查看更多>>摘要：Carbon-based catalyst-activated persulfate-driven advanced oxidation processes (AOPs) have received great attention for wastewater treatment. Herein, a magnetic Fe-doped activated carbon (FeC2O4/AC) was successfully prepared via a conventional method using FeC2O4 as an iron source and Zoysia sinica as biomass. FeC2O4/AC was characterized and used to activate peroxymonosulfate (PMS) for Rhodamine B (RhB) degradation. The influence of various factors on RhB removal was evaluated, including initial pH, temperature, coexisting ions, RhB concentration, PMS concentration and catalyst dosage. Under the optimized condition, the removal efficiency of FeC2O4/AC for RhB (300 mg/L) reached up to 97% within 150 min. Radical scavenging results and EPR experiments confirm that singlet-oxygen (O-1(2)) was confirmed as the main active species in the degradation of RhB in the FeC2O4/AC/PMS system. More importantly, the possible route of O-1(2) generation was revealed: the synergistic effect of Fe species and the activated carbon acts as a crucial part in promoting the PMS activation and contributing to the generation of O-1(2). The reaction rate constant (k(obs)) of FeC2O4/AC is about 7.4 times that of pure AC, and the excellent leaching rate of Fe2+ (< 0.09%) proves that this material is an excellent catalyst. This research on the development of Fe-doped activated carbon with high activity and high stability has profound implications for the effective treatment of organic wastewater.
查看更多>>摘要：Photocatalysis utilized solar energy with metal oxide semiconductors has been considered as one of the attractive green routes for organics' conversion. The construction of high-density co-catalytic sites is essential for the surface reaction kinetics. In this work, a high-efficiency mesoporous TiO2 decorated with single atomic Pt loading of 1 at% (2.1 wt%) had been successfully achieved. The high specific surface area of mesopomus TiO2 affords adequate physical surface for the resident of atomic Pt, thus stabilizing a high areal density of single-atom reaction sites. The optimized single-atom Pt/TiO2 revealed a performance of 4.1 mmol/h/g(cat) for photocatalytic oxidation of benzyl alcohol under visible light irradiation that is 3.8 folds than that of Pt-modified commercial TiO2 photocatalysts. The reactivity will further enhance after the introduction of plasmonic Au nanoparticles and the finally sample (1 at% Pt-0.075 at% Au)/TiO2-MP exhibited salient activity (4.5 mmol/h/g eat ) and stability. This work paves a potential way to boost the performance of metal oxide semiconductors for green photocatalytic conversion of organics.
查看更多>>摘要：Alkylation reaction of benzene and methanol produces desirable product p-xylene, thus understanding the structure-performance relationship in alkylation reaction is significant. Herein, the diffusion behavior of representative components (i.e. benzene, methanol, olefin and alkylbenzene) involved in the alkylation reaction catalyzed by Al-substituting ZSM-5 (H-ZSM-5) zeolite at 673 K was studied based on molecular dynamics simulations. As a result, the self-diffusion coefficients (Ds) of methanol and benzene at 673 K in H-ZSM-5 zeolite are 2.97 x 10(-8 )and 6.50 x 10-(12) m(2) s(-1), respectively; while in CH3-ZSM-5 zeolite, the presence of CH3O- intermediates does favor to the diffusion of benzene and alkylbenzene, especially p-xylene. Furthermore, due to the distinguished dynamic diameters compared with pore sizes, the reaction species exhibit anisotropic diffusion along x-, y-and z -direction of zeolite channel. This work may not only provide an insight into the diffusion mechanism for alkylation reaction of benzene and methanol, but also help guide the design of zeolite catalysts.
查看更多>>摘要：The atomic model of carbon xerogel microporous structure is reconstructed by a modified virtual porous carbon (VPC) model. The physical parameters of the reconstructed model, especially the predicted nitrogen adsorption isotherm, agree well with the experimental data. Then, the adsorption and diffusion of the gas in carbon xerogel microporous structure are investigated at the pore-scale. The results show that decreases of isosteric adsorption heat and the excess adsorption in carbon xerogel microporous structure are majorly contributed by the desorption of adsorbates in ultramicropores with the temperature increasing. The microporous structure appears a strong selectivity for oxygen in the air, due to the molecular sieving effect and the strong solid-fluid interaction between the pore wall and oxygen. As the desorption of oxygen in ultramicropores due to its increasing steric repulsion with the temperature rising from 298 K to 573 K, the selectivity of microporous structure for oxygen decreases, and the gap between isosteric adsorption heat for nitrogen and oxygen is narrowed. The systemic migration of gas molecules from the ultramicropores to the wider area is observed by the pore-scale analysis, and it makes the gas diffusivity appear an approximately linear relationship with the temperature.
Marcucci, Silvio Miguel ParmegianiZanin, Gisella MariaArroyo, Pedro Augusto
8页
查看更多>>摘要：The mesoporous silicas were extensively used in lipase immobilization due to the high specific area, pore diameter, and the possibility of surface modification. Due to this, the present work aimed to synthesize the SBA 15 with different pore diameters (S8 with 9.1 nm and S23 with 23 nm) and modify the silica surfaces with tin (SnS8 and SnS23), a little-explored technique for immobilization, for Burkholderia cepacia lipase immobilization by covalently bond between the functional group in the enzyme and the metal. The tin-modified silica (SnS23) derived from the pore expansion of the SBA-15 was the support with the largest pore size (25 nm) and led to the highest specific activity of the immobilized enzyme (SnS23B, 268 +/- 12 U/mg). In the leaching tests, no lipase was detected in the buffer solution used for lipase desorption, indicating the strong interaction between lipases and modified silicas.
查看更多>>摘要：Aiming for materials compatible with enhanced gold/palladium trap and open active sites for green Suzuki coupling, Zr-Ll/L2 of UiO-66 topology was feasibly modified with amine and imidazole a-diimine side-groups. Excellent extraction percentage (>98%), high selectivity and outstanding recyclability were obtained by the adsorbent in recovering gold from river water. The saturate adsorption capacity was calculated to reach 1582.5 mg g(-1), outperforming most reported sorbents. Furthermore, up to 99% palladium recovery performance in less than 5 min was achieved. Palladium-loaded sample exhibit perfect conversion and excellent recyclability for aqueous-phase Suzuki coupling at room temperature. In this study, the synergistic interactions (coordination, electrostatic interaction and hydrogen bonding) in the material benefit for the remarkable extraction performance of gold and palladium in river, preventing palladium leaching out and aggregation.
查看更多>>摘要：Nucleation and growth of zeolites are closely related to the state of amorphous aluminosilicate precursors which may lead to different crystallization pathways. This article provided a deep understanding of the formation mechanisms of EUO from different precursors generated through hydrolysis of tetraethoxysilane (TEOS) at different temperatures as well as by introducing the aluminum source at different time. A combination of diffraction, NMR and microscopy techniques was applied to characterize the assembly and evolution of amorphous species during the synthesis of EUO zeolites. Hydrolysis temperature of TEOS was closely associated with the nucleation rate of EUO. The evolution of worm-like precursors to bulk precursors was accelerated when the gel was hydrolyzed at low temperature. Moreover, the introduction of sodium aluminate could also promote the nucleation when a homogeneous gel with uniform Si-Al distribution was formed. When the gel environment was non-uniform, amorphous-to-crystalline transformation involved a two-step pathway, beginning with the appearance of *MRE due to the existence of Si-rich regions, followed by inter-crystalline transformation to EUO. Such crystallization pathway led to the formation of EUO single crystal around 1.5 mu m. Given that numerous zeolite syntheses involve the formation of metastable precursors with heterogeneous composition, the choice of gel preparation procedure in this study may be generalized to other related materials.
查看更多>>摘要：Porous carbons with abundant pores and good conductivity are the dominant sulfur host in lithium sulfur batteries. Herein, a facile simultaneous activation/carbonization with inexpensive FeCl3 and ZnCl2 as activators is employed to prepare sucrose derived porous carbon at low temperature of 600 degrees C. The as-prepared carbon materials not only have partial graphitization due to the FeCl3 catalysis, but also show abundant hierarchical porous structure with high specific surface area of 2104 m(2) g(-1) and large pore volume of 1.29 cm(3) g(-1), whilst obtaining a high yield of about 30 wt%. When used to encapsulate sulfur, the abundant porous structure is conductive to immobilizing polysulfides and buffering volume effect during charge/discharge. Owing to these structure merits and good electrical conductivity, the corresponding porous carbon/sulfur cathode with a sulfur content of 53 wt% delivers high first discharge capacity of 811 mAh g-1 at 0.2C. Even with 75 wt% sulfur, the reversible capacity of 446 mAh g-1 are also obtained after 200 cycles at 0.2C. Especially, a durable long life of 1000 cycles with a low capacity decay of 0.035% per cycle can be achieved at 1C when the sulfur content is 45 wt %. This work provides a scientific foundation for preparing high-performance porous carbon applied in energy related storage/conversion.
查看更多>>摘要：Heterogeneous catalytic reactions are strongly relying on metal-based catalysts due to their outstanding activity. However, the activity of catalysts depends on the size of metal nanoparticles (MNPs). Herein, Pd, Pt and Au NPs were confined in the nanoconfined spaces of template occluded as-made KIT-6 (AK) via facile single-step strategy. The metal precursors are directly inserted into the nanoconfined channels of AK by grinding. Subse-quent reduction removes template P123, decompose precursors and reduce MNPs in one step in comparison to multiple ones of traditional strategies. The results demonstrated that the nanoconfined channels between tem-plate and silica walls of AK where MNPs locate, MNPs interaction with AK and single-step strategy promote the formation of MNPs with smaller size. The characterization results confirmed uniform MNPs distribution with single metallic state without any metallic oxides. The smaller size of MNPs in catalysts endows excellent catalytic activity and the order of para-nitrophenol (p-NP) reduction to p-aminophenol (p-AP) and methylene blue (MB) to leucomethylene blue (LMB) is AK-Pd > AK-Pt > AK-Au. Also, the reaction rate constant of AK-Pd is much better than AK-Pt and AK-Au catalysts. Moreover, the synthesized catalysts exhibited good reusability and are highly promising for utilization in catalytic reactions.
查看更多>>摘要：Complex large models of multi-scale microstructures of porous media do not exist in a manner adequately efficient to render their comprehensive analysis of textural and structural properties possible. The simulation of experimental processes, such as gas adsorption, raises two issues. First, the modeling of these complex materials must be sufficiently realistic. This implies that the numerical twin of the porous material must consider three essential aspects: a spatial structure defining different scales of porosity, comparable textural and structural properties of the real material and irregular pore morphology. Secondly, efficient algorithms must be developed to mimic the quasi-static phase transition behavior of fluids in a realistic manner. The proposed simulation approach allows to handle the physico-chemical phenomena inside complex materials by means of well-established mathematical operators. Morphological operators are used to efficiently mimic processes such as surface adsorption and pore filling. Fluid percolation that provokes phase transition is simulated by labeled connected components. This method relies entirely on morphological and structural operators, which has the advantage of substantially reducing the calculation time compared to that of density functional theory and molecular simulations-based approaches. In contrast to oversimplified models characterized by ideal pore shape and unconnected pores, our approach enables us to calculate the adsorption isotherm of realistic random models where pore morphology and porous network topology are unknown beforehand. We demonstrate that our model succeed in reproducing the adsorption isotherm of two well-known model materials (SBA-15 and KIT-5) and mesoporous alumina, represented by Cox Boolean models.
NSTL
Elsevier