Continuous-flow, gas-phase, catalytic transfer hydrogenation of methyl levulinate with ethanol over two different zirconia crystalline phases
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•Continuous-flow catalytic transfer ...hydrogenation of methyl levulinate with ethanol.•Structure-activity relationship of the effect of the zirconia crystalline structure.•Complementary approach with characterisation, experimental, DFT and NMR relaxation studies.
The depletion of fossil resources is driving the research towards renewable alternatives, like lignocellulosic biomass. Therefore, the development of efficient continuous-flow processes, allowing to achieve better productivity compared to batch processes, will play a crucial role in promoting a sustainable transition. In this context, we report on the continuous-flow, gas-phase, catalytic transfer hydrogenation (CTH) of methyl levulinate and ethanol over zirconia catalysts, in particular focusing on the effect of two different crystalline phases (i.e. monoclinic, m-ZrO2, and tetragonal, t-ZrO2) on catalyst performance. An in-depth catalyst characterisation was coupled with both computational and 1H-NMR relaxation studies to assess the structure-activity relationship, providing fundamental insights into the catalytic process and future catalyst optimization. The results, indicate that the higher Lewis acidity and basicity along with the lower affinity with ethanol of m-ZrO2 with respect to t-ZrO2 are responsible for the promotion of undesired oligomerisation reactions of angelica lactones responsible for catalyst deactivation.
As ubiquitous chemical substances in water bodies, nitrophenol compounds (NCs) can form chlorinated halonitromethanes (Cl-HNMs) in the chlorination process. This work chose six typical NCs to explore ...Cl-HNMs produced during the UV/post-chlorination process, and Cl-HNMs yields from these NCs followed the increasing order of 4-, 2-, 2-amino-3-, 2-methyl-3-, 3-, and 2-chloro-3-nitrophenol. The Cl-HNMs yields increased continually or increased firstly and declined with post-chlorination time. Increasing chlorine dosage favored Cl-HNMs formation, while excessive chlorine dosage decreased Cl-HNMs produced from 2- and 4-nitrophenol. Besides, appropriate UV radiation, acidic pH, and higher precursor concentrations facilitated Cl-HNMs formation. Then, the reaction mechanisms of Cl-HNMs generated from these different NCs were explored according to density functional theory calculation and identified transformation products (TPs), and the main reactions included chlorine substitution, benzoquinone compound formation, ring opening, and bond cleavage. Moreover, the Cl-HNMs generated from 2-chloro-3-nitrophenol were of the highest toxicity, and the six NCs and their TPs also presented ecotoxicity. Finally, two kinds of real waters were used to explore Cl-HNMs formation and toxicity, and they were significantly distinguishable compared to the phenomena observed in simulated waters. This work will give new insights into Cl-HNMs formation from different NCs in water disinfection processes and help better apply the UV/post-chlorination process to water treatments.
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•Nitrophenol compounds (NCs) have high formation potential of Cl-HNMs.•UV radiation, chlorine dosage, and pH markedly affected Cl-HNMs formation from NCs.•Formation mechanisms and pathways of Cl-HNMs from different NCs were proposed.•Cl-HNMs, NCs, and their transformation products presented different toxicity.•Cl-HNMs formation in real waters were more complicated than that in simulated waters.
Two-dimensional (2D) transition metal dichalcogenides (TMDs) hold great promise for room temperature (RT) NO2 sensors. However, the exposure of the edges of TMDs with high adsorption capability and ...electronic activity remains a great obstacle to achieve high sensor sensitivity. Herein, we demonstrate a high-performance RT NO2 gas sensor based on WS2 nanosheets/carbon nanofibers (CNFs) composite with abundant intentionally exposed WS2 edges. Few-layer WS2 nanosheets are anchored on CNFs through a hydrothermal process. The approach permits to achieve a coating presenting an optimized active surface area and accessibility of the sensing layers. The exposure of WS2 edges remarkably improves the sensing properties. Consequently, the WS2@CNFs composite exhibits excellent selectivity to NO2 at RT with improved response and much lower detection limit in comparison to the WS2 and CNFs counterparts. Density functional theory (DFT) calculations verify a surprisingly strong NO2 adsorption on WS2 edge sites (adsorption energy 3.40 eV) with a partial charge transfer of 0.394e, while a week adsorption on the basal surface of WS2 (adsorption energy 0.25 eV) with a partial charge transfer of 0.171e. The strategy proposed herein will be instructive to the design of efficient material structures for low-power NO2 sensors with optimized performances.
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•WS2 nanosheets are anchored on carbon nanofibers (CNFs) by hydrothermal method.•WS2@CNFs composites have abundant exposed WS2 edges.•Gas sensor based on WS2@CNFs exhibits remarkable NO2 sensitivity at room temperature.•Density functional theory (DFT) calculations verify strong NO2 adsorption on the WS2 edges.
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The introduction of oxygen-defects has been a versatile strategy to enhance photocatalysis efficiency. In this work, a 2D/3D Bi/BiO2-x/Bi2WO6 heterojunction photocatalyst with rich ...oxygen-defective was in sequence prepared through a facile solvothermal method, which displays favorable photocatalytic activity towards organic contaminants under visible-NIR light irradiation. The enhancement in photocatalytic performance can be attributed to the synergistic effect between oxygen-vacancy-rich heterojunction and the localized surface plasmon resonance induced by metallic Bi. The functional group interaction, surface morphology, crystal structure, element composition, and tuned bandgap were investigated by FT-IR, SEM, Raman shift, ICP-MS, and XPS technique. The spectrum response performance of the photocatalyst was verified by UV–visible DRS analysis. Results of photodegradation experiments toward organic contaminants showed that the prepared photocatalyst can degrade 90% of phenol in 20 mins under visible-NIR light irradiation, both Z-scheme heterojunction and the introduction of Bi metal contribute to the enhancement in the photocatalytic activity. The results of the DFT calculation suggest that the valence band-edge hybridization within BiO2-x and Bi2WO6 can effectively enhance the photocatalytic performance by increasing the migration efficiencies of electron-hole pairs. Moreover, a possible mechanism was proposed on the results of EIS, ESR and GC–MS tests. This work offers a novel insight for synthesizing efficient visible-NIR light photocatalysis by activating the semiconductors with Bi metal.
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•CuFe2O4/pyrite waste had excellent photothermal conversion performance.•The CuFe bimetallic in CuFe2O4/pyrite accelerate electron transfer.•The in situ heat generated by photothermal ...effect can reduces the reaction barrier.•DFT revealed atoms with high Fukui index were active sites for radical attack.•Degradation pathway was proposed according to intermediates and DFT analysis.
The widespread distribution of antibiotics in natural waters has raised global concerns due to their potential threat to the aquatic environment. In this study, 40 %-CuFe2O4/pyrite waste composite material was constructed for the removal of ofloxacin (OFX) through activating H2O2 in photothermal Fenton processes. It had excellent photothermal conversion performance and could serve as a superior photothermal-Fenton catalyst. The removal efficiency of OFX was 96.13 % in the photothermal Fenton reaction, and the apparent first-order kinetics rate constant (k) was 4.33 and 12.15 times higher than in the traditional Fenton without light and 40 %-Fe/PW photothermal Fenton reaction. This could be attributed to the introduction of photothermal effect promoted collisions between substances, and expedited the reaction rate. The redox cycle of Fe(II)/Fe(III) and Cu(I)/Cu(II) in the Cu-Fe bimetal system also contributed to the removal of OFX. Besides, it exhibited excellent cycling stability, extensive adaptability for various pollutants and water properties. The order of contribution of active radicals to the removal of OFX was ∙ OH>h+ >∙O2-, and they attacked the active atoms of OFX molecule with high Fukui index. Hopefully, this study may encourage the utilization of the photothermal effect for contaminant removal and introduce a novel perspective for environmental remediation.
Novel TPHCPs with multiple accessible sites show durable high-activity for cycloaddition of CO2 and epoxides under additive-free conditions.
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•TPHCPs with abundant accessible active ...sites are constructed by a simple one-pot method.•TPHCP⊃3Br– promotes CO2/epoxides coupling efficiently under additive-free conditions.•The developed catalyst is easily separated and exhibits durable high-activity.•Valuable insight into the cycloaddition mechanism is theoretically elucidated.
The development of highly stable and active single-component catalysts for transformation of CO2 into organic carbonates remains challenging. Here several novel triazinyl- and pyridinium-based zwitterionic hypercrosslinked polymers (TPHCPs) were constructed via a simple one-pot strategy and their structures were characterized. The TPHCPs exhibit excellent porosity and multiple adjustable functional units, including nucleophilic Br− anions formed in situ. The obtained TPHCPs were used in the cycloaddition reaction of CO2 and epoxide, and the effects of TPHCP structures and reaction parameters were studied respectively. TPHCP⊃3Br− was determined to be the most excellent catalyst, the multiple active sites of TPHCP⊃3Br− are beneficial for the simultaneous adsorption and activation of CO2 and epoxide. It could efficiently catalyze the reaction of CO2 with various epoxides to form corresponding cyclic carbonates without a co-catalyst under mild conditions. In addition, the recovery and reuse performances of TPHCP⊃3Br− were examined. The catalytic activity did not change obviously upon reusing five times. Finally, a reasonable mechanism of the cycloaddition reaction under the synergistic actions of multiple active sites was proposed by using a DFT calculation method.
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•Lattice strain Bi2WO6 was fabricated using a one-step hydrothermal doping method.•Efficient ciprofloxacin and tetracycline mixed wastewater photodegradation were achieved.•Revealing ...the asymmetric polarization effect caused by natural localized electric field by revealing lattice compression strain.•The degradation intermediates and pathways were derived and validated using the Fukui function and LC-MS.
Localized polarization electric field is a key factor affecting photocatalytic activity. In this study, the localized polarization electric field of lattice strain was introduced into the electronic structure of Bi2WO6 by using the high and low valence state doping method. The impurity energy level induced by lattice strain further affects the gap energy level. As an intermediate state for electron transfer, the gap level further promotes the dynamics of photo generated charges, reducing the band gap by 0.4 eV and improving the photoelectric performance by 60 %. Various tests and theoretical calculations have confirmed that the internal electric field of local polarization significantly improves the generation and transfer rate of photo-generated charges, thereby boosting catalytic activity. The removal ratios of ciprofloxacin (CIP) and tetracycline (TC) in the mixed wastewater reach 91.5 % and 97.1 % in 90 min, respectively. Cyclic tests have shown that the electronic structure control exhibits excellent stability with removal ratios of CIP and TC of 83.9 % and 85.7 %, respectively. Finally, the 8C of CIP and the 11C and 19O of TC are most susceptible to the attack of free radicals generated by lattice compression spin polarization electric fields based on the theoretical calculations of the Fukui function and the analysis of intermediates. This work provides new insights into the design of catalysts for efficient photo generated charge dynamics with lattice strain.
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•MCN-60 exhibited excellent photodegradation rate of ofloxacin.•Type Ⅱ heterojunction of MCN-60 promoted separation of electron-hole pairs.•O2– radical was the main active species in ...ofloxacin photodegradation.•DFT calculation and LC-MS explained the degradation pathways.•Toxicity of ofloxacin was reduced during photocatalysis process by QSAR analysis.
In this study, g-C3N4/NH2-MIL-88B(Fe) (MCN-x) heterostructures were successfully prepared using a facile solvothermal method. MCN-x composites exhibit excellent degradation performance toward ofloxacin in aqueous solution under visible light (λ > 420 nm). The photodegradation rate of ofloxacin by MCN-60 under visible light reaches 96.5% in 150 min, and the apparent first-order kinetics rate constant reaches 0.0217 min−1, 3.7 and 4.7 times that of pristine g-C3N4 and NH2-MIL-88(Fe), respectively. This decent photocatalytic performance is principally attributed that the introduction of g-C3N4 can notably promote the separation of photogenerated electron-hole pairs. Besides, the photocatalytic efficiency and structure of the MCN-60 composite basically show no change after three reuse cycles. Furthermore, trapping experiments and ESR analyses confirm that the O2– radical has a more dominant role than OH and holes (h+). The ofloxacin degradation mechanism and pathway are predicted by density functional theory (DFT) calculations and an intermediate analysis. Quantitative structure–activity relationship (QSAR) predictions reveal that the ofloxacin photocatalytic degradation process can reduce toxicity in a step-by-step manner. MOF-based materials have been confirmed to show high potential for practical application in removing emerging pollutants from wastewater.
This study aimed to design an efficient and easily collected/regenerated adsorbent for trace concentration sulfamethoxazole (SMX) removal to eliminate its negative impacts on human health, reduce the ...risk of adsorbed SMX release and boost the reusability of adsorbent. Various multiple modified sludge-derived biochars (SBC) were synthesized in this work and applied to adsorb trace level SMX. The results demonstrated that hydrothermal N-doping, magnetization coupled with ball milling co-functionalized SBC (BMNSBC) displayed the greater adsorption ability for SMX. The maximum adsorption capacity of BMNSBC for SMX calculated by Langmuir model was 1.02×105 μg/g, which was 12.9 times of SBC. Characterization combined with adsorption experiments (e.g., models fitting) and DFT calculation confirmed that π-π conjugation, Lewis acid-base, pore filling and Fe3O4 complexation were the primary forces driving SMX binding to BMNSBC. These diversified physicochemical forces contributed to the fine anti-interference of BMNSBC to background substances (e.g., inorganic compounds and organic matter) and its remarkable adsorption ability for SMX in diverse real waters. The great magnetization strength of BMNSBC was advantage for its collection and efficient regeneration by NaOH desorption. Additionally, BMNSBC exhibited a outstanding security in view of its low leaching levels of iron (Fe) and total nitrogen (TN). The multiple superiority of BMNSBC enable it to be a prospective material for emerging contaminants (e.g., SMX) purification, also offering a feasible disposal approach for municipal waste (e.g., sludge).
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•Hydrothermal N-doping, magnetization and ball milling co-modified SBC was produced.•BMNSBC showed the superior adsorption ability for SMX and great magnetic sensitivity.•Lewis acid-base, π-π conjugation, pore filling, Fe3O4 complexation were the main forces.•Multiple forces guaranteed the fine tolerance of BMNSBC to high salinity and pH range.•BMNSBC performed a good stability in view of the low leaching levels of Fe and TN.
The environmental implications of antibiotics have drawn widespread attention. Numerous monomer-based bismuth oxide halide catalysts have been extensively studied to remove tetracycline (TC) from ...aquatic environments. Integrating bismuth oxide halide composites with In-based metal organic framework (NH2-MIL-68(In)) might potentially serve as a novel strategy. By meticulously adjusting Cl and I within the composite bismuth halide oxide (B-x), a suite of purpose built heterojunctions (NMB-x) were synthesized, which were engineered to facilitate the efficient photodegradation of TC in simulated and actual aquatic environments. The incorporation of Z-scheme heterojunctions yielded a significant enhancement in photocatalytic responsiveness and charge carrier separation. Notably, NMB-0.3 demonstrated remarkable TC removal efficiency of 88.52 ± 3.05%, which is 3.74 times of B-0.3 within 90 min. The apparent quantum yield was also increased from 8.97% (B-0.3) to 19.68% (NMB-0.3). The removal of TC from natural water bodies was also assessed. Moreover, the photocatalyst concentration, assessed using response surface method, was found to show influential factors on TC removal. In addition, density functional theory (DFT) simulations were employed to identify vulnerable sites within TC. Intermediates and pathways in the photodegradation of TC have also been inferred. Furthermore, a comprehensive environmental toxicity assessment of representative intermediates demonstrated that these intermediates exhibited significantly reduced environmental toxicity compared to TC. This study provides a new approach to the design strategy of efficient and environmentally friendly MOF-based photocatalysts.
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•NH2-MIL-68(In)/BiOCl1−xIx was synthesized and employed for tetracycline removal.•Enhanced photoresponse and effective charge carrier separation were achieved.•Density functional theory was used to predict the susceptibility of TC.•Intermediates were generally less environmentally toxic than tetracycline.
