Article
Engineering, Environmental
Yuanshuang Zheng, Maya Marinova, Pascal Granger
Summary: The kinetics of the catalytic CH4/O-2 reaction on Pd/LaxMnO3 catalysts with different compositions (x = 0.7, 1.0, and 1.3) was studied. It was found that on Pd/La1.3MnO3 with a La-rich surface, a single site reaction mechanism was preferred, while on Pd-La0.7MnO3 with a Mn-rich surface, a dual-site reaction mechanism involving both Pd and surface reactive oxygen species was observed. High surface Pd/Mn ratio and high concentration of Pd-n(+) (n > 2) were identified as good indicators for the efficacy of Pd/LaxMnO3 catalysts.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Engineering, Environmental
Yanwei Sun, Guangyan Xu, Yingjie Wang, Wei Shi, Yunbo Yu, Hong He
Summary: In this study, a series of encapsulated structured catalysts with palladium nanoparticles confined in hydrophobic silicalite-2 were prepared, which showed high catalytic activity and long-term stability for methane oxidation under harsh conditions.
ENVIRONMENTAL SCIENCE & TECHNOLOGY
(2023)
Article
Green & Sustainable Science & Technology
Jia Lin, Yalan Xu, Xiaohua Chen, Jiangli Huang, Hong Xu, Ying Zheng
Summary: Different dopants (yttrium, magnesium, zinc, nickel, or tin) with varying electron affinity were incorporated into alumina-supported palladium-cobalt catalysts, resulting in the tuning of microstructure, surface property, and electronic state of catalysts. The catalytic activity showed an inverted volcano trend with increased electronegativity of dopants, with magnesium providing additional electrons to enhance the Pd-Co interaction and improve catalytic performance, stability, and water-resistance.
JOURNAL OF CLEANER PRODUCTION
(2023)
Article
Chemistry, Applied
Henry Steven Fabian Ramos, Joseph P. Mmbaga, Robert E. Hayes
Summary: This paper presents a study on catalyst configuration for lean methane combustion using computational modelling. The use of platinum group metals catalyst in a washcoated monolith is investigated, and the computational model is validated using experimental data from a small-scale pilot plant reactor. The results show that catalyst activity and reactor length are critical for system performance and stability.
Article
Chemistry, Multidisciplinary
Shengpan Peng, Ziran Ma, Jing Ma, Hongyan Wang, Jingyun Chen, Hui Wei, Yonglong Li, Zhimin Ao, Baodong Wang
Summary: The study investigates the effects of Pd/Al2O3 catalysts modified by different chemical elements (Mg, Si, Ce, and Zr) on methane catalytic combustion. It is found that tuning Pd dispersion and acidity on the catalyst's surface can alter activation energy and pre-exponential factors, thus enhancing the catalytic activity of methane.
FRONTIERS IN CHEMISTRY
(2022)
Article
Nanoscience & Nanotechnology
Meiyin Liu, Xiaomai Chen, Zikun Wang, Yanshi Zhang, Ruijie Li, Haoming Zheng, Daiqi Ye, Junliang Wu
Summary: A series of Pd catalysts encapsulated in Silicalite-1 zeolite with different nanoparticle sizes were synthesized using a one-step hydrothermal method to study the size effect on methane catalytic oxidation. The addition of ethylenediamine ligand was used to modulate the Pd nanoparticle sizes, and the Pd/S-1-in-6EN catalyst with a size of 2.1 nm exhibited remarkable catalytic performance. Long-term stability tests showed excellent water resistance for Pd/S-1-in-6EN with smaller particle size. In situ CO-DRIFTS results presented a volcano-shaped curve between the fraction of step sites controlled by Pd nanoparticle size and the catalytic performance, with Pd/S-1-in-6EN showing the optimum performance. This provides further insight into the particle size effect on zeolite-confined noble metal catalysts for methane combustion.
ACS APPLIED NANO MATERIALS
(2023)
Article
Energy & Fuels
Fen Wang, Yao Ouyang, Xiumiao Yang
Summary: This work demonstrates that adding Pt to the 1Pd/MgFe2O4 catalyst in a suitable amount (4 wt%) can greatly enhance its catalytic activity and stability. The 4Pt-1Pd/MgFe2O4 catalyst achieved high and stable methane combustion performances at 395 degrees C under a WHSV of 30,000 mL/(g-h) for 20 hours. Through comprehensive characterizations, the study reveals that the addition of Pt can decrease the size of metallic nanoparticles, increase the proportion of Pd0 and adsorbed oxygen species, leading to improved catalytic activity and stability. These findings provide guidance for designing highly active and stable Pd-based catalysts for catalytic combustion of methane.
JOURNAL OF THE ENERGY INSTITUTE
(2023)
Article
Energy & Fuels
Jie Li, Yan Zhang, Wenpo Shan, Hong He
Summary: A series of mesoporous Pd/Al2O3 and Pd/MgAl2O4 catalysts with different palladium contents (0.5, 1 and 4 wt%) were prepared and used for methane combustion. The 1Pd/MgAl2O4 (1 wt% Pd) catalyst showed highly efficient catalysis for methane combustion below 450 degrees C, with a low apparent activation energy of around 50.1 kJ/mol and good thermal stability. The superior catalytic performance of Pd/MgAl2O4 can be attributed to the strong interaction between the MgAl2O4 spinel and PdO species, which promotes species dispersion and stability. In addition, the catalytic activity of Pd/MgAl2O4 showed a volcano-shaped dependence on the size of Pd particles, indicating the importance of strong metal-support interaction.
Article
Nanoscience & Nanotechnology
Yang Wu, Wenhu Yang, Hailong Zhang, Haidi Xu, Yi Jiao, Lin Zhong, Jianli Wang, Yaoqiang Chen
Summary: This study improves the performance of Pd/Y2O3-ZrO2 catalyst by constructing silicate patches on the support surface. This modification optimizes palladium chemistry, enhances CH4 conversion, reduces surface oxygen vacancies, and inhibits hydroxyl accumulation.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Chemistry, Physical
Silva Stanchovska, Georgy Ivanov, Sonya Harizanova, Krasimir Tenchev, Ekaterina Zhecheva, Anton Naydenov, Radostina Stoyanova
Summary: The study elaborates on the deposition method, chemical state of Pd, and the oxygen storage capability of transition metal ions in Pd-supported catalysts for catalytic combustion to reduce methane emissions. Wet impregnation method shows higher catalytic activity due to well-dispersed PdO-like phase and high oxygen storage capability of transition metal ions. Reactivity likely proceeds through Mars-van Krevelen mechanism over the catalysts.
Article
Chemistry, Applied
Alessandra Palella, Lorenzo Spadaro, Roberto Di Chio, Francesco Arena
Summary: The study investigated a series of MnCeOx composite materials for methane oxidation reaction, finding that increasing the proportion of CeO2 in the catalyst can significantly enhance the activity. The most active catalyst with a Mn-to-Ce ratio of 1:3 achieved almost complete methane conversion at 600 degrees Celsius.
Article
Chemistry, Physical
An-Chih Yang, Verena Streibel, Tej S. Choksi, Hassan Aljama, Baraa Werghi, Simon R. Bare, Roel S. Sanchez-Carrera, Ansgar Schaefer, Yuejin Li, Frank Abild-Pedersen, Matteo Cargnello
Summary: Hydrocarbon combustion is crucial in emission control applications, and developing efficient catalysts optimized for noble metal use is imperative. Pt-rich catalysts were found to perform best for both propane and propene oxidation reactions. However, contrasting trends in rate orders, active phase, and stability were observed due to different rate-limiting steps and interactions between the two compounds.
JOURNAL OF CATALYSIS
(2021)
Article
Chemistry, Physical
Yahia H. Ahmad, Assem T. Mohamed, Siham Y. Al-Qaradawi
Summary: Chemical modification of halloysite nanotubes and deposition of palladium results in catalysts with enhanced catalytic performance for methane combustion, with Pd/HNTs-NaOH showing the highest activity and stability among them. The confinement of Pd nanoparticles at the inner surface of the nanotubes enhances catalyst-support interaction and increases resistance to sintering at high temperatures, leading to improved catalytic efficiency.
APPLIED CLAY SCIENCE
(2021)
Article
Engineering, Chemical
Chuan-Bin Du, Zhi Xuan Law, Ren-You Huang, De-Hao Tsai
Summary: A raspberry-structured hybrid nanocatalyst composed of NiCu bimetallic oxide nanoparticle decorated on ceria nanoparticle cluster (NiCuOx@CeO2) was successfully synthesized via a gas-phase evaporation-induced self-assembly approach. The NiCuOx@CeO2 exhibited superior catalytic performance in methane combustion and showed high stability. The addition of CuO promoted the redox ability of NiCuOx in the hybrid nanostructure.
ADVANCED POWDER TECHNOLOGY
(2022)
Article
Thermodynamics
Seokwon Cho, Hyewon Lee, Ying Lin, Satbir Singh, William F. Northrop
Summary: Pretreating natural gas using catalytic oxidative coupling of methane (OCM) can produce ethylene and ethane, increasing fuel reactivity and expanding the operational range of highly efficient compression ignition combustion in natural gas engines. This study presents experimental and computational results on the impact of OCM product species on engine thermal efficiency and operability range.
ENERGY CONVERSION AND MANAGEMENT
(2022)
Article
Chemistry, Applied
Masato Machida, Yurika Tokudome, Akihide Maeda, Tetsuya Sato, Hiroshi Yoshida, Junya Ohyama, Kenji Fujii, Naoya Ishikawa
Summary: The study investigates the effect of different transition metal overlayers on Fe-Cr-Al metal foil as catalysts for NH3 oxidation. It was found that the presence of H2O had contrasting effects on the activity of different metals, with non-precious metals showing decreased activity while Pt and Ir remained stable.
Article
Chemistry, Applied
Hiroshi Yoshida, Tomoyo Koide, Takuya Uemura, Yusuke Kuzuhara, Junya Ohyama, Masato Machida
Summary: In this study, the surface modification of a nanometric Rh overlayer by a small amount of Ce was found to enhance its three-way catalytic activity. The oxygen storage/release behavior of the surface Ce contributed to buffering the air-to-fuel change and improving the catalytic activity. The Ce-modified Rh overlayer with a metal honeycomb structure exhibited high activity even under A/F perturbation conditions at high space velocity, making it a promising and energy-saving alternative to conventional catalytic converters.
Article
Chemistry, Physical
Ayumi Fujiwara, Yutaro Tsurunari, Shundai Iwashita, Hiroshi Yoshida, Junya Ohyama, Masato Machida
Summary: In three-way catalytic converters, perturbations in exhaust gas composition between fuel-rich and fuel-lean conditions affect catalyst surface and conversion efficiencies. In this study, real-time changes in surface states of Pd-based catalysts were monitored using in situ diffuse reflectance spectroscopy. The oxidation state of Pd fluctuated in sync with the perturbations, with smaller oscillation amplitude on CeO2-ZrO2 (CZ) compared to Al2O3. CZ's oxygen scavenging function buffered oxidative degradation, resulting in higher reaction rates and preventing coke deposition. This study highlights the usefulness of in situ DRS in understanding transient catalytic processes and bridging the gap between on-board performances and laboratory tests.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Energy & Fuels
Yuka Tsuchimura, Hiroshi Yoshida, Masato Machida, Shun Nishimura, Keisuke Takahashi, Junya Ohyama
Summary: Cu-CHA exhibits high catalytic performance in the direct oxidation of CH4 to CH3OH. The catalytic activity varies with the composition of Cu-CHA. Three groups of Cu species were identified based on their catalytic performance: low Cu/Al ratio for high selectivity and low activity, medium Cu/Al ratio for high selectivity and high activity in CH3OH production, and high Cu/Al ratio for high activity in complete oxidation of CH4 to CO2. The mono-(mu-oxo) di-Cu species in Cu-CHA is proposed as the active species for the catalytic reaction.
Article
Engineering, Chemical
Shundai Iwashita, Ayumi Fujiwara, Hiroshi Yoshida, Junya Ohyama, Takeshi Miki, Masato Machida
Summary: The thermal deactivation mechanism of Pd/CeO2-ZrO2-Al2O3 three-way catalysts (TWCs) was investigated through engine-bench aging and driving tests. The results showed that high temperature and prolonged aging promoted the growth of Pd particles, leading to a decrease in catalytic activity. A sintering kinetic model was developed to predict TWC deactivation and lifetime based on the analysis of particle growth kinetics.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2023)
Article
Chemistry, Physical
Masato Machida, Hideto Yoshida, Naoto Kamiuchi, Yasuhiro Fujino, Takeshi Miki, Masaaki Haneda, Yutaro Tsurunari, Shundai Iwashita, Rion Ohta, Hiroshi Yoshida, Junya Ohyama, Masayuki Tsushida
Summary: Under dynamic SLR cycle conditions, the Rh/ZrO2-CeO2 (Rh/ZC) three-way catalyst experienced more severe deactivation compared to static conditions. The complete encapsulation of Rh particles with a ZC overlayer under dynamic SLR cycle conditions led to physical blockage and suppressed catalytic activity. This encapsulation phenomenon was not recovered by post-treatment in air at 1000 degrees C.
Article
Chemistry, Physical
Junya Ohyama, Hideto Ushijima, Takashi Yamashita, Akihiro Yamashita, Hiroshi Yoshida, Masato Machida
Summary: Improving the catalysts for hydrogen oxidation reaction (HOR) in alkaline conditions is crucial for the development of anion exchange membrane fuel cells. Previous studies have shown that Pt catalysts can be enhanced by forming coordinationally saturated surface sites and also by combining Pt with other metals. This study demonstrates the use of Pt-Ni alloy thin films as highly active structures in alkaline HOR, with improved activity compared to Pt monometal thin-film and nanoparticle catalysts.
ACS APPLIED ENERGY MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Masato Machida, Hideto Yoshida, Naoto Kamiuchi, Yasuhiro Fujino, Takeshi Miki, Masaaki Haneda, Yutaro Tsurunari, Shundai Iwashita, Rion Ohta, Hiroshi Yoshida, Junya Ohyama
Summary: This study investigates the performance of catalysts after real engine aging and finds that pre-aged catalysts can maintain better catalytic performance at high temperatures. It is found that the migration of Rh nanoparticles from the ZC surface to the Al2O3 binder interface plays a crucial role in mitigating the encapsulation of Rh nanoparticles by ZC. By using a dual-oxide support formulation, the deterioration extent of the catalyst and the oxygen storage capacity performance can be effectively improved.
ACS APPLIED NANO MATERIALS
(2023)
Review
Chemistry, Physical
Hiroshi Yoshida, Masato Machida
Summary: Although most solid catalysts have a three-dimensional structure of nanoparticles dispersed on a porous support, this structure is not optimal for all catalytic reactions. This article introduces a unique catalytic performance of a two-dimensional metal foil-supported nanometric Rh thin film, which is particularly suitable for CO-NO reaction and three-way catalytic reaction.
Article
Chemistry, Physical
Ayumi Fujiwara, Yutaro Tsurunari, Shundai Iwashita, Hiroshi Yoshida, Junya Ohyama, Masato Machida
Summary: This study investigated the redox behaviour of Rh in three-way catalysts using time-resolved in situ diffuse reflectance UV-vis spectroscopy. The results showed that the metallic fraction of Rh increased with changing air-to-fuel ratio, and the Kubelka-Munk function also increased near the stoichiometric point. This study provides insights into the oxidation state of Rh in TWC and its impact on catalytic performance.
Article
Chemistry, Physical
Fumiya Nishino, Hiroshi Yoshida, Masato Machida, Shun Nishimura, Keisuke Takahashi, Junya Ohyama
Summary: Catalysts for oxidative coupling of methane (OCM) were designed through machine learning of the property of surface oxygen species. The CO32- peak energy was chosen as the guiding parameter and important physical quantities determining the CO32- peak energy were identified through machine learning. Synthesized catalysts were found to have high catalytic performance based on their predicted compositions, and a new highly active OCM catalyst was discovered.
CATALYSIS SCIENCE & TECHNOLOGY
(2023)
Article
Chemistry, Physical
Masato Machida, Hideto Yoshida, Naoto Kamiuchi, Yasuhiro Fujino, Takeshi Miki, Masaaki Haneda, Yutaro Tsurunari, Shundai Iwashita, Rion Ohta, Hiroshi Yoshida, Junya Ohyama, Masayuki Tsushida
Summary: A Rh/ZrO2-CeO2 (Rh/ZC) three-way catalyst exhibited more severe deactivation under dynamic SLR cycle conditions compared to static conditions. The total encapsulation of Rh particles by a ZC overlayer led to physical blockage and suppressed catalytic activity. The encapsulation under a dynamic SLR cycle condition suggests the activation of ZC migration near the metal-support interface.
Article
Chemistry, Physical
Hiroki Iwai, Fumiya Nishino, Tomokazu Yamamoto, Masaki Kudo, Masayuki Tsushida, Hiroshi Yoshida, Masato Machida, Junya Ohyama
Summary: Researchers have successfully predicted and removed the background image of supported metal nanoparticles using a deep learning-based image inpainting method. The 3D reconstruction of the extracted images reveals the atomic structure and deformed shape of the nanoparticles, providing insights into their catalytic activity. This study demonstrates the importance of 3D atomic-scale analysis in understanding and designing supported metal catalysts.
Article
Chemistry, Physical
Masato Machida, Shundai Iwashita, Tetsuya Sato, Hiroshi Yoshida, Junya Ohyama, Masao Yoshioka, Shiro Miwa, Takeshi Hashishin
Summary: When Rh catalysts supported on Al2O3-based oxides are exposed to a high-temperature oxidizing environment, they lose their three-way catalytic activity due to the diffusion of Rh3+ into the support structure. The diffusion of Rh3+ is suppressed in the layered structure of hexaaluminate, which effectively blocks further penetration and preserves their reduction to active metallic Rh nanoparticles.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Materials Science, Ceramics
Alam S. M. Nur, Asuka Ikematsu, Hiroshi Yoshida, Masato Machida
Summary: Molten-state potassium metavanadate supported on mesoporous SiO2 materials is an active catalyst for SO3 decomposition, and the addition of phosphate can enhance its catalytic activity and form mixed phosphate vanadate KV2PO8.
JOURNAL OF THE CERAMIC SOCIETY OF JAPAN
(2022)
