Article
Chemistry, Applied
Weifeng Chu, Xiaona Liu, Zhiqiang Yang, Hiroya Nakata, Xingzhi Tan, Xuebin Liu, Longya Xu, Peng Guo, Xiujie Li, Xiangxue Zhu
Summary: By conducting Rietveld refinement against powder X-ray diffraction data, this study unraveled the constrained Al crystallographic sites in FER-type zeolites, revealing distinct local environments and Al-rich positions, which can explain the limited catalytic activity in certain reactions.
CHINESE JOURNAL OF CATALYSIS
(2021)
Article
Engineering, Environmental
Dequan Fan, Shuchao Jiang, Kai Qiao, Shengzhong Zhang, Hongtao Wang, Dechen Bo, Ying Zhang, Tie Yu, Dong Zhai, Guoqing Ren, Hao Yang, Kumar Marella Ravi
Summary: In this study, the impact of acidity on copper species distribution and CO storage performance during solid exchange process was evaluated. The results showed that NaY-Cu samples had superior CO storage ability compared to NaY supports, and the CO adsorption behaviors over hydroxyls, Na+ cations, and Cu+/Cu2+ cations were further examined to reveal the adsorption sites. The relation between faujasite acidity and CuCl distribution was systematically concluded to illustrate their industrial application potential.
CHEMICAL ENGINEERING JOURNAL
(2022)
Article
Chemistry, Multidisciplinary
Xinyu Li, He Han, Wenqian Xu, Son-Jong Hwang, Peng Lu, Aditya Bhan, Michael Tsapatsis
Summary: This study investigated the mild dealumination of Faujasite (FAU) zeolites under moderate ion exchange conditions and the effects of changes in accessible and active protons on propane reactions. The ratio of protons in sodalite cages can be manipulated by adjusting ammonium concentrations in ion exchange, impacting the dehydrogenation and cracking rates of propane. This study reveals the significance of proton accessibility and reactivity in sodalite cages on catalytic reactions.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Physical
Peng Liu, Jingjing Zhang, Shaozhong Peng, Wei Liu, Donghai Mei
Summary: The hydrocracking process of aromatic rings in the petrochemical industry has been studied using density functional theory. It is found that the Lewis acid site composed of a single extraframework-Al3+ atom is the most stable mononuclear extraframework aluminum species. Molecular dynamics simulations show that this site is the most efficient catalytic center for hydrogen splitting, leading to the formation of the stable tetrahydroanthracen-1-ylium cation. The reactivity of the hydrogen splitting process on different catalytic centers is influenced by the local electric field generated by the hydride acceptor and proton acceptor within the frustrated Lewis pair sites.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Chemistry, Multidisciplinary
Jeffery L. White, Kuizhi Chen, Anya Zornes, Vy Nguyen, Bin Wang, Zhehong Gan, Steven P. Crossley
Summary: This study reveals the presence of at least two types of paired active sites in zeolite catalysts through NMR experiments, and finds that these paired sites play a crucial role in reactivity. Additionally, it is observed that synthetic and postsynthetic modifications affect the quantity and arrangement of these paired sites.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Materials Science, Multidisciplinary
A. Martucci, N. Precisvalle, E. Fois, M. Ardit, G. Beltrami, L. Pasti, M. Cescon, E. Suard, G. Tabacchi
Summary: The concentration and location of Bronsted acid sites (BASs) in deuterated L-zeolite were determined using neutron powder diffraction and ab-initio molecular dynamics modelling. Two Bronsted acid sites, D1 and D2, were identified, with D2 showing a large degree of mobility and D1 showing static disorder. The study also found that the O1 BAS had a higher Bronsted base character compared to the average basicity of the framework oxygens of the 12-membered ring channels.
MATERIALS CHEMISTRY AND PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Zhiping Xiong, Guodong Qi, Ensheng Zhan, Yueying Chu, Jun Xu, Jiake Wei, Na Ta, Aijing Hao, Yan Zhou, Feng Deng, Wenjie Shen
Summary: Mordenite is an effective catalyst for the carbonylation of dimethyl ether to methyl acetate, and the activity is determined by the number of Bronsted acid sites in its 8-member-ring pore. Experimental evidence shows that the specific activity of the T3 site is 4 times higher than that of the T4 site at 473 K. This study provides insights into the unique reaction mechanism at the T3 site.
Article
Chemistry, Physical
Do Trung Hieu, Hendrik Kosslick, Muhammad Riaz, Axel Schulz, Armin Springer, Marcus Frank, Christian Jaeger, Nguyen Thi Minh Thu, Le Thanh Son
Summary: This study prepared acidic HCLIN catalysts by ion exchange and calcination using natural zeolite clinoptilolite as a starting material. The catalysts showed good catalytic performance in the etherification of glycerol.
Article
Biochemistry & Molecular Biology
Abderrazek El-Kordy, Abdelaziz Elgamouz, El Mokhtar Lemdek, Najib Tijani, Salman S. Alharthi, Abdel-Nasser Kawde, Ihsan Shehadi
Summary: This study describes the deposition of sodalite and faujasite zeolite films on clay supports from the central region of Morocco to tune the mesopores. The 160-250μm support showed the highest water flux and the zeolite films exhibited well crystallized structures. Filtration tests showed that size exclusion was the predominant mechanism for the retention of methyl orange.
Article
Materials Science, Ceramics
Lisandro Simao, Andreia De Rossi, Dachamir Hotza, Manuel J. Ribeiro, Rui M. Novais, Oscar R. Klegues Montedo, Fabiano Raupp-Pereira
Summary: In this research, variations in compositional and processing parameters were explored to produce zeolites-containing geopolymers from biomass fly ash wastes. The mixture composition used in the synthesis plays a crucial role in determining the nature of zeolitic crystalline phases in the geopolymeric matrix. Different NaOH concentrations resulted in varying surface areas of faujasite-type zeolites in the geopolymers.
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
(2021)
Article
Chemistry, Inorganic & Nuclear
Esmat Koohsaryan, Mansoor Anbia, Kourosh Tabar Heydar
Summary: In this study, highly crystalline hierarchical FAU zeolite was prepared and activated by MoO3 for oxidative desulfurization of fuel oils. Various characterization techniques were employed to identify the structural properties of the catalyst and the mechanism of the ODS process. The results showed that Meso-Mo-FAU with 19 wt.% molybdenum exhibited high catalytic activity at 70 degrees C, and the spent catalyst had a robust heterogeneous nature.
JOURNAL OF SOLID STATE CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Manoj Ravi, Vitaly L. Sushkevich, Jeroen A. van Bokhoven
Summary: The Lewis acidic aluminum in zeolites can be transformed into octahedrally coordinated aluminum, which serves as the precursor of Lewis acid sites. These Lewis acid sites preferentially locate in the pore structure of mordenite, particularly in the side-pockets. By reverting the octahedrally coordinated aluminum back to a tetrahedral geometry, the corresponding Bronsted acid sites are restored, showing a reversible switch between Lewis and Bronsted acidity.
Article
Chemistry, Physical
Daiqiang Li, Lian Wang, Yuqin Lu, Hua Deng, Zhilin Zhang, Yingjie Wang, Ying Ma, Tingting Pan, Qian Zhao, Yulong Shan, Xiaoyan Shi, Jinzhu Ma, Hong He
Summary: In this study, regulation of active sites in zeolites with different Si/Al ratios was used to achieve Pt/Beta catalysts with different valence states, locations, and dispersion of Pt for toluene oxidation. The Pt/Beta catalysts with high silica showed better catalytic oxidation performance than those with low silica, due to the stronger activation ability towards O2 and more facile oxygen replenishment of Pt0. Moreover, Pt0 was found to be more conducive to the benzene ring opening reaction.
APPLIED CATALYSIS B-ENVIRONMENTAL
(2023)
Article
Chemistry, Physical
Omar Abed, Hend Omar Mohamed, Idoia Hita, Vijay Velisoju, Natalia Morlanes, Omar El Tall, Pedro Castano
Summary: This study compares the effects of different catalyst structures on adsorption and catalysis, exploring the roles of pore topology, Ni sites, and acid sites. The results show that acid sites are particularly important during the initial stages of the reaction, and using a continuous reactor alone may lead to misinterpretation. Ni accelerates the reaction and improves the selectivity towards oligomers. Based on the experimental results, the dominant mechanisms over the different catalyst sites and reaction times are discussed.
Article
Chemistry, Physical
Fei Han, Han Sun, Zhenchao Zhao, Yaxin Xu, Hong Dong, Weiwei Liu, Lu Sun, Zhili Wang, Guangjin Hou, Masaaki Kitano, Wei Li, Meiqing Shen, Haijun Chen
Summary: In this study, an environmentally friendly deNO(x) method using methanol as a reductant and pure H-FER zeolite as the catalyst was proposed. The metal-free zeolite showed nearly 4 times higher activity compared to commonly used precious metal catalysts. It exhibited comparable deNO(x) efficiency with state-of-the-art NH3-SCR on vanadium-based catalysts, along with good stability and potential for industrial application.
Article
Chemistry, Physical
Vera Bikbaeva, Nikolay Nesterenko, Stanislav Konnov, Thanh-Son Nguyen, Jean-Pierre Gilson, Valentin Valtchev
Summary: This study presents a new catalyst based on supported molybdenum-carbide phase for the oxidative dehydrogenation of ethane with CO2. The catalyst achieves a conversion rate of 66% for ethane and a yield of 58% for ethylene. The techno-economic study shows that this catalyst can significantly reduce CO2 emissions in ethylene production, with lower energy demand and a simpler product slate.
APPLIED CATALYSIS B-ENVIRONMENTAL
(2023)
Article
Chemistry, Physical
Eddy Dib, Svetlana Mintova, Georgi N. Vayssilov, Hristiyan A. Aleksandrov, Marina Carravetta
Summary: By using a combination of symmetry-based recoupling in 29Si NMR, spin dynamics-based simulations, and DFT-based theoretical calculations, we demonstrate how to characterize the 29Si NMR peaks of (Si-O-Si), Bronsted acid sites (Si-OH-Al), and silanols (Si-OH) in nanosized ZSM-5 zeolites. Theoretical calculations and experimental observations reveal significant differences in the chemical shift anisotropy for silicon nuclei close to aluminum (Q(4)(1Al)) compared to those which are not, allowing for clear assignment of Si-29 NMR peaks. The isotropic chemical shift alone cannot differentiate these differences.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Chemistry, Physical
Nikola L. Drenchev, Elena Z. Ivanova, Mihail Y. Mihaylov, Hristiyan A. Aleksandrov, Georgi N. Vayssilov, Konstantin I. Hadjiivanov
Summary: To design efficient CO2 capture materials, it is important to ensure a high adsorption capacity. We have recently discovered that one Na+ site in NaY zeolite can attach two CO2 molecules, but the process occurs at a low temperature and is not suitable for practical use. We have now found that one Ca2+ site in CaNaY zeolite can attach three CO2 molecules, making it a promising material for CO2 capture.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Yaozu Liu, Jingwei Li, Jia Lv, Zitao Wang, Jinquan Suo, Junxia Ren, Jianchuan Liu, Dong Liu, Yujie Wang, Valentin Valtchev, Shilun Qiu, Daliang Zhang, Qianrong Fang
Summary: Although isomerism is rare in covalent organic framework (COF) materials, this study achieved controllable synthesis of topological isomers in three-dimensional COFs for the first time. Different solvents were used to obtain two isomers, JUC-620 and JUC-621, with distinct porous features. JUC-621 with a qtz net showed larger mesopores and higher surface area compared to JUC-620 with a dia net, and it exhibited efficient dye removal and excellent iodine adsorption.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Edwin B. Clatworthy, Simona Moldovan, Kalthoum Nakouri, Stoyan P. Gramatikov, Francesco Dalena, Marco Daturi, Petko St. Petkov, Georgi N. Vayssilov, Svetlana Mintova
Summary: This study directly visualizes the structural flexibility of a high-aluminum nano-sized RHO zeolite using in situ TEM for the first time. Variable temperature experiments observe the physical expansion of nanocrystals in response to changes in guest-molecule chemistry and temperature. Operando FTIR spectroscopy complements the observations and verifies the nature of adsorbed CO2 and structural changes at high temperatures. Quantum chemical modeling substantiates the effect of cation mobility and CO2 on the flexibility behavior of the structure. The results demonstrate the combined influences of temperature and CO2 on the structural flexibility consistent with experimental observations.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Ayoub Daouli, Jerome Rey, El Hassane Lahrar, Valentin Valtchev, Michael Badawi, Remy Guillet-Nicolas
Summary: The study systematically screened divalent cation exchanged chabazite zeolites using theoretical calculations and simulations, focusing on the adsorption selectivity of CO2/CH4, N-2/CH4, and N-2/H-2. The results showed that Mg-CHA exhibited the best selective adsorption performance for CO2, while Ca(II) was found to be favorable for the selective adsorption of H-2 and CO2.
Article
Chemistry, Applied
Peng Peng, Simona Moldovan, Aurelie Vicente, Valerie Ruaux, Maxime Debost, Han Hu, Hristiyan A. Aleksandrov, Georgi N. Vayssilov, Zi-Feng Yan, Svetlana Mintova
Summary: Nanosized MFI type zeolites were synthesized using Cu-containing complexes. The use of EDTA as a ligand promoted solubility and ensured exclusive configuration of copper-bearing chelate. EDTA-assisted MFI zeolite nanocrystals (Cu-MFIEDTA) had low silanol content due to flexible Si-O-Cu bonds. NH3 as a ligand resulted in extra framework [Cu delta+,,,O delta- ,,,Cu delta+]n clusters in the corresponding sample (Cu-MFI-NH3).
MICROPOROUS AND MESOPOROUS MATERIALS
(2023)
Article
Chemistry, Physical
Jiali Li, Ji Jia, Jinquan Suo, Cuiyan Li, Zhiwei Wang, Hui Li, Valentin Valtchev, Shilun Qiu, Xiaoming Liu, Qianrong Fang
Summary: Researchers have developed metal- and pyrolysis-free COFs with high ORR activity by incorporating precise heteroatoms, and JUC-616 shows the best performance in terms of half-wave potential and TOF.
JOURNAL OF MATERIALS CHEMISTRY A
(2023)
Article
Chemistry, Inorganic & Nuclear
Mohammad Fahda, Louwanda Lakiss, Kamila Goldyn, Edwin Clatworthy, Marie Desmurs, Jean-Pierre Gilson, Svetlana Mintova, Valentin Valtchev
Summary: Non-chemical post-synthetic approach using constant pressure can shrink zeolite crystals, enhancing their catalytic activity by improving molecular diffusion.
INORGANIC CHEMISTRY FRONTIERS
(2023)
Article
Chemistry, Physical
Iskra Z. Koleva, Hristiyan A. Aleksandrov, Georgi N. Vayssilov
Summary: The mechanism of CO oxidation on platinum species supported on ceria or alumina was investigated using periodic density functional calculations. Various reaction paths involving different oxidation states of monoatomic species-Pt0, Pt2+, and Pt4+-as well as platinum clusters were modeled to understand the nature of the catalytically active species. The activation barriers of the reaction paths involving complexes of Pt2+ and Pt4+ cations were found to be the lowest, ranging from 22 to 35 kJ/mol. The calculations also revealed that the activation energies for platinum clusters with high CO coverage supported on ceria were low, while those on gamma-alumina or involving preadsorbed oxygen on the platinum cluster were significantly higher, ranging from 90 to 120 kJ/mol. The role of the oxidant in the reaction paths was discriminated, indicating that the activation barriers are low when the oxidants are platinum species and notably higher when the oxidants are Ce4+ cations.
Article
Chemistry, Physical
Nikola L. Drenchev, Elena Z. Ivanova, Mihail Y. Mihaylov, Hristiyan A. Aleksandrov, Georgi N. Vayssilov, Konstantin I. Hadjiivanov
Summary: In order to design efficient CO2 capture materials, a high adsorption capacity is necessary. It has been found that one Na+ site in NaY zeolite can attach two CO2 molecules, while one Ca2+ site in CaNaY zeolite can attach three CO2 molecules. The results show that CaY zeolites can be very effective CO2 capture materials, with the potential for practical use.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
