Article
Chemistry, Multidisciplinary
Jing Xiong, Zhenguo Li, Peng Zhang, Qi Yu, Kaixiang Li, Yilin Zhang, Zhen Zhao, Jian Liu, Jianmei Li, Yuechang Wei
Summary: The 3DOM-Pt@MnOx/Al2O3 catalysts prepared by the GBMR/P method show high catalytic activities for soot combustion, with the optimized Pt-MnOx interface catalyst exhibiting the highest activity. These catalysts have the potential for practical applications in reducing soot particle emissions.
CHINESE CHEMICAL LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Mauro E. Silva, Maira O. Palm, Diego A. . Duarte, Rafael C. Catapan
Summary: Here, the synthesis of Pt/Al2O3 catalysts on a monolithic foam using the competitive impregnation method is described. NO3- was employed as a competitive adsorbate to delay Pt adsorption and minimize Pt concentration gradients. Various characterization techniques were applied to evaluate the catalysts, including BET, H2-pulse titration, SEM, XRD, and XPS. The catalytic activity of the samples was assessed in partial oxidation and autothermal reforming of ethanol. The competitive impregnation method led to better dispersion of Pt particles and showed promising results in synthesizing well dispersed Pt catalysts over alpha-Al2O3 foams.
Article
Chemistry, Multidisciplinary
Mengmeng Sun, Shuo Zhou, Suning Wang, Chang Song
Summary: This study systematically investigated the differences between Pt/SiO2-Al2O3 catalysts prepared by the traditional impregnation method and the strong electrostatic adsorption process. It was found that the catalyst prepared through the strong electrostatic adsorption process had smaller Pt particle size, better dispersion, and better catalytic activity and thermal stability.
Article
Engineering, Environmental
Rajat Subhra Ghosh, Pritpal Singh Dhillon, Michael P. Harold, D. Wang
Summary: This study presents a comprehensive investigation of NH3 oxidation on Pt/Al2O3 through experimental kinetics and modeling, revealing the significant enhancement of Pt/Al2O3 activity by milling and its effect on the light-off temperature. The dependence of reaction rate on NH3 concentration and processing method is discussed, highlighting the importance of understanding the reaction mechanism for optimizing catalytic performance.
CHEMICAL ENGINEERING JOURNAL
(2021)
Article
Chemistry, Physical
Elena M. Slavinskaya, Lidiya S. Kibis, Olga A. Stonkus, Dmitry A. Svintsitskiy, Andrei I. Stadnichenko, Elizaveta A. Fedorova, Anatolii V. Romanenko, Vasyl Marchuk, Dmitry E. Doronkin, Andrei I. Boronin
Summary: The dependence of NH3 oxidation on the state and dispersion of Pt species in Pt/γ-Al2O3 catalysts was investigated. Prereduced Pt/γ-Al2O3 catalysts with Pt-0 nanoparticles exhibited significantly higher activity, with the most significant improvement observed when Pt-0 particle size increased. Introduction of H2O and CO2 moderately influenced NH3 oxidation activity.
Article
Nanoscience & Nanotechnology
Shuaiqi Zhao, Jiajin Lin, Peng Wu, Changchun Ye, Yifei Li, Anqi Li, Xiaojing Jin, Yun Zhao, Guangxu Chen, Yongcai Qiu, Daiqi Ye
Summary: The study presents a single-atom Pt-HEO/Al2O3 catalyst achieved through a sol-gel-assisted mechanical milling strategy, where the strong interaction between HEO and Al2O3 effectively inhibits the growth of HEO microparticles, while another strong interaction between Pt and HEO stabilizes single-atom Pt on HEO. This catalyst shows superior stability against hydrothermal aging and long-term reaction stability for CO catalytic oxidation, exceeding 540 hours, opening up new possibilities for practical applications.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Chemistry, Physical
Emily Cheng, Justin Notestein
Summary: Potassium-promoted, alumina-supported molybdenum oxide is investigated for non-oxidative isobutane dehydrogenation, with an emphasis on sub-monolayer coverages. The study shows that sub-monolayer metal oxides may warrant further investigation as light alkane dehydrogenation, given their stable dehydrogenation activity.
JOURNAL OF CATALYSIS
(2021)
Article
Chemistry, Physical
Yonglong Li, Senyou Yang, Honggen Peng, Wenming Liu, Yangyang Mi, Zheng Wang, Changjin Tang, Daishe Wu, Taicheng An
Summary: In this study, Co-doped MnFeOx ternary mixed oxides with hierarchically ordered structure exhibited enhanced low-temperature activity, broadened temperature window, improved water resistance, and enhanced SO2 and soot tolerance for NH3-SCR of NOx. The enhanced performance was attributed to the presence of active oxygen species, higher content of Mn4+, Fe3+, and Co3+, and improved surface acidity, which facilitated the adsorption and activation of NO and NH3, making it a promising candidate for low-temperature deNOx application.
JOURNAL OF CATALYSIS
(2021)
Article
Engineering, Environmental
Peiyuan Liang, Lina Wang, Qi Wang, Baogang Zhao, Yunhe Li, Yanming Ma, Yi Wei, Tianjun Sun
Summary: Al-Ti oxides supported noble-metal catalysts were prepared through mechanical ball-milling method and incipient wetness impregnation method, in which the etching of Al-Ti mixed oxides by phosphoric acid enhanced the propane oxidation performance. The phosphate-modified Pd/Al2O3-TiO2 catalyst with an Al/P ratio of 3:1 exhibited high catalytic activity, achieving over 90% conversion of C3H8 at 380 degrees C and GHSV of 100000 h-1, with the addition of 5 vol% H2O and 10 vol% CO2. The incorporation of Al2O3 and TiO2 provided a high specific surface area and excellent pore structure, while the phosphate modification enhanced the interaction between Pd species and the support, leading to better dispersion and catalytic stability. The presence of brilliant redox ability and abundant surface oxygen species in phosphate-modified Pd/Al2O3-TiO2 catalysts contributed to the activation of O2 and increased catalytic activity.
JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING
(2023)
Article
Chemistry, Physical
Ali Cherif, Rachid Nebbali, John William Sheffield, Nimeti Doner, Fatih Sen
Summary: This study presents a numerical analysis of hydrogen production via an autothermal reforming reactor activated with patterned catalytic layers. The novel design aims to improve hydrogen yield, shorten the activated zone length, and reduce oxygen consumption. The new design results in lower costs and a more compact process.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Energy & Fuels
Maria U. Alzueta, Victor D. Mercader, Jorge Gimenez-Lopez, Rafael Bilbao
Summary: The impact of using CO2 or N2/Ar as bath gas on ammonia oxidation has been evaluated through combined experimental and simulation study. Operating conditions such as temperature and oxygen stoichiometry were carefully controlled. The presence of NO, formed from ammonia oxidation, was also investigated. The results have significant implications for the power and energy industry, particularly in guiding the co-firing of NH3 and carbon containing fuels.
Article
Chemistry, Multidisciplinary
Yilin Zhang, Peng Zhang, Jing Xiong, Yuanfeng Li, Yaxiao Ma, Sicheng Zhang, Zhen Zhao, Jian Liu, Yuechang Wei
Summary: In this article, highly dispersed Pt nanoparticles supported on Ni1.5Co0.5AlO nanosheets derived from hydrotalcite were fabricated using the gas-bubble-assisted membrane-reduction method. The specific porous structure of the Ni1.5Co0.5AlO nanosheets enhanced mass transfer efficiency and the interaction between Pt and Ni1.5Co0.5AlO promoted the mobility of lattice oxygen and the formation of surface-oxygen vacancies. The Pt-n/Ni1.5Co0.5AlO catalysts exhibited excellent catalytic activity and stability in diesel soot combustion, with the Pt-2/Ni1.5Co0.5AlO catalyst showing the highest activity. The synergistic effect of Pt and dual Ni/Co cations in the catalysts promoted the oxidation of NO to NO2 and provided new strategies for reducing the use of noble metals in high-efficient catalysts.
Article
Energy & Fuels
Maria U. Alzueta, Jorge Gimenez-Lopez, Victor D. Mercader, Rafael Bilbao
Summary: This study investigates the oxidation of ammonia and ammonia-nitric oxide mixtures in a CO2 atmosphere from both experimental and kinetic modelling perspectives. The influence of temperature, stoichiometry, gas residence time, and NH3/NO ratio on the reaction is evaluated through parametric studies. Experimental results are interpreted using a literature reaction mechanism.
Article
Environmental Sciences
Nawel Jraba, Thabet Makhlouf, Gerard Delahay, Hassib Tounsi
Summary: The study involves the preparation and characterization of copper-loaded eta-alumina catalysts with different copper contents for catalytic reactions. Experimental results indicate that the impregnation/evaporation method is beneficial for highly dispersed copper oxide species on the surface at low copper contents. Wet impregnation allows for a well dispersion of copper species on the alumina surface for low copper contents, leading to similar catalytic performance in the selective catalytic oxidation of NH3.
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
(2022)
Article
Environmental Sciences
Minh Thang Le, Sharanjit Singh, Minh Nguyen-Quang, Anh Binh Ngo, Angelika Bruckner, Udo Armbruster
Summary: The study found that the loading of ceria has a significant impact on the reduction of NOx, with catalysts with low and high loading showing different activities under different temperature conditions. The results indicate that a too high loading of ceria can lead to a decrease in catalyst activity.
SCIENCE OF THE TOTAL ENVIRONMENT
(2021)
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
Chemistry, Physical
Junya Ohyama, Yuka Tsuchimura, Hiroshi Yoshida, Masato Machida, Shun Nishimura, Keisuke Takahashi
Summary: The catalytic performance of Cu-CHA catalysts for partial CH4 oxidation was improved through refinement of catalyst composition using the Bayesian optimization method. Experimental validation showed that optimization of Cu-ion exchange rates (Cu IERs) and Si/Al2 ratios was achieved in only two cycles of the Bayesian optimization process.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Multidisciplinary
Taiki Hirakawa, Yuma Miyahara, Yushi Shimokawa, Koshi Nishiyama, Masayuki Tsushida, Hiroshi Yoshida, Junya Ohyama, Masato Machida
Summary: In this research, various quaternary metal catalysts were investigated for the replacement of precious metals in three-way catalysts. The CrFeNiCu system demonstrated the best catalytic performance, achieving a lower light-off temperature for CO, C3H6, and NO compared to a reference catalyst. Structural analysis revealed that the catalyst underwent structural changes during the catalytic reaction. The presence of Cr oxide significantly enhanced CO/C3H6 oxidation and promoted the regeneration of the active NiCu metallic surface for NO reduction.
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)
