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4 pages, 196 KiB

Open AccessEditorial

Editorial—Special Issue “Catalysis for Energy Production”

by Maria A. Goula and Kyriaki Polychronopoulou

Catalysts 2021, 11(7), 785; https://doi.org/10.3390/catal11070785 - 28 Jun 2021

Cited by 1 | Viewed by 1837

Abstract

The rapid increase in anthropogenic greenhouse gas concentrations in the last several decades means that the effects of climate change are fast becoming the familiar horsemen of a planetary apocalypse. Catalysis, one of the pillars of the chemical and petrochemical industries, will play [...] Read more.

The rapid increase in anthropogenic greenhouse gas concentrations in the last several decades means that the effects of climate change are fast becoming the familiar horsemen of a planetary apocalypse. Catalysis, one of the pillars of the chemical and petrochemical industries, will play a critical role in the effort to reduce the flow of greenhouse gases into the atmosphere. This Special Issue is timely, as it provides a collection of high-quality manuscripts in a diverse range of topics, which include the production of green hydrogen via water electrolysis, the steam reforming of ethanol, propane or glycerol, the dry reforming of methane, and the autothermal reforming of diesel surrogate fuel. The topic of the transformation of biomass waste to chemicals is also well represented as is the tackling of CO₂ emissions via novel utilization technologies. The Editors are grateful to all authors for their valuable contributions and confident that this Special Issue will prove valuable to scholars, university professors and students alike. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

Research

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17 pages, 2581 KiB

Open AccessArticle

RETRACTED: Experimental Study of CO₂ Conversion into Methanol by Synthesized Photocatalyst (ZnFe₂O₄/TiO₂) Using Visible Light as an Energy Source

by Numair Manzoor, Muhammad Sadiq, Muhammad Naqvi, Umair Sikandar and Salman Raza Naqvi

Catalysts 2020, 10(2), 163; https://doi.org/10.3390/catal10020163 - 1 Feb 2020

Cited by 17 | Viewed by 4486 | Retraction

Abstract

Ozone layer depletion is a serious threat due to the extensive release of greenhouse gases. The emission of carbon dioxide (CO₂) from fossil fuel combustion is a major reason for global warming. Energy demands and climate change are coupled with each [...] Read more.

Ozone layer depletion is a serious threat due to the extensive release of greenhouse gases. The emission of carbon dioxide (CO₂) from fossil fuel combustion is a major reason for global warming. Energy demands and climate change are coupled with each other. CO₂is a major gas contributing to global warming; hence, the conversion of CO₂ into useful products such as methanol, formic acid, formaldehyde, etc., under visible light is an attractive topic. Challenges associated with the current research include synthesizing a photocatalyst that is driven by visible light with a narrow band gap range between 2.5 and 3.0 eV, the separation of a mixed end product, and the two to three times faster recombination rate of an electron–hole pair compared with separation over yield. The purpose of the current research is to convert CO₂ into useful fuel i.e., methanol; the current study focuses on the photocatalytic reduction of CO₂into a useful product. This research is based on the profound analysis of published work, which allows the selection of appropriate methods and material for this research. In this study, zinc ferrite (ZnFe₂O₄) is synthesized via the modified sol–gel method and coupled with titanium dioxide (TiO₂). Thereafter, the catalyst is characterized by Fourier transform infrared (FTIR), FE-SEM, UV–Vis, and XRD characterization techniques. UV–Vis illustrates that the synthesized catalyst has a low band gap and utilizes a major portion of visible light irradiation. The XRD pattern was confirmed by the formation of the desired catalyst. FE-SEM illustrated that the size of the catalyst ranges from 50 to 500 nm and BET analysis determined the surface area, which was 2.213 and 6.453 m²/g for ZnFe₂O₄ and ZnFe₂O_4/TiO₂, respectively. The continuous gas flow photoreactor was used to study the activity of the synthesized catalyst, while titanium dioxide (TiO₂) has been coupled with zinc ferrite (ZnFe₂O₄) under visible light in order to obtain the maximum yield of methanol as a single product and simultaneously avoid the conversion of CO₂ into multiple products. The performance of ZnFe₂O_4/TiO₂was mainly assessed through methanol yield with a variable amount of TiO₂ over ZnFe₂O₄ (1:1, 1:2, 2:1, 1:3, and 3:1). The synthesized catalyst recycling ability has been tested up to five cycles. Finally, we concluded that the optimum conditions for maximum yield were found to be a calcination temperature of ZnFe₂O₄at 900 °C, and optimum yield was at a 1:1 w/w coupling ratio of ZnFe₂O₄/TiO₂. It was observed that due to the enhancement in the electron–hole pair lifetime, the methanol yield at 141.22 μmol/g_cat·h over ZnFe₂O₄/TiO₂was found to be 7% higher than the earlier reported data. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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14 pages, 4189 KiB

Open AccessArticle

Hydrogen Production from Ammonia Borane over PtNi Alloy Nanoparticles Immobilized on Graphite Carbon Nitride

by Mingya Zhang, Xue Xiao, Yan Wu, Yue An, Lixin Xu and Chao Wan

Catalysts 2019, 9(12), 1009; https://doi.org/10.3390/catal9121009 - 1 Dec 2019

Cited by 22 | Viewed by 4044

Abstract

Graphite carbon nitride (g-C₃N₄) supported PtNi alloy nanoparticles (NPs) were fabricated via a facile and simple impregnation and chemical reduction method and explored their catalytic performance towards hydrogen evolution from ammonia borane (AB) hydrolysis dehydrogenation. Interestingly, the resultant Pt [...] Read more.

Graphite carbon nitride (g-C₃N₄) supported PtNi alloy nanoparticles (NPs) were fabricated via a facile and simple impregnation and chemical reduction method and explored their catalytic performance towards hydrogen evolution from ammonia borane (AB) hydrolysis dehydrogenation. Interestingly, the resultant Pt_0.5Ni_0.5/g-C₃N₄ catalyst affords superior performance, including 100% conversion, 100% H₂ selectivity, yielding the extraordinary initial total turnover frequency (TOF) of 250.8 mol_H2 min⁻¹ (mol_Pt)⁻¹ for hydrogen evolution from AB at 10 °C, a relatively low activation energy of 38.09 kJ mol⁻¹, and a remarkable reusability (at least 10 times), which surpass most of the noble metal heterogeneous catalysts. This notably improved activity is attributed to the charge interaction between PtNi NPs and g-C₃N₄ support. Especially, the nitrogen-containing functional groups on g-C₃N₄, serving as the anchoring sites for PtNi NPs, may be beneficial for becoming a uniform distribution and decreasing the particle size for the NPs. Our work not only provides a cost-effective route for constructing high-performance catalysts towards the hydrogen evolution of AB but also prompts the utilization of g-C₃N₄ in energy fields. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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20 pages, 8095 KiB

Open AccessArticle

Ni Catalysts Based on Attapulgite for Hydrogen Production through the Glycerol Steam Reforming Reaction

by Nikolaos D. Charisiou, Victor Sebastian, Steven J. Hinder, Mark A. Baker, Kyriaki Polychronopoulou and Maria A. Goula

Catalysts 2019, 9(8), 650; https://doi.org/10.3390/catal9080650 - 30 Jul 2019

Cited by 29 | Viewed by 3785

Abstract

Attapulgite (ATP, a natural clay) was used as carrier to produce a nickel-based catalyst (Ni/ATP) for the work that is presented herein. Its catalytic performance was comparatively assessed with a standard Ni/Al₂O₃ sample for the glycerol steam reforming (GSR) reaction. [...] Read more.

Attapulgite (ATP, a natural clay) was used as carrier to produce a nickel-based catalyst (Ni/ATP) for the work that is presented herein. Its catalytic performance was comparatively assessed with a standard Ni/Al₂O₃ sample for the glycerol steam reforming (GSR) reaction. It was shown that the ATP support led to lower mean Ni crystallite size, i.e., it increased the dispersion of the active phase, to the easier reduction of NiO and also increased the basicity of the catalytic material. It was also shown that it had a significant effect on the distribution of the gaseous products. Specifically, for the Ni/ATP catalyst, the production of liquid effluents was minimal and subsequently, conversion of glycerol into gaseous products was higher. Importantly, the Ni/ATP favored the conversion into H₂ and CO₂ to the detriment of CO and CH₄. The stability experiments, which were undertaken at a low WGFR, showed that the activity of both catalysts was affected with time as a result of carbon deposition and/or metal particle sintering. An examination of the spent catalysts revealed that the coke deposits consisted of filamentous carbon, a type that is known to encapsulate the active phase with fatal consequences. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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14 pages, 4529 KiB

Open AccessArticle

Continuous-Flow Process for Glycerol Conversion to Solketal Using a Brönsted Acid Functionalized Carbon-Based Catalyst

by Vanesa Domínguez-Barroso, Concepción Herrera, María Ángeles Larrubia, Rafael González-Gil, Marina Cortés-Reyes and Luis J. Alemany

Catalysts 2019, 9(7), 609; https://doi.org/10.3390/catal9070609 - 18 Jul 2019

Cited by 22 | Viewed by 5233

Abstract

The acetalization of glycerol with acetone represents a strategy for its valorization into solketal as a fuel additive component. Thus, acid carbon-based structured catalyst (SO₃H-C) has been prepared, characterized and tested in this reaction. The structured catalyst (L = 5 cm, [...] Read more.

The acetalization of glycerol with acetone represents a strategy for its valorization into solketal as a fuel additive component. Thus, acid carbon-based structured catalyst (SO₃H-C) has been prepared, characterized and tested in this reaction. The structured catalyst (L = 5 cm, d = 1 cm) showed a high surface density of acidic sites (2.9 mmol H⁺ g⁻¹) and a high surface area. This catalyst is highly active and stable in the solketal reaction production in a batch reactor system and in a continuous downflow reactor, where several parameters were studied such as the variation of time of reaction, temperature, acetone/glycerol molar ratio (A/G) and weight hourly space velocity (WHSV). A complete glycerol conversion and 100% of solketal selectivity were achieved working in the continuous flow reactor equipped with distillation equipment when WHSV is 2.9 h⁻¹, A/G = 8 at 57 °C in a co-solvent free operation. The catalyst maintained its activity under continuous flow even after 300 min of reaction. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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12 pages, 2335 KiB

Open AccessArticle

Nanostructured Fe-Ni Sulfide: A Multifunctional Material for Energy Generation and Storage

by Chen Zhao, Chunyang Zhang, Sanket Bhoyate, Pawan K. Kahol, Nikolaos Kostoglou, Christian Mitterer, Steve Hinder, Mark Baker, Georgios Constantinides, Kyriaki Polychronopoulou, Claus Rebholz and Ram K. Gupta

Catalysts 2019, 9(7), 597; https://doi.org/10.3390/catal9070597 - 11 Jul 2019

Cited by 21 | Viewed by 5511

Abstract

Multifunctional materials for energy conversion and storage could act as a key solution for growing energy needs. In this study, we synthesized nanoflower-shaped iron-nickel sulfide (FeNiS) over a nickel foam (NF) substrate using a facile hydrothermal method. The FeNiS electrode showed a high [...] Read more.

Multifunctional materials for energy conversion and storage could act as a key solution for growing energy needs. In this study, we synthesized nanoflower-shaped iron-nickel sulfide (FeNiS) over a nickel foam (NF) substrate using a facile hydrothermal method. The FeNiS electrode showed a high catalytic performance with a low overpotential value of 246 mV for the oxygen evolution reaction (OER) to achieve a current density of 10 mA/cm², while it required 208 mV at 10 mA/cm² for the hydrogen evolution reaction (HER). The synthesized electrode exhibited a durable performance of up to 2000 cycles in stability and bending tests. The electrolyzer showed a lower cell potential requirement for a FeNiS-Pt/C system (1.54 V) compared to a standard benchmark IrO₂-Pt/C system (1.56 V) to achieve a current density of 10 mA/cm². Furthermore, the FeNiS electrode demonstrated promising charge storage capabilities with a high areal capacitance of 13.2 F/cm². Our results suggest that FeNiS could be used for multifunctional energy applications such as energy generation (OER and HER) and storage (supercapacitor). Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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13 pages, 2671 KiB

Open AccessArticle

Enhanced Ni-Al-Based Catalysts and Influence of Aromatic Hydrocarbon for Autothermal Reforming of Diesel Surrogate Fuel

by Dong Geon Ju, Seong Bin Jo, Dong Su Ha, Tae Young Kim, Suk Yong Jung, Ho Jin Chae, Soo Chool Lee and Jae Chang Kim

Catalysts 2019, 9(7), 573; https://doi.org/10.3390/catal9070573 - 28 Jun 2019

Cited by 14 | Viewed by 3190

Abstract

Aromatic hydrocarbons along with sulfur compounds in diesel fuel pose a significant threat to catalytic performances, due mainly to carbon deposition on the catalytic surface. In order to investigate the influence of an aromatic hydrocarbon on the autothermal reforming of diesel fuel, 1-methylnaphthalene [...] Read more.

Aromatic hydrocarbons along with sulfur compounds in diesel fuel pose a significant threat to catalytic performances, due mainly to carbon deposition on the catalytic surface. In order to investigate the influence of an aromatic hydrocarbon on the autothermal reforming of diesel fuel, 1-methylnaphthalene (C₁₁H₁₀) was selected as an aromatic hydrocarbon. Two types of diesel surrogate fuel, i.e., DH (dodecane (C₁₂H₂₆) and hexadecane (C₁₆H₃₄) mixture) as well as DHM (DH fuel and C₁₁H₁₀ mixture) fuel, were prepared. A Rh-Al-based catalyst (R5A-I) was prepared using a conventional impregnation method. Various Ni-Al-based catalysts with Fe and Rh promoters were prepared via a polymer modified incipient method to improve the carbon coking resistance. These catalysts were tested under conditions of S/C = 1.17, O₂/C = 0.24, 750 °C, and GHSV = 12,000 h^-1 at DH or DHM fuel. R5A-I exhibited excellent catalytic performance in both DH and DHM fuels. However, carbon coking and sulfur poisoning resistance were observed in our previous study for the Ni-Al-based catalyst with the Fe promoter, which became deactivated with increasing reaction time at the DHM fuel. In the case of the Rh promoter addition to the Ni-Al-based catalysts, the catalytic performances decreased relatively slowly with increasing (from 1 wt.% (R1N50A) to 2 wt.% (R2N50A)) content of Rh₂O₃ at DHM fuel. The catalysts were analyzed via scanning electron microscopy combined with energy dispersive X-ray, X-ray diffraction, and X-ray photoelectron spectroscopy. Gas chromatography-mass spectrometry detected various types of hydrocarbons, e.g., ethylene (C₂H₄), with catalyst deactivation. The results revealed that, among the produced hydrocarbons, C₂H₄ played a major role in accelerating carbon deposition that blocks the reforming reaction. Therefore, Rh metal deserves consideration as a carbon coking inhibitor that prevents the negative effects of the C₂H₄ for autothermal reforming of diesel fuel in the presence of aromatic hydrocarbons. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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17 pages, 2617 KiB

Open AccessArticle

Intrinsic Kinetics Study of Biogas Methanation Coupling with Water Gas Shift over Re-Promoted Ni Bifunctional Catalysts

by Xinxin Dong, Baosheng Jin, Zhiwei Kong and Lu Dong

Catalysts 2019, 9(5), 422; https://doi.org/10.3390/catal9050422 - 6 May 2019

Cited by 4 | Viewed by 3361

Abstract

The intrinsic kinetics of biogas methanation coupling with water gas shift over Re-promoted Ni bifunctional catalysts were investigated in this study. The catalysts were prepared through co-impregnation of Ni and Re precursors on the H₂O₂-modified manganese sand. The experiments [...] Read more.

The intrinsic kinetics of biogas methanation coupling with water gas shift over Re-promoted Ni bifunctional catalysts were investigated in this study. The catalysts were prepared through co-impregnation of Ni and Re precursors on the H₂O₂-modified manganese sand. The experiments were performed in a fixed bed reactor under the assorted reaction conditions of 300–400 °C, 0.1–0.3 MPa, and a 0.6–1.0 H₂/CO ratio. The effect of gas internal and external diffusion on the performance of methanation coupling with water gas shift was examined by changing catalyst particle size and gas hourly space velocity (GHSV) and further verified by the Weisz–Prater and Mears criterion, respectively. It was found that the internal and external diffusions were eliminated when the catalyst particle size was 12–14 meshes and GHSV was 2000 h⁻¹. Three kinetics models including the empirical model (EM), synergetic model (SM), and independent model (IM) were proposed, and 25 sets of experimental data were obtained to solve the model parameters. By mathematical fitting and analysis, it was discovered that the fitting situation of the three kinetics models was in the order of EM > SM > IM, among which EM had the highest fitting degree of 99.7% for CH₄ and 99.9% for CO₂ with the lowest average relative error of 8.9% for CH₄ and 8.7% for CO₂. The over 30% of average relative error for CO₂ in IM might exclude the possibility of the Langmuir–Hinshelwood water gas shift mechanism in the real steps of biogas methanation coupling with water gas shift over Re-promoted Ni catalysts. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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14 pages, 3960 KiB

Open AccessArticle

Efficient Biodiesel Conversion from Microalgae Oil of Schizochytrium sp.

by Dingyaw Kuan, Lingmei Dai, Dehua Liu, Hongjuan Liu and Wei Du

Catalysts 2019, 9(4), 341; https://doi.org/10.3390/catal9040341 - 6 Apr 2019

Cited by 9 | Viewed by 3971

Abstract

Microalgae oil has been regarded as a promising feedstock for biodiesel production. However, microalgae oil usually contains some non-lipid components, such as pigments. Microalgae oil could be converted to biodiesel effectively with a two-step process to decrease the negative effect caused by by-product [...] Read more.

Microalgae oil has been regarded as a promising feedstock for biodiesel production. However, microalgae oil usually contains some non-lipid components, such as pigments. Microalgae oil could be converted to biodiesel effectively with a two-step process to decrease the negative effect caused by by-product glycerol generated in traditional biodiesel production process. Firstly, microalgae oil was hydrolysed to free fatty acids (FFAs) and then FFAs were converted to methyl ester. In this study, the hydrolysis of microalgae oil from Schizochytrium sp. was systematically investigated and microalgae oil could be hydrolysed effectively to FFAs at both non-catalytic and acid-catalytic conditions. The hydrolysis degree of 97.5% was obtained under non-catalytic conditions of 220 °C and a water to oil ratio of 10:1 (w:w). The hydrolysis degree of 97.1% was obtained with the optimized sulphuric acid catalytic conditions of 95 °C, and a ratio of water to oil 3:1. The lipase Novozym435-mediated esterification with the hydrolysed FFAs was explored and a FAME (Fatty Acids Methyl Ester) yield of 95.1% was achieved. The conversion of different FFAs also was compared and the results indicated that lipase Novozym435-mediated methanolysis was effective for the preparation of biodiesel as well as poly unsaturated fatty acids (PUFAs). Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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11 pages, 2197 KiB

Open AccessArticle

Electrodeposited Nanostructured CoFe₂O₄ for Overall Water Splitting and Supercapacitor Applications

by Chunyang Zhang, Sanket Bhoyate, Chen Zhao, Pawan K. Kahol, Nikolaos Kostoglou, Christian Mitterer, Steven J. Hinder, Mark A. Baker, Georgios Constantinides, Kyriaki Polychronopoulou, Claus Rebholz and Ram K. Gupta

Catalysts 2019, 9(2), 176; https://doi.org/10.3390/catal9020176 - 13 Feb 2019

Cited by 71 | Viewed by 8468

Abstract

To contribute to solving global energy problems, a multifunctional CoFe₂O₄ spinel was synthesized and used as a catalyst for overall water splitting and as an electrode material for supercapacitors. The ultra-fast one-step electrodeposition of CoFe₂O₄ over conducting [...] Read more.

To contribute to solving global energy problems, a multifunctional CoFe₂O₄ spinel was synthesized and used as a catalyst for overall water splitting and as an electrode material for supercapacitors. The ultra-fast one-step electrodeposition of CoFe₂O₄ over conducting substrates provides an economic pathway to high-performance energy devices. Electrodeposited CoFe₂O₄ on Ni-foam showed a low overpotential of 270 mV and a Tafel slope of 31 mV/dec. The results indicated a higher conductivity for electrodeposited compared with dip-coated CoFe₂O₄ with enhanced device performance. Moreover, bending and chronoamperometry studies suggest excellent durability of the catalytic electrode for long-term use. The energy storage behavior of CoFe₂O₄ showed high specific capacitance of 768 F/g at a current density of 0.5 A/g and maintained about 80% retention after 10,000 cycles. These results demonstrate the competitiveness and multifunctional applicability of the CoFe₂O₄ spinel to be used for energy generation and storage devices. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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13 pages, 2052 KiB

Open AccessArticle

Efficient Catalytic Dehydration of High-Concentration 1-Butanol with Zn-Mn-Co Modified γ-Al₂O₃ in Jet Fuel Production

by Jing Wu, Hong-Juan Liu, Xiang Yan, Yu-Jie Zhou, Zhang-Nan Lin, Shuo Mi, Ke-Ke Cheng and Jian-An Zhang

Catalysts 2019, 9(1), 93; https://doi.org/10.3390/catal9010093 - 16 Jan 2019

Cited by 14 | Viewed by 4855

Abstract

It is important to develop full-performance bio-jet fuel based on alternative feedstocks. The compound 1-butanol can be transformed into jet fuel through dehydration, oligomerization, and hydrogenation. In this study, a new catalyst consisting of Zn-Mn-Co modified γ-Al₂O₃ was used for [...] Read more.

It is important to develop full-performance bio-jet fuel based on alternative feedstocks. The compound 1-butanol can be transformed into jet fuel through dehydration, oligomerization, and hydrogenation. In this study, a new catalyst consisting of Zn-Mn-Co modified γ-Al₂O₃ was used for the dehydration of high-concentration 1-butanol to butenes. The interactive effects of reaction temperature and butanol weight-hourly space velocity (WHSV) on butene yield were investigated with response surface methodology (RSM). Butene yield was enhanced when the temperature increased from 350 °C to 450 °C but it was reduced as WHSV increased from 1 h⁻¹ to 4 h⁻¹. Under the optimized conditions of 1.67 h⁻¹ WHSV and 375 °C reaction temperature, the selectivity of butenes achieved 90%, and the conversion rate of 1-butanol reached 100%, which were 10% and 6% higher, respectively, than when using unmodified γ-Al₂O₃. The Zn-Mn-Co modified γ-Al₂O₃ exhibited high stability and a long lifetime of 180 h, while the unmodified γ-Al₂O₃ began to deactivate after 60 h. Characterization with X-ray diffraction (XRD), nitrogen adsorption-desorption, pyridine temperature-programmed desorption (Py-TPD), pyridine adsorption IR spectra, and inductively coupled plasma atomic emission spectrometry (ICP-AES), showed that the crystallinity and acid content of γ-Al₂O₃ were obviously enhanced by the modification with Zn-Mn-Co, and the loading amounts of zinc, manganese, and cobalt were 0.54%, 0.44%, and 0.23%, respectively. This study provides a new catalyst, and the results will be helpful for the further optimization of bio-jet fuel production with a high concentration of 1-butanol. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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18 pages, 5207 KiB

Open AccessArticle

Ce- and Y-Modified Double-Layered Hydroxides as Catalysts for Dry Reforming of Methane: On the Effect of Yttrium Promotion

by Katarzyna Świrk, Magnus Rønning, Monika Motak, Patricia Beaunier, Patrick Da Costa and Teresa Grzybek

Catalysts 2019, 9(1), 56; https://doi.org/10.3390/catal9010056 - 8 Jan 2019

Cited by 37 | Viewed by 4770

Abstract

Ce- and Y-promoted double-layered hydroxides were synthesized and tested in dry reforming of methane (CH₄/CO₂ = 1/1). The characterization of the catalysts was performed using X-ray fluorescence (XRF), X-ray diffraction (XRD), N₂ sorption, temperature-programmed reduction in H₂ (TPR-H [...] Read more.

Ce- and Y-promoted double-layered hydroxides were synthesized and tested in dry reforming of methane (CH₄/CO₂ = 1/1). The characterization of the catalysts was performed using X-ray fluorescence (XRF), X-ray diffraction (XRD), N₂ sorption, temperature-programmed reduction in H₂ (TPR-H₂), temperature-programmed desorption of CO₂ (TPD-CO₂), H₂ chemisorption, thermogravimetric analysis coupled by mass spectrometry (TGA/MS), Raman, and high-resolution transmission electron microscopy (HRTEM). The promotion with cerium influences textural properties, improves the Ni dispersion, decreases the number of total basic sites, and increases the reduction temperature of nickel species. After promotion with yttrium, the increase in basicity is not directly correlated with the increasing Y loading on the contrary of Ni dispersion. Dry reforming of methane (DRM) was performed as a function of temperature and in isothermal conditions at 700 °C for 5 h. For catalytic tests, a slight increase of the activity is observed for both Y and Ce doped catalysts. This improvement can of course be explained by Ni dispersion, which was found higher for both Y and Ce promoted catalysts. During DRM, the H₂/CO ratio was found below unity, which can be explained by side reactions occurrence. These side reactions are linked with the increase of CO₂ conversion and led to carbon deposition. By HRTEM, only multi-walled and helical-shaped carbon nanotubes were identified on Y and Ce promoted catalysts. Finally, from Raman spectroscopy, it was found that on Y and Ce promoted catalysts, the formed C is less graphitic as compared to only Ce-based catalyst. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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14 pages, 1863 KiB

Open AccessArticle

Carbon-Black-Supported Ru Catalysts for the Valorization of Cellulose through Hydrolytic Hydrogenation

by Maria Dolores Adsuar-García, Jhony Xavier Flores-Lasluisa, Fatima Zahra Azar and M. Carmen Román-Martínez

Catalysts 2018, 8(12), 572; https://doi.org/10.3390/catal8120572 - 22 Nov 2018

Cited by 21 | Viewed by 4113

Abstract

The one-pot hydrolytic hydrogenation of cellulose (HHC) with heterogeneous catalysts is an interesting method for the synthesis of fuels and chemicals from a renewable resource like lignocellulosic biomass. Supported metal catalysts are interesting for this application because they can contain the required active [...] Read more.

The one-pot hydrolytic hydrogenation of cellulose (HHC) with heterogeneous catalysts is an interesting method for the synthesis of fuels and chemicals from a renewable resource like lignocellulosic biomass. Supported metal catalysts are interesting for this application because they can contain the required active sites for the two catalytic steps of the HHC reaction (hydrolysis and hydrogenation). In this work, Ru catalysts have been prepared using a commercial carbon black that has been modified by sulfonation and oxidation treatments with H₂SO₄ and (NH₄)S₂O₈, respectively, in order to create acidic surface sites. The correlation between the catalysts’ properties and catalytic activity has been addressed after detailed catalyst characterization. The prepared catalysts are active for cellulose conversion, being that prepared with the carbon black treated with sulfuric acid the most selective to sorbitol (above 40%). This good behavior can be mainly explained by the suitable porous structure and surface chemistry of the carbon support together with the low content of residual chlorine. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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17 pages, 3270 KiB

Open AccessArticle

Photo-Induced Charge Separation vs. Degradation of a BODIPY-Based Photosensitizer Assessed by TDDFT and RASPT2

by Karl Michael Ziems, Stefanie Gräfe and Stephan Kupfer

Catalysts 2018, 8(11), 520; https://doi.org/10.3390/catal8110520 - 5 Nov 2018

Cited by 13 | Viewed by 5943

Abstract

A meso-mesityl-2,6-iodine substituted boron dipyrromethene (BODIPY) dye is investigated using a suite of computational methods addressing its functionality as photosensitizer, i.e., in the scope of light-driven hydrogen evolution in a two-component approach. Earlier reports on the performance of the present iodinated BODIPY dye [...] Read more.

A meso-mesityl-2,6-iodine substituted boron dipyrromethene (BODIPY) dye is investigated using a suite of computational methods addressing its functionality as photosensitizer, i.e., in the scope of light-driven hydrogen evolution in a two-component approach. Earlier reports on the performance of the present iodinated BODIPY dye proposed a significantly improved catalytic turn-over compared to its unsubstituted parent compound based on the population of long-lived charge-separated triplet states, accessible due to an enhanced spin-orbit coupling (SOC) introduced by the iodine atoms. The present quantum chemical study aims at elucidating the mechanisms of both the higher catalytic performance and the degradation pathways. Time-dependent density functional theory (TDDFT) and multi-state restricted active space perturbation theory through second-order (MS-RASPT2) simulations allowed identifying excited-state channels correlated to iodine dissociation. No evidence for an improved catalytic activity via enhanced SOCs among the low-lying states could be determined. However, the computational analysis reveals that the activation of the dye proceeds via pathways of the (prior chemically) singly-reduced species, featuring a pronounced stabilization of charge-separated species, while low barriers for carbon-iodine bond breaking determine the photostability of the BODIPY dye. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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16 pages, 5672 KiB

Open AccessArticle

Effect of Ce Doping of a Co/Al₂O₃ Catalyst on Hydrogen Production via Propane Steam Reforming

by Jeong Yeon Do, Rama Krishna Chava, Namgyu Son, Junyeong Kim, No-Kuk Park, Doyeon Lee, Myung Won Seo, Ho-Jung Ryu, Jun Hwa Chi and Misook Kang

Catalysts 2018, 8(10), 413; https://doi.org/10.3390/catal8100413 - 25 Sep 2018

Cited by 13 | Viewed by 4972

Abstract

We synthesized cerium-doped cobalt-alumina (Co_xCe_y/Al₂O₃) catalysts for the propane steam reforming (PSR) reaction. Adding cerium introduces oxygen vacancies, and the oxygen transfer capacity of the Ce promoter favors CO to CO₂ conversion during PSR, [...] Read more.

We synthesized cerium-doped cobalt-alumina (Co_xCe_y/Al₂O₃) catalysts for the propane steam reforming (PSR) reaction. Adding cerium introduces oxygen vacancies, and the oxygen transfer capacity of the Ce promoter favors CO to CO₂ conversion during PSR, inhibiting coke deposition and promoting hydrogen production. The best PSR activity was achieved at 700 °C using the Co_0.85Ce_0.15/Al₂O₃ catalyst, which showed 100% propane (C₃H₈) conversion and about 75% H₂ selectivity, and 6% CO, 5% CO₂, and 4% CH₄ were obtained. In contrast, the H₂ selectivity of the base catalyst, Co/Al₂O₃, is 64%. The origin of the difference in activity was the lower C₃H₈ gas desorption temperature of the Co_0.85Ce_0.15/Al₂O₃ catalyst compared to that of the Co/Al₂O₃ catalyst; thus, the PSR occurred at low temperatures. Furthermore, more CO was adsorbed on the Co_0.85Ce_0.15/Al₂O₃ catalyst, and subsequently, desorbed as CO₂. The activation energy for water desorption from the Co_0.85Ce_0.15/Al₂O₃ catalyst was 266.96 kJ/mol, higher than that from Co/Al₂O₃. Furthermore, the water introduced during the reaction probably reacted with CO on the Co_0.85Ce_0.15/Al₂O₃ catalyst, increasing CO₂ generation. Finally, we propose a mechanism involving the Co_0.85Ce_0.15/Al₂O₃ catalyst, wherein propane is reformed on Co_xCe_y sites, forming H_2, and CO, followed by the conversion of CO to CO₂ by water on CeO₂ sites. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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12 pages, 1523 KiB

Open AccessArticle

Hydrogen Production from Chemical Looping Steam Reforming of Ethanol over Perovskite-Type Oxygen Carriers with Bimetallic Co and Ni B-Site Substitution

by Lin Li, Bo Jiang, Zhehao Sun, Qian Zhang, Duyu Li and Dawei Tang

Catalysts 2018, 8(9), 372; https://doi.org/10.3390/catal8090372 - 4 Sep 2018

Cited by 11 | Viewed by 3824

Abstract

This paper describes the synthesis of a series of La_1.4Sr_0.6Ni_1−xCo_xO₄ perovskite OCs using co-precipitation method by employing Co and Ni as the B-site components of perovskite and the synergetic effect of Co doping [...] Read more.

This paper describes the synthesis of a series of La_1.4Sr_0.6Ni_1−xCo_xO₄ perovskite OCs using co-precipitation method by employing Co and Ni as the B-site components of perovskite and the synergetic effect of Co doping on chemical looping reforming of ethanol. A variety of techniques including N₂ adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and H₂ temperature-programmed reduction (TPR) were employed to investigate the physicochemical properties of the fresh and used OCs. The activity and stability in chemical looping reforming were studied in a fixed bed reactor at 600 °C and a S/C ratio of three. The synergetic effect between Ni and Co was able to enhance the catalytic activity and improve the stability of perovskite OCs. La_1.4Sr_0.6Ni_0.6Co_0.4O₄ showed an average ethanol conversion of 92.4% and an average CO₂/CO ratio of 5.4 in a 30-cycle stability test. Significantly, the H₂ yield and purity reached 11 wt.% and 73%, respectively. The Co doping was able to significantly improve the self-regeneration capability due to the increase in the number of oxygen vacancies in the perovskite lattice, thereby enhancing the sintering resistance. Moreover, Co promotion also contributes to the improved WGS activity. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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35 pages, 8152 KiB

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The Role of Alkali and Alkaline Earth Metals in the CO₂ Methanation Reaction and the Combined Capture and Methanation of CO₂

by Anastasios I. Tsiotsias, Nikolaos D. Charisiou, Ioannis V. Yentekakis and Maria A. Goula

Catalysts 2020, 10(7), 812; https://doi.org/10.3390/catal10070812 - 21 Jul 2020

Cited by 105 | Viewed by 12757

Abstract

CO₂ methanation has great potential for the better utilization of existing carbon resources via the transformation of spent carbon (CO₂) to synthetic natural gas (CH₄). Alkali and alkaline earth metals can serve both as promoters for methanation catalysts [...] Read more.

CO₂ methanation has great potential for the better utilization of existing carbon resources via the transformation of spent carbon (CO₂) to synthetic natural gas (CH₄). Alkali and alkaline earth metals can serve both as promoters for methanation catalysts and as adsorbent phases upon the combined capture and methanation of CO₂. Their promotion effect during methanation of carbon dioxide mainly relies on their ability to generate new basic sites on the surface of metal oxide supports that favour CO₂ chemisorption and activation. However, suppression of methanation activity can also occur under certain conditions. Regarding the combined CO₂ capture and methanation process, the development of novel dual-function materials (DFMs) that incorporate both adsorption and methanation functions has opened a new pathway towards the utilization of carbon dioxide emitted from point sources. The sorption and catalytically active phases on these types of materials are crucial parameters influencing their performance and stability and thus, great efforts have been undertaken for their optimization. In this review, we present some of the most recent works on the development of alkali and alkaline earth metal promoted CO₂ methanation catalysts, as well as DFMs for the combined capture and methanation of CO₂. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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32 pages, 10541 KiB

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Nickel Phosphide Electrocatalysts for Hydrogen Evolution Reaction

by Cun Hu, Chao Lv, Shuai Liu, Yan Shi, Jiangfeng Song, Zhi Zhang, Jinguang Cai and Akira Watanabe

Catalysts 2020, 10(2), 188; https://doi.org/10.3390/catal10020188 - 5 Feb 2020

Cited by 67 | Viewed by 12934

Abstract

The production of hydrogen through electrochemical water splitting driven by clean energy becomes a sustainable route for utilization of hydrogen energy, while an efficient hydrogen evolution reaction (HER) electrocatalyst is required to achieve a high energy conversion efficiency. Nickel phosphides have been widely [...] Read more.

The production of hydrogen through electrochemical water splitting driven by clean energy becomes a sustainable route for utilization of hydrogen energy, while an efficient hydrogen evolution reaction (HER) electrocatalyst is required to achieve a high energy conversion efficiency. Nickel phosphides have been widely explored for electrocatalytic HER due to their unique electronic properties, efficient electrocatalytic performance, and a superior anti-corrosion feature. However, the HER activities of nickel phosphide electrocatalysts are still low for practical applications in electrolyzers, and further studies are necessary. Therefore, at the current stage, a specific comprehensive review is necessary to focus on the progresses of the nickel phosphide electrocatalysts. This review focuses on the developments of preparation approaches of nickel phosphides for HER, including a mechanism of HER, properties of nickel phosphides, and preparation and electrocatalytic HER performances of nickel phosphides. The progresses of the preparation and HER activities of the nickel phosphide electrocatalysts are mainly discussed by classification of the preparation method. The comparative surveys of their HER activities are made in terms of experimental metrics of overpotential at a certain current density and Tafel slope together with the preparation method. The remaining challenges and perspectives of the future development of nickel phosphide electrocatalysts for HER are also proposed. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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30 pages, 2792 KiB

Open AccessReview

Perovskites in the Energy Grid and CO₂ Conversion: Current Context and Future Directions

by Ahmad Tabish, Anish Mathai Varghese, Md A. Wahab and Georgios N. Karanikolos

Catalysts 2020, 10(1), 95; https://doi.org/10.3390/catal10010095 - 9 Jan 2020

Cited by 32 | Viewed by 7501

Abstract

CO₂ emissions from the consumption of fossil fuels are continuously increasing, thus impacting Earth’s climate. In this context, intensive research efforts are being dedicated to develop materials that can effectively reduce CO₂ levels in the atmosphere and convert CO₂ into [...] Read more.

CO₂ emissions from the consumption of fossil fuels are continuously increasing, thus impacting Earth’s climate. In this context, intensive research efforts are being dedicated to develop materials that can effectively reduce CO₂ levels in the atmosphere and convert CO₂ into value-added chemicals and fuels, thus contributing to sustainable energy and meeting the increase in energy demand. The development of clean energy by conversion technologies is of high priority to circumvent these challenges. Among the various methods that include photoelectrochemical, high-temperature conversion, electrocatalytic, biocatalytic, and organocatalytic reactions, photocatalytic CO₂ reduction has received great attention because of its potential to efficiently reduce the level of CO₂ in the atmosphere by converting it into fuels and value-added chemicals. Among the reported CO₂ conversion catalysts, perovskite oxides catalyze redox reactions and exhibit high catalytic activity, stability, long charge diffusion lengths, compositional flexibility, and tunable band gap and band edge. This review focuses on recent advances and future prospects in the design and performance of perovskites for CO₂ conversion, particularly emphasizing on the structure of the catalysts, defect engineering and interface tuning at the nanoscale, and conversion technologies and rational approaches for enhancing CO₂ transformation to value-added chemicals and chemical feedstocks. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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