Surface Formate Research Articles

Deciphering rock surface origins in a karst cave: insights from the Rača Cave, Lastovo, Croatia

This paper outlines a comprehensive fieldwork methodology for discerning the origin of rock surfaces within a karst cave environment. This methodology is particularly utilized in a cave with breakdown morphology. Using Rača Cave in Lastovo, Croatia as a case study, we explore geological and morphological features through advanced surface analysis. The approach involves meticulous measurement of rock discontinuities, joint patterns, and surface formations. Cost-efficient and time-efficient data collection and processing during field-work were undertaken with FieldClino Move and Polycam applications on smartphones. Visualization techniques were employed to elucidate the interplay between erosion, deposition, and speleogenetic processes.

Concurrent Amorphization and Nanocatalyst Formation in Cu-Substituted Perovskite Oxide Surface: Effects on Oxygen Reduction Reaction at Elevated Temperatures.

The activity and durability of chemical/electrochemical catalysts are significantly influenced by their surface environments, highlighting the importance of thoroughly examining the catalyst surface. Here, Cu-substituted La0.6Sr0.4Co0.2Fe0.8O3-δ is selected, a state-of-the-art material for oxygen reduction reaction (ORR), to explore the real-time evolution of surface morphology and chemistry under a reducing atmosphere at elevated temperatures. Remarkably, in a pioneering observation, it is discovered that the perovskite surface starts to amorphize at an unusually low temperature of approximately 100 °C and multicomponent metal nanocatalysts additionally form on the amorphous surface as the temperature raises to 400 °C. Moreover, this investigation into the stability of the resulting amorphous layer under oxidizing conditions reveals that the amorphous structure can withstand a high-temperature oxidizing atmosphere (≥650 °C) only when it has undergone sufficient reduction for an extended period. Therefore, the coexistence of the active nanocatalysts and defective amorphous surface leads to a nearly 100% enhancement in the electrode resistance for the ORR over 200 h without significant degradation. These observations provide a new catalytic design strategy for using redox-dynamic perovskite oxide host materials.

Design and Understanding of Adaptive Hydrogenation Catalysts Triggered by the H2/CO2-Formic Acid Equilibrium.

An adaptive catalytic system for selective hydrogenation was developed exploiting the H2+CO2HCOOH equilibrium for reversible, rapid, and robust on/off switch of the ketone hydrogenation activity of ruthenium nanoparticles (Ru NPs). The catalyst design was based on mechanistic studies and DFT calculations demonstrating that adsorption of formic acid to Ru NPs on silica results in surface formate species that prevent C═O hydrogenation. Ru NPs were immobilized on readily accessible silica supports modified with guanidinium-based ionic liquid phases (Ru@SILPGB) to generate in situ sufficient amounts of HCOOH when CO2 was introduced into the H2 feed gas for switching off ketone hydrogenation while maintaining the activity for hydrogenation of olefinic and aromatic C═C bonds. Upon shutting down the CO2 supply, the C═O hydrogenation activity was restored in real time due to the rapid decarboxylation of the surface formate species without the need for any changes in the reaction conditions. Thus, the newly developed Ru@SILPGB catalysts allow controlled and alternating production of either saturated alcohols or ketones from unsaturated substrates depending on the use of H2 or H2/CO2 as feed gas. The major prerequisite for design of adaptive catalytic systems based on CO2 as trigger is the ability to shift the H2+CO2HCOOH equilibrium sufficiently to exploit competing adsorption of surface formate and targeted functional groups. Thus, the concept can be expected to be more generally applicable beyond ruthenium as the active metal, paving the way for next-generation adaptive catalytic systems in hydrogenation reactions more broadly.

Environmental water-mediated dual-mechanism regulation of PtCuδ-MnOx-catalyzed acetone oxidation: Enhancement of MvK and inhibition of L-H mechanism

Environmental H2O has a significant effect on the reaction mechanism and process of VOC oxidation, of which the intrinsic mechanism is hardly reported. Herein, a series of PtCuδ-MnOx catalysts with different strong metal-supported interactions were constructed by replacing some Pt species with Cu species. Among them, the PtCu3-MnOx catalyst exhibited superior catalytic performance (T90 = 170 ℃), high water resistance, and long-term stability. Furthermore, in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTs) showed that the acetone oxidation followed synergistic cooperation of the Langmuir-Hinshelwood (L-H) and Mars van Krevelen (MvK) mechanism. Acetone oxidation over PtCu3-MnOx occurred via the L-H mechanism producing surface acetate and formate species intermediate. Above 100 °C, adsorbed acetone (i.e., acetate and formate species) reacts with MnOx lattice oxygen according to the MvK mechanism to form CO2 and H2O. When water vapor was present, the L-H mechanism was impaired, inhibiting the deep oxidation of acetone. This research provides an in-depth exploration of how water vapor impacts the reaction mechanism of acetone oxidation. It offers valuable insights for creating dependable catalysts suitable for use in various industrial settings.

Ba2+ doping into Ni/Al2O3 nanofibers promotes CO2 methanation via alkaline modulation

Ni-based catalysts are promising catalysts for CO2 methanation due to low lost. However, the activity and selectivity of Ni-based catalysts in CO2 methanation at low temperatures still need to be improved. Here, Ni4Al2BamOx (m = 0–0.5) nanofibers were prepared. Doping Ba2+ would increase alkaline sites and facilitate generating oxygen vacancies. Especially, Ni4Al2Ba0.2Ox exhibited the high specific surface area with 127.1 m2 g−1, being potential for exposing more active sites. Indeed, compared with undoped Ni4Al2Ox catalysts (CO2 conv. = 45 %, CH4 select. = 92 % at 300 °C), Ba2+ doping significantly improved activity (CO2 conv. = 74 %, CH4 select. = 99 % at 300 °C) and stability within 200 h for Ni4Al2Ba0.2Ox. Both EPR and O1S XPS confirmed that Ni4Al2Ba0.2Ox can form more oxygen vacancies and CO2-TPD confirmed that Ni4Al2Ba0.2Ox had stronger CO2 adsorption capacity compared to Ni4Al2Ox. In-situ infrared spectroscopy and DFT calculations both indicated that Ba2+ doping can promote generating surface hydroxyl groups and formate pathways.

Natural elicitors enhanced suberin polyphenolic accumulation in wounded potato tuber tissues.

Unintended wounding or bruising during harvest or postharvest handling leads to significant tuber loss and imposes economic burden to potato industry. Therefore, finding effective strategies to mitigate wound-related tuber losses is very important from industry perspectives. Formation of protective barrier through accumulation of suberin polyphenolics (SPP) is a natural and initial response of potato tuber tissues to wounding. In this study, efficacy of two natural elicitors, such as chitosan oligosaccharide (COS 0.125 g L-1) and cranberry pomace residue (Nutri-Cran 0.125 g L-1) was investigated using a mechanically wounded tuber tissue model and by histological determination of SPP formation in five agronomically relevant and red-skin potato cultivars (Chieftain, Dakota Rose, Dakota Ruby, Red LaSoda, Red Norland). Furthermore, the potential role of stress protective metabolic regulation involving phenolic metabolites, proline, and antioxidant enzymes in tuber WH processes were also investigated during 0-9 days after wounding. Exogenous treatments of both COS and Nutri-Cran resulted into enhanced SPP formation in wounded surface, but the impact was more rapid with Nutri-Cran treatment in select cultivars. Greater contents of total soluble phenolic, ferulic acid, chlorogenic acid, total antioxidant activity, and superoxide dismutase activity were also observed in elicitor treated tuber tissues at different time points after wounding. Nutri-Cran treatment also reduced the activity of succinate dehydrogenase in Red Norland and Dakota Ruby at 3 d, indicating a suppression in respiration rate. Collectively, these results suggest that Nutri-Cran can be potentially utilized as an effective WH treatment to potato tubers for minimizing wound-related losses.

EDM machining effectiveness for Ti–6Al–4V alloy using Cu–TiB2 ceramic composite electrode: a parametric evaluation

The study addresses the requirement for better machining of titanium alloy (Ti–6Al–4V) in Electrical Discharge Machining (EDM) with a Cu–TiB2 ceramic composite powder metallurgy electrode. The electrode underwent analysis for relative density, hardness, and microstructure using field emission scanning electron microscopy and X-ray diffraction. Results indicated a relative density of approximately 90.08%, a microhardness of around 142 H V, and an electrical conductivity of 46% IACS. Response Surface Methodology (RSM) was used as Design of Experiment (DoE) technique for this study to investigate the effects of pulse current (Ip), pulse on time (Ton), and discharge voltage (V) on Material Removal Rate (MRR) and Surface Roughness (SR). Analysis of variance (ANNOVA) at a 5% significance level highlights the significant impact of Ip, Ton & V, and the interaction between selected parameter on MRR and SR. Results show a significant influence of pulse current (Ip) and pulse duration (Ton) on both MRR and SR. Rising pulse current correlates with improved MRR, with optimal parameters identified as a pulse current of 15 A, a pulse on time of 150 μs, and a voltage of 50 V. The study also looks into the usage of reverse polarity to improve surface finish compared to typical EDM methods. The use of Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) analyses adds depth to the evaluation of surface formations on the workpiece. EDS analysis indicates the presence of 63.13 wt (%) of boron on the machined work surface, affirming the effectiveness of the developed Cu–TiB2 electrode in machining titanium alloy.

Antibacterial mode of action of garviecin LG34 against Gram-negative bacterium Salmonella typhimurium.

Garviecin LG34 produced by Lactococcus garvieae LG34 exhibits wide-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria. This work aimed at clarifying the antibacterial mode of action of garviecin LG34 against Gram-negative bacterium Salmonella typhimurium. To determine the concentration for the bacteriocin antimicrobial mode experiments, the minimum inhibitory concentration of garviecin LG34 against S. typhimurium CICC21484 was determined as 0.25mg/ml. Garviecin LG34 decreased the viable count of S. typhimurium CICC21484 and its antibacterial activity was the dose and time dependant. Garviecin LG34 led to the dissipation of transmembrane potential, the rise in the extracellular conductivity, UV-absorbing material at 260nm, and LDH level of S. typhimurium CICC21484. Scanning electron micrographs results shown that garviecin LG34 cause dramatic deformation and fragmentation including the flagellum shedding, pores formation in surface, and even completely breakage of S. typhimurium cell. Moreover, garviecin LG34 decreased the intracellular ATP level. The results of this study demonstrated that garviecin LG34 can destroy cell structure, increase membrane permeability of S. typhimurium, thereby might be used as biopreservative for treating food borne and salmonellosis resulting from Gram-negative bacterium S. typhimurium.

Analysis of carbon dioxide disposal methods to reduce greenhouse gases

The practice of capturing, storing and utilizing CO2 is becoming key to developing sustainable energy and industrial solutions. The technology promotes the use of fossil fuels, which remain the predominant source of energy worldwide. The effectiveness of the technology is evident in the reduction of CO2 levels in the atmosphere, a significant contribution to the reduction of global greenhouse gas (GHG) emissions and the fight against climate change. However, a notable concern in the realm of geological storage revolves around the potential leakage of CO2 from storage reservoirs. Carbon dioxide has the capability to migrate from the storage site, reaching both the surface and underground formations. Surface leakage presents health risks to humans, animals, and plants. The solution to this problem requires a detailed approach and should be solved through an inverse problem, in which pressure measurements in monitoring wells will be performed frequently to obtain information about the reservoir and possible leaks. Additionally, there are a number of issues with carbon dioxide leakage during oil and gas extraction, as well as various operations at fields. Emphasizing the monitoring of CO2 leakage, this paper underscores the importance of developing an algorithm designed to proactively prevent CO2 leakage in aquifers and depleted reservoirs. Such an initiative is pivotal in the broader context of mitigating greenhouse gas emissions. The paper offers an overview of methodologies for effective monitoring, management and modeling of CO2 leakage and practical approaches to calculation and assessment, contributing to a more complete understanding of the challenges associated with CO2 storage.

Investigation of the role of oxygen vacancies in CuZn catalysts for the formation of higher alcohols from syngas

The catalytic conversion of syngas to higher alcohols (C2+OH) has drawn widespread attention because it can alleviate the oil crisis and realize the clean and efficient use of coal. Nevertheless, the seesaw problem between C2+OH and total alcohol selectivity has not been solved. In recent years, catalytic processes involving oxygen vacancies have been widely investigated. However, the existing literature on this topic is fragmentary and unsystematic. Herein, we report a significant improvement in C2+OH synthesis by varying the oxygen vacancies on CuZn catalysts and systematically elaborate the structural and catalytic effects of the oxygen vacancies. Oxygen vacancy content shows almost linear positive correlations with many of the physical and chemical properties of the catalysts, such as SBET, Vp, Dp, Cu0 size, H2 consumption, and Cu0/(Cu0 + Cu+) ratio. The presence of oxygen vacancies drives catalysis in two ways. One, the dissociation of water adsorbed on oxygen vacancies causes the formation of hydroxyl groups, which interact with activated CO* to form surface formate (HCOO*) groups. This is followed by successive hydrogenation to form surface CHxO* intermediates. The CHxO* or CO* species are then coupled with surface CHx* to form ethanol on Znδ+ defect sites, realizing the growth of carbon chains. Two, oxygen vacancies drive electron transfer from ZnO to Cu, generating more Znδ+ defects and regulating the Cu0/(Cu0 + Cu+) ratio. The presence of electron-rich Cu is conducive to CO dissociation and adsorption, which promotes the formation of the critical surface intermediate CHx*. Consequently, the optimized CZ-0.80 catalyst exhibits exceptional catalytic performance, achieving 9.98 % CO conversion as well as ethanol and C2+OH proportions of up to 54.27 % and 59.95 %, respectively. Thus, by developing a new catalyst system that avoids the use of F-T elements such as Co or Fe for C2+OH synthesis from syngas, this work provides a new understanding of the growth of carbon chains.

Mechanistic study of integrated CO2 capture and utilization over Cu and Al-modified calcined limestone with high stability using MFB-TGA-MS

This study explores the performance of dual-functional materials (DFMs) in cyclic integrated CO2 capture and reverse water–gas shift (ICCU-RWGS) reactions under fluidized, isothermal conditions. DFMs with a copper catalyst and alumina support on calcined natural limestone were analyzed using micro-fluidized bed thermogravimetric analysis coupled with mass spectrometry (MFB-TGA-MS). The results indicate that the 10 %Cu5%Al-CaO-IMP surpasses others, demonstrating a CO2 capture capacity of 10.67 mmol⋅g−1, 71.5 % in-situ CO2 conversion at 700 °C, and remarkable cyclic stability over 30 cycles. Cu and Al additions curtail CaO agglomeration during extended ICCU-RWGS and enhance CO2 and H2 activation by removing surface formate species, promoting CO production. Furthermore, non-catalytic gas–solid reactions coexist with catalytic gas–solid reactions, leading to gradual Cu particle coating by CaCO3 during carbonation. This phenomenon prevents Cu sintering but slightly reduces catalytic activity. These findings, combined with cost-effective materials (CaO, Cu, Al), hold significant promise for efficient and economically viable ICCU processes.

Grain size effect on the plasma etching behavior of spark plasma sintered yttria-stabilized zirconia ceramics

Yttria-stabilized zirconia (YSZ) ceramics with various grain sizes were fabricated via a spark plasma sintering (SPS), and their plasma etching properties were investigated, particularly focusing on the effect of grain size on plasma etching behavior. All the sintered YSZ ceramics were fully densified (∼99.8 % relative density) and the grain size was varied by controlling the sintering conditions. The plasma etching test was conducted by an inductively coupled plasma (ICP) chamber using CF4. The sintered YSZ ceramics exhibited a low etching rate compared to that of the conventional plasma-resistant materials such as Al2O3 and SiC. The superior plasma erosion resistance of YSZ ceramics can be attributed to the yttrium (Y) enrichment and YF3 formation in the plasma etched surface. Interestingly, the grain size of the YSZ ceramics barely affected the etching depth and mass loss. On the other hand, the surface roughness increased with the increasing grain size. The YSZ ceramics with the large grain size showed a much rough surface after the plasma exposure. The obtained results indicated that the grain size could affect the surface properties of the ceramics during plasma etching, which should be considered when fabricating the future plasma-resistant materials.

Exploring the evidence of Middle Amazonian aquifer sedimentary outburst residues in a Martian chaotic terrain

The quest for past Martian life hinges on locating surface formations linked to ancient habitability. While Mars' surface is considered to have become cryogenic ~3.7 Ga, stable subsurface aquifers persisted long after this transition. Their extensive collapse triggered megafloods ~3.4 Ga, and the resulting outflow channel excavation generated voluminous sediment eroded from the highlands. These materials are considered to have extensively covered the northern lowlands. Here, we show evidence that a lacustrine sedimentary residue within Hydraotes Chaos formed due to regional aquifer upwelling and ponding into an interior basin. Unlike the northern lowland counterparts, its sedimentary makeup likely consists of aquifer-expelled materials, offering a potential window into the nature of Mars' subsurface habitability. Furthermore, the lake’s residue’s estimated age is ~1.1 Ga (~2.3 Ga post-peak aquifer drainage during the Late Hesperian), enhancing the prospects for organic matter preservation. This deposit’s inferred fine-grained composition, coupled with the presence of coexisting mud volcanoes and diapirs, suggest that its source aquifer existed within abundant subsurface mudstones, water ice, and evaporites, forming part of the region’s extremely ancient (~ 4 Ga) highland stratigraphy. Our numerical models suggest that magmatically induced phase segregation within these materials generated enormous water-filled chambers. The meltwater, originating from varying thermally affected mudstone depths, could have potentially harbored diverse biosignatures, which could have become concentrated within the lake’s sedimentary residue. Thus, we propose that Hydraotes Chaos merits priority consideration in future missions aiming to detect Martian biosignatures.

Interface mediated CO2 hydrogenation on inverse supported ZrO2/Ni(1 1 1) nanocluster catalyst

To tune the activity and selectivity of CO2 hydrogenation, inverse supported Zr9O18/Ni(111) catalysts are designed based on ab initio molecular dynamics simulation and density functional theory calculation under the consideration of the number of interfacial O and Zr atoms as well as the interaction between O and Zr atoms. For the most stable catalyst with coordinatively unsaturated interface Zr sites, charge transfer from surface to oxide has been found. The Ni(111) surface is pre-covered by H atoms and the interface Zr sites can activate CO2 to a large extent, and their interaction results in the spontaneous formation of surface formate. Further hydrogenation of surface formate leads to the selective formation of methanol with an apparent Gibbs free energy barrier of 0.62 eV, lower than that of methane formation (1.09 eV). On the contrary to metallic nickel and supported nickel catalysts, the most favoured methanol formation route [HCOO → CHO → CH2O → CH3O → CH3OH] does not involve CO as intermediate, revealing the mediated interface effect.

High‐temperature ablation of hot‐pressed HfC–SiC ceramics

AbstractEffective thermal insulation materials rely on the fabrication of dense, ultra‐high‐temperature ceramics that can withstand harsh environments. Hafnium carbide‐based ceramics are one of the leading materials that have the potential to perform relatively well in high‐temperature oxidizing environments under mechanical loading due to their thermal and mechanical stability. In this study, we explore the effects of processing conditions to create dense, ablation‐resistant HfC–SiC composites with a fixed composition of HfC–20 wt.% SiC using a hot‐pressing method. Sintering pressure, temperature, and time were varied and the material's relative density, phase composition, morphology, microstructure, and hardness were investigated. Composite ceramics with 99% relative density relative to a theoretical value were created by hot pressing at 2100°C for 1 h at 50 MPa and displayed a fine microstructure with an average grain size of ∼5 µm and a Vickers hardness of 22.9 ± .8 GPa. The mass loss was determined using an oxyacetylene torch with cross‐section investigations of oxide surface formations and subsurface microstructural changes. These HfC–SiC samples developed a 410 nm hafnium oxide layer on the surface upon torch exposure and had an average calculated recession rate of .028 µm/s.

Comprehensive Analysis of CdS Ultrathin Films Modified by the Substrate Position inside the Reactor Container Using the CBD Technique.

The cadmium sulfide (CdS) n-type semiconductor is one of the most used as a window layer in thin-film solar cells, such as CdTe, CIS, CIGS, and CZTS. Optoelectronic properties are the most important characteristics for window materials. CdS thin films obtained using the chemical bath deposition technique (CBD) have been reported; however, large amounts of precursor solutions are used, which generate considerable amounts of toxic waste. The aim of this work is to reduce the amount of precursor solutions used for CdS growth; for this, it is necessary to consider an efficient position for the substrate inside the reactor container and at the same time allow obtaining CdS thin films with adequate physical properties to be applied in the photovoltaic solar cell development. CdS thin films were deposited on soda-lime/SnO2:F substrates (FTO) using the CBD technique; the substrates were placed in three different arrangements [rack system, step system (up), and step system (down)]. CdS samples with areas of 4 cm2 and a thickness of 27-48 nm were obtained; the X-ray diffraction patterns show CdS thin films with different polycrystalline structures. The morphological measurements reveal different surface formations depending on the substrate position, and resistivity values of around 105 Ω*cm were measured. UV-vis spectra show transmittance values of around 45-94% in the visible region with band gap energy values of around 2.1-2.36 eV. The best physical properties of CdS thin films and an efficient CBD process were obtained when the FTO substrates were located near the bottom of the reactor container with the FTO side down, leading to an optimal configuration that allows reducing the amount of precursor solutions and in this way reduces the toxic waste generated. These results are important in the photovoltaic technology process and environmental impact.

Preformed Pt Nanoparticles Supported on Nanoshaped CeO2 for Total Propane Oxidation.

Pt-based catalysts have been widely used for the removal of short-chain volatile organic compounds (VOCs), such as propane. In this study, we synthesized Pt nanoparticles with a size of ca. 2.4 nm and loaded them on various fine-shaped CeO2 with different facets to investigate the effect of CeO2 morphology on the complete oxidation of propane. The Pt/CeO2-o catalyst with {111} facets exhibited superior catalytic activity compared to the Pt/CeO2-r catalyst with {110} and {100} facets. Specifically, the turnover frequency (TOF) value of Pt/CeO2-o was 1.8 times higher than that of Pt/CeO2-r. Moreover, Pt/CeO2-o showed outstanding long-term stability during 50 h. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that the excellent performance of Pt/CeO2-o is due to the prevalence of metallic Pt species, which promotes C-C bond cleavage and facilitates the rapid removal of surface formate species. In contrast, a stronger metal-support interaction in Pt/CeO2-r leads to easier oxidation of Pt species and the accumulation of intermediates, which is detrimental to the catalytic activity. Our work provides insight into the oxidation of propane on different nanoshaped Pt/CeO2 catalysts.

Повышение селективности модифицирования спектральных характеристик алмазов перед процессом рентгенолюминесцентной сепарации

Introduction. A promising direction in solving the problem of increasing the recovery of diamonds with weak or anomalous luminescence is the use of modern technologies for modifying the spectral characteristics of diamonds with luminophore-containing reagents. Materials and methods. In the experiments, we used collections consisting of diamond crystals with weak and anomalous luminosity and grains of kimberlite minerals selected from the gravity enrichment concentrate. When evaluating the efficiency of fixing luminophores on the surface of diamonds, a vision-metric method was used in UV radiation with the determination of the proportion of surface areas covered with luminophores. The spectral and kinetic characteristics of diamond crystals and kimberlite grains were measured under laboratory conditions on a «Polus-M» separator. The separation of diamonds and kimberlite grains was carried out in the mode used in the industrial radar process. Results. The causes and regularities of the interaction of modifier reagents with kimberlite minerals, as well as the effect of dispersant reagents on the fixation of luminophores and the spectral and kinetic characteristics of kimberlite are determined. Discussion. It is shown that the fixation of an organic collector with luminophores on kimberlite minerals proceeds according to the adhesion mechanism with the formation of focal surface formations on hydrophobic minerals and point fixation on the surface of faces with low surface energy. It is shown that the high selectivity of the X-ray luminescence separation process is achieved at a surface concentration of the luminophores on diamonds of at least 15 % and a surface concentration of luminophores on kimberlite minerals of no more than 3%, controlled by the addition of reagents-dispersants. Conclusions. The article presents the results of studies of the mechanism and regularities of fixing luminophore-containing compositions on kimberlitic minerals in the presence of dispersant reagents. It was found that the addition of luminophore-containing reagents-modifiers of sodium hexametaphosphate, sulfonol, carboxymethylcellulose and liquid glass to the aqueous phase of emulsions provides an increase in the selectivity of fixing luminophores on the surface of diamonds and improves the performance of X-ray luminescent separation of diamond-containing products. A mode of increasing the selectivity of the action of an aqueous emulsion of the MLA-3 modifier reagent based on luminophore E-515-115-G5 has been developed by adding sodium hexametaphosphate to the emulsion aqueous phase at a concentration of 1-1.5 g/l, providing 90% recovery of weakly and abnormally luminous diamonds into the X-ray luminescent separation concentrate with a decrease in kimberlite yield by 33 %. The tested modifier agents and the selected conditions of their application can be useful in industrial conditions for the X-ray luminescent separation of diamond-containing kimberlites. Resume. As a result of the studies, a mode was developed to increase the selectivity of the action of an aqueous emulsion of the MLA-3 modifier reagent based on the E-515-115-G5 luminophore with the addition of a dispersant reagent (sodium hexametaphosphate) to the aqueous phase of the emulsion at a concentration of 1-1.5 g/l , providing the possibility of 90 % extraction of weakly and abnormally luminous diamonds into the concentrate of X-ray luminescent separation while reducing the yield of kimberlite by 33 %. Suggestions for practical application and direction for future research. The developed reagents-modifiers and the selected conditions for their use are recommended for testing and implementation in industrial conditions.

An investigation of the Ni/carbonate interfaces on dual function materials in integrated CO2 capture and utilisation cycles

CO2 capture and utilisation (CCU) is a promising strategy to effectively mitigate the adverse greenhouse effects caused by CO2 emissions at an industrial scale. Through a process intensification strategy known as integrated CO2 capture and utilisation (ICCU), CO2 capture and catalytic CO2 conversion can be achieved in a single process with the use of dual function materials (DFMs), which are both CO2 sorbents and CO2 conversion catalysts. Given the significantly different operating conditions of ICCU from conventional catalytic CO2 hydrogenation, the catalytic mechanism of DFMs, especially during CO2 hydrogenation, needs to be thoroughly investigated. In this study, the relationship between the nature of the Ni/carbonate interfaces and the performance of Ni-based DFMs over ICCU cycles is systematically investigated. A series of Ni/alkaline earth carbonate DFMs were synthesised with varying Ca:Mg ratios to simulate different metal-carbonate model interfaces. At 400 °C, CH4 formation with nearly 100% CH4 selectivity was achieved on Ni/CaCO3 over 15 ICCU cycles. In general, Ni/CaCO3 interfaces correspond to higher CO2 conversion and higher CH4 selectivity than Ni/MgCO3 interfaces. Such trend may be attributed to the higher surface basicity of CaO and the higher thermal stability of CaCO3. As a consequence, the hydrogenation of the Ni/CaCO3 interface proceed via the formate pathway, in which carbonates are consecutively converted to surface formates, methoxyl, methyl species and eventually desorb as methane. This reaction model is applicable to the hydrogenation of both surface carbonate and bulk carbonates, although the former proceeds with much faster kinetics. On the weakly alkaline Ni/MgCO3 interface, MgCO3 preferentially decomposes to form gaseous CO2, which is subsequently hydrogenated via the reverse-water-gas-shift pathway, with CO as the key reaction intermediate. Interestingly, in situ infrared spectroscopy shows similar surface significant species during the direct hydrogenation of DFMs and during the conventional catalytic hydrogenation of molecular CO2, suggesting that the catalytic mechanisms during the two operating regimes are highly correlated.

Cu-Bound Formates are Main Reaction Intermediates during CO2 Hydrogenation to Methanol over Cu/ZrO2.

Cu/ZrO2 is a promising catalyst for the hydrogenation of CO2 to methanol. Reaction pathways involving formates or hydroxycarbonyls have been proposed. We show here that three different types of formates can be observed under reaction conditions at 220 °C and 3 bar, one being located on metallic Cu and two others being bound to ZrO2 . The surface concentrations of formates were determined through calibration curves and their reactivity measured during chemical transient experiments. The Cu-bound formate represented only about 7 % of surface formates, but exhibited a higher reactivity and was found to be the only formate that could account for all the production of methanol. Copper is thus not there only to activate H2 , but also bears other crucial intermediates. This work reemphasizes that fully quantitative IR analyses and transient methods are required to unravel the role of surface species.