Effect Of Mesoporous Structure Research Articles

Efficient dye adsorption of mesoporous activated carbon from bamboo parenchyma cells by phosphoric acid activation.

In order to solve the environmental damage caused by the discharge of dyes as industrial wastewater, the development of efficient and sustainable adsorbents is the key, while most of the previous studies on bamboo parenchyma cells have focused on their microstructural, functional and mechanical properties, and few of the properties in adsorption have been investigated. To evaluate the role of the unique microstructure of bamboo parenchyma cells on adsorption after carbonization and activation, PC-based activated carbon (PPAC) was fabricated by the phosphoric acid activation method and tested for adsorption using methylene blue (MB). The effect of mesoporous structure on MB adsorption was investigated in detail using PPAC-30C impregnated with phosphoric acid at a concentration of 30%. The results showed that the adsorption performance was influenced by single-factor experiments (e.g., pH, activated carbon dosing). The adsorption isotherms and kinetics could conform to the Langmuir model (R2 = 0.983-0.994) and pseudo-second-order kinetic model (R2 = 0.822-0.991) respectively, and the maximum MB adsorption capacity of adsorbent was 576 mg g-1. The adsorption mechanism of MB on PPAC-30C includes physical adsorption, electrostatic attraction, hydrogen bonding, and the π-π conjugation effect, which was dominated by physical adsorption. The results of this study show that PPAC has good application prospects for cationic dye removal.

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.

Structure and near-infrared spectral properties of mesoporous silica for hyperspectral camouflage materials

Mesoporous silica materials were prepared via a hydrothermal method by adjusting the content of trimethylbenzene (TMB) and PEO-PPO-PEO block copolymer (F127) in mesoporous silica. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy(TEM), nitrogen adsorption–desorption analysis(BET),Fourier transform-infrared spectroscopy (FTIR) and Visible near infrared spectrophotometry (VIS-NIR). The effects of mesoporous structure on the water load capacity and near-infrared spectra were systematically then studied. The results showed that the pore size and volume of the mesoporous silica could be tuned by varying the dosage of TMB and F127. In addition, the hygroscopicity of the mesoporous silica was linearly dependent on the pore size and volume, and the as-prepared mesoporous silica had NIR spectral features similar to those of vegetation leaves. More interestingly, as the water content increased, the water absorption peak of the mesoporous silica in the NIR wavebands was closer to that of natural leaves, showing greater similarity. Finally, camouflage coatings were prepared by using the as-prepared mesoporous silica powder as a functional filler and water-borne polyurethane as an adhesive. The cosine similarity between the camouflage coating and natural leaves reached 98.49%, suggesting that the camouflage coating achieved strong similarity in simulating the reflection spectra of plant leaves, potentially providing a new approach to the design of functional fillers of camouflage materials.

Synthesis and characterization of meso-porous Au-modified SnO2 fibers using natural silk with enhanced sensitivity for n-butanol

Meso-porous SnO2 fibers were prepared via hydrothermal method, and natural silk was used as bio-template. Au nanoparticles served as the sensitizer were prepared on the surface of these SnO2 fibers to further enhance the properties of gas sensing. Results show that these Au-modified products presented high surface area of 168.66 m2/g and meso-porous structure, and these fibers were composed of nanosized SnO2 and Au particles with the size of about 7 ± 0.5 nm and 5 ± 0.5 nm, respectively. Gas sensing properties of these synthesized pristine products and Au-loaded fibers were investigated. Results show that these Au-modified SnO2 fibers exhibited remarkably enhanced sensing performance to n-butanol with high response, good selectivity and good stability. The gas sensing mechanism was discussed from the effects of meso-porous structure, high surface area and Au nanoparticle catalytic activity.

Effects of mesoporous structure and Pt promoter on the activity of Co-based catalysts in low-temperature CO2 hydrogenation for higher alcohol synthesis

Mesoporous Co3O4 (Co3O4-m) was synthesized with mesoporous silica (KIT-6) as a hard template. Co3O4-m was characterized by in situ reduction XRD, BET, TEM, and H2 TPR. The partly reduced Co3O4-m was studied as a catalyst for higher alcohol synthesis from CO2 hydrogenation. The metallic Co reduced from Co3O4 was the main activity site for the CO2 hydrogenation. The ordered mesoporous structure of the Co3O4-m catalyst promotes the growth of carbon chains for the production of higher hydrocarbons and alcohols and reduces the selectivity for CH4 from that of the partially reduced Co3O4 nanoparticles. The highest yield of higher alcohols was obtained in 1.6 mmol gcat−1 h−1 at 200 °C over the Co3O4-m catalyst, which was reduced at 300 °C. In addition, the selectivity for CH4 further decreased at 200 °C over the Pt/Co3O4-m catalyst, while the selectivity for CO and alcohols increased, owing to the reverse water gas shift ability of Pt. However, the conversion of CO2 significantly decreased. The yield of higher alcohols (1.5 mmol gcat−1 h−1) was slightly lower than that of Co3O4-m catalysts under the same reaction conditions.

Heterogeneous Fenton-like degradation of ofloxacin over a wide pH range of 3.6–10.0 over modified mesoporous iron oxide

To develop an efficient heterogeneous Fenton catalyst over a wide pH range without any external energy input is still a challenging work. In this study, the Fenton activity of mesoporous iron oxide was firstly extended to pH of 3.6–10.0 by the carbon quantum dots (CQDs) and Cu modification (CQDs/Cu-MIO). The characterization studies indicated that CQDs/Cu-MIO had a typical mesoporous structure and CQDs was highly dispersed on the surface of catalyst. While Cu element with Cu (I) and Cu (II) was introduced in the framework of iron oxide by chemical binding of FeOCu. Without the aids of UV, CQDs/Cu-MIO exhibited an excellent efficiency and the ofloxacin (OFX) degradation followed the pseudo-first order kinetic model with a reaction constant of 0.1109min−1. Moreover, the catalyst can be reused for 6 times with good stability, in which the maximum concentration of leaching Fe and Cu ions were 0.085 and 0.015mmol/L. The optimum reaction condition was evaluated and the degradation process of OFX was further investigated by FT-IR spectrum. The reactive oxygen species involved in OFX degradation, the effects of mesoporous structure, Cu/Fe multivalent state and the excellent capability of electron transformation/energy exchange of CQDs on the enhancement of CQDs/Cu-MIO Fenton activity were also discussed. Finally, the heterogeneous Fenton reaction mechanism was proposed based on the experimental results.

Effect of mesoporous structure on the Seebeck coefficient and electrical properties of SrTi0.8Nb0.2O3

The porosity of mesoporous SrTi0.8Nb0.2O3 (STNO) was controlled by changing the surfactant concentration to investigate the porosity effect on the thermoelectric properties. Mesoporous structure typically induces a large decrease in the carrier mobility and a small increase in the carrier concentration owing to carrier scattering and oxygen vacancies. These changes in the carrier mobility and concentration induce a change in the thermoelectric properties by enhancing the Seebeck coefficient owing to an increase in the electrical resistivity and carrier filtering effect. Brij-S10 surfactant induces a carrier filtering effect in STNO, and so the Seebeck coefficient could be enhanced even with increasing carrier concentration. Because the Seebeck coefficient affects the power factor more strongly than the electrical resistivity does, incorporation of Brij-S10 surfactant into STNO films increases the power factor. The maximum value of the power factor, approximately 2.2×10−4W/mK2 at 200°C, was obtained at a Brij-S10 molar ratio of 0.075. From this result, we can expect the application of STNO as a thermoelectric material with an enhanced power factor through successful adoption of mesoporous structure.

Copper and chromium oxide nanocomposites supported on SBA-15 silica as catalysts for ethylacetate combustion: Effect of mesoporous structure and metal oxide composition

Copper and chromium oxide nanocomposite materials with different Cu/Cr ratio are prepared by deposition on silica host matrices with different textural properties and characterized by XRD, nitrogen physisorption, UV–Vis, FTIR, XPS and TPR-TG. Their catalytic behavior in ethylacetate total oxidation was also studied. A complex effect of Cu/Cr ratio, textural characteristics of the support and reaction medium on the phase composition of the supported active phase was found. Different mechanisms of regulation of loaded metal oxides dispersion depending on the support peculiarities were discussed. The relation between the phase composition and the catalytic properties of various bi-component materials was studied.

Effects of mesoporous structure and UV irradiation on in vitro bioactivity of titania coatings

Mesoporous titania coatings (MTCs) with a pore size of 4.75 nm were prepared on Ti6Al4V substrates by a sol–gel process, and then irradiated with UV light at room temperature for 2 h. The effects of mesoporous structure and UV irradiation on the in vitro bioactivity were investigated. Simulated body fluid (SBF) tests reveal that the MTCs exhibit a high apatite-forming ability, which may be attributed to the following reasons: (i) the BET surface area of the MTCs is ∼190 m 2/g, resulting in a greater density of Ti–OH groups than that without mesoporous structure; (ii) theoretical analysis reveals that the mesoporous structure can improve the driving force and nucleation rate of apatite precipitation in SBF. As compared with the MTCs, the UV-irradiated coatings do not exhibit any change in phase components and surface morphologies. However, the apatite-forming ability is higher on the UV irradiation coatings than on the MTCs because of the increase of Ti–OH groups and the improvement of wettability after UV irradiation. In addition, the investigation of the MG63 cell proliferation on the both substrates was performed. The results indicate that the MTCs before and after UV irradiation exhibit a good biocompatibility and are fit for the MG63 cell proliferation.

Effects of mesoporous structure on grain growth of nanostructured tungsten oxide

The effects of mesoporous structure on grain growth were investigated in this study. The synthesis was accomplished using block copolymer as the organic template and tungsten chloride as the inorganic precursor. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, x-ray diffractometry (XRD), transmission electron microscopy, and N2 adsorption/desorption isotherms were used to characterize the microstructures obtained for different temperatures. TGA and XRD analyses demonstrate that copolymers were expelled at 150–250 °C, and mesoporous structure was stable up to 350 °C. The pore diameter and the surface area evaluated from the Barrett-Joyner-Halenda model and Brunauer–Emmett–Teller method indicated that the average pore diameter is 4.11 nm and specific surface area is 191.5 m2/g for 250 °C calcination. Arrhenius equation used to calculate the activation energy for grain growth demonstrates that the activation energy for grain growth was about 38.1 kJ/mol before mesostructure collapse and 11.3 kJ/mol after collapse. These results show evidence of two different mechanisms governing the process of grain growth. The presence of the pore can be related to the obstacle for grain growth.