuel processors; biofuels; hydrogen energy; chemical kinetics and computational fluid dynamics (CFD) applied to chemical reactors
Guest Editor
Prof. Mario Montes

Department of Applied Chemistry, University of the Basque Country, San Sebastián, Spain
E-Mail
Interests: Structured Catalysts and Reactors; Monolith Catalysts; Microchannel Reactors; Fischer-Tropsch Synthesis; Biofuels; Dimethyl Ether
Guest Editor
Prof. José Antonio Odriozola

Inorganic Chemistry Department and Materials Science Institute. University of Sevilla - CSIC. Address: Av. Americo Vespucio 49, 41092 Sevilla, Spain
Website1 | Website2 | E-Mail
Interests: Catalysis; Structured Catalysts and Reactors; Gold Catalysts; Water-Gas-Shift; Fuel Processors

Special Issue Information

Dear Colleagues,

Structured catalysts and reactors (SC&R) are being successfully employed in a number of processes, mostly related with Environmental Catalysis applications. These well-stablished technologies include the control of pollutants emissions from transportation vehicles, of NOx emissions from stationary sources or the removal of volatile organic compounds and the catalytic combustion for power generation plants. The selective catalytic reduction of NOx in power and nitric acid production plants, refineries and waste incinerators is an excellent example of the use of SC&R.

SC&R are characterized by relatively large void fractions and many more ordered paths of the fluids compared to conventional packed beds of particulate catalysts. These facts together with the laminar regime that typically governs the flow of the fluids lead up to two orders of magnitude lower pressure drops in structured reactors than in fixed-bed reactors. This opens the possibility of using SC&R in processes involving very high flow rates of the reactants (environmental applications) or requiring very short contact times, such as in the selective oxidation of hydrocarbons.

In the case of the micro-structured systems, such as microreactors and catalytic-wall microchannel reactors, the very small characteristic dimensions (typically below 1 mm) prevailing in these devices allow a significant enhancement of the mass and heat transport rates. This results in an incomparable intensification of the process with an excellent temperature control, and improved product quality and process safety.

Structured catalysts normally consist in a ceramic or metallic substrate that can adopt several configurations, such as parallel channels monoliths, open cell foams, stacked wire meshes, and microchannel reactors. The substrate provides structural entity and determines the flow pattern of the fluids inside the reactor. The catalyst, typically composed of a porous support, the active component, and eventually modifiers to tune some properties or provide new ones, is incorporated in the form of a thin layer that coats the substrate walls or even forming micro-packed-beds inside the substrate cavities.

Structured catalysts based on ceramic substrates are being traditionally employed in a number of applications. On the other hand, the use of metallic substrates is being increasingly considered for reactions with a strong thermal effect for which a very good heat transfer capacity is required in order to avoid problems associated to hot spots and temperature gradients. Nevertheless, preparing structured catalysts on metallic substrates remains still challenging due to the difficulties associated to the deposition of the catalyst on the substrate surface. The formation of homogeneous and adherent thin layers of catalyst on these substrates is very difficult and the procedures employed are in many cases halfway between science and art. These difficulties are related with the very different characteristics of the substrate and the catalyst, the modifications suffered by the catalyst during the deposition process, and the increasing complexities of the shapes of the new substrate designs and of the new technology employed, such as in the case of additive manufacturing.

In this context, the aim of this Special Issue is to collect a series of novel contributions in the field of SC&R and microreactors that allow updating the state-of-the-art. The special issue is devoted although not limited to parallel channels monoliths, open cell foams, stacked wire meshes and microchannel reactors. Topics to be covered are SC&R preparation and characterization, microreactors fabrication and applications for process intensification, as well as modeling and simulation of SC&R and microreactors.

Prof. Luis M. Gandía
Prof. Mario Montes
Prof. José Antonio Odriozola

Guest Editors

Manuscript Submission Information

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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 1000 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

structured catalysts and reactors; monoliths; foams; meshes; microreactors; microchannels; coating; catalytic layer; thermal properties

Published Papers (3 papers)

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Research

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Open AccessArticle DeNOx Abatement Modelling over Sonically Prepared Copper USY and ZSM5 Structured Catalysts
Catalysts 2017, 7(7), 205; doi:10.3390/catal7070205
Received: 24 May 2017 / Revised: 29 June 2017 / Accepted: 30 June 2017 / Published: 6 July 2017
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Abstract
Metallic supports play an important role as structured reactor internals. Due to their specific properties including enhanced heat and mass transport, high mechanical resistivity and elimination of local hot-spots, they are commonly used in gas exhaust abatement from stationary and automotive industries. In
[...] Read more.
Metallic supports play an important role as structured reactor internals. Due to their specific properties including enhanced heat and mass transport, high mechanical resistivity and elimination of local hot-spots, they are commonly used in gas exhaust abatement from stationary and automotive industries. In this study, the performance of three structured supports with deposited Cu/USY (Ultrastabilised Y—zeolite) for deNOx abatement were modelled. Based on kinetic and flow resistance experimental results, the one-dimensional (1D) model of structured reactor was developed. The performance of the structured reactors was compared by the length of the reactor necessary to achieve an arbitrary 90% NOx conversion. The performed simulations showed that the sonochemically prepared copper USY and ZSM-5 zeolites deposited on metallic supports may be successfully used as catalysts for deNOx process. Full article
(This article belongs to the Special Issue Structured and Micro-Structured Catalysts and Reactors)
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Open AccessArticle In Search of Governing Gas Flow Mechanism through Metal Solid Foams
Catalysts 2017, 7(4), 124; doi:10.3390/catal7040124
Received: 9 February 2017 / Revised: 11 April 2017 / Accepted: 17 April 2017 / Published: 21 April 2017
Cited by 1 | PDF Full-text (4749 KB) | HTML Full-text | XML Full-text
Abstract
Solid foams have been intensely studied as promising structured catalytic internals. However, mechanisms governing flow and transport phenomena within the foam structures have not been properly addressed in the literature. The aim of this study was to consider such flow mechanisms based on
[...] Read more.
Solid foams have been intensely studied as promising structured catalytic internals. However, mechanisms governing flow and transport phenomena within the foam structures have not been properly addressed in the literature. The aim of this study was to consider such flow mechanisms based on our experimental results on flow resistance. Two mechanisms were considered: developing laminar flow in a short capillary channel (flow-through model), and flow around an immersed solid body, either a cylinder or sphere (flow-around model). Flow resistance experiments were performed on three aluminum foams of 10, 20, and 40 PPI (pores per inch), using a 57 mm ID test column filled with the foams studied. The foam morphology was examined using microtomography and optical microscopy to derive the geometric parameters applied in the model equations. The flow-through model provided an accuracy of 25% for the experiments. The model channel diameter was the foam cell diameter, and the channel length was the strut thickness. The accuracy of the flow-around model was only slightly worse (35%). It was difficult to establish the geometry of the immersed solid body (sphere or cylinder) because experiment characteristics tended to change from sphere to cylinder with increasing PPI value. Full article
(This article belongs to the Special Issue Structured and Micro-Structured Catalysts and Reactors)
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Review

Jump to: Research

Open AccessFeature PaperReview Nano-Array Integrated Structured Catalysts: A New Paradigm upon Conventional Wash-Coated Monolithic Catalysts?
Catalysts 2017, 7(9), 253; doi:10.3390/catal7090253
Received: 14 May 2017 / Revised: 12 August 2017 / Accepted: 17 August 2017 / Published: 28 August 2017
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Abstract
The monolithic catalyst, namely the structured catalyst, is one of the important categories of catalysts used in various fields, especially in catalytic exhaust after-treatment. Despite its successful application in conventional wash-coated catalysts in both mobile and stationary catalytic converters, washcoat-based technologies are facing
[...] Read more.
The monolithic catalyst, namely the structured catalyst, is one of the important categories of catalysts used in various fields, especially in catalytic exhaust after-treatment. Despite its successful application in conventional wash-coated catalysts in both mobile and stationary catalytic converters, washcoat-based technologies are facing multi-fold challenges, including: (1) high Pt-group metals (PGM) material loading being required, driving the market prices; (2) less-than ideal distribution of washcoats in typically square-shaped channels associated with pressure drop sacrifice; and (3) far from clear correlations between macroscopic washcoat structures and their catalytic performance. To tackle these challenges, the well-defined nanostructure array (nano-array)-integrated structured catalysts which we invented and developed recently have been proven to be a promising class of cost-effective and efficient devices that may complement or substitute wash-coated catalysts. This new type of structured catalysts is composed of honeycomb-structured monoliths, whose channel surfaces are grown in situ with a nano-array forest made of traditional binary transition metal oxide support such as Al2O3, CeO2, Co3O4, MnO2, TiO2, and ZnO, or newer support materials including perovskite-type ABO3 structures, for example LaMnO3, LaCoO3, LaNiO, and LaFeO3. The integration strategy parts from the traditional washcoat technique. Instead, an in situ nanomaterial assembly method is utilized, such as a hydro (solva-) thermal synthesis approach, in order to create sound structure robustness, and increase ease and complex-shaped substrate adaptability. Specifically, the critical fabrication procedures for nano-array structured catalysts include deposition of seeding layer, in situ growth of nano-array, and loading of catalytic materials. The generic methodology utilization in both the magnetic stirring batch process and continuous flow reactor synthesis offers the nano-array catalysts with great potential to be scaled up readily and cost-effectively. The tunability of the structure and catalytic performance could be achieved through morphology and geometry adjustment and guest atoms and defect manipulation, as well as composite nano-array catalyst manufacture. Excellent stabilities under various conditions were also present compared to conventional wash-coated catalysts. Full article
(This article belongs to the Special Issue Structured and Micro-Structured Catalysts and Reactors)
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