Origin and Nature of Coke in Ethanol Steam Reforming and Its Role in Deactivation of Ni/La2O3–αAl2O3 Catalyst

Montero, Carolina; Remiro, Aingeru; Valle, Beatríz; Oar‐Arteta, Lide; Bilbao, Javier; Gayubo, Ana G.

doi:10.1021/acs.iecr.9b02880

Cited by 79 publications

(58 citation statements)

References 58 publications

(118 reference statements)

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“…These methyl groups at lower temperatures desorb as CH4, with nickel's methanation activity also contributing to higher methane selectivities. Over all metals, acid sites on the support can promote in parallel ethanol's dehydration towards ethylene [28], while carbon deposition remains a major issue for the long term stability of Ni catalysts [29,30].…”

Section: Introductionmentioning

confidence: 99%

Elucidation of metal and support effects during ethanol steam reforming over Ni and Rh based catalysts supported on (CeO2)-ZrO2-La2O3

2021

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Section: Introductionmentioning

confidence: 99%

Elucidation of metal and support effects during ethanol steam reforming over Ni and Rh based catalysts supported on (CeO2)-ZrO2-La2O3

2021

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“…Several studies about the use of ethanol for hydrogen production technologies report two additional reactions, which can be responsible for the coke formation 39,40 :

2CO \leftrightarrow {CO}_{2} + normalC ΔH = - 173 kJ / mol,

C_{2} H_{4} \to carbonaceous polymeric compounds ((), coke) .

…”

Section: Resultsmentioning

confidence: 99%

“…Several studies about the use of ethanol for hydrogen production technologies report two additional reactions, which can be responsible for the coke formation 39,40 :…”

Section: Thermal Ethanol Decompositionmentioning

confidence: 99%

Pure hydrogen production by steam‐iron process: The synergic effect of MnO ₂ and Fe ₂ O ₃

et al. 2020

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Summary In the energy transition from fossil to clean fuels, hydrogen plays a key role. Proton‐exchange membrane fuel cells (PEMFCs) represent the most promising hydrogen application, but they require a pure hydrogen stream (CO < 10 ppm). The steam iron process represents a technology for the production of pure H2, exploiting iron redox cycles. If renewable reducing agents are used, the process can be considered completely green. In this context, bio‐ethanol can be an interesting solution that is still not thoroughly explored. In this work, the use of ethanol as a reducing agent in the steam iron process will be investigated. Ethanol, at high temperature, decomposes mainly in syngas but can also form coke, which can compromise the process effectiveness, reacting with water and producing CO together with H2. In this work, the deposition of coke is avoided by controlling the duration of the reduction step; in fact, the data demonstrated that coke deposition is significantly dependent on reduction time. Tests were carried out in a fixed bed reactor using hematite (Fe2O3) as raw iron oxide adopting several reduction times (7 minutes‐25 minutes), which correspond to different amount of ethanol fed (5 mmolC2H5OH/gFe2O3‐17,95 mmolC2H5OH/gFe2O3). The effect of the addition of MnO2 to increase the reduction degree of iron oxides was explored using different amount of MnO2 (10 wt% and 40 wt% with respect to Fe2O3). The tests were performed at fixed temperatures of 675°C and atmospheric pressure. The optimization of the reduction time, in the chosen operating condition, performed only with Fe2O3, shows that, feeding an amount of 5 mmolC2H5OH/gFe2O3, coke deposition is avoided and, therefore, a pure H2 stream in oxidation is obtained. The addition of MnO2 leads to increased H2 yield and process efficiency, confirming its positive effect on the reduction degree of the solid bed. A reaction pathway to demonstrate the synergic effect of Fe2O3 and MnO2 in the reduction step was proposed in this article.

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“…The DTA profile of the coke deposited on the used Ni-0.25Al-Zr catalyst shows three combustion peaks at 380, 680 and 850 • C, respectively. The peak at 380 • C evidences the presence of amorphous coke (monoatomic and polymeric carbon) that is adsorbed on the metal sites and cover them (encapsulating carbon) [41,42], which results in a rapid deactivation and low selectivity to H 2 as shown in figures 9 and 10d, respectively. This type of carbon may be attributed to polymeric carbon originating from ethylene polymerization and acetaldehyde decomposition reactions.…”

Section: Characterization Of Used Catalystsmentioning

confidence: 97%

Synthesis, characterization and catalytic application of Ni catalysts supported on alumina–zirconia mixed oxides

et al. 2017

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Alumina and alumina-zirconia mixed oxides were compared as supports to prepare nickel catalysts. The oxides were prepared by the sol-gel method using aluminum tri-sec-butoxide and zirconium (IV) propoxide as precursors, and its physicochemical properties were determined by BET, TGA, DTA, XRD, SEM and TEM. The catalysts of nickel were obtained by the impregnation of the supports with nickel nitrate (10 wt%) and were heat-treated at 700 • C. The specific area of the supports and catalysts decreased with the increase in the zirconia content in agreement with the crystalline phase formed. TEM micrographs of nickel catalysts revealed particles in the size range of 10-30 nm. The Ni/Al 2 O 3 -ZrO 2 catalysts were tested in the steam reforming reaction of ethanol (SRE) at 500 • C, and the obtained results suggest that the differences in catalytic activities depended on the content of ZrO 2 . The selectivity towards H 2 was ∼56% for the named catalyst Ni-Al-0.25Zr.

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Origin and Nature of Coke in Ethanol Steam Reforming and Its Role in Deactivation of Ni/La₂O₃–αAl₂O₃ Catalyst

Cited by 79 publications

References 58 publications

Elucidation of metal and support effects during ethanol steam reforming over Ni and Rh based catalysts supported on (CeO2)-ZrO2-La2O3

Elucidation of metal and support effects during ethanol steam reforming over Ni and Rh based catalysts supported on (CeO2)-ZrO2-La2O3

Pure hydrogen production by steam‐iron process: The synergic effect of MnO ₂ and Fe ₂ O ₃

Synthesis, characterization and catalytic application of Ni catalysts supported on alumina–zirconia mixed oxides

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Origin and Nature of Coke in Ethanol Steam Reforming and Its Role in Deactivation of Ni/La2O3–αAl2O3 Catalyst

Cited by 79 publications

References 58 publications

Elucidation of metal and support effects during ethanol steam reforming over Ni and Rh based catalysts supported on (CeO2)-ZrO2-La2O3

Elucidation of metal and support effects during ethanol steam reforming over Ni and Rh based catalysts supported on (CeO2)-ZrO2-La2O3

Pure hydrogen production by steam‐iron process: The synergic effect of MnO 2 and Fe 2 O 3

Synthesis, characterization and catalytic application of Ni catalysts supported on alumina–zirconia mixed oxides

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Origin and Nature of Coke in Ethanol Steam Reforming and Its Role in Deactivation of Ni/La₂O₃–αAl₂O₃ Catalyst

Pure hydrogen production by steam‐iron process: The synergic effect of MnO ₂ and Fe ₂ O ₃