Composition and humidity affect CO oxidation on oxide catalysts. We present an in-situ study for the CO catalytic oxidation by Co3O4 and modified by Mn forming CoMn2O4 spinel-type catalysts under controlled humidity, using near-ambient pressure X-ray Photoelectron Spectroscopy (NAP-XPS). The catalyst samples were prepared as thin films grown on MgO (100) substrates. Surface morphology characterization indicated low surface roughness (< 1.7 nm) with flat shape regardless of catalyst composition. The addition of Mn into Co3O4 films results in the formation of a range of active cationic species (Mn2+, Mn3+ and Mn4+). Based on in-situ NAP-XPS experiments, we observed under dry conditions that the presence of Mn favored CO oxidation into CO2 by increasing the concentration of oxidized cations which served as adsorption sites for CO molecules. Moreover, it was identified that surface adsorbed oxygen takes part in the reaction, finding its consumption is preferred at low reaction temperatures. In the presence of humidity, the CO2 production rate decreased significantly due to competition between CO and H2O molecules for the same adsorption sites. These findings and analysis methodologies represent a simple way to obtain useful information of surface catalysts for future design of catalysts applied in the oxidation of gas pollutants.

Magnesium-based materials are promising candidates for solid-state hydrogen storage due to their high gravimetric capacity; however, their practical application is limited by slow sorption kinetics and high thermal stability. This study investigates the influence of hydride additives on the microstructure and hydrogen desorption performance of ball-milled Mg–Co composites. Flake-like magnesium particles modified with 7 wt.% cobalt were processed by high-energy ball milling and subsequently doped with sodium hydride, potassium hydride, and calcium hydride at concentrations of 0.5 and 5 wt.%. Microstructural, phase, and surface chemical characterization revealed that additive type strongly affects dispersion, interfacial distribution, and the formation of additive-derived surface species within the Mg–Co matrix. Hydrogen sorption measurements conducted at 300–350 °C under different pressure conditions show that alkali hydrides significantly enhance low-temperature hydrogen desorption. In particular, the composite containing 5 wt.% potassium hydride exhibits a marked improvement, releasing approximately 4 wt.% hydrogen at 300 °C, while the unmodified material shows negligible desorption under the same conditions. Thermal analysis confirms that the additives modify the dehydrogenation response, although improved performance is not solely correlated with lower onset temperatures. The results demonstrate a clear asymmetry between hydrogen absorption and desorption, indicating that the primary effect of hydride additives is an enhancement in dehydrogenation kinetics. This behavior is associated with microstructural features, including additive dispersion and interfacial effects induced during processing. These findings provide insight into the design of magnesium-based hydrogen storage materials through microstructure–property relationships.

In this work, the synergistic effect of Mn and Co cations in spinel-type mixed oxides supported on a threedimensionally ordered macro- and mesoporous (3DOM)-Al2O3 has been evidenced in the catalytic oxidation reaction in a dilute gas phase of toluene. A series of Co-Mn mixed oxide nanoparticles (10 wt%) with different Co/Mn atomic ratios of 0.5, 1, and 2 supported on large surface area 3DOM-Al2O3 were synthesized by the incipient wet impregnation method. The microstructural characterization by XRD, HR-TEM and Raman spectroscopy confirmed a structural phase transition from cubic (Fd-3 m) to tetragonal (I41/amd) with increasing Mn content in the spinel-type Co3O4. Moreover, this structural transition was accompanied by an increase in reducible surface sites as evidenced by H2-TPR and XPS analyses. The synergistic effect of greater content of Co3+, Mn3+ and Mn4+ cations on the catalyst surface during Mn incorporation plays a crucial role in optimizing catalyst performance. This can be attributed to the site distribution of these cations within the catalyst structure. Specifically, the presence of lower Mn content favored the Mn2+ cations into tetrahedral sites, while higher Mn content promoted Mn3+ and Mn4+ ions into octahedral sites substituting the Co3+. This distribution pattern favored the formation and recovery of oxygen vacancies, consequently exposing a greater number of reactive oxygen species (O alpha). This improvement in the catalytic efficiency of the nanoparticles supported on 3DOM-Al2O3 is evidenced by the reduction of the T90 of about 250 degrees C for the 0.5 Co/Mn ratio catalyst after recycling, making these catalysts promising candidates for catalytic applications in the abatement of environmental pollutants.

In this study, a carbonaceous material was obtained from the thermal decomposition of a non-pretreated rice husk in a pyrolysis system with controlled nitrogen at 700, 800, 900, and 1000 °C. The characterization of the material was performed using various analytical techniques. The results of these characterizations indicate that the obtained carbonaceous material can achieve a surface area of 450 m2/g, with a microporous volume of 0.15 cm3/g. Furthermore, the presence of oxygenated function groups, predominantly hydroxyl (C-OH) and epoxy (C-O-C), along with amorphous silicon, was identified. Additionally, the material's CO2 adsorption capacity was assessed, revealing a maximum capacity of 1.0 mmol/g. The findings of this study suggest that the CO2 adsorption effectiveness can be impacted by the presence of specific functional groups. These groups have been shown to enhance the material's affinity for CO2, along with its porosity and surface area. In this sense, a notable correlation was identified between the oxygenated function group content and CO2 adsorption capacity. Also, the adsorption isotherm modeling showed an excellent fit to the Langmuir model, indicating monolayer adsorption on a homogeneous surface.

Producing nanosized zeolites Y has been restricted to a Si/Al ratio lower than 2.0, requiring prolonged crystallization periods. This study employed temperature ramps during nucleation and crystallization to synthesize nanosized zeolites Y with a Si/Al ratio of 2.4, ranging from 47 to 100 nm, in just one day. Sequential post-synthesis desilication and dealumination treatments were used to modify the pore structure and acidity of the zeolites, leading to hierarchical zeolite formation. These modifications enhanced the structural stability and porosity of the zeolites while preserving their high crystallinity. Desilicated zeolites, unlike dealuminated ones, possessed straighter and more uniform mesoporous within their crystals, with diameters smaller than 5 nm. Additionally, successive desilication produced a greater number of intracrystalline mesoporous. The solids obtained from both processes exhibited porosity within the zeolite structure connected to the external surface, potentially improving the mass transfer limitations of the original zeolite due to the lack of mesoporous. Catalysts were prepared using modified nanozeolites for evaluation in the propylene oligomerization reaction. Catalysts based on dealuminated and desilicated nanosized zeolite Y showed high conversions above 20

The combination of a commercial zeolite A (ZA, an affordable and highly available material) with peroxymonosulfate (PMS, at mu mol L- 1 levels) for treating several organic pollutants in water was explored herein. Firstly, the ability of the PMS/ZA combination to degrade three model compounds in distilled water, to understand the fundamental aspects of action routes, was tested. It was found the participation of adsorption on ZA, oxidation by PMS, plus the generation and action of 1O2. After evaluating the model substances, the treatment of actual effluent from a municipal wastewater plant (EMWTP) was studied. The EMWTP contained eighteen relevant pharmaceuticals, whose environmental risk (employing the parameters of occurrence, bioaccumulation potential, and quotient risk for the mixture) was initially assessed. Afterward, the treatment of the EMWTP was studied, paying attention to the removal of target pharmaceuticals, color, and phytoxicity. The adsorption of the pharmaceuticals on the ZA alone led to a moderate removal due to its hydrophilic nature and low surface area. Also, PMS induced direct oxidation of some pharmaceuticals having highly reactive moieties (e.g., reduced forms of nitrogen and sulfur and activated benzene rings). In turn, the PMS/ZA system was very efficient for the elimination of most target pharmaceuticals. Also, this combined system led to the color removal and decreased phytotoxicity of the treated EMWTP. The results from this research revealed the high feasibility of the process based on accessible zeolites and PMS for the effective degradation of relevant organic pollutants and mitigation of environmental risks in actual wastewater effluents.

Zeolites are typically used as adsorbents for the removal of organic pollutants from water but recently are gaining attention as catalysts for the activation of persulfates toward contaminants degradation. In this work, the capability of a zeolite Y (FAU-type) and two zeolites beta (BEA-type) to activate peroxymonosulfate (PMS) toward the degradation of one representative pollutant of a pharmaceutical nature (i.e., ciprofloxacin) was tested and compared. Initially, the characterization of the considered zeolites was carried out, evidencing that they had different Si/Al, surface area, and basicity. Then, the main degradation pathway involved in the target pollutant degradation was determined and the activating ability of three zeolites was compared. It was found that among the three tested materials, zeolite Y had the highest activating capability toward PMS for ciprofloxacin degradation (showing 90

In the field of hydrocracking reactions, achieving optimal middle distillate yields remains a persistent challenge with commercially available zeolite Y catalysts. This limitation is attributed to challenges related to diffusion constraints within the catalyst. In response, we present a promising solution not only to these problems but also to the challenges encountered in nanosized Y zeolites when attempting to generate acidic sites within their structure and when analyzing their performance in vacuum gas oil hydrocracking. NiMo catalysts based on nanosized Y zeolites with different crystal sizes exchanged with lanthanum, effectively address diffusion issues and significantly enhance catalyst performance compared to dealuminated nanosized and commercial Y zeolite under the same reaction conditions. The catalysts were characterized by TGA, ICP-OES, XPS, N2 physisorption, FT-IR for pyridine acidity, TEM-mapping, and the 3-methyl thiophene reaction to test the hydrogenating capacity. Surface analysis and microscopy showed greater porosity in the catalysts with smaller zeolites and different arrangements of their components. The catalysts based on steamed protonated nanosized Y zeolites with a larger size and lanthanide nanosized Y zeolite with a smaller size yielded more middle distillates. Research provides a comprehensive analysis, providing a correlation between the catalytic performance and the size of the nanosized Y zeolite.

The dependence of the mesoporous structure (mp) on the catalytic performance of Ni/CeO2-mp and Ni/CeO2-La2O3-mp was evaluated for high-quality mesoporous materials prepared from an SBA-15 template. The samples were characterized by different analytical techniques followed by the catalytic evaluation in a fixed bed reactor (GHSV 36,000 h(-1)). From these results, ceriamesoporous samples (CeO2-mp) showed a highly ordered pore system with assemblies of slitshaped mesopores, and a moderate improvement in CO2 conversion to CH4 due to the presence of basic sites for the Ni/CeO2-La2O3-mp. Subsequently, the influence of the mp-structure on their reactivity was investigated by evaluating the Ni-0 and Ni2+-CeO2 active sites for CO2 methanation from in-situ NAP-XPS experiments as a function of both chemical environment (CO2/H-2) and operating temperature (up to 350 degrees C). The results highlighted the critical role of mesopores in maintaining the proper balance of the active species (Ni-0/Ni2+-CeO2 similar to 2.5) that are present on the catalyst surface, leading to enhanced reactivity over a wide range of operating temperatures (250-350 degrees C) compared to conventional ceria supports. Furthermore, it has been demonstrated that this spectroscopic technique provides valuable insights into the concave surface behavior for monitoring reactivity on mesoporous catalysts, allowing us to contribute to the advancement of methanation reaction technology using CO2.

Metal oxide complexes based on Ni, Co, Mo, or W were prepared by a hydrothermal method and layered structures, identified by X-ray diffraction (XRD), were obtained. Subsequently, layered materials were thermally treated with air and H2S/H2 to obtain transition metal sulfide phases. The physicochemical properties of the materials were also determined by chemical analysis by atomic absorption (AA), thermogravimetric (TGA) and differential (DTA) analyses, hydrogen temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), BET surface area measured by nitrogen physisorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). All catalysts were tested in the hydrodesulfurization (HDS) reaction of dibenzothiophene (DBT) at 593 K and 5.5 MPa. The results indicated that the activity of the catalysts is hexavalent metal (Mo and W) dependent. The NiCoMoS catalyst showed the highest activity with a DBT conversion of 96%. Metal oxide complexes based on Ni, Co, Mo, or W were prepared by a hydrothermal method and layered structures, identified by X-ray diffraction (XRD), were obtained.

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The synthesis of submicrometric Y zeolites has only been achieved for a Si/Al ratio lower than 2.0 for long crystallization times. In this work, submicrometric Y zeolites in the range of 100-200 nm were synthesized with a Si/Al ratio equal to 2.4 in just 24 h. Post-synthesis methods allow tuning the porosity and the acidity of the microporous Y zeolites leading to hierarchical zeolites. Hierarchical Y zeolites were obtained by post-synthetic modification of submicrosized Y zeolites, synthesized under organic template-free conditions. The influence of the post-synthetic modification on the structure, particle size, morphology, surface area and acidic properties of the zeolites was studied. The post-synthetic modification involved either sequential desilication-dealumination (DES-DEA) or sequential dealumination-desilication (DEA-DES) of the zeolite framework involving both leaching with NaOH and steaming processes. Structurally more stable zeolites with hierarchical porosity and high crystallinity were synthesized by the sequential DES-DEA process proposed in this work. Sequential DES-DEA process allowed two relevant results in applications of these zeolites for catalysis. On one hand, it allowed a more ordered and controlled dealumination which led to retaining the number of Bronsted acid sites when the NaOH concentration was changed. Characterization of surface acidity revealed protection of the structural aluminum due to the first step of desilication before the dealumination. On the other hand, this method produced simultaneously both intraparticle and interparticle mesoporosity. With the obtained zeolites, NiMo catalysts were prepared and evaluated in the vacuum gas oil hydrocracking reaction. The catalysts based on zeolites obtained by DES-DEA were more active at lower temperatures and exhibited higher yields of middle distillates compared to those obtained with zeolites synthesized by the DEA-DES method. The desilication-dealumination process allowed the production of structurally more stable submicrometric Y zeolites with hierarchical porosity and high crystallinity.

In this work, Ni -based mixed metal oxide (MMOs) materials were synthesized by coprecipitation, and then ceria (CeO2) was incorporated. The obtained structures were characterized by XRD, TEM, BET, H-2-TPR, and CO2-TPD techniques. The synthesized materials were evaluated in the CO2 methanation process (250-400 degrees C range). Firstly, the effects of space velocity and Ni loading on the catalyst were tested, and 36000 h(-1) and 5 % of Ni were found to be suitable conditions for CO2 conversion. The addition of Co or Fe to the Ni-based MMO was then assessed. Co improved the catalytic activity, meanwhile, the Fe addition did not have an enhancing effect. Afterward, the role of CeO2 as support on Ni-, NiFe- and NiCo-based MMOs was evaluated, evidencing that selectivity and space-time yields were enhanced in the materials by the CeO2 presence. Furthermore, due to the characteristics of CeO2, the MMO containing nickel, cobalt, and ceria was more stable, showing similar to 85% conversion of CO2 after 1400 min of continuous use.

Water pollution by pharmaceuticals is a current worrying environmental problem. Adsorption and catalytic processes using zeolites have been employed in several studies to remove/degrade pharmaceuticals from water. The interest of researchers in these two strategies based on the utilization of zeolites (i.e., adsorption and advanced oxidation technologies, AOT) is continuously growing. Then, this work presents a literature review, considering the origin of the zeolites (natural vs. synthetic) and the modifications of zeolites (e.g., the addition of surfactants) for the adsorption of diverse pharmaceuticals. The role of zeolites in catalytic ozonation, Fenton-based systems, and activation of peroxymonosulfate and peroxydisulfate is detailed. Also, the primary transformations of pharmaceuticals induced by these AOTs were examined. Moreover, the gaps regarding biodegradability and toxicity of the transformation products coming from the degradation of pharmaceuticals by the zeolites-based processes were discussed. To overcome the scarcity of information regarding the biodegradability and toxicity of the primary transformation products observed in the revised works, an initial approach to these topics, using a predictive tool, was made. Finally, from the present review, it was evidenced the need for future works involving zeolites that provide results about the simultaneous removal/elimination of multiple pharmaceuticals in complex matrices (e.g., hospital wastewater or municipal wastewater), new information about biodegradability and toxicity plus the development of combination or coupling of processes with other AOTs (e.g., sonochemistry) or classical systems (e.g., biological process).

Mid-high-frequency ultrasound (200–1000 kHz) eliminates organic pollutants and also generates H2O2. To take advantage of H2O2, iron species can be added, generating a hybrid sono-Fenton process (sF). This paper presents the possibilities and limitations of sF. Heterogeneous (a natural mineral) and homogeneous (Fe2+ and Fe3+ ions) iron sources were considered. Acetaminophen, ciprofloxacin, and methyl orange were the target organic pollutants. Ultrasound alone induced the pollutants degradation, and the dual competing role of the natural mineral (0.02–0.20 g L−1) meant that it had no significant effects on the elimination of pollutants. In contrast, both Fe2+ and Fe3+ ions enhanced the pollutants’ degradation, and the elimination using Fe2+ was better because of its higher reactivity toward H2O2. However, the enhancement decreased at high Fe2+ concentrations (e.g., 5 mg L−1) because of scavenger effects. The Fe2+ addition significantly accelerated the elimination of acetaminophen and methyl orange. For ciprofloxacin, at short treatment times, the degradation was enhanced, but the pollutant complexation with Fe3+ that came from the Fenton reaction caused degradation to stop. Additionally, sF did not decrease the antimicrobial activity associated with ciprofloxacin, whereas ultrasound alone did. Therefore, the chemical structure of the pollutant plays a crucial role in the feasibility of the sF process.

A chromate of copper and cobalt (Φy) was synthesized and characterized. Φy activated peroxymonosulfate (PMS) to degrade ciprofloxacin (CIP) in water. The Φy/PMS combination showed a high degrading capability toward CIP (~100% elimination in 15 min). However, Φy leached cobalt (1.6 mg L−1), limiting its use for water treatment. To avoid leaching, Φy was calcinated, forming a mixed metal oxide (MMO). In the combination of MMO/PMS, no metals leached, the CIP adsorption was low (<20%), and the action of SO4•− dominated, leading to a synergistic effect on pollutant elimination (>95% after 15 min of treatment). MMO/PMS promoted the opening and oxidation of the piperazyl ring, plus the hydroxylation of the quinolone moiety on CIP, which potentially decreased the biological activity. After three reuse cycles, the MMO still presented with a high activation of PMS toward CIP degradation (90% in 15 min of action). Additionally, the CIP degradation by the MMO/PMS system in simulated hospital wastewater was close to that obtained in distilled water. This work provides relevant information on the stability of Co-, Cu-, and Cr-based materials under interaction with PMS and the strategies to obtain a proper catalyst to degrade CIP.

Zeolite 4A (Z4A), synthesized from natural kaolin by an easy and low-cost method, was used to activate inorganic peroxides for degrading organic pollutants in water. Z4A had a high catalytic capability for the activation of peroxymonosulfate (PMS) but a low effect on peroxydisulfate (PDS) or hydrogen peroxide (H2O2). The non-radical pathway dominated the degradation of the pollutants, due to acid-base interactions of PMS with Z4A, as indicated by the characterization of the fresh and used zeolite. Additionally, in the Z4A/PMS system, synergistic effects in the elimination of two representative contaminants (ciprofloxacin “CIP” and methyl orange “MO”) were observed. The Z4A/PMS system induced the opening of the piperazyl ring of CIP, and the cleavage of the azo-benzene bond of MO. These primary transformations occurred in electron-rich groups, as supported by theoretical analyses on atomic charge developed herein. Interestingly, Z4A showed high activating/degrading capability even after three reuse cycles without the involvement of the typical recycling steps (filtration, washing, and drying) for a solid recovery. Furthermore, when compared with a sonochemical process, the Z4A/PMS system was highly efficient and more selective for the degradation of both CIP in synthetic fresh urine and MO in simulated textile wastewater. This study offers relevant findings on the PMS activation toward the non-radical pathway using the zeolite 4A, which represents an interesting alternative to those materials composed of transition metals or carbonaceous structures, to treat organic pollutants in aqueous samples in a selective way.

Nanosized Y zeolite is a material which could potentially be used as an adsorbent or catalyst in the oil industry thanks to its increased high external area and mesopore volume. However, a simple, inexpensive, and environmentally friendly method to synthesize this zeolite has not yet been reported. Currently, the synthesis methods used to obtain nanosized Y zeolite are based on the use of organic structure-directing agents, since the zeolites obtained without these compounds have low Si/Al ratios. Based on these considerations, in this work nanosized Y zeolites were synthesized with high crystallinity and Si/Al ratios between 1.5 and 2.6, without the use of organic compounds and in a relatively short time (3 days). The study focuses on understanding the variation in the crystallization temperature when the amount of sodium aluminate, silica and sodium hydroxide is modified in the synthesis and correlates this variation with the Si/Al ratio and the particle size of the resulting zeolite.

Nanocomposites of nickel oxide/yttria-stabilized zirconia (NiO/YSZ) particles were synthesized via solution combustion synthesis using glycine and urea as fuels in one step. The powders were characterized by X-ray diffraction (XRD) analysis, where the synthesis with urea showed the formation of the NiO/YSZ composite, while the presence of Ni with NiO/YSZ were observed when the glycine was used. The morphology of the as-prepared powders and the presence of Ni were corroborated by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy (FE-SEM; EDX). The powders showed catalytic behavior which was evidenced by H2-TPR measurements. These materials could be used for the fabrication of Ni/YSZ anode for fuel cells.