Monitoring Ni 0 and coke evolution during the deactivation of a Ni/La 2 O 3 –αAl 2 O 3 catalyst in ethanol steam reforming in a fluidized bed

Montero, Carolina; Ochoa, Aitor; Castaño, Pedro; Bilbao, Javier; Gayubo, Ana G.

doi:10.1016/j.jcat.2015.08.005

Cited by 228 publications

(127 citation statements)

References 71 publications

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“…After 40 h, a plateau condition was reached and no more variation in both conversion and pressure drop profile was observed. Differently from the data reported by other authors, which observed almost steady performances followed by a severe drop in ethanol conversion and finally a slow decrease in ethanol conversion until total deactivation of the Ni-based catalysts, in this work steady performances were observed [66,67]. The experimental results showed, as commonly reported in the literature, that coke accumulation in the catalytic bed causes an appreciable increase in pressure drops; it is interesting to remark that, after 40 h of TOS, the absence of growth in pressure drops evidences no carbonaceous species accumulation.…”

Section: Catalytic Performances Of Ceo2-sio2 Based Samplescontrasting

confidence: 99%

Renewable Hydrogen from Ethanol Reforming over CeO2-SiO2 Based Catalysts

et al. 2017

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Abstract:In this research, a bimetallic Pt-Ni/CeO 2 -SiO 2 catalyst, synthetized via wet impregnation, was successfully employed for the oxidative steam reforming of ethanol between 300 and 600 • C. The reaction performance of the Pt-Ni catalyst was investigated and compared with the Ni/CeO 2 -SiO 2 , Pt/CeO 2 -SiO 2 as well as CeO 2 -SiO 2 sample. The bimetallic catalyst displayed the best results in terms of hydrogen yield and by-products selectivity, thus highlighting the crucial role of active species (Pt and Ni) in promoting ethanol conversion and reaching the products distribution predicted by thermodynamics. The most promising sample, tested at 500 • C for more than 120 h, assured total conversion and no apparent deactivation, demonstrating the stability of the selected formulation. By changing contact time, the dependence of carbon formation rate on space velocity was also investigated.

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Section: Catalytic Performances Of Ceo2-sio2 Based Samplescontrasting

confidence: 99%

Renewable Hydrogen from Ethanol Reforming over CeO2-SiO2 Based Catalysts

et al. 2017

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“…There are two DTA peaks, which implies that at least two kinds of coke formation occurs. Ni particles sinter to form bigger particles, and two types of coke are present for spent NiPS, one of which is filamentous and the other is nonfilamentous (Figure a) . The formation of filamentous carbon would not cause deactivation.…”

Section: Resultsmentioning

confidence: 99%

Sandwich‐Like Silica@Ni@Silica Multicore–Shell Catalyst for the Low‐Temperature Dry Reforming of Methane: Confinement Effect Against Carbon Formation

2017

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We synthesize a new sandwich‐like silica@Ni@silica multicore–shell catalyst. Firstly, Ni phyllosilicate (NiPS) is supported on silica nanospheres by a simple ammonia evaporation method. Then NiPS is coated with a layer of mesoporous silica to obtain a core–shell NiPS@silica structure by the hydrolysis of tetraethylorthosilicate (TEOS). The thickness of the shell can be tuned by varying the amount of TEOS. After calcination and H2 reduction at high temperature, multiple small Ni nanoparticles (≈6 nm) are generated and supported on the inner silica core but also encapsulated within the outer mesoporous silica shell. This silica@Ni@silica multicore–shell catalyst shows a high and stable conversion (≈60 %, gas hourly space velocity=60 000 mL h−1 gcat−1) for the dry reforming of methane (DRM) at 600 °C, whereas pristine NiPS deactivates quickly because of heavy carbon formation. We investigated the spent catalysts by using thermogravimetric analysis and TEM and found that there is almost no carbon formation for this new multicore–shell catalyst. Compared with a conventional Ni@silica core–shell catalyst, our multicore–shell catalyst is much easier to synthesize and the process does not require any toxic organic solvents. We believe that this strategy to make a multicore–shell catalyst can be applied to more nanomaterials and extended to other catalytic reactions besides DRM.

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“…Temperature programmed oxidation (TPO) using thermogravimetric analysis (TGA or TG) is by far the most common method used for the characterization of coke deposited on catalysts, gaining insights into the amount, nature or location of coke . The standard experimental procedure involves a linear heating program, and it allows a coke characterization based on the general criterion that fractions burning at lower temperatures have: (i) more hydrogenated nature, higher proportion of aliphatics with respect to aromatics; (ii) more oxygenated nature; (iii) higher accessibility within the catalyst porous structure; and/or (iv) higher proximity of coke to metallic sites, which catalyze coke combustion . TG‐TPO also allows the determination of coke combustion kinetics and quantification of the different coke fractions.…”

Section: Introductionmentioning

confidence: 99%

Temperature Programmed Oxidation Coupled with In Situ Techniques Reveal the Nature and Location of Coke Deposited on a Ni/La₂O₃‐αAl₂O₃ Catalyst in the Steam Reforming of Bio‐oil

et al. 2018

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The characterization of coke deposited on a Ni/La2O3‐αAl2O3 catalyst used in the steam reforming of bio‐oil has been studied by temperature programmed oxidation (TPO) coupled with different in situ techniques: thermogravimetry (TG), modulated thermogravimetry (MTG), FTIR spectroscopy with mass spectrometry (MS), Raman spectroscopy, and differential scanning calorimetry (DSC). The steam reforming of bio‐oil was carried out in a reactor equipment with two steps in series, comprising bio‐oil thermal treatment (500 °C) and subsequent reforming in a fluidized bed reactor (550–700 °C; and steam‐to‐carbon ratio, 1.5–6). TG/MS‐TPO experiments identify encapsulating and filamentous coke, and a more detailed analysis using other in situ techniques enable to characterize the nature and location of 4 types of coke: (i) an encapsulating coke with aliphatic nature placed in the most superficial layers; (ii) an encapsulating coke with higher aromatic nature in inner layers; (iii) the most superficial layers of a filamentous coke, further from active sites and with a more carbonized structure compared to encapsulating coke; and (iv) an innermost and mainly polyaromatic filamentous coke with a low oxygenates content.

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Monitoring Ni 0 and coke evolution during the deactivation of a Ni/La 2 O 3 –αAl 2 O 3 catalyst in ethanol steam reforming in a fluidized bed

Cited by 228 publications

References 71 publications

Renewable Hydrogen from Ethanol Reforming over CeO2-SiO2 Based Catalysts

Renewable Hydrogen from Ethanol Reforming over CeO2-SiO2 Based Catalysts

Sandwich‐Like Silica@Ni@Silica Multicore–Shell Catalyst for the Low‐Temperature Dry Reforming of Methane: Confinement Effect Against Carbon Formation

Temperature Programmed Oxidation Coupled with In Situ Techniques Reveal the Nature and Location of Coke Deposited on a Ni/La₂O₃‐αAl₂O₃ Catalyst in the Steam Reforming of Bio‐oil

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Monitoring Ni 0 and coke evolution during the deactivation of a Ni/La 2 O 3 –αAl 2 O 3 catalyst in ethanol steam reforming in a fluidized bed

Cited by 228 publications

References 71 publications

Renewable Hydrogen from Ethanol Reforming over CeO2-SiO2 Based Catalysts

Renewable Hydrogen from Ethanol Reforming over CeO2-SiO2 Based Catalysts

Sandwich‐Like Silica@Ni@Silica Multicore–Shell Catalyst for the Low‐Temperature Dry Reforming of Methane: Confinement Effect Against Carbon Formation

Temperature Programmed Oxidation Coupled with In Situ Techniques Reveal the Nature and Location of Coke Deposited on a Ni/La2O3‐αAl2O3 Catalyst in the Steam Reforming of Bio‐oil

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Temperature Programmed Oxidation Coupled with In Situ Techniques Reveal the Nature and Location of Coke Deposited on a Ni/La₂O₃‐αAl₂O₃ Catalyst in the Steam Reforming of Bio‐oil