Pure SBA-15 Research Articles

Mesoporous Silica-Carbon Composites with Enhanced Conductivity: Analysis of Powder and Thin Film Forms.

The resistivity of the silica SBA-15 type can be significantly improved by forming a thin layer of carbon on the pore surface. This is possible through the carbonization reaction of a surfactant used as a structure-directing agent in the synthesis of mesostructured silica materials. The synthesis of this type of silica-carbon composite (SBA-C) is based on the use of sulfuric acid to create a carbon layer from surfactant molecules encapsulated in silica mesopores. The action of sulfuric acid takes place through dehydration and sulfonation reactions, which promote the formation of aromatic structures and favor crosslinking processes. The same procedure was applied to prepare MTF-C composites based on mesostructured thin films (MTFs). Compared to pure silica materials, these silica-carbon composites exhibit reduced pore diameter and volume while maintaining morphology and structure. The pore structure characteristics were obtained by scanning and transmission electron microscopy, X-ray energy dispersive spectroscopy, Raman spectroscopy, X-ray diffraction, thermogravimetry, and isothermal sorption analysis. The composite obtained after carbon layer formation exhibited enhanced conductivity in comparison to pure silica SBA-15. The resistivity of SBA-C composite material after annealing at 800 °C under a nitrogen atmosphere decreased to 1980 Ωcm in comparison with pure SBA-15.

Cu-trimesate and mesoporous silica composite as adsorbent showing enhanced CO2/CH4 and CO2/N2 selectivity for biogas and flue gas separation

Due to their diverse structure, high porosity, and tunable functionality, Metal-Organic Frameworks (MOFs) hold great potential as materials for diverse applications, including gas separation. Material science researchers are focusing on creating flexible materials that have special properties. Most of the latest research mainly concentrates on fabricating composite materials of MOFs and other functional materials. These MOF-based composites can mitigate the limitations of pure MOFs and may even perform better than the individual components. Here, we present a systematic study on the effect of solvent in synthesising a composite (Cu-BTC@SBA-15) of Cu-trimesate MOF (aka CuBTC) and ordered mesoporous silica SBA-15, showing considerable improvement in selectivity for CO2 adsorption from the flue gas and biogas. The pristine Cu-BTC, SBA-15 and the composites with different content of Cu-BTC were characterized by PXRD, BET, FT-IR, SEM, TEM and TGA techniques. The pure gas adsorption isotherms were measured for CO2, CH4, and N2 gases. Ideal Adsorbed Solution Theory (IAST) is used for the binary selectivity calculations for gas systems such as CO2/CH4 and CO2/N2 in the context of biogas and flue gas separation. The composite exhibited an increase in CO2/CH4 selectivity by 39 % compared to pure Cu-BTC and 85 % compared to pure SBA-15. For the CO2/N2 system, the composite showed 38 % higher selectivity than Cu-BTC. The work has significance in the design of effective MOF-based composites for CO2 separation. Our work might open up a new route to design multifunctional materials for worldwide applications through an adsorptive and or mixed matrix membrane route.

Low-Density Polyethylene-Based Novel Active Packaging Film for Food Shelf-Life Extension via Thyme-Oil Control Release from SBA-15 Nanocarrier.

The use of natural raw substances for food preservation could provide a great contribution to food waste reduction, circular economy enhancement, and green process application widening. Recent studies indicated that the use of porous materials as adsorbents for natural essential oils provided nanohybrids with excellent antioxidant and antimicrobial properties. Following this trend in this work, a thymol oil (TEO) rich SBA-15 nanohybrid was prepared and characterized physiochemically with various techniques. This TEO@SBA-15 nanohybrid, along with the pure SBA-15, was extruded with low-density polyethylene (LDPE) to develop novel active packaging films. Results indicated that TEO loading was higher than other porous materials reported recently, and the addition of both pure SBA-15 and TEO@SBA-15 to the LDPE increased the water/oxygen barrier. The film with the higher thyme-oil@SBA-15 nanohybrid content exhibited a slower release kinetic. The antioxidant activity of the final films ignited after 48 h, was in the range of 60-70%, and was almost constant for 7 days. Finally, all tests indicated a sufficient improvement by the addition of thyme-oil@SBA-15 nanohybrids in the pure LDPE matrix and the concentration of wt. 10% of such nanocarriers provided the optimum final LDPE/10TEO@SBE-15 active packaging film. This material could be a potential future product for active packaging applications.

Investigation of intermediates formation in the CO2 hydrogenation to methanol reaction over Ni5Ga3-ZrO2-SBA-15 materials prepared via ZrO2 atomic layer deposition

The production of methanol through CO2 hydrogenation holds great promise for efficient CO2 utilization. The development of catalysts that exclusively favor the formate route is desirable as this enhances methanol selectivity and avoids CO formation. Here, the synthesis of two groups of Ni5Ga3-ZrO2-SBA-15 based materials was studied through the atomic layer deposition (ALD) of ZrO2. The first group was prepared applying ZrO2 ALD over a Ni5Ga3/SBA-15 material and the second group was prepared doing ZrO2 ALD over a mesoporous silica, Santa Barbara Amorphous (SBA-15), followed by impregnation with Ni5Ga3. Some characterization techniques were employed to assess the effectiveness of the ZrO2 ALD on both groups. Interestingly, it was observed that ZrO2 deposition was less effective over the Ni5Ga3/SBA-15 sample compared to its deposition over pure SBA-15, and through XPS analysis was noticed that ZrO2 is probably covering part of the Ni5Ga3 alloys. Furthermore, in situ DRIFTS analysis was performed during reaction conditions and revealed that ZrO2 deposition facilitated the formation of formate and methoxy intermediates in both material groups. The increase in the ZrO2 ALD cycles increased the formate and methoxy bands and decreased CO-related bands. After 6 cycles, only the ZrSBANG_6 catalyst exclusively followed the formate route, as only formate and methoxy bands were present.

Ordered mesoporous silicas for potential applications in solid vaccine formulations

In an effort to develop efficient vaccine formulations, the use of ordered mesoporous silica (SBA-15) as an antigen carrier has been investigated. SBA-15 has required properties such as high surface area and pore volume, including narrow pore size distribution to protect antigens inside its matrix. This study aimed to examine the impact of solvent removal methods, specifically freeze-drying and evaporation on the intrinsic properties of an immunogenic complex. The immunogenic complexes, synthesized and incorporated with BSA, were characterized by various physicochemical techniques. Small Angle X-ray Scattering measurements revealed the characteristic reflections associated to pure SBA-15, indicating the preservation of the silica mesostructured following BSA incorporation and the formation of BSA aggregates within the macropore region. Nitrogen Adsorption Isotherm measurements demonstrated a decrease in surface area and pore volume for all samples, indicating that the BSA was incorporated into the SBA-15 matrix. Fluorescence spectroscopy evidenced that the tryptophan residues in BSA inside SBA-15 or in solution displayed similar spectra, showing the preservation of the aromatic residues’ environment. The Circular Dichroism spectra of BSA in both conditions suggest the preservation of its native secondary structure after the encapsulation process. The immunogenic analysis with the detection of anti-BSA IgG did not give any significant difference between the non-dried, freeze-dried or evaporated groups. However, all groups containing BSA and SBA-15 showed results almost three times higher than the groups with pure BSA (control group). These facts indicate that none of the BSA incorporation methods interfered with the immunogenicity of the complex. In particular, the freeze-dried process is regularly used in the pharmaceutical industry, therefore its adequacy to produce immunogenic complexes was proved Furthermore, the results showed that SBA-15 increased the immunogenic activity of BSA.

Preparation and characterization of vernolic acid methyl ester functionalized ordered mesoporous materials

ABSTRACT. Vernonia oil is a naturally epoxidized triglyceride oil extracted from the seed of Vernonia galamensis, a native plant in East Africa. After hydrolysis to vernolic acid (VA) and derivatization, vernolic acid methyl ester (VAME) is synthesized and used to functionalize ordered mesoporous materials (OMM). Al-MCM-41 with Si/Al ratio of 15, pure silica SBA-15 and periodic mesoporous organosilica (PMO) are employed as supports exploring the different surface properties. Following optimization of the VAME/OMM ratios, selected samples, i.e. those with 13% VAME, were impregnated with AgNO3 in NaBH4 to obtain Ag-nanoparticles. The final AgVAME-OMM potential catalysts were characterized by transmission electron microscopy, observing an efficient loading of Ag nanoparticles in pure silica SBA-15 with VAME with 500 m2 specific surface area and 6 nm pore size.
 
 KEY WORDS: Vernolic acid methyl ester, Vernonia oil, Functionalization, Ordered mesoporous materials, Catalysis
 
 Bull. Chem. Soc. Ethiop. 2023, 37(3), 689-702. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i3.12

Deep eutectic solvent functionalized mesoporous silica SBA-15 based mixed matrix polymeric membranes for mitigation of CO2 (Extended Version)

The carbon dioxide (CO2) separation can be enhanced by using modified materials like a deep eutectic solvent (DES) modified mesoporous silica SBA-15 in polymeric support i.e polysulfone via mixed matrix membranes (MMMs). The pure SBA-15 and DES are potential candidates for the CO2 capturing and their combination has not been reported yet. In this work, a fresh DES was synthesized by combining equal concentrations of Decanoic acid and choline chloride by mass. MMMs were fabricated by DES functionalized SBA-15 (DES-SBA) filler. The DES-SBA-based polymeric MMMs of different compositions, from 5% to 20% with the difference of five each, were developed and subjected to the gas permeation analysis to evaluate relative selectivities and permeabilities of membranes. The DES-SBA-based MMMs were characterized by SEM and FTIR to obtain distribution analysis of filler in the polymer matrix as well as the cross-sectional and surface morphology and the structural analysis of membranes, respectively. The gas permeation evaluations have been utilized to mixed and pure gas samples and the findings of selectivities for CO2/N2 and CO2/CH4 and permeabilities of synthesized MMMs are being reported. The performance of the MMMs has been enhanced via functionalization of SBA-15 by DES as compared to the neat polysulfone (PSF) based simple membrane.

SBA-15 Supported Benzimidazolium-based Ionic Liquids: Synthesis, Characterization, and Applications in the Fuel Desulfurization

SBA-15 supported benzimidazolium-based ionic liquid ([email protected][BzIm][Cl]) has been synthesized with immobilization of trimethoxysilane-modified 1-methylbenzimidazolium chloride ([BzIm][Cl]) onto synthesized SBA-15 silica support material. SBA-15 and [email protected][BzIm][Cl] were characterized using FTIR, SEM, TEM, EDS, SAXS, BET, and NMR spectroscopy. The variation was found in the morphology as well as structure of [email protected][BzIm][Cl] with variation in the content of [BzIm][Cl]. The application of synthesized SBA-15 supported [BzIm][Cl] was studied for the removal of sulfur compounds from model fuel and real gasoline samples. It was found that in contrast to pure SBA-15, supported ionic liquids (SILs) showed higher efficiency for the adsorption of different sulfur-containing aromatic heterocyclic compounds from model fuel. Similarly, SIL having large IL content was found more efficient in the removal of sulfurous compounds from model and real gasoline samples in comparison to SIL having lesser IL content. Moreover, the adsorbents were reused 10 times without any significant loss in adsorption efficiency.

Porous polymer-in-silica hybrid electrolyte for all-solid-state Li-ion battery applications

Porous hybrid electrolytes based on Poly(Ethylene Glycol) (PEG) and mesoporous silica (SBA-15) were prepared by a post-synthetic modification of the silica matrix. The complex composed of the lithium salt (LiTFSI) and PEG is embedded in the silica pores, which offers mechanical properties for the hybrid electrolyte. The textural properties and composition of pure SBA-15 and the hybrid materials were characterized by several techniques. It was evidenced that the inner pores of the inorganic matrix (hexagonally packed cylindrical mesochannels) surface were uniformly coated with the complex PEG-LiTFSI and that the hybrid materials remained slightly mesoporous after the post-synthetic modification. To study the ionic conductivity, the hybrid powders were shaped as a pellet having both inter- and intraparticle porosity. The parameters whose influence were addressed are: the filling of the inter- and intraparticle porosity with PEG-LiTFSI complex, the lithium ion concentration and the PEG molecular weight. First, filling the interparticle porosity is necessary to the formation of continuous lithium conducting pathways while the intraparticle conductivity appeared to be mandatory to improve the overall conductivity. The hybrid of SBA-15 with PEG having a molecular weight of 600 gmol-1 gives the highest conductivity (1.6 x 10−6 S cm−1 at 30 °C) when used with the optimum molar ratio nEO/nLi of 10 found in this study. Preliminary analysis showed that the conductivity is governed by the segmental dynamics of the polymer chains (VTF model) in the whole temperature range. Finally, this material has an electrochemical window compatible with classical Li ion batteries cathode materials.

A detailed surface characterization study of SBA-15 and B-SBA-15-x mesoporous materials using the IGC technique

Pure and boron-containing B-SBA-15-x (molar ratio, Si/B = 50, 30, 10) mesoporous materials were synthesized by a direct hydrothermal procedure. Samples were characterized by XRD, ICP-OES, FT-IR, BET and SEM. Inverse gas chromatography (IGC) technique was used to determine the dispersive surface energies (γSd), adsorption thermodynamic parameters (ΔH, ΔG, ΔS) and the acid-base constants (KA and KD) of the samples. IGC experiments were performed at infinite dilution region at 200, 210, 220 and 230 °C. The surface characterization results confirmed that the SBA-15 structure was formed, boron was added to the structure and all samples have meso pores. The surface area of the pure SBA-15 was determined as 745.288 m2/g and it was found that the surface area decreases with increasing boron content. Physical adsorption occurred between the IGC probe molecules and all SBA-15 materials according to the adsorption thermodynamic parameters. (γSd) values of pure SBA-15, B-SBA-15-50, B-SBA-15-30 and B-SBA-15-10 were found at 40.873, 37.039, 36.636 and 37.444 mJ/m2 at 200 °C, respectively. It has been observed that the dispersive surface energy of all samples decreases with increasing temperature. According to the SC value calculated from the KA and KD parameters, the surface of B-SBA-15-10 with the highest boron content was found to be acidic. On the other hand the surfaces of all other samples were determined as basic.

Simultaneous monitoring of the photocatalytic degradation process of trifluralin and pendimethalin herbicides by SBA-15/TiO2 nanocomposite

Today, The occurrence of herbicides in environments attitudes a potential hazard to aquatic life and displays development forbidding of human embryonic cells, therefore their elimination from the environment is a vigorous job. In this paper, the SBA-15/TiO2 nanocomposite were synthesized utilizing amorphous nanosilica, which was extracted from stem cane ash (SCA) with 92.56% purity. FESEM and TEM images of pure SBA-15 and SBA-15/TiO2 nanocomposite demonstrates which their mean particle size was under 50 nm. The average particles size of TiO2 anatase calculated to be 27.6 nm using the Scherrer’s equation. The BET surface area, total pore volume and average pore diameter of the SBA-15/TiO2 was obtained to be 279.2 m2 g−1, 0.39 cm3 g−1 and 5.64 nm, respectively. For the first time, this nanocomposite was used as photocatalysts for degradation of trifluralin (Tri) and pendimethalin (Pen) herbicides in the aqueous solution. Partial least squares-1 (PLS-1) regression was used for simultaneous measurement of them in aqueous solutions before and after photocatalytic degradation with SBA-15/TiO2 nanocomposite. The values of some parameters such as R2(0.9951, 0.9872), recovery (101.5, 102.0%) and root mean square error of prediction (0.231, 0.239) for both Tri and Pen were attained by the PLS-1 regression, respectively. The influence of some operational parameters such as initial herbicide concentrations, photocatalyst dosage, irradiation time and pH were also investigated on the photocatalytic performance using the response surface methodology. Conferring to the ANOVA test, the most important factor on the decomposition of herbicides was photocatalyst dosage. The results displayed that the maximum elimination efficiencies under the optimum conditions (pH = 10, photocatalyst dosage 0.2 g L−1, irradiation time 30 min and initial herbicide concentration 60 mg L−1) from the river water for Tri and Pen were attained to be 90% and 82.5%, respectively.

Using contact angle measurement technique for determination of the surface free energy of B-SBA-15-x materials

Pure and boron-containing, Santa Barbara Amorphous (SBA-15) mesoporous materials and B-SBA-15-x (x is molar ratio of Si/B = 50, 30, 10), were synthesized via a direct hydrothermal method. Samples were characterized by XRD, BJH pore size distribution and SEM techniques. A contact angle technique was used to determine surface free energy and its dispersive and polar components. For this purpose, ethylene glycol (EG), di-iodomethane (DIM), formamide (FA) and water were used as model liquids to detect the contact angles. The OWRK/Fowkes approach was used to calculate the surface free energy values. Total surface free energy (γS) values of pure SBA-15 and B-SBA-15-50, B-SBA-15-30, B-SBA-15-10 were calculated as 64.365, 63.545, 63.490 and 64.218 mJ/m2 at room temperature, respectively. The main results of the study can be summarized as follows: (i) The contact angle measurement technique is suitable for determining the total surface free energy (γS) and its dispersive and polar components (γSd and γSp, respectively) of SBA-15 mesoporous materials and (ii) Addition of boron did not have a significant impact on the characteristic structure of SBA-15.

Ag modification of SBA-15 and MCM-41 mesoporous materials as sorbents of thiophene

Zeolites and some mesoporous materials modified by Ag possess excellent desulfurization performances toward the adsorption of thiophenic compounds. However, Ag in Ag-based sorbents has different forms, and the interactions between different forms of silver and thiophene still require further studies. In this paper, pure silica SBA-15 and MCM-41 mesoporous materials with weak acidity were loaded with Ag from the silver ammonia solution to form Ag/SBA-15 and Ag/MCM-41 sorbents. By comparing the desulfurization efficiencies of the sorbents in the simulated solution of thiophene-cyclohexane, thiophene-benzene, tetrahydrothiophene-cyclohexane and tetrahydrothiophene-benzene, it is found that the adsorption of sorbent for thiophene was accompanied by S-Ag and π complexation, and the adsorption performances of thiophene by the sorbents were greatly affected by benzene. The XPS results show that most Ag in Ag/SBA-15 and Ag/MCM-41 sorbents was metallic Ag, and some Ag strongly interacting with the carrier led to the formation of Ag-O-Si bonds as the main active center of thiophenic compounds. In addition, the sulfur atomic mulliken charges (e-) of different thiopheic compounds (thiophene, tetrahydrothiophene, methylthiophene) will affect the interactions between active components Ag and thiophene sulfur compounds. The desulfurization efficiencies of the sorbents in thiophene-cyclohexane, 2-methylthiophene-cyclohexane, and 3-methylthiophene-cyclohexane showed that the decrease in mulliken charges (e-) of sulfur atoms facilitated the S-Ag bond interaction between the sulfur atom of thiophenic compounds and active component in the sorbent. In conclusion, to obtain the Ag-based sorbent with good adsorption performance for thiophenic compounds, the carrier should contain a certain content of silicon hydroxyl and the suitable pore structure. During the preparation of SBA-15 and MCM-41 mesoporous materials modified by Ag, the Ag-O-Si bonds are more easily formed when silver ammonia interacts with the silicon hydroxyl group on the surface of the carrier. The suitable pore size can inhibit agglomerate to form metallic Ag during the calcination process. These conclusions will provide theoretical guidance for the preparation of silver-based sorbents for thiophene.

Recent developments in metal-doped SBA-15 catalysts for heterogeneous catalysis and sustainable chemistry

The development of new advanced sustainable materials for heterogeneous catalysis requires control of the structural parameters of the active sites. Mesoporous silica, especially SBA-15, has some unique and important features such as highly ordered mesopores, greater hydrothermal stability, greater wall thickness, large surface area, and adjustable pore volume. All these properties render it a promising material for catalysis, adsorption, supporting materials, biomedical applications, and environmental remediation. However, pure SBA-15 lacks acidic characteristics, which hinders its catalytic activity. Therefore, the functionalized SBA-15 improves the catalytic activity for versatile applications. Thus, in this study, we attempted to summarize the synthesis procedures, various functionalization processes, and application of metal-modified SBA-15 in organic synthesis, fine chemical synthesis, photocatalysis, and decontamination of water. Furthermore, the physicochemical properties, sustainability, and efficacy are discussed in detail for future reference and scope of studies.

Phosphoric acid doped polybenzimidazole based polymer electrolyte membrane and functionalized SBA-15 mesoporous for elevated temperature fuel cell

Polymer electrolyte membrane as heart of a Fuel Cell electrochemical system to improve the durability of Fuel Cell performance at elevated temperatures requires the highest stability of proton conductivity, and thermal and chemical stability in long-term operations. In this research, the effect of SBA-15 mesoporous on the properties of H3PO4 doped polybenzimidazole/ionic liquid membranes were investigated for Fuel Cell applications under elevated temperatures. The H3PO4 doped polybenzimidazole based membranes were successfully fabricated by using polybenzimidazole (PBI) polymer with the same molecular weight and different amounts of 1,6-di (3-methylimidazolium) hexane dibromide dicationic ionic liquid (Mim2+ Br2− DIL), pure SBA-15 mesoporous and functionalized SBA-15 mesoporous with polyamidoamine groups (PAMAM mesoporous).The H3PO4 doped composite membrane containing 7% w/w Mim2+ Br2− DIL and 2% w/w PAMAM mesoporous with a superior mechanical strength and high thermal and chemical stability indicate a best electrochemical performance at 180 °C and 0.50 V under anhydrous conditions. The high proton conductivity stability of the composite membranes under elevated temperature and high humidity indicates that the introduction of PAMAM mesoporous with the NH2, NH and CO groups on the inner wall of its pores significantly improves the ability to retain of Mim2+ Br2− DIL and H3PO4. The results imply that use of PAMAM mesoporous as Mim2+ Br2− DIL and H3PO4 protectors against their leaching from the composite membrane is a new strategy to improve the stability of elevated temperature Fuel Cells performance in long-term operation.

Pyrolysis-catalysis for waste polyolefin conversion into low aromatic naphtha

The global waste plastic crisis, caused by overconsumption of single-use plastics, is threatening ecological systems and public health, worldwide. This study presents a novel catalytic conversion of waste polyolefinic plastics to low aromatic naphtha for new plastic manufacturing by a tandem catalysis process. Zn/SBA-15 was found to be an effective heterogeneous catalyst for cracking high density polyethylene (HDPE) pyrolytic wax into short chain olefins. This catalyst shows a much higher activity than pure catalysts or SBA-15 catalysts that were modified with other metals. This tandem catalysis system was also applicable to catalytic reforming of various waste polyolefins including HDPE, low density polyethylene (LDPE), and polypropylene (PP), producing high quality naphtha with a C5-C12 paraffin selectivity of 50–71 % peak area. Furthermore, the pure and real-world plastic mixture can also be used to produce high quality naphtha, with a C5-C12 paraffin selectivity of 60.39 % peak area and 57.16 % peak area, respectively. This new plastic to low-aromatic naphtha technology highlights the feasibility of upcycling waste plastics into virgin plastic products.

Adsorption behavior of cationic dye on mesoporous silica SBA-15 carried by calcium alginate beads: Experimental and molecular dynamics study

This paper describes the fabrication of composites beads based on functionalized SBA-15 materials encapsulated in calcium alginate (ALG) which are employed for removing methylene blue (MB). The prepared composites beads were characterized by various techniques such as XRD, FTIR, SEM, zeta potential measurements and TGA. As results, the SBA-15 material was well immobilized in the alginate matrix. The best adsorbent beads were determined by evaluating the kinetics of MB adsorption from aqueous solutions. It has also been established that the hydrogel beads with a pure SBA-15 have a negative surface and therefore a greater capacity for adsorption of cationic dye compared to the adsorbents beads containing amine-functionalized SBA-15. The combination of two matrices (Pure SBA-15 and alginate) containing negatively charged surfaces generates excellent properties through the removal of the MB dye. The maximum adsorption capacity of the ALG-SBA-15 composite was 333.33 mg.g−1. The adsorption well followed the pseudo-second-order kinetics and Langmuir isotherm, and was spontaneous endothermic process. The adsorption of MB dye on the ALG-SBA-15 beads could be easily realized through electrostatic interactions and hydrogen bonding. Furthermore, molecular dynamic (MD) simulations were performed on pure SBA-15 structure models with different pore diameters to get a glimpse on the dynamic behavior of MB molecules upon adsorption on the mesoporous material.

Al-functionalized mesoporous SBA-15 with enhanced acidity for hydroisomerization of n-octane

SBA-15, possessing uniform mesopore system and large specific surface area, shows a tremendous mass transfer advantage in the reactions involving reactant, intermediate or product whose dynamic diameter is larger than the pore size of microporous zeolites, but the low acidity greatly limits its application in acid-catalyzed reactions (e.g., hydroisomerization). Herein, we report an Al-functionalized SBA-15 molecular sieve (Al-SBA-15) with enhanced acidity obtained via a pH-adjusted prehydrolysis synthesis approach for hydroisomerization. Its physicochemical properties and catalytic performance were carefully characterized, evaluated in hydroisomerization of n-octane after loading active component Pt, and compared with a pure silica SBA-15 and two Al-containing samples (AlSBA-15 and Al/SBA-15) produced through direct synthesis and wetness impregnation, respectively. The results show that the acidity of three Al-functionalized samples is prominently improved, and thus the conversion of n-octane over them is greatly increased when compared with siliceous SBA-15. Moreover, among three Al-containing SBA-15 materials, Al-SBA-15 with the largest pore diameter and moderate acidity exhibits relatively high n-octane conversion and di-branched isomers selectivity but minimal cracking selectivity. These results demonstrate that pH-adjusted prehydrolysis is an effective route to preparing Al-functionalized SBA-15 with suitable acidity for the hydroisomerization of alkanes.

New bi-functionalized ordered mesoporous material as heterogeneous catalyst for production of 5-hydroxymethylfurfural

Newly designed ordered two dimensional hexagonal bi-functionalized mesoporous organosilica material (b-MPOS) has been synthesized through the step-by-step post-grafting synthetic pathway. The pure calcined SBA-15 was subjected for functionalization using chloro-substituted organo-silica ligand to get MPCFOS, denoted by mesoporous chloro-functionalized organosilica material. This material undergoes through the substitution reaction (SN2) between the pore wall attached chloro-functional group and the organic bi-functionalized ligand i.e. 3-Amino-1,2,4-triazole-5-carboxylic acid containing amine group in the presence of potassium carbonate which was used as a mild base under the refluxing conditions. The as-synthesized bi-functionalized material displays the high specific surface area as well as pore diameter of 537 m2 g−1 and 9.4 nm, respectively. Since, as-synthesized material contains both acid and basic functional groups, temperature programmed desorption (TPD) of NH3 and CO2 analysis, have been performed to determine the total amount of surface acidic and basic sites of this material which are estimated to be 1.87 and 2.07 mmol g−1, respectively. Due to the presence of Brønsted acid and base groups together with the bi-functionalized material, it has been investigated as a heterogeneous catalyst for carbohydrates transformation to synthesize the valuable chemical like 5-hydroxymethylfurfural (HMF) from fructose with the high product yield of 86 mol% by using microwave irradiated heating conditions.

Carbamate-Isocyanurate-Bridged Periodic Mesoporous Organosilica for van der Waals CO2 Capture.

We synthesized a new organosiloxane bridge on the basis of an isocyanurate derivative through a simple melt-fusion approach by the reaction of 3-isocyanatopropyltriethoxysilane (IPTES) with 1,3,5-tris(2-hydroxyethyl)-1,3,5-triazinane-2,4,6(1H,3H,5H)-trione (THEIC). The obtained carbamate-isocyanurate-based organosiloxane bridge precursor was used for the preparation of chemo- and thermostable periodic mesoporous organosilica (PMO-THEIC) on condensation with tetrathoxysilane silicon precursor through a soft-template approach. Furthermore, the synthesized PMO-THEIC with unique surface functionality was investigated for CO2 capture. The results show that the PMO-THEIC has higher activity than pure SBA-15 for CO2 capture due to the high affinity of carbamate functionalities embedded within the pore walls toward CO2 molecules. The affinity of organosiloxane bridge for CO2 molecules is mainly facilitated via the van der Waals force with carbamate functional groups rather than the isocyanurate ring, according to the density functional calculations.