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11 pages, 3690 KiB

Open AccessFeature PaperArticle

Modelling the Sintering of Nickel Particles Supported on γ-Alumina under Hydrothermal Conditions

by Isabelle Champon, Alain Bengaouer, Albin Chaise, Sébastien Thomas and Anne-Cécile Roger

Catalysts 2020, 10(12), 1477; https://doi.org/10.3390/catal10121477 - 17 Dec 2020

Cited by 7 | Viewed by 2750

Abstract

Sintering of nickel particles is a well-known path of deactivation for Ni/Al₂O₃ catalysts. Considering the CO₂ methanation in the context of Power-to-Gas, a sintering study for up to 300 h was performed in a controlled atmosphere between 450 and [...] Read more.

Sintering of nickel particles is a well-known path of deactivation for Ni/Al₂O₃ catalysts. Considering the CO₂ methanation in the context of Power-to-Gas, a sintering study for up to 300 h was performed in a controlled atmosphere between 450 and 600 °C. Since water is a product of the methanation reaction and is known to favor the particle sintering, the H₂O:H₂ molar ratio was varied in the range 0–3.2. Characterization of the post mortem samples showed sintering of both nickel and support particles. The absence of carbon oxides in the gas feed allows us to rule out other causes of deactivation such as carbon deposits. A sintering law is derived from the loss of metallic surface area with time-on-stream according to local temperature and H₂O:H₂ molar ratio. An excellent fit of the experimental data was obtained allowing the prediction of the metallic surface area within 15%. Full article

(This article belongs to the Special Issue CO₂ Capture and / or Its Transformation into Fuels or Valuable Chemicals)

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24 pages, 10440 KiB

Open AccessArticle

Enhancement of CO₂ Reforming of CH₄ Reaction Using Ni,Pd,Pt/Mg_1−xCe_x⁴⁺O and Ni/Mg_1−xCe_x⁴⁺O Catalysts

by Faris A. J. Al-Doghachi, Ali F. A. Jassim and Yun Hin Taufiq-Yap

Catalysts 2020, 10(11), 1240; https://doi.org/10.3390/catal10111240 - 27 Oct 2020

Cited by 9 | Viewed by 2474

Abstract

Catalysts Ni/Mg_1−xCe_x⁴⁺O and Ni,Pd,Pt/Mg_1−xCe_x⁴⁺O were developed using the co-precipitation–impregnation methods. Catalyst characterization took place using XRD, H₂-TPR, XRF, XPS, Brunauer–Emmett–Teller (BET), TGA TEM, and FE-SEM. Testing the catalysts for the dry [...] Read more.

Catalysts Ni/Mg_1−xCe_x⁴⁺O and Ni,Pd,Pt/Mg_1−xCe_x⁴⁺O were developed using the co-precipitation–impregnation methods. Catalyst characterization took place using XRD, H₂-TPR, XRF, XPS, Brunauer–Emmett–Teller (BET), TGA TEM, and FE-SEM. Testing the catalysts for the dry reforming of CH₄ took place at temperatures of 700–900 °C. Findings from this study revealed a higher CH₄ and CO₂ conversion using the tri-metallic Ni,Pd,Pt/Mg_1−xCe_x⁴⁺O catalyst in comparison with Ni monometallic systems in the whole temperature ranges. The catalyst Ni,Pd,Pt/Mg_0.85Ce⁴⁺_0.15O also reported an elevated activity level (CH₄; 78%, and CO₂; 90%) and an outstanding stability. Carbon deposition on spent catalysts was analyzed using TEM and Temperature programmed oxidation-mass spectroscopy (TPO-MS) following 200 h under an oxygen stream. The TEM and TPO-MS analysis results indicated a better anti-coking activity of the reduced catalyst along with a minimal concentration of platinum and palladium metals. Full article

(This article belongs to the Special Issue CO₂ Capture and / or Its Transformation into Fuels or Valuable Chemicals)

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17 pages, 4403 KiB

Open AccessArticle

Methanation of CO₂ over Cobalt-Lanthanide Aerogels: Effect of Calcination Temperature

by Joaquim Badalo Branco, Ricardo Pinto da Silva and Ana Cristina Ferreira

Catalysts 2020, 10(6), 704; https://doi.org/10.3390/catal10060704 - 23 Jun 2020

Cited by 11 | Viewed by 3083

Abstract

High surface area cobalt-lanthanide bimetallic aerogels were successfully synthesized by the epoxide addition method. The bimetallic aerogels were calcined at two different temperatures and either bimetallic oxides containing oxychlorides, Co₃O₄.3LnOCl (Ln = La, Sm, Gd, Dy and Yb) or [...] Read more.

High surface area cobalt-lanthanide bimetallic aerogels were successfully synthesized by the epoxide addition method. The bimetallic aerogels were calcined at two different temperatures and either bimetallic oxides containing oxychlorides, Co₃O₄.3LnOCl (Ln = La, Sm, Gd, Dy and Yb) or perovskites, LnCoO₃ (Ln = La, Sm, Gd and Dy) were obtained at 500 or 900 °C, respectively. The exceptions are the aerogels of cerium and ytterbium, which after oxidation at 500 and 900 °C, stabilize as sesquioxides: Co₃O₄.3CeO₂ and 2Co₃O₄.3Yb₂O₃, the first at both temperatures and the second only at the highest temperature. The bimetallic cobalt-lanthanide oxychlorides or perovskites were tested as catalysts for the methanation of CO₂. The cobalt catalytic activity is determined by the type and acid-base properties of the lanthanide oxide phase and by its pre-reduction under hydrogen. The best results were those obtained over the calcined aerogels pre-reduced under hydrogen. In particular, the highest values were those obtained over the Co-Ce aerogel calcined at 900 °C that in the same conditions present an activity comparable to that measured over a 5 wt.% Rh catalyst supported on alumina, one of the literature references. The activity and the selectivity increase with the catalysts’ basicity, showing an inverse dependence of the reduction temperature that decreases along the lanthanide series either for the aerogels calcined at 500 or 900 °C. In general, the basicity of the aerogels calcined at 900 °C (perovskites) is higher and they are more active but less selective than those calcined at 500 °C (oxychlorides), which to our knowledge is for the first time reported for the methanation of CO₂. Full article

(This article belongs to the Special Issue CO₂ Capture and / or Its Transformation into Fuels or Valuable Chemicals)

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14 pages, 2767 KiB

Open AccessArticle

Continuous Process for Carbon Dioxide Capture Using Lysine and Tetrabutyl Phosphonium Lysinate Aqueous Mixtures in a Packed Tower

by Antonio de Jesús Zúñiga-Mendiola, Diana Rosa Gómora-Herrera, Juan Manuel García-González and Javier Guzmán-Pantoja

Catalysts 2020, 10(4), 426; https://doi.org/10.3390/catal10040426 - 14 Apr 2020

Cited by 3 | Viewed by 3318

Abstract

The CO₂ absorption process using aqueous solutions of lysine (Lys), the ionic liquid (IL) tetrabutyl phosphonium lysinate ([TBP][Lys]) and their mixtures was studied by means of a packed tower. The performance of these systems was evaluated through the volumetric overall mass transfer [...] Read more.

The CO₂ absorption process using aqueous solutions of lysine (Lys), the ionic liquid (IL) tetrabutyl phosphonium lysinate ([TBP][Lys]) and their mixtures was studied by means of a packed tower. The performance of these systems was evaluated through the volumetric overall mass transfer coefficient (

K_{G} a_{V})

, conducting experiments under diverse conditions such as inlet CO₂ concentration from 10 to 40 vol.%, gas and absorbent flow rates from 100 to 200 mL/min and from 3 to 5 mL/min, respectively, absorbent concentration from 5 to 15 wt.% and temperature from 15 to 40 °C. The obtained results for all the previous experimental conditions were better for the IL/Lys mixture than for the isolated components; the best performance was shown by the experiment varying the absorbent concentration, where the increasing

K_{G} a_{V}

was benefited by the IL/Lys synergistic effect. Full article

(This article belongs to the Special Issue CO₂ Capture and / or Its Transformation into Fuels or Valuable Chemicals)

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20 pages, 7854 KiB

Open AccessArticle

CO₂ Methanation over Hydrotalcite-Derived Nickel/Ruthenium and Supported Ruthenium Catalysts

by Joana A. Martins, A. Catarina Faria, Miguel A. Soria, Carlos V. Miguel, Alírio E. Rodrigues and Luís M. Madeira

Catalysts 2019, 9(12), 1008; https://doi.org/10.3390/catal9121008 - 1 Dec 2019

Cited by 35 | Viewed by 5550

Abstract

In this work, in-house synthesized NiMgAl, Ru/NiMgAl, and Ru/SiO₂ catalysts and a commercial ruthenium-containing material (Ru/Al₂O₃^com.) were tested for CO₂ methanation at 250, 300, and 350 °C (weight hourly space velocity, WHSV, of 2400 mL [...] Read more.

In this work, in-house synthesized NiMgAl, Ru/NiMgAl, and Ru/SiO₂ catalysts and a commercial ruthenium-containing material (Ru/Al₂O₃^com.) were tested for CO₂ methanation at 250, 300, and 350 °C (weight hourly space velocity, WHSV, of 2400 mL_N,CO2·g⁻¹·h⁻¹). Materials were compared in terms of CO₂ conversion and CH₄ selectivity. Still, their performances were assessed in a short stability test (24 h) performed at 350 °C. All catalysts were characterized by temperature programmed reduction (TPR), X-ray diffraction (XRD), N₂ physisorption at −196 °C, inductively coupled plasma optical emission spectrometry (ICP-OES), and H₂/CO chemisorption. The catalysts with the best performance (i.e., the hydrotalcite-derived NiMgAl and Ru/NiMgAl) seem to be quite promising, even when compared with other methanation catalysts reported in the literature. Extended stability experiments (240 h of time-on-stream) were performed only over NiMgAl, which was selected based on catalytic performance and estimated price criteria. This catalyst showed some deactivation under conditions that favor CO formation (high temperature and high WHSV, i.e., 350 °C and 24,000 mL_N,CO2·g⁻¹·h⁻¹, respectively), but at 300 °C and low WHSV, excellent activity (ca. 90% of CO₂ conversion) and stability, with nearly complete selectivity towards methane, were obtained. Full article

(This article belongs to the Special Issue CO₂ Capture and / or Its Transformation into Fuels or Valuable Chemicals)

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16 pages, 9066 KiB

Open AccessArticle

Ti³⁺ Defective SnS₂/TiO₂ Heterojunction Photocatalyst for Visible-Light Driven Reduction of CO₂ to CO with High Selectivity

by Aiguo Han, Mei Li, Shengbo Zhang, Xinli Zhu, Jinyu Han, Qingfeng Ge and Hua Wang

Catalysts 2019, 9(11), 927; https://doi.org/10.3390/catal9110927 - 6 Nov 2019

Cited by 30 | Viewed by 3666

Abstract

In recent years, defective TiO₂-based composite nanomaterials have received much attention in the field of photocatalysis. In this work, TiB₂ was used as a precursor to successfully prepare Ti³⁺ defective TiO₂ (TiO₂-B) with a truncated bipyramidal [...] Read more.

In recent years, defective TiO₂-based composite nanomaterials have received much attention in the field of photocatalysis. In this work, TiB₂ was used as a precursor to successfully prepare Ti³⁺ defective TiO₂ (TiO₂-B) with a truncated bipyramidal structure by a one-step method. Then, the SnS₂ nanosheets were assembled onto the as-prepared TiO₂-B through simple hydrothermal reaction. TiO₂-B exhibits strong visible light absorption properties, but the recombination rate of the photo-generated electron-hole pair was high and does not exhibit ideal photocatalytic performance. Upon introducing SnS₂, the heterojunction catalyst SnS₂-Ti³⁺ defective TiO₂ (SnS₂/TiO₂-B) not only possesses the strong light absorption from UV to visible light region, the lowest photo-generated charge recombination rate but also achieves a more negative conduction band potential than the reduction potential of CO₂ to CO, and thereby, exhibits the significantly enhanced selectivity and yield of CO in photocatalytic CO₂ reduction. Notably, SnS₂/TiO₂-B produces CO at a rate of 58 µmol·h⁻¹·g⁻¹ with CO selectivity of 96.3% under visible light irradiation, which is 2 and 19 times greater than those of alone TiO₂-B and SnS₂, respectively. Finally, a plausible photocatalytic mechanism on SnS₂/TiO₂-B was proposed that the electron transfer between TiO₂ and SnS₂ follows the Z-scheme mode. Our results present an effective way to gain highly efficient TiO₂ based photocatalysts for CO₂ reduction by combining different modification methods of TiO₂ and make full use of the synergistic effects. Full article

(This article belongs to the Special Issue CO₂ Capture and / or Its Transformation into Fuels or Valuable Chemicals)

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12 pages, 1643 KiB

Open AccessArticle

Performance Analysis of Biocathode in Bioelectrochemical CO₂ Reduction

by Anirudh Bhanu Teja Nelabhotla, Rune Bakke and Carlos Dinamarca

Catalysts 2019, 9(8), 683; https://doi.org/10.3390/catal9080683 - 12 Aug 2019

Cited by 13 | Viewed by 3942

Abstract

Microbial electrosynthesis (MES) biogas upgrading is done via reduction of carbon dioxide to methane through electroactive microbial catalysis. The baseline MES mode of operation showed about a 39% increase in the methane production rate compared to the open circuit mode of operation. MES [...] Read more.

Microbial electrosynthesis (MES) biogas upgrading is done via reduction of carbon dioxide to methane through electroactive microbial catalysis. The baseline MES mode of operation showed about a 39% increase in the methane production rate compared to the open circuit mode of operation. MES is capable of producing acetic acid at relatively more negative potential (−0.80 to –0.90 V vs. Standard Hydrogen Electrode (SHE)) than the potential at which it produces methane (−0.65 V vs. SHE). The optimum pH for enhancing the electroactive acetogens is found to be around 6.8–7.0 while a pH of around 7.0–7.5 enhances the electroactive methanogens performance. The biocathode adaptation test reveals that 45% of the methane was produced through the electrochemical pathway with a coulombic efficiency of 100% while maintaining heterotrophic efficiency above 99%. Full article

(This article belongs to the Special Issue CO₂ Capture and / or Its Transformation into Fuels or Valuable Chemicals)

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Review

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25 pages, 4026 KiB

Open AccessReview

Advances in Clean Fuel Ethanol Production from Electro-, Photo- and Photoelectro-Catalytic CO₂ Reduction

by Yanfang Song, Wei Chen, Wei Wei and Yuhan Sun

Catalysts 2020, 10(11), 1287; https://doi.org/10.3390/catal10111287 - 5 Nov 2020

Cited by 29 | Viewed by 6792

Abstract

Using renewable energy to convert CO₂ to a clean fuel ethanol can not only reduce carbon emission through the utilization of CO₂ as feedstock, but also store renewable energy as the widely used chemical and high-energy-density fuel, being considered as a [...] Read more.

Using renewable energy to convert CO₂ to a clean fuel ethanol can not only reduce carbon emission through the utilization of CO₂ as feedstock, but also store renewable energy as the widely used chemical and high-energy-density fuel, being considered as a perfect strategy to address current environment and energy issues. Developing efficient electrocatalysts, photocatalysts, and photoelectrocatalysts for CO₂ reduction is the most crucial keystone for achieving this goal. Considerable progresses in CO₂-based ethanol production have been made over the past decades. This review provides the general principles and summarizes the latest advancements in electrocatalytic, photocatalytic and photoelectrocatalytic CO₂ conversion to ethanol. Furthermore, the main challenges and proposed future prospects are illustrated for further developments in clean fuel ethanol production. Full article

(This article belongs to the Special Issue CO₂ Capture and / or Its Transformation into Fuels or Valuable Chemicals)

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