| 1. |
- Bello, Estefania, et al.
(författare)
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NH3-SCR catalysts for heavy-duty diesel vehicles : Preparation of CHA-type zeolites with low-cost templates
- 2022
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Ingår i: Applied Catalysis B. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 303
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Tidskriftsartikel (refereegranskat)abstract
- Computer-assistance allows selecting the most adequate low-cost organic structure directing agents (OSDAs) for the crystallization of Al-rich CHA-type zeolites. The host-guest stabilization energies of tetraethylammonium (TEA), methyltriethylammonium (MTEA) and dimethyldiethylammonium (DMDEA), in combination with Na, were first theoretically evaluated. This ab-initio analysis reveals that two TEA show a serious steric hindrance in a cha cavity, whereas two MTEA would present excellent host-guest confinements. The synthesis of Al-rich CHA-type zeolites has been accomplished using TEA and MTEA. Electron diffraction and high-resolution transmission electron microscopy reveal large CHA-domains with narrow faulted GME-domains in the CHAtype material synthesized with TEA, confirming the better OSDA-directing roles of MTEA cations towards the cha cavity, in good agreement with DFT calculations. Cu-exchanged Al-rich CHA-type samples achieved with MTEA and TEA show excellent catalytic activity and hydrothermal stability for the selective catalytic reduction (SCR) of NOx with ammonia under conditions relevant for future heavy duty diesel conditions.
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| 2. |
- Bello-Jurado, Estefanía, et al.
(författare)
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Tunable CHA/AEI Zeolite Intergrowths with A Priori Biselective Organic Structure-Directing Agents : Controlling Enrichment and Implications for Selective Catalytic Reduction of NOx
- 2022
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 61:28
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Tidskriftsartikel (refereegranskat)abstract
- A novel ab initio methodology based on high-throughput simulations has permitted designing unique biselective organic structure-directing agents (OSDAs) that allow the efficient synthesis of CHA/AEI zeolite intergrowth materials with controlled phase compositions. Distinctive local crystallographic ordering of the CHA/AEI intergrowths was revealed at the nanoscale level using integrated differential phase contrast scanning transmission electron microscopy (iDPC STEM). These novel CHA/AEI materials have been tested for the selective catalytic reduction (SCR) of NOx, presenting an outstanding catalytic performance and hydrothermal stability, even surpassing the performance of the well-established commercial CHA-type catalyst. This methodology opens the possibility for synthetizing new zeolite intergrowths with more complex structures and unique catalytic properties.
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| 3. |
- Campbell, Charles, et al.
(författare)
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Bridging model and real catalysts: general discussion
- 2016
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Ingår i: Faraday Discussions. - 1359-6640 .- 1364-5498. ; 188, s. 565-589
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Charles Campbell opened the discussion of the paper by Hans-JoachimFreund: If you have a 3D gold particle and it spreads out to be a 2D particle whenyou adsorb CO2, it must gain energy stability. Did you estimate the energy changeof the overall process to do that?
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| 4. |
- Campbell, Charles, et al.
(författare)
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Catalyst design from theory to practice: general discussion
- 2016
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Ingår i: Faraday Discussions. - 1359-6640 .- 1364-5498. ; 188, s. 279-307
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Hans-Joachim Freund opened the discussion of the paper by Alberto Roldan:How is the atomic hydrogen produced on the greigite surface? In the paper (DOI:10.1039/C5FD00186B) there is no comment whether you studied dissociatehydrogen adsorption.
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| 5. |
- Jiang, Jiuxing, et al.
(författare)
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ITQ-54 : a multi-dimensional extra-large pore zeolite with 20 [times] 14 [times] 12-ring channels
- 2015
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Ingår i: Chemical Science. - 2041-6520 .- 2041-6539. ; 6, s. 480-485
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Tidskriftsartikel (refereegranskat)abstract
- A multi-dimensional extra-large pore silicogermanate zeolite, named ITQ-54, has been synthesised by in situ decomposition of the N,N-dicyclohexylisoindolinium cation into the N-cyclohexylisoindolinium cation. Its structure was solved by 3D rotation electron diffraction (RED) from crystals of ca. 1 [small mu ]m in size. The structure of ITQ-54 contains straight intersecting 20 [times] 14 [times] 12-ring channels along the three crystallographic axes and it is one of the few zeolites with extra-large channels in more than one direction. ITQ-54 has a framework density of 11.1 T atoms per 1000 A3, which is one of the lowest among the known zeolites. ITQ-54 was obtained together with GeO2 as an impurity. A heavy liquid separation method was developed and successfully applied to remove this impurity from the zeolite. ITQ-54 is stable up to 600 [degree]C and exhibits permanent porosity. The structure was further refined using powder X-ray diffraction (PXRD) data for both as-made and calcined samples.
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| 6. |
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| 7. |
- Kapaca, Elina, et al.
(författare)
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Synthesis and Structure of a 22 x 12 x 12 Extra-Large Pore Zeolite ITQ-56 Determined by 3D Electron Diffraction
- 2021
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 143:23, s. 8713-8719
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Tidskriftsartikel (refereegranskat)abstract
- A multidimensional extra-large pore germanosilicate, denoted ITQ-56, has been synthesized by using modified memantine as an organic structure-directing agent. ITQ-56 crystallizes as plate-like nanocrystals. Its structure was determined by 3D electron diffraction/MicroED. The structure of ITQ-56 contains extra-large 22-ring channels intersecting with straight 12-ring channels. ITQ-56 is the first zeolite with 22-ring pores, which is a result of ordered vacancies of double 4-ring (d4r) units in a fully connected zeolite framework. The framework density is as low as 12.4 T atoms/1000 angstrom(3). The discovery of the ITQ-56 structure not only fills the missing member of extra-large pore zeolite with 22-ring channels but also creates a new approach of making extra-large pore zeolites by introducing ordered vacancies in zeolite frameworks.
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| 8. |
- Kwon, Soonhyoung, et al.
(författare)
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One-Pot Synthesis of CHA/ERI-Type Zeolite Intergrowth from a Single Multiselective Organic Structure-Directing Agent
- 2024
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Ingår i: ACS Applied Materials and Interfaces. - 1944-8244 .- 1944-8252. ; 16:12, s. 14661-14668
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Tidskriftsartikel (refereegranskat)abstract
- We report the one-pot synthesis of a chabazite (CHA)/erionite (ERI)-type zeolite intergrowth structure characterized by adjustable extents of intergrowth enrichment and Si/Al molar ratios. This method utilizes readily synthesizable 6-azaspiro[5.6]dodecan-6-ium as the exclusive organic structure-directing agent (OSDA) within a potassium-dominant environment. High-throughput simulations were used to accurately determine the templating energy and molecular shape, facilitating the selection of an optimally biselective OSDA from among thousands of prospective candidates. The coexistence of the crystal phases, forming a distinct structure comprising disk-like CHA regions bridged by ERI-rich pillars, was corroborated via rigorous powder X-ray diffraction and integrated differential-phase contrast scanning transmission electron microscopy (iDPC S/TEM) analyses. iDPC S/TEM imaging further revealed the presence of single offretite layers dispersed within the ERI phase. The ratio of crystal phases between CHA and ERI in this type of intergrowth could be varied systematically by changing both the OSDA/Si and K/Si ratios. Two intergrown zeolite samples with different Si/Al molar ratios were tested for the selective catalytic reduction (SCR) of NOx with NH3, showing competitive catalytic performance and hydrothermal stability compared to that of the industry-standard commercial NH3-SCR catalyst, Cu-SSZ-13, prevalent in automotive applications. Collectively, this work underscores the potential of our approach for the synthesis and optimization of adjustable intergrown zeolite structures, offering competitive alternatives for key industrial processes.
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| 9. |
- Lofstedt, Joakim, et al.
(författare)
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Green Diesel from Kraft Lignin in Three Steps
- 2016
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 9:12, s. 1392-1396
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Tidskriftsartikel (refereegranskat)abstract
- Precipitated kraft lignin from black liquor was converted into green diesel in three steps. A mild Ni-catalyzed transfer hydrogenation/hydrogenolysis using 2-propanol generated a lignin residue in which the ethers, carbonyls, and olefins were reduced. An organocatalyzed esterification of the lignin residue with an insitu prepared tall oil fatty acid anhydride gave an esterified lignin residue that was soluble in light gas oil. The esterified lignin residue was coprocessed with light gas oil in a continous hydrotreater to produce a green diesel. This approach will enable the development of new techniques to process commercial lignin in existing oil refinery infrastructures to standardized transportation fuels in the future.
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| 10. |
- Martinez-Franco, Raquel, et al.
(författare)
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Supra-molecular assembly of aromatic proton sponges to direct the crystallization of extra-large-pore zeotypes
- 2014
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Ingår i: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences. - : The Royal Society. - 1364-5021 .- 1471-2946. ; 470:2166
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Tidskriftsartikel (refereegranskat)abstract
- The combination of different experimental techniques, such as solid C-13 and H-1 magic-angle spinning NMR spectroscopy, fluorescence spectroscopy and powder X-ray diffraction, together with theoretical calculations allows the determination of the unique structure directing the role of the bulky aromatic proton sponge 1,8-bis(dimethylamino)naphthalene (DMAN) towards the extra-large-pore ITQ-51 zeolite through supra-molecular assemblies of those organic molecules.
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