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

Omran, Ahmed; Yoon, Soo-Han; Khan, Murtaza Ali; Ghouri, Minhaj; Chatla, Anjaneyulu; Elbashir, Nimir O.

doi:10.3390/catal10091043

Cited by 37 publications

(26 citation statements)

References 54 publications

(73 reference statements)

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“…This reaction has an energy barrier of 0.68 eV and a reaction energy of −0.74 eV in Table 3. The C* oxidation is an exothermic reaction with a reaction energy of −1.90 eV, which is close to the reported value of −2.17 eV on the Cu/Ni catalysts in the literature 39 . The reverse reaction energy barrier is 3.36 eV, which indicates that the final product CO is stable and not conducive to be decomposed.…”

Section: Resultssupporting

confidence: 85%

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Comparative density functional theory study of carbon formation and removal mechanism on Rh modified Ni‐based catalyst in theCH₄/CO₂reforming

et al. 2021

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Summary Rh catalyst shows promising performance for coke resistance in the CH4/CO2 reforming reaction. In this study, a single atom Rh was added to the surface of Ni(111) by doping and adsorbing ways, and the performance of these surfaces was compared with the pure Ni(111) through density functional theory (DFT) calculation. The reactions related to the carbon formation were studied to obtain the favored adsorption site and dominant reaction paths on three surfaces. A good linear relationship between the charge difference and the reaction barrier was proposed. On the Ni(111) surface, the highest energy barrier of CH* oxidation and decomposition is 1.24 and 1.30 eV, respectively, thus these two reaction paths are dominant. The most favorable pathway for the Rh/Ni(111) is CH* + O* → CHO* → CO* + H*, with the highest energy barrier of 1.34 eV. However, C* is more likely to be converted into C‐C (C2) than oxidized on all three catalyst surfaces. As a result, Rh/Ni(111) surface shows better catalytic activity thermodynamically and more superior carbon deposition resistance. In general, compared with pure Ni catalyst, the modification of Rh could manipulate the reaction path of CH* consumption, which could inhibit the direct decomposition of CH*, and finally suppress the carbon deposition.

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Section: Resultssupporting

confidence: 85%

“…The addition of an appropriate amount of Cu increases the energy barrier for CH* cracking and makes C* more easily oxidized. And the result was confirmed by experiments 38,39 . However, the accumulation of carbon is rarely considered and the detailed mechanism of Rh‐doped Ni‐based catalyst is lacking.…”

Section: Introductionmentioning

confidence: 74%

Comparative density functional theory study of carbon formation and removal mechanism on Rh modified Ni‐based catalyst in theCH₄/CO₂reforming

et al. 2021

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“…The DRM reaction mechanism on the surface of Ru, Rh, Pt, Pd, and other precious metals has been confirmed by theoretical calculations. In addition, the effect of doping Cu, Fe, B, and other elements , into Ni-based catalysts on the catalytic activity and reaction mechanism has also been verified by theoretical calculations.…”

Section: Introductionmentioning

confidence: 83%

Nickel/Molybdenum Bimetallic Alloy for Dry Reforming of Methane: A Coverage-Dependence Microkinetic Model Simulation Based on the First-Principles Calculation

Wang

2021

J. Phys. Chem. C

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Ni-based catalysts have attracted much attention because of their high catalytic activity for dry reforming of methane (DRM) reaction and their low-cost characteristics. The deactivation caused by carbon deposition has become a major factor restricting its application. Mo doping is expected to improve the carbon deposition resistance of Ni-based catalysts. In this study, we used density functional theory (DFT) calculations and the microkinetic model to compare the catalytic activity of Ni and MoNi4 (as a Mo-doped Ni-based catalyst model) for the DRM reaction. By calculating the surface energies, Ni(111) and MoNi4(001) were determined as the calculation models. The DFT calculation results show that MoNi4 catalyst has a stronger adsorption capacity for intermediate species. Combining Bader charge analysis and charge density differences analysis, the stronger adsorption capacity comes from the stronger electron donating capacity brought about by the doping of Mo. According to our proposed reaction network, the energy barriers of 19 elementary reactions were calculated in detail. We found that there are similar CO2 dissociation modes (direct dissociation) and C–O bond formation modes (CH2/CH–O oxidation) on Ni(111) and MoNi4(001). Both CH4 dissociation and CO2 dissociation on MoNi4(001) have a lower energy barrier, while CO formation through CH2/CH–O oxidation has a higher energy barrier. The total free energy barrier of the DRM is lower than that of carbon deposition formation on MoNi4(001), whereas the opposite on Ni(111), means MoNi4(001) shows strongly carbon resistance properties. At 1073.15 K and 2 bar, the microkinetic simulation results showed that when the reaction reaches equilibrium, MoNi4(001) is deactivated due to excessive O*. Accordingly, the influence of O* coverage on the activation energy of CO 2 dissociation was considered in the MoNi 4 microkinetic model. In this way, the DRM reaction can be carried out steadily and continuously on MoNi4(001). And the simulation results show that MoNi4 catalyst has extremely high catalytic activity and selectivity and is basically not affected by carbon deposition and byproduct H2O. Under the same simulated conditions, MoNi4(001) showed better catalytic activity than Ni(111). In addition, degree of rate control (DRC) analysis showed that on MoNi4(001), the activation of CH4 is the rate-limiting step of the whole reaction. Through our study, one might be proposed that alloying Ni with a small amount of active metals such as Mo can increase the carbon deposition resistance by increasing the activation of CH4 and CO2 in an equal ratio.

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“…One of the most promising ways to transform CO 2 is through the use of the dry methane reforming (DMR) reaction. During this reaction, CO 2 and CH 4 are combined to produce syngas, which is a valuable precursor for many other downstream applications [4]. Although methane is present at a lower concentration than CO 2 , its global warming potential is 21 times greater [5].…”

Section: Introductionmentioning

confidence: 99%

Nanowire-Based Materials as Coke-Resistant Catalyst Supports for Dry Methane Reforming

et al. 2021

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In this paper, nanowire-supported catalysts loaded with nickel are shown to be coke resistant compared to nanoparticle-supported catalysts. Specifically, Ni-loaded titania-based nanowire catalysts were tested with the dry methane reforming process in a laboratory-scale continuous packed-bed atmospheric reactor. The CO2 conversion rate stayed above 90% for over 30 h on stream under coke-promoting conditions, such as high flow rates, low temperatures, and a high ratio of CH4 to CO2. The coke (CxHy, x>>y) on the spent catalyst surface for both nanowire- and nanoparticle-supported catalysts was characterized by TGA, temperature-programmed reduction (TPR), and electron microscopy (SEM/TEM/EDS), and it was revealed that the types of carbon species present and their distribution over the morphology-enhanced materials played a major role in the deactivation. The CO2 conversion activity of Ni supported on titania nanoparticles was reduced from ~80% to less than 72% in 30 h due to the formation of a graphitic coke formation. On the other hand, Ni particles supported on nanowires exhibited cube-octahedral morphologies, with a high density of non- (111) surface sites responsible for the increased activity and reduced graphitic coke deposition, giving a sustained and stable catalytic activity during a long time-on-stream experiment.

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

Cited by 37 publications

References 54 publications

Comparative density functional theory study of carbon formation and removal mechanism on Rh modified Ni‐based catalyst in theCH₄/CO₂reforming

Comparative density functional theory study of carbon formation and removal mechanism on Rh modified Ni‐based catalyst in theCH₄/CO₂reforming

Nickel/Molybdenum Bimetallic Alloy for Dry Reforming of Methane: A Coverage-Dependence Microkinetic Model Simulation Based on the First-Principles Calculation

Nanowire-Based Materials as Coke-Resistant Catalyst Supports for Dry Methane Reforming

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

Cited by 37 publications

References 54 publications

Comparative density functional theory study of carbon formation and removal mechanism on Rh modified Ni‐based catalyst in theCH4/CO2reforming

Comparative density functional theory study of carbon formation and removal mechanism on Rh modified Ni‐based catalyst in theCH4/CO2reforming

Nickel/Molybdenum Bimetallic Alloy for Dry Reforming of Methane: A Coverage-Dependence Microkinetic Model Simulation Based on the First-Principles Calculation

Nanowire-Based Materials as Coke-Resistant Catalyst Supports for Dry Methane Reforming

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Comparative density functional theory study of carbon formation and removal mechanism on Rh modified Ni‐based catalyst in theCH₄/CO₂reforming

Comparative density functional theory study of carbon formation and removal mechanism on Rh modified Ni‐based catalyst in theCH₄/CO₂reforming