Editorial

2 pages, 159 KiB

Open AccessEditorial

Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis

by Yves Schuurman and Pascal Granger

Catalysts 2019, 9(6), 501; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9060501 - 31 May 2019

Viewed by 2085

Kinetics and reactor modeling for heterogeneous catalytic reactions are prominent tools for investigating, and understanding, the catalyst functionalities at nanoscale, and related rates of complex reaction networks [...] Full article

(This article belongs to the Special Issue Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis)

Research

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11 pages, 629 KiB

Open AccessArticle

CaRMeN: An Improved Computer-Aided Method for Developing Catalytic Reaction Mechanisms

by Hendrik Gossler, Lubow Maier, Sofia Angeli, Steffen Tischer and Olaf Deutschmann

Catalysts 2019, 9(3), 227; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9030227 - 01 Mar 2019

Cited by 20 | Viewed by 4516

Abstract

The software tool CaRMeN (Catalytic Reaction Mechanism Network) was exemplarily used to analyze several surface reaction mechanisms for the combustion of H₂, CO, and CH₄ over Rh. This tool provides a way to archive and combine experimental and modeling information [...] Read more.

The software tool CaRMeN (Catalytic Reaction Mechanism Network) was exemplarily used to analyze several surface reaction mechanisms for the combustion of H₂, CO, and CH₄ over Rh. This tool provides a way to archive and combine experimental and modeling information as well as computer simulations from a wide variety of sources. The tool facilitates rapid analysis of experiments, chemical models, and computer codes for reactor simulations, helping to support the development of chemical kinetic models and the analysis of experimental data. In a comparative study, experimental data from different reactor configurations (channel, annular, and stagnation flow reactors) were modeled and numerically simulated using four different catalytic reaction mechanisms from the literature. It is shown that the software greatly enhanced productivity. Full article

(This article belongs to the Special Issue Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis)

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13 pages, 2155 KiB

Open AccessFeature PaperArticle

Kinetic Study of the Selective Hydrogenation of Acetylene over Supported Palladium under Tail-End Conditions

by Caroline Urmès, Jean-Marc Schweitzer, Amandine Cabiac and Yves Schuurman

Catalysts 2019, 9(2), 180; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9020180 - 14 Feb 2019

Cited by 18 | Viewed by 5882

Abstract

The kinetics of the selective hydrogenation of acetylene in the presence of an excess of ethylene has been studied over a 0.05 wt. % Pd/α-Al₂O₃ catalyst. The experimental reaction conditions were chosen to operate under intrinsic kinetic conditions, free from [...] Read more.

The kinetics of the selective hydrogenation of acetylene in the presence of an excess of ethylene has been studied over a 0.05 wt. % Pd/α-Al₂O₃ catalyst. The experimental reaction conditions were chosen to operate under intrinsic kinetic conditions, free from heat and mass transfer limitations. The data could be described adequately by a Langmuir–Hinshelwood rate-equation based on a series of sequential hydrogen additions according to the Horiuti–Polanyi mechanism. The mechanism involves a single active site on which both the conversion of acetylene and ethylene take place. Full article

(This article belongs to the Special Issue Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis)

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18 pages, 5874 KiB

Open AccessArticle

Must the Best Laboratory Prepared Catalyst Also Be the Best in an Operational Application?

by Lucie Obalová, Anna Klegova, Lenka Matějová, Kateřina Pacultová and Dagmar Fridrichová

Catalysts 2019, 9(2), 160; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9020160 - 07 Feb 2019

Cited by 7 | Viewed by 3566

Abstract

Three cobalt mixed oxide deN₂O catalysts, with optimal content of alkali metals (K, Cs), were prepared on a large scale, shaped into tablets, and tested in a pilot plant reactor connected to the bypassed tail gas from the nitric production plant, [...] Read more.

Three cobalt mixed oxide deN₂O catalysts, with optimal content of alkali metals (K, Cs), were prepared on a large scale, shaped into tablets, and tested in a pilot plant reactor connected to the bypassed tail gas from the nitric production plant, downstream from the selective catalytic reduction of NO_x by ammonia (SCR NO_x/NH₃) catalyst. High efficiency in N₂O removal (N₂O conversion of 75–90% at 450 °C, VHSV = 11,000 m³ m_bed⁻³ h⁻¹) was achieved. However, a different activity order of the commercially prepared catalyst tablets compared to the laboratory prepared catalyst grains was observed. Catalytic experiments in the kinetic regime using laboratory and commercial prepared catalysts and characterization methods (XRD, TPR-H₂, physisorption, and chemical analysis) were utilized to explain this phenomenon. Experimentally determined internal effectiveness factors and their general dependency on kinetic constants were evaluated to discuss the relationship between the catalyst activity in the kinetic regime and the internal diffusion limitation in catalyst tablets as well as their morphology. The theoretical N₂O conversion as a function of the intrinsic kinetic constants and diffusion rate, expressed as effective diffusion coefficients, was evaluated to estimate the final catalyst performance on a large scale and to answer the question of the above article title. Full article

(This article belongs to the Special Issue Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis)

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19 pages, 3715 KiB

Open AccessArticle

Transient Kinetic Experiments within the High Conversion Domain: The Case of Ammonia Decomposition

by Yixiao Wang, M. Ross Kunz, Skyler Siebers, Harry Rollins, John Gleaves, Gregory Yablonsky and Rebecca Fushimi

Catalysts 2019, 9(1), 104; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9010104 - 19 Jan 2019

Cited by 14 | Viewed by 6951

Abstract

In the development of catalytic materials, a set of standard conditions is needed where the kinetic performance of many samples can be compared. This can be challenging when a sample set covers a broad range of activity. Precise kinetic characterization requires uniformity in [...] Read more.

In the development of catalytic materials, a set of standard conditions is needed where the kinetic performance of many samples can be compared. This can be challenging when a sample set covers a broad range of activity. Precise kinetic characterization requires uniformity in the gas and catalyst bed composition. This limits the range of convecting devices to low conversion (generally <20%). While steady-state kinetics offer a snapshot of conversion, yield and apparent rates of the slow reaction steps, transient techniques offer much greater detail of rate processes and hence more information as to why certain catalyst compositions offer better performance. In this work, transient experiments in two transport regimes are compared: an advecting differential plug flow reactor (PFR) and a pure-diffusion temporal analysis of products (TAP) reactor. The decomposition of ammonia was used as a model reaction to test three simple materials: polycrystalline iron, cobalt and a bimetallic preparation of the two. These materials presented a wide range of activity and it was not possible to capture transient information in the advecting device for all samples at the same conditions while ensuring uniformity. We push the boundary for the theoretical estimates of uniformity in the TAP device and find reliable kinetic measurement up to 90% conversion. However, what is more advantageous from this technique is the ability to observe the time-dependence of the reaction rate rather than just singular points of conversion and yield. For example, on the iron sample we observed reversible adsorption of ammonia and on cobalt materials we identify two routes for hydrogen production. From the time-dependence of reactants and product, the dynamic accumulation was calculated. This was used to understand the atomic distribution of H and N species regulated by the surface of different materials. When ammonia was pulsed at 550 °C, the surface hydrogen/nitrogen, (H/N), ratios that evolved for Fe, CoFe and Co were 2.4, 0.25 and 0.3 respectively. This indicates that iron will store a mixture of hydrogenated species while materials with cobalt will predominantly store NH and N. While much is already known about iron, cobalt and ammonia decomposition, the goal of this work was to demonstrate new tools for comparing materials over a wider window of conversion and with much greater kinetic detail. As such, this provides an approach for detailed kinetic discrimination of more complex industrial samples beyond conversion and yield. Full article

(This article belongs to the Special Issue Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis)

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18 pages, 52855 KiB

Open AccessFeature PaperArticle

Gaseous Nitric Acid Activated Graphite Felts as Hierarchical Metal-Free Catalyst for Selective Oxidation of H₂S

by Zhenxin Xu, Cuong Duong-Viet, Housseinou Ba, Bing Li, Tri Truong-Huu, Lam Nguyen-Dinh and Cuong Pham-Huu

Catalysts 2018, 8(4), 145; https://0-doi-org.brum.beds.ac.uk/10.3390/catal8040145 - 04 Apr 2018

Cited by 16 | Viewed by 6250

Abstract

In this study, we reported on the influence of gaseous HNO₃ treatment on the formation of defects decorated with oxygenated functional groups on commercial graphite felts (GFs). The gaseous acid treatment also leads to a remarkable increase of the specific as well [...] Read more.

In this study, we reported on the influence of gaseous HNO₃ treatment on the formation of defects decorated with oxygenated functional groups on commercial graphite felts (GFs). The gaseous acid treatment also leads to a remarkable increase of the specific as well as effective surface area through the formation of a highly porous graphite structure from dense graphite filamentous. The as-synthesized catalyst was further used as a metal-free catalyst in the selective oxidation of H₂S in industrial waste effluents. According to the results, the defects decorated with oxygenated groups were highly active for performing selective oxidation of H₂S into elemental sulfur. The desulfurization activity was relatively high and extremely stable as a function of time on stream which indicated the high efficiency of these oxidized un-doped GFs as metal-free catalysts for the selective oxidation process. The high catalytic performance was attributed to both the presence of structural defects on the filamentous carbon wall, which acting as a dissociative adsorption center for the oxygen, and the oxygenated functional groups, which could play the role of active sites for the selective oxidation process. Full article

(This article belongs to the Special Issue Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis)

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13 pages, 1432 KiB

Open AccessArticle

Modeling of a Pilot-Scale Fixed-Bed Reactor for Dehydration of 2,3-Butanediol to 1,3-Butadiene and Methyl Ethyl Ketone

by Daesung Song

Catalysts 2018, 8(2), 72; https://0-doi-org.brum.beds.ac.uk/10.3390/catal8020072 - 09 Feb 2018

Cited by 9 | Viewed by 5163

Abstract

A 1D heterogeneous reactor model accounting for interfacial and intra-particle gradients was developed to simulate the dehydration of 2,3-Butanediol (2,3-BDO) to 1,3-Butadiene (1,3-BD) and Methyl Ethyl Ketone (MEK) over an amorphous calcium phosphate (a-CP) catalyst in a pilot-scale fixed-bed reactor. The developed model [...] Read more.

A 1D heterogeneous reactor model accounting for interfacial and intra-particle gradients was developed to simulate the dehydration of 2,3-Butanediol (2,3-BDO) to 1,3-Butadiene (1,3-BD) and Methyl Ethyl Ketone (MEK) over an amorphous calcium phosphate (a-CP) catalyst in a pilot-scale fixed-bed reactor. The developed model was validated with experimental data in terms of a fluid temperature profile along with the length of the catalyst bed, 2,3-BDO conversion, and selectivity for the major products, 1,3-BD and MEK, at the outlet of the reactor. The fluid temperature profile obtained from the model along the length of the catalyst bed coincides satisfactorily with the experimental observations. The difference between the experimental data and the 1D heterogeneous reactor model prediction for 2,3-BDO conversion and selectivity of 1,3-BD and MEK were 0.1%, 9 wt %, and 2 wt %, respectively. In addition, valuable insights related to the feeding system of a commercial-scale plant were made through troubleshooting of the pilot tests. Notably, if the feed including only 2,3-BDO and furnaces that increase the temperature of the feed to the reaction temperature were used in a commercial plant, the feeding system could not be operational because of the presence of heavy chemicals considered oligomers of 2,3-BDO. Full article

(This article belongs to the Special Issue Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis)

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Review

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89 pages, 21455 KiB

Open AccessReview

Kinetic Modeling of Catalytic Olefin Cracking and Methanol-to-Olefins (MTO) over Zeolites: A Review

by Sebastian Standl and Olaf Hinrichsen

Catalysts 2018, 8(12), 626; https://0-doi-org.brum.beds.ac.uk/10.3390/catal8120626 - 05 Dec 2018

Cited by 33 | Viewed by 11459

Abstract

The increasing demand for lower olefins requires new production routes besides steam cracking and fluid catalytic cracking (FCC). Furthermore, less energy consumption, more flexibility in feed and a higher influence on the product distribution are necessary. In this context, catalytic olefin cracking and [...] Read more.

The increasing demand for lower olefins requires new production routes besides steam cracking and fluid catalytic cracking (FCC). Furthermore, less energy consumption, more flexibility in feed and a higher influence on the product distribution are necessary. In this context, catalytic olefin cracking and methanol-to-olefins (MTO) gain in importance. Here, the undesired higher olefins can be catalytically converted and, for methanol, the possibility of a green synthesis route exists. Kinetic modeling of these processes is a helpful tool in understanding the reactivity and finding optimum operating points; however, it is also challenging because reaction networks for hydrocarbon interconversion are rather complex. This review analyzes different deterministic kinetic models published in the literature since 2000. After a presentation of the underlying chemistry and thermodynamics, the models are compared in terms of catalysts, reaction setups and operating conditions. Furthermore, the modeling methodology is shown; both lumped and microkinetic approaches can be found. Despite ZSM-5 being the most widely used catalyst for these processes, other catalysts such as SAPO-34, SAPO-18 and ZSM-23 are also discussed here. Finally, some general as well as reaction-specific recommendations for future work on modeling of complex reaction networks are given. Full article

(This article belongs to the Special Issue Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis)

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20 pages, 1503 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Contribution to the Experimental Microkinetic Approach of Gas/Solid Heterogeneous Catalysis: Measurement of the Individual Heats of Adsorption of Coadsorbed Species by Using the AEIR Method

by Daniel Bianchi

Catalysts 2018, 8(7), 265; https://0-doi-org.brum.beds.ac.uk/10.3390/catal8070265 - 29 Jun 2018

Cited by 9 | Viewed by 3184

Abstract

The two first surface elementary steps of a gas/solid catalytic reaction are the adsorption/desorption at least one of the reactants leading to its adsorption equilibrium which can be or not disturbed by the others surface elementary steps leading to the products. The variety [...] Read more.

The two first surface elementary steps of a gas/solid catalytic reaction are the adsorption/desorption at least one of the reactants leading to its adsorption equilibrium which can be or not disturbed by the others surface elementary steps leading to the products. The variety of the sites of a conventional catalyst may lead to the formation of different coadsorbed species such as linear, bridged and threefold coordinated species for the adsorption of CO on supported metal particles. The aim of the present article is to summarize works performed in the last twenty years for the development and applications of an analytical method named Adsorption Equilibrium InfraRed spectroscopy (AEIR) for the measurement of the individual heats of adsorption of coadsorbed species and for the validation of mathematical expressions for their adsorption coefficients and adsorption models. The method uses the evolution of the IR bands characteristic of each of coadsorbed species during the increase in the adsorption temperature in isobaric conditions. The presentation shows that the versatility of AEIR leads to net advantages as compared to others conventional methods particularly in the context of the microkinetic approach of catalytic reactions. Full article

(This article belongs to the Special Issue Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis)

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