This study describes the operation of two independent parallel laboratory-scale biotrickling filters (BTFs) to degrade different types of binary volatile organic compound (VOC) mixtures. Comparison ...experiments were conducted to evaluate the effects of two typical VOCs, i.e., ethyl acetate (a hydrophilic VOC) and n-hexane (a hydrophobic VOC) on the removal performance of toluene (a moderately hydrophobic VOC) in BTFs ''A" and ''B", respectively. Experiments were carried out by stabilizing the toluene concentration at 1.64 g m-3 and varying the concentrations of gas-phase ethyl acetate (0.85-2.8 g m-3) and n-hexane (0.85-2.8 g m-3) at an empty bed residence time (EBRT) of 30 s. In the presence of ethyl acetate (850 ± 55 mg m-3), toluene exhibited the highest removal efficiency (95.4 ± 2.2%) in BTF "A". However, the removal rate of toluene varied from 48.1 ± 6.9% to 70.1 ± 6.8% when 850 ± 123 mg m-3 to 2800 ± 136 mg m-3 of n-hexane was introduced into BTF "B". The high-throughput sequencing data revealed that the genera Pseudomonas and Comamonadaceae_unclassified are the core microorganisms responsible for the degradation of toluene. The intensity of the inhibitory or synergistic effects on toluene removal was influenced by the type and concentration of the introduced VOC, as well as the number and activity of the genera Pseudomonas and Comamonadaceae_unclassified. It provides insights into the interaction between binary VOCs during biofiltration from a microscopic perspective.
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•Combined experimental and DFT studies can elucidate the role of Pt catalyst.•Adding Pt atom into HY zeolite facilitates C‒C cleavage and formation processes.•The isomerization on ...Pt-HY catalyst required a remarkably low barrier of 0.97 eV.•The Pt-HY catalyst is more selective towards 2MP than 3MP.
In this study, we used several in situ, and spectroscopy analyses to investigate the roles of platinum (Pt) in zeolite-supported Pt catalysts for selective n-alkane isomerization. HY zeolites were synthesized using the rice husk silica and impregnated with Pt precursor by incipient wetness impregnation. Typically, HY zeolites have proved to be active hydrocarbon cracking catalysts. The particular challenge is to find an effective catalyst, which favors the isomerization of n-alkanes without too much cracking. In this work, adding Pt atoms to HY zeolite provides an enhanced multifunctional catalyst for converting n-alkanes to branched hydrocarbons. To understand the effect of Pt, we further investigated the reaction mechanism of n-hexane isomerization to 2–methylpentane (2MP) and 3-methylpentane (3MP) by DFT simulations, using a cluster of 30T HY zeolite modeled through B3LYP + 3D calculations. We found that, at 450 °C, the isomerization on Pt-HY gives higher cracking products. Decreasing temperature to 300 °C yielded greater selectivity of branched hydrocarbons. In addition, DFT calculations demonstrate that the 2MP production via route A1 (C3-C4 bond activation) and a rate-determining step of 0.97 eV proved more thermodynamically and kinetically favorable than the 3MP product. This agrees well with our experimental observations. Consequently, the presence of Pt on the HY zeolite plays an essential role in both CC forming and breaking. Finally, the Pt–HY zeolite is an efficient catalyst for petroleum production, improving the octane number for catalytic performance and product selectivity by isomerizing straight-chain alkanes to their branched chain isomers.
Power-to-gas is a heavily discussed option to store surplus electricity from renewable sources. Part of the generated hydrogen could be fed into the gas grid and lead to fluctuations in the ...composition of the fuel gas. Consequently, both operators of transmission networks and end users would need to frequently monitor the gas to ensure safety as well as optimal and stable operation. Currently, gas chromatography-based analysis methods are the state of the art. However, these methods have several downsides for time-resolved and distributed application and Raman gas spectroscopy is favorable for future point-of-use monitoring. Here, we demonstrate that fiber-enhanced Raman gas spectroscopy (FERS) enables the simultaneous detection of all relevant gases, from major (methane, CH4; hydrogen, H2) to minor (C2–C6 alkanes) fuel gas components. The characteristic peaks of H2 (585 cm–1), CH4 (2917 cm–1), isopentane (765 cm–1), i-butane (798 cm–1), n-butane (830 cm–1), n-pentane (840 cm–1), propane (869 cm–1), ethane (993 cm–1), and n-hexane (1038 cm–1) are well resolved in the broadband spectra acquired with a compact spectrometer. The fiber enhancement achieved in a hollow-core antiresonant fiber enables highly sensitive measurements with limits of detection between 90 and 180 ppm for different hydrocarbons. Both methane and hydrogen were quantified with high accuracy with average relative errors of 1.1% for CH4 and 1.5% for H2 over a wide concentration range. These results show that FERS is ideally suited for comprehensive fuel gas analysis in a future, where regenerative sources lead to fluctuations in the composition of gas.
In Table 1 of this Article, the third row in the furthest right column contains a typographical error and should read 'NH', rather than 'NM', corresponding to n-hexane as the infused liquid.
Les neuropathies périphériques secondaires à une exposition au n-hexane ont été observées chez l’animal en laboratoire et chez l’homme avec une diminution de la vitesse de conduction nerveuse.
Nous ...rapportons le cas d’un jeune de 34 ans polytoxicomane depuis l’âge de 14 ans avec consommation de tabac, cannabis et d’alcool, et sniffeur de colle synthétique. Le début remonte en juillet 2022 par l’installation progressive d’un déficit moteur aux membres inférieurs à prédominance distale compliqué 6 semaine après par le déficit des membres supérieurs associé à un engourdissement des membres en gants et en chaussette. À l’examen les réflexes étaient abolis donnant un tableau de polyneuropathie. L’ENMG a mis en évidence une polyneuropathie démyélinisante sensitivomotrice avec une atteinte axonale secondaire, l’étude du LCR revenue sans anomalie, les sérologies sont revenues négatives et le reste du bilan sanguin était normal.
Le principal métabolite du n-hexane dans l’organisme est le 2,5-hexanedione. Ce métabolite peut provoquer une neuropathie périphérique après une exposition prolongée excessive. Le début est généralement subaigu ou chronique, et l’évolution est progressive avec premiers symptômes d’engourdissement et de sensation de brûlure dans les orteils et des doigts, suivis d’une faiblesse musculaire distale des membres. Le pronostic est souvent favorable.
Le N-hexane provoque une polyneuropathie subaiguë sévère dont le diagnostic repose sur une bonne analyse clinique et électrophysiologie avec élimination des diagnostics différentiels.
We investigated the possible anticancer mechanisms of
Pteris vittata
PV n-hexane extract on MCF-7 breast cancer cell line. Cultured cell lines were treated with various concentrations of this extract ...± Baf-A1 autophagic inhibitor. Cells’ viability, apoptotic markers caspase-7, Bax, and Bcl-2, autophagic markers light chain 3 LC-3 and P62/SQSTM1, and the tumor suppressor P53 and its mRNA were checked by their corresponding methods. Treated cell lines showed significant concentration and time-dependent reductions in cell viability in response to PV
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n-hexane extract and also exhibited a concomitant induction of apoptosis increased chromatin condensation, nuclear fragmentation, and pro-apoptotic Bax, and cleaved caspase-7 levels while decreased Bcl-2 levels and autophagy increased autophagosomes vacuoles, and LC3B II levels while decreased P62/SQSTM1 levels. Moreover, PV
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n-hexane extract-treated cells showed significant increases in the P53 and its mRNA levels. The addition of Baf-A1 reversed the PV
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n-hexane extract autophagic effects and increased apoptotic cell percentage with a much increase in the cleaved caspase-7 and P53 protein and its mRNA levels. We concluded that the PV
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n-hexane extract exhibits cytotoxic effects on the MCF-7 cell line with significant reductions in cell viability and concomitant autophagy and apoptosis induction. Inhibition of autophagy in the PV-treated MCF-7 cells enhances apoptosis via a p35-dependent pathway.
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•Synergy of metal and acid sites in the Ni-SAPO-11 catalyst is improved by β addition.•A micro/nano-meter intimacy of metal and acid sites is preferred for the Ni-SAPO-11.•The ...optimized catalyst exhibits comparable isomers yield to the commercial one.
Catalytic performance of the hydroisomerization catalysts is strongly influenced by the synergy between metal and acid sites which includes synergy in quantity and intimacy. Here, the metal-acid synergy in quantity over the Ni-SAPO-11 catalyst with excessive metal sites was improved via adding a small amount of β zeolite, and the metal-acid synergy in intimacy was also discussed. The β zeolite was introduced into the Ni-SAPO-11 (obtaining Ni-SAPO-11-β catalyst) using an in-situ solid synthesis method by grinding nickel source with crystallized β and precursors of SAPO-11 before crystallization. The β zeolite is well dispersed in the Ni-SAPO-11-β catalyst with strong interaction with SAPO-11. Compared with Ni-SAPO-11, acidity of of the Ni-SAPO-11-β catalyst is enhanced and a better metal-acid synergy in quantity is obtained. The catalytic performance was assessed for n-hexane hydroisomerization and kinetic measurements were carried out. The Ni-SAPO-11-β catalyst with relatively lower activation energy outperforms the Ni-SAPO-11 in terms of activity and isomers yield due to the improved metal-acid synergy. Its isomers yield is comparable to the optimal value over a commercial hydroisomerization catalyst (Pt based). To further study effect of the metal-acid intimacy, mechanical mixtures of Ni-SAPO-11 and β were prepared and compared with the Ni-SAPO-11-β catalyst in catalytic behavior. Nanometer or micrometer scale intimacy between nickel and acid sites perform better than millimeter or larger scale intimacy. Thus the nickel based hydroisomerization catalyst with high catalytic performance is obtained here and a preferred metal-acid intimacy is proposed.
Emissions of n-alkanes are facing increasingly stringent management challenges. Biotrickling filtration in the presence of surfactants is a competitive alternative for the enhanced removal of ...n-alkanes. Herein, sodium dodecyl benzene sulfonate (SDBS) was added into the liquid phase feeding a biotrickling filter (BTF) to enhance the removal of various short-chain n-alkanes from n-hexane (C6) to methane (C1). The removal performance of C6–C1 and microbial response mechanisms were explored. The results showed that the removal efficiency (RE) of n-alkanes decreased from 77 ± 1.3 to 35 ± 5.6% as the carbon chain number of n-alkanes decreased from C6 to C1, under the conditions of an n-alkane inlet load of 58 ± 3.0 g/m3·h and EBCT of 30 s. The removal performance of n-alkanes was enhanced significantly by the introduction of 15 mg/L SDBS, as the RE of C6 reached 99 ± 0.7% and the RE of C1 reached 74 ± 3.3%. The strengthening mechanisms were that the apparent Henry’s law coefficient of n-alkanes decreased by 11 ± 1.4–30 ± 0.3%, and the cell surface hydrophobicity of microorganisms improved from 71 ± 5.6 to 87 ± 4.0% with the existence of SDBS. Moreover, the presence of SDBS promoted the succession and activity of the microbial community. The activities of alkane hydroxylase and alcohol dehydrogenase were 5.8 and 5.9 times higher than those without SDBS, and the concentration of the cytochrome P450 gene was improved 2.2 times. Therefore, the addition of SDBS is an effective strategy that makes BTF suitable for the removal of various n-alkanes from waste gas streams.
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•We used DFT calculations to study n-hexane cracking over zeolites.•Trends in activation barriers and transition state energies relate to zeolite acidities.•Simple SISSO descriptors ...predicts Ea and ETS, avoiding time-consuming calculations.
Significant computational cost arises in calculating the pathways for heterogeneous catalyzed cracking reactions by quantum chemical means. This can prevent the screening of catalysts and thus the identification of potent ones. To reduce this computational cost, we investigate if recently developed nonlinear regression methods can be employed to predict transition state and activation energies of species arising along the reaction pathways. Cracking of n-hexane catalyzed by the zeolites ZSM-5, FAU, FER, and MOR isomorphously substituted with B, Al, Ga, and Fe serves as an example. We first derive the relevant quantities by density functional theory (DFT) calculations. The trend in activation barriers (Ea) and transition state energies (ETS) is found to be closely related to their acidities. Standard regression analysis already shows that transition state energies can be well reproduced by linear functions of the energies of the final states, while activation barriers can be moderately well predicted from deprotonation energy and dipole moment of the zeolite cluster. In order to enhance the prediction accuracy, especially for Ea, we use the sure-independence screening and sparsifying operator (SISSO) method. This machine-learning method can search a large pool of combinations of physical descriptors and select the best ones. We derive a simple mathematical expression that predicts ETS and Ea values with reasonable accuracy, thus making it possible to avoid the time-consuming calculation of the reaction pathway. Statistical tests indicate that the expressions suggested by SISSO are reasonably robust as well, at least within the limited data set.
Biodegradation of hydrophobic volatile organic compounds (VOCs) such as n-hexane is limited by their poor accessibility. Constructing fungal-bacterial degradation alliances is an effective approach, ...but the role of those fungi without the capability to degrade VOCs may have been overlooked. In this study, a non-n-hexane-degrading fungus, Fusarium keratoplasticum FK, was utilized to enhance n-hexane degradation by the bacterium Mycobacterium neworleansense WCJ. It was shown that strain WCJ removed 64.84% of n-hexane (at a concentration of 648.20 mg L−1) over 3 d, and 84.04% after introducing strain FK. Microbial growth kinetic studies revealed that the growth of strain WCJ was also promoted. Through a stepwise adsorption-degradation experiment combined with qPCR technology, it was found that the strain WCJ could utilize the n-hexane pre-adsorbed by strain FK, with an increase in copy number from 108.2662 to 108.7731. Therefore, the non-degrading fungi can improved the accessibility of n-hexane by providing n-hexane adsorbed by the mycelium to the degrading bacteria. In addition, the adsorption tests and characterization of the fungal samples before and after Soxhlet extraction indicated that the adsorption of n-hexane on strain FK conformed to Lagergren's pseudo-second-order kinetics and Freundlich adsorption isotherms, and was correlated with the presence of lipids and nonpolar groups. This study emphasizes the potential role of non-degrading fungi in bioremediation and proposes a viable strategy to enhance the bacterial degradation of hydrophobic VOCs.
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•The introduction of strain FK increased the n-hexane removal to 84.04%.•The k value of strain WCJ was promoted by strain FK from 0.0395 to 0.1681 h−1.•Adsorption of VOCs by fungi through hyphae were confirmed by IFM and kinetics.•Bacterial degradation of the adsorbed n-hexane was indirectly proven by qPCR.•Lipids and nonpolar groups of fungi were found to contribute to the adsorption.
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