Research

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12 pages, 4322 KiB

Open AccessFeature PaperArticle

Egg-Shell-Type MgAl₂O₄ Pellet Catalyst for Steam Methane Reforming Reaction Activity: Effect of Pellet Preparation Temperature

by Yeon Jeong Yu, Eunkyung Cho and Chang Hyun Ko

Catalysts 2022, 12(12), 1500; https://doi.org/10.3390/catal12121500 - 23 Nov 2022

Cited by 2 | Viewed by 1262

Abstract

A pellet catalyst was prepared to be used in a large-scale steam methane reformer. Hydrotalcite powder (MG30) was used as a precursor to prepare MgAl₂O₄ pellet supports at different calcination temperatures. Ni-supported catalysts with egg-shell-type distribution were prepared on these [...] Read more.

A pellet catalyst was prepared to be used in a large-scale steam methane reformer. Hydrotalcite powder (MG30) was used as a precursor to prepare MgAl₂O₄ pellet supports at different calcination temperatures. Ni-supported catalysts with egg-shell-type distribution were prepared on these pellet supports: Ni/sup-x (where x is the calcination temperature of the support with x = 1273, 1373, and 1473 K). Among them, Ni/sup-1473, which experienced the highest calcination temperature (1473 K), showed the highest methane conversion and lowest weight loss owing to carbon deposition. As a result, when the calcination temperature increased, the egg-shell thickness decreased, and the reducibility of the catalyst was enhanced. Although a small amount of Ni (3.5 wt%) was used, the egg-shell-type catalyst had superior catalytic activity and coke resistance. Therefore, the egg-shell-type catalyst using Ni as the active material and MgAl₂O₄ calcined at high temperature as the support is expected to be appropriate for large-scale industrial steam methane reforming reactions. Full article

(This article belongs to the Special Issue Catalysis on Stable Molecules (CO₂, CO, CH₄, N₂, NH₃) Activation and Their Transformation)

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20 pages, 4011 KiB

Open AccessArticle

A Systematic Approach to Study Complex Ternary Co-Promoter Interactions: Addition of Ir, Li, and Ti to RhMn/SiO₂ for Syngas Conversion to Ethanol

by Mohammad Khatamirad, Martin Konrad, Manuel Gentzen, Chiara Boscagli, Christian Almer, Aleks Arinchtein, Michael Geske, Frank Rosowski and Ralph Kraehnert

Catalysts 2022, 12(11), 1321; https://doi.org/10.3390/catal12111321 - 27 Oct 2022

Cited by 1 | Viewed by 1247

Abstract

The direct conversion of synthesis gas could open up economically viable routes for the efficient production of ethanol. RhMn/SiO₂ represents one of the most active systems reported thus far. Potential improvements were reported by added dopants, i.e., Ir, Ti, and Li. Yet, [...] Read more.

The direct conversion of synthesis gas could open up economically viable routes for the efficient production of ethanol. RhMn/SiO₂ represents one of the most active systems reported thus far. Potential improvements were reported by added dopants, i.e., Ir, Ti, and Li. Yet, combining these elements leads to contradicting results, owing to the complexity of the interactions in a multi-promoted system. This complexity is often encountered in heterogeneous catalysis. We report a systematic data-driven approach for the assessment of complex multi-promoter interactions based on a combination of design-of-experiment, high-throughput experimentation, statistical analysis, and mechanistic assessment. We illustrate this approach for the system RhMn/SiO₂ promoted with Ir, Li, and Ti. Using this approach, we investigate the impact of promoters’ interactions on a mechanistic level. Our analysis depicts the means to learn hidden correlations in the performance data and, additionally, high performance for ethanol yield for the RhMnIr/SiO₂ catalyst. The method presented outlines an efficient way to also elucidate co-promoter interactions in other complex environments. Full article

(This article belongs to the Special Issue Catalysis on Stable Molecules (CO₂, CO, CH₄, N₂, NH₃) Activation and Their Transformation)

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13 pages, 3253 KiB

Open AccessFeature PaperArticle

Effects of Cu Species on Liquid-Phase Partial Oxidation of Methane with H₂O₂ over Cu-Fe/ZSM-5 Catalysts

by Min Sik Kim, Gun Sik Yang and Eun Duck Park

Catalysts 2022, 12(10), 1224; https://doi.org/10.3390/catal12101224 - 13 Oct 2022

Cited by 4 | Viewed by 1559

Abstract

In this study, a Cu-promoted Fe/ZSM-5 catalyst was examined to reveal the effects of Cu species in selective oxidation of methane into methane oxygenates using H₂O₂ in water. Cu/ZSM-5, Cu-Fe/ZSM-5, and Fe/ZSM-5 catalysts were prepared using wet impregnation, solid-state ion [...] Read more.

In this study, a Cu-promoted Fe/ZSM-5 catalyst was examined to reveal the effects of Cu species in selective oxidation of methane into methane oxygenates using H₂O₂ in water. Cu/ZSM-5, Cu-Fe/ZSM-5, and Fe/ZSM-5 catalysts were prepared using wet impregnation, solid-state ion exchange, and ion-exchange methods. Various techniques, including nitrogen physisorption, temperature-programmed reduction with H₂, UV-vis spectroscopy, and FT-IR spectroscopy after NO adsorption, were utilized to characterize the catalysts. The promotional effect of Cu on the Cu-Fe/ZSM-5 catalyst in terms of methanol selectivity was confirmed. The preparation method has a considerable influence on the catalyst performance, and the ion-exchange method is the most effective. However, leaching of the Cu species was observed during this reaction, which can affect the quantification of formic acid by ¹H-NMR. The homogeneous Cu species increase hydrogen peroxide decomposition and CO₂ selectivity, which is undesirable for this reaction. Full article

(This article belongs to the Special Issue Catalysis on Stable Molecules (CO₂, CO, CH₄, N₂, NH₃) Activation and Their Transformation)

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10 pages, 1727 KiB

Open AccessFeature PaperArticle

Ammonia Decomposition over Ru/SiO₂ Catalysts

by Ho Jin Lee and Eun Duck Park

Catalysts 2022, 12(10), 1203; https://doi.org/10.3390/catal12101203 - 09 Oct 2022

Cited by 9 | Viewed by 5180

Abstract

Ammonia decomposition is a key step in hydrogen production and is considered a promising practical intercontinental hydrogen carrier. In this study, 1 wt.% Ru/SiO₂ catalysts were prepared via wet impregnation and subjected to calcination in air at different temperatures to control the [...] Read more.

Ammonia decomposition is a key step in hydrogen production and is considered a promising practical intercontinental hydrogen carrier. In this study, 1 wt.% Ru/SiO₂ catalysts were prepared via wet impregnation and subjected to calcination in air at different temperatures to control the particle size of Ru. Furthermore, silica supports with different surface areas were prepared after calcination at different temperatures and utilized to support a change in the Ru particle size distribution of Ru/SiO₂. N₂ physisorption and transmission electron microscopy were used to probe the textural properties and Ru particle size distribution of the catalysts, respectively. These results show that the Ru/SiO₂ catalyst with a high-surface area achieved the highest ammonia conversion among catalysts at 400 °C. Notably, this is closely related to the Ru particle sizes ranging between 5 and 6 nm, which supports the notion that ammonia decomposition is a structure-sensitive reaction. Full article

(This article belongs to the Special Issue Catalysis on Stable Molecules (CO₂, CO, CH₄, N₂, NH₃) Activation and Their Transformation)

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21 pages, 4347 KiB

Open AccessArticle

On the Optimization of Ni/A and Ni/X Synthesis Procedure toward Active and Selective Catalysts for the Production of CH₄ from CO₂

by Somkiat Krachuamram, Pinit Kidkhunthod, Yingyot Poo-arporn, Nuntaporn Kamonsutthipaijit and Kingkaew Chayakul Chanapattharapol

Catalysts 2022, 12(8), 823; https://doi.org/10.3390/catal12080823 - 26 Jul 2022

Cited by 2 | Viewed by 1325

Abstract

Herein, optimization of zeolite NaA/NaX synthesis conditions in order to obtain the final product with high surface area and pore volume was investigated. An optimal synthesis condition was 5 days aging time and crystallization time of 9 h with the co-addition of cetyltrimethylammonium [...] Read more.

Herein, optimization of zeolite NaA/NaX synthesis conditions in order to obtain the final product with high surface area and pore volume was investigated. An optimal synthesis condition was 5 days aging time and crystallization time of 9 h with the co-addition of cetyltrimethylammonium bromide (CTAB) and heptane. All those optimal synthesis conditions provided mixed phase between zeolite NaA and NaX, and addition of those organic phases improved the surface area and pore volume of the final synthesized zeolite. The role of CTAB and heptane on increasing the surface area of zeolite was studied by in situ small-angle X-ray scattering (SAXS). The SAXS results evidenced that small nucleation precursor was formed upon the addition of organic phase, and this nucleation precursor can provide zeolite with high-characteristic XRD signals of mixed phase of zeolite A and X after the crystallization process. The synthesized zeolite obtained from optimal synthesis condition with high surface area was further used as a catalyst support by impregnating with 5, 10, 15, and 20wt%Ni for catalyzing CO₂ methanation reaction. The results found that 15wt%Ni/zeolite expressed the highest catalytic activity with high CH₄ selectivity and stability. This was due to high dispersion of Ni species on catalyst surface and high metal-support interaction between Ni and zeolite. These results indicated that the mixed phase zeolite support can be a potential catalyst support for this reaction. Full article

(This article belongs to the Special Issue Catalysis on Stable Molecules (CO₂, CO, CH₄, N₂, NH₃) Activation and Their Transformation)

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14 pages, 4020 KiB

Open AccessFeature PaperArticle

CO and CO₂ Methanation over CeO₂-Supported Cobalt Catalysts

by Thuy Ha Nguyen, Han Bom Kim and Eun Duck Park

Catalysts 2022, 12(2), 212; https://doi.org/10.3390/catal12020212 - 11 Feb 2022

Cited by 23 | Viewed by 3861

Abstract

CO₂ methanation is a promising reaction for utilizing CO₂ using hydrogen generated by renewable energy. In this study, CO and CO₂ methanation were examined over ceria-supported cobalt catalysts with low cobalt contents. The catalysts were prepared using a wet impregnation [...] Read more.

CO₂ methanation is a promising reaction for utilizing CO₂ using hydrogen generated by renewable energy. In this study, CO and CO₂ methanation were examined over ceria-supported cobalt catalysts with low cobalt contents. The catalysts were prepared using a wet impregnation and co-precipitation method and pretreated at different temperatures. These preparation variables affected the catalytic performance as well as the physicochemical properties. These properties were characterized using various techniques including N₂ physisorption, X-ray diffraction, H₂ chemisorption, temperature-programmed reduction with H₂, and temperature-programmed desorption after CO₂ chemisorption. Among the prepared catalysts, the ceria-supported cobalt catalyst that was prepared using a wet impregnation method calcined in air at 500 °C, and reduced in H₂ at 500 °C, showed the best catalytic performance. It is closely related to the large catalytically active surface area, large surface area, and large number of basic sites. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study revealed the presence of carbonate, bicarbonate, formate, and CO on metallic cobalt. Full article

(This article belongs to the Special Issue Catalysis on Stable Molecules (CO₂, CO, CH₄, N₂, NH₃) Activation and Their Transformation)

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17 pages, 8243 KiB

Open AccessArticle

Na₂WO₄/Mn/SiO₂ Catalyst Pellets for Upgrading H₂S-Containing Biogas via the Oxidative Coupling of Methane

by Sangseo Gu, Jae-Wook Choi, Dong Jin Suh, Chun-Jae Yoo, Jungkyu Choi and Jeong-Myeong Ha

Catalysts 2021, 11(11), 1301; https://doi.org/10.3390/catal11111301 - 28 Oct 2021

Cited by 1 | Viewed by 1712

Abstract

Biogas is a promising renewable energy source; however, it needs to be upgraded to increase its low calorific value. In this study, oxidative coupling of methane (OCM) was selected to convert it to a higher fuel standard. Prior to establishing the scaled-up OCM [...] Read more.

Biogas is a promising renewable energy source; however, it needs to be upgraded to increase its low calorific value. In this study, oxidative coupling of methane (OCM) was selected to convert it to a higher fuel standard. Prior to establishing the scaled-up OCM process, the effect of organic/inorganic binders on catalytic activity was examined. The selection of the binders and composition of the catalyst pellet influenced the pore structure, fracture strength, and catalytic activity of the catalyst pellets. It was also observed that the O₂ supply from the inorganic binder is a key factor in determining catalytic activity, based on which the composition of the catalyst pellets was optimized. The higher heating value increased from 39.9 (CH₄, Wobbe index = 53.5 MJ/Nm³) to 41.0 MJ/Nm³ (OCM product mixture, Wobbe index = 54.2 MJ/Nm³), achieving the fuel standard prescribed in many countries (Wobbe index = 45.5–55.0 MJ/Nm³). The reaction parameters (temperature, gas hourly space velocity, size of the reaction system, and the CH₄/O₂ ratio) were also optimized, followed by a sensitivity analysis. Furthermore, the catalyst was stable for a long-term (100 h) operation under the optimized conditions. Full article

(This article belongs to the Special Issue Catalysis on Stable Molecules (CO₂, CO, CH₄, N₂, NH₃) Activation and Their Transformation)

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8 pages, 4077 KiB

Open AccessCommunication

Iridium(NHC)-Catalyzed Sustainable Transfer Hydrogenation of CO₂ and Inorganic Carbonates

by Yeon-Joo Cheong, Kihyuk Sung, Jin-A Kim, Yu Kwon Kim, Woojin Yoon, Hoseop Yun and Hye-Young Jang

Catalysts 2021, 11(6), 695; https://doi.org/10.3390/catal11060695 - 31 May 2021

Cited by 5 | Viewed by 2988

Abstract

Iridium(NHC)-catalyzed transfer hydrogenation (TH) of CO₂ and inorganic carbonates with glycerol were conducted, demonstrating excellent turnover numbers (TONs) and turnover frequencies (TOFs) for the formation of formate and lactate. Regardless of carbon sources, excellent TOFs of formate were observed (CO₂: [...] Read more.

Iridium(NHC)-catalyzed transfer hydrogenation (TH) of CO₂ and inorganic carbonates with glycerol were conducted, demonstrating excellent turnover numbers (TONs) and turnover frequencies (TOFs) for the formation of formate and lactate. Regardless of carbon sources, excellent TOFs of formate were observed (CO₂: 10,000 h⁻¹ and K₂CO₃: 10,150 h⁻¹). Iridium catalysts modified with the triscarbene ligand showed excellent catalytic activity at 200 °C and are a suitable choice for this transformation which requires a high temperature for high TONs of formate. On the basis of the control experiments, the transfer hydrogenation mechanism of CO₂ was proposed. Full article

(This article belongs to the Special Issue Catalysis on Stable Molecules (CO₂, CO, CH₄, N₂, NH₃) Activation and Their Transformation)

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Review

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19 pages, 2114 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Electrochemical Nitrogen Reduction Reaction to Ammonia from the Catalyst to the System

by Yong Hyun Moon, Na Yun Kim, Sung Min Kim and Youn Jeong Jang

Catalysts 2022, 12(9), 1015; https://doi.org/10.3390/catal12091015 - 07 Sep 2022

Cited by 17 | Viewed by 4579

Abstract

As energy-related issues increase significantly, interest in ammonia (NH₃) and its potential as a new eco-friendly fuel is increasing substantially. Accordingly, many studies have been conducted on electrochemical nitrogen reduction reaction (ENRR), which can produce ammonia in an environmentally friendly manner [...] Read more.

As energy-related issues increase significantly, interest in ammonia (NH₃) and its potential as a new eco-friendly fuel is increasing substantially. Accordingly, many studies have been conducted on electrochemical nitrogen reduction reaction (ENRR), which can produce ammonia in an environmentally friendly manner using nitrogen molecule (N₂) and water (H₂O) in mild conditions. However, research is still at a standstill, showing low performances in faradaic efficiency (FE) and NH₃ production rate due to the competitive reaction and insufficient three-phase boundary (TPB) of N₂(g)-catalyst(s)-H₂O(l). Therefore, this review comprehensively describes the main challenges related to the ENRR and examines the strategies of catalyst design and TPB engineering that affect performances. Finally, a direction to further develop ENRR through perspective is provided. Full article

(This article belongs to the Special Issue Catalysis on Stable Molecules (CO₂, CO, CH₄, N₂, NH₃) Activation and Their Transformation)

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29 pages, 26697 KiB

Open AccessFeature PaperReview

Gas-Phase Selective Oxidation of Methane into Methane Oxygenates

by Zhen Chao Xu and Eun Duck Park

Catalysts 2022, 12(3), 314; https://doi.org/10.3390/catal12030314 - 09 Mar 2022

Cited by 8 | Viewed by 4037

Abstract

Methane is an abundant resource and its direct conversion into value-added chemicals has been an attractive subject for its efficient utilization. This method can be more efficient than the present energy-intensive indirect conversion of methane via syngas, a mixture of CO and H [...] Read more.

Methane is an abundant resource and its direct conversion into value-added chemicals has been an attractive subject for its efficient utilization. This method can be more efficient than the present energy-intensive indirect conversion of methane via syngas, a mixture of CO and H₂. Among the various approaches for direct methane conversion, the selective oxidation of methane into methane oxygenates (e.g., methanol and formaldehyde) is particularly promising because it can proceed at low temperatures. Nevertheless, due to low product yields this method is challenging. Compared with the liquid-phase partial oxidation of methane, which frequently demands for strong oxidizing agents in protic solvents, gas-phase selective methane oxidation has some merits, such as the possibility of using oxygen as an oxidant and the ease of scale-up owing to the use of heterogeneous catalysts. Herein, we summarize recent advances in the gas-phase partial oxidation of methane into methane oxygenates, focusing mainly on its conversion into formaldehyde and methanol. Full article

(This article belongs to the Special Issue Catalysis on Stable Molecules (CO₂, CO, CH₄, N₂, NH₃) Activation and Their Transformation)

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18 pages, 3615 KiB

Open AccessFeature PaperReview

Photoelectrochemical Conversion of Methane into Value-Added Products

by Adeel Mehmood, Sang Youn Chae and Eun Duck Park

Catalysts 2021, 11(11), 1387; https://doi.org/10.3390/catal11111387 - 17 Nov 2021

Cited by 15 | Viewed by 3110

Abstract

Methane has been reported to be directly converted into value-added products through various methods. Among them, photoelectrochemical (PEC) methane conversion is considered an eco-friendly method because it utilizes solar light and is able to control the selectivity to different products by means of [...] Read more.

Methane has been reported to be directly converted into value-added products through various methods. Among them, photoelectrochemical (PEC) methane conversion is considered an eco-friendly method because it utilizes solar light and is able to control the selectivity to different products by means of application of an external bias. Recently, some PEC methane conversion systems have been reported, but their performance efficiencies are relatively lower than those of other existing thermal, photocatalytic, and electrochemical systems. The detailed mechanism of methane activation is not clear at this stage. In this review, various catalytic materials and their roles in the reaction pathways are summarized and discussed. Furthermore, promising semiconductor materials, co-catalysts, and oxidants have also been proposed. Finally, direct and indirect pathways in the design of the PEC methane conversion system have been discussed. Full article

(This article belongs to the Special Issue Catalysis on Stable Molecules (CO₂, CO, CH₄, N₂, NH₃) Activation and Their Transformation)

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