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12 pages, 2573 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Improving the Stability of Ru-Doped Ni-Based Catalysts for Steam Methane Reforming during Daily Startup and Shutdown Operation

by Tae-Young Kim, Jong-Heon Lee, Seongbin Jo, Jueon Kim, Jin-Hyeok Woo, Ragupathy Dhanusuraman, Jae-Chang Kim and Soo-Chool Lee

Catalysts 2023, 13(6), 949; https://doi.org/10.3390/catal13060949 - 30 May 2023

Cited by 8 | Viewed by 2304

Abstract

In this study, a Ru-doped Ni pellet-type catalyst was prepared to produce hydrogen via steam methane reforming (SMR). A small amount of Ru addition on the Ni catalyst improved Ni dispersion, thus affording a higher catalytic activity than that of the Ni catalyst. During the daily startup and shutdown (DSS) operations, the CH₄ conversion of Ni catalysts significantly decreased because of Ni metal oxidation to NiAl₂O₄, which is not reduced completely at 700 °C. Conversely, the oxidized Ni species in the Ru–Ni catalyst can be reduced under SMR conditions because of H₂ spillover from the surface of Ru onto the surface of Ni. Consequently, the addition of a small quantity of Ru to the Ni catalyst can improve the catalytic activity and stability during the DSS operation. Full article

(This article belongs to the Special Issue Advances in Reforming Catalysts for Hydrogen Production)

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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 3 | Viewed by 2223

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 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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29 pages, 11709 KiB

Open AccessArticle

Catalytic Tar Conversion in Two Different Hot Syngas Cleaning Systems

by Grazyna Straczewski, Robert Mai, Uta Gerhards, Krassimir Garbev and Hans Leibold

Catalysts 2021, 11(10), 1231; https://doi.org/10.3390/catal11101231 - 13 Oct 2021

Cited by 4 | Viewed by 3984

Abstract

Tar in the product gas of biomass gasifiers reduces the efficiency of gasification processes and causes fouling of system components and pipework. Therefore, an efficient tar conversion in the product gas is a key step of effective and reliable syngas production. One of the most promising approaches is the catalytic decomposition of the tar species combined with hot syngas cleaning. The catalyst must be able to convert tar components in the synthesis gas at temperatures of around 700 °C downstream of the gasifier without preheating. A Ni-based doped catalyst with high activity in tar conversion was developed and characterized in detail. An appropriate composition of transition metals was applied to minimize catalyst coking. Precious metals (Pt, Pd, Rh, or a combination of two of them) were added to the catalyst in small quantities. Depending on the hot gas cleaning system used, both transition metals and precious metals were co-impregnated on pellets or on a ceramic filter material. In the case of a pelletized-type catalyst, the hot gas cleaning system revealed a conversion above 80% for 70 and 110 h. The catalyst composed of Ni, Fe, and Cr oxides, promoted with Pt and impregnated on a ceramic fiber filter composed of Al₂O₃(44%)/SiO₂(56%), was the most active catalyst for a compact cleaning system. This catalyst was catalytically active with a naphthalene conversion of around 93% over 95 h without catalyst deactivation. Full article

(This article belongs to the Special Issue Catalysts in Production of Clean Gasification Gas)

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12 pages, 3720 KiB

Open AccessArticle

Combustion Synthesis during Flame Spraying (“CAFSY”) for the Production of Catalysts on Substrates

by Galina Xanthopoulou, Amalia Marinou, Konstantinos Karanasios and George Vekinis

Coatings 2017, 7(1), 14; https://doi.org/10.3390/coatings7010014 - 20 Jan 2017

Cited by 6 | Viewed by 5835

Abstract

Combustion-assisted flame spraying (“CAFSY”) has been used to produce catalytically active nickel aluminide coatings on ceramic substrates. Their catalytic activity was studied in CO₂ (dry) reforming of methane, which is particularly significant for environmental protection as well as production of synthesis gas (CO + H₂). By varying the CAFSY processing parameters, it is possible to obtain a range of Ni–Al alloys with various ratios of catalytically active phases on the substrate. The influence of the number of coating layers and the type of substrate on the final catalyst composition and on the catalytic activity of the CAFSY coatings was studied and is presented here. The morphology and microstructure of the composite coatings were determined by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) elemental analysis, X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) specific area analysis. Catalytic tests for dry reforming of methane were carried out using crushed pellets from the coatings at temperatures of 750–900 °C, and gas chromatography showed that methane conversion approached 88% whereas that of carbon dioxide reached 100%. The H₂/CO ratio in the synthesis gas produced by the reaction varied from about 0.7 to over 1.2, depending on the catalyst and substrate type and testing temperature. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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