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Ni/La2O3 Catalysts for Dry Reforming of Methane: Insights into the Factors Improving the Catalytic Performance

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Luoji Xu
Luoji Xu
Luoji Xu
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Wen Ming Liu at Nanchang University
Wen Ming Liu
Xin Zhang
Xin Zhang
Xin Zhang
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Lele Tao
Lele Tao
Lele Tao
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Abstract and Figures

To understand the structure‐reactivity relationship of Ni/La2O3, and eventually get more applicable catalysts for DRM, glycine nitrate combustion (GNC), precipitation (PP) and thermal decomposition (TD) methods have been used to prepare La2O3 supports. Although all the supports possess a hexagonal La2O3 phase, their bulk and surface properties are significantly changed. By using them as supports, the interactions between NiO/Ni and La2O3 are varied, thus achieving Ni/La2O3 catalysts with different activity, stability and anti‐coking ability, which follow the order of 5Ni/La2O3‐GNC>5Ni/La2O3‐PP>5Ni/La2O3‐TD. On La2O3 having a higher surface area, a catalyst with a higher active metallic Ni surface area can be achieved. Therefore, the interfaces between Ni and La2O2CO3 can be enlarged, which effectively facilitates the reaction between carbon deposits and the La2O2CO3 formed during the DRM, thus preventing the accumulation of both and keeping the catalyst surface clean, active and stable. In addition, the amount of surface alkaline and active oxygen sites of the reduced catalysts obey the order of 5Ni/La2O3‐GNC>5Ni/La2O3‐PP>5Ni/La2O3‐TD, which is well consistent with the reaction performance. Therefore, these two factors are also believed to be critical to decide the reaction performance. It is concluded that Ni/La2O3 catalysts with high activity, stability and potent anti‐coking ability for DRM can be achieved by preparing catalysts with high Ni dispersion.
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Ni/La2O3Catalysts for Dry Reforming of Methane: Insights
into the Factors Improving the Catalytic Performance
Luoji Xu+,[a] Wenming Liu+,[a] Xin Zhang,[a] Lele Tao,[a] Lianghui Xia,[a] Xianglan Xu,[a]
Junwei Song,[c] Wufeng Zhou,[d] Xiuzhong Fang,*[a, b] and Xiang Wang*[a]
To understand the structure-reactivity relationship of Ni/La2O3,
and eventually get more applicable catalysts for DRM, glycine
nitrate combustion (GNC), precipitation (PP) and thermal
decomposition (TD) methods have been used to prepare La2O3
supports. Although all the supports possess a hexagonal La2O3
phase, their bulk and surface properties are significantly
changed. By using them as supports, the interactions between
NiO/Ni and La2O3are varied, thus achieving Ni/La2O3catalysts
with different activity, stability and anti-coking ability, which
follow the order of 5Ni/La2O3-GNC >5Ni/La2O3-PP >5Ni/La2O3-
TD. On La2O3having a higher surface area, a catalyst with a
higher active metallic Ni surface area can be achieved. There-
fore, the interfaces between Ni and La2O2CO3can be enlarged,
which effectively facilitates the reaction between carbon
deposits and the La2O2CO3formed during the DRM, thus
preventing the accumulation of both and keeping the catalyst
surface clean, active and stable. In addition, the amount of
surface alkaline and active oxygen sites of the reduced catalysts
obey the order of 5Ni/La2O3-GNC >5Ni/La2O3-PP >5Ni/La2O3-TD,
which is well consistent with the reaction performance. There-
fore, these two factors are also believed to be critical to decide
the reaction performance. It is concluded that Ni/La2O3catalysts
with high activity, stability and potent anti-coking ability for
DRM can be achieved by preparing catalysts with high Ni
dispersion.
Introduction
With the high pace development of modern industry, the
demand for energy is increasing and people are looking for
new green energy source instead of fossil fuels. As a type of
clean and high efficient energy carrier, hydrogen has attracted
much attention. Methane reforming, such as steam reforming,[1]
dry reforming[2] and oxidative steam reforming,[3] is attractive
for larger scale hydrogen production, among which steam
reforming has been successfully industrialized. Over recent
years, dry reforming of methane (DRM) has aroused much
interest since it can convert two strong greenhouse gases into
syngas. Moreover, the H2/CO molar ratio around 1 is promising
for further transformation of the obtained syngas into higher
value chemicals such as liquid fuels by Fischer-Tropsch
process.[4,5] As depicted in Equation (1), DRM is a strong
endothermic reaction, thus high temperature is generally
required to proceed.
CO2þCH4!2CO þ2H2DH298 K ¼ þ247 kJ mol1(1)
Up to date, both noble metals[6] and non-noble metals have
been adopted as the active components for DRM catalysts.[7]
Noble metals such as Pt,[8] Pd,[9] Rh,[10] or Ru[11] exhibit superior
catalytic activity and carbon resistance, but their high cost limits
the widespread industrial applications. Over recent decades, Ni-
based catalysts have been widely used in DRM for syngas and
hydrogen production because of its’ high initial activity and
competitive price. However, severe carbon deposition and Ni
active sites agglomeration at elevated temperature can result in
quick deactivation of the catalysts during DRM processes.[12,13]
On the basis of former studies, in high temperature region (>
550 °C), coke deposition mainly originates from CH4decom-
position [Eq. (2)]:
CH4!Cþ2H2DH298 K ¼ þ75 kJ mol1(2)
Whereas, in low-temperature region, coke deposition mainly
comes from Boudouard reaction [Eq. (3)]:
2CO !CþCO2DH298 K ¼ 172 kJ mol1(3)
To improve both the activity and coke resistance of Ni-based
catalysts, many efforts have been devoted to choosing good
[a] L. Xu,+Prof. Dr. W. Liu,+X. Zhang, L. Tao, L. Xia, X. Xu, Dr. X. Fang,
Prof. Dr. X. Wang
Key Laboratory of Jiangxi Province for Environment and Energy Catalysis
College of Chemistry
Nanchang University
Nanchang, Jiangxi 330031 (P.R. China)
E-mail: fangxiuzhong@ncu.edu.cn
xwang23@ncu.edu.cn
Homepage: http://chem.ncu.edu.cn/index.php?c =channel&molds =
szdw&id =39
[b] Dr. X. Fang
College of Environmental and Energy Engineering
Beijing University of Technology
Beijing 100124 (P.R. China)
[c] Dr. J. Song
School of Civil Engineering
Jiangxi University of Technology
Nanchang 330098 (P.R. China)
[d] W. Zhou
Jiangxi Golden Century Advance materials Co.Ltd
Nanchang, 330013 (P.R. China)
[+]These authors contributed equally to this work.
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/cctc.201900331
Full Papers
DOI: 10.1002/cctc.201900331
2887ChemCatChem 2019,11, 2887 – 2899 © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Wiley VCH Donnerstag, 06.06.2019
1912 / 137336 [S. 2887/2899] 1
... In face of such an issue, studies aiming at catalyst modi cation through the addition of lanthanum (La), cerium (Ce), and zirconium (Zr) oxides have been investigated to minimize the catalytic deactivation by coke deposition [8][9][10]. La increases the active phase dispersion, besides providing oxygen to react with the formed coke, thus improving the catalyst activity and stability [11]. Moreover, cerium also enhances the active phase dispersion and decreases the catalyst deactivation by coke [9]. ...
... Finally, it is noted that La-Al support did not present any reduction peak, thus indicating no presence of any reducible species. Therefore, the absence of reducible La 2 O 3 species below 900°C can be justi ed by the strong bond between La and O 2 [11]. ...
... Therefore, the bene cial effect of the La 2 O 3 impregnation on the catalyst is evident since it provides O 2 that assists the oxidation of the coke formed during the reaction [11,33]. ...
Use of structured systems as a strategy to minimize the deactivation of Ni-based catalysts applied in dry reforming of methane
Preprint
Full-text available
  • Jul 2023
The main challenge in the use of Ni based catalysts is the high deactivation rate of these catalysts. In this work, strategies aimed at improving this characteristic such as the use of structured catalysts were studied. In this work, the Ni/γ-Al 2 O 3 (Ni/Al) and Ni/La 2 O 3 -γ-Al 2 O 3 (Ni/La-Al) catalysts were synthesized by the all-in-one method and used in the Dry Reforming of Methane combined with its application in structured systems to minimize the effects of deactivation. The catalysts were characterized and a smaller Ni crystallite size for the La-promoted catalyst was observed. The deactivation of the structured catalysts and application of residual activity deactivation models (DMRA) were evaluated by applying different weight hourly velocities (WHSV). Besides that, the regeneration of the catalysts was developed through the comparison of the treatment with CO 2 and H 2 atmospheres. Furthermore, the greatest and the lowest deactivation of the structured systems were identified for the WHSV values of 40 and 20 L g cat ⁻¹ h − 1 , respectively. Finally, the regeneration treatment with CO 2 showed to be more efficient than the treatment with H 2 . A deactivation model was predicted in the region of equilibrium in the catalytic activity, which is associated with the appearance of a residual activity, which decreases with increasing WHSV variable.
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... Furthermore, La enhances the adsorption of CO 2 , regenerates the Ni surface, reduces coking, and improves stability under reforming reaction conditions. During the reforming reaction, CH 4 is primarily decomposed on the Ni crystal to form H 2 and surface carbon, whereas CO 2 is adsorbed onto the La 2 O 3 support to form La 2 O 2 CO 3 [77]. At high temperatures, the reaction of La 2 O 2 CO 3 with the carbonaceous material formed on the surfaces of the Ni crystals results in the production of CO and the restoration of the original state of the Ni surfaces [78]. ...
Performance of Ni-Based Catalysts with La Promoter for the Reforming of Methane in Gasification Process
Article
Full-text available
  • May 2024
The deactivation of active sites caused by high-temperature sintering and the deposition of a large amount of carbon are the main difficulties in the reforming of methane using Ni-based catalysts. La, as a promoter, has an ameliorating effect on the defects of Ni-based catalysts. In this article, the mechanism of action of Ni-based catalysts with the introduction of the rare-earth metal additive La was reviewed, and the effects of La on the methane-reforming performance of Ni-based catalysts were examined. The physical properties, alkalinity, and activity of Ni-based catalysts can be enhanced by the use of the auxiliary agent La, which promotes the conversion of CH4 and CO2 as well as the selectivity towards H2 and CO formation in the reforming of methane. The reason why the Ni-based catalysts could maintain long-term stability in the presence of La was discussed. Furthermore, the current state of research on the introduction of different amounts of La in the reforming of methane at home and abroad was analyzed. It was found that 2–5 wt.% La is the most optimal quantity for improving the catalyst activity and stability, as well as the CO2 chemisorption. The limitations and directions for future research in the reforming of methane were discussed.
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Mitigating deactivation in dry methane reforming by lanthanum catalysts for enhanced hydrogen production: A review
Article
  • Jun 2024
  • INT J HYDROGEN ENERG
Catalyst deactivation in dry methane reforming, resulting from coke accumulation and sintering, has long captivated academic interest due to its negative impact on catalytic performance and hindrance to industrial scalability. Thus, developing efficient catalysts capable of sustaining high reforming activity and stability is crucial. Lately, lanthanum (La) has gained popularity in catalysis for its ability to enhance performance and resist coking, owing to its great basicity, redox capabilities, and high oxygen storage capacity. As a result, diverse strategies for incorporating La into catalysts, including support, promoter, bimetallic combinations, and perovskite formation, have been extensively explored. Herein, this review delves into various advancements in lanthanum-based catalysts and their effectiveness in dry methane reforming while addressing catalyst deactivation and regeneration. Finally, the prospect of La-based catalysts in dry methane reforming is also emphasized in this review.
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Anti-coking Ni-La2O3/SiO2 catalyst prepared by a glycine-assisted impregnation method for low-temperature dry reforming of methane
Article
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The development of efficient Ni-based catalysts for low-temperature (≤600 °C) dry reforming of methane remains a challenge because of their susceptibility to carbon deposition. Herein, we report a Ni-La2O3/SiO2 catalyst prepared using a glycine-assisted impregnation method. Small Ni nanoparticles were confined by La2O3 on the SiO2 support in the catalyst, which exhibited remarkable resistance to carbon deposition for the dry reforming of methane at 600 °C.
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Use of structured systems as a strategy to minimize the deactivation of Ni-based catalysts applied in dry reforming of methane
Article
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In this work, the Ni/γ-Al2O3 (Ni/Al) and Ni/La2O3-γ-Al2O3 (Ni/La-Al) catalysts were synthesized using the all-in-one method and applied to dry methane reforming, with the aim of minimizing the effects of deactivation through the use of La and the application of monoliths. The characterization showed a smaller Ni crystallite size for the catalyst promoted by La, which was associated with better dispersion of its active phase. The monoliths showed a conversion rate around 15% higher than that of the powdered catalysts. By studying the deactivation of the monoliths and applying residual activity deactivation models (DMRA), it was possible to verify a fit with R2 greater than 0.90 and RMSE values below 5%, with the model predicted and adjusted to the residual activity region. In addition, the highest and lowest deactivation of the structured systems was identified for WHSV values of 40 and 20 L h−1 g−1cat, respectively. Finally, the regeneration of the catalysts with CO2 proved to be superior to that with H2, with a regeneration rate of 90% in the first two cycles.
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The Photocatalytic Oxidative Dehydrogenation of Ethane using CO2 as a Soft Oxidant over Pd/TiO2 Catalysts to C2H4 and Syngas
Article
Full-text available
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Using CO2 as the soft oxidant for the oxidative dehydrogenation of ethane (ODE) is a potential advancement for ethylene production from ethane. However, the current ODE reaction is primarily operated at high temperatures (e.g., 873K), and the development of an alternative approaches for the ODE reaction under the mild conditions is still a challenge. Herein, we report a photocatalytic ODE using CO2 as the oxidant over Pd/TiO2 catalysts at room temperature. The presence of CO2 significantly promoted the production of C2H4 and syngas, and the 1% Pd/TiO2 catalyst exhibited a C2H4 production rate of 230.5 μmol/gcat·h and syngas of 282.6 μmol/gcat·h. Density functional theory (DFT) calculation verified that the intermediate energy level provided by Pd and the covalent bond in Pd-O stimulated the electron transfer, excitation and separation. The photoinduced electron, hole and isolate OH on the surface of TiO2 played essential roles during the whole process. In addition, the possible reaction pathways of photocatalytic ODE with CO2 were proposed on the basis of the experimental data and DFT calculation results.
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Structural Effect of Ni/ZrO2 Catalyst on CO2 Methanation with Enhanced Activity
Article
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A zirconia supported nickel catalyst for CO2 methanation has been prepared via a rapid and effective plasma decomposition of nickel precursor at atmospheric pressure and temperature around 150 °C, followed by hydrogen reduction at 500 °C. The obtained Ni/ZrO2 catalyst shows high Ni dispersion with principally exposed Ni(111) lattice plane. An enhanced cooperation between Ni and interfacial active sites is achieved as well, which leads to rapid dissociative adsorption of H2 and hydrogen spillover. Sufficient H atoms are thereby generated for CO2 hydrogenation and helpful to create oxygen vacancies on the ZrO2 surface. Higher basicity correlated to the oxygen vacancies further enhances CO2 adsorption and activation. Hence, a superior low temperature activity for CO2 methanation was achieved. For example, a CO2 conversion of 71.9% with a CH4 yield of 69.5% was achieved over the plasma decomposed catalyst at 300 °C with a feeding gas consisting of H2 (32 ml min⁻¹), CO2 (8 ml min⁻¹) and N2 (10 ml min⁻¹) at a GHSV of 60,000 h⁻¹. The corresponding TOF value towards CO2 conversion is 0.61 s⁻¹. However, the CO2 conversion, CH4 yield and TOF value are only 32.9%, 30.3% and 0.39 s⁻¹ at the same reaction conditions over the thermally prepared catalyst. The operando DRIFT analyses demonstrate that CO2 methanation over the plasma decomposed catalyst follows the CO-hydrogenation route. The exposed high-coordinate Ni(111) facets of the plasma decomposed catalyst facilitate the decomposition of CO2 and formates into adsorbed CO. The subsequent hydrogenation of adsorbed CO leads to the production of methane. However, the thermally decomposed catalyst with complex Ni crystal structure and more defects mainly takes the pathway of direct formate hydrogenation. The present study confirms the structure of Ni/ZrO2 has significant effect on the catalytic activity for CO2 methanation.
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Methane dry reforming over Ni/Mg-Al-O: On the significant promotional effects of rare earth Ce and Nd metal oxides
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In this study, with the purpose to obtain more efficient catalysts for methane dry reforming, an Mg-Al-O support having excess MgO and higher alkalinity than pure MgAl2O4 spinel support have been designed and used to prepare Ni/Mg-Al-O catalysts. XRD has demonstrated that this support consists of both MgO and MgAl2O4 spinel phases. As a result, Ni/Mg-Al-O displays better reaction performance than Ni/MgAl2O4 and Ni/Al2O3 catalysts. With the promotion by Ce and Nd oxides, the Ni dispersion and the surface active oxygen amount can be significantly improved, which results in more active and stable catalysts with also significantly improved coking resistance. It is revealed that the active metallic Ni surface area, surface alkalinity and active oxygen abundance are the major factors deciding the reaction performance of the Ni/Mg-Al-O catalysts. Because of the optimal concerted action of these factors, Ni-Ce/Mg-Al-O, the sample promoted by ceria, displays the best reaction performance among all the catalysts.
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Behaviour of Rh supported on hydroxyapatite catalysts in partial oxidation and steam reforming of methane: On the role of the speciation of the Rh particles
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Rh/hydroxyapatite samples were prepared by impregnation and investigated for the partial oxidation (POM) and steam reforming (SRM) of methane. The catalysts were analysed by BET, XRD, DRS, XPS, H2-TPR, TEM, H2 chemisorption, CO2-TPD and NH3-TPD techniques. The characterisation results showed that, after calcination, Rh existed in three different forms in the samples: (i) large crystallites of Rh2O3 deposited on the surface of the catalysts, (ii) RhOx in small particles exhibiting strong interaction with the support and (iii) a phase of Rh2+ species which incorporated the hydroxyapatite framework. Operating in the POM and SRM processes the reduced Rh(x)/HAP catalysts resulted highly active and exhibited excellent stability at 973 K (for 30 h). This behaviour was explained by their high coke-resistance. The activity of the catalyst with the optimum loading (1%), in SRM, was compared with that of a commercial Rh/Al2O3 catalyst. The conversion and H2 and CO yields values achieved on the former were all close to those exhibited by the latter. This comparable behaviour was explained by suitable properties provided by the HAP support such as reducibility, lower surface acidity and larger pore sizes (ensuring a better diffusion of the reactants and the products during the SRM reaction). These properties seemed to compensate the low dispersion of the Rh active phase induced by its low specific surface area.
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Catalyst preparation with plasmas is increasingly attracting interest. A plasma is a partially ionized gas, consisting of electrons, ions, molecules, radicals, photons and excited species, which are all active species for catalyst preparation and treatment. Under the influence of plasma, the nucleation and crystal growth in catalyst preparation can be very different from the conventional thermal approach. Some thermodynamically unfavorable reactions can easily take place with plasmas. The compounds such as sulfides, nitrides and phosphides that are produced at harsh conditions can be synthesized by plasma at mild conditions. Plasmas can produce catalysts with smaller particle sizes and controllable structure. Plasma is also a facile tool for reduction, oxidation, doping, etching, coating, alloy formation, surface treatment and surface cleaning in a simple and direct way. A rapid and convenient plasma template removal has thus been established for the zeolite synthesis. It can operate at room temperature and allows the catalyst preparation on temperature sensitive supporting materials. Plasma is typically effective for the production of various catalysts on metallic substrates. In addition, plasma prepared transition metal catalysts show enhanced low temperature activity with improved stability. This provides a useful model catalyst for further improvement of the industrial catalysts. In this review, we aim to summarize the recent advances in catalyst preparation with plasmas. The present understanding of plasma-based catalyst preparation is discussed. The challenges and future development are addressed.
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Developing Reactive Catalysts for Low Temperature Oxidative Coupling of Methane: On the Factors Deciding the Reaction Performance of Ln 2 Ce 2 O 7 with Different Rare Earth A sites
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To develop more efficient catalysts that can be operated at low temperature region for oxidative of methane (OCM), a series of Ln2Ce2O7 compounds with different A sites (Ln = La, Pr, Sm and Y) have been prepared. It is revealed by XRD and Raman techniques that a defective cubic fluorite phase has been formed in all the catalysts. As a consequence, all the Ln2Ce2O7 catalysts possess much stronger surface basicity and more abundant electrophilic oxygen species in comparison with individual CeO2, which is beneficial to OCM reaction. It is believed that the concerted interaction between surface intermediate basic sites and selective electrophilic oxygen species is the predominant reason controlling the reaction performance of the catalysts. Furthermore, Ln2Ce2O7 catalysts own more abundant mesopores and higher surface areas than pure CeO2, which could also be favorable for the contacting of the reactants with the active sites. Due to the optimal synergistic interaction of these factors, La2Ce2O7 exhibits the best performance among all the catalysts, on which the highest C2 yield of 16.6% is achieved at 750 °C. In comparison with Mn/Na2WO4/SiO2, the most promising catalyst at present, La2Ce2O7 display much improved reaction performance at low temperature region (<750 °C).
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Synthesis of Highly Active and Stable Ni@Al2O3 Embedded Catalyst for Methane Dry Reforming: On the Confinement Effects of Al2O3 Shells for Ni Nanoparticles
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In this paper, a 12% Ni@Al2O3 catalyst has been synthesized by using inverse micro-emulsion technique and evaluated for the dry reforming of methane (DRM). It is revealed by TEM that the core-shell structure has been successfully formed in the 12% Ni@Al2O3 catalyst, for which the Ni nanoparticle cores with an average grain size around 10 nm are encapsulated by the mesoporous Al2O3 shells. In comparison with 12% Ni/Al2O3 catalyst prepared by impregnation method, much smaller Ni grain sizes and higher metallic Ni active surface areas can be achieved in the core-shell catalyst, as evidenced by TEM and H2 adsorption-desorption results. In addition, a larger amount of active oxygen species has been formed on the surface of 12% Ni@Al2O3. Most importantly, the formation of core-shell structure in 12% Ni@Al2O3 can effectively impede the migration of the Ni active species at elevated temperature, thus preventing it from agglomerating. As a consequence, 12% Ni@Al2O3 core-shell catalyst shows remarkable activity, stability and potent coke resistance during a 50 hours' durability evaluation at 800 oC for DRM. It is believed that the core-shell structure is the major factor accounting for the superior DRM performance over the 12% Ni@Al2O3 catalyst, which might open a new gate for people to design and develop improved catalyst for DRM for hydrogen production.
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Ni/Ln2Zr2O7 (Ln = La, Pr, Sm and Y) catalysts for methane steam reforming: The effects of A site replacement
Article
  • Jan 2017
A series of Ln2Zr2O7 supports (Ln=La, Pr, Sm and Y) with different “A” sites were prepared by glycine-nitrate combustion method and used to support Ni to prepare catalysts for methane steam reforming for hydrogen production. It is revealed by XRD and Raman techniques that with the decreasing of the rA/rB ratio in the sequence of La, Pr, Sm and Y, the structures of the compounds become less order with the transformation of the bulk phase from ordered pyrochlore (La2Zr2O7) to less ordered pyrochlore (Pr2Zr2O7 and Sm2Zr2O7) and subsequently to defective fluorite (Y2Zr2O7). XPS demonstrated that the oxygen vacancies and mobility of the compounds improves also with the sequence. As supports for Ni, those possessing more mobile oxygen species display evidently enhanced coke resistance. In addition, as evidenced by H2-TPR, the supported Ni active sites have stronger interaction with those supports having higher degree of disorder, which improves both of the Ni dispersion and thermal stability of the prepared Ni/Ln2Zr2O7. Y2Zr2O7 support with a defective fluorite structure owns the most amount of mobile oxygen species. Therefore, Ni active species has stronger interaction with it than with other three supports, which results in the smallest Ni grains with the highest metallic active surface area. As a consequence, Ni/Y2Zr2O7 exhibits the highest activity, stability and coke resistance among all of the catalysts.It is concluded that A site replacement by rare earth cations with different radius influences the structures of Ln2Zr2O7 significantly, which ultimately affects the reaction performance of the prepared Ni/Ln2Zr2O7 catalysts for methane steam reforming.
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Dry reforming of methane over Ni/La2O3 nanorod catalysts with stabilized Ni nanoparticles
Article
  • Mar 2017
  • APPL CATAL B-ENVIRON
This paper describes the design of a Ni/La2O3 catalyst using La2O2CO3 nanorod as a support precursor (denoted as Ni/La2O3-LOC) via a wet impregnation method for dry reforming of methane (DRM). The results showed that La2O3 derived from the La2O2CO3 precursor maintained its initial morphology upon thermal treatment and could highly disperse Ni particles on it. Additionally, the nanorod-shaped support could provide more medium-strength basic sites to facilitate CO2 adsorption and activation on its surface. Consequently, the Ni/La2O3-LOC catalyst reached 70% of CH4 conversion and 75% of CO2 conversion at 700 °C after 50 h DRM reaction with a H2/CO ratio of 0.87. The enhanced metal-support interaction restricted the sintering of nickel particles under harsh reaction conditions. Coke evolution on the catalysts was also investigated to understand coke formation mechanism and the role of La2O2CO3 in coke elimination. It has been found that nickel dispersion can affect distribution of coke and La2O2CO3 on the surface of catalyst, both of which have a close relation with catalytic performance.
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Effect of metal-support interaction on activity and stability of Ni-CeO2 catalyst for partial oxidation of methane
Article
  • Mar 2017
  • APPL CATAL B-ENVIRON
The objective of the current study was to synthesize a nickel based catalyst with high activity at low temperature for partial oxidation of methane (POM). Ni-nanoparticles supported on CeO2 nanoparticles were synthesized by two step preparation method. First, 30–50 nm CeO2 was synthesized by solvo-thermal method and then Ni- nanoparticles were deposited over it following a newly developed procedure, where cetyltrimethylammonium bromide (CTAB) acted as morphology controlling agent and polyvinylpyrrolidone (PVP) as size controlling agent for nickel nanoparticles. The characterizations of synthesized catalysts were done by BET-Surface area, XRD, SEM, TEM, TPR, H2-chemisorpton, TGA and XPS analysis. The catalysts showed excellent coke resisting ability during POM and produces synthesis gas with H2/CO ratio almost 2. The catalyst activated methane at 400 °C with 10% methane conversion and converts methane almost completely at 800 °C. The catalyst showed above 98% methane conversion at 800 °C during 90 h of time on stream (TOS) reaction with H2/CO ratio 1.98. Average 5.5 nm Ni particles, use of CeO2 as a support played a very crucial role for methane activation at such lower temperature. The synergistic effect between small Ni-nanoparticles and CeO2 nanoparticles of Ni-CeO2 catalyst is the main reason for such activity. Detailed study of other reaction parameters like temperature, Ni loading, weight hourly space velocity (WHSV) was also carried out and reported.
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