Journal articles: 'Single zeolite catalysts'

1

Ulan, J., and R. Gronsky. "Effect of alkali cations on the microstructure and composition of iron silicate catalysts." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 268–69. http://dx.doi.org/10.1017/s0424820100153312.

Full text

Abstract:

Zeolites are shape selective catalysts widely used in industry. Selectivity arises from the fact that zeolites possess channels several angstroms in diameter which limits the size of species that can easily diffuse through. Promoted iron oxide is a highly active catalyst for the synthesis of hydrocarbons from CO and H2 (Fischer-Tropsch reaction) but researchers would like to narrow product selectivity to the C7-C10 gasoline range. Selectivity is improved by dispersing iron on zeolites and efforts are now directed at maximizing the iron distribution in the zeolite channels. One approach is to first incorporate iron directly into the zeolite framework during synthesis and then remove the iron from the zeolite framework and ideally form catalytically active iron oxide particles within the channels while still maintaining the pore structure of the zeolite. Iron silicate analogs of the zeolite ZSM-5 (FeZSM-5) have been synthesized and thermal treatments have been employed to produce a catalytic active material. The complete characterization by SEM and TEM of a series of FeZSM-5 catalysts with various Si/Fe ratios and preparation conditions has been achieved. This presentation is a continuation of that work. Three series of FeZSM-5 catalysts were synthesized, two had Si/Fe ratios of 45 with different Si/Al ratios and one had a Si/Fe ratio of 25. In each series, the synthetic conditions were modified by adding alkali metal cations (Li+, Na+ and K+) to the reaction mixture. It has been shown with ZSM-5 that the addition of alkali cations during synthesis produces large single crystals. The effect of alkali cations on the growth of zeolite analogs is interesting for several independent reasons ranging from basic studies of the mechanism of zeolite growth to practical experimental considerations. Single crystals are very desirable for electron microscopy studies: results are unambiguous for a single crystallite in one orientation compared to a region with many overlapping small particles.

APA, Harvard, Vancouver, ISO, and other styles

2

Abreu, Norberto J., Héctor Valdés, Claudio A. Zaror, Tatianne Ferreira de Oliveira, Federico Azzolina-Jury, and Frédéric Thibault-Starzyk. "Evidence of Synergy Effects between Zinc and Copper Oxides with Acidic Sites on Natural Zeolite during Photocatalytic Oxidation of Ethylene Using Operando DRIFTS Studies." Catalysts 13, no. 3 (2023): 610. http://dx.doi.org/10.3390/catal13030610.

Full text

Abstract:

In this article, the role of surface sites of modified zeolites with semiconductor nanoparticles as alternative photocatalyts for protecting post-harvest foodstuff from the detrimental effects of ethylene is addressed. Two single and one double catalyst based on zinc and copper oxides supported over modified zeolite samples were prepared. Physical, chemical, and surface properties of prepared materials were studied by several characterization methods. UV-Vis absorption spectra show that the applied modification procedures increase the optical absorption of light in the UV and visible regions, suggesting that an increase in the photocatalytic activity could take place mainly in the obtained co-impregnated catalyst. An ethylene conversion around 50% was achieved when the parent natural zeolite support was modified with both transition metal oxides, obtaining higher removal efficiency in comparison to single oxide catalysts. Adsorption and photocatalytic oxidation experiments were also performed using single and double catalysts supported over fumed silica, attaining lower ethylene conversion and thus highlighting the role of zeolite surfaces as adsorption sites for ethylene during photocatalytic reactions. Operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies reveal that a synergistic mechanism occurs, involving ethylene adsorption at acidic sites of zeolite and its photocatalytic oxidation due to the generation of radicals by the light activation of nanoparticles of zinc and copper oxides.

APA, Harvard, Vancouver, ISO, and other styles

3

CHRISTENSEN, C., K. JOHANNSEN, E. TORNQVIST, I. SCHMIDT, H. TOPSOE, and C. CHRISTENSEN. "Mesoporous zeolite single crystal catalysts: Diffusion and catalysis in hierarchical zeolites." Catalysis Today 128, no. 3-4 (2007): 117–22. http://dx.doi.org/10.1016/j.cattod.2007.06.082.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Takezoe, S., Kazuyuki Hosoi, Masahiko Tajika, Yuki Yamasaki, and Atsushi Nakahira. "Syntheses of Bulky Y-Zeolite by Hydrothermal Hot-Pressing (HHP) Technique." Key Engineering Materials 317-318 (August 2006): 97–100. http://dx.doi.org/10.4028/www.scientific.net/kem.317-318.97.

Full text

Abstract:

Synthesis of bulky Y-zeolite was attempted by a hydrothermal hot-pressing (HHP) method. These bulky products synthesized under hydrothermal conditions were identified as Y-zeolite single phase. Especially, bulky Y-zeolite having translucency, high density and large surface area was obtained by HHP treatment at 423K for 2h with 17wt% of 5M-NaOH solution. This solidified zeolite like single-crystal was considered to be made by dissolution and precipitation mechanism. High-density bulky zeolites can be expected as novel molecular sieves and catalysts with high activity.

APA, Harvard, Vancouver, ISO, and other styles

5

Singh, Bhupendra Kumar, Yongseok Kim, Seungdon Kwon, and Kyungsu Na. "Synthesis of Mesoporous Zeolites and Their Opportunities in Heterogeneous Catalysis." Catalysts 11, no. 12 (2021): 1541. http://dx.doi.org/10.3390/catal11121541.

Full text

Abstract:

Currently, zeolites are one of the most important classes of heterogeneous catalysts in chemical industries owing to their unique structural characteristics such as molecular-scale size/shape-selectivity, heterogenized single catalytic sites in the framework, and excellent stability in harsh industrial processes. However, the microporous structure of conventional zeolite materials limits their applications to small-molecule reactions. To alleviate this problem, mesoporous zeolitic frameworks were developed. In the last few decades, several methods have been developed for the synthesis of mesoporous zeolites; these zeolites have demonstrated greater lifetime and better performance than their bulk microporous counterparts in many catalytic processes, which can be explained by the rapid diffusion of reactant species into the zeolite framework and facile accessibility to bulky molecules through the mesopores. Mesoporous zeolites provide versatile opportunities not only in conventional chemical industries but also in emerging catalysis fields. This review presents many state-of-the-art mesoporous zeolites, discusses various strategies for their synthesis, and details their contributions to catalytic reactions including catalytic cracking, isomerization, alkylation and acylation, alternative fuel synthesis via methanol-to-hydrocarbon (MTH) and Fischer–Tropsch synthesis (FTS) routes, and different fine-chemical syntheses.

APA, Harvard, Vancouver, ISO, and other styles

6

Li, Yixiao, Quanhua Wang, Ding Wang, and Xiaoliang Yan. "NO-CH4-SCR Over Core-Shell MnH-Zeolite Composites." Applied Sciences 9, no. 9 (2019): 1773. http://dx.doi.org/10.3390/app9091773.

Full text

Abstract:

Selective catalytic reduction of NO with methane (NO-CH4-SCR) in the presence of excess oxygen was investigated over the synthesized MnH-ZZs-n zeolite composite catalysts with FAU (as core) and BEA (as shell) topologies. XRD, SEM, and NH3-TPD technologies were employed to characterize the catalysts. It is found that the topological structure of the zeolite affected the catalytic properties and H2O/SO2 tolerances considerably. MnH-ZZs-n catalysts exhibited much higher NO-CH4-SCR activity than the physical mixture catalysts with comparable relative mass content of Y and Beta zeolites, particularly the ratio of Y and Beta at the range of 0.2–0.5 than the MnH-Beta catalysts with single topology. NH3-TPD results showed that one new type of strong acidic sites formed in H-ZZs-n and remained in MnH-ZZs-n resulted from the interaction between the Lewis and Brönsted acid sites under a particular environment. The special zeolite-zeolite structure with ion-exchanged Mn ions in the core-shell zeolite composite catalysts contributed to the novel NO-CH4-SCR properties.

APA, Harvard, Vancouver, ISO, and other styles

7

Crozier, P. A., and M. Pan. "Quantitative nano-characterization of heterogeneous catalysts." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 398–99. http://dx.doi.org/10.1017/s0424820100138361.

Full text

Abstract:

Heterogeneous catalysts can be of varying complexity ranging from single or double phase systems to complicated mixtures of metals and oxides with additives to help promote chemical reactions, extend the life of the catalysts, prevent poisoning etc. Although catalysis occurs on the surface of most systems, detailed descriptions of the microstructure and chemistry of catalysts can be helpful for developing an understanding of the mechanism by which a catalyst facilitates a reaction. Recent years have seen continued development and improvement of various TEM, STEM and AEM techniques for yielding information on the structure and chemistry of catalysts on the nanometer scale. Here we review some quantitative approaches to catalyst characterization that have resulted from new developments in instrumentation.HREM has been used to examine structural features of catalysts often by employing profile imaging techniques to study atomic details on the surface. Digital recording techniques employing slow-scan CCD cameras have facilitated the use of low-dose imaging in zeolite structure analysis and electron crystallography. Fig. la shows a low-dose image from SSZ-33 zeolite revealing the presence of a stacking fault.

APA, Harvard, Vancouver, ISO, and other styles

8

N., K. DAS, and PRAMANIK KRISHNA. "Side-chain Alkylation of Toluene with Methanol over Single Zeolite Catalysts." Journal of Indian Chemical Society Vol. 74, Sep 1997 (1997): 701–4. https://doi.org/10.5281/zenodo.5895768.

Full text

Abstract:

Department of Chemical Technology. University Colleges of Science & Technology, Calcutta University, 92 A P C Road, Calcutta-700 009 Manuscript received 5 January 1996, revised 28 June 1996, accepted 25 September 1996 The side-chain alkylation of toluene with methanol has been studied over a number of prospective zeolite catalysts, such as Na-X, Cs-X and Cs-B-X at atmospheric pressure in a fixed-bed reactor. Cs-X zeolite showed a higher activity than Cs-B-X and Na-X zeolites with respect to toluene conversion and yield of styrene. The effects or reaction temperature and molecular ratios of reactants have been investigated. The maximum toluene conversion of 25.5% and styrene to ethylbenzene mole ratio of 4 : 1 are obtained with Cs-X zeolite. The catalysts show good stability as found with time-on-stream studies.

APA, Harvard, Vancouver, ISO, and other styles

9

Korchak, V. N., A. M. Kuli-zade, O. N. Silchenkova, and O. V. Udalova. "Oxidation of benzene to phenol by nitrous oxide over Me-ZSM-5-zeolites with a low concentration of active sites. Role of single active sites." Himičeskaâ fizika 43, no. 4 (2024): 18–28. http://dx.doi.org/10.31857/s0207401x24040038.

Full text

Abstract:

The ZSM-5 zeolites with Si/Al ratio 50 and 80 (ZSM-5-50 и ZSM-5-80) modified by Ca-, Sr-, Cr-, Mn- и Sb-ions were synthesized and investigated in oxidation of benzene to phenol. It was shown that more active and selective in direct oxidation of benzene by nitrous oxide are catalysts containing about 0.1–0.2% of Sb. It formally corresponds to substitution of 1/12 and 1/6 ions of H-ions by Sb-ions in ratio 1 : 1 of zeolite. Yield of phenol equal to 61.2% was obtained at 450°C and contact time 1 sec. with selectivity to phenol 96% in the presence of (ZSM-5-50 + 1/12 Sb) sample. It is about twice as much than an average value of yield reported in literature for other Me-ZSM-5 catalysts. Also, (ZSM-5-50 + 1/6 Sb) sample revealed much higher stability than other catalysts based on ZSM-5 zeolites. A model of nitrous oxide activation over single active sites (located very distant from each other) of the catalyst is suggested. The suggested model of single site adsorption and catalysis allows explain more higher efficiency of nitrous oxide as oxidant than that of molecular oxygen in reaction of direct oxidation of benzene to phenol, especially over catalysts with a low concentration (less than 0.1%) of |Me-ions.

APA, Harvard, Vancouver, ISO, and other styles

10

Zeng, Lei, Kang Cheng, Fanfei Sun, et al. "Stable anchoring of single rhodium atoms by indium in zeolite alkane dehydrogenation catalysts." Science 383, no. 6686 (2024): 998–1004. http://dx.doi.org/10.1126/science.adk5195.

Full text

Abstract:

Maintaining the stability of single-atom catalysts in high-temperature reactions remains extremely challenging because of the migration of metal atoms under these conditions. We present a strategy for designing stable single-atom catalysts by harnessing a second metal to anchor the noble metal atom inside zeolite channels. A single-atom rhodium-indium cluster catalyst is formed inside zeolite silicalite-1 through in situ migration of indium during alkane dehydrogenation. This catalyst demonstrates exceptional stability against coke formation for 5500 hours in continuous pure propane dehydrogenation with 99% propylene selectivity and propane conversions close to the thermodynamic equilibrium value at 550°C. Our catalyst also operated stably at 600°C, offering propane conversions of >60% and propylene selectivity of >95%.

APA, Harvard, Vancouver, ISO, and other styles

11

Verdoliva, Valentina, Michele Saviano, and Stefania De Luca. "Investigation of the Acid/Basic Sites of Zeolite Trough Some Catalysed Nucleophilic Reactions." Foundations 3, no. 1 (2023): 72–81. http://dx.doi.org/10.3390/foundations3010008.

Full text

Abstract:

Zeolites, both natural and synthetic, are certainly some of the most versatile minerals for their applications. Since the 1940s, they have been used in the chemical industry as catalysts, adsorbents and ion exchanger extensively, and the development of their practical usage is expected to continue upon years. Their versatility is the result of the combination of peculiar and indispensable properties, each of which can be found in other material as a single property, but seldom all of them are found in combination. However, despite the success of their employment, the mechanisms of many important catalytic processes involving zeolites remained elusive. In particular, the comprehension of the structure–property relationships for emerging applications are highly required. In this perspective article we focus on the role of zeolites as solid acid-base catalysts. We go deeply into the structural properties of the LTA kind (Zeolite-Na A 4 Ångstrom) that was successfully employed as basic catalyst for several nucleophilic substitution reactions.

APA, Harvard, Vancouver, ISO, and other styles

12

Ye, Ke, Ying Liu, Shubin Wu, and Junping Zhuang. "Efficient catalytic liquefaction of organosolv lignin over transition metal supported on HZSM-5." BioResources 17, no. 2 (2022): 2275–95. http://dx.doi.org/10.15376/biores.17.2.2275-2295.

Full text

Abstract:

In this work, the catalytic liquefaction of eucalyptus organosolv lignin (EOL) over hydrogen type-zeolite socony mobile-five (HZSM-5) zeolite supported transition metals in an ethanol system was studied, and a cheap transition metal NiCr/HZSM-5 catalyst was prepared. Among them, nickel and chromium proved to have a good synergistic effect, which could remarkably enhance the acidity of the catalyst surface, and the catalytic effect was better than Ru-based precious metal catalysts and commercial Raney Ni catalysts. Meanwhile, the optimal reaction process of NiCr/HZSM-5 and Raney Ni catalyst for synergistic catalysis of EOL was explored. Under the optimal process conditions, the lignin liquefaction rate reached 95.9%, the monophenol yield was 8.64%, and the char content was only 2.08%. Furthermore, 1H-13C heteronuclear single quantum correlation nuclear magnetic resonance (1H-13C HSQC NMR) showed that the β-O-4, β-β, and β-5 linkages of lignin were effectively broken. Thus, a higher liquefaction rate of lignin was realized, which provided the possibility for further comprehensive utilization of lignin.

APA, Harvard, Vancouver, ISO, and other styles

13

Shen, Siqi, Yuanyuan Sun, Hao Sun, et al. "Research Progress in ZIF-8 Derived Single Atomic Catalysts for Oxygen Reduction Reaction." Catalysts 12, no. 5 (2022): 525. http://dx.doi.org/10.3390/catal12050525.

Full text

Abstract:

Transition metal (TM) single atomic catalysts (MSAC-N-C) derived from doped zeolite imidazolate frameworks (ZIF-8) are considered attractive oxygen reduction reaction (ORR) catalysts for fuel cells and metal-air batteries due to their advantages of high specific surface area, more active catalytic sites, adjustable pore size, and coordination topology features. This review provides an updated overview of the latest advances of MSAC-N-C catalysts derived from ZIF-8 precursors in ORR electrocatalysis. Particularly, some key challenges, including coordination environments regulation of catalysis center in MSAC-N-C, the active sites loading optimization and synergistic effects between TM nanoclusters/nanoparticles and the single atoms on MSAC-N-C catalysis activity, as well as their adaptability in various devices, are summarized for improving future development and application of MSAC-N-C catalysts. In addition, this review puts forward future research directions, making it play a better role in ORR catalysis for fuel cells and metal air batteries.

APA, Harvard, Vancouver, ISO, and other styles

14

Kustova, Marina Yu, Peter Hasselriis, and Claus Hviid Christensen. "Mesoporous MEL – Type Zeolite Single Crystal Catalysts." Catalysis Letters 96, no. 3/4 (2004): 205–11. http://dx.doi.org/10.1023/b:catl.0000030122.37779.f4.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Dzwigaj, Stanislaw, and Michel Che. "Toward redox framework single site zeolite catalysts." Catalysis Today 169, no. 1 (2011): 232–41. http://dx.doi.org/10.1016/j.cattod.2011.01.035.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Dyer, Andrew C., Mohamad A. Nahil, and Paul T. Williams. "Biomass:polystyrene co-pyrolysis coupled with metal-modified zeolite catalysis for liquid fuel and chemical production." Journal of Material Cycles and Waste Management 24, no. 2 (2022): 477–90. http://dx.doi.org/10.1007/s10163-021-01334-0.

Full text

Abstract:

AbstractBiomass and waste polystyrene plastic (ratio 1:1) were co-pyrolysed followed by catalysis in a two-stage fixed bed reactor system to produce upgraded bio-oils for production of liquid fuel and aromatic chemicals. The catalysts investigated were ZSM-5 impregnated with different metals, Ga, Co, Cu, Fe and Ni to determine their influence on bio-oil upgrading. The results showed that the different added metals had a different impact on the yield and composition of the product oils and gases. Deoxygenation of the bio-oils was mainly via formation of CO2 and CO via decarboxylation and decarbonylation with the Ni–ZSM-5 and Co–ZSM-5 catalysts whereas higher water yield and lower CO2 and CO was obtained with the ZSM-5, Ga–ZSM-5, Cu–ZSM-5 and Fe–ZSM-5 catalysts suggesting hydrodeoxygenation was dominant. Compared to the unmodified ZSM-5, the yield of single-ring aromatic compounds in the product oil was increased for the Co–ZSM-5, Cu–ZSM-5, Fe–ZSM-5 and Ni–ZSM-5 catalysts. However, for the Ga–ZSM-5 catalyst, single-ring aromatic compounds were reduced, but the highest yield of polycyclic aromatic hydrocarbons was produced. A higher biomass to polystyrene ratio (4:1) resulted in a markedly lower oil yield with a consequent increased yield of gas.

APA, Harvard, Vancouver, ISO, and other styles

17

Cheng, Kang, Luc C. J. Smulders, Lars I. van der Wal, et al. "Maximizing noble metal utilization in solid catalysts by control of nanoparticle location." Science 377, no. 6602 (2022): 204–8. http://dx.doi.org/10.1126/science.abn8289.

Full text

Abstract:

Maximizing the utilization of noble metals is crucial for applications such as catalysis. We found that the minimum loading of platinum for optimal performance in the hydroconversion of n -alkanes for industrially relevant bifunctional catalysts could be reduced by a factor of 10 or more through the rational arranging of functional sites at the nanoscale. Intentionally depositing traces of platinum nanoparticles on the alumina binder or the outer surface of zeolite crystals, instead of inside the zeolite crystals, enhanced isomer selectivity without compromising activity. Separation between platinum and zeolite acid sites preserved the metal and acid functions by limiting micropore blockage by metal clusters and enhancing access to metal sites. Reduced platinum nanoparticles were more active than platinum single atoms strongly bonded to the alumina binder.

APA, Harvard, Vancouver, ISO, and other styles

18

Fleury, Guillaume, and Maarten B. J. Roeffaers. "Resolving the Acid Site Distribution in Zn-Exchanged ZSM-5 with Stimulated Raman Scattering Microscopy." Catalysts 10, no. 11 (2020): 1331. http://dx.doi.org/10.3390/catal10111331.

Full text

Abstract:

Zeolites are widely used acid catalysts in research and in industrial processes. The catalytic performance of these materials is affected by the nature and concentration of Brønsted and Lewis acid sites. The balance between these types of active sites—and thus the activity and selectivity of the zeolite—can be altered by the introduction of metal species, e.g., by ion exchange. Although the acidic properties of zeolites are routinely characterized by bulk-scale techniques, this ensemble-averaged approach neglects the local variations in the material. Insights into the distribution of active sites at the single-particle level are thus critical to better understand the impact of post-synthetic modifications on the zeolite acidity. In this contribution, we spatially resolve Brønsted and Lewis acid sites in protonated and Zn-exchanged ZSM-5 crystals. To this end, the vibrational modes of pyridine chemisorbed on active sites are mapped with stimulated Raman scattering (SRS) microscopy. The SRS images reveal sharp inter- and intra-particle heterogeneities in the distribution of Lewis acid sites introduced upon ion exchange, ascribed to local variations in the Al content. Besides assessing the impact of Zn exchange on the active site distribution in ZSM-5 crystals, this approach enables uniquely to map the distribution of Lewis acid sites in catalysts at the single-particle level.

APA, Harvard, Vancouver, ISO, and other styles

19

Grundner, S., W. Luo, M. Sanchez-Sanchez, and J. A. Lercher. "Synthesis of single-site copper catalysts for methane partial oxidation." Chemical Communications 52, no. 12 (2016): 2553–56. http://dx.doi.org/10.1039/c5cc08371k.

Full text

Abstract:

Synthesis conditions direct the speciation of Cu2+ in Cu-exchanged mordenite zeolite towards active [Cu3(μ-O)3]2+ species for methane oxidation to methanol.

APA, Harvard, Vancouver, ISO, and other styles

20

Mohammed, Mohammed Taha, Rokhsana Mohammed Ismail, and Nadrah M. Hussami. "TREATMENT OF KEROSEN FROM YEMENI – (ALIF FIELD) MARIB CRUDE OIL USING ZEOLITE CATALYST." Electronic Journal of University of Aden for Basic and Applied Sciences 5, no. 4 (2024): 543–53. https://doi.org/10.47372/ejua-ba.2024.4.411.

Full text

Abstract:

Regarding the investigation of Yemen crude Oil, we found that Marib crude oil was the best one. Based on the information we started to treat Kerosene from Marib Crude Oil using zeolite catalyst because this catalyst is the best one referring to the references. Many bifunctional catalysts in recent studies have been prepared using a single method, it is important to note that different preparation methods can have an influence on their behavior during the process and the properties of the fuels they produce. We used several methods of analysis, such as Catalyst Preparation, Method of Impregnation, Sol – gel Method, in addition we studied Catalyst characterization. The results showed that the acidic sites of Y-zeolites would be thus affecting its catalytic efficiency in reforming process. One of the main reasons for production of higher products was the concentration of Bronsted acid targets in the catalyst. In this study, the catalyst is synthesized the SG method had Bronsted acid sites, resulting in effect of this solvent on their acid sites. Although less jet fuel was produced over the catalyst produced by the IM method (75. 81%), the fuel was higher quality is allowed aromatic and high of naphthens, which were associated with less the Bronsted acid sites of this catalyst.

APA, Harvard, Vancouver, ISO, and other styles

21

Kim, Yanghwa, Ocktaeck Lim, and Hongsuk Kim. "Determination of Chemical Kinetic Parameters for Adsorption and Desorption of NH3 in Cu-Zeolite Used as a DeNOx SCR Catalyst of Diesel Engines." Catalysts 12, no. 8 (2022): 917. http://dx.doi.org/10.3390/catal12080917.

Full text

Abstract:

Ammonia-based selective catalytic reduction is one of the most effective NOx reduction technologies for diesel engines, but its low NOx reduction efficiency under low-temperature conditions needs further improvement. Previous studies have broadened our understanding of the NH3 adsorption and desorption that occurs in an SCR catalyst of Cu ion-exchanged zeolite. However, many studies conducted to data on the control of the NH3 adsorption and desorption in SCR catalysts have considered a simple chemical reaction related to a single acid site. This study demonstrates a detailed process for determining the chemical kinetic parameters of the adsorption and desorption of NH3 for different types of acid sites of a zeolite catalyst. The determined chemical kinetics parameters will be used for more effective control of the SCR system in future studies.

APA, Harvard, Vancouver, ISO, and other styles

22

Alonso, Gerard, Estefanía López, Fermín Huarte-Larrañaga, Ramón Sayós, Hector Prats, and Pablo Gamallo. "Zeolite-encapsulated single-atom catalysts for efficient CO2 conversion." Journal of CO2 Utilization 54 (December 2021): 101777. http://dx.doi.org/10.1016/j.jcou.2021.101777.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Dzwigaj, Stanislaw, and Michel Che. "ChemInform Abstract: Toward Redox Framework Single Site Zeolite Catalysts." ChemInform 42, no. 41 (2011): no. http://dx.doi.org/10.1002/chin.201141204.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Shi, Dezhi, Sen Wang, Hao Wang, et al. "Synthesis of HZSM-5 Rich in Paired Al and Its Catalytic Performance for Propane Aromatization." Catalysts 10, no. 6 (2020): 622. http://dx.doi.org/10.3390/catal10060622.

Full text

Abstract:

A series of HZSM-5 catalysts with similar Si/AlF mole ratio, textual properties and morphology, but different contents of AlF pairs, were synthesized by controlling the Na/Al molar ratios in the precursor gel and used for propane aromatization. It is shown that the catalyst with a Na/Al molar ratio of 0.8 in the synthetic gel possesses the highest paired AlF concentration (64.4%) and shows higher propane conversion (38.2%) and aromatics selectivity (19.7 wt.%). Propane pulse experiments, micro reactor activity estimation, Operando diffuse reflectance ultraviolet-visible (DR UV-vis) spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR) analysis of coke species deposited on the catalysts provide evidence that AlF pairs in the ZSM-5 framework promote oligomerization and cyclization reactions of olefins, and then produce more aromatics. Density Functional Theory (DFT) calculations demonstrate that the cyclization of olefins and hydride transfer reaction occurring on AlF pairs in HZSM-5 zeolite show a lower free energy barrier and a higher rate constant than those on single AlF, indicating that the structure of AlF pairs in the HZSM-5 zeolite has a stronger electrostatic stabilization effect on the transition states than that of single AlF.

APA, Harvard, Vancouver, ISO, and other styles

25

Xie, Qinglong, Paul Chen, Pu Peng, et al. "Single-step synthesis of DME from syngas on CuZnAl–zeolite bifunctional catalysts: the influence of zeolite type." RSC Advances 5, no. 33 (2015): 26301–7. http://dx.doi.org/10.1039/c5ra02814k.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Krishna, Siddarth H., Casey B. Jones, and Rajamani Gounder. "Dynamic Interconversion of Metal Active Site Ensembles in Zeolite Catalysis." Annual Review of Chemical and Biomolecular Engineering 12, no. 1 (2021): 115–36. http://dx.doi.org/10.1146/annurev-chembioeng-092120-010920.

Full text

Abstract:

Catalysis science is founded on understanding the structure, number, and reactivity of active sites. Kinetic models that consider active sites to be static and noninteracting entities are routinely successful in describing the behavior of heterogeneous catalysts. Yet, active site ensembles often restructure in response to their external environment and even during steady-state catalytic turnover, sometimes requiring non-mean-field kinetic treatments to describe distance-dependent interactions among sites. Such behavior is being recognized more frequently in modern catalysis research, with the advent of experimental methods to quantify turnover rates with increasing precision, an expanding arsenal of operando characterization tools, and computational descriptions of atomic structure and motion at chemical potentials and timescales increasingly relevant to reaction conditions. This review focuses on dynamic changes to metal active site ensembles on zeolite supports, which are silica-based crystalline materials substituted with Al that generate binding sites for isolated and low-nuclearity metal site ensembles. Metal sites can become solvated and mobilized during reaction, facilitating interactions among sites that change their nuclearity and function. Such intersite communication can be regulated by the zeolite support, resulting in non-single-site and potentially non-mean-field kinetic behavior arising from mechanisms of catalytic action that combine elements of those canonically associated with homogeneous and heterogeneous catalysis.We discuss recent literature examples that document dynamic active site behavior in metal-zeolites and outline methodologies to identify and interpret such behavior. We conclude with our outlook on future research directions to develop this evolving branch of catalysis science and harness it for practical applications.

APA, Harvard, Vancouver, ISO, and other styles

27

Yakovenko, R. E., V. G. Bakun, I. N. Zubkov, G. B. Narochnyi, O. P. Papeta, and A. P. Savost'yanov. "The Effect of the Preparation Method of Bifunctional Fischer – Tropsch Catalysts on the Composition and Properties of Synthetic Fuel." Kataliz v promyshlennosti 20, no. 4 (2020): 275–85. http://dx.doi.org/10.18412/1816-0387-2020-4-275-285.

Full text

Abstract:

The effect of the preparation method of bifunctional cobalt catalysts with HZSM-5 zeolite and a boehmite binder on the catalytic performance in the Fischer–Tropsch synthesis was studied. The synthesized catalysts were characterized by means of BET, XRD, EDX, SEM, TEM, H2 TPD and NH3 TPD methods and tested in the synthesis of hydrocarbons at a pressure of 2.0 MPa, temperature 240 °C, and gas hourly space velocity 1000 h–1. It was shown that the method of catalyst preparation can be used for controlling the hydrocarbon and fractional composition ofproducts of the Fischer – Tropsch synthesis. A promising composite catalytic system for the single-step synthesis of low-freezing diesel fuel was proposed.

APA, Harvard, Vancouver, ISO, and other styles

28

Niasar, Faeze Namayandeh, and Mohsen Moradian. "Synthesis of some derivatives of 1,8-dioxo-octa-hydro xanthene and 9-aryl-hexahydro acridine-1,8-dione using metal ion-exchanged NaY zeolite as heterogeneous catalyst." RSC Advances 14, no. 15 (2024): 10322–30. http://dx.doi.org/10.1039/d3ra03020b.

Full text

Abstract:

This is a process for producing xanthene and acridine derivatives. It uses copper metal catalysts supported by de-alumination zeolite-NaY. The process is conducted in a single pot and solvent-free conditions and does not require toxic reagents.

APA, Harvard, Vancouver, ISO, and other styles

29

de Reviere, Arno, Tom Vandevyvere, Maarten K. Sabbe та An Verberckmoes. "Renewable Butene Production through Dehydration Reactions over Nano-HZSM-5/γ-Al2O3 Hybrid Catalysts". Catalysts 10, № 8 (2020): 879. http://dx.doi.org/10.3390/catal10080879.

Full text

Abstract:

The development of new, improved zeolitic materials is of prime importance to progress heterogeneous catalysis and adsorption technologies. The zeolite HZSM-5 and metal oxide γ-Al2O3 are key materials for processing bio-alcohols, but both have some limitations, i.e., HZSM-5 has a high activity but low catalytic stability, and vice versa for γ-Al2O3. To combine their advantages and suppress their disadvantages, this study reports the synthesis, characterization, and catalytic results of a hybrid nano-HZSM-5/γ-Al2O3 catalyst for the dehydration of n-butanol to butenes. The hybrid catalyst is prepared by the in-situ hydrothermal synthesis of nano-HZSM-5 onto γ-Al2O3. This catalyst combines mesoporosity, related to the γ-Al2O3 support, and microporosity due to the nano-HZSM-5 crystals dispersed on the γ-Al2O3. HZSM-5 and γ-Al2O3 being in one hybrid catalyst leads to a different acid strength distribution and outperforms both single materials as it shows increased activity (compared to γ-Al2O3) and a high selectivity to olefins, even at low conversion and a higher stability (compared to HZSM-5). The hybrid catalyst also outperforms a physical mixture of nano-HZSM-5 and γ-Al2O3, indicating a truly synergistic effect in the hybrid catalyst.

APA, Harvard, Vancouver, ISO, and other styles

30

Nejadsalim, Aidin, Hamid Reza Godini, Sanjay Ramesh Kumar, et al. "Hydrogenation of Carbon Dioxide to Dimethyl Ether on CuO–ZnO/ZSM-5 Catalysts: Comparison of Powder and Electrospun Structures." Materials 16, no. 23 (2023): 7255. http://dx.doi.org/10.3390/ma16237255.

Full text

Abstract:

The promising direct dimethyl ether (DME) production through CO2 hydrogenation was systematically analyzed in this research by synthesizing, characterizing, and testing several catalytic structures. In doing so, various combinations of precipitation and impregnation of copper- and zinc-oxides (CuO–ZnO) over a ZSM-5 zeolite structure were applied to synthesize the hybrid catalysts capable of hydrogenating carbon dioxide to methanol and dehydrating it to DME. The resulting catalytic structures, including the co-precipitated, sequentially precipitated, and sequentially impregnated CuO–ZnO/ZSM-5 catalysts, were prepared in the form of particle and electrospun fibers with distinguished chemical and structural features. They were then characterized using XRD, BET, XPS, ICP, TGA, SEM, and FIB-SEM/EDS analyses. Their catalytic performances were also tested and analyzed in light of their observed characteristics. It was observed that it is crucial to establish relatively small-size and well-distributed zeolite crystals across a hybrid catalytic structure to secure a distinguished DME selectivity and yield. This approach, along with other observed behaviors and the involved phenomena like catalyst particles and fibers, clusters of catalyst particles, or the whole catalytic bed, were analyzed and explained. In particular, the desired characteristics of a CuO–ZnO/ZSM-5 hybrid catalyst, synthesized in a single-pot processing of the precursors of all involved catalytically active elements, were found to be promising in guiding the future efforts in tailoring an efficient catalyst for this system.

APA, Harvard, Vancouver, ISO, and other styles

31

Tan, Kok Bing, Guowu Zhan, Daohua Sun, Jiale Huang, and Qingbiao Li. "The development of bifunctional catalysts for carbon dioxide hydrogenation to hydrocarbons via the methanol route: from single component to integrated components." Journal of Materials Chemistry A 9, no. 9 (2021): 5197–231. http://dx.doi.org/10.1039/d0ta09607e.

Full text

Abstract:

We review and provide subtantial knowledge on bifunctional catalysts design strategies and development on metal/metal oxide and zeolite components: independently and integrated components for CO2 hydrogenation to hydrocarbons via methanol route.

APA, Harvard, Vancouver, ISO, and other styles

32

Witsuthammakul, Ayut, and Tawan Sooknoi. "Selective hydrodeoxygenation of bio-oil derived products: acetic acid to propylene over hybrid CeO2–Cu/zeolite catalysts." Catalysis Science & Technology 6, no. 6 (2016): 1737–45. http://dx.doi.org/10.1039/c5cy01485a.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Pagis, Céline, Christophe Bouchy, Mathias Dodin, Raquel Martinez Franco, David Farrusseng, and Alain Tuel. "Hollow Y zeolite single crystals: synthesis, characterization and activity in the hydroisomerization of n-hexadecane." Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 74 (2019): 38. http://dx.doi.org/10.2516/ogst/2019015.

Full text

Abstract:

Hollow Y zeolite single crystals have been obtained from a conventional NaY zeolite following a three-step process involving a severe dealumination of the zeolite with silicon tetrachloride (step #1), followed by an acid washing under mild conditions (step #2) and finally a selective dissolution of the crystals core in the presence of protective Al species (step #3). Crystals are characterized by the presence of a regular internal cavity with 0.1–0.2 nm thick microporous walls. They contain a relatively low framework Al content but significant amounts of extraframework Al oxide species mainly located on the external surface of the crystals. Hollow crystals have been mixed with a Pt-supported alumina binder and used as catalysts in the hydroisomerization of n-hexadecane. Compared to the corresponding bulk crystals obtained after step #2, their higher activity has been attributed to a better efficiency, directly resulting from the presence of the cavity.

APA, Harvard, Vancouver, ISO, and other styles

34

Morgado Prates, Ana Rita, Céline Pagis, Frederic C. Meunier, et al. "Hollow Beta Zeolite Single Crystals for the Design of Selective Catalysts." Crystal Growth & Design 18, no. 2 (2018): 592–96. http://dx.doi.org/10.1021/acs.cgd.7b01635.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Hamidi, Nurkholis, Rony Sessar Anugrah, Winarto Winarto, and Lilis Yuliati. "Improving Palm Oil Methylester Using Catalytic Cracking Methods." Journal of Advanced Research in Applied Sciences and Engineering Technology 64, no. 2 (2025): 72–80. https://doi.org/10.37934/araset.64.2.7280.

Full text

Abstract:

Biodiesel is a prospective substitute for diesel fuel that has garnered attention in recent years due to its environmentally conscious properties. However, biodiesel still exhibits several drawbacks in its features, namely in terms of its high viscosity, density, and flashpoint values. These factors can significantly impact the operation of the fuel motor engine, preventing it from operating at its ideal level. Consequently, biodiesel requires further processing to acquire properties that are appropriate for use in combustion engines, such as catalytic cracking with heterogeneous catalysts. The use of heterogeneous (solid) catalysts can effectively overcome this shortcoming. This study involved conducting experimental research on the effect of catalytic cracking on the characteristics of methyl-ester oil using a natural zeolite. The methyl ester was mixed with 5%mass of zeolite and heated for durations of 10, 15, 20, 25, and 30 minutes. Heterogeneous catalysts offer several benefits, such as facilitating the separation of biodiesel products, as well as the ability to regenerate and reuse the catalyst. To enhance the cost-effectiveness of biodiesel manufacturing. This study observed alterations in both the chemical composition and physical properties, as demonstrated by FTIR analysis and fuel physical properties tests. The content is primarily composed of double-chain (C=O) and single-chain (OH, C-CH3, CH2, CH3, C-O, C-CL, and C-Br) functional groups detected at absorption wavelengths ranging from 586.17 to 3006.45 cm-1. The viscosity, density, flashpoint, and calorific value of the methyl-ester with 5% zeolite combination dropped as the heating time increased. This is due to the elongation and subsequent dissociation of the hydrocarbon chains comprising the methyl-ester, which previously exhibited attractive forces. As a result, the intermolecular forces diminish, leading to a drop in the value of physical qualities.

APA, Harvard, Vancouver, ISO, and other styles

36

Pan, Wangxiang, Jingping He, Guanlin Huang, Wentao Zhang, and De Fang. "Research Progress of the Selective Catalytic Reduction with NH3 over ZSM-5 Zeolite Catalysts for NOx Removal." Catalysts 13, no. 10 (2023): 1381. http://dx.doi.org/10.3390/catal13101381.

Full text

Abstract:

Nitrogen oxides (NOx) are very common air pollutants that are harmful to the environment and human bodies. Selective catalytic reduction with ammonia (NH3-SCR) is considered an effective means to remove NOx emissions due to its good environmental adaptability, high catalytic activity, and remarkable selectivity. In this paper, the preparation methods, types, advantages, and challenges of ZSM-5 catalysts are reviewed. Special attention is paid to the catalytic properties and influence factors of ZSM-5 catalysts for NH3-SCR. The SCR performances of ZSM-5 catalysts doped with single or multiple metal ions are also reviewed. In addition, the environmental adaptabilities (sulfur resistance, alkali resistance, water resistance, and hydrothermal stability) of ZSM-5 catalysts are discussed, and the development of ZSM-5 catalysts in denitrification is summarized.

APA, Harvard, Vancouver, ISO, and other styles

37

Rice, Stephen B., Michael M. J. Treacy, and Mark M. Disko. "Imaging single platinum atoms on zeolites in the STEM." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (1990): 240–41. http://dx.doi.org/10.1017/s0424820100174333.

Full text

Abstract:

High angle annular dark-field (HAAD) imaging in the scanning transmission electron microscope has been shown in recent years to be a very effective tool in characterizing materials in which there are large differences in atomic number. Supported metal catalysts, in particular, have been explored extremely successfully using this Z-contrast technique. HAAD has very good sensitivity to high atomic number clusters on low atomic number supports, due to the approximately Z2 relationship. Furthermore, since the image contrast is due primarily to amplitude contrast, the resulting images are maps of mass thickness. Owing to the linear proportionality between intensity and the number of atoms probed, the intensity values integrated over metal clusters can be used as a measure of the cluster size.High resolution bright-field imaging is better suited for resolving structure in periodic specimens, and can be used to obtain structure images of zeolites. However, even with contrast enhancements such as Fourier filtering available from image processing, bright-field images are ineffective for detecting clusters containing fewer than about 20 Pt atoms in supports thicker than about 100Å. In comparison, we have demonstrated that the HAAD technique can be used successfully to detect single atoms of platinum on a 200Å thick zeolite support.

APA, Harvard, Vancouver, ISO, and other styles

38

DAS, N. K., and K. PRAMANIK. "ChemInform Abstract: Side-Chain Alkylation of Toluene with Methanol over Single Zeolite Catalysts." ChemInform 29, no. 39 (2010): no. http://dx.doi.org/10.1002/chin.199839044.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Li, Jiyang, Jihong Yu, and Ruren Xu. "Progress in heteroatom-containing aluminophosphate molecular sieves." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 468, no. 2143 (2012): 1955–67. http://dx.doi.org/10.1098/rspa.2012.0058.

Full text

Abstract:

Over the past 30 years, heteroatom-containing aluminophosphate molecular sieves as a prime class of heterogeneous single-site solid catalysts have been quickly developed since the first discovery of aluminophosphate molecular sieves in 1982, and a large variety of such materials with 48 unique zeotype structures have been prepared. This work mainly presents the progress in the development of heteroatom-containing aluminophosphate molecular sieves with new zeolite structures and variable framework compositions in recent years.

APA, Harvard, Vancouver, ISO, and other styles

40

Seeburg, Dominik, Dongjing Liu, Radostina Dragomirova, et al. "Low-Temperature Steam Reforming of Natural Gas after LPG-Enrichment with MFI Membranes." Processes 6, no. 12 (2018): 263. http://dx.doi.org/10.3390/pr6120263.

Full text

Abstract:

Low-temperature hydrogen production from natural gas via steam reforming requires novel processing concepts as well as stable catalysts. A process using zeolite membranes of the type MFI (Mobile FIve) was used to enrich natural gas with liquefied petroleum gas (LPG) alkanes (in particular, propane and n-butane), in order to improve the hydrogen production from this mixture at a reduced temperature. For this purpose, a catalyst precursor based on Rh single-sites (1 mol% Rh) on alumina was transformed in situ to a Rh1/Al2O3 catalyst possessing better performance capabilities compared with commercial catalysts. A wet raw natural gas (57.6 vol% CH4) was fully reformed at 650 °C, with 1 bar absolute pressure over the Rh1/Al2O3 at a steam to carbon ratio S/C = 4, yielding 74.7% H2. However, at 350 °C only 21 vol% H2 was obtained under these conditions. The second mixture, enriched with LPG, was obtained from the raw gas after the membrane process and contained only 25.2 vol% CH4. From this second mixture, 47 vol% H2 was generated at 350 °C after steam reforming over the Rh1/Al2O3 catalyst at S/C = 4. At S/C = 1 conversion was suppressed for both gas mixtures. Single alkane reforming of C2–C4 showed different sensitivity for side reactions, e.g., methanation between 350 and 650 °C. These results contribute to ongoing research in the field of low-temperature hydrogen release from natural gas alkanes for fuel cell applications as well as for pre-reforming processes.

APA, Harvard, Vancouver, ISO, and other styles

41

Singh, Bhupendra Kumar, Yongseok Kim, Seungdon Kwon, and Kyungsu Na. "Selective Catalytic Transfer Hydrogenolysis of Glycerol to 2-Isopropoxy-Propan-1-Ol over Noble Metal Ion-Exchanged Mordenite Zeolite." Catalysts 9, no. 11 (2019): 885. http://dx.doi.org/10.3390/catal9110885.

Full text

Abstract:

This study investigated the selective conversion of glycerol to 2-isopropoxy-propan-1-ol over noble metal ion-exchanged mordenite zeolites (RuMOR, RhMOR, and PdMOR) as heterogeneous catalysts via catalytic transfer hydrogenolysis (CTH) using propan-2-ol as the solvent, hydrogen supplier, and reactive coupling reagent with glycerol. The catalytic reactions were performed at 140 °C under inert conditions with a 0.5 MPa initial pressure of N2. A single product, 2-isopropoxy-propan-1-ol, was catalytically generated without any appreciable by-products. The catalytic results were reproducible, and the catalysts exhibited good recyclability.

APA, Harvard, Vancouver, ISO, and other styles

42

Xie, Jingxiu, and Unni Olsbye. "The Oxygenate-Mediated Conversion of COx to Hydrocarbons─On the Role of Zeolites in Tandem Catalysis." Chemical Reviews 123 (September 28, 2023): 11775–816. https://doi.org/10.1021/acs.chemrev.3c00058.

Full text

Abstract:

Decentralized chemical plants close to circular carbon sources will play an important role in shaping the postfossil society. This scenario calls for carbon technologies which valorize CO2 and CO with renewable H2 and utilize process intensification approaches. The single-reactor tandem reaction approach to convert COx to hydrocarbons via oxygenate intermediates offers clear benefits in terms of improved thermodynamics and energy efficiency. Simultaneously, challenges and complexity in terms of catalyst material and mechanism, reactor, and process gaps have to be addressed. While the separate processes, namely methanol synthesis and methanol to hydrocarbons, are commercialized and extensively discussed, this review focuses on the zeolite/zeotype function in the oxygenate-mediated conversion of COx to hydrocarbons. Use of shape-selective zeolite/zeotype catalysts enables the selective production of fuel components as well as key intermediates for the chemical industry, such as BTX, gasoline, light olefins, and C3+ alkanes. In contrast to the separate processes which use methanol as a platform, this review examines the potential of methanol, dimethyl ether, and ketene as possible oxygenate intermediates in separate chapters. We explore the connection between literature on the individual reactions for converting oxygenates and the tandem reaction, so as to identify transferable knowledge from the individual processes which could drive progress in the intensification of the tandem process. This encompasses a multiscale approach, from molecule (mechanism, oxygenate molecule), to catalyst, to reactor configuration, and finally to process level. Finally, we present our perspectives on related emerging technologies, outstanding challenges, and potential directions for future research.

APA, Harvard, Vancouver, ISO, and other styles

43

Psaltou, Savvina, Efthimia Kaprara, Manassis Mitrakas, and Anastasios I. Zouboulis. "Performance of Heterogeneous Catalytic Ozonation with Minerals in Degradation of p-Chlorobenzoic Acid (p-CBA) from Aqueous Solutions." Proceedings 48, no. 1 (2019): 12. http://dx.doi.org/10.3390/ecws-4-06432.

Full text

Abstract:

Water pollution is a critical environmental issue nowadays. One major problem is the pollution of freshwaters by pollutants of low concentrations (ng/L–μg/L), known as micropollutants. The most promising techniques for micropollutants degradation are Advanced Oxidation Processes (AOPs). Heterogeneous catalytic ozonation is among them, and recent studies have shown that it can be an efficient water treatment technique. The aim of this study is to evaluate the catalytic activity of five minerals (anatase, dolomite, kaolin, talc and zeolite) on the ozonation of small concentrations of p-CBA at pH 7 by batch mode experiments. p-CBA was employed as a model compound for evaluation of single and catalytic ozonation performance, because it cannot be efficiently removed by direct ozonation (kO3 < 0.15 M−1s−1), while it has high reactivity with hydroxyl radicals (k·OH = 5×109 M−1s−1). It was found that all applied solid materials can be characterized as catalysts, except kaolin, theuse of which presented almost the same performance with single ozonation. The best results were obtained by zeolite and dolomite (>99.4%) within 15 min reaction/oxidation time. These materials were neutrally (PZC = 6.8) and positively (PZC = 8.9) charged, respectively, during the oxidation process (pH 7), favoring the contact of micropollutant and ozone with the catalysts’ surface. On the other hand, the addition of anatase and talc in the ozonation system resulted in 97.5% and 98.5% p-CBA degradation, respectively, due to their slightly negative surface charge throughout the reaction. Conclusively, the experimental results indicated that the performance of heterogeneous catalytic ozonation is strongly depending on the surface charge of the solid materials (catalysts).

APA, Harvard, Vancouver, ISO, and other styles

44

Choi, Minkee, Kyungsu Na, Jeongnam Kim, Yasuhiro Sakamoto, Osamu Terasaki, and Ryong Ryoo. "Stable single-unit-cell nanosheets of zeolite MFI as active and long-lived catalysts." Nature 461, no. 7261 (2009): 246–49. http://dx.doi.org/10.1038/nature08288.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Liu, Yiwei, Zhi Li, Qiuying Yu, et al. "A General Strategy for Fabricating Isolated Single Metal Atomic Site Catalysts in Y Zeolite." Journal of the American Chemical Society 141, no. 23 (2019): 9305–11. http://dx.doi.org/10.1021/jacs.9b02936.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Shao, Yuanchao, Hongjuan Wang, Xuefei Liu, et al. "Single-crystalline hierarchically-porous TS-1 zeolite catalysts via a solid-phase transformation mechanism." Microporous and Mesoporous Materials 313 (January 2021): 110828. http://dx.doi.org/10.1016/j.micromeso.2020.110828.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Xie, Jun, Lang Chen, Wu-Hui Wang, Peng Wang, Chak-Tong Au, and Shuang-Feng Yin. "Direct dual-template synthesis of HZSM-5 zeolite for enhanced p-xylene selectivity in toluene methylation with CH3Br." Catalysis Science & Technology 7, no. 5 (2017): 1211–16. http://dx.doi.org/10.1039/c6cy02633h.

Full text

Abstract:

HZSM-5 catalysts of different crystal sizes directly synthesized by a single-step method using TPAOH and TEA as templates were characterized by XRD, SEM, N2 adsorption–desorption and NH3-TPD techniques.

APA, Harvard, Vancouver, ISO, and other styles

48

Kaprara, Efthimia, Charalampos Belesakos, Konstantinos Kollis, Savvina Psaltou, Anastasios Zouboulis, and Manassis Mitrakas. "Evaluation of Heterogeneous Catalytic Ozonation Process for the Removal of Micropollutants from Water/Wastewater: Application of a Novel Pilot-Scale Continuous Flow System." Catalysts 13, no. 5 (2023): 899. http://dx.doi.org/10.3390/catal13050899.

Full text

Abstract:

The present study evaluates the removal of micropollutants from water/wastewater contaminated sources through the application of a heterogeneous catalytic ozonation process, using a pilot-scale continuous operation unit, composed of a membrane module for the diffusion and effective dilution of ozone into the liquid phase to be treated and a plug flow reactor/continuous stirred tank reactor (PFR/CSTR) contact reactor system in series, where the catalyst is recirculated in dispersion mode. The solid materials tested as catalysts are natural and calcined zeolite, Bayoxide and alumina, whereas the examined micropollutants, used in this case as probe compounds, are p-chlorobenzoic acid (p-CBA), atrazine, benzotriazole and carbamazepine. A high-performance liquid chromatography system was used to determine the removal of micropollutants. In the case of p-CBA, an ozone-resistant compound, the addition of catalyst was found to significantly enhance its degradation rate, leading to >99% removal under the optimum defined conditions, i.e., in terms of catalyst concentration, pH, temperature, and process time. On the other hand, in the case of atrazine, a different ozone-resistant compound, the introduction of examined catalysts in the ozonation process was found to reduce the degradation of micropollutant, when compared with the application of single ozonation, indicating the importance of specific affinity between the pollutant and the solid material used as catalyst. Benzotriazole, a moderately ozone-reactive compound was degraded by more than 95% under all experimental conditions and catalysts tested in the pilot unit, while carbamazepine, a highly ozone-reactive compound, was completely removed even during the first stage of treatment process (i.e., at the membrane contactor). When increasing the pH value (in the range 6–8) and the contact time, the performance of catalytic ozonation process also improved.

APA, Harvard, Vancouver, ISO, and other styles

49

Yu-Kai, Liao, Cleto Bruzzese Paolo, Salvadori Enrico, and Chiesa Mario. "17O hyperfine spectroscopy in surface chemistry and catalysis." Journal of Magnetic Resonance Open 16-17 (March 13, 2023): 100101. https://doi.org/10.1016/j.jmro.2023.100101.

Full text

Abstract:

Oxide-based materials are of key technological importance in different areas including advanced functional materials, solid state chemistry and catalysis. Many of the key questions concerning these areas involve understanding the chemical bond between the metal and the oxygen ions in the first or subsequent coordinating shells. The spectroscopic study of oxygen is therefore of fundamental importance to elucidate the complex interfacial coordination chemistry that underlies the development of metal-oxide supported catalysts and other advanced materials. Oxygen atoms at solid surfaces or lining the pores of zeolite frameworks play a vital role in stabilizing and defining the electronic and geometric structure of single metal atoms or clusters that act as catalytically active sites. In the case of paramagnetic species, EPR and its related hyperfine techniques offer a unique opportunity to explore and understand the nature of the chemical bonding in metal-oxide systems through the detection of the 17O hyperfine interaction. In this perspective we offer an overview of experimental considerations and relevant examples specific to 17O hyperfine spectroscopy of transition metal ions in zeolites relevant to catalysis. 17O hyperfine coupling values are obtained, which allow discriminating σ- and π-bonding channels in metal-oxygen bonds involving first-row transition metal ions. An exhaustive collection of 17O hyperfine and nuclear quadrupole couplings in different systems including molecular and biomolecular chemistry is provided, emphasizing the connection between interfacial and molecular inorganic coordination chemistry.

APA, Harvard, Vancouver, ISO, and other styles

50

Hardiyanto, M. A., N. A. Sasongko, and H. Z. Almubaroq. "Analysis Of Isothermal Pyrolysis Process Of Municipal Waste Into Bio-Oil With The Addition Of Natural Catalyst (Zeolite) In Supporting National Energy Security." IOP Conference Series: Earth and Environmental Science 1267, no. 1 (2023): 012077. http://dx.doi.org/10.1088/1755-1315/1267/1/012077.

Full text

Abstract:

Abstract Conversion technology will continue to evolve. These developments started from the industrial revolution 1.0 to the industrial revolution 4.0, but in these developments even though technology solves a problem, it has the potential to cause new problems such as environmental problems. Environmental problems that can occur starting from energy conversion that is not environmentally friendly as well as the use of several technologies that cause pollutants that are quite dangerous if high intensity can even cause health problems, acid rain and climate change. The pyrolysis process has been proven capable of converting municipal solid waste (SPP) into bio-oil (BO) where most of the BO produced is hydrocarbon fuel with light oil (naphtha) and diesel types. Many studies have been carried out by various groups, but the raw materials used are single SPP components such as plastic, biomass, tire rubber, paper and not the real SPP. Therefore, this research was conducted to see the effect of using variations in zeolite catalyst concentration on the bio-oil produced. Variations in zeolite catalyst concentration are divided into concentrations of 0.25; 0.5; 0.75 and 1. For the pyrolysis test, it was carried out at a temperature of 400 ° C, with a reaction time of 60 minutes. From the results of experiments that have been carried out, the most ideal concentration for producing the most bio-oil products is at a concentration of 0.5. This indicates that the more catalysts are used in the pyrolysis process, the more syngas products will be produced. So the use of catalysts in the pyrolysis process can increase thermal efficiency and the pyrolysis process can be carried out at low temperatures for the production of bio-oil from mixed waste. If following national oil needs and these reserves continue to be exploited, Indonesia will only have oil reserves for the next 7-8 years or until 2028. Another problem is that the use of conventional fuel oil will produce large amounts of CO2 and will make a major contribution to climate change and global warming.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Single zeolite catalysts'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles