Effect of mesopore spatial distribution of HZSM-5 catalyst on zinc state and product distribution in 1-hexene aromatization

1-hexene aromatization is a promising technology to convert excess olefin in fluid catalytic cracking(FCC)gasoline to high-value benzene(B),toluene(T),and xylene.Besides,the increasing market demand of xylene has put forward higher requirements for new generation of catalyst.For increasing xylene yield in 1-hexene aromatization,the effect of mesopore structure and spatial distribution on product distribution and Zn loading was studied.Catalysts with different mesopore spatial distribution were prepared by post-treatment of parent HZSM-5 zeolite,including NaOH treatment,tetra-propylammonium hydroxide(TPAOH)treatment,and recrystallization.It was found the evenly distributed mesopore mainly prolongs the catalyst lifetime by enhancing diffusion properties but reduces the aromatics selectivity,as a result of damage of micropores close to the catalyst surface.While the selectivity of high-value xylene can be highly promoted when the mesopore is mainly distributed interior the catalyst.Besides,the state of loaded Zn was also affected by mesopores spatial distribution.On the optimized catalyst,the xylene selectivity was enhanced by 12.4%compared with conventional Zn-loaded parent HZSM-5 catalyst at conversion over 99%.It was attributed to the synergy effect of mesopores spatial distribution and optimized acid properties.This work reveals the role of mesopores in different spatial positions of 1-hexene aromatization catalysts in the reaction process and the influence on metal distribution,as well as their synergistic effect two on the improvement of xylene selectivity,which can improve our understanding of catalyst pore structure and be helpful for the rational design of high-efficient catalyst.

Fabrication of a nano-sized ZSM-5 zeolite with intercrystalline mesopores for conversion of methanol to gasoline

Carbon deposition during methanol to hydrocarbons leads to the quick deactivation of ZSM-5 catalyst and it is one of the major problems for this technology. Decreasing the crystal size or introducing mesopores into ZSM-5 zeolites can improve its diffusion property and decrease the coke formation. In this paper, nano-sized ZSM-5 zeolite with intercrystalline mesopores combining the mesoporous and nano sized structure was fabricated. For comparison, the mesoporous ZSM-5 and nano-sized ZSM-5 were also prepared. These catalyst samples were characterized by XRD, BET, NH3-TPD, TEM, Py-IR and TG techniques and used on the conversion of methanol to gasoline in a fixed-bed reactor at T=405 degrees C, WHSV =4.74 h(-1) and P=1.0 MPa. It was found that the external surface area of the nano-sized ZSM-5 zeolite with intercrystalline mesopores reached 104 m(2)/g, larger than that of mesoporous ZSM-5 (66 m(2)/g) and nano sized ZSM-5 (76 m(2)/g). Catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores was 93 h, which was only longer than that of mesoporous ZSM-5 (86 h), but shorter than that of nano sized ZSM-5 (104 h). Strong acidity promoted the coke formation and thus decreased the catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores though it presented large external surface that could improve the diffusion property. The special zeolite catalyst was further dealuminated to decrease the strong acidity. After this, its coke formation rate was slowed and catalytic lifetime was prolonged to 106 h because of the large external surface area and decreased weak acidity. This special structural zeolite is a potential catalyst for methanol to gasoline reaction. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Research on a New Process of Preparation for Nano-SiO_2 with High Activity and Mesopores

Nano-SiO_2 with high activity and mesopores was prepared through sol-gel synthesis followed by low-temperatureheat treatment and ball milling firstly in our experiments. TEM was performed to measure particle sizes. Nitrogenadsorption experiments were carried out to estimate specific surface area, porous distribution and porous ratio by BETand BJH methods. The content of Si-OH in SiO_2 surface was calculated by analysis of the results of hydrogen-oxygencontent mensuration (HOCM). As a result, appropriate heat treatment system and ball milling time are important topreparation for nano-SiO_2 with high activity and mesopores, which are 5～50 nm particles, 5～6 nm average aperture,85%～93% porous ratio, and 51%～55% Si-OH content in surface. Nano-SiO_2 with that structure has high surfaceenergy and activity. This process, which has simple facilities and operation rules, is a new way of preparation fornano-SiO_2 with high activity and mesopores.

Creating mesopores in ZSM-48 zeolite by alkali treatment: Enhanced catalyst for hydroisomerization of hexadecane

ZSM-48 zeolites with various Si/Al ratios were hydrothermally synthesized in the H;N（CH;）;NH;（HDA）-containing media. The obtained samples were highly crystallized with minor mixed phases as evidenced by X-ray powder diffraction（XRD）. The alkaline treated ZSM-48 zeolites maintained its structure under different concentrations of Na OH aqueous solution. Micropores remained unchanged while mesopores with wide pore size distribution formed after the alkaline treatment. The surface area increased from 228 to 288 m;/g. The Br?nsted acid sites had little alteration while an obvious increase of Lewis acid sites was observed. The hydroisomerization of hexadecane was performed as the model reaction to test the effects of the alkali treatment. The conversion of hexadecane had almost no change, which was attributed to the preservation of the Br?nsted acid sites. While high selectivity to iso-hexadecane with an improved iso to normal ratio of alkanes was due to the mesopore formation and improved diffusivity.

Optimization of battery life and capacity by setting dense mesopores on the surface of nanosheets used as electrode

Nanosheets with mesopores on the surface have been prepared using molybdenum trioxide(α-MoO3).The effect of mesopores on the performance of the electrode remains elusive.The MoO3 nanosheets obtained in this study exhibited great battery performance, including good capacity, prolonged recycling life cycles, and excellent rate performance;e.g., 780 mAh/g when charged under a super high current-density of 1000 m A/g.These nanosheets demonstrated excellent stability, maintaining a capacity of 1189 mAh/g after 20 cycles, and 1075 mAh/g after 50 cycles;thus preventing the capacity to decrease to values under the scanning rate of 100 mA/g.These high-purity MoO3 nanosheets are well-ordered and have dense mesopores on the surface;these micropores contribute to the excellent electrode performance of the host electrode materials;the performance parameters include prolonged battery life and capacity.Setting mesopores or active sites on the electrode surface can be an alternative way to obtain stable electrodes in the future.

Thick free-standing electrode based on carbon-carbon nitride microspheres with large mesopores for high-energy-density lithium-sulfur batteries

The development of sulfur cathodes with high areal capacity and high energy density is crucial for the practical application of lithium-sulfur batteries(LSBs).LSBs can be built by employing(ultra)high-loading sulfur cathodes,which have rarely been realized due to massive passivation and shuttling.Herein,microspheres of a carbon-carbon nitride composite(C@CN)with large mesopores are fabricated via molecular cooperative assembly.Using the C@CN-based electrodes,the effects of the large mesopores and N-functional groups on the electrochemical behavior of sulfur in LSB cells are thoroughly investigated under ultrahigh sulfur-loading conditions(>15 mgS cm^(-2)).Furthermore,for high-energy-density LSBs,the C@CN powders are pelletized into a thick free-standing electrode(thickness:500^m;diameter:11 mm)via a simple briquette process;here,the total amount of energy stored by the LSB cells is 39 mWh,corresponding to a volumetric energy density of 440 Wh L-1 with an areal capacity of 24.9 and 17.5 mAh cm^(-2) at 0.47 and 4.7 mA cm^(-2),respectively(at 24mgS cm^(-2)).These results have significantly surpassed most recent records due to the synergy among the large mesopores,(poly)sulfide-philic surfaces,and thick electrodes.The developed strategy with its potential for scale-up successfully fills the gap between laboratory-scale cells and practical cells without sacrificing the high areal capacity and high energy density,providing a solid foundation for the development of practical LSBs.

Fluids in Mesopores： A New Theory and Applications

While hysteresis in the adsorption of fluids in porous material is known since about one century, the thermodynamic treatment of this phenomenon is still not settled. We propose to accept that thermodynamics is not designed to deal with confined systems and we propose to introduce a new set of rules for describing the behavior of confined systems. This proposal is based on a large number of simulation calculations. The employed method of simulation has been shown to describe static and dynamic phenomena encountered in this field. The newly formulated theory incorporates the phenomenon of hysteresis without inconsistencies. Further, it will be shown that the theory allows simulating diffusional and convectional transport （nanofluidics） by a unified approach without the need to introduce capillary forces （surface or interface tensions） by phenomenological parameters. The second part of the paper is devoted to the potential for practical use. It turns out that the new concepts open the route to employing unusual states of matter found in porous systems which may lead to improved applications. In particular we will focus on the possibility to drive a fluid in a pore into states with negative pressure under static and under dynamic conditions. It turns out that states with negative pressure can be reproducibly controlled. Negative pressure states are in principal known since the time of Torricelli and they have been discussed in the literature as experimentally accessible situations. Still, they have not been turned into practical usefulness which is likely to be caused by the notion of their metastability in macroscopic systems. Possible applications refer to controlling chemical reactions as well as new routes to efficient separation processes that are difficult to handle by conventional techniques.

Facile One-Pot Synthesis of ZSM-5 Aggregates with Interand Intra-Crystalline Mesopores for Methanol to Gasoline Conversion

ZSM-5 aggregates consisting of superfine and hierarchical nanocrystals(combined with micropores and intra-crystalline mesopores) with an average size of 30 nm were prepared through one-pot synthesis with the assistance of anionic polyacrylamide(APAM). The resultant zeolites(AHN-ZSM-5) were characterized by XRD, ICP-OES, SEM, TEM, BET, NH_3-TPD, Py-IR, and TG analyses and evaluated in the methanol to gasoline(MTG) reaction. Characterization results show that the hierarchical ZSM-5 aggregates possessed two kinds of mesopores, namely inter-and intra-crystalline mesopores. The amount of APAM considerably influenced the mesoporosity and textural properties of AHN-ZSM-5 zeolites. With the addition of APAM in the synthesis, the AHN-ZSM-5 zeolites exhibited large mesopore volume, large external surface area, and appropriate acidity. When applied in the MTG reaction, AHN-ZSM-5 demonstrated a catalytic lifetime that was 1.6 times longer than that of conventional ZSM-5 synthesized in the absence of APAM.

Size Determination of Ultramicropores and Small Mesopores Using a Calculation Procedure Based on the Tangents of Comparison Plot

Pore size distribution（PSD） curves of synthesized hollow silica spheres with ultrmicropores and small mesopores were obtained from calculations based on the BJH,KJS,SF,MP,NLDFT models and Prof.Zhu＇s method.Comparisons indicate that Zhu＇s method not only gives reasonable small mesopore size but also could be further extended to the ultramicropores region for the PSD evaluation.

On a New Mechanism for Separating two Components in a Stationary Flow through Mesopores

When simulating the behavior of fluids in a stationary flow through mesopores we have observed a phenomenon that may prove useful in some cases as basis for separating fluid components. The scheme works at constant temperature which makes it energy efficient as are other schemes like (molecular) sieves or chromatography. Sieves rely on differences in molecular size and chromatography on different affinity of components to the solid material of the ‘packing’. The scheme presented here may sometimes complement the established techniques in that it is based on a different mechanism. The fluids to be separated can have the same molecular size and the same affinity to solid material they are in contact with. The only requirement for the scheme to work is that the miscibility behavior varies somewhat with pressure or density. From literature it is known that virtually any mixture reacts on strong variations of pressure. Even a mixture that behaves almost ideally at ambient pressure will show slight deviations from ideal miscibility when exposed to extreme pressure. The strong differences in pressure are not created by external means but by exploiting the spontaneous behavior of fluids in mesopores. If the experiment is designed correctly, strong pressure gradients show up in mesopores that are far beyond any gradient that could be established by technical means. Our simulations are carried out for situations where pressure inside the pores varies between a few hundred bar positive pressure and a few hundred bar negative pressure while the pressure in the gas phase outside the pores amounts to ca.170 mbar.

Progress in understanding fluids in mesopores

An important feature of porous materials is the adsorption hysteresis: the amount of an atomic or molecular species adsorbed from the gas phase is not only dependent on the gas pressure, but may depend in certain ranges of pressure on the history. Thus, the system may respond in different ways to identical experimental conditions which seems to contradict classical thermody-namics. While the phenomenon is known since about a century, it has not yet found a consistent theoretical description. In the pres-ent talk, we will-based on results of computer simulations-formulate rules that provide a consistent basis for the behavior of confined systems, or even for inhomogeneous systems in general. In other words, we present a new theory (confined thermodynamics) with its own definitions and rules. It will turn out, that hysteretic behavior does not impose a conceptual challenge any more, but follows in a natural way from these rules. The approach which is employed in the simulations is very akin to the density functional method. All quantities defined develop into the standard thermodynamic expressions when the density of amount becomes homogeneous.The second part of the talk is devoted to the potential for practical use. It turns out that the new theory does not only remove conceptual problems, but at the same time opens the route to a number of new states found in porous systems which may lead to im-proved applications. In particular we will focus on the possibility to drive a fluid in a pore into exotic states with negative pressure, provided one has full control over the phenomenon of adsorption hysteresis. Negative pressure states are in principal known since the time of Torricelli and they have been in the literature as experimentally accessible situations. Still, they have not been turned into practical usefulness which is likely to be caused by the notion of their metastability in macroscopic systems. However, fluids con-fined to nanopores have been proven to show reproducible behaviour. The present time appears to be suited for exploring the new ap-plications resting in fluid/pore systems: since about a decade material scientists have started to prepare pores with increasing accura-cy from an increasing variety of substances. On the other hand, the new theory presented in the first part of the talk provides the tool to drive a fluid/pore system reliably into any of the exotic states found within a hysteresis loop. Prospects of a few applications will be discussed.

Hollow Bio-derived Polymer Nanospheres with Ordered Mesopores for Sodium-Ion Battery

Bio-inspired hierarchical self-assembly provides elegant and powerful bottom-up strategies for the creation of complex materials.However,the current self-assembly approaches for natural bio-compounds often result in materials with limited diversity and complexity in architecture as well as microstructure.Here,we develop a novel coordination polymerization-driven hierarchical assembly of micelle strategy,using phytic acid-based natural compounds as an example,for the spatially controlled fabrication of metal coordination bio-derived polymers.The resultant ferric phytate polymer nanospheres feature hollow architecture,ordered meso-channels of^12 nm,high surface area of 401 m2 g−1,and large pore volume of 0.53 cm3 g−1.As an advanced anode material,this bio-derivative polymer delivers a remarkable reversible capacity of 540 mAh g−1 at 50 mA g−1,good rate capability,and cycling stability for sodium-ion batteries.This study holds great potential of the design of new complex bio-materials with supramolecular chemistry.

Simultaneous Removal of Surfactant Template from MCM-41 and Implantation of Transition Metal Complexes into Mesopores with Supercritical Fluid

The simultaneous removal of up to 92% of the surfactant template and chemical implantation of transition metal complexes into mesopores has been successfully achieved by treating as-synthesized pure siliceous MCM-41 with supercritical CO2 modified with CH2Cl2/MeOH mixture, resulting in the formation of functionalized material with uniform pore structure.

Double-Mesopore V-MSU-X Silica and its Pure Siliceous Derivative Prepared by One Synthesis System

Non-ionically templated organo-modified MSU-2 mesoporous silicas have been prepared in neutral medium by co-condensation TEOS and vinyltriexoylsiloxane (VTES) and exhibit highly symmetric bimodal mesopore systems. A bromination reaction of V-MSU-2 provides evidence for attachment of most vinyl groups to the accessible surface within the channels. Further, siliceous MSU-2 materials with double pore size have been obtained from calcination of so-produced organo-modified MSU-2 and demonstrate the immense flexibility of the non-ionic templating system.

Interfacial assembly of 2D polydopamine/graphene heterostructures with well-defined mesopore and tunable thickness for high-energy planar micro-supercapacitors

Two-dimensional(2D)mesoporous pseudocapacitive polymer/graphene heterostructures combine the advanced merits of 2D materials and mesoporous materials,possessing unique nanosheet structure,large specific surface area(SSA),abundant oxygen/nitrogen-containing groups,desirable electrical conductivity and admirable electrochemical redox activity,and hold great potential for constructing high-performance planar micro-supercapacitors(MSCs).Herein,we demonstrate the interfacial assembly of 2D mesoporous polydopamine/graphene(mPDG)heterostructures with well-defined mesopore structure(12 nm)and adjustable thickness(7.5–14.1 nm)for planar high-energy pseudocapacitive MSCs.Attributed to medium thickness,exposed mesopore of 12 nm and large SSA of 108 m^(2)/g,the m PDG with 10.8 nm thickness reveals prominent mass capacitance of 419 F/g and impressive cycling stability with~96%capacitance retention after 5000 cycles.Furthermore,the symmetric mPDG-based MSCs with“water-in-salt”gel electrolyte present wide voltage window of 1.6 V,superior volumetric energy density of 11.5 mWh/cm^(3),outstanding flexibility and self-integration ability.Therefore,this work offers a new platform of controllably synthesizing 2D mesoporous heterostructures for high-performance MSCs.

Enhanced activation of peroxymonosulfate by Fe/N co-doped ordered mesoporous carbon with dual active sites for efficient removal of m-cresol

The novel Fe-N co-doped ordered mesoporous carbon with high catalytic activity in m-cresol removal was prepared by urea-assisted impregnation and simple pyrolysis method.During the preparation of the Fe-NC catalyst,the complexation of N elements in urea could anchor Fe,and the formation of C3N4during urea pyrolysis could also prevent migration and aggregation of Fe species,which jointly improve the dispersion and stability of Fe.The FeN4sites and highly dispersed Fe nanoparticles synergistically trigger the dual-site peroxymonosulfate (PMS) activation for highly efficient m-cresol degradation,while the ordered mesoporous structure of the catalyst could improve the mass transfer rate of the catalytic process,which together promote catalytic degradation of m-cresol by PMS activation.Reactive oxygen species (ROS) analytic experiments demonstrate that the system degrades m-cresol by free radical pathway mainly based on SO_(4)^(-)·and·OH,and partially based on·OH as the active components,and a possible PMS activation mechanism by 5Fe-50 for m-cresol degradation was proposed.This study can provide theoretical guidance for the preparation of efficient and stable catalysts for the degradation of organic pollutants by activated PMS.

Stable immobilization of lithium polysulfides using three-dimensional ordered mesoporous Mn_(2)O_(3) as the host material in lithium-sulfur batteries

Lithium-sulfur batteries(LSBs)have drawn significant attention owing to their high theoretical discharge capacity and energy density.However,the dissolution of long-chain polysulfides into the electrolyte during the charge and discharge process(“shuttle effect”)results in fast capacity fading and inferior electrochemical performance.In this study,Mn_(2)O_(3)with an ordered mesoporous structure(OM-Mn_(2)O_(3))was designed as a cathode host for LSBs via KIT-6 hard templating,to effectively inhibit the polysulfide shuttle effect.OM-Mn_(2)O_(3)offers numerous pores to confine sulfur and tightly anchor the dissolved polysulfides through the combined effects of strong polar-polar interactions,polysulfides,and sulfur chain catenation.The OM-Mn_(2)O_(3)/S composite electrode delivered a discharge capacity of 561 mAh g^(-1) after 250 cycles at 0.5 C owing to the excellent performance of OM-Mn_(2)O_(3).Furthermore,it retained a discharge capacity of 628mA h g^(-1) even at a rate of 2 C,which was significantly higher than that of a pristine sulfur electrode(206mA h g^(-1)).These findings provide a prospective strategy for designing cathode materials for high-performance LSBs.

Hollow Fe3O4/carbon with surface mesopores derived from MOFs for enhanced lithium storage performance

Hollow metal-organic frameworks(MOFs)and their derivatives have attracted more and more attention due to their high specific surface area and perfect morphological structure,which determine their large potential application in energy storage and catalysis fields.However,few researchers have carried out further modification on the outer shell of hollow MOFs,such as the perforation modification,which will endow hollow nanomaterials derived from MOFs with multifunctionality.In this paper,hollow MOFs of MIL-53(Fe)with perforated outer surface are successfully synthesized by using SiO2 nanospheres as the template via a self-assembly process induced by the coordination polymerization.The tightly packed mesopore structure makes the carbon outer shell of MOFs thinner,thus realizing the in-situ transformation from MOFs to hollow Fe3 O4/carbon,which exhibits perfect capacity approaching 1270 mA h g-1 even after 200 cycles at 0.1 A g-1,as an anode material in lithium ion batteries(LIBs)application.This research provides a new strategy for the design and preparation of MOFs and their derivatives with multifunctionality for the energy applications.

Effect of mesopores on solidification of sirolimus self-microemulsifying drug delivery system

To investigate the influence of mesopores towards the solidification of self-microemulsifying drug delivery system(SMEDDS), mesoporous silica nanospheres(MSNs) and Santa Barbara Amorphous-15(SBA-15) were compared. The MSNs had hydrodynamic size of 195.35 ± 5.82 nm, and pore diameter of 2.70 nm. The SBA-15 had hydrodynamic size of 2312.19 ± 106.93 nm, and pore diameter of 10.91 nm. The MSNs and SBA-15 showed similar loading efficiency of SMEDDS containing sirolimus(SRL). However,MSNs had higher drug dissolution and in vivo absorption, with relative bioavailability of 174.62%. Thus,the length of mesopores played a more important role in solidification of SMEDDS as compared with the pore diameter. This study suggests that the SMEDDS-MSNs can be a potential candidate for oral administration of hydrophobic drugs.

Osteoblast behaviors on titania nanotube and mesopore layers

Titania nanotubes and mesopores with different diameter sizes were prepared by electrochemical oxidation of titanium.The responses of osteoblastic cells isolated from Sprague–Dawley rats to the nanotube and mesopore layers were investigated in sequential events of cell adhesion,morphology,actin cytoskeleton,proliferation,differentiation,and mineralization.Nano-structural features,especially diameters of the nanotubes and mesopores,obviously influenced on cell behaviors in the sequential events.The cells showed better proliferation and differentiation abilities on the specimens with the nanotubes and mesopores than on flat titanium disk.Higher levers of calcium mineralization were observed on the nanotube and mesopore layers.The cells adhered much faster onto the nanotubes with about 170nm diameter and the mesopores with about 400nm diameter than onto flat titanium disk and 50nm nanotubes.There is an appropriate range of the tube/pore sizes,and in this present work,titania nantubes with 170nm diameter is the best for enhancing functions of osteoblasts.