Search Results (5)

Three bimetallic catalysts of the type M–Cu with M = Ag, Au and Ni supports were successfully prepared by a two-step synthesized method using Cu/Al₂O₃-CeO₂ as the base monometallic catalyst. The nanocatalysts were characterized using X-ray diffraction (XRD), temperature-programmed reduction of H₂ (H₂-TPR), N₂ adsorption-desorption, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and ultraviolet–visible spectroscopy with diffuse reflectance (DR-UV-Vis) techniques. This synthesized methodology allowed a close interaction between two metals on the support surface; therefore, it could have synthesized an efficient transition–noble mixture bimetallic nanostructure. Alloy formation through bimetallic nanoparticles (BNPs) of AgCuAlCe and AuCuAlCe was demonstrated by DR–UV–Vis, EDS, TEM and H₂-TPR. Furthermore, in the case of AgCuAlCe and AuCuAlCe, improvements were observed in their reducibility, in contrast to NiCuAlCe. The addition of a noble metal over the monometallic copper-based catalyst drastically improved the phenol mineralization. The higher activity and selectivity to CO₂ of the bimetallic gold–copper- and silver–copper-supported catalysts can be attributed to the alloy compound formation and the synergetic effect of the M–Cu interaction. Petroleum Refinery Wastewater (PRW) had a complex composition that affected the applied single CWAO treatment, rendering it inefficient. Full article

PROMETHEUS catalyst, a copper-based polymetallic nano-catalyst has been proven to be suitable for automotive emission control applications. This novel catalyst consists of copper, palladium and rhodium nanoparticles as active phases, impregnated on an inorganic oxide substrate, CeO₂/ZrO₂ (75%, 25%). The aim of PROMETHEUS catalyst’s development is the substitution of a significant amount (85%) of Platinum Group Metals (PGMs) with copper nanoparticles while, at the same time, presenting high catalytic efficiency with respect to the commercial catalysts. In this work, an extensive investigation of the catalytic activity of full scale PROMETHEUS fresh and aged catalyst deposited on ceramic cordierites is presented and discussed. The catalytic activity was tested on an Synthetic Gas Bench (SGB) towards the oxidation of CO and CH₄ and the reduction of NO. The loading of the washcoat was 2 wt% (metal content) on Cu, Pd, Rh with the corresponding metal ratio at 21:7:1. The concentration of the full-scale monolithic catalysts to be 0.032% total PGM loading for meeting Euro III standard and 0.089% for meeting Euro IV to Euro VIb standards. The catalytic activity of all catalysts was tested both in rich-burn (λ = 0.99) and lean-burn conditions (λ = 1.03). Full article

According to the strict European exhaust emissions standards that have been imposed by European legislation there is an elevated need for the decrease of the toxic gas emissions from vehicles. Therefore, car manufacturers have implemented a series of catalytic devices in the aftertreatment of the engine to comply with the standards. All catalytic devices (such as three-way catalysts, diesel particulate filters and diesel oxidation catalysts) accumulate concentrated loading of platinum group metals (PGMs, platinum, palladium, rhodium) as the active catalytic phase. Thus, the demand for PGMs is constantly increasing with a subsequent increase in their market prices. As a result, the research on catalytic converters of high activity and reduced cost/PGM loading is of great interest. In the present work, the Prometheus catalyst, a polymetallic nanosized copper-based catalyst for automotive emission control applications, is presented in two different metal loadings (2 wt% and 5 wt%) and metal ratios (Cu/Pd/Rh = 21/7/1 and Cu/Pd/Rh = 21/7/3). For the first time, a three-metal (copper, palladium, rhodium) nano-catalyst has been synthesized and characterized on a large scale. By using copper as an active catalytic phase, a reduction of PGMs loading is achieved (up to 85%) resulting in a novel catalytic device with similar or improved catalytic performance compared to commercial ones. The Prometheus catalyst is prepared by a wet impregnation method, using as a carrier an inorganic mixed oxide (CeZrO₄) exhibiting elevated oxygen storage capacity (OSC). The heterogeneous catalytic powders produced were characterized by both spectroscopic and analytical methods. The metal content and ratio were determined by inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence (XRF) and energy-dispersive X-ray spectroscopy (EDS). The morphology and the catalyst particle size were determined with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The investigation revealed homogeneous particle formation and dispersion. The deposition of the metal nanoparticles on the porous inorganic carrier was verified with N₂ sorption. Catalytic performance and reactivity of a catalyst (pure wash coat) with molar ratio 21/7/1 and a full-scale Prometheus catalyst with the desired loading of 15 g/ft³ were tested on an in-house synthetic gas bench (SGB) for the abatement of CO, CH₄ and NO, both presenting high catalytic activity. Full article

CuO-CeO₂ nanocatalysts with varying CuO contents (1, 5, 9, 14 and 17 wt %) were prepared by one-step flame spray pyrolysis (FSP) and applied to CO oxidation. The influences of CuO content on the as-prepared catalysts were systematically characterized by X-ray diffraction (XRD), N₂ adsorption-desorption at −196 °C, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and hydrogen-temperature programmed reduction (H₂-TPR). A superior CO oxidation activity was observed for the 14 wt % CuO-CeO₂ catalyst, with 90% CO conversion at 98 °C at space velocity (60,000 mL × g⁻¹ × h⁻¹), which was attributed to abundant surface defects (lattice distortion, Ce³⁺, and oxygen vacancies) and high reducibility supported by strong synergistic interaction. In addition, the catalyst also displayed excellent stability and resistance to water vapor. Significantly, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) showed that in the CO catalytic oxidation process, the strong synergistic interaction led readily to dehydroxylation and CO adsorption on Cu⁺ at low temperature. Furthermore, in the feed of water vapor, although there was an adverse effect on the access of CO adsorption, there was also a positive effect on the formation of fewer carbon intermediates. All these results showed the potential of highly active and water vapor-resistive CuO-CeO₂ catalysts prepared by FSP. Full article

Alloying Pd with Cu is important for catalytic reactions such as denitrification reaction and CO oxidation reaction, but understanding of the catalyst preparation and its correlation with the catalyst’s activity and selectivity remains elusive. Herein, we report the results of investigations of the preparation of PdCu alloy nanocatalysts using different methods and the catalytic properties of the catalysts in catalytic denitrification reaction and CO oxidation reaction. PdCu alloy nanocatalysts were prepared by conventional dry impregnation method and ligand-capping based wet chemical synthesis method, and subsequent thermochemical activation as well. The alloying characteristics depend on the bimetallic composition. PdCu/Al₂O₃ with a Pd/Cu ratio of 50:50 was shown to exhibit an optimized hydrogenation activity for the catalytic denitrification reaction. The catalytic activity of the PdCu catalysts was shown to be highly dependent on the support, as evidenced by the observation of an enhanced catalytic activity for CO oxidation reaction using TiO₂ and CeO₂ supports with high oxygen storage capacity. Implications of the results to the refinement of the preparation of the alloy nanocatalysts are also discussed. Full article