Transient Oxidation Research Articles

Transient CO Oxidation as a Versatile Technique to Investigate Cu2+ Titration, Speciation and Sites Hydrolysis on Cu–CHA Catalysts: The Cu Loading Effect

The investigation of the ZCu2+(OH)− and Z2Cu2+ ions modifications during NH3-SCR on Cu–CHA catalysts is a key aspect to clarify the still-debated low-T redox SCR mechanism. In previous works, the dry transient CO oxidation protocol has been employed to identify the generation of dinuclear Cu2+ structures under conditions representative of the low-T SCR–RHC: NH3 solvation promotes the inter-cage mobility and coupling of ZCu2+(OH)−, acting as the catalytic centers for the CO oxidation process, while Z2Cu2+ results inactive. Herein the same protocol, with pre-stored NH3, has been applied to a set of Cu–CHA catalysts with variable Cu loading (0.7–2.4% w/w) but fixed Si/Al: an increasing Cu content produced a net positive effect on the CO2 production, coherent with a growing ZCu2+(OH)− population, while a further enhancement was observed in the presence of H2O. The analysis of the integral CO2 production enabled to predict the maximum CO conversion, corresponding to the titration of the whole ZCu2+(OH)− content for each catalyst under dry condition, verifying the initial mechanism. Conversely, in the presence of water, the analysis evaluated an asymptotic titration of the total catalyst Cu2+ contents. This finding permits to generalize a recent study where combined TRMs, DFT and FTIR were used to probe the complete reversible Cu2+ sites hydrolysis and pairing in the presence of H2O and NH3, thus activating the participation of Z2Cu2+ species, too. These results also highlight the versatility and effectiveness of the CO oxidation protocol as a multi-purpose technique to study the Cu2+ ions in Cu–CHA catalysts.

On the sulfation reaction of protective and transient oxides at 650 °C and its role in the low temperature hot corrosion mechanism

MxOy-Na2SO4 (with M = Ni, Cr, Fe, Al, Ti, Nb) and NiSO4-Na2SO4 mixtures were prepared and their reactivity was examined at 650 °C in air + SO2 (400 and 1000 ppm). The formation of a molten phase for NiSO4-Na2SO4 mixtures and the rapid sulfation of NiO in these conditions were demonstrated. NiO sulfation should be considered when explaining the Type II hot corrosion attacks. Cr2O3, Fe2O3 and Al2O3 also react with the gas phase showing these oxides dissolved according to an acidic-fluxing mechanism in air + SO2/SO3 (400 and 1000 ppm) environments. Al2O3 is more soluble than Cr2O3 in these conditions.

Dynamic pressure scuffing initiation of a grade 250 flake graphite cast iron

The dynamic contact pressures experienced at the ring-liner interface of an engine are difficult to replicate in laboratory based reciprocating tribometers utilising a sliding Hertzian line contact, not least due to wear of the mating surfaces. A grade 250 flake graphite cast iron flat plate test geometry was designed to allow dynamic contact pressures between 8 and 62 MPa experienced in a heavy-duty diesel engine liner to be achieved on a reciprocating tribometer during the compression and expansion stroke.A constant normal load of 311 N was applied by sliding at 25 mm stroke length in PAO4 at 15 Hz against a 52100 rectangular contact area (2 × 20 mm). The temperature was slowly increased at 4 °C/min to initiate scuffing between the mating surfaces. Severe scuffing initiated at 250.8 ± 2.6 °C for all specimens. The spatially resolved friction force and non-contact optical profilometry suggested scuffing did not always initiate in the region of the highest contact pressure, whilst electron microscopy revealed that subsequent to lubricant failure, a transient low friction iron oxide layer was formed prior to removal and catastrophic adhesive wear.

Numerical simulation of the transient graphite oxidation process based on a dynamic mesh method

The high-temperature gas-cooled reactor uses graphite-matrix spherical fuel elements to coat the tri-structural isotropic fuel particles (TRISO). In accident conditions, graphite oxidation may cause fuel particle exposure, which further leads to severe radioactive contamination. Therefore, it is very important to study the oxidation behavior of graphite during air-ingress accidents. This work aimed to develop a reaction kinetic model of graphite oxidation based on the Institute of Nuclear and New Energy Technology (INET) experiment correlations and to study the transient process of graphite oxidation using computational fluid dynamics and a dynamic mesh method. The results show that convective diffusion and mass diffusion dominate the distribution of reaction products at different flow rates. The reaction rate in the early stage of oxidation was high and then decreased rapidly until the oxygen consumption rate and supplementation rate reached equilibrium. After that, the oxidation rate decreased slowly due to the reduction of graphite surface area. The fluctuating flow around the graphite leads to anisotropic oxygen concentrations at different inflow angles on the graphite surface. The fluctuations caused a non-uniform ellipsoidal graphite structure, in which graphite has a smaller radius of curvature and pits on the windward side and a larger radius of curvature on the leeward side. The oxidation mass of graphite is in good agreement with the INET experimental data, which shows that this study can provide a method for the estimation of the mass and shape of graphite oxidation.

Task Transfer Learning for Prediction of Transient Nitrogen Oxides, Soot, and Total Hydrocarbon Emissions of a Diesel Engine

Task Transfer Learning for Prediction of Transient Nitrogen Oxides, Soot, and Total Hydrocarbon Emissions of a Diesel Engine

Pnictogen‐Bonding Catalysts, Compared to Tetrel‐Bonding Catalysts: More Than Just Weak Lewis Acids

AbstractA hyperresponsive tool to assess supramolecular catalysis, the cyclization of di‐epoxides into cyclic ethers is used to elucidate the difference between pnictogen‐bonding and Lewis acid catalysis systematically. For all stereoisomers, most tested catalysts follow the Baldwin rules. Brønsted acid and anion–π catalysis afford almost only Baldwin products. Lewis acids such as SbCl3, BF3 and BiCl3 give the poorest selectivity, with at least 50 % Baldwin (B) products for all stereoisomers. In clear contrast, optimized pnictogen‐bonding catalysts operating on the Sb(III) and the Sb(V) level give the fused anti‐Baldwin (A) bicycles as the main product of trans epoxides, independent of syn or anti relation of the two epoxides. In the cis series, Sb(III) pnictogen‐bonding catalysts afford BA products almost exclusively for syn diastereomers, while anti diastereomers give equal amounts of BA and AB products. Sb(V) pnictogen‐bonding catalysts show similarly special trends. These unique characteristics support that pnictogen‐bonding catalysis differs from Lewis acid catalysis and can arguably be defined as its non‐covalent counterpart, just like hydrogen‐bonding catalysis is understood and appreciated as the non‐covalent counterpart of Brønsted acid catalysis. Computational studies on the origin of anti‐Baldwin selectivity reveal Sb(V) catalysts with an introvert deep σ hole surrounded by an almost planar ring of ligands. Central pnictogen‐bond attraction against peripheral steric repulsion then forces the epoxide to break open. In contrast, transient antimony oxidation in cyclic intermediates accounts for the chemoselectivity of Sb(III) catalysts. Presumably due to insufficient accessibility of their σ holes, the activity of tetrel‐bonding catalysts is negligible. The division between powerful pnictogen‐bonding and irrelevant tetrel‐bonding catalysts does not exist with the respective orthodox Lewis acids and thus supports that σ‐hole and Lewis acid catalysis are not the same.

Characterisation of a 10-Layer SOC Stack Under Pressurised CO2 Electrolysis Operation

One promising way of facing recent challenges to slow down the climate crisis or to reduce dependencies on fossil energy sources, e.g. natural gas, is using renewable methane and other e-fuels for storage and distribution via existing infrastructure. Solid oxide cell (SOC) reactors play an important role in the conversion of sustainable electric power into chemicals as they can be obtained from combined steam and CO2 co-electrolysis for syngas production. The pressurised electrolysis operation is a key factor for increasing the system efficiency of PtX-processes, including balance-of-plant (BoP) components, electrochemical reactors and high pressure downstream processes.In general, the yield of CO2 electrochemical reduction at atmospheric and pressurised conditions in high temperature co-electrolysis is still controversially discussed. Previously, several SOC short stacks were thoroughly analysed in pressurised steam- and co-electrolysis operation in a test-rig environment. These experimental results indicate marginal influence of pressure on the performance of electrolyte supported cells (ESC). In contrast, electrochemical impedance spectroscopy (EIS) suggests that pressurisation of pure CO2 electrolysis significantly reduces the fuel electrode impedance contribution, especially at lower temperatures around 700 °C [1,2].This work aims to experimentally determine the kinetic behaviour of pure CO2 electrolysis by varying operating conditions like pressure, temperature, reactant conversion and feed gas composition. The investigation of kinetic parameters during these experiments could complement the formerly described research. Furthermore, the kinetic expressions can be used when studying co-electrolysis operation to identify the shares of: (i) the reverse water-gas-shift (rWGS) and (ii) the CO2 electrochemical reduction. Polarisation curves were dynamically recorded and different current densities were evaluated in steady-state operation. Additionally, EIS measurements were performed at open circuit voltage (OCV), as well as under different current densities. The kinetic parameters were estimated by curve-fitting analysis of the experimental results. The resulting expressions will be implemented in the in-house modelling framework, TEMPEST, based on [3,4] with the aim to increase the accuracy of modelling high-temperature CO2 electrolysis and co-electrolysis systems. [1]Riedel, M., Heddrich, M. P., & Friedrich, K. A. (2020). Experimental Analysis of the Co-Electrolysis Operation under Pressurized Conditions with a 10 Layer SOC Stack. Journal of The Electrochemical Society, 167(2), 024504, DOI: 10.1149/1945-7111/ab6820.[2]Riedel, M. (2020, October 20–23). Experimental analysis of SOE stacks under pressurized co- and CO2 electrolysis operation [Paper presentation]. 14th European SOFC & SOE Forum, Lucerne, Switzerland.[3] Tomberg, M., Santhanam, S., Heddrich, M. P., Ansar, A., & Friedrich, K. A. (2019). Transient Modelling of Solid Oxide Cell Modules and 50 kW Experimental Validation. ECS Transactions, 91(1), 2089, DOI: 10.1149/09101.2089ecst.[4] Srikanth, S., Heddrich, M. P., Gupta, S., & Friedrich, K. A. (2018). Transient reversiblesolid oxide cell reactor operation–Experimentally validated modeling and analysis. Applied Energy, 232, 473-488, DOI: 10.1016/j.apenergy.2018.09.186.

Structural Model for Transient Pt Oxidation during Fuel Cell Start-up Using Electrochemical X-ray Photoelectron Spectroscopy.

Potential spikes during the start-up and shutdown of fuel cells are a major cause of platinum electrocatalyst degradation, which limits the lifetime of the device. The electrochemical oxidation of platinum (Pt) that occurs on the cathode during the potential spikes plays a key role in this degradation process. However, the composition of the oxide species formed as well as their role in catalyst dissolution remains unclear. In this study, we employ a special arrangement of XPS (X-ray photoelectron spectroscopy), in which the platinum electrocatalyst is covered by a graphene spectroscopy window, making the in situ examination of the oxidation/reduction reaction under wet conditions possible. We use this assembly to investigate the change in the oxidation states of Pt within the potential window relevant to fuel cell operation. We show that above 1.1 VRHE (potential vs reversible hydrogen electrode), a mixed Ptδ+/Pt2+/Pt4+ surface oxide is formed, with an average oxidation state that gradually increases as the potential is increased. By comparing a model based on the XPS data to the oxidation charge measured during potential spikes, we show that our description of Pt oxidation is also valid during the transient conditions of fuel cell start-up and shutdown. This is due to the rapid Pt oxidation kinetics during the pulses. As a result of the irreversibility of Pt oxidation, some remnants of oxidized Pt remain at typical fuel cell operating potentials after a pulse.

Heat-Induced Photosynthetic Responses of Symbiodiniaceae Revealed by Flash-Induced Fluorescence Relaxation Kinetics

Symbiodiniaceae live in endosymbiosis with corals. In the last few decades, mass bleaching events have occurred in the coral reefs, causing damage in the ecosystem and the associated species. Global temperature increase is affecting the algae, disturbing the whole symbiosis and leads to coral bleaching. However, the heat tolerance is strongly determined by the species (formerly genetic clades) harbored by the coral host. We assessed three different strains of Symbiodiniaceae family, i.e., Fugacium kawagutii (CS156), Symbiodinium tridacnidorum (2465), and Symbiodinium microadriaticum (2467), which display different heat tolerance under heat stress conditions. Flash-induced chlorophyll fluorescence relaxation is a useful tool to monitor various components of the photosynthetic electron transport chain and the redox reactions of plastoquinone pool. We observed the appearance of a wave phenomenon in the fluorescence relaxation by heating the strains in combination with microaerobic conditions. The characteristics of this fluorescence wave were found to be strain-specific and possibly related to the transient oxidation and re-reduction of the plastoquinone pool. The appearance of the wave phenomenon appears to be related to cyclic electron flow as well because it is accompanied with enhanced post-illumination chlorophyll fluorescence rise. These results will potentially reveal further details of the role of cyclic electron transport in Symbiodiniaceae and its relevance in heat stress tolerance.

Transient Radiation-Induced Berkelium(III) and Californium(III) Redox Chemistry in Aqueous Solution.

Despite the significant impact of radiation-induced redox reactions on the accessibility and lifetimes of actinide oxidation states, fundamental knowledge of aqueous actinide metal ion radiation chemistry is limited, especially for the late actinides. A quantitative understanding of these intrinsic radiation-induced processes is essential for investigating the fundamental properties of these actinides. We present here a picosecond electron pulse reaction kinetics study into the radiation-induced redox chemistry of trivalent berkelium (Bk(III)) and californium (Cf(III)) ions in acidic aqueous solutions at ambient temperature. New and first-of-a-kind, second-order rate coefficients are reported for the transient radical-induced reduction of Bk(III) and Cf(III) by the hydrated electron (eaq-) and hydrogen atom (H•), demonstrating a significant reactivity (up to 1011 M-1 s-1) indicative of a preference of these metals to adopt divalent states. Additionally, we report the first-ever second-order rate coefficients for the transient radical-induced oxidation of these elements by a reaction with hydroxyl (•OH) and nitrate (NO3•) radicals, which also exhibited fast reactivity (ca. 108 M-1 s-1). Transient Cf(II), Cf(IV), and Bk(IV) absorption spectra are also reported. Overall, the presented data highlight the existence of rich, complex, intrinsic late actinide radiation-induced redox chemistry that has the potential to influence the findings of other areas of actinide science.

Hydride Transfer Mechanism of Enzymatic Sugar Nucleotide C2 Epimerization Probed with a Loose-Fit CDP-Glucose Substrate.

Transient oxidation–reduction through hydride transfer with tightly bound NAD coenzyme is used by a large class of sugar nucleotide epimerases to promote configurational inversion of carbon stereocenters in carbohydrate substrates. A requirement for the epimerases to coordinate hydride abstraction and re-addition with substrate rotation in the binding pocket poses a challenge for dynamical protein conformational selection linked to enzyme catalysis. Here, we studied the thermophilic C2 epimerase from Thermodesulfatator atlanticus (TaCPa2E) in combination with a slow CDP-glucose substrate (kcat ≈ 1.0 min–1; 60 °C) to explore the sensitivity of the enzymatic hydride transfer toward environmental fluctuations affected by temperature (20–80 °C). We determined noncompetitive primary kinetic isotope effects (KIE) due to 2H at the glucose C2 and showed that a normal KIE on the kcat (Dkcat) reflects isotope sensitivity of the hydrogen abstraction to enzyme-NAD+ in a rate-limiting transient oxidation. The Dkcat peaked at 40 °C was 6.1 and decreased to 2.1 at low (20 °C) and 3.3 at high temperature (80 °C). The temperature profiles for kcat with the 1H and 2H substrate showed a decrease in the rate below a dynamically important breakpoint (∼40 °C), suggesting an equilibrium shift to an impaired conformational landscape relevant for catalysis in the low-temperature region. Full Marcus-like model fits of the rate and KIE profiles provided evidence for a high-temperature reaction via low-frequency conformational sampling associated with a broad distribution of hydride donor–acceptor distances (long-distance population centered at 3.31 ± 0.02 Å), only poorly suitable for quantum mechanical tunneling. Collectively, dynamical characteristics of TaCPa2E-catalyzed hydride transfer during transient oxidation of CDP-glucose reveal important analogies to mechanistically simpler enzymes such as alcohol dehydrogenase and dihydrofolate reductase. A loose-fit substrate (in TaCPa2E) resembles structural variants of these enzymes by extensive dynamical sampling to balance conformational flexibility and catalytic efficiency.

Editorial

Editorial

Oxidation mechanism and kinetics of nuclear-grade FeCrAl alloys in the temperature range of 500–1500 °C in steam

The oxidation mechanism and kinetics of two nuclear-grade FeCrAl alloys were investigated in steam up to 1500 °C by transient and isothermal oxidation tests. The slow α-alumina formation kinetics well matched only for the temperature range from 1000 °C to 1300 °C. Below 1000 °C, formation of transient alumina caused faster kinetics. In addition, an excessive Fe-rich oxide formation was observed on the inner surface due to rough surface at 600 °C. Above 1300 °C, convoluted α-alumina was easily spalled and caused faster kinetics. Moreover, the oxide spallation caused Cr and Al depletion and catastrophic oxidation above 1400 °C by the formation of Fe-rich oxide. The catastrophic oxidation caused a liquid phase in Fe-rich oxides, which significantly changed the tube segment geometry.

New sight on the oxide film growth mechanism in a single crystal Ni-based superalloy with a ground surface signature

The oxide film characteristics and growth mechanism of a single crystal Ni-based superalloy were studied under the ground surface signature. In the transient oxidation, oxygen atoms invaded the substrate along with the γ ´ phases, resulting in the Ni-Al spinels and alumina with nanosize formed simultaneously. Moreover, the outer layer of NiAl2O4 obeyed a liner law (with n ≈ 1) and was controlled by the outward diffusion of Ni and Al cations (with Q= 1.13 eV), whereas the inner Al2O3 layer followed a parabolic law(with n ≈ 0.5) and was determined by the inward diffusion of oxygen (with Q= 1.43 eV).

Graham Wood. 6 February 1934—4 November 2016

Graham Wood was a world-leading corrosion scientist who bridged both the aqueous (electrochemical) corrosion and high-temperature oxidation branches of the subject. His analytical predictions of depletion and enrichment profiles in substrate and scale during preferential oxidation have long been confirmed in practice. He also demonstrated that transient oxides can be vital solid lubricants in oxidative friction and wear processes. He elucidated ionic transport in amorphous anodic films, leading to precise models of pore initiation, development and closure, thus allowing the strict design of anodic films for practical application. He set up, and headed, the Corrosion and Protection Centre at the University of Manchester Institute of Science and Technology (UMIST) and was instrumental in initiating the Corrosion and Protection Centre Industrial Service, which, respectively, became the world's largest academic centre on the study of materials degradation and the world's largest corrosion consulting organization. While keeping active in research, he held increasingly senior administrative roles, where he established a specialist graduate school and helped prepare UMIST to full independence from the Victoria University of Manchester.

TRANOX: Model for non-isothermal steam oxidation of zircaloy cladding

• Developed a mechanistic oxygen distribution model in steam-oxidized Zircaloy-4. • Experimental validation conducted for ECR, oxygen distribution, and phase thickness. • Providing accurate oxidation prediction in non-isothermal conditions. • Validate the accuracy of CP correlation and provide an advanced mechanistic model. • Explaining effect of hydrogen on oxygen content in zr for highburnup cladding. TRANOX-1.0 (TRANsient OXidation), a mechanistic model that calculates oxygen distribution for isothermal and non-isothermal transients (1000–1250 °C) has been developed. TRANOX solves radial transient diffusion equation using Finite Difference Method (FDM) with spatial phase changes for each time step. Diffusion coefficients of each resulting phase were obtained by searching a combination that best guarantees Equivalent Cladding Reacted (ECR) and α-Zr(O) thickness simultaneously. The model has been extensively validated by overarching experimental campaigns including isothermal and non-isothermal high temperature steam oxidation, and post-metallurgical characterization. Accounting for α+β equilibrium phase, TRANOX gives accurate predictions for ECR, spatially averaged radial oxygen distribution, and thicknesses of each phase. Mechanistically solving the diffusion equation, TRANOX exhibits unbiased predictability for isothermal and non-isothermal transients. TRANOX was used to understand the oxygen distribution of pre-hydrided high burnup fuel cladding. The diffusion resistance behavior of α-Zr(O) and α+β with respect to hydrogen content counteract, neutralizing the overall hydrogen effect on oxygen distribution. The limited hydrogen effect on diffusion resistance during the early stage of steam oxidation further reduces the hydrogen-sensitivity of oxygen profiles. This finding provides a cogent explanation for the effect of hydrogen on oxygen distribution and oxidation kinetics observed by a number of past studies.

The oxidation behavior of Mg-Er binary alloys at 500 ℃

Thermodynamics and kinetics of the oxidation behavior of magnesium-erbium (Mg-Er) alloys at 500 ℃ were studied. The observed protective oxidation behavior, which follows parabolic kinetics, can be attributed to the formation of compact Er2O3 surface layer and continuous dissolution and diffusion of Er from the matrix. The surface film of Mg-8.1Er (wt%) alloy was composed of four sublayers, with the double Er2O3 layers consisting of a compact fine-grain layer and an underlying coarse-columnar-grain layer providing the protective effect. A four-stage oxidation process composed of three transient reaction-controlled oxidation processes and followed by a diffusion-controlled oxides growth process is proposed.

First-principles study on the NiAl/Al2O3 interfacial segregation of Hf during the oxidation of Hf-modified NiAl

Despite the well-known beneficial effect of reactive element dopants on improving the oxidation resistance of alumina-forming alloys, many open questions remain, including the migration and segregation of reactive elements at the oxide/alloy interface, a key zone in controlling the global oxidation kinetics and interface adhesion. Herein, we elucidate the atomic processes governing the interfacial dynamics of hafnium with γ-Al2O3 and θ-Al2O3, two dominant metastable phases before transforming to stable α-Al2O3 during the oxidation of Ni-Al alloys. Our results show that Al vacancies in the Al2O3 overlayer play a critical role in influencing the interfacial segregation of Hf atoms and HfO2 formation. For the γ-Al2O3 (001)/NiAl (100) interface, the presence of interfacial Al vacancies in γ-Al2O3 drives the interfacial segregation and aggregation of Hf atoms from the NiAl substrate, resulting in interfacial nucleation of HfO2. By contrast, for the θ-Al2O3 (100)/NiAl (100) interface, the presence of interfacial Al vacancies steers the migration of Hf atoms from the NiAl substrate across the oxide/alloy interface deeper into the oxide lattice, promoting the HfO2 formation in the bulk of the θ-Al2O3 layer. These results may find broader applicability for manipulating the interfacial transport process of reactive elements by controlling the phase and stoichiometry of the transient oxide phases.

The Role of Oxidation Resistance in High Temperature Alloy Selection for a Future with Green Hydrogen

Hydrogen is being considered integral to the future energy landscape but there is limited mechanistic understanding and a lack of predictive models to describe the combined effects of alloy and gas composition, temperature, thermal cycling and water vapor contents on the oxidation behavior of high-temperature materials. Experimental evaluations were combined with coupled thermodynamic-kinetic modeling to investigate the oxidation behavior of five representative Ni-based superalloys in two water vapor contents (10%, 60% H2O) under thermal cycling (1-h, 100-h cyles) conditions at 800°C and 1000°C. The alloy with the highest Ti content demonstrated the poorest cyclic oxidation behavior while the alloy with highest Cr and Al contents was expected to continue to support protective formation of a compact Al2O3 scale. Accelerated degradation of the chromia-forming alloys was observed in the higher water vapor content but the impact on transient oxidation of the alumina-forming alloys needs further investigations.

Photochemical transformation of pyridinium ionic liquids in aqueous phase: Kinetics, products and mechanism

Pyridinium ionic liquids (Pyr+ ILs) with promising applications are likely to appear in large quantity in water environment and become emergent pollutants due to their high hydrophilicity and low biodegradability. Hence, we studied the indirect photochemical degradation of Pyr+ ILs, including their kinetics of reactions with transient oxidants (•OH, CO3•–, triplet stated sodium anthraquinone-2-sulfonate (3AQ2S*) and 1O2), modeling studies on contribution of the transient oxidants to their degradation and their half-lives, as well as mechanistic study and toxicity estimation of the ILs and their products. Half-lives of these Pyr+ ILs were estimated to be 5–600 days under different scenarios, indicating persistence of the Pyr+ ILs in natural waters. Moreover, major contributors for degradation of the ILs are triplet stated dissolved organic matter (3DOM*) and CO3•―. For reaction with •OH, products identified by secondary mass spectrometry (MS2) and hydrogen nuclear magnetic resonance (1H NMR) indicate that the reactions proceed via hydrogen-atom transfer at the initial stage, and further transformation of the alkyl radicals lead to products by dehydrogenation, hydroxylation, and further oxidation. Additionally, model study shows that 1-butyl-Pyr+ and 1-butyl-3-methyl-Pyr+ IL are toxic to the aquatic organisms, and their products possess even higher toxicity, indicating that the Pyr+ ILs in natural waters may pose threat to aquatic organisms. Potential eco-risk of Pyr+ ILs should be fully considered before large-scale industrial application.