Mesopore Porosity Research Articles

Targeted Anthocyanin Enrichment of Cranberry Juice by Electrodialysis with Filtration Membranes: Impact of Filtration Membrane Physicochemical Properties and Predictive Statistical Models.

To optimize cranberry juice enrichment, correlation between physicochemical properties of filtration membranes (FM) and anthocyanin migration was investigated during electrodialysis with filtration membranes (EDFM) using redundancy (RDA) and multivariate regression (MRGA) analyses. Six polyether sulfone (PES) and polyvinylidene fluoride (PVDF) membranes with molecular weight cut-offs between 150 and 500 kDa, commercially available at large scale, were characterized in terms of nine physicochemical characteristics and used for EDFM. The highest migration of total anthocyanin was obtained with PVDF 250 kDa, with a global migration rate of 3.5 ± 0.4 g/m2·h. RDA showed that two FM properties (mesopore porosity and hydrophilic porosity) were significantly negatively correlated to the anthocyanin's migration and explained 67.4% of their total variation in migration. Predictive MRGA models were also developed for each anthocyanin based on these significant FM properties. A combination of intermolecular interactions may lead to binding in a cooperative and synergistic mode and hinder the anthocyanin migration.

Devitrite (Na2Ca3Si6O16) phase dominated nanostructured 45S5 bioactive glass: exploring its structural and biological properties

This research study is primarily centred around calcination temperature and time influence on phase formation in bioactive glasses (BGs). In the present study, BG with a nominal composition of 45S5 was synthesized through the sol–gel process. The developed BGs then underwent heat treatment for various sintering durations and temperatures. X-ray diffraction (XRD) patterns of the BGs reveals that the sintering process led to the crystallization of both devitrite (Na2Ca3Si6O16) and combeite (Na2Ca2Si3O9) phases. The field emission scanning electron microscopy study divulges morphological alterations, from sheet-like to rod-like structures to eventually transforming into spherical and sheet-like structures. The surface area and Type-IV mesoporous porosity were validated through Brunauer Emmett Teller analysis, highlighting a notable increase in pore volume and mechanical strength at a lower sintering temperature. In vitro apatite formation was carried out in Hank’s balance salt in order to evaluate the bioactivity of the glass. After 7 d of immersion in simulated body fluid (SBF), XRD patterns and scanning electron microscopy micrographs results showed that formation of hydroxyapatite layer on the surface of the BGs. The BG compatibility with erythrocytes (red blood cells) was also studied, and the results revealed that there was only a low 2% lysis, showing good hemocompatibility. The drug loading and release behaviour of the BGs was studied in the in vitro analysis. The findings showed a high drug encapsulation effectiveness of up to 90% and continuous drug release from the BGs for 24 h. The materials biocompatibility was unambiguously confirmed by cytocompatibility and proliferation studies. This study provides compelling evidence for the exceptional efficacy and promise of the distinct 45S5 BGs in advancing the field of regenerative medicine.

Adsorption Behavior and Kinetics of 1,4-Dioxane by Carbon Aerogel.

1,4-dioxane is a potential carcinogen in water and is difficult to deal with due to its robust cycloether bond and complete miscibility with water. To remove 1,4-dioxane in an economically viable and environmentally friendly way, a series of carbon aerogels were synthesized as adsorbents for 1,4-dioxane. The experiment results showed that adsorption performances were closely related to the preparation conditions of carbon aerogels, such as the molar ratio, heating rate, pyrolysis temperature and residence time, which were carefully controlled. Scanning electron microscope analysis revealed the presence of a three-dimensional porous network structure in carbon aerogels. Brunauer-Emmett-Teller analysis results demonstrated an increase in specific surface area (673.89 m2/g) and total pore volume after carbonization, with an increase in mesoporous porosity and a decrease in microporosity. When considering each variable individually, the highest specific surface area of prepared carbon aerogels was achieved at a pyrolysis temperature of 800 °C, a holding time of 1 h, and a heating rate of 2 °C/min. Under optimal experimental conditions, the adsorption removal of 1,4-dioxane by carbon aerogels exceeded 95%, following quasi-second-order kinetics and Langmuir isothermal adsorption isotherms, indicating that monolayer adsorption on the surface of carbon aerogels occurred. The maximum adsorption capacity obtained was 67.28 mg/g at a temperature of 318 K, which was attributed to the presence of a large proportion of mesopores and abundant micropores simultaneously in carbon aerogels. Furthermore, with the interference of chlorinated solvents such as trichloroethylene (TCE), the removal efficiency of 1,4-dioxane had no obvious inhibition effect. Regeneration experiments showed that after five continuous cycles, the carbon aerogels still kept a comparable adsorption capacity, which illustrates its potential application in 1,4-dioxane-polluted water purification.

Boost the Utilization of Dense FeN4 Sites for High‐Performance Proton Exchange Membrane Fuel Cells

Iron‐nitrogen‐carbon (Fe‐N‐C) catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) have seriously been hindered by their poor ORR performance of Fe‐N‐C due to the low active site density (SD) and site utilization. Herein, we reported a melamine‐assisted vapor deposition approach to overcome these hindrances. The melamine not only compensates for the loss of nitrogen caused by high‐temperature pyrolysis but also effectively etches the carbon substrate, increasing the external surface area and mesoporous porosity of the carbon substrate. These can provide more useful area for subsequent vapor deposition on active sites. The prepared 0.20Mela‐FeNC catalyst shows a fourfold higher SD value and site utilization than the FeNC without the treatment of melamine. As a result, 0.20Mela‐FeNC catalyst exhibits a high ORR activity with a half‐wave potential (E1/2) of 0.861 V and 12‐fold higher ORR mass activity than the FeNC in acidic media. As the cathode in a H2‐O2 PEMFCs, 0.20Mela‐FeNC catalyst demonstrates a high peak power density of 1.30 W cm−2, outstripping most of the reported Fe‐N‐C catalysts. The developed melamine‐assisted vapor deposition approach for boosting the SD and utilization of Fe‐N‐C catalysts offers a new insight into high‐performance ORR electrocatalysts.

TiO2-embedded mesoporous silica with lower porosity is beneficial to adsorb the pollutants and retard UV filter absorption: A possible application for outdoor skin protection

The purpose of the current investigation was to develop multifunctional TiO2-embedded mesoporous silica incorporating avobenzone to protect against environmental stress through pollutant adsorption and UVA protection. We sought to explore the effect of the mesoporous porosity on the capability of contaminant capture and the suppression of avobenzone skin penetration. The porosity of the mesoporous silica was tuned by adjusting the ratio of template triblock copolymers (Pluronic P123 and F68). The Pluronic P123:F68 ratios of 3:1, 2:2, and 1:3 produced mesoporous silica with pore volumes of 0.66 (TiO2/SBA-L), 0.47 (TiO2/SBA-M), and 0.25 (TiO2/SBA-S) cm3/g, respectively. X-ray scattering and electron microscopy confirmed the SBA-15 structure of the as-prepared material had a size of 3–5 μm. The maximum adsorbability of fluoranthene and methylene blue was found to be 43% and 53% for the TiO2/SBA-S under UVA light, respectively. The avobenzone loaded into the mesoporous silica demonstrated the synergistic effect of in vitro UVA protection, reaching an UVA/UVB absorbance ratio of near 1.5 (Boots star rating = 5). The encapsulation of avobenzone into the TiO2/SBA-S lessened cutaneous avobenzone absorption from 0.76 to 0.50 nmol/mg, whereas no reduction was detected for the TiO2/SBA-L. The avobenzone-loaded TiO2/SBA-S hydrogel exhibited a greater improvement in skin barrier recovery and proinflammatory mediator mitigation compared to the SBA-S hydrogel (without TiO2). The cytokines/chemokines in the photoaged skin were reduced by two- to three-fold after TiO2/SBA-S treatment compared to the non-treatment control. Our data suggested that the mesoporous formulation with low porosity and a specific surface area showed effective adsorbability and UVA protection, with reduced UVA filter absorption. The versatility of the developed mesoporous system indicated a promising potential for outdoor skin protection.

Effect of Ultrasonic Pretreatment on Flocculation Filtration of Low-Rank Coal Slurry.

The efficient filtration of low-rank coal (LRC) slurry was significantly beneficial to the production process of wet coal beneficiation. However, relatively few studies have been reported on novel pretreatment methods for the efficient filtration of LRC slurry. In this paper, the mechanism of ultrasonic pretreatment to promote flocculation and filtration of slurry was studied. The hydrophobic variation of the slurry surface was measured by contact angle and XPS. The flocculation properties of slurry were characterized using zeta potential and FBRM. The effects of filter cake porosity and ultrasonic pretreatment on slurry filtration resistance were calculated by L-F NMR and Darcy’s theory. The results showed that the ultrasonic pretreatment promoted the flocculation and filtration performance of LRC slurry, increased the filtration rate, and decreased the cake moisture content. Meanwhile, the contact angle of LRC increased significantly from 50.1° to 67.8° after ultrasonic pretreatment, and the surface tension of the filtrate decreased from 69.5 to 53.31 mN/m. Ultrasonic pretreatment reduced the absolute value of the zeta potential of coal slurry from 24.8 to 21.0 mV, and the average chord length of flocs increased from 5–10 μm to 25–30 μm, thus weakening the electrostatic repulsion between coals to promote floc formation. In addition, the pore tests and filtration theory calculations showed that the ultrasonic pretreatment significantly improved the permeability of the filter cake to water and reduced the resistance to slurry during filtration. In particular, the mesopore porosity increased by 9.18%, and the permeability increased by 2.937 × 108 m2. Therefore, this contributed to the reduction of slurry filtration resistance. This research provides an efficient method for promoting the efficient filtration of slurry.

Effect of surfactant and flocculant on low-rank coal slime filtration: From filter cake characteristics point of view

Filter aids are widely used in low-rank coal (LRC) slime filtration. However, their impact on filter cake characteristics is still unclear. In this paper, the effect of anionic polyacrylamide (APAM) and cetyltrimethylammonium bromide (CTAB) on the filter cake characteristics was investigated using Darcy’s filtration theory and low-field nuclear magnetic resonance (L-F NMR). The slime and filtrate property change was determined by contact angle, XPS, FBRM, Zeta potential and surface tension measurements. The results showed that the filter aid improved slime filtration rate and reduced filter cake moisture. The filter aid effect of APAM was better than that of CTAB. CTAB significantly improved the slime surface hydrophobicity with the contact angle increasing to 90.5°, and reduced the filtrate surface tension to 35.26 mN/m. However, APAM decreased the absolute value of slime Zeta potential by 7.48 mV, and increased the slime floc size by about 7–9 µm. Both CTAB and APAM can reduce the filtration resistance, but the effect of APAM was better than that of CTAB, because APAM greatly improved the filter cake permeability. L-F NMR results showed that CTAB increased the filter cake porosity only by 2.65%, while APAM significantly improved the filter cake porosity by 11.65%, especially the mesopore porosity of cake, which increased by 10.48%. It was indicated that CTAB reduced the filtration resistance by “lubricating” the pore wall of the filter cake, while APAM improved the filter cake porosity and permeability by weakening the electrostatic repulsion between slime particles and promoting floc formation through aggregation effect. This research provided a new perspective to reveal the mechanism of LRC slime filtration.

Synergistic effect of bulking agents and biodegradation on the pyrolysis of biodried products derived from municipal organic wastes: Product distribution and biochar physicochemical characteristics

Derived from municipal organic wastes (MOWs), biodried products (BPs) are widely accepted as carbon-neutral and renewable energy resources. In this study, the pyrolytic products of BPs, i.e., syngas, tar and biochar, were comprehensively investigated, with a special focus on the synergistic effect of bulking agents (BAs) and the modification of biodegradation. Compared with the theoretical yields (31.12%–34.94%), the interactions of MOWs and BAs promoted biochar formation (34.65%–37.74%) during pyrolysis of raw materials (RMs). Biodegradation further enhanced the biochar yield (40.73%–49.50%) but limited the liquid yields (29.49%–38.04% vs. 39.75%–43.40%) during pyrolysis of BPs. Furthermore, biodegradation also enriched H2 in the syngas and promoted the formation of phenolic compounds (30.19%–47.83% vs. 11.08%–26.55%) in the tars during BP pyrolysis. In addition, the BP-biochar presented a higher porosity of mesopores, larger total volume (0.130–0.170 cm3/g) and pore size (4.15–4.77 nm); therefore, it had a higher methylene blue adsorption capacity than the RM-biochar (50.9–84.4 vs. 21.1–44.5 mg/g). These findings suggested that the interactive effect of BAs and the modification of biodegradation were effective in upgrading the pyrolytic products, including H2-rich syngas, phenolic-rich tar and mesoporous biochar. This study provides a promising strategy for the efficient utilization of MOWs by integrating biodrying and pyrolysis.

Green synthesis of hierarchical porous carbon with adjustable porosity for high performance supercapacitors

We prepared hierarchical porous carbon based on the metathesis reaction of K2CO3 with CH3COOH. During carbonization, the reactant (K2CO3) and the reaction product (CH3COOK) acted as activators and templates. The influence of the ratio of K2CO3/CH3COOK on the electrochemical performance of hierarchical porous carbon was explored. The obtained porous carbon has a high specific surface area (2289 m2 g−1) and adjustable micro-/mesoporous porosity. When the molar ratio of K2CO3/CH3COOK is 1, the specific capacitance is 374.4 F g−1 at 1 A g−1, and the capacitance retention rate reaches 76.4% when the current density increases to 10 A g−1. The assembled symmetrical supercapacitor (PC-2/PC-2) has a excellent cycle stability in 1 M Na2SO4 within the voltage window of 0–2.0 V. When the power density is 500.02 W kg−1, the maximum energy density of 29.14 Wh kg−1 is obtained. These results show superb performance in supercapacitor based on the metathesis reaction of K2CO3 with CH3COOH.

Damage caused by freeze‐thaw treatment with liquid nitrogen on pore and fracture structures in a water‐bearing coal mass

AbstractThe purpose of the study was to explore the microscopic and mesoscopic damage mechanisms of water‐bearing coal mass in the freeze‐thaw process with liquid nitrogen. For this purpose, by using a Zeiss microscope, a nonmetal ultrasonic velocity detector and a nuclear magnetic resonance (NMR) spectrometer, the changes in the structures of surface fractures and pores before and after coal masses with different moisture contents when subjected to freeze‐thaw treatment with liquid nitrogen (FTTLN) were tested. The result showed that under the freeze‐thaw effect of liquid nitrogen, the structures of surface fractures and internal pores of coal mass were both changed. Upon increasing the moisture content of the coal, the width of surface fractures increased; the surface fractures showed significant fractal characteristics: The higher the moisture content of the coal, the greater the rate of change of fractal dimension after FTTLN; the ultrasonic wave velocity in the coal mass gradually decreased after FTTLN, and the greater the moisture content, the more significant the decrease in ultrasonic wave velocity; under the freeze‐thaw effect of liquid nitrogen, the pore structure in the coal mass was transformed from micropores and small pores to mesopores and macropores and certain new micropores and small pores were generated. Upon increasing the moisture content of the coal mass, the peak area of micropores and small pores and their proportion decreased at first and then increased (reaching the minimum at 9.12% of moisture content); the peak area, peak area proportion, and porosity of mesopores and macropores always increased. The damage factor attained based on the width of fractures, longitudinal wave velocity, fractal dimension of surface fractures, and porosity was favorably correlated with the moisture content: With increasing moisture content, the coal mass became more severely damaged.

Lattice Boltzmann simulation of intraparticle diffusivity in porous pellets with macro-mesopore structure

Intraparticle diffusion inside porous pellets plays a controlling step in most reactive transport processes. In order to investigate microscopic diffusion process in porous pellets with macro-mesopore structure, a three-dimensional lattice Boltzmann method (LBM) approach with multi-relaxation-time (MRT) collision operator was utilized to calculate the intraparticle diffusivity. With respect to the hierarchical pore structure, the modified random generation of macro-meso pores (RGMMP) algorithm was proposed to obtain pore structure of porous pellets. In this work, a resin catalyst that has macro-mesopore structure was selected as a validation example. Based on the LBM approach, the effects of four geometrical parameters of the modified RGMMP algorithm on the intraparticle diffusivity, namely the total porosity, the ratio of mesopore porosity to macropore porosity, the ratio of average macropore diameter to mesopore diameter and the macropore growth direction were investigated, so as to elucidate the mass transfer mechanism in porous pellets with macro-mesopore structure. These theoretical findings are useful for the pore structure optimization design of porous pellets with macro-mesopore structure.

Two-Phase Diffusion Technique for the Preparation of Ultramacroporous/Mesoporous Silica Microspheres via Interface Hydrolysis, Diffusion, and Gelation of TEOS.

Honeycombed hierarchical ultramacroporous/mesoporous silica microspheres were prepared via the hydrolysis of TEOS in the oil-water interface, with subsequent diffusion and gelation in the acidic water-phase microdroplets with the assistance of a simple homemade microdevice. The diffusion of furfuryl alcohol (FA) also happened at a relatively high rate during the hydrolysis and diffusion of TEOS. Therefore, plenty of FA will be inside of the water microdroplets and form a decent number of polyfurfuryl alcohol (PFA) microparticles, thereby obtaining honeycombed hierarchical porosity silica microspheres with abundant ultramacroporous cavities and mesopores after calcination. It was found that the concentration of FA, residence time, and reaction temperature have significant effects on the porosity and pore size due to the influence on the diffusion rate and amount of FA in water-phase microdroplets. The honeycombed silica microspheres have obvious microscopic visible ultramacroporous cavities with the submicrometer cavity diameter as high as 85% porosity based on the rough overall volume of microsphere. N2 adsorption-desorption isotherms show that the honeycombed hierarchical porosity silica microspheres have a high surface area of 602 m2 g-1, a mesopore volume of 0.77 cm3/g, and a mesopore porosity of 99.6% based on the total pore volume of N2 adsorption-desorption. On the basis of the experiment results, a rational formation process of the honeycombed hierarchical porosity silica microspheres was deduced.

Controllable synthesis of mesoporous multi-shelled ZnO microspheres as efficient photocatalysts for NO oxidation

The successful application of hierarchically porous structure in environmental treatment has provided new insights for solving environmental problems. Hierarchically structured semiconductor materials were considered as promising photocatalysts for NO oxidation in gas phase. Multi-shelled ZnO microspheres (MMSZ) were controllably shaped with hierarchically porous structures via a facile hydrothermal route using amino acid (N-Acetyl-d-Proline) as template and post-calcination treatment. Symmetric Ostwald ripening was used to explain the morphological evolution of hierarchical nanostructure. MMSZ was proved highly efficient for oxidizing NO (400 ppb) in gas phase under UV light irradiation with a much higher photocatalytic removal rate (77.3%) than that of the as-obtained ZnO crystals with other hierachically porous structures, owing to its higher photocurrent intensity. Such greatly enhanced photocatalytic activity can be assigned to the enhanced crystallinity of ZnO, mesopores and unique multi-shelled structure. Enhanced crystallinity promotes photogenerated charges under light irradiation. Mesoporous porosity can ensure enough light scattering between the shells. Multi-shelled structure endows ZnO with higher specific surface area and high frequency of multiple light reflection, resulting in more exposed active sites, higher light utilization efficiency, and fast separation efficiency of photogenerated charge carriers. The experimental results demonstrated that the photogenerated holes (h+) are the main active species. Hierarchically structured ZnO is not only contributed to directly use solar energy to solving various problems caused by atmospheric pollution, but also has potential applications in energy converse and storage including solar cells, lithium batteries, water-splitting, etc.

MnOx-TiO2 and Sn doped MnOx-TiO2 selective reduction catalysts prepared using MWCNTs as the pore template

The stability of MnOx based low temperature SCR catalysts remained to be a serious issue. This report explored use of multi-walled carbon nanotubes (MWCNTs) network with uniform structure as a “rigid” pore template for synthesis of mesoporous MnOx-TiO2 SCR catalyst with high surface area and high stability. The results showed that MWCNT network imposed MnOx-TiO2 catalyst a mesoporous porosity with a narrow pore size distribution centered on ∼13.2nm and a surface area of 131.6m2g−1 stabilized at 500°C. The mesoporous structure was formed by interconnected nanoparticles, comprised of crystallized rutile TiO2 core surrounded by amorphous MnOx, with an average diameter of ∼8nm. The catalyst exhibited an excellent low temperature SCR activity and selectivity as well as high resistance to deactivation and poison by H2O and SO2. SnO2 modification led to degradation of catalytic performance in low temperature (60–180°C) side, but improvement at high temperature side (240–360°C), especially at high gas velocity, which can be attributed to change in structure, reactivity of MnOx and surface acidity induced by SnO2 addition.

Pore throat structure and fractal characteristics of tight oil sandstone: A case study in the Ordos Basin, China

Pore throat structure is a significant factor controlling the properties of reservoir. Evaluation of the pore throat structure is also important for the exploration and development of tight oil. In order to determine the micro-structure of pore throat, the high pressure mercury intrusion experiments (HPMI) were performed on the tight oil sandstone samples of Chang 7 member in Xin’anbian Block, Ordos Basin, China. HPMI were conducted to obtain the microscopic parameters of the pore throat structure, such as pore-size distribution, pore connectivity, and pore space topology.The pore throat network of the tight oil sandstone mainly consists of micropores, transitional pores, and mesopores. The mesopores of the Chang 7 tight reservoirs is the dominant factor affecting the pore throat structure. Mesopores development positively influences the maximum pore radius, median radius, sorting coefficient, skewness, maximum mercury saturation, and efficiency of mercury withdrawal, indicating that with the development of mesopores, the properties of percolation, storage, pore throat connectivity, and oil recovery would become better. Fractal theory was used to quantitatively characterize the complex and irregular pore throat structure of the reservoir. The fractal dimensions of mesopores, transitional pores and micropores (D1, D2, and D3) were calculated through the slopes of the trendlines of each segment obtained from the curve of log (1-SH) versus log (Pc). The total fractal dimension (D) was obtained, based on the weighted average of porosity of mesopores, transitional pores, and micropores. D ranging of 2.2520–2.7875 indicates that the pore throat structure of Chang 7 tight reservoir is complex and has a strong heterogeneity. D1, D2, and D3 have obvious negative correlations with porosity of the corresponding pores and only D1 has an obviously negative correlation with permeability. D has a downward trend, with the increasing porosity, but no correlation with permeability. D1 has better correlations with the parameters of pore throat structure than D2 and D3. The heterogeneity and surface roughness of mesopores mainly influence the property of pore throat structure, especially percolation and storage space of the reservoir. The development of mesopores is a main factor affecting the pore throat structure of the Chang 7 tight oil sandstone. The fractal characteristic of mesopores reflects how well the pore throat structure for the exploration and development of Chang 7 tight oil.

A smart processing of silicon oxynitride ceramic powders with variable morphology controlled by hard template assistance

Spherical and rod-like Si2N2O ceramic powders were successfully prepared using a hard template strategy to meet different application background. The mesoporous silica spheres and rod-like silica (SBA-15) particles were selected as hard templates and also served as reactants. Highly active mesoporous silica is reacted through a combination of sucrose-nano-casting and carbothermal reduction nitridation (CRN) to successfully synthesize spherical and rod-like powders. Temperature and holding time of calcination are found to be significant factors for the formation of pure and well-crystallized powders. Insufficient temperature and holding time cause an incomplete reaction between silica, carbon and nitrogen, and also lead to the formation of amorphous phase. In the processing, sucrose was used as carbon source to incorporate evenly into mesopores of templates to assist CRN reaction. Big surface areas and high porosity of mesopores in SiO2 provide an additional driving force to decrease the formation temperature of Si2N2O phase to 1280°C. As-synthesized powders inherit same morphology as their parental mesoporous templates, which indicate that two mesoporous templates play an important role in guiding the growth of ceramic particles. In the research, we develop a smart processing for synthesis of oxynitride powders with variable morphology controlled by template.

Hierarchical structure and catalytic properties of a microspherical zeolite with intracrystalline mesopores

An effective microspherical zeolite MFI for large molecules was prepared for the first time. The material is found in a microspherical form 5.0μm in size, and the microspheres are composed of 20–30-nm nanoparticles. The nanoparticles further contain uniform intracrystalline mesopores of ∼3.0nm. The mesopores in the material are generated in the course of crystallization, owing to bond-blocking from silanized silicon dioxide, and the mesoporous porosity can be effectively adjusted though different degrees of silanization. During the synthesis, an excess of grafted organic species on the silica surface inhibits the formation of zeolitic phases. The formation of the microsphere is attributed to the glomeration of halogen anions and/or the salts present during the synthesis. Fourier transform infrared spectrophotometry and 29Si and 27Al nuclear magnetic resonance results confirm that the existence of silanol groups is directly related to the rich crystalline defect sites. The adsorption of alkali molecules with different kinetic diameters (0.5–0.8nm) indicates that the mesopores generated in the zeolite catalyst markedly increase the accessibility of micropores and the availability of acid sites, which is confirmed by high performances observed in catalytic conversions, such as cumene cracking, benzylation of benzene, and methanol conversion to gasoline. The introduction of auxiliary mesoporosity to the zeolitic catalyst is believed to improve molecule transport and enhance the accessibility of active sites in the microporous structure.

Investigation on the Textural Properties Tuning of Ordered Mesoporous Carbons with an Excellent Electrochemical Performance

A synthetic method to produce mesoporous carbons with tunable textural properties and ordered pore structure has been developed by changing sucrose to water ratio. The specific surface area of 1437 m2/g with pore volume of 1.4 cm3/g and porosity of mesopores centered at around 4.4 nm are achieved by tuning the concentration of filling amount into mesoporous silica. The mesoporous carbon exhibits hexagonal rod-like morphology (a diameter of ~1.2 m), which confirms that the replication process is highly successful. It is demonstrated that the prepared mesoporous carbon exhibits much higher current density and superior performance as compared to conventional activated charcoal.

Preparation of monolithic columns with target mesopore-size distribution for potential use in size-exclusion chromatography

The main factors affecting the mesopore porosity of methacrylate-ester based monolithic columns were investigated. We prepared 40 monolithic capillary columns with porosity controlled by varying the proportions of butyl methacrylate (BMA) and ethylene dimethacrylate (EDMA) monomers and of 1,4-butanediol (BUT) and 1-propanol (PROP) as the porogen solvent in the polymerisation mixtures by thermally initiated in situ polymerisation in fused-silica capillaries. Using mixture design software, we systematically varied the composition of the polymerisation mixtures to find significant factors affecting mesopore formation. Multivariate analysis of the experimental data obtained for the fabricated columns yielded a model for prediction of the mesopore porosity in monolithic beds as a function of the composition of the polymerisation mixture used to prepare polymethacrylate monolithic capillary columns. The mean absolute deviation of predicted porosities is 0.029 for most of the columns, with only eight columns showing deviations exceeding 0.050. The main factor affecting the mesopore porosity proved to be the combination of the concentration of hydrophobic monomer (BMA) and the concentration of the less-polar solvent, 1-propanol, in the porogen mixture. The proportion of mesopores in the monolithic capillary columns increases with increasing concentration of 1-propanol and with decreasing concentration ratios of the cross-linker (EDMA) to monomer (BMA) and of BUT to PROP porogenic solvents.

Ageing-induced enhancement of open porosity of mesoporous silica films studied by positron annihilation spectroscopy

We show that ageing of the silica sol in a closed vessel enhanced the open porosity of calcined mesoporous silica film studied by positron. Positron annihilation lifetime spectroscopy (PALS) based on a pulsed slow positron beam was used to estimate the mesopore size. 2-dimensional PALS (2D-PALS) and ortho-positronium time-of-flight (Ps-TOF) were used to evaluate the open porosity, interconnectivity and tortuosity of mesopores in the silica films. Results revealed that little change in pore size but significant enhancement of open porosity and/or pore interconnectivity occurred in the silica film deposited after the precursor solution aged for a relative longer time.