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Special Issue "In Situ and Operando Characterization in Catalysis"

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

Deadline for manuscript submissions: closed (31 August 2016) | Viewed by 38918

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Dr. Juan J. Bravo-Suarez

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Chemical & Petroleum Engineering Department, The University of Kansas, Lawrence, KS 66045, USA
Interests: heterogeneous catalysis; advanced catalyst synthesis; in situ/operando spectroscopy and spectrokinetics; reaction kinetics; biomass and alternative feedstock conversion; oxidation reactions; fuels and chemicals
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Special Issue Information

Dear Colleagues,

The majority of today’s industrial chemical processes employ biocatalysts (e.g., enzymes), homogeneous and/or heterogeneous catalysts. With current worldwide challenges in food, energy, and water supplies, it is hard to imagine a future of yet-to-be-discovered solutions without catalysts. The development of energy and resource efficient catalytic process for production of ammonia (for fertilizers) and for conversion of biomass and abundant feedstocks to fuels and chemicals are just a few examples where novel active, selective, and stable catalysts will be required. To achieve this goal, many tools will be needed to enable a better understanding of how these catalysts work: where (required catalytic sites), how (reaction mechanism), and how fast (kinetics). In situ and/or operando (experimental and computational) catalyst characterization at reaction conditions is without any doubt poised to help us understand the intricacies of chemical conversions required for the design of better catalytic materials.

This Special Issue focuses on recent advances in experimental and computational in situ and operando spectroscopy/microscopy/diffraction characterization of catalysts, novel characterization methods, and in situ reactors, and novel analysis methodologies to better understand catalysts, reaction intermediates and mechanisms and how they can assist in the design of improved and novel catalysts. Full papers, communications, perspectives, and mini-reviews are most welcome.

Dr. Juan J Bravo-Suarez
Guest Editor

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 submissions that pass pre-check are 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 2700 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

In situ spectroscopy
In situ microscopic techniques
In situ X-ray diffraction
In situ electrochemical methods
Surface science techniques
Novel catalyst characterization techniques
Novel in situ reactors
Computational spectroscopy
Operando studies
Spectrokinetic studies
Steady state isotopic kinetic analysis
Modulation excitation spectroscopy
Spectroscopy/microscopy/diffraction assisted design of catalysts

Published Papers (6 papers)

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Research

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Open AccessArticle

Visualization of Gas Distribution in a Model AP-XPS Reactor by PLIF: CO Oxidation over a Pd(100) Catalyst

and

Catalysts 2017, 7(1), 29; https://doi.org/10.3390/catal7010029 - 17 Jan 2017

Cited by 19 | Viewed by 4919

Abstract

In situ knowledge of the gas phase around a catalyst is essential to make an accurate correlation between the catalytic activity and surface structure in operando studies. Although ambient pressure X-ray photoelectron spectroscopy (AP-XPS) can provide information on the gas phase as well as the surface structure of a working catalyst, the gas phase detected has not been spatially resolved to date, thus possibly making it ambiguous to interpret the AP-XPS spectra. In this work, planar laser-induced fluorescence (PLIF) is used to visualize the CO₂ distribution in a model AP-XPS reactor, during CO oxidation over a Pd(100) catalyst. The results show that the gas composition in the vicinity of the sample measured by PLIF is significantly different from that measured by a conventional mass spectrometer connected to a nozzle positioned just above the sample. In addition, the gas distribution above the catalytic sample has a strong dependence on the gas flow and total chamber pressure. The technique presented has the potential to increase our knowledge of the gas phase in AP-XPS, as well as to optimize the design and operating conditions of in situ AP-XPS reactors for catalysis studies. Full article

(This article belongs to the Special Issue In Situ and Operando Characterization in Catalysis)

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Open AccessArticle

Spatial Concentration Profiles for the Catalytic Partial Oxidation of Jet Fuel Surrogates in a Rh/Al₂O₃ Coated Monolith

and

Catalysts 2016, 6(12), 207; https://doi.org/10.3390/catal6120207 - 14 Dec 2016

Cited by 5 | Viewed by 5026

Abstract

The catalytic partial oxidation (CPOX) of several hydrocarbon mixtures, containing n-dodecane (DD), 1,2,4-trimethylbenzene (TMB), and benzothiophene (BT) as a sulfur compound was studied over a Rh/Al₂O₃ honeycomb catalyst. The in-situ sampling technique SpaciPro was used in this study to investigate the complex reaction system which consisted of total and partial oxidation, steam reforming, and the water gas shift reaction. The mixtures of 83 vol % DD, 17 vol % TMB with and without addition of the sulfur compound BT, as well as the pure hydrocarbons were studied at a molar C/O-ratio of 0.75. The spatially resolved concentration and temperature profiles inside a central channel of the catalyst revealed three reaction zones: an oxidation zone, an oxy-reforming zone, and a reforming zone. Hydrogen formation starts in the oxy-reforming zone, not directly at the catalyst inlet, contrary to methane CPOX on Rh. In the reforming zone, in which steam reforming is the predominant reaction, even small amounts of sulfur (10 mg S in 1 kg fuel) block active sites. Full article

(This article belongs to the Special Issue In Situ and Operando Characterization in Catalysis)

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Open AccessArticle

Effect of Surface Copper Species on NO + CO Reaction over xCuO-Ce_0.9Zr_0.1O₂ Catalysts: In Situ DRIFTS Studies

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Catalysts 2016, 6(8), 124; https://doi.org/10.3390/catal6080124 - 12 Aug 2016

Cited by 22 | Viewed by 6084

Abstract

In this work, the activity of xCuO-Ce_0.9Zr_0.1O₂ catalysts for the reaction of NO + CO was investigated. Especially, in situ DRIFTS was applied to investigate the surface species under the adsorption of NO and/or CO and the reaction of NO and CO to understand the key intermediates species and reaction process of NO + CO. The results suggest that the copper oxide species are well dispersed on the surface of the catalysts, which can be easily reduced to form Cu⁺ species. The Cu⁺ species are proposed to be important activity species. The results of this work also suggest that N₂O₂²⁻ is likely an intermediate species that plays an important role in NO reduction by CO. Thus, more Cu⁺ and highly dispersed copper oxide species are expected to be beneficial for the reaction of CO + NO over the xCuO-Ce_0.9Zr_0.1O₂ catalysts. Full article

(This article belongs to the Special Issue In Situ and Operando Characterization in Catalysis)

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Review

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Open AccessFeature PaperReview

Characterization of MoVTeNbO_x Catalysts during Oxidation Reactions Using In Situ/Operando Techniques: A Review

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Catalysts 2017, 7(4), 109; https://doi.org/10.3390/catal7040109 - 08 Apr 2017

Cited by 17 | Viewed by 5946

Abstract

Light alkanes are abundant in shale gas resources. The bulk mixed metal oxide MoVTe(Sb)NbO_x catalysts play a very important role in dehydrogenation and selective oxidation reactions of these short hydrocarbons to produce high-value chemicals. This catalyst system mainly consists of M1 and less-active M2 crystalline phases. Due to their ability to directly monitor the catalysts under the relevant industrial conditions, in situ/operando techniques can provide information about the nature of active sites, surface intermediates, and kinetics/mechanisms, and may help with the synthesis of new and better catalysts. Sophisticated catalyst design and understanding is necessary to achieve the desired performance (activity, selectivity, lifetime, etc.) at reasonable reaction conditions (temperature, pressure, etc.). This article critically reviews the progress made in research of these MoVTe(Sb)NbO_x catalysts in oxidation reactions mainly through in situ/operando techniques and suggests the future direction needed to realize the industrialization of these catalysts. Full article

(This article belongs to the Special Issue In Situ and Operando Characterization in Catalysis)

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Open AccessReview

Time Resolved Operando X-ray Techniques in Catalysis, a Case Study: CO Oxidation by O₂ over Pt Surfaces and Alumina Supported Pt Catalysts

Mark A. Newton

Catalysts 2017, 7(2), 58; https://doi.org/10.3390/catal7020058 - 14 Feb 2017

Cited by 32 | Viewed by 8489

Abstract

The catalytic oxidation of CO by O₂ to form CO₂ over Pt surfaces and supported catalysts is one of the most studied catalytic reactions from both fundamental and applied points of view. This review aims to show how the application of a range of time resolved, X-ray based techniques, such as X-ray diffraction (XRD), Surface X-ray diffraction (SXRD), total X-ray scattering/pair distribution function (PDF), X-ray absorption (XAFS), X-ray emission (XES), and X-ray photoelectron spectroscopies (XPS), applied under operando conditions and often coupled to adjunct techniques (for instance mass spectrometry (MS) and infrared spectroscopy (IR)) have shed new light on the structures and mechanisms at work in this most studied of systems. The aim of this review is therefore to demonstrate how a fusion of the operando philosophy with the ever augmenting capacities of modern synchrotron sources can lead to new insight and catalytic possibilities, even in the case of a process that has been intensely studied for almost 100 years. Full article

(This article belongs to the Special Issue In Situ and Operando Characterization in Catalysis)

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Open AccessReview

In Situ Spectroscopic Studies of Proton Transport in Zeolite Catalysts for NH₃-SCR

Peirong Chen

and

Ulrich Simon

Catalysts 2016, 6(12), 204; https://doi.org/10.3390/catal6120204 - 14 Dec 2016

Cited by 8 | Viewed by 7140

Abstract

Proton transport is an elementary process in the selective catalytic reduction of nitrogen oxides by ammonia (DeNO_x by NH₃-SCR) using metal-exchanged zeolites as catalysts. This review summarizes recent advancements in the study of proton transport in zeolite catalysts using in situ electrical impedance spectroscopy (IS) under NH₃-SCR reaction conditions. Different factors, such as the metal cation type, metal exchange level, zeolite framework type, or formation of intermediates, were found to influence the proton transport properties of zeolite NH₃-SCR catalysts. A combination of IS with diffuse reflection infrared Fourier transformation spectroscopy in situ (in situ IS-DRIFTS) allowed to achieve a molecular understanding of the proton transport processes. Several mechanistic aspects, such as the NH₃-zeolite interaction, NO-zeolite interaction in the presence of adsorbed NH₃, or formation of NH₄⁺ intermediates, have been revealed. These achievements indicate that IS-based in situ methods as complementary tools for conventional techniques (e.g., in situ X-ray absorption spectroscopy) are able to provide new perspectives for the understanding of NH₃-SCR on zeolite catalysts. Full article

(This article belongs to the Special Issue In Situ and Operando Characterization in Catalysis)

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