Molecular Sieve SBA-15 Research Articles

The application of FTIR in situ spectroscopy combined with methanol adsorption to the study of mesoporous sieve SBA-15 with cerium-zirconium oxides modified with gold and copper species

The molecular sieves SBA-15 with ceria, zirconia and mixed cerium-zirconium oxides were synthesized and used as supports for gold and copper species. The materials were characterised using a FTIR in situ spectroscopy combined with the adsorption of methanol and oxygen as probe molecules, which allowed the monitoring of the changes on the surface, in particular the creation of the intermediates species on the active sites of materials. The presence of interactions between gold and copper in bimetallic catalysts was considered during the reaction of methanol oxidation. The goal of this work was studied the changes of intermediates adsorbed on the surface of catalysts during the oxidation of methanol after treatment at selected temperature. The monometallic gold and the bimetallic copper–gold catalysts were tested in the reaction of methanol oxidation in the gas phase in situ.

Affinity purification of angiotensin-converting enzyme inhibitory peptides from Volutharpa ampullacea perryi protein hydrolysate using Zn-SBA-15 immobilized ACE

In this study, a new affinity medium of Zn-SBA-15-immobilized ACE was prepared and applied in the separation of ACE inhibitor peptides from Volutharpa ampullacea perryi protein hydrolysate. Molecular sieve SBA-15 for immobilizing ACE was prepared by hydrothermal crystallization method. Zn2+ was directly adsorbed by SBA-15 to form Zn-SBA-15. ACE was immobilized on Zn-SBA-15 by affinity adsorption. ACE inhibitory peptides were separated by affinity chromatography based on the specific binding force between immobilized ACE and its inhibitors. The bound peptides were released by 2 M NaCl and further purified by reverse-phase high-performance liquid chromatography. Then the amino acid sequence of two peptides with ACE inhibitory activity was identified by MS/MS. Two new ACE inhibitory peptides Ile-Val-Thr-Asn-Trp-Asp-Asp-Met-Glu-Lys (IC50 = 2.08 mM)) and Val-Gly-Pro-Ala-Gly-Arg-Pro-Gly (IC50 = 4.66 mM) were purified from Volutharpa ampullacea perryi protein hydrolysate. The study suggest that the two peptides separated from the Volutharpa ampullacea perryi protein hydrolysate were potent ACE inhibitors and may be used to decrease blood pressure. The significance of the research is to prepare a new affinity medium of Zn-SBA-15 immobilized ACE and apply it in separation of ACE inhibitory peptides from Volutharpa ampullacea perryi protein hydrolysate, which can also provide an effective means to separate the peptides with ACE inhibitory activities from other food sources. It can promote the research and development of antihypertensive active substances.

Mesoporous molecular sieves containing niobium(V) as catalysts for the epoxidation of fatty acid methyl esters and rapeseed oil

Niobium-containing mesoporous silica (Nb–SiO2) catalysts, which showed previously promising performances in the liquid-phase epoxidation of alkenes, were here applied to the epoxidation of unsaturated fatty acid methyl esters (FAMEs), selectively hydrogenated FAMEs and rapeseed oil triglyceride with aqueous hydrogen peroxide. Niobium-silica solids were prepared via grafting of niobocene dichloride onto the surface of different porous silica-based supports (non-ordered SiO2, ordered mesoporous MCM-41 and SBA-15 molecular sieves) via a dry impregnation procedure. Promising performance with very good selectivity towards desired monoepoxides were obtained, in particular over a Nb-grafted silica catalyst prepared from a commercial non-ordered silica support.

Al-Rich Ordered Mesoporous Silica SBA-15 Materials: Synthesis, Surface Characterization and Acid Properties

Al–SBA-15 is an interesting mesoporous material having highly ordered nanopores and a large surface area, which is widely employed as catalysts and adsorbents, but relatively few studies on the surfaces properties of this type of materials have been carried out. The purpose of the present work was to advance knowledge on the textural properties of Al–SBA-15 by applying the accurate NLDFT method as well as to gain insight into the surface characterisation and acidic trend of this material. Mesoporous Al–SBA-15 molecular sieves, in three SiO2/Al2O3 ratios: 50, 75 and 100 were accomplished by post-synthesis alumination in aqueous solution of a purely siliceous SBA-15 material. The obtained solids were characterized using powder X-ray diffraction (XRD), X-ray fluorescence (XRF), N2 adsorption–desorption (BET/DFT), transmission electron microscopy (TEM), water adsorption and zeta potential measurements. The results indicate that Al atoms have been successfully incorporated into the framework of the hexagonal mesoporous SBA-15. The aluminum introduced amount has remarkably affected the surface properties of the SBA-15 solid, indeed microporosity decreased. Furthermore, the esterification test showed that the Al–SBA-15 material exhibit Bronsted acid properties with an interesting activity leading to yields of ~90% of biodiesel.

Hydrothermal Stability of Molecular Sieves SBA-15 Research

Hydrothermal Stability of Molecular Sieves SBA-15 was studied. It was characterized by N2 adsorption, X-ray diffraction and FT-IR analysis. The results indicated that water, heat and alkaline environments are acidic center caused some of the molecular sieve SBA-15, the influence of the structure of the SBA- 15 mesoporous molecular sieves have some damage, led to the decrease of the pore diameter, specific surface area. This is because the thermal stability of mesoporous molecular sieve is closely related to the silicon hydroxyl condensation. Due to the contraction of silicon hydroxyl, generated the Si-O-Si unit structure, causes the d100. Moderate Si-OH condensation can increase the stability of mesoporous structure, and excessive Si-fuelled by condensation of Ozzie and Harriet channel by Si-O keys tensile force, spacing gradually reduced resulting in progressive collapse of mesoporous structure.

Metathesis of 2-pentene over Mo and W supported mesoporous molecular sieves MCM-41 and SBA-15

Abstract Molybdenum and tungsten oxides were supported on silica, MCM-22, MCM-41 and SBA-15. XRD and N2 adsorption–desorption revealed that architecture and textural character of supports were preserved. The catalysts were investigated in transformation of 2-pentene at different reaction temperatures. MoO3/MCM-22 exhibited highest conversions with isomerization and cracking as major reactions. MoO2(acac)2, MoO3 and WO3 supported on MCM-41 and SBA-15 showed metathesis reaction of 2-C5= producing propylene, C4= and C6+=as major products. Catalysts based on MCM-41 exhibited higher activity and stability than SBA-15. Addition of ethylene to 2-C5= increased selectivity to propylene due to metathesis of ethylene with 2-pentene.

Carbothermal synthesis of porous silicon carbide using mesoporous silicas

Samples of crystal modifications of porous silicon carbide were obtained by carbothermal method using carbon precursors (sucrose, carbon) and aerosil or mesoporous silicas molecular sieves SBA-3, SBA-15, KIT-6, and MCF as silicon sources. Porous β-SiC samples obtained from carbon–silica composites are characterized by high structural and sorption characteristics (SBET up to 410 m2/g, Vpore up to 1.0 cm3/g). High hydrogen adsorption capacity of silicon carbide samples based on KIT-6 (up to 1.24 wt% at 77 K and 1 atm.), considering low adsorption energy (\( \left| {\Delta \mu_{0} } \right|_{{{\text{H}}_{2} }} \)) up to 2.3 kJ/mol for SiC vs. ca. 5.0 kJ/mol for carbon), was determined. The highest ever reported value among the existing porous materials was observed for specific adsorption of H2 by SiC (specific adsorption on the pore surface, ρ up to 15 μmol/m2) corresponding to almost complete filling of the surface with hydrogen in the examined conditions (77 K, 1 atm.).

Facile immobilization of nitrile hydratase in SBA-15 via a biomimetic coating

Dopamine functionalized mesoporous molecular sieve SBA-15 (Dop-SBA-15), synthesized by a simple and cost-effective method, was developed as a matrix to immobilize NHase (NHase@Dop-SBA-15). Various characterization techniques such as SEM, TEM, BET and FT-IR were carried out to investigate the properties of Dop-SBA-15 and NHase@Dop-SBA-15. It was shown that the Dop-SBA-15 had highly ordered mesopores and large surface area of 447 m2/g. The activity, thermal stability, pH stability, storage stability, and reusability of NHase@Dop-SBA-15 were studied in detail. It was observed that the performance of NHase@Dop-SBA-15 was improved significantly compared to that of the free NHase and NHase immobilized in unfunctionalized SBA-15. This study provided insight into the preparation of Dop-SBA-15 and its application for NHase immobilization.

Synthesis and Characterization of Co/SBA-15 Catalysts

The mesoporous silica SBA-15 molecular sieve has been widely studied due to its unidirectional mesoporous structure, its high average pore diameter, its high thermal and hydrothermal stability and its ability to absorb metal ions, allowing its use as support material for catalysts. This study aimed to synthesize the Co/SBA-15 catalyst, and characterize it through the techniques of X-ray diffraction, temperature programmed reduction (TPR) and scanning electron microscopy (SEM). The SBA-15 support was synthesized from the following molar composition of reaction mixture: 1TEOS: 0.017 P123: 5.7 HCl: 173 H2O: 40 EtOH, and after calcined at 550 °C for 6 hours. The Co/SBA-15 catalyst was prepared by incorporating 10% cobalt by wet impregnation. Through the X-ray diffractograms, it was found that the impregnation has not changed the structure of the material. RTP profiles showed the presence of peaks at different temperatures that may be caused by dispersion of the cobalt.

Covalent grafting of cobalt carbonyl cluster on functionalized mesoporous SBA- 15 molecular sieve and its applications towards hydroformylation of 1-octene

Cobalt carbonyl cluster was anchored through a facile route on the surface of organo-functionalized SBA-15 molecular sieve by post-synthetic approach. The successful grafting of organofunctional ligand and cobalt carbonyl cluster was evident thorough 29Si-MAS NMR, 13C-MAS NMR and FT-IR studies. The resultant cobalt clusters anchored functionalized SBA-15 material (SBA-15-RCo) showed promising catalytic activity on hydroformylation of 1-octene (97% conversion) with excellent selective towards hydroformylated products (90%).

Anatase TiO2 nanocrystals anchored at inside of SBA-15 mesopores and their optical behavior

In this paper, a new synthesis method was proposed to obtain anatase titanium oxide (TiO2) nanocrystals anchored into SBA-15 molecular sieve, as a matrix assigned by the in-situ anchoring (ISA) method. Pure SBA-15 and modified with TiO2 nanocrystals at different Si/Ti molar ratios (R=75, 50, and 25) were structurally characterized by X-ray diffraction (XRD), Micro-Raman and Fourier Transform infrared (FTIR) spectroscopies. Specific surface area, pore volume and average pore diameter were estimated using both Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods, respectively. Morphological aspects of these samples were observed by means of field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Optical properties were investigated by ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. XRD patterns, Micro-Raman and FT-IR spectra indicate the TiO2 nanocrystals crystallized in a tetragonal structure anchored into the SBA-15 mesopores. BET and BJH methods prove a large amount of TiO2 nanocrystals were anchored inside of SBA-15 mesopores due to increase in surface area and average pore size of SBA-15 matrix. FE-SEM and TEM images showed the pure SBA-15 has an elongated hexagon-shaped microstructure, and an average size of 7.34nm for 2D hexagonal mesopores. Moreover, ISA method was able to avoid blocking of mesopores, in addition promotes a significant increasing the impregnation rate of anatase TiO2 nanocrystals in SBA-15 matrix. A growth mechanism was proposed in order to explain the stages involved in the formation of TiO2-SBA mesoporous. UV–vis spectra revealed a dependence of the optical band gap energy (Egap) with the decreasing of Si/Ti molar ratios.

Synthesis and characterization of SBA-15 in presence of Zn (II) tetraphenylporphyrin and study of its luminescent property

ABSTRACTThe metalloporphyrin Zn (II) tetraphenylporphyrin was incorporated into mesoporous molecular sieves SBA-15 by the interaction of the π electrons of the metalloporphyrin with the superficial hydroxyl groups of the SBA-15. The resultant material confirmed that the channels of SBA-15 have been filled with the metalloporphyrins by means of XRD, TEM, solid UV/Vis, FT-IR, nitrogen adsorption, and TGA. Luminescent properties were studied by solid fluorescence emission and excitation spectra. Results indicate that luminescent property of SBA-15/metalloporphyrin is better than that of the pure metalloporphyrin.

Low-Cost Preparation of SBA-15 Silica Molecular Sieve and High Humidity Sensing Property in a Wide Range of Relative Humidity

In this paper, different SBA-15 molecular sieves were prepared in a facile sol-gel method by using a low-cost sodium silicate as silicon source at different ripening temperature. The materials were characterized by small-angle XRD, TEM, nitrogen adsorption–desorption test. The results showed that ripening temperature can affect the pore size and mesostructure of SBA-15. High surface area SBA-15 can be obtained at low ripening temperature, and plugged mesostructure can be prepared at high temperature. The gravimetric humidity sensing property of the materials were tested based on a transducer of quartz crystal microbalance. The test results revealed that all the samples showed high response in the wide range of relative humidity. The sensors based on that prepared at 35°C show a good stability and linearity in the range of 11.3%RH to 98%RRH along with fast response (12s) and recovery time (8s), ultrahigh sensitivity and low hysteresis, implying that has a great potential for humidity detection.

Highly ordered mesoporous spinel ZnCo2O4 as a high-performance anode material for lithium-ion batteries

Highly-ordered mesoporous spinel ZnCo2O4 (HOM-ZnCo2O4) with controlled morphology, high surface area and narrow pore size distribution is prepared through a facile infiltration route with molecular sieve SBA-15 as templates for the first time. At the same time, nanostructured porous spherical spinel ZnCo2O4 (NPS-ZnCo2O4) framework is also synthesized using silicon spheres as templates. HOM-ZnCo2O4 is revealed to have a highly ordered mesoporous structure with a pore diameter of ∼4nm and a high surface area of 112.0m2g−1, while NPS-ZnCo2O4 is a framework containing 3D connected pores with a diameter of ∼100nm and surface area of 88.4m2g−1. As the anode material, HOM-ZnCo2O4 displays a high reversible specific capacity up to 1623mAhg−1, ∼300mAhg−1 larger than NPS-ZnCo2O4 (1286mAhg−1), at a current density of 2.0 Ag−1. When applying a high current density of 8.0Ag−1, the capacity of HOM-ZnCo2O4 still remains at a high level of 1470mAhg−1, but NPS-ZnCo2O4 undergoes a severe degradation to 751mAhg−1. The large specific surface area contributes much to the better rate performance of the former because it provides a larger cross section for Li+ flux. Also, the small pore size may be more in favor of maintaining the structural stability of porous spinel material than the large one. Aside from its nanostructured characteristics, an inner atomic synergistic effect within the cubic lattices may account for the superior electrochemical performance of HOM-ZnCo2O4. HOM-ZnCo2O4 that exhibits high capacities and well stability is a kind of competitive anode materials and highly-ordered mesoporous structure is superior in electrode design.

Dielectric studies of ferroelectric NH4HSO4 nanoparticles embedded into porous matrices

ABSTRACTDielectric studies were carried out for the ammonium hydrogen sulphate, NH4HSO4, nanopartiles confined to three different mesoporous silica matrices: opal (photonic crystal), porous glass (mean pore size of 7 nm), and SBA-15 molecular sieves (pore size of 7.5 nm). Measurements were made within a temperature range 100 to 300 K which covers two structural phase transitions bounded the intermediate ferroelectric phase. The temperature of the upper second order phase transition was found not to shift compared to that in bulk. The lower phase transition shifted compared to bulk leading to the expansion of the ferroelectric phase. The transition temperature reduction, diffusion of transitions, and width of the thermal hysteresis differed for different nanocomposites and did not correlate to the pore size. The experimental data were treated within the framework of the models developed for isolated small ferroelectric particles and arrays of coupled particles. The rise of the space charge polarization effects was also observed.

Amine-modified SBA-15 and MCF mesoporous molecular sieves as promising sorbents for natural antioxidant. Modeling of caffeic acid adsorption

This work presents a detailed study of caffeic acid adsorption on mesoporous SBA-15 and MCF silicas functionalized with (3-aminopropyl)triethoxysilane (APTES) and 3-[2-(aminoethylamino)propyl]trimethoxysilane (AEAPTMS). Synthesized mesoporous adsorbents were characterized using different analytical techniques such as N2 sorption, XRD, TEM, SEM and FT-IR. The adsorption studies of caffeic acid were conducted in various organic solvents. Moreover, the effect of water content in 2-propanol–water mixture on adsorption efficiency was investigated. The experimental data were best fitted to the Langmuir equation, followed by the Temkin, Dubinin–Radushkevich and Freundlich models. The maximum adsorption capacity values calculated from the Langmuir model demonstrated that SBA-15 and MCF silicas modified with AEAPTMS revealed better adsorption properties toward caffeic acid (192.3 and 161.3mg/g, respectively) as compared to the materials modified with APTES (125.0 and 113.6mg/g, respectively). The obtained results indicate that both SBA-15 and MCF silicas functionalized with AEAPTMS and APTES are promising materials for the entrapment of caffeic acid.

Ru complexes of Hoveyda-Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions.

Hoveyda–Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36) and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (<1% of Ru content). XPS analysis revealed that during immobilization ion exchange between Hoveyda–Grubbs type catalyst and zeolitic support occurred in the case of Cl− counter anion; in contrast, PF6− counter anion underwent partial decomposition.

Textural analysis of SBA-15 molecular sieve using ethanol as co-solvent

The SBA-15 molecular sieve has been widely studied due to its unidirectional mesoporous structure, high average pore diameter and high thermal and hydrothermal stability. This study aimed to evaluate the effect of ethanol co-solvent in the texture of SBA-15 molecular sieve, performing the synthesis process in different proportions of co-solvent ethanol. The SBA-15 molecular sieve was synthesized by adopting the following molar composition of reaction mixture: 1TEOS: 0.017 P123: 5.7 HCl: 173 H2O: x EtOH. In which X took the values 10, 20, 30 and 40 due to the ethanol co-solvent ratio. Analyzing the X-ray diffractograms, it was possible to observe a greater structural organization for a higher molar proportion of co-solvent. The micrographs showed agglomerates of spherical particles which by increasing molar proportion of ethanol co-solvent became larger and more defined. By the BET method, it was observed that as the proportion of co-solvent increased the specific surface area also increase and a decrease in micropores occurred, pointing to the porous nature of the material. The walls of the material became thicker as it increased the proportion of co-solvent making it the most stable material.

A New Method for Immobilization of NDHPI on SBA-15 Carrier Used as Catalyst for Selective Oxidation of Toluene

Mesoporous molecular sieve SBA-15 immobilized N,N-dihydroxypyromellitimide (NDHPI) was prepared by a new method, which was realized through the coupling NDHPI with pre-grafted glycidoxypropyl chains of glycidoxypropyl-SBA-15. SBA-15 immobilized N-hydroxyphthalimide (NHPI) by impregnation method was also prepared for comparison. The two catalysts were characterized by Fourier transform infrared spectroscopy, N2 adsorption–desorption technique, thermogravimetric analyses, X-ray diffraction, scanning electron microscope, transmission electron microscope and X-ray photoelectron spectroscopy. Then the catalysts and N,N-bis(salicylidene) ethylenediiminocobalt (Cosalen) complex were used into oxidation of toluene with molecular oxygen. The more active and reusable catalyst was the immobilized one coupled by NDHPI with glycidoxypropyl-SBA-15, which improved the total selectivity of benzaldehyde and benzyl alcohol to 46.0 % with the conversion of toluene 14.8 % at 90 °C for 7 h. Mesoporous molecular sieve SBA-15 immobilized N,N-dihydroxypyromellitimide (NDHPI) was prepared by a new method, which was realized through the coupling NDHPI with pre-grafted glycidoxypropyl chains of glycidoxypropyl-SBA-15. SBA-15 immobilized NHPI by impregnation method was also prepared for comparison. Their structure was characterized and their catalytic performance combined with Cosalen complex in the molecule oxidation of toluene were compared. Their reusability performance was also discussed.

Quantitative analysis of flavanones from citrus fruits by using mesoporous molecular sieve-based miniaturized solid phase extraction coupled to ultrahigh-performance liquid chromatography and quadrupole time-of-flight mass spectrometry

An analytical procedure based on miniaturized solid phase extraction (SPE) and ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry was developed and validated for determination of six flavanones in Citrus fruits. The mesoporous molecular sieve SBA-15 as a solid sorbent was characterised by Fourier transform-infrared spectroscopy and scanning electron microscopy. Additionally, compared with reported extraction techniques, the mesoporous SBA-15 based SPE method possessed the advantages of shorter analysis time and higher sensitivity. Furthermore, considering the different nature of the tested compounds, all of the parameters, including the SBA-15 amount, solution pH, elution solvent, and the sorbent type, were investigated in detail. Under the optimum condition, the instrumental detection and quantitation limits calculated were less than 4.26 and 14.29ngmL−1, respectively. The recoveries obtained for all the analytes were ranging from 89.22% to 103.46%. The experimental results suggested that SBA-15 was a promising material for the purification and enrichment of target flavanones from complex citrus fruit samples.