Effects of Cu loading and zeolite topology on the selective catalytic reduction with C3H6 over Cu/zeolite catalysts

Transparent Anti-SARS COV-2 Film from Copper(I) Oxide Incorporated in Zeolite Nanoparticles

The high antibacterial and antiviral performance of synthesized copper(I) oxide (Cu₂O) incorporated in zeolite nanoparticles (Cu-Z) was determined. Various Cu contents (1-9 wt %) in solutions were loaded in the zeolite matrix under neutral conditions at room temperature. All synthesized Cu-Z nanoparticles showed high selectivity of the cuprous oxide, as confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. An advantage of the prepared Cu-Z over the pristine Cu₂O nanoparticles was its high thermal stability. The 7 and 9 wt % Cu contents (07Cu-Z and 09Cu-Z) exhibited the best activities to deactivate Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. The film coated with 07Cu-Z nanoparticles also had high antiviral activities against porcine coronavirus (porcine epidemic diarrhea virus, PEDV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Specifically, the 07Cu-Z-coated film could reduce 99.93% of PEDV and 99.94% of SARS-CoV-2 viruses in 5 min of contact time, which were higher efficacies and faster than those of any previously reported works. The anti-SARS-CoV-2 virus film was coated on a low-cost PET or PVC film. A very small amount of cuprous oxide in zeolite was used to fabricate the antivirus film; therefore, the film was more transparent (79.4% transparency) than the cuprous oxide film or other commercial products. The toxicity of 07Cu-Z nanoparticles was determined by a toxicity test on zebrafish embryo and a skin irritation test to reconstruct a human epidermis (RhE) model. It was found that the impact on the aquatic environment and human skin was lower than that of the pristine Cu₂O.

Investigation of low-temperature performances of hybrid catalysts with different chain length OHC reductants

In the present work, NO_x conversion efficiency of the hybrid catalysts at low temperatures was investigated. ANP-TVM and ANP-TVC-TVM hybrid catalysts for OHC-SCR performance were prepared by the impregnation method. The properties of catalysts were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and X-ray diffraction (XRD) analyses. The NO_x conversion ratios with real diesel exhaust gases were performed using oxygenated hydrocarbon reductants such as ethanol, propanol, n-butanol and n-penthanol. Performances of the hybrid catalysts at different engine loads and low temperatures were investigated. It was determined that ANP-TVC-TVM gave better results at all temperatures and loads. In general, the performance of ANP-TVC-TVM hybrid catalyst was superior with ethanol reductant except for at 1 kW engine load. The maximum NO_x conversion ratio was 90.6% on the ANP-TVC-TVM hybrid catalyst with n-butanol at 1 kW engine load and 300°C.

Recent Advances in Catalysis Based on Transition Metals Supported on Zeolites

This article reviews the current state and development of thermal catalytic processes using transition metals (TM) supported on zeolites (TM/Z), as well as the contribution of theoretical studies to understand the details of the catalytic processes. Structural features inherent to zeolites, and their corresponding properties such as ion exchange capacity, stable and very regular microporosity, the ability to create additional mesoporosity, as well as the potential chemical modification of their properties by isomorphic substitution of tetrahedral atoms in the crystal framework, make them unique catalyst carriers. New methods that modify zeolites, including sequential ion exchange, multiple isomorphic substitution, and the creation of hierarchically porous structures both during synthesis and in subsequent stages of post-synthetic processing, continue to be discovered. TM/Z catalysts can be applied to new processes such as CO₂ capture/conversion, methane activation/conversion, selective catalytic NO_x reduction (SCR-deNO_x), catalytic depolymerization, biomass conversion and H₂ production/storage.

Copper-Based Plasmonic Catalysis: Recent Advances and Future Perspectives

With the capability of inducing intense electromagnetic field, energetic charge carriers, and photothermal effect, plasmonic metals provide a unique opportunity for efficient light utilization and chemical transformation. Earth-abundant low-cost Cu possesses intense and tunable localized surface plasmon resonance from ultraviolet-visible to near infrared region. Moreover, Cu essentially exhibits remarkable catalytic performance toward various reactions owing to its intriguing physical and chemical properties. Coupling with light-harvesting ability and catalytic function, plasmonic Cu serves as a promising platform for efficient light-driven chemical reaction. Herein, recent advancements of Cu-based plasmonic photocatalysis are systematically summarized, including designing and synthetic strategies for Cu-based catalysts, plasmonic catalytic performance, and mechanistic understanding over Cu-based plasmonic catalysts. What's more, approaches for the enhancement of light utilization efficiency and construction of active centers on Cu-based plasmonic catalysts are highlighted and discussed in detail, such as morphology and size control, regulation of electronic structure, defect and strain engineering, etc. Remaining challenges and future perspectives for further development of Cu-based plasmonic catalysis are also proposed.

Catalytic Performances of Cu/MCM-22 Zeolites with Different Cu Loadings in NH3-SCR

The NH₃-SCR activities and hydrothermal stabilities of five xCu/MCM-22 zeolites with different Cu loadings (x = 2–10 wt%) prepared by incipient wetness impregnation method were systematically investigated. The physicochemical properties of xCu/MCM-22 zeolites were analyzed by XRD, nitrogen physisorption, ICP-AES, SEM, NH₃-TPD, UV-vis, H₂-TPR and XPS experiments. The Cu species existing in xCu/MCM-22 are mainly isolated Cu²⁺, CuO_x and unreducible copper species. The concentrations of both isolated Cu²⁺ and CuO_x species in xCu/MCM-22 increase with Cu contents, but the increment of CuO_x species is more distinct, especially in high Cu loadings (>4 wt%). NH₃-SCR experimental results demonstrated that the activity of xCu/MCM-22 is sensitive to Cu content at low Cu loadings (≤4 wt%). When the Cu loading exceeds 4 wt%, the NH₃-SCR activity of xCu/MCM-22 is irrelevant to Cu content due to the severe pore blockage effects caused by aggregated CuO_x species. Among the five xCu/MCM-22 zeolites, 4Cu/MCM-22 with moderate Cu content has the best NH₃-SCR performance, which displays higher than 80% NO_x conversions in a wide temperature window (160–430 °C). Furthermore, the hydrothermal aging experiments (xCu/MCM-22 was treated at 750 °C for 10 h under 10% water vapor atmosphere) illustrated that all the xCu/MCM-22 zeolites exhibit high hydrothermal stability in NH₃-SCR reactions.

Properties of Iron-Modified-by-Silver Supported on Mordenite as Catalysts for NOx Reduction

A series of mono and bimetallic catalysts based on a Fe-Ag mixture deposited on mordenite was prepared by ion-exchange and evaluated in the catalytic activity test of the de-NOx reaction in the presence of CO/C3H6. The activity results showed that the most active samples were the Fe-containing ones, and at high temperatures, a co-promoter effect of Ag on the activity of Fe catalysts was also observed. The influence of the order of cation deposition on catalysts formation and their physicochemical properties was studied by FTIR (Fourier Transform Infrared Spectroscopy) of adsorbed NO, XANES (X-ray Absorption Near-Edge Structure), and EXAFS (Extended X-ray Absorption Fine Structure) and discussed in terms of the state of iron. Results of Fe K-edge XANES oscillations showed that, in FeMOR catalysts, iron was present in a disordered state as Fe3+ and Fe2+. In FeAgMOR, the prevailing species was Fe3+, while in the AgFeMOR catalyst, the state of iron was intermediate or mixed between FeMOR and FeAgMOR. The Fe K-edge EXAFS results were characteristic of a disordered phase, the first coordination sphere being asymmetric with two different Fe-O distances. In FeAgMOR and AgFeMOR, coordination of Fe-O was similar to Fe2O3 with a few amount of Fe2+ species. We may conclude that, in the bimetallic FeAgMOR and AgFeMOR samples, a certain amount of tetrahedral Al3+ ions in the mordenite framework is replaced by Fe3+ ions, confirming the previous reports that these species are active sites for the de-NOx reaction. Based on the thermodynamic analysis and experimental data, also, it was confirmed that the order of deposition of the components influenced the mechanism of active sites’ formation during the two steps ion-exchange synthesis.

Spectroscopic studies of MFI and USY zeolite layers over stainless steel 316L wire gauze meshes

The objective of our study was to develop and optimize the in situ synthesis of zeolitic thin coatings with USY (ultrastabilised form of faujasite) and MFI (Model Five) type structure on metallic structured catalysts supports using the hydrothermal method. Thus, obtained zeolitic materials were studied in terms of their prospective activity in selective catalytic reduction of nitrogen oxides (SCR of NO_x) with ammonia. Optimization of the preparation method consisted of several steps including: the pretreatment of steel carrier to obtain an adhesive surface, hydrothermal synthesis of zeolites at different conditions and adjustment of the zeolite structure type (MFI vs. USY). As a result, uniform zeolitic layers were deposited on steel supports. Prepared structured supports were ion-exchanged with copper or cobalt precursors to obtain active catalysts and then characterised by various physicochemical methods with a particular reference to the in situ Fourier-Transform Infrared Spectroscopy (FTIR), Ultraviolet-Visible Diffusion Reflectance Spectroscopy (DRS-UV/VIS) and Raman spectroscopy. For CuUSY sample, slightly better catalytic properties are related to higher copper content. In the case of Co-samples, worse catalytic properties in comparison with Cu counterparts might imply from higher concentration of Brønsted acid sites, lower cobalt loading (thus concentration of Lewis acid sites) and the presence of cobalt cation significantly in oxide form (evidenced by Raman, DRS-UV/VIS spectroscopy and by in situ FT-IR sorption studies).