Synthesis of High-Silica Erionite Driven by Computational Screening of Hypothetical Zeolites

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemistry of Materials, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.chemmater.9b01229.[EN] A hypothetical zeolite framework was selected from a database of hypothetical structures and adapted based on the structural features relevant for deNOx and MTO catalysis. To attempt the realization of this structure, a computational energy-based approach was applied to select relevant organic structure directing agent (OSDA) molecules with large OSDA-zeolite stabilization energies, leading to the selection of three OSDAs (OSDA1, OSDA2, and OSDA3) as potential candidates for the synthesis of the hypothetical zeolite (Hypo#1). Instead of Hypo#1, erionite (ERI) was found to dominate the experimental product outcome when potassium was used as a mineralizing agent. In the case of OSDA3, a novel high-silica ERI was found. The different ERI products were characterized, intergrowth structures ruled out, and special attention was paid to the compositional and morphological features arising from the use of the different OSDAs. In the specific high-Si product obtained using OSDA3, a distinct tubular to prismatic crystal morphology could be seen. Theoretical stabilization energies calculated for potentially competing phases (Hypo#1, ERI, offretite (OFF), and chabazite (CHA) among others) could be used to rationalize the experimental outcome to a certain extent, but our results also show that only considering zeolite-OSDA interaction is probably not sufficient to realize hypothetical frameworks, especially for Al-containing zeolites where alkali ions play an important role during crystallization.The authors thank Haldor Topsoe A/S and Innovation Fund Denmark for financial support under the Industrial PhD programe (case no. 1355-0174B). We thank MINECO of Spain for funding (SEV-2016-0683 and RTI2018-101033-B-100) and ASIC-UPV for the use of computational facilities. We also thank Prof. M. M. J. Treacy for assistance with the Database of Prospective Zeolite Structures.Boruntea, C.; Sastre Navarro, GI.; Lundegaard, LF.; Corma Canós, A.; Vennestrom, PNR. (2019). Synthesis of High-Silica Erionite Driven by Computational Screening of Hypothetical Zeolites. Chemistry of Materials. 31(22):9268-9276. https://doi.org/10.1021/acs.chemmater.9b01229S92689276312

Tracking Structural Deactivation of H-Ferrierite Zeolite Catalyst During MTH with XRD

publishedVersio

Identification and HLA-Tetramer-Validation of Human CD4(+) and CD8(+) T Cell Responses against HCMV Proteins IE1 and IE2

Human cytomegalovirus (HCMV) is an important human pathogen. It is a leading cause of congenital infection and a leading infectious threat to recipients of solid organ transplants as well as of allogeneic hematopoietic cell transplants. Moreover, it has recently been suggested that HCMV may promote tumor development. Both CD4+ and CD8+ T cell responses are important for long-term control of the virus, and adoptive transfer of HCMV-specific T cells has led to protection from reactivation and HCMV disease. Identification of HCMV-specific T cell epitopes has primarily focused on CD8+ T cell responses against the pp65 phosphoprotein. In this study, we have focused on CD4+ and CD8+ T cell responses against the immediate early 1 and 2 proteins (IE1 and IE2). Using overlapping peptides spanning the entire IE1 and IE2 sequences, peripheral blood mononuclear cells from 16 healthy, HLA-typed, donors were screened by ex vivo IFN-γ ELISpot and in vitro intracellular cytokine secretion assays. The specificities of CD4+ and CD8+ T cell responses were identified and validated by HLA class II and I tetramers, respectively. Eighty-one CD4+ and 44 CD8+ T cell responses were identified representing at least seven different CD4 epitopes and 14 CD8 epitopes restricted by seven and 11 different HLA class II and I molecules, respectively, in total covering 91 and 98% of the Caucasian population, respectively. Presented in the context of several different HLA class II molecules, two epitope areas in IE1 and IE2 were recognized in about half of the analyzed donors. These data may be used to design a versatile anti-HCMV vaccine and/or immunotherapy strategy

K-paracelsian (KAlSi3O8·H2O) and identification of a simple building scheme of dense double-crankshaft zeolite topologies

During screening of the phase space using KOH and 1-methyl-4-aza-1-azoniabicyclo[2.2.2]octane hydroxide (1-methyl-DABCO) under hydrothermal zeolite synthesis conditions, K-paracelsian was synthesized. Scanning electron microscopy, energy dispersive X-ray spectroscopy and ex situ powder X-ray diffraction analysis revealed a material that is compositionally closely related to the mineral microcline and structurally closely related to the mineral paracelsian, both of which are feldspars. In contrast to the feldspars, K-paracelsian contains intrazeolitic water corresponding to one molecule per cage. In the case of K-paracelsian it might be useful to consider it a link between feldspars and zeolites. It was also shown that K-paracelsian can be described as the simplest endmember of a family of dense double-crankshaft zeolite topologies. By applying the identified building principle, a number of known zeolite topologies can be constructed. Furthermore, it facilitates the construction of a range of hypothetical small-pore structures that are crystallo-chemically healthy, but which have not yet been realized experimentally

Crystallization of AEI and AFX zeolites through zeolite-to-zeolite transformations

[EN] The OH-/T-atom ratio and the Al-source are identified as critical parameters for the successful crystallization of AEI and AFX type zeolites when sufficient organic structure directing agent (OSDA) molecules are present. Especially the use of a zeolite as the Al-source is essential. When a complete zeolite-to-zeolite transformation of FAU is explored it is found to proceed without any solid crystalline intermediates. The optimal OH-/T-atom ratio can also be decreased when the Al-content in the reactant zeolite is increased to resemble the product composition better. This makes higher yields and better utilization of the OSDA possible compared to gels with less Al. During successful zeolite transformations the lattice parameter of FAU, which is proportional to the Alcontent, seems to converge at a certain range before the onset of product crystallization. This indicates that successful nucleation and/or formation of the target zeolite is dependent on this type of intermediate and dependent on the dissolution of the starting zeolite. Based on the findings of optimal OH-/T-atom ratios and synchronization of Si/Al ratio in the reactant zeolite with the product zeolite we also show that AEI and AFX can be obtained from CHA, which has similar structural features, but a higher framework density (FD) than e.g. FAU. This indicates that zeolite-to-zeolite transformations does not have to proceed from zeolites with low FDs (i.e. high stabilization energies) to higher FDs (i.e. lower stabilization energies), but is mainly driven by favorable OSDA-zeolite interactions. Overall, results are rationalized in a scheme where the dissolution rate of a starting zeolite with key structural features must be lower than the crystallization of the zeolite product in order to obtain a successful zeolite-to-zeolite transformation.The authors thank Haldor Topsoe A/S and Innovation Fund Denmark for financial support under the Industrial PhD programme (Case no. 1355-0174B).Boruntea, C.; Lundegaard, LF.; Corma Canós, A.; Vennestrom, PNR. (2019). Crystallization of AEI and AFX zeolites through zeolite-to-zeolite transformations. Microporous and Mesoporous Materials. 278:105-114. https://doi.org/10.1016/j.micromeso.2018.11.002S10511427

Pyrolysis of a metal–organic framework followed by in situ X-ray absorption spectroscopy, powder diffraction and pair distribution function analysis

Metal–organic frameworks (MOFs) can serve as precursors for new nanomaterials via thermal decomposition. Such MOF-derived nanomaterials (MDNs) are often comprised of metal and/or metal oxide particles embedded on porous carbon. The morphology of MDNs is similar to that of the precursor MOF, and improved stability and catalytic properties have been demonstrated. However, the pathway from MOF to MDN is only well understood for a few systems, and in situ studies are needed to elucidate the full phase behaviour and time/temperature dependency. In this work, we follow the MOF-to-MDN transformation in situ by using three complementary techniques: X-ray absorption spectroscopy (XAS), powder X-ray diffraction (PXRD), and X-ray total scattering/pair distribution function (TS/PDF) analysis. The thermal decomposition of HKUST-1, i.e. the archetypical MOF Cu$_3$(btc = 1,3,5-benzenetricarboxylate)$_2$, is followed from room temperature to 500 °C by applying different heating ramps. Real space correlations are followed by PDF and extended X-ray absorption fine structure (EXAFS) analysis, and quantitative phase fractions are obtained by refinement of PXRD and PDF data, and by linear combination analysis (LCA) of X-ray absorption near edge Structure (XANES) data. We find that HKUST-1 decomposes at 300–325 °C into copper(I) oxide and metallic copper. Above 350–470 °C, metal particles remain as the only copper species. There is an overall good agreement between all three techniques with respect to the phase evolution, and the study paves the road towards rational synthesis of a Cu$_2$O/Cu/carbon material with the desired metal/metal oxide composition. More importantly, our investigations serve as a benchmark study demonstrating that this methodology is generally applicable for studying the thermal decomposition of MOFs

Copper mobility in zeolite-based SCR catalysts

Selective catalytic reduction with ammonia (NH3-SCR) is an effective, well-established method to eliminate nitrogen oxides (NOx) in oxygen excess for stationary and mobile applications. Titania-supported vanadia catalysts are traditionally used for NH3-SCR. This type of catalyst is effective in the range 300-450\ub0C, but the NOx reduction efficiency decreases at both lower and higher temperatures. The efficiency of the NH3-SCR process can be improved significantly by using catalysts based on copper-exchanged zeolites and zeotypes, due to their high activity around 200\ub0C. Solid-state ion-exchange in a mixture of copper oxide and zeolite is an efficient way to prepare such catalysts, but this process usually requires high (>700\ub0C) temperatures. The ion-exchange can be considerably affected by appropriate choice of atmosphere during the process. It is shown that the copper-exchange is possible at unprecedented low temperatures, as low as 250\ub0C, in presence of ammonia. The influence of the treatment conditions on the copper-exchange and the mechanism of the reaction-driven ion-exchange process will be presented and discussed. Such copper-exchanged zeolite structures with high copper loading are potentially interesting catalysts for a number of technical applications.Powder mixtures of Cu2O or CuO and zeolite with either CHA, MFI or *BEA framework structure were exposed to well-defined gas atmospheres at constant temperature. After the treatment, the SCR activity of the samples was determined by steady state and transient flow reactor experiments, and the physicochemical properties of the samples were characterized with bulk and surface sensitive characterization techniques. Furthermore, first-principles calculations were used to investigate the energetic conditions for the ion-exchange process.We show that in the presence of ammonia, copper becomes mobile at considerably lower temperatures

Solid-State Ion-Exchange of Copper into Zeolites Facilitated by Ammonia at Low Temperature

The effect of the gas phase during solid-state ion-exchange of copper into zeolites was studied by exposing physical mixtures of copper oxides (Cu^I₂O and Cu^IIO) and zeolites (MFI, *BEA, and CHA) to various combinations of NO, NH₃, O₂, and H₂O. It is shown that heating these mixtures to 250 °C results in active catalysts for the selective catalytic reduction of NO with NH₃ (NH₃-SCR), indicating that the Cu has become mobile at that temperature. Such treatment allows for a fast (<5–10 h) preparation of copper-exchanged zeolites. Scanning transmission electron microscopy analysis of Cu-CHA prepared using this method shows homogeneous distribution of the Cu in the primary particles of the zeolite. In situ XRD reveals that the Cu ion-exchange is related to the formation of Cu^I₂O. When the zeolite is mixed with Cu^IIO, addition of NO to the NH₃-containing gas phase enhances the formation of Cu^I₂O and the Cu ion-exchange. The mobility of Cu at low temperatures is proposed to be related to the formation of [Cu^I(NH₃)_<i>x</i>]⁺ (<i>x</i> ≥ 2) complexes

Mobility of copper in zeolite-based SCR catalysts

Selective catalytic reduction with ammonia (NH3-SCR) is a well-established and effective method to eliminate nitrogen oxides (NOx) in oxygen excess for stationary and mobile applications. Vanadia supported on titania was the first NH3-SCR catalyst that was commercialized. This type of catalyst is effective around 300-450\ub0C, however at lower or higher temperatures, the efficiency of the catalyst to reduce NOx decreases. To increase the overall NOx reduction, high SCR activity around 200\ub0C is required and copper-exchanged zeolites are interesting candidates in this respect. Solid-state ion-exchange in a mixture of copper oxide and zeolite is an efficient method to prepare such catalysts, but the process usually requires high (>700\ub0C) temperatures. The ion-exchange process with copper oxides and zeolites can be considerably affected inpresence of reactive atmospheres. It is shown that the copper-exchange is possible at unprecedented low temperatures, as low as 250\ub0C, when facilitated by ammonia. The influence of the treatment conditions on the copper-exchange and the mechanism of the ion-exchange process will be presented and discussed. Such copper-exchanged zeolite structures with high copper loading are potentially interesting catalysts for a number of technical applications.Powder mixtures of CuO or Cu2O and zeolite with either the MFI, *BEA or CHA framework structure were exposed to well-defined gas atmospheres at constant temperature. After the treatment the SCR activity was determined by steady state and transient flow reactor experiments, and the physico-chemical properties of the samples were characterized with bulk and surface sensitive characterization techniques. Furthermore, density functional theory calculations were used to investigate the energetic conditions for the ion-exchange process. We show that copper in the presence of ammonia becomes mobile at considerably lower temperatures