Preparation Of Mesoporous Silica Research Articles

Pivotal role of pH value in the preparation of mesoporous silica with high surface area for toluene adsorption

Porous silica samples were prepared by a non-template approach using silicate and HCl at different pH values. Macroporous silica with a low surface area of 72.0 m2/g was obtained at pH = 7. Surprisingly, mesoporous silica with very high surface area of 806.0 m2/g was obtained at pH = 3. This was due to the formation of protonated silicic acid molecules under acidic condition which had enough time for the polymerization and assembly to mesoporous structure, and the rapid polymerization and assembly of silicic molecules under neutral condition to silica nanoparticles among which macropores were formed. The mesoporous silica showed a saturation toluene adsorption capacity of 79.1 mg g−1, 9 times higher than that of the macroporous silica.

Modified mesoporous silica derived from bamboo leaf using cetyltrimethylammonium bromide and 3-aminopropyl triethoxysilane as CO2 adsorbentinbiogas purification.

The calorific value of post-fermentation biogas is a way down below standard and quite low due to the presence of high amount level of carbon dioxide (CO2) biogas mixture. Therefore, it raises the need to process the biogas, separating it from CO2 in order to obtain high-purity biogas as well as to maximize its calorific value. One widely available material that can be used as a sustainable carbon capture adsorbent is silica extracted from bamboo leaves. However, so that silica can act as CO2 adsorber, it is necessary to modify the surface of silica with CTAB and APTES (3-aminopropyl triethoxysilane). In this study, 2-stage method was carried out, namely preparation of mesoporous silica and surface modification using APTES on the mesoporous silica. Experiments in synthesizing APTES-modified silica were obtained by varying its composition: CTAB (1.5-5%w), (HCl 1.5-5 N), and APTES (10-30%). A central composite design (CCD) was employed in exploring the interaction between all variables and also performed for the optimization. Through analysis of variance, it shows that optimum CO2 adsorption capacity reaches 47.02mgg-1, by applying 4.98% of CTAB, 4.28N of HCl and 10.08% of APTES. Pseudo-second-order kinetic and Redlich-Peterson isotherm models are more representative to show the adsorption behavior of CO2 into the modified silica. The results show that the modified silica with APTES shows a prospective application of silica for CO2 removal from biogas.

Preparation of mesoporous silica and organosilica nanostructures functionalized with C2‐symmetric diol and their catalytic performance in diethylzinc addition to aromatic aldehydes

In this study, heterogenization of C2‐symmetric (1R,2R)‐1,2‐bis(4‐(3‐(triethoxysilyl)propyl)phenyl)ethane‐1,2‐diol compound and investigation of the effect of structural arrangements of nanocatalysts on catalytic activity were carried out. For this, bissilyl derivative of (1R,2R)‐1,2‐bis(4′‐bromophenyl)‐ethane‐1,2‐diol, named as C2‐BSi, was obtained by 2‐step synthesis. Then, mesoporous silica nanocatalysts C2‐BSi@SBA‐15 and C2‐BSi@MCM‐41 were synthesized by grafting of C2‐BSi onto SBA‐15 and MCM‐41, whereas mesoporous organosilica nanocatalysts C2‐BSi‐MON‐(a) and C2‐BSi‐MON‐(b) were synthesized by co‐condenzation of C2‐BSi and tetraethyl orthosilicate (TEOS). Structure determinations of synthesized organic substances were performed by 1H, 13C NMR, Fourier transform infrared (FT‐IR), polarimeter, and mass analysis, whereas the structural properties of heterogeneous catalysts C2‐BSi@SBA‐15, C2‐BSi@MCM‐41, C2‐BSi‐MON‐(a), and C2‐BSi‐MON‐(b) were determined by FT‐IR, X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), and N2 sorption analyses. The catalytic activities of novel heterogenous materials were tested in the reaction of Ti‐promoted enantioselective diethylzinc addition to aromatic aldehydes. The effects of the structural arrangements of the prepared heterogeneous catalyst on the catalytic activity were examined and compared with the catalytic activity values of their homogeneous analog. According to the results, all catalysts catalyzed the reactions and afforded the corresponding products with high conversion (82–99%) but low enantioselectivity (rac‐7% ee). The conversion values in heterogeneous catalysis were higher than those in homogeneous catalysis. C2‐BSi‐MON‐(a) with the largest pore width stood out as the most effective catalyst (99% conversion, 7% ee). The findings from the catalytic activity experiments confirmed that the structural arrangement of the nanocatalysts has an effect on the performance of the catalysts in the reaction.

Hierarchical porous nanosilica derived from coal gasification fly ash with excellent CO2 adsorption performance

The preparation of mesoporous silica from solid waste is an effective method to realize high-value utilization of solid waste and reduce the synthesis cost of mesoporous silica. However, the silica derived from solid waste often suffers from small pore size and weak adsorption capacity. Besides, the traditional method of extracting silicon from solid waste requires high-temperature melting in the presence of a large amount of alkali, resulting in equipment corrosion. In this work, hierarchical porous nanosilica was prepared via microwave-assisted alkaline extraction followed by hydrothermal synthesis, using coal gasification fly ash (CGFA) as silicon source. The microwave assisted alkali-dissolution process is fast in silicon extraction and induces less impurity metal ions. Besides, the Fixed Carbon in CGFA was degraded into C20H24O3, C5H10O and C16H35NO3. These compounds acted as swelling agent, inducing intergranular pores with sizes greater than 10 nm in the nanosilicas. The isosteric heat of adsorption of the hierarchical porous nanosilica was −30.06 kJ/mol, indicating that CO2 was adsorbed by the hierarchical porous nanosilica via both physisorption and chemisorption. Chemisorption was induced by the surface silanol and its density increased with the intergranular pores. Because the intergranular pores and surface silanol group provided more adsorption sites, the CO2 adsorption capacity of the hierarchical porous nanosilica was significantly improved, which reached 1.63 mmol/g at 30 ℃ and 1 bar.

Preparation of mesoporous silica with monomodal and bimodal pore structure using co-condensation method and its application for CO2 separation

Preparation of mesoporous silica with monomodal and bimodal pore structure using co-condensation method and its application for CO2 separation

Pore size control of monodisperse mesoporous silica particles with alkyl imidazole ionic liquid templates for high performance liquid chromatography applications

The control of pore size in mesoporous silica particles is still a topic of considerable research attention for the preparation of chromatographic packing materials. In this study, three alkyl imidazole ionic liquid surfactants ([BRIJOn-MIM]Ts (n = 2, 10, 20)) were synthesized from polyoxyethylene oleyl ether (BRIJ™On, n = 2, 10, 20), 1-methylimidazole, and p-toluenesulfonyl chloride. [BRIJOn-MIM]Ts (n = 2, 10, 20) exhibited different template behaviors in the preparation of mesoporous silica, and hollow silica with worm-like vesicle structures, spherical silica, and gel were obtained, respectively. Monodisperse sub-3 µm core-shell silica particles (CSSPs) with narrow pore size distribution were successfully prepared by the ultrasound-assisted sol-gel method using [BRIJO10-MIM]Ts as the template. A shell thickness of up to 300 nm was obtained, and the pore size was expanded from 4.7 to 7.3 nm by adjusting the reaction parameters, overcoming the limitation of pore size to less than 4 nm when using organic alkyl quaternary ammonium or alkyl imidazolium surfactants as the templates. The synthesized 2.7 µm CSSPs were functionalized with tert-butylcarbamoylated quinine and used as an anion exchange chiral stationary phase, exhibiting excellent separation performance for N-substituted amino acid enantiomers.

Preparation of Physical-modified Mesoporous Silica

Based on the concept of molecular design, mesoporous silica materials with different physical structure and morphology were prepared by adjusting the molecular chain length of surfactants and the mass ratio of anion-cationic surfactants. The composition and morphology of the prepared silica materials were characterized by FTIR, SEM, N2 adsorption and desorption. By adjusting the carbon chain length of surfactants and the mass ratio of anion-cationic surfactants, the preparation of mesoporous silica was carried out, and the effects of mesoporous silica on the internal structure of mesoporous silica were analyzed.

Preparation of Mesoporous Silica by Nonionic Surfactant Micelle\u2013Templated Gelation of Na2SiO3 and H2SiF6 and Application as a Catalyst Carrier for the Partial Oxidation of CH4

Mesoporous silica (MSPN12) was prepared by nonionic surfactant micelle–templated gelation of sodium silicate (Na2SiO3) and fluorosilicic acid (H2SiF6) in aqueous solution, characterized by a range of instrumental techniques, and tested as a support for Ni and Rh catalysts in the partial oxidation of methane (POM). Calcined and sintered MSPN12 exhibited well-defined d00l-spacings (3.5–4.39 nm), narrow pore distributions (2.4–3.1 nm), and large specific surface areas (552–1,246 m2 g−1), and was found to be highly thermally stable. Microscopic imaging revealed that MSPN12 comprised spherical particles with a uniform diameter of ~0.7 µm, with each particle featuring firm and regular honeycomb-type pores. MSPN12-loaded Ni and Rh maintained stable POM activity at 700 °C during almost 100 h on stream, which were comparable to those for the commercial Rh(5)/Al2O3 catalyst in terms of methane conversion and H2 formation selectivity. Thus, the combination of structural stability and favorable physicochemical properties resulted in good POM performance.

Preparation of mesoporous silica supported sulfonic acid and evaluation of the catalyst in esterification reactions

Sulfonic acid group was chemically bonded on either amorphous or highly ordered mesoporous silica surface through hydrothermal treatment with Na2SO3/NaHSO3 aqueous solution followed by acidification after the silica was grafted with surface propyl-chloride group. N2 adsorption–desorption was used for the characterization of the topology properties of the mesoporous silica–SO3H catalysts and the acid amount was studied by titration. Solid NMR and FTIR techniques were employed for detection of the surface groups and covalently bonded propyl–SO3H species was identified. The solid acid catalyst was evaluated in esterification reactions between various carboxylic acids and short-chain alcohols and the results demonstrated that the mesoporous silica–SO3H catalyst shows not only a high activity comparable to that of reported KIT-6-120–SO3H catalyst, but also an excellent recyclability (without deactivation after reused for eight times in lauric acid esterification with ethanol). The good performance and strong acidic character of the catalyst was correlated with the large pore size, well accessible acid sites as well as covalently grafted active structure on the catalyst.

Preparation of mesoporous silica by the rapid gelation of Na2SiO3 and H2SiF6 in aqueous surfactant solution

Abstract Microporous and mesoporous materials are used as catalyst carriers, adsorbents, and ion exchangers. In this study, mesoporous molecular sieves were prepared through the rapid reaction of Na2SiO3 and H2SiF6 in a water solution containing surfactants. Mesoporous silica (MS) precipitates were produced within 5 s and X-ray diffraction (XRD) analysis of the MS samples indicated the formation of mesoporous molecular sieves owing to the appearance of well-defined peaks at intervals of 3.8–5.2 nm. The specific surface area was 371 m2 g−1 when using a cationic surfactant and in the range of 959–1135 m2 g−1 in nonionic surfactants. The pore-size distribution of MS samples showed a constant value of 2.5–3.1 nm. The shape of the silica particles observed via scanning electron microscopy was spherical with a uniform size of ∼0.7 μm. Transmission electron microscopy images of the samples obtained using the nonionic surfactant showed worm-hole-shaped pores, whereas those obtained using the cationic surfactant had regular honeycomb-shaped pores. MS samples synthesized using nonionic surfactants were thermally very stable in the light of their XRD peaks being maintained at 900 °C. The intensity of Q3 and Q4 signals for the MS obtained by nonionic surfactant is double than that of cationic surfactant, proving that silicate network of MS-PL15 is lots thicker than that of MS-CTAB. MS synthesized by nonionic surfactant can be used as a catalyst support at high temperatures because they has a large specific surface area and excellent thermal stability.

Preparation of mesoporous silica from coal slag and its metal ion adsorption behavior

A novel mesoporous silica (MS) with the high specific surface area up to 1,199 m2/g was prepared from coal slag by SO 3 2− leaching and hydrothermal synthesis. Its application in metal ion removal was explored using Pb2+, Cu2+, Co2+ and Cd2+ as the model ions. The effects of adsorption time, pH, initial metal ion concentration, adsorbent dosage and adsorption temperature on the metal ion adsorption behaviors of the as-prepared MS were systematically, and the maximum adsorption capacities were measured to be 55.76 mg·g−1, 33.49 mg·g−1, 24.29 mg·g−1 and 22.98 mg·g−l for Pb2+, Cu2+, Co2+ and Cd2+, respectively. The metal ion adsorption on the as-prepared MS followed pseudo-second-order kinetics, and the adsorption isotherm fitted the Langmuir isotherm model, indicating that the adsorption was spontaneous, endothermic and enthalpy driven.

Effect of Temperature on Thermal Treatment of Silica Coated Magnetic Nanoparticles

In the quest for developing a catalyst with as many desired characteristics, a facile synthetic route was designed for the preparation of mesoporous silica coated magnetic nanoparticles(MSMNP) employing a colloid mill reactor. The composite particles were characterized by the techniques, such as nitrogen adsorption-desorption isotherms, scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction patterns (XRD), thermo-gravimetric analysis(TGA), Fourier transform infrared spectroscopy(FTIR) and vibrating sample magnetometer(VSM), etc. The analysis showed that the resulted MSMNP composites were composed of silica shell layers with open pores connecting channels and NiFe2O4 with spinel structure, so the thermal treatment temperature did not show significant effect on pore textural properties, and its specific surface areas were in the range of 443–474 m2/g, while pore volume of about 0.8 cm3/g with an average pore size of around 9.5 nm. The composites with super paramagnetic nature were encapsulated entirely with amorphous silica layers contributing to optimum porosity and abundant surface hydroxyl groups.

Preparation of mesoporous silica from a Nigerian talc ore by acetic acid treatment

A study on the preparation of porous silica from a Nigerian talc ore by acetic acid leaching was investigated. The initial and leached talc products were characterized by Energy Dispersive X-ray fluorescence EDXRF , X-ray diffraction XRD , Scanning Electron Microscopy SEM with Energy Dispersive spectroscopy EDS and the N2 adsorption techniques. The influence of acetic acid concentration, reaction temperature and particle size on the ore leaching kinetics were examined. The results of the dissolution rates were found to be significantly influenced by leachant concentration, temperature and decreasing particle size. The dissolution mechanism process followed the diffusion control shrinking core model with the calculated activation energy of 34.53 kJ/mol supporting the proposed mechanism. The leached product has a specific surface area increased to 2.056 m2 /g from the initial ore surface area of 0.15 m2 /g. At optimal leaching conditions, the pore size distribution calculated by Barret-Joyner-Halenda BJH method based on N2 gas isotherms showed the presence of peaks from micropores and mesopores formation, indicating the porous nature of the leached product.

Preparation of Mesoporous Silica from Electrolytic Manganese Slags by Using Amino-Ended Hyperbranched Polyamide as Template

Large quantities of waste slags are produced during the preparation of electrical manganese, causing serious pollution to the environment. The recycling and utilization of electrolytic manganese slags (EMS) is a serious challenge to the industry. Here, we report the utilization of EMS in preparation of high-performance mesoporous silica using amino-ended hyperbranched polyamide (AEHPA) as template. The effects of AEHPA content and molecular weight on properties of mesoporous silica, including the specific surface area, pore diameter, pore volume, size and distribution, have been investigated. Based on 0.3 wt% AEHPA-2 during preparing silica, the specific surface area, pore volume and pore diameter of the produced amorphous mesoporous silica are 451.34 m2•g-1, 0.824 cm3•g-1 and 7.09 nm, respectively, showing remarkable improvements over the silica without AEHPA with specific surface area (271.05 m2•g-1), pore volume (1.167 cm3•g-1) and pore diameter (17.43 nm). The formation mechanism of mesoporous silica ...

The phase behaviors of cationic and anionic aqueous mixtures and the usage as templates for synthesis of mesoporous materials

Liquid crystals formed in aqueous mixtures of cationic and anionic surfactants were used as structure- directing templates for preparation of mesoporous silicas. For this purpose, micellar particle sizes and liquid crystal regions in the mixed system containing cetyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) were investigated by Melvin laser particle size analyzer and polarizers, respectively. The formation of large organized assemblies was closely related to both the total surfactant concentrations and mixing ratios. Micelles formed at low total concentration while liquid crystals formed at high total concentration. The mixtures of CTAB and SDS favored the formations of large organized assemblies when the molar fraction of CTAB was 0.30 or 0.70. Using tetraethoxysilane as precursor and liquid crystals as templates, mesoporous silicas were prepared at different total concentrations of surfactants when molar fraction of CTAB was fixed at 0.70. Transmission electron microscopy results revealed that ordered mesoporous silicas with lamellar pore channels were prepared. Nitrogen adsorption-desorption determinations showed that these materials exhibited a pore size about 4.5 nm. In addition, the surface areas increased significantly with the increase of total surfactant concentrations. This work provided a simple and effective approach to synthesize lamellar mesoporous silicas.

A new approach to prepare mesoporous silica using coal fly ash

Even after decades of research, the preparation of mesoporous silica still depends on the sol–gel method. The major problem of sol–gel method is its infeasibility in industrial manufacturing. A large-scale preparation method is desired to meet the growing demand of mesoporous silica in multiple applications. A cost-effective and industrially feasible method was proposed to prepare mesoporous silica. The well-developed acid leaching technology was used as a novel pore forming method for treating coal fly ash. And mesoporous silica with specific surface area as high as 585.02m2/g and pore volume of 0.54cm3/g was successfully prepared under a control of reaction parameters. Reaction intensity was introduced as a new parameter to describe reaction conditions and help explain the variation of pore structure and shape prepared under different reaction conditions. This method is feasible in large-scale manufacturing of mesoporous silica and will satisfy the great demand for its wide applications.

Mesoporous Silica Coating on Rf-Sputtered Apatite/Titanium Substrate

The preparation of mesoporous silica coated rf-sputterd apatite / titanium substrate and protein adsorptive property is reported. Hydroxyapatite coated titanium implant has been used, and the adsorption of proteins onto implant is very important for bond formation between bone and implant. Mesoporous silica (MPS) materials have been extensively studied as carriers of bio-molecules due to their potential practical applications in medical materials. Pore diameters of 1.5 – 30 nm of the periodic mesoporous materials are close to the diameters of target molecules and high adsorbed amount of proteins onto MPS has been reported, and also enclosure of the protein in a well-defined space may help to prevent denaturation. Previously, we reported the MPS coating on the porous hydroxyapatite (HAp) ceramics obtained by dip-coating method, and by the vapor phase synthesis. Protein adsorption on the porous HAp with the MPS coatings was evaluated using UV-VIS spectrometry, and the quantity of adsorbed amount of protein was remarkably improved. In this study, the HAp deposition on Ti substrate (HAp/Ti) was carried out by rf magnetron sputtering and hydrothermal treatment, and MPS coating on HAp/Ti using LB deposition apparatus to improve the protein adsorptive property of HAp/Ti. The quantity of adsorbed protein onto the HAp /Ti was around 12 times high, and that onto the MPS/HAp/Ti was 18 times high compared to that on Ti substrate.

Optimization of tetracycline hydrochloride adsorption on amino modified SBA-15 using response surface methodology

Several researchers are focused on preparation of mesoporous silica as drug carriers with high loading efficiency to control or sustain the drug release. Carriers with highly loaded drug are utilized to minimize the time of drug intake. In this study, amino modified SBA-15 was synthesized through grafting with amino propyl triethoxy silane and then loaded with tetracycline hydrochloride. The drug loading was optimized by using the response surface method considering various factors including drug to silica ratio, operation time, and temperature. The drug to silica ratio indicated as the most influential factor on the drug loading yield. Further, a quadratic polynomial equation was developed to predict the loading percentage. The experimental results indicated reasonable agreement with the predicted values. The modified and drug loaded mesoporous particles were characterized by FT-IR, SEM, TEM, X-ray diffraction (XRD), elemental analysis and N2 adsorption–desorption. The release profiles of tetracycline-loaded particles were studied in different pH. Also, Higuchi equation was used to analyze the release profile of the drug and to evaluate the kinetic of drug release. The drug release rate followed the conventional Higuchi model that could be controlled by amino-functionalized SBA-15. Further, the drug delivery system based on amino modified SBA-15 exhibits novel features with an appropriate usage as an anti-bacterial drug delivery system with effective management of drug adsorption and release.

A facile approach for the tunable wormlike or ordered pore morphology of mesoporous silica: Effect of catalyst types and polyethylene glycol

Two different basic catalysts, NaOH and NH4OH, to the formation of mesoporous silica with completely different pore morphology at the same mole concentration with or without polyethylene glycol (PEG) were investigated. NaOH catalyzed system seemed to have a more ordered structure and larger particle size than NH4OH catalyzed system. The addition of PEG tended to promote the charge matching probability for silicate oligomers and micelles, which resulted in the more ordered pore morphology for NH4OH system. With increased ammonia concentrations, the pore morphology of disordered wormlike structure was transformed into ordered MCM-41 type mesoporous structure with particle dimension in a few tenths of nanometer to hundred nanometer. With the addition of PEG, at low ammonia concentration, the mesoporous pores became more orderly arranged as well. However, the effect of PEG on the pore and particle morphology of the NaOH catalyzed system was less evident than that of the NH4OH system. The catalyst types were also investigated at the same pH to contrast the significance of catalyst effect on the preparation of mesoporous silica, which was often neglected in the literature. NaOH catalyzed system still indicated a more ordered wormlike structure and slightly larger particle size than NH4OH catalyzed system. The XRD (X-ray diffraction) results and N2 adsorption–desorption isotherms were in agreement with the TEM (Transmission electron microscope) morphology. The significance of two different catalysts with the addition of PEG in tuning pore morphology was justified.

The Adsorption of Cytochrome C on Mesoporous Silica Coated Hydroxyapatite Ceramics in PBS Solution

The preparation of mesoporous silica coated hydroxyapatite (HAp) ceramics is reported. The adsorption of proteins onto hydroxyapatite (HAp) is important in a variety of oral or osseous biological events. HAp has been used as bone filler, and the protein adsorption onto HAp materials is of importance for the bond formation. HAp has been also used as the material for column packing of liquid chromatography to separate and refine proteins due to the adsorptive capabilities with respect to the HAp. Mesoporous silica (MPS) materials have been extensively studied as carriers of bio-molecules due to their potential practical applications in medical materials. Pore diameters of 1.5 30 nm of the periodic mesoporous materials are close to the diameters of target molecules and enclosure of the protein in a well-defined space may help to prevent denaturation. Previously, we reported the MPS coating on the porous hydroxyapatite (HAp) ceramics obtained by dip-coating method. Protein adsorption on the porous HAp with the MPS coatings was evaluated using UV-VIS spectrometry, and the quantity of BSA adsorbed onto the HAp ceramics with the MPS coatings is around 1.5 times high compared to that on porous HAp ceramics. In this study, the vapor-phase synthesis of MPS film on HAP ceramics was carried out to improve the protein adsorptive property of HAp ceramics. The quantity of adsorbed protein onto the HAp ceramic disc with MPS coatings is around 5 times high compared to that on HAp ceramic disc.