A nerve‐agent simulant based on a phosphate ester is hydrolyzed using a MOF‐based catalyst. Suspensions of MOF‐808 (6‐connected), a material featuring 6‐connected zirconium nodes, display the highest ...hydrolysis rates among all MOFs that have been reported to date. A plug‐flow reactor was also prepared with MOF‐808 (6‐connected) as the active layer. Deployed in a simple filtration scheme, the reactor displayed high hydrolysis efficiency and reusability.
Detox, faster than fast: Chemical‐warfare agents, including nerve agents, are a threat to humans. A six‐connected zirconium metal–organic framework (MOF) can hydrolyze a nerve‐agent simulant within 30 s which is faster than any other catalyst reported. It is a promising material for protective equipment as well as the elimination of large stores of nerve agents.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The pyrolysis of N-methylethylamine (MEA, C3H9N) was studied in a flow tube reactor at 30 Torr within 1073–1348 K. 12 intermediates and products were detected by the time-of-flight molecular beam ...mass spectrometry with the light source of tunable synchrotron vacuum ultraviolet. The photoionization cross section (PICS) of MEA was obtained over the photon energy range from 8.0 to 11.5 eV and used to calculate the mole fractions of the detected species. Based on the previous work of other amines, a detailed kinetic model consisting of 883 species and 4750 reactions was developed. Reasonable agreements between the predicted mole fractions and the measured values were obtained for MEA and main nitrogenous intermediates and products. To deeply understand the nitrogen conversion route of MEA pyrolysis, rate-of-production and sensitivity analyses were performed. MEA is dominantly consumed via H-abstraction reactions by H radical at C1 or C3 site. The sensitivity analysis indicates that the unimolecular decomposition reactions of MEA via the cleavage of two kinds of C-N bonds play important roles in promoting MEA consumption, especially at higher temperatures, because the subsequent H atom produced from the fragments decomposition enhances the radical pool. Three C2H5N isomers were observed in this work, with an interconversion between vinylamine and ethanimine. N-methyl-1-ethanimine (C3H7N) is the only identified C3 unsaturated amine with limited concentrations. This can be attributed to the fact that the chemical bonds between the C and N atoms are weaker than CH or NH in primary radicals. These results will enrich the knowledge of C3 amine chemistry and lay a solid foundation for exploring the kinetic behavior of more complicated amines.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A vertical flow electro-Fenton reactor for organic pollutant efficient degradation was described.•The effect of key parameters on pollutants degradation and mineralization efficiency was ...studied.•The degradation performance was more efficient than that in traditional parallel flow reactor.•The dependence of pollutant removal and energy consumption with cell numbers were investigated.
Degradation of organic pollutants using electro-Fenton has received great attentions in recent years, however, less efforts have been paid to sound reactor exploration. This study presented a novel vertical-flow electro-Fenton reactor, composing of 10 cell compartments using PbO2 anode and modified graphite felt mesh cathode, which was found to be more complete and efficient in organic pollutants degradation when comparing with the traditional parallel-flow reactor, using tartrazine as the model pollutant. Under the optimal conditions of pH 3, voltage 4.0V, flow rate 40mL/min, Fe2+ 0.4mmol/L and aeration rate 80mL/min, the tartrazine of initial concentration of 100mg/L could reach near 100% removal and the TOC removal efficiency was 61.64%. The dependence of pollutant removal and energy consumption with the cell numbers were investigated, which would help to design vertical-flow electro-Fenton reactor for practical application.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This work presents the changing abundance of surface functional groups (SFGs) on polystyrene (PS) upon weathering within one or a few molecular monolayers from a molecular point of view. PS particles ...were aged by exposing it to a gas flow of typically (5 %) O3 in O2 (PSO3), UV radiation using a solar simulator under controlled conditions in the laboratory (PSSS) and to the water/air interface immerged in a freshwater lake for 2 months (PSL). The chemical composition of the interface of weathered, compared to pristine (virgin or PSV) material was established using a titration technique that probed the chemical composition of the molecular interface of the polymer. The main conclusions of this exploratory study are: (a) The interface of PS changes significantly compared to ATR-FTIR spectra that do not show additional absorptions in the mid-IR spectrum over a penetration depth of more than hundred monolayers at 10 μm; (b) The average surface functionalization of the gas-solid interface, corresponding to the sum of all examined types of SFG, increases from 20 % of a monolayer for PSV to 40, 50 and 84 % for PSL, PSO3 and PSSS, respectively; (c) in all cases the most important SFG was surface -OH ranging from 11.2 to 64 % for PSV and PSSS, respectively; (d) each PS sample shows a characteristic SFG pattern or fingerprint using several probe gases; (e) O3 interaction led to interface acidification; (f) UV treatment leads to the highest degree of surface -OH functionalization compared to PSO3 and PSL. The accumulation of SFG's renders the interface more reactive towards adsorption of probe gases.
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•As a consequence of treatment of PSV in a laboratory (PSO3, PSS) and field environment (PSL) surface functionalization probed by 5 reactive gases (TMA, HA, TFA, HCl, O3) increases from 20% ML (PSV) to 40-85% ML coverage•O3 interaction with PSV leads to interface acidification probed by TMA•UV treatment in a solar simulator in the absence of O3 leads to the highest degree of functionalization (84% ML) followed by O3 treatment (50% ML)•Each weathering method leads to a characteristic pattern of SFG distribution at the interface when several probe gases are compared
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The combustion kinetics of a novel oxygenated bioblendstock for diesel, 4-butoxyheptane (4-BH), was investigated experimentally using a flow reactor and a heated, high-pressure shock tube. The flow ...reactor experiments employed oxygen as the oxidizer and helium as the diluent with oxidation conducted at atmospheric pressure and 10 bar for temperatures from 400 to 1000 K at 20-K intervals. The fuel, oxidizer, and diluent flow rates were varied at different temperatures to maintain a constant initial fuel mole fraction of 1000 ppm, with stoichiometric equivalence ratio, and a residence time of 2.0 s. The reacted gas was fed to two separate GC systems that could qualitatively and quantitatively detect product species. Additionally, real fuel-air ignition delay time (IDT) data were collected using a heated, high-pressure shock-tube facility. Fuel lean (ϕ = 0.5) and stoichiometric (ϕ = 1.0) mixtures were investigated at 10 atm as well as at 30 atm for the fuel lean case for temperatures between 847 and 1259 K. A detailed chemical kinetics mechanism was developed to model the product distribution from the flow reactor and IDTs from the shock tube. The proposed model was able to predict the double NTC behavior in flow reactor experiments reasonably well. Model predictions at low temperatures were observed to be highly sensitive to the rate constants of ketohydroperoxide (KHP) decomposition in the case of the OOH group in α position which were modeled based on existing literature studies on ethers. It was noted that in the absence of theoretical or experimental studies, the rate constants for KHP decomposition used in the literature were empirically set. Additional studies are required to address the gap in model prediction obtained in this study and to reduce the uncertainty in kinetics models for ether oxidation. Predicted product concentrations and IDTs showed some quantitative agreement with experimental data, but the overall reactivity of the IDTs is underpredicted. Additionally, significant deviation is observed for the IDT results at 10 atm for the stoichiometric case with minor deviations for the other cases. The reaction pathways to the missing products were then further analyzed theoretically through quantum-mechanical calculations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Multi-objective algorithm applied to the self-optimisation of complex pharmaceutical processes.•Algorithm targeted automated reactor productivity and downstream purification.•Pareto ...front rapidly generated for three competing objectives.
There has been an increasing interest in the use of automated self-optimising continuous flow platforms for the development and manufacture in synthesis in recent years. Such processes include multiple reactive and work-up steps, which need to be efficiently optimised. Here, we report the combination of multi-objective optimisation based on machine learning methods (TSEMO algorithm) with self-optimising platforms for the optimisation of multi-step continuous reaction processes. This is demonstrated for a pharmaceutically relevant Sonogashira reaction. We demonstrate how optimum reaction conditions are re-evaluated with the changing downstream work-up specifications in the active learning process. Furthermore, a Claisen-Schmidt condensation reaction with subsequent liquid-liquid separation was optimised with respect to three-objectives. This approach provides the ability to simultaneously optimise multi-step processes with respect to multiple objectives, and thus has the potential to make substantial savings in time and resources.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Plug flow reactors (PFRs) approximated by the connection of multiple completely stirred tank reactors (CSTRs) in series were used to achieve continuous flow aerobic granulation in real domestic ...wastewater. This study revealed, possibly for the first time, that the morphology and characteristics of aerobic granular sludge transformed in the course of a mixed liquor flow through a PFR. The feast zone, located at the front end of the PFR, can quickly develop filamentous structure on the surface of aerobic granular sludge which later disappeared in the famine zone at the back end of the PFR. Detention time from the front to the back end of the PFR was only 6.5 h. During this period the observed sludge morphological change led to sludge settleability fluctuation as much as 66% in zone settling velocity, 16% in specific gravity, and 40% in settled sludge volume. Further analysis revealed these types of sludge morphologies and characteristics were closely related to the specific substrate removal rate profiles of the PFR, i.e., the feast zone might have encouraged filamentous bacteria to extend outward into the bulk solution for soluble substrate, and the famine zone appeared to play an essential role in solidifying the structure of granular sludge structure prior to subjecting it to the gravity selection pressure. It can be inferred from this study that the lack of a famine zone in aerobic granulation reactors can loosen the granule structure and in turn deteriorate granule settleability. For a PFR, a famine zone following the feast zone is essential for maintaining the structural integrity of aerobic granular sludge in a continuous flow wastewater treatment system.
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•Granular sludge morphological evolution occurred within a 6.5 h HRT.•Poor settleability improved in famine zone.•Famine zone caused filamentous structure retraction into granules.
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•Early reaction stages of a co-precipitation synthesis were studied via in-situ synchrotron XRD and SAXS.•A stabilisation procedure was developed, not requiring any ultra-sonication ...or washing step.•IONP formation and stabilisation kinetics were determined.•A multistage flow reactor facilitated the entirely continuous production of stable IONPs.
Co-precipitation is by far the most common synthesis for magnetic iron oxide nanoparticles (IONPs), as cheap and environmentally friendly precursors and simple experimental procedures facilitate IONP production in many labs. Optimising co-precipitation syntheses remains challenging however, as particle formation mechanisms are not well understood. This is partly due to the rapid particle formation (within seconds) providing insufficient time to characterise initial precipitates. To overcome this limitation, a flow chemistry approach has been developed using steady-state operation to “freeze” transient reaction states locally. This allowed for the first time a comprehensive analysis of the early stages of co-precipitation syntheses via in-situ Small Angle X-ray Scattering and in-situ synchrotron X-Ray Diffraction. These studies revealed that after mixing the ferrous/ferric chloride precursor with the NaOH base solution, the most magnetic iron oxide phase forms within 5 s, the particle size changes only marginally afterwards, and co-precipitation and agglomeration occur simultaneously. As these agglomerates were too large to achieve colloidal stability via subsequent stabiliser addition, co-precipitated IONPs had to be de-agglomerated. This was achieved by adding the appropriate quantity of a citric acid solution which yielded within minutes colloidally stable IONP solutions around a neutral pH value. The new insights into the particle formation and the novel stabilisation procedure (not requiring any ultra-sonication or washing step) allowed to design a multistage flow reactor to synthesise and stabilise IONPs continuously with a residence time of less than 5 min. This reactor was robust against fouling and produced stable IONP solutions (of ~1.5 mg particles per ml) reproducibly via fast mixing (< 50 ms) and accurate temperature control at large scale (> 500 ml/h) for low materials cost.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•Multi-objective algorithm applied to the self-optimization of flow reactor.•Algorithm simultaneously targeted reactor productivity and environmental objectives.•Pareto front shows ...the trade-off between these target objectives.•Gaussian process models provide knowledge about the nature of interactions.
Automated development of chemical processes requires access to sophisticated algorithms for multi-objective optimization, since single-objective optimization fails to identify the trade-offs between conflicting performance criteria. Herein we report the implementation of a new multi-objective machine learning optimization algorithm for self-optimization, and demonstrate it in two exemplar chemical reactions performed in continuous flow. The algorithm successfully identified a set of optimal conditions corresponding to the trade-off curve (Pareto front) between environmental and economic objectives in both cases. Thus, it reveals the complete underlying trade-off and is not limited to one compromise as is the case in many other studies. The machine learning algorithm proved to be extremely data efficient, identifying the optimal conditions for the objectives in a lower number of experiments compared to single-objective optimizations. The complete underlying trade-off between multiple objectives is identified without arbitrary weighting factors, but via true multi-objective optimization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•A vertical flow electro-Fenton reactor for high-performance H2O2 electrolyzers was described.•The effect of key parameters on pollutants degradation and mineralization efficiency was studied.•The ...H2O2 production and degradation performance was more efficient than that in traditional parallel flow reactor.
This study has investigated a novel jet-type reactor (vertical flow reactor) in order to improve the oxygen utilization for enhanced production of hydrogen peroxide (H2O2). In vertical flow electro-Fenton (EF) system, the effects of current density, water flow rate, Fe2+ concentration and initial pH were investigated for the removal of tetracycline hydrochloride. The efficient removal of tetracycline hydrochloride could reach 100% within 60 min under the current density of 24 mA cm−2, water flow rate of 10 L h−1 and pH of 3. The vertical flow reactor was relatively stable and reusable for the removal of pollutants. The removal rates of tetracycline hydrochloride and total organic carbon (TOC) were maintained at about 95% and 80%, respectively in a 5-time continuous runs. Moreover, the vertical flow reactor could efficiently remove a wide type of organic pollutants, and the TOC removals of acid magenta, rhodamine B, alizarin yellow R, orange Ⅳ and diclofenacdium were 75.96, 77.90, 61.27, 72.11 and 82.89%, respectively after 3 h of reaction time. Cathodic adsorption, anodization, and H2O2 oxidation played minor roles in the removal of tetracycline hydrochloride, while the OH radicals are the most pivotal oxidizing substance in the system. As compared with the traditional aeration, the vertical flow reactor has a high-speed jet flow state, which makes the liquid-gas mixture homogeneous, and renders it high oxygen absorption rate, cost effectiveness and high power efficiency for the degradation of pollutants.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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