Impact of small promoter amounts on coke structure in dry reforming of methane over Ni/ ZrO2

Coke deposition is one of the main challenges in the commercialisation of dry reforming of methane over supported Ni catalysts. Besides the coke quantity, the structure of the deposits is also essential for the catalyst lifetime. Accordingly, in this study, we analysed the effect of Na, K, and Cs promoters on both these variables over Ni/ ZrO2 catalysts. Besides blocking the most active coke-forming sites already at low loading, the promoting effect of the alkali metals is also contributed by their coke gasification activity. To evaluate the additional impact of the latter, the behaviour of alkali-doped catalysts was compared to that for Mn-doped catalysts, exclusively featuring the site-blocking promotion mechanism. While the conversion is barely affected by the type of promoter, it has a profound effect on the amount and the composition of carbon deposits formed during the reaction. Promoting with K or Mn reduces the coke content to a similar degree but with less carbon fibres observed in the case of K. The promotion by Cs and Na results in the lowest coke content. The superior performance of Cs and Na-doped Ni/ZrO2 catalysts is attributed to the enhanced coke gasification via carbonate species on top of the site blocking effects.

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Impact of Small Promoter Amounts on Coke Structure in Dry Reforming over Ni/ ZrO2

10.26434/chemrxiv.12174879.v1 ◽

2020 ◽

Author(s):

Robert Franz ◽

Tobias Kuehlewind ◽

Genrikh Shterk ◽

Edy Abou-hamad ◽

Alexander Parastaev ◽

...

Keyword(s):

Alkali Metals ◽

Dry Reforming ◽

Coke Deposition ◽

Dry Reforming Of Methane ◽

Similar Degree ◽

Ni Catalysts ◽

Coke Content ◽

K Promotion ◽

Carbonate Species ◽

Supported Ni

Coke deposition is one of the main challenges in the commercialization of dry reforming of methane over supported Ni catalysts. Besides the coke quantity, the structure of the deposits is also essential for the catalyst lifetime. Accordingly, in this study, we analysed the effect of different metal promoters on both these variables over Ni/ ZrO2 catalysts. Alkali metals are known to block the most active coke forming sites already at low loading, leading to an investigation of Na, K and Cs. To analyse the possible contributions of coke gasification activity of the alkali metals, Mn was additionally used as a comparison. While the conversion is barely affected by the type of promoter, it has profound effect on the amount and the composition of carbon deposits formed during reaction: Addition of K or Mn reduces the coke content to a similar degree but with less carbon fibres observed in the case of K. Promotion by Cs and Na results in the lowest coke content, which is attributed to enhanced coke gasification via carbonate species

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A novel promoting effect of chelating ligand on the dispersion of Ni species over Ni/SBA-15 catalyst for dry reforming of methane

International Journal of Hydrogen Energy ◽

10.1016/j.ijhydene.2017.04.090 ◽

2017 ◽

Vol 42 (20) ◽

pp. 14103-14114 ◽

Cited By ~ 29

Author(s):

Qiulin Zhang ◽

Kaixian Long ◽

Jing Wang ◽

Tengfei Zhang ◽

Zhongxian Song ◽

...

Keyword(s):

Dry Reforming ◽

Dry Reforming Of Methane ◽

Promoting Effect ◽

Chelating Ligand ◽

Ni Species

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Factors affecting the long-term stability of mesoporous nickel-based catalysts in combined steam and dry reforming of methane

Catalysis Science & Technology ◽

10.1039/c6cy00032k ◽

2016 ◽

Vol 6 (12) ◽

pp. 4616-4631 ◽

Cited By ~ 36

Author(s):

K. Jabbour ◽

N. El Hassan ◽

A. Davidson ◽

S. Casale ◽

P. Massiani

Keyword(s):

Dry Reforming ◽

Coke Deposition ◽

Dry Reforming Of Methane ◽

One Pot ◽

Factors Affecting ◽

Term Stability ◽

Long Term Stability ◽

Highly Efficient ◽

One Pot Synthesis

Direct “one-pot” synthesis is highly efficient to obtain performing mesoporous Ni–Al2O3catalysts able to resist deactivation by sintering and coke deposition during CH4reforming by CO2and H2O to produce “metgas”.

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Mechanistic Insights for Dry Reforming of Methane on Cu/Ni Bimetallic Catalysts: DFT-Assisted Microkinetic Analysis for Coke Resistance

Catalysts ◽

10.3390/catal10091043 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1043

Author(s):

Ahmed Omran ◽

Sun Hee Yoon ◽

Murtaza Khan ◽

Minhaj Ghouri ◽

Anjaneyulu Chatla ◽

...

Keyword(s):

Energy Barrier ◽

Density Functional ◽

Carbon Deposition ◽

Bimetallic Catalyst ◽

Dry Reforming ◽

Coke Deposition ◽

Dry Reforming Of Methane ◽

Catalyst Stability ◽

Effect Of Temperature ◽

Elimination Mechanism

Density functional theory (DFT) calculations have been utilized to evaluate the complete reaction mechanism of methane dry reforming (DRM) over Ni2Cu (111) bimetallic catalyst. The detailed catalytic cycle on Ni2Cu (111) catalyst demonstrated superior coke resistance compared to pure Ni (111) and Ni2Fe (111) reported in the literature. Doping Cu in the Ni–Ni network enhanced the competitive CH oxidation by both atomic O and OH species with the latter having only 0.02 eV higher than the 1.06 eV energy barrier required for CH oxidation by atomic O. Among the C/CH oxidation pathways, C* + O* → CO (g) was the most favorable with an energy barrier of 0.72 eV. This was almost half of the energy barrier required for the rate-limiting step of CH decomposition (1.40 eV) and indicated enhanced coke deposition removal. Finally, we investigated the effect of temperature (800~1000 K) on the carbon deposition and elimination mechanism over Ni2Cu (111) catalyst. Under those realistic DRM conditions, the calculations showed a periodic cycle of simultaneous carbon deposition and elimination resulting in improved catalyst stability.

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Dry Reforming of Methane over a Ruthenium/Carbon Nanotube Catalyst

ChemEngineering ◽

10.3390/chemengineering4010016 ◽

2020 ◽

Vol 4 (1) ◽

pp. 16

Author(s):

Yuan Zhu ◽

Kun Chen ◽

Robert Barat ◽

Somenath Mitra

Keyword(s):

Carbon Nanotube ◽

Kinetic Model ◽

Packed Bed ◽

Dry Reforming ◽

Gas Analysis ◽

Packed Bed Reactor ◽

Coke Deposition ◽

Dry Reforming Of Methane ◽

Reverse Water Gas Shift ◽

Water Gas

In this study, CH4 dry reforming was demonstrated on a novel microwave-synthesized ruthenium (Ru)/carbon nanotube (CNT) catalyst. The catalyst was tested in an isothermal laboratory-packed bed reactor, with gas analysis by gas chromatography/thermal conductivity detection. The catalyst demonstrated excellent dry-reforming activity at modest temperatures (773–973 K) and pressure (3.03 × 105 Pa). Higher reaction temperatures favored increased conversion of CH4 and CO2, and increased H2/CO product ratios. Slight coke deposition, estimated by carbon balance, was observed at higher temperatures and higher feed CH4/CO2. A robust global kinetic model composed of three reversible reactions—dry reforming, reverse water gas shift, and CH4 decomposition—simulates observed outlet species concentrations and reactant conversions using this Ru/CNT catalyst over the temperature range of this study. This engineering kinetic model for the Ru/CNT catalyst predicts a somewhat higher selectivity and yield for H2, and less for CO, in comparison to previously published results for a similarly prepared Pt_Pd/CNT catalyst from our group.

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Methane Dry Reforming over Ni-Co/Al2O3: Kinetic Modelling in a Catalytic Fixed-bed Reactor

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2016-0170 ◽

2017 ◽

Vol 15 (6) ◽

Cited By ~ 5

Author(s):

Yacine Benguerba ◽

Mirella Virginie ◽

Christine Dumas ◽

Barbara Ernst

Keyword(s):

Catalyst Deactivation ◽

Kinetic Modelling ◽

Fixed Bed ◽

Dry Reforming ◽

Fixed Bed Reactor ◽

Coke Deposition ◽

Dry Reforming Of Methane ◽

Reactor Model ◽

Reverse Water Gas Shift ◽

Different Temperatures

Abstract The dry reforming of CH4 was investigated in a catalytic fixed-bed reactor to produce hydrogen at different temperatures over supported bimetallic Ni-Co catalyst. The reactor model for the dry reforming of methane used a set of kinetic models: The Zhang et al model for the dry reforming of methane (DRM); the Richardson-Paripatyadar model for the reverse water gas shift (RWGS); and the Snoeck et al kinetics for the coke-deposition and gasification reactions. The effect of temperatures on the performance of the reactor was studied. The amount of each species consumed or/and produced were calculated and compared with the experimental determined ones. It was showed that the set of kinetic model used in this work gave a good fit and accurately predict the experimental observed profiles from the fixed bed reactor. It was found that reaction-4 and reaction-5 could be neglected which could explain the fact that this catalyst coked rapidly comparatively with other catalyst. The use of large amount of Ni-Co will lead to carbon deposition and so to the catalyst deactivation.

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Dry reforming of methane over nickel supported on Nd–ceria: enhancement of the catalytic properties and coke resistance

RSC Advances ◽

10.1039/d0ra05761d ◽

2020 ◽

Vol 10 (55) ◽

pp. 33059-33070

Author(s):

Hugo A. Lara-García ◽

Daniel G. Araiza ◽

Melissa Méndez-Galván ◽

Samuel Tehuacanero-Cuapa ◽

Antonio Gómez-Cortés ◽

...

Keyword(s):

Catalytic Properties ◽

Dry Reforming ◽

Coke Deposition ◽

Dry Reforming Of Methane

The Nd-doped CeO2 support enhances the reactivity of the catalysts, selectivity toward hydrogen and stability by improving coke deposition resistance.

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Reaction-induced Ni-based interstitial carbon atoms for coke-free dry reforming of methane

10.21203/rs.3.rs-753881/v1 ◽

2021 ◽

Author(s):

Qianqian Wang ◽

Wu Wang ◽

Sha Li ◽

Min Cao ◽

Pengfei Wang ◽

...

Keyword(s):

Dry Reforming ◽

Coke Deposition ◽

Dry Reforming Of Methane ◽

Interior Structure ◽

Interstitial Position ◽

Octahedral Sites ◽

In Situ Experiments ◽

Excellent Activity ◽

Space Volume

Abstract Dry reforming of methane on Ni-based catalyst offers an environmentally and economically viable and pivotal route to produce synthesis gas. The accumulation and polymerization of carbon atoms on the surface of Ni eventually deactivate the catalyst because of coke deposition. Here, we establish a reaction-induced method to isolate carbon atoms into the interstitial position of nickel octahedral sites (O-sites) under reaction condition, which can avoid the C−C bond formation. Al2O3 encapsulated Ni3Zn provides expanded space volume of O-sites in nickel to accommodate carbon atoms, and the further transformation to Ni3ZnC0.7 with superstructure feature was achieved under CH4/CO2 reaction. Ni3ZnC0.7/Al2O3 exhibits excellent activity and stability below 600°C with variable CH4/CO2 ratio (1/4−2/1). These active carbon atoms can be replenished and cycled in Ni3ZnC0.7 interior structure rather than depositing as coke on the surface during the reaction as revealed by in situ experiments.

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Bimetallic Ni–Ru and Ni–Re Catalysts for Dry Reforming of Methane: Understanding the Synergies of the Selected Promoters

Frontiers in Chemistry ◽

10.3389/fchem.2021.694976 ◽

2021 ◽

Vol 9 ◽

Author(s):

Andrea Álvarez Moreno ◽

Tomás Ramirez-Reina ◽

Svetlana Ivanova ◽

Anne-Cécile Roger ◽

Miguel Ángel Centeno ◽

...

Keyword(s):

Catalytic Activity ◽

Noble Metal ◽

Dry Reforming ◽

Coke Deposition ◽

Dry Reforming Of Methane ◽

Hydrogen Chemisorption ◽

High Catalytic Activity ◽

Reaction Conditions ◽

Primary Strategy ◽

Selection Of

Designing an economically viable catalyst that maintains high catalytic activity and stability is the key to unlock dry reforming of methane (DRM) as a primary strategy for biogas valorization. Ni/Al2O3 catalysts have been widely used for this purpose; however, several modifications have been reported in the last years in order to prevent coke deposition and deactivation of the samples. Modification of the acidity of the support and the addition of noble metal promoters are between the most reported strategies. Nevertheless, in the task of designing an active and stable catalyst for DRM, the selection of an appropriate noble metal promoter is turning more challenging owing to the lack of homogeneity of the different studies. Therefore, this research aims to compare Ru (0.50 and 2.0%) and Re (0.50 and 2.0%) as noble metal promoters for a Ni/MgAl2O4 catalyst under the same synthesis and reaction conditions. Catalysts were characterized by XRF, BET, XRD, TPR, hydrogen chemisorption (H2-TPD), and dry reforming reaction tests. Results show that both promoters increase Ni reducibility and dispersion. However, Ru seems a better promoter for DRM since 0.50% of Ru increases the catalytic activity in 10% and leads to less coke deposition.

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