Pore-structure-mediated hierarchical SAPO-34: Facile synthesis,tunable nanostructure,and catalysis applications for the conversion of dimethyl ether into olefins

Hierarchical cross-like SAPO-34 catalysts with different pore size distributions were obtained via hydrothermal synthesis with polyethylene glycol (PEG) as the mesopore-generating agent. The hierarchical SAPO-34 molecular sieves were characterized using X-ray diffraction, scanning electron microscopy, N₂ adsorption–desorption, thermogravimetric analysis, and temperature-programmed NH₃ desorption. The cross-like SAPO-34 catalysts exhibited enriched multi-porosity, and the sizes of their mesopores ranged from 10 to 50 nm. Both the mesoporous structures and morphologies of the hierarchical SAPO-34 could be further tuned through adjustments of the amount of PEG used. The as-obtained SAPO-34 showed dramatic catalytic performance in the conversion of dimethyl ether into olefins. A maximum selectivity of olefins of 96% was achieved, which was attributed to the rapid transport of the reactants and products in zeolitic micropores through mesopores.     

High-temperature synthesis of SAPO-34 molecular sieve using a dry gel method

SAPO-34 is one of the main catalysts used in the petrochemical industry. Various effective methods have been developed to synthesize SAPO-34 with optimal size and characteristics for such application. In the present study, SAPO-34 was synthesized using a dry gel method at high temperatures. Morpholine was used as an organic template. The products were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and gas sorption analysis. The results showed that application of the dry gel method at high temperatures successfully afforded a pure catalyst with high crystallinity. Small particles of less than 500 nm could be obtained within a short reaction time of 30 min.     

Water-bathing synthesis of high-surface-area zeolite P from diatomite

Zeolite P was synthesized for the first time via a novel water-bathing route at 90 C using scrubbed diatomite,sodium hydroxide,and aluminum hydroxide as precursor,with SiO 2/Al 2 O 3,SiO 2/Na 2 O,and H 2 O/Na 2 O molar ratios of 7.43,3.81,and 80.00,respectively.The as-fabricated samples were characterized by means of scanning electron microscopy,X-ray diffraction,and nitrogen adsorption measurements.This study showed that (i) treating the diatomite raw material with sodium hexametaphosphate could open the p...     

Application of solvent evaporation technique for pure drug crystal spheres preparation

An innovative application of the solvent evaporation technique was suggested. Solvent evaporation technique is a technique for drug encapsulation and nanosphere preparation. The widely used technique is also facing the problem of low actual drug entrapment percent, which is not economic from the industrial view. The goal of this work is trying to use the advantage of this technique concerning the product sphericity and the ability to control particle size, to prepare a drug as pure crystals spheres. Ibuprofen is selected as a model drug. The spheres are formed by using Polyvinyl pyrrolidone (PVP) or Polyethylene glycol (PEG) as an anti-aggregating agent but not formed on using tween or span. Particle size and actual drug content depend on the concentrations the anti-aggregating agent used. Surfaces of the drug crystal spheres are porous with empty sphere internal structure on using PVP but spongy and rough on using PEG. The drug has its identity chemical form in the drug crystal spheres. IR scan of spheres prepared on using PEG showed a characteristic ether peak. DSC showed melting endothermic peak of PEG, but X-ray showed minor change in the drug crystal patterns. Drug release profiles from crystal spheres prepared with the same anti-aggregating agent are close to each other. The drug release profiles from drug crystal spheres prepared by using PEG are more controlled than that prepared by using PVP. The drug release mechanism is diffusion. It was concluded that, the same technique could be suggested for preparation of other biomedical material in pure crystals spheres with controlled particle size. These properties may encourage to prepare very small particles with spherical shape for inhalation or injection as an innovative particle technology application for the widely used technique.     

Diffusive Effects on Recovery of Light Oil by Medium Temperature Oxidation

Volatile oil recovery by means of air injection is studied as a method to improve recovery from low permeable reservoirs. We consider the case in which the oil is directly combusted into small products, for which we use the term medium temperature oil combustion. The two-phase model considers evaporation, condensation and reaction with oxygen. In the absence of thermal, molecular and capillary diffusion, the relevant transport equations can be solved analytically. The solution consists of three waves, i.e., a thermal wave, a medium temperature oxidation (MTO) wave and a saturation wave separated by constant state regions. A striking feature is that evaporation occurs upstream of the combustion reaction in the MTO wave. The purpose of this paper is to show the effect of diffusion mechanisms on the MTO process. We used a finite element package (COMSOL) to obtain a numerical solution; the package uses fifth-order Lagrangian base functions, combined with a central difference scheme. This makes it possible to model situations at realistic diffusion coefficients. The qualitative behavior of the numerical solution is similar to the analytical solution. Molecular diffusion lowers the temperature of the MTO wave, but creates a small peak near the vaporization region. The effect of thermal diffusion smoothes the thermal wave and widens the MTO region. Capillary diffusion increases the temperature in the upstream part of the MTO region and decreases the efficiency of oil recovery. At increasing capillary diffusion the recovery by gas displacement gradually becomes higher, leaving less oil to be recovered by combustion. Consequently, the analytical solution with no diffusion and numerical solutions at a high capillary diffusion coefficient become different. Therefore high numerical diffusion, significant in numerical simulations especially in coarse gridded simulations, may conceal the importance of combustion in recovering oil.     

SYNTHESIS AND COATING OF ORDERED MESOPOROUS SILICA

1,3,5-trimethyl benzene (TMB) was used as organic swelling agent in O/W emulsions to template ultra-large mesoporous materials using the hydrothermal method. The silicas with well-defined mesopores and hydrothermally robust framework were characterized by X-ray diffraction, transmission electron microscopy and BET surface area analysis. The influence of the quantity of TMB during preparation was studied. It has been found that the TMB/CTAB ratio must be controlled for producing high pore volume materials. Polysulfone (PSU), as the usual extraction agent, was coated on the silicas with the solvent evaporation method to produce a solid separation medium. The adsorptivity and the surface area of the coated MCM were determined: 10% PSU coated MCM adsorbed twice as much phenol as the uncoated material, reaching 0.5 mg/g silica. It was found that the surface area of the coated material decreased rapidly with an increase of the PSU Ioadina.     

Self-assembly of fibrous ZSM-5 zeolites in the presence of sodium alginate

ZSM-5 zeolites with a fibrous morphology were successfully self-assembled in the presence of sodium alginate. The effect of the sodium alginate concentration, Si/Al molar ratio in the synthesis gel, crystallization temperature and time, and the addition order of the sodium alginate on the morphology of the ZSM-5 zeolites was investigated. The possible formation mechanism of fibrous ZSM-5 zeolite crystals was also proposed. The results indicated that the carboxyl and hydroxyl groups of sodium alginate synergistically induced the self-stacking of ZSM-5 nanocrystals and thus the formation of the fibrous ZSM-5 zeolites. The Si/Al molar ratio of the fibrous ZSM-5 zeolites could be adjusted by controlling the amount of the NaAlO₂ additive; however, high Si/Al molar ratios also hindered the self-stacking of ZSM-5 nanocrystals. A high crystallization temperature (180 °C), a moderate sodium alginate concentration (8.33 g/L), and the addition of sodium alginate prior to tetraethoxysilane were necessary for the formation of fibrous ZSM-5 zeolites.     

Preparation of 3D micro/nanostructured CeO2: Influence of organic/inorganic acids

CeO₂ is an important porous material with a wide range of applications in the abatement of volatile organic compounds (VOCs). In this paper, we prepared a series of novel three-dimensional (3D) micro/nanostructured CeO₂ materials via a solvothermal method. Organic acid-assisted synthesis and inorganic acid post-treatment were used to adjust the CeO₂ microstructures. The size of the 3D micro/nanostructures could be controlled in the range from 180 nm to 1.5 μm and the surface morphology changed from rough to smooth with the use of different organic acids. The CeO₂ synthesized with acetic acid featured a hierarchical porosity and showed good performance for toluene catalytic combustion: a T₅₀ of 187 °C and a T₉₀ of 195 °C. Moreover, the crystallite size, textural properties, and surface chemical states could be tuned by inorganic acid modification. After treatment with HNO₃, the modified CeO₂ materials exhibited improved catalytic activity, with a T₅₀ of ∼175 °C and a T₉₀ of ∼187 °C. We concluded that the toluene combustion activity is related to the porosity and the amount of surface active oxygen of the CeO₂. Both these features can be tuned by the co-work of organic and inorganic acids.     

Apoferritin nanoparticle based dual-antigen influenza conjugate vaccine with potential cross-protective efficacy against heterosubtypic influenza virus

Ferritin nanoparticles with self-assembling properties have been widely explored as vaccine carrier by displaying foreign antigens through genetic fusion strategy. In the present work, an apoferritin (AFt) nanoparticle was tested as influenza vaccine carrier by chemically conjugating a matrix protein 2 ectodomain (M2e) antigen peptide or/and the full-length hemagglutinin (HA) antigen on the outer surface of the AFt, with heterobifunctional sSMCC or SM(PEG)24 containing PEG chain as linkers. To each AFt nanoparticle, about 30–32 M2e or 1.8 HA antigen could be coupled. The AFt-(PEG)₂₄-M2e, in which the M2e was coupled through SM(PEG)24 containing PEG chain, conferred higher protective efficacy in immunized mice than AFt-M2e did, but was less effective than AFt-(PEG)₂₄-HA. When both M2e and HA were coupled, the synthesized dual-antigen vaccine candidate AFt-(PEG)₂₄-M2e/HA elicited high level of M2e and HA antigen-specific antibodies and conferred 100% protection against lethal infection of homologous PR8 H1N1 virus strain and 70% protection against a heterologous A/FM/1/47 (FM1, H1N1) strain, which was more effective than the M2e or HA single antigen vaccine candidates. The potential cross-protective effect of the dual-antigen vaccine was further demonstrated by significant specific hemagglutination inhibition (HAI) titers in serum of the immunized mice against three other heterologous viral strains including A/Singapore/GP1908/2015 (IVR-180) H1N1, A/Anhui/1/2005 H5N1, and A/Hong Kong H3N2.     

Control of iron nanoparticle size by manipulating PEG–ethanol colloidal solutions and spin-coating parameters for the growth of single-walled carbon nanotubes

Iron catalyst nanoparticles were prepared on silicon wafers by spin-coating colloidal solutions containing iron nitrate, polyethylene glycol (PEG) and absolute ethanol. The effects of various spin-coating conditions were investigated. The findings showed that the size of the iron particles was governed by the composition of the colloidal solution used and that a high angular speed was responsible for the formation of a thin colloidal film. The effect of angular acceleration on the size and distribution of the iron particles were found to be insignificant. It was observed that a longer spin-coating duration provoked the agglomeration of iron particles, leading to the formation of large particles. We also showed that single-walled carbon nanotubes could be grown from the smallest iron catalyst nanoparticles after the chemical vapor deposition of methane.     

Synthesis and characterization of PMMA/Al2O3 composite particles by in situ emulsion polymerization

In order to improve its dispersibility, superfine alumina (Al2O3) was encapsulated with poly (methyl methacrylate) (PMMA) by in situ emulsion polymerization. It was found that only when the concentration of sodium dodecyl sulfate (SDS) was much higher than its critical micelle concentration, could PMMA/Al2O3 composite particles with high percentage of grafting (PG) be prepared. The same results were obtained between the experimental and stoichiometric amounts of tris (dodecylbenzenesulfonate) isopropoxide (NDZ), indicating that single-molecule-layer adsorption had taken place between NDZ and Al2O3. Analysis using FTIR. TEM and XPS showed that PMMA/Al2O3 composite particles with core-shell structure had been successfully synthesized by in sire emulsion polymerization. Compared to Al2O3, thermal stability and dispersibility of the composite particles showed marked improvement.     

Density functional theory study on the influence of cation ratio on the host layer structure of Zn/Al double hydroxides

A density functional theory (DFT) study has been carried out for [Znn-1Al(OH2)n+6(OH)2n-2]3+(n=3-6) and [Znn-1 Al(OH2)2n-2(OH)2n-2 ]3+ (n=7) clusters,which include the basic structural information of the brucite-like lattice structure of Zn/Al layered double hydroxides (LDHs) with Zn/Al molar ratio (R) in the range 2-6,in order to understand the effect of the Zn/Al ratio on the structure and stability of binary Zn/Al LDHs.Based on systematic calculations of the geometric parameters and formation energies of the cluster models,it was found that it is possible for Zn2+ and Al3+ cations to replace Mg2+ isomorphously in the brucite-like structure with different R values,resulting in differences in microstructure of the clusters and unit cell parameter a of the Zn/Al LDHs.Analysis of the geometry and bonding around the trivalent Al3+ or divalent Zn2+ cations reveals that Al3+ plays a more significant role than Zn2+ in determining the microstructure properties,formation and bonding stability of the corresponding ZnRAl clusters when R＜5,while the influence of Zn2+ becomes the dominant factor in the case of R≥5.These findings are in good agreement with experiments.This work provides a detailed electronic-level understanding of how the composition of cations affects the microstructure and stability of Zn-containing binary LDH layers.     

Secondary reduction strategy synthesis of Pt–Co nanoparticle catalysts towards boosting the activity of proton exchange membrane fuel cells

Based on the volcanic relationship between catalytic activity and key adsorption energies, Pt–Co alloy materials have been widely studied as cathode oxygen reduction reaction (ORR) catalysts in proton exchange membrane fuel cells (PEMFCs) due to their higher active surface area and adjustable D-band energy levels compared to Pt/C. However, how to balance the alloying degree and ORR performance of Pt–Co catalyst remains a great challenge. Herein, we first synthesized a well-dispersed Pt/Co/C precursor by using a mild dimethylamine borane (DMAB) as the reducing agent. The precursor was calcined at high temperature under H₂/Ar mixed gas by a secondary reduction strategy to obtain an ordered Pt₃Co intermetallic compound nanoparticle catalyst with a high degree of alloying. The optimization of electronic structure due to Pt–Co alloying and the strong metal-carrier interaction ensure the high kinetic activity of the cell membrane electrode. Additionally, the high degree of graphitization increases the electrical conductivity during the reaction. As a result, the activity and stability of the catalyst were significantly improved, with a half-wave potential as high as 0.87 V, which decreased by only 20 mV after 10000 potential cycles. Single-cell tests further validate the high intrinsic activity of the ordered Pt₃Co catalyst with mass activity up to 0.67 A mg_pt⁻¹, exceeding the United States Department of Energy (US DOE) standard (0.44 A mg_pt⁻¹), and a rated power of 5.93 W mg_pt⁻¹.     

Improved performance of aluminum pigments encapsulated in hybrid inorganic–organic films

An organic silane acrylate resin (PMBK) was synthesized by free-radical solution polymerization using methyl methacrylate, butyl acrylate and (3-methacryloxypropyl)trimethoxysilane as monomers. Aluminum (Al) particles were then encapsulated in inorganic–organic hybrid films that were prepared by hydrolysis and condensation of PMBK and tetraethyl orthosilicate (TEOS) on the surface of Al pigments. Characterization results showed that PMBK and TEOS could simultaneously hydrolyze and condense with hydroxyl groups on the surface of the Al particles to form composite Al particles coated with inorganic–organic hybrid films. Compared with raw Al particles, the corrosion resistance and adhesive properties of paint films containing the composite Al particles were improved greatly, while the glossiness of the paint films decreased slightly, from 48.6° to 47.0°. In alkaline media (pH 11), the volume of evolved H₂ of composite Al particles was only 3.5 mL, whereas that of raw Al was 83.5 mL. The glossiness of paint films containing composite Al particles decreased by 1.66% after immersion in alkaline media for 24 h, whereas that of raw Al decreased by 14.82%. Peel-off tests of the paint films showed that the composite particles moved slightly away from the paint films. In contrast, the raw Al particles were seriously desquamated, suggesting encapsulation of hybrid films can greatly improve the adhesive properties of Al particles in paint films.     

Synthesis of mesoporous tin dioxide via sol-gel process assisted by resorcinol–formaldehyde gel

Tin dioxide is a useful n-type oxide semiconductor used in a variety of applications owing to its superior optical, electrical, and multifunctional properties. Here, we used a network of resorcinol–formaldehyde (RF) gel to synthesize mesoporous tin dioxide via a sol–gel process. The effects of various synthesis parameters on the morphology and mesoporosity of the obtained product were investigated, including aging time of the RF gel, tin-to-formaldehyde molar ratio, resorcinol-to-carbonate molar ratio, and the aging time of the tin/RF mixed gel. Our experimental results showed that the interaction between the network of the RF gel and tin-containing sol is a key factor that affected the structural strength of the porous network and the porosity of the final product. Through control of the interactions in the tin/RF mixed gel we obtained porous tin dioxide materials that could be effectively used to form large-surface area films with desirable mesoporous properties.     

Further investigations on the influence of scale-up of a high shear granulator on the granule properties

This study focuses on the characterisation of strength, density, and size of granules produced in various scales of a high shear granulator. Calcium carbonate （Durca165） was used as the feed powder and aqueous polyethylene glycol （PEG 4000） as the binder. The dried granules were analysed for their strength, density, size distribution, and wall make-up. Granules were produced in granulators with four scales, 1, 5, 50, and 250 L under three scale-up rules of constant tip speed, constant shear stress, and constant Froude number. The results show that regardless of equipment scale, increasing the impeller speed has a great effect on crushing strength and stress. The underlying cause is an increase in granule density due to more consolidation at higher impeller speeds. Wall make-up is significantly reduced to less than 5% as the scale is increased from 1 to 250 L. The results of this study corroborate our previous findings that the constant tip speed rule is the best criterion for scale-up of high shear granulators.     

磷酸酯离子液体对钢/铝摩擦副的摩擦性能研究

为解决钢/铝摩擦副润滑困难的现状,合成了1种磷酸酯类离子液体.采用SRV微动摩擦磨损试验机对其在钢/铝摩擦副条件下的摩擦学行为进行了测试;采用扫描电子显微镜（SEM）及X光电子能谱（XPS）对磨损表面进行了分析.结果表明：此磷酸酯离子液体对钢/铝摩擦副具有优良的减摩抗磨性能,优于常见的含氟类离子液体（LB106和LP106）及液体石蜡.SEM和XPS分析结果表明：磷酸酯离子液体在摩擦过程中于金属表面形成了包含有机金属配合物,磷酸铝盐的复合边界润滑膜,从而使其表现出优异的摩擦学性能.     

热挤压态Al—Si—Pb轴承合金的摩擦学行为

研究了热挤压对搅拌铸造 Al- Si- Pb合金组织与机械性能的影响 .结果表明 :热挤压可以显著改善合金铸态组织 ,降低气孔率 ,提高机械性能 ;随着铅含量增加 ,合金的摩擦系数与磨损率显著下降 ,尤其铅含量为 2 0 %与 2 5 %的合金抗咬合性能明显提高 .对其磨损表面的光学与 X射线光电子能谱分析表明 ,磨损表面了形成由 Al2 O3、Fe2 O3和 Pb的化合物组成的混合物润滑膜 ,这是其抗咬合性能得以改善的直接原因 .     

喷射成形Zn52Al40Cu2Si6微观形貌及耐磨性能

采用喷射成形工艺制备高铝锌基合金,利用扫描电镜?金相显微镜?透射电镜及X-射线衍射等表征了合金的磨损形貌和内部组织,采用M2000摩擦试验机考察了高铝锌基合金的摩擦磨损性能.结果表明,沉积坯大部分为粗化均细的共析片层状组织,呈不均匀微观分布态,而不是通常认为的树枝晶结构.沉积过程中形成较多无规则?不均匀分布的孔洞,致密度只有60%左右;由于时效后期的四相反应α+ε→Τ′+η,合金的硬度热处理后下降.试验中,硅颗粒在合金基体中始终呈均匀分布.通过M2000摩擦试验机测试合金的摩擦磨损性能.Zn52Al40Cu2Si6合金在2000N载荷,200r/min试验条件下呈最佳耐磨性能.合金的摩擦系数随着载荷的增加而减小.