Kinetic Study on High-Temperature H2S Removal over Mn-Based Regenerable Sorbent Using Deactivation Model.
Ontology highlight
ABSTRACT:
SUBMITTER: Wang J
PROVIDER: S-EPMC8792942 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Biocatalytic nanofiltration membranes (BNMs) exhibit great potentials in organic micropollutants removal attributed to its synergistic effect between enzyme catalysis and membrane separation. However, the difficulties in regeneration of the BNMs halted their economic practicality. Inspired by cell membranes with stimuli-responsive channels, we have developed the temperature-responsive BNMs with nanogating function by poly(N-isopropyl acrylamide) (PNIPAM) modification. PNIPAM modification increases the geometric confinement of the support layer to enzymes, thus improving enzyme loading, inhibiting enzyme leakage, and preventing membrane permeability decline caused by enzyme excess migration and aggregation. By optimizing the concentration of reaction monomers, modification time, and strategies, the PNIPAM-based BNMs show high bisphenol A (BPA) removal efficiency and long-term stability. Furthermore, the PNIPAM-polyethyleneimine-based BNMs can be easily regenerated at 38°C, and the laccase activity and BPA removal efficiency are fully recovered. This work would promote the real application of BNMs in bioconversion, drug delivery, and biosensors.
| S-EPMC8741613 | biostudies-literature
Project description:In this work, porous CeO2 flower-like spheres loaded with bimetal oxides were prepared to achieve effective removal of HCN in the lower temperature region of 30-150 °C. Among all samples, the CeO2 loaded with copper and manganese oxides at the mass ratio of 8/2 (Cu8Mn2/CeO2) exhibited the highest catalytic activity: the HCN removal rate was nearly 100% at 90 °C at the conditions of 120 000 h-1 and 5 vol% H2O, the catalytic activity of which was higher than for other reported catalysts. The introduction of MnO x could improve the dispersion of CuO particles and increase the total acid sites of the prepared samples. It was proved that the synergy between CuO and MnO x , the chemisorption oxygen, the oxygen vacancies, the Cu2+ and Mn4+ all played an important role in determining the good catalytic activity of the prepared samples. NH3-TPD analysis indicated the introduction of MnO x promoted the conversion of NH3 and N2 selectivity by increasing the acid sites of the sample. According to the C, N balance data and FT-IR results, when the temperature was below 30 °C, the removal of HCN over Cu8Mn2/CeO2 was mainly by chemisorption and the HCN breakthrough behaviors corresponded to the Yoon and Nelson's model. When temperature was above 120 °C, the HCN was totally removed by catalytic hydrolysis and catalytic oxidation.
| S-EPMC8695306 | biostudies-literature
Project description:Cyclohexene is an important intermediate during the combustion process of hydrocarbon and oxygenated fuels. In view of the lack of study on the combustion of cyclohexene in air, an experimental and modeling study is performed to investigate the chemistry of cyclohexene-air mixtures under a wide temperature range. The shock tube experiments are conducted at pressures of 2 and 10 atm with equivalence ratios of 0.5, 1.0 and 2.0 to determine the ignition delay times. The ignition data under 10 atm cover a wide temperature range varying from a low temperature of 770 K to a high temperature of 1222 K. No typical negative-temperature-coefficient is observed, but the ignition at low temperatures is shorter than the extrapolation at high temperatures. A detailed kinetic model of cyclohexene oxidation is proposed based on the low temperature mechanism of 1,3-cyclohexadiene and the existing high temperature mechanism of cyclohexene. The developed model reproduces the ignition delay times in air well, but it over predicts the ignition delays in argon conditions at higher temperatures. Sensitivity analyses under different temperatures and equivalence ratios are carried out to identify the key reactions affecting ignition. The reactions of H + O2 = O + OH and hydrogen abstraction reaction of cyclohexene with oxygen (CYHEXEN + O2 = CYHEXEN-3J + HO2) explain the change of ignition delay time of cyclohexene with equivalence ratios. Flux analysis gives the change of main reaction pathways under wide temperatures and different pressures. The retro-Diels-Alder reaction as the most important consumption channel of cyclohexene at the pressure of 2 atm and temperature of 1350 K is greatly suppressed when the pressure is increased to 10 atm, while the hydrogen abstraction reaction becomes the main consumption channel of cyclohexene at the high pressure. The proposed kinetic model for cyclohexene oxidation can be used to develop models of hydrocarbon and oxygenated fuels.
| S-EPMC9044623 | biostudies-literature
Project description:Removal of trace CO impurities is an essential step in the utilization of Hydrogen as a clean energy source. While various solutions are currently employed to address this challenge, there is an urgent need to improve their efficiency. Here, we show that a bead-structured Mg, Cu, and Ce-based sorbent, Mg13CuCeOx, demonstrates superior removal capacity of trace CO from H2 with high stability. The incorporation of Mg boosts sorption performance by enhancing the porous structure and Cu+ surface area. Remarkably, compared to existing pelletized sorbents, Mg13CuCeOx exhibits 15.5 to 50 times greater equilibrium capacity under pressures below 10 Pa CO and 31 times longer breakthrough time in removing 50 ppm CO in H2. Energy-efficient oxidative regeneration using air at 120 °C allows its stable sorption performance over 20 cycles. Through in-situ DRIFTS analysis, we elucidate the reaction mechanism that Mg augments the surface OH groups, promoting the formation of bicarbonate and formate species. This study highlights the potential of MgCuCeOx sorbents in advancing the hydrogen economy by effectively removing trace CO from H2.
| S-EPMC10624860 | biostudies-literature
Project description:A novel, stimuli-responsive composite, based on poly(4-vinylpyridine) (PVP) brushes, end-grafted to montmorillonite clay (GPC), was designed as a regenerable sorbent for efficient removal of pollutants from water. We characterized the novel composite sorbent and its response to pH, employing Fourier transform infrared, X-ray photoelectron spectroscopy, X-ray diffraction, thermogravimetry analysis and zeta potential measurements. In comparison with conventional, electrostatically adsorbed PVP composites (APC), the GPC presented superior characteristics: higher polymer loading without polymer release, higher zeta potential and lower pH/charge dependency. These superior characteristics explained the significantly higher removal of organic and inorganic anionic pollutants by this composite, in comparison with the removal by APC and by many reported sorbents. For example, the filtration (20 pore volumes) of selenate by GPC, APC and a commercial resin column was complete (100%), negligible (0%) and reached 90% removal, respectively. At low-moderate pH, the grafted polymer undergoes protonation, promoting pollutant adsorption, whereas at high pH, the polymer deprotonates, promoting pollutant desorption. Indeed, 'in-column' regeneration of the GPC sorbents was achieved by increasing pH, and upon a second filtration cycle, no reduction in filter capacity was observed. These findings suggest the possible applicability of this stimuli-responsive sorbent for water treatment.
| S-EPMC6104616 | biostudies-literature
Project description:The Mn x Ce y binary catalysts with a three-dimensional network structure were successfully prepared via a polymer-assisted deposition method using ethylenediaminetetraacetic acid and polyethyleneimine as complexing agents. The developed pore structure could facilitate the gas diffusion and accelerate the catalytic reaction for NH3 selective catalytic reduction (SCR). Moreover, the addition of Ce is beneficial for the exposure of active sites on the catalyst surface and increases the adsorption of the NH3 and NO species. Therefore, the Mn1Ce1 catalyst exhibits the best catalytic activity for NO x removal with a conversion rate of 97% at 180 °C, superior water resistance, and favorable stability. The SCR reaction over the Mn1Ce1 catalyst takes place through the E-R pathway, which is confirmed by the in situ diffuse reflectance Fourier transform analysis. This work explores a new strategy to fabricate multimetal catalysts and optimize the structure of catalysts.
| S-EPMC8154236 | biostudies-literature
Project description:NOx abatement has been an indispensable part of environmental catalysis for decades. Selective catalytic reduction with ammonia using V2O5/TiO2 is an important technology for removing NOx emitted from industrial facilities. However, it has been a huge challenge for the catalyst to operate at low temperatures, because ammonium bisulfate (ABS) forms and causes deactivation by blocking the pores of the catalyst. Here, we report that physically mixed H-Y zeolite effectively protects vanadium active sites by trapping ABS in micropores. The mixed catalysts operate stably at a low temperature of 220 °C, which is below the dew point of ABS. The sulfur resistance of this system is fully maintained during repeated aging/regeneration cycles because the trapped ABS easily decomposes at 350 °C. Further investigations reveal that the pore structure and the amount of framework Al determined the trapping ability of various zeolites.
| S-EPMC7876025 | biostudies-literature
Project description:Boron removal was evaluated in the present work by using calcium alginate beads (CA) and a novel composite based on alginate-alumina (CAAl) as sorbents in a batch system. The effects of different parameters such as pH, temperature, contact time, and composition of alginate (at different concentrations of guluronic and mannuronic acids) on boron sorption were investigated. The results confirm that calcium alginate beads (CA) exhibited a better adsorption capacity in a slightly basic medium, and the composite alginate-alumina (CAAl) exhibited improved boron removal at neutral pH. Sorption isotherm studies were performed and the Langmuir isotherm model was found to fit the experimental data. The maximum sorption capacities were 4.5 mmol g-1 and 5.2 mmol g-1, using CA and CAAl, respectively. Thermodynamic parameters such as change in free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were also determined. The pseudo-first-order and pseudo-second-order rate equations (PFORE and PSORE, respectively) were tested to fit the kinetic data; the experimental results can be better described with PSORE. The regeneration of the loaded sorbents was demonstrated by using dilute HCl solution (distilled water at pH 3) as eluent for metal recovery.
| S-EPMC6780931 | biostudies-literature
Project description:A top-down synthetic method was developed for the fabrication of sponge-like Mn3O4 composed of Mn3O4 nanocrystals by decomposition of manganese formate at 200 °C. The samples were characterized in terms of their structural and morphological properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) studies. TEM and SEM images showed that the morphology of sponge-like Mn3O4 structures was mostly retained from the morphology of the manganese formate precursor, which was controlled by the solvothermal process. Large sponge-like Mn3O4 structures exhibiting crystallographic symmetry were prepared under solvothermal treatment for a long time. The XRD pattern showed that the Mn3O4 exhibit a tetragonal hausmannite structure. The results of N2 adsorption analysis indicated that the sponge-like Mn3O4 nanostructures possess high surface area. The possible formation mechanism of Mn3O4 nanostructures has been discussed.
| S-EPMC9067135 | biostudies-literature
Project description:CO oxidation is a widely used model system for understanding fundamental aspects of heterogeneous catalysis. While platinum (Pt) continues to be a reference material for CO oxidation catalysis, poisoning of Pt catalysts presents a critical issue that blocks reaction sites and impedes subsequent reaction steps. Fabrication of CO poison-free Pt catalysts remains a great challenge due to its CO-philic nature. Herein, we report a Pt based catalyst to effectively tackle CO poisoning by tightly anchoring Pt sub-nanoclusters onto Mn-mullite oxide (SmMn2O5) via atomic layer deposition. Superior CO oxidation activity has been observed with a significantly lowered light-off temperature and apparent activation energy. In situ diffuse reflectance infrared Fourier transform spectroscopy analysis, oxygen isotope experiments and density functional theory calculations confirm that the low-temperature activity originates from active oxygen atom sources at the bifunctional interface structure.
| S-EPMC5909126 | biostudies-other