Rational Design and Targeted Synthesis of Small-Pore Zeolites with the Assistance of Molecular Modeling, Structural Analysis, and Synthetic Chemistry
03 Nov 2021-Industrial & Engineering Chemistry Research (American Chemical Society (ACS))-Vol. 60, Iss: 43, pp 15403-15415
About: This article is published in Industrial & Engineering Chemistry Research.The article was published on 2021-11-03 and is currently open access. It has received 5 citations till now. The article focuses on the topics: Rational design.
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30 Jan 2022
TL;DR: The structure of zeolite SSZ-43 was determined by 3D electron diffraction, synchrotron X-ray powder diffraction and high-resolution transmission electron microscopy as mentioned in this paper .
Abstract: Abstract The structure of zeolite SSZ‐43 was determined by 3D electron diffraction, synchrotron X‐ray powder diffraction, and high‐resolution transmission electron microscopy. The SSZ‐43 framework forms one‐dimensional, sinusoidal 12‐ring channels from 5461 butterfly units commonly found in other zeolites, but with unique 6.5×6.5 Å apertures and 12‐ring 6.5×8.9 Å windows perpendicular to the channels. SSZ‐43 crystals are intergrowths of two polytypes: ≈90 % orthorhombic polytype A with ABAB stacking of the 12‐rings, and ≈10 % monoclinic polytype B with ABCABC stacking. Molecular modeling performed on the idealized Si‐SSZ‐43 structure along with empirical relationships for zeolite selectivity in boron‐ and aluminum‐containing synthesis gels were used in a combined approach to design new di‐quaternary ammonium organic structure‐directing agents (OSDAs). Experimental trials demonstrated that the new OSDAs produced SSZ‐43 over a broader range of compositions than previous mono‐quaternary OSDAs.
2 citations
24 Jan 2023
TL;DR: The use of organics in the synthesis gel creates additional opportunities for directing a specific zeolite structure, templating, space filling, and charge compensation, and the enormous variety of shapes and sizes of these organics can be both daunting and exciting as mentioned in this paper .
Abstract: Zeolite synthesis can be a tricky process due to the interactions between inorganic species, organic structure-directing agents, and processing conditions. Our understanding of the underlying mechanisms at work is further obscured by the complex interplay between thermodynamics and kinetics. Molecular modeling can help guide the direction of syntheses, although true a priori prediction of zeolite products is still an elusive goal. These synthesis variables are often interconnected, and modification to one must be made with consideration to trends identified in others. Important inorganic conditions include heteroatom type and content, reagent sources, alkali and total hydroxide content, mineralizing agent, and the role of water. The use of organics in the synthesis gel creates additional opportunities for directing a specific zeolite structure, templating, space-filling, and charge compensation, and the enormous variety of shapes and sizes of these organics can be both daunting and exciting. Molecular modeling is especially useful for predicting the interaction energies between these organics and the inorganic framework, and it has helped shape our interpretation of observed experimental results. Finally, the way in which zeolite research is carried out using high throughput, automation, and data mining will be critical to making step-change advancements in the field of zeolite synthesis.
24 Jan 2023
TL;DR: The potential of computational modeling in the design of organic structure directing agents (OSDAs) for target small-pore zeolites was demonstrated some three decades ago by the use of the ZEBEDDE program for an aluminophosphate zeotype with the CHA topology as discussed by the authors .
Abstract: The potential of computational modeling in the design of organic structure directing agents (OSDAs) for target small-pore zeolites was demonstrated some three decades ago by the use of the ZEBEDDE program for an aluminophosphate zeotype with the CHA topology. In this structure type, d6r units are the only secondary building units (SBUs) and there is a single type of cage, making the approach relatively straightforward, but in other target structures of catalytic interest there may be more than one cage type. The use of a co-templating strategy, in which OSDAs are computationally-designed specifically for each cage type, has therefore been explored. This has been successful, both for AlPOs, where organic cations alone are required as templates, and also for zeolites, where inorganic cations required for aluminosilicate gel crystallization also perform templating functions, favoring specific SBUs. The successful use of co-templates in a synthesis requires that each has similar templating efficacy, to avoid either formation of a dominant single-template phase or a simple mixture of phases. Examples of computation-led new material syntheses that demonstrate these principles include SAPOs with the SAV, AFX, and SFW structure types and aluminosilicates of the RHO family of embedded isoreticular zeolites. Where structural considerations permit, for example in polytypes in the ABC-6 or other structural families, intergrown systems with either simple or statistically-complex patterns of intergrowths can result. These have characteristic pore size distributions and physical properties, and here a deep understanding and control over the ratio of intergrowth phases can only be achieved by detailed characterization and modeling as reported, for example for the JMZ-11 family.
TL;DR: The structure of zeolite SSZ-43 was determined by 3D electron diffraction, synchrotron X-ray powder diffraction and high-resolution transmission electron microscopy as discussed by the authors .
Abstract: The structure of zeolite SSZ-43 was determined by 3D electron diffraction, synchrotron X-ray powder diffraction, and high-resolution transmission electron microscopy. The SSZ-43 framework forms one-dimensional, sinusoidal 12-ring channels from 5461 butterfly units commonly found in other zeolites, but with unique 6.5×6.5 Å apertures and 12-ring 6.5×8.9 Å windows perpendicular to the channels. SSZ-43 crystals are intergrowths of two polytypes: ≈90 % orthorhombic polytype A with ABAB stacking of the 12-rings, and ≈10 % monoclinic polytype B with ABCABC stacking. Molecular modeling performed on the idealized Si-SSZ-43 structure along with empirical relationships for zeolite selectivity in boron- and aluminum-containing synthesis gels were used in a combined approach to design new di-quaternary ammonium organic structure-directing agents (OSDAs). Experimental trials demonstrated that the new OSDAs produced SSZ-43 over a broader range of compositions than previous mono-quaternary OSDAs.
TL;DR: In this paper , a new layer silicate zeolite L was synthesized using the N, N-dimethyl-(2-methyl)-benzimidazolium as the structure-directing agent (SDA) under fluoride condition.
Abstract: Two dimensional zeolites have drawn a lot of attention due to their structural diversity and chemical composition, which can be used to obtain 3D zeolites unable to be direct synthesized. Here, a new layer silicate zeolite L was synthesized using the N, N-dimethyl-(2-methyl)-benzimidazolium as the structure-directing agent (SDA) under fluoride condition. Structure determination from the single-crystal X-ray diffraction reveals that the pure silica precursor with five-ring pores in the crystalline sheets is composed of the rth layer stacking along the (001) direction in an …AAAA… sequence with SDA + cations and F - residing within the interlayer spaces. Variable temperature powder X-ray diffraction results showed the new layer could transform into 3D RTH topology structure at 350 °C via 2D-3D topotactic transformation. Furthermore, a new 3D zeolite material is obtained by treating the original layer with diethoxydimethylsilane agent under hydrochloric acid condition (HCl-DEDMS). Based on the powder X-ray diffraction (PXRD) and the original layer structure, the new 3D zeolite structure expanding the rth layer linking with another Si atom is constructed, which possesses a 10×8×6 channel system. It displays a high BET surface area of 188 cm 3 /g with an external surface area of 130 cm 3 /g. The structure and textural properties pave a way for the potential catalytic application. The research not only provides a new layer zeolite, broadening the 2D zeolite framework types, but also allows for the discovery of a new stable 3D zeolite expanding the RTH structure with Si atom, which hasn't been reported yet.
References
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TL;DR: The differences between the active site of all‐atom minimized structure and the experimental structure are similar to differences observed between crystal structures of the same protein.
Abstract: A study of the binding of the antibacterial agent trimethoprim to Escherichia coli dihydrofolate reductase was carried out using energy minimization techniques with both a full, all-atom valence force field and a united atom force field. Convergence criteria ensured that no significant structural or energetic changes would occur with further minimization. Root-mean-square (RMS) deviations of both minimized structures with the experimental structure with the experimental structure were calculated for selected regions of the protein. In the active site, the all-atom minimized structure fit the experimental structure much better than did the united atom structure. To ascertain what constitutes a good fit, the RMS deviations between crystal structures of the same enzyme either from different species or in different crystal environments were compared. The differences between the active site of all-atom minimized structure and the experimental structure are similar to differences observed between crystal structures of the same protein.
Finally, the energetics of ligand binding were analyzed for the all-atom minimized coordinates. Strain energy induced in the ligand, the corresponding entropy loss due to shifts in harmonic frequencies, and the role of specific residues in ligand binding were examined. Water molecules, even those not in direct contact with the ligand, were found to have significant interaction energies with the ligand. Thus, the inclusion of at least one shell of waters may be vital for accurate simulations of enzyme complexes.
1,812 citations
TL;DR: An account of the mechanistic aspects of hydrothermal zeolite synthesis can be found in this paper, where a review of the most probable mechanistic pathways in Zeolite formation is given.
1,262 citations
TL;DR: In this paper, a brief summary of the key issues for the methanol-to-olefins (MTO) reaction is given, including studies on the reaction mechanism, molecular sieve synthesis and crystallization mechanism, catalyst and its manufacturing scale-up, reactor selection and reactor scaleup, process demonstration, and commercialization.
Abstract: The methanol-to-olefins (MTO) reaction is an interesting and important reaction for both fundamental research and industrial application. The Dalian Institute of Chemical Physics (DICP) has developed a MTO technology that led to the successful construction and operation of the world’s first coal to olefin plant in 2010. This historical perspective gives a brief summary on the key issues for the process development, including studies on the reaction mechanism, molecular sieve synthesis and crystallization mechanism, catalyst and its manufacturing scale-up, reactor selection and reactor scale-up, process demonstration, and commercialization. Further challenges on the fundamental research and the directions for future catalyst improvement are also suggested.
1,174 citations
21 Apr 2010
TL;DR: Avelino Corma as discussed by the authors is a co-author of more than 700 articles and 100 patents on acid-base and redox catalysis and molecular sieves covering aspects of synthesis, characterization and reactivity in acid base and redoxide catalysis, and is the director of the Instituto de Tecnologia Quimica (UPV-CSIC) at the Universidad Politecnica de Valencia since 1990.
Abstract: Prof. AVELINO CORMA was born in Moncofar, Spain in 1951. He studied Chemistry at the Universidad de Valencia (1967-1973), and received his Ph.D. at the Universidad Complutense de Madrid in 1976. He was a Postdoctoral researcher in the Department of chemical engineering at the Queen?s University (Canada, 1977-79). Prof. Corma is the director of the Instituto de Tecnologia Quimica (UPV-CSIC) at the Universidad Politecnica de Valencia since 1990. His current research field is catalysis, and molecular sieves covering aspects of synthesis, characterization and reactivity in acid-base and redox catalysis. Avelino Corma is co-author of more than 700 articles and 100 patents on these subjects.
532 citations
TL;DR: In this paper, a general recursion algorithm is described for calculating kinematical diffraction intensities from crystals containing coherent planar faults, which exploits the self-similar stacking sequences that occur when layers stack non-deterministically.
Abstract: A general recursion algorithm is described for calculating kinematical diffraction intensities from crystals containing coherent planar faults. The method exploits the self-similar stacking sequences that occur when layers stack non-deterministically. Recursion gives a set of simple relations between average interference terms from a statistical crystal, which can be solved as a set of simultaneous equations. The diffracted intensity for a polycrystalline sample is given by the incoherent sum of scattered intensities over an ensemble of crystallites. The relations between this and previous approaches, namely the Hendricks-Teller matrix formulation, the difference equation method, the summed series formula of Cowley, and Michalski’s recurrence relations between average phase factors, are discussed. Although formally identical to these previous methods, the present recursive description has an intuitive appeal and proves easier to apply to complex crystal structure types. The method is valid for all types of planar faults, can accommodate long-range stacking correlations, and is applicable to crystals that contain only a finite number of layers. A FORTRAN program DIFFaX , based on this recursion algorithm, has been written and used to simulate powder X-ray (and neutron) diffraction patterns and single crystal electron (kinematical) diffraction patterns. Calculations for diamond-lonsdaleite and for several synthetic zeolite systems that contain high densities of stacking faults are presented as examples.
524 citations