Linear energy scaling relations constitute the basis of computational design of catalysts using a descriptor-based approach. Herein, we demonstrated the general applicability of the scaling relations ...in Brønsted acid zeolite catalysis with acid strength. Using ammonia adsorption enthalpy as the descriptor of acid strength, the scaling relations of transition state (TS) energies were established in CHA/AlPO-34-structured zeolites or zeotypes among a series of elementary reactions with relevance to methanol-to-olefins conversion, for example, methylation, ethylation, hydride transfer, cyclization, and cracking. The scaling slope, e.g. the sensitivity of TS enthalpy versus acid strength, was revealed to approximately linearly correlate with the charge variation of the framework in the reaction. These findings enable fast and accurate prediction of the TS energies of systems with different acid strengths or compositions in one given framework topology, similar to those in metal or oxide catalysis in which the scaling relations are established with composition in one specific surface, and therefore open up an avenue for the rational design of zeolite catalysts for complex industrially relevant reactions.
The direct syngas conversion to olefins, aromatics and other hydrocarbons has attracted increasing attention while unraveling the complex reaction mechanism is of great challenge. It was recently ...demonstrated that zinc-exchanged zeolites could selectively convert syngas to alkanes, particular ethane, and Zn–O–Zn motif is likely the intrinsic active site. The underlying reaction network however remains ambiguous. Herein, we proposed a reaction mechanism for the direct conversion of syngas to light alkanes including methane and ethane using density functional theory calculations in periodic Zn–O–Zn-ZSM-5 zeolite model. The evolution of syngas to ethane follows the sequence of CO → CH2O → CH2CO → CH3CHO → C2H6. The activation of CO to formaldehyde initiates the reaction. The Zn–O–Zn site can readily be reduced by CO to Zn–Zn site, which either inserts aldehydes to form Zn–O-CnH2n-Zn motif for chain propagation to higher aldehydes, or converts aldehydes to alkanes for chain termination. Ketene is the first intermediate after the C–C bond coupling between Zn–O–CH2–Zn and CO. Both the structures and the evolution sequence of the involved intermediates in the proposal (formyl, methylene, acetyl, ethyl) coincide quite well with experimentally quasi in-situ characterized results. The proposed reaction network consisting of initiation, propagation and termination sub-cycles unifies the formation pathway of methane, ethane, and higher alkanes, and bears some resemblance to the Fischer-Tropsch synthesis for syngas conversion. This theoretical work thus further vindicates the critical role of Zn–O–Zn site and may proffer some implications to tailor alkane selectivity in metal-exchanged zeolites for syngas conversion.
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•Reaction network of syngas to alkanes in Lewis Zn–O–Zn-ZSM-5 were established.•Ethane formation follows the sequence of CO .→ CH2O → CH2CO → CH3CHO → C2H6.•Reaction consists of chain initiation, propagation, and termination sub-cycles.•Ketenes were involved in chain propagation.
In a circular economy, an enterprise should pursue long-term business and economic opportunities for environmental and societal benefits. One of the critical issues in industries with a circular ...economy is the development of the reverse logistics system for semi-finished product packaging and shipping. There are several challenges while designing this system; for example, the use of reusable semi-finished product shipping boxes and a logistics system for shipping the products and returning these boxes. In this research, under the context of global manufacturing, a logistics system for reusable semi-finished product packaging in LCD panel industry is studied. The cost models of semi-finished product packaging in a traditional logistics mode and a green logistics mode are introduced. In the green logistics mode, the shipping boxes are redesigned to be reusable and capable of accommodating multiple various-sized panels simultaneously. The cost models involve material cost, shipping, and recycling cost. The economic performances of the traditional and green logistics modes at different package recycling levels are analyzed. The results show that the total cost of the green logistics mode is beneficial, always lower than that of the traditional logistics mode, even at a low recycling rate (30%). In addition, in the green mode, the material cost of shipping boxes is the most influential sector of the total cost.
Zeolite catalyzed methanol-to-olefins (MTO) conversion proceeds through a hydrocarbon pool mechanism involving a series of elementary steps. The nature of the active hydrocarbon pool species is yet ...to be made clear in different zeolites. In this work, both aromatic-based and olefin-based cycles in H-SAPO-34 and H-SSZ-13 were systematically investigated using periodic DFT calculations with a van der Waals (vdW) interaction corrected XC functional. Combining static adsorption energies and interconversion thermodynamics, we theoretically proved that 1,2,4,5-tetramethylbenzene (1,2,4,5-TMB) is the primary component of methylbenzenes in CHA-structured zeolites. The energetic span model was employed to compare the kinetics of both cycles in which 1,2,4,5-TMB and 2,3-dimethyl-2-butene (iso-C6) were taken as hydrocarbon pool species. Both cycles follow a similar sequence of elementary steps. We demonstrate that the iso-C6-based cycle is kinetically facile for the MTO conversion in H-SAPO-34 and H-SSZ-13. The rate-determining transition states are identified as the propagation of ethyl side chain in the 1,2,4,5-TMB-based cycle and the cracking of alkyl chain in the iso-C6-based cycle. Our results show that the reactivity of 1,2,4,5-TMB increases from H-SAPO-34 to H-SSZ-13. The stabilities of carbenium ions, important intermediates in the olefin-based cycle, increase with their size and zeolite acidity. These theoretical insights from the energetic span model enable us to highlight the importance of the olefin-based cycle in MTO conversion and understand the dependence of the reaction mechanism on zeolite frameworks.
Vimentin (VIM), an indispensable protein, is responsible for the formation of intermediate filament structures within cells and plays a crucial role in viral infections. However, the precise role of ...VIM in classical swine fever virus (CSFV) infection remains unclear. Herein, we systematically investigated the function of VIM in CSFV replication. We demonstrated that both knockdown and overexpression of VIM affected CSFV replication. Furthermore, we observed by confocal microscopy the rearrangement of cellular VIM into a cage-like structure during CSFV infection. Three-dimensional (3D) imaging indicated that the cage-like structures were localized in the endoplasmic reticulum (ER) and ringed around the double-stranded RNA (dsRNA), thereby suggesting that VIM was associated with the formation of the viral replication complex (VRC). Mechanistically, phosphorylation of VIM at serine 72 (Ser72), regulated by the RhoA/ROCK signaling pathway, induced VIM rearrangement upon CSFV infection. Confocal microscopy and coimmunoprecipitation assays revealed that VIM colocalized and interacted with CSFV NS5A. Structurally, it was determined that amino acids 96 to 407 of VIM and amino acids 251 to 416 of NS5A were the respective important domains for this interaction. Importantly, both VIM knockdown and disruption of VIM rearrangement inhibited the localization of NS5A in the ER, implying that VIM rearrangement recruited NS5A to the ER for VRC formation. Collectively, our results suggest that VIM recruits NS5A to form a stable VRC that is protected by the cage-like structure formed by VIM rearrangement, ultimately leading to enhanced virus replication. These findings highlight the critical role of VIM in the formation and stabilization of VRC, which provides alternative strategies for the development of antiviral drugs.
Classical swine fever (CSF), caused by classical swine fever virus (CSFV), is a highly infectious disease that poses a significant threat to the global pig industry. Therefore, gaining insights into the virus and its interaction with host cells is crucial for developing effective antiviral measures and controlling the spread of CSF. Previous studies have shown that CSFV infection induces rearrangement of the endoplasmic reticulum, leading to the formation of small vesicular organelles containing nonstructural protein and double-stranded RNA of CSFV, as well as some host factors. These organelles then assemble into viral replication complexes (VRCs). In this study, we have discovered that VIM recruited CSFV NS5A to form a stable VRC that was protected by a cage-like structure formed by rearranged VIM. This enhanced viral replication. Our findings not only shed light on the molecular mechanism of CSFV replication but also offer new insights into the development of antiviral strategies for controlling CSFV.
The electrolyte is a key component in determining the performance of sodium-ion batteries. A systematic study is conducted to optimize the electrolyte formulation for a Sb2S3/graphene anode, which is ...synthesized via a facile solvothermal method. The effects of solvent composition and fluoroethylene carbonate (FEC) additive on the electrochemical properties of the anode are examined. The propylene carbonate (PC)-based electrolyte with FEC can ensure the formation of a reliable solid-electrolyte interphase layer, resulting in superior charge–discharge performance, compared to that found in the ethylene carbonate (EC)/diethyl carbonate (DEC)-based electrolyte. At 60 °C, the carbonate-based electrolyte cannot function properly. At such an elevated temperature, however, the use of an N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte is highly promising, enabling the Sb2S3/graphene electrode to deliver a high reversible capacity of 760 mAh g–1 and retain 95% of its initial performance after 100 cycles. The present work demonstrates that the electrode sodiation/desodiation properties are dependent significantly on the electrolyte formulation, which should be optimized for various application demands and operating temperatures of batteries.
Summary of main observation and conclusion
Understanding and optimizing structure of active sites is of significance in zeolite catalysis. Benzene ethylation is an industrially important process ...catalyzed by H‐MCM‐22 zeolite; while the active sites still remain elusive. In this work, density functional theory (DFT) calculations were employed to investigate the benzene ethylation at two different types of Brønsted acid sites (BAS) in H‐MCM‐22 zeolite, namely the internal cavity (IC) acid site and the external surface (ES) acid site. Both the stepwise and concerted pathways were addressed. The comparison of the calculated energetics of two pathways indicates that the benzene ethylation reaction primarily proceeds via the concerted pathway at both the IC and ES acid sites of H‐MCM‐22. The calculated overall Gibbs free energies at reaction condition (473 K and 3.5 MPa) on the IC and ES acid sites are 90 and 86 kJ/mol, with the rate constants of 1.20 × 103 and 2.92 × 103 s–1, respectively. It indicates that benzene ethylation could occur both on the IC and ES acid sites, with the catalytic activity of IC acid site being slightly lower than that of ES acid site. Furthermore, we theoretically reveal that the acid strength at the ES site is slightly weaker than that at the IC site via the frequency shift after the adsorption of CO. The differences in dispersion interaction between ES and IC sites are also quantified by the adsorption of base molecules with different sizes. The calculated results in this work demonstrate that the acid sites at the external surface of H‐MCM‐22 zeolites are suitable for benzene ethylation to produce ethylbenzene, providing theoretical implications for tailoring the distribution of active sites in H‐MCM‐22 zeolite.
Let H be a uniform hypergraph with cut vertices, which is a coalescence of two nontrivial connected sub-hypergraphs (called branches) at some vertex. The traces of the adjacency tensor A(H) of H, ...simply called the traces of H, are important in the expression of the determinant and the characteristic polynomial of A(H), and are closely related to the Estrada index of H. In this paper we give a formula for the traces of H in terms of those of its branches, and get some perturbation results on the traces of H when a branch of H attached at one vertex is relocated to another vertex. We prove that among all hypertrees with fixed number of edges, the hyperpath is the unique one with minimum Estrada index and the hyperstar is the unique one with maximum Estrada index.
The hygroscopicity and phase state of atmospheric aerosols, depending on relative humidity (RH), dominate their impacts on global climate and heterogeneous atmospheric chemistry. It is challenging to ...achieve full course measurements on hygroscopic mass growth factors (MGFs), deliquescence relative humidity (DRH), efflorescence relative humidity (ERH) and efflorescence kinetics of aerosols at different ambient RH, which concerns the gas, liquid and solid phases. The combination of a rapid scan vacuum FTIR and a RH pulsed controlling system allowed us to directly and synchronously determine ambient RH and MGFs of aerosols, as well as nucleation rates in the efflorescence process with a subsecond time resolution. With an excellent signal-to-noise ratio and high time resolution spectra, the vacuum FTIR method allowed for real-time in situ measurements of water partitioning between gas and particle phases as it changed with RH, as well as the ratio between the number of crystallized aerosol droplets and the total number of particles during the efflorescence of aerosols. The hygroscopicity and efflorescence kinetics of NaCl and (NH4)2SO4 aerosols were studied in linear RH change mode and in pulsed RH change mode. The measured MGF values, DRH and ERH agreed well with theoretical data from the Extended Aerosol Inorganic Model (EAIM) and literature for both the linear and pulsed RH change modes. In addition, the pulsed RH mode also provided both heterogeneous and homogeneous nucleation rates for NaCl and (NH4)2SO4 aerosols. There were significant advantages of the vacuum FTIR method combined with the pulsed RH controlling technique. First, the RH was continuously changed and was determined in real-time with a time resolution of 0.12 s in the pulsed mode. During the RH change process, the water content in the aerosols was measured synchronously with the same time resolution, allowing for high-efficiency measurements of MGFs, ERH and DRH. The deviations of measured MGFs from the EAIM predictions in the RH range of 75–55% were less than ±3.3%. Second, FTIR spectroscopy was sensitive to phase transitions, which provided quantitative information on the ratio of the number of aerosols transformed from droplets to solid particles at ERH, allowing for the measurement of nucleation kinetics during the efflorescence of aerosols.
•RH, growth factors and nucleation rates of aerosols are synchronously determined.•The complete hygroscopic cycle data of aerosols can be determined within 1 min.•The nucleation mode of particles is first explored based on the measured ERH range.•Heterogeneous and homogeneous nucleation rates are both obtained in the pulsed mode.
This study designed and synthesized a series of novel ursolic acid derivatives in an attempt to develop potent antitumor agents. Their structures were confirmed using MS, IR, 1H NMR and 13C NMR. The ...inhibitory activities of the title compounds against the MGC-803 (gastric cancer cell) and Bcap-37 (breast cancer cell) human cancer cell lines were evaluated using standard MTT assay in vitro. The pharmacological results showed that some of the compounds displayed moderate to high levels of antitumor activities against the tested cancer cell lines and that most exhibited more potent inhibitory activities compared with ursolic acid. The mechanism of compound 4b was preliminarily investigated by acridine orange/ethidium bromide staining, Hoechst 33258 staining, TUNEL assay and flow cytometry, which revealed that the compound can induce cell apoptosis in MGC-803 cells.
Display omitted A series of new ursolic acid derivatives containing an acyl piperazine moiety were synthesized, and were found possessing good antitumor activities as well as cell apoptosis inducing activities in MGC-803 cells.
► A series of new ursolic acid derivatives containing acyl piperazine were synthesized. ► The new compounds showed good antiproliferative activities against tumor cells. ► Further mechanism study indicates that the new compounds can induce cell apoptosis.
