Bis Triethoxysilyl Methane Research Articles

Amine-containing yolk-shell structured magnetic organosilica nanocomposite as a highly efficient catalyst for the Knoevenagel reaction.

The yolk-shell structured silica nanocomposites have been considered by many researchers due to their specific physical and chemical properties. These materials have been widely used in adsorption and catalysis processes. Especially, the void space of yolk-shell nanostructures can provide a unique environment for storage, compartmentation, and confinement in host-guest interactions. In this paper, for the first time, the preparation, characterization, and catalytic application of a novel amine-containing magnetic methylene-based periodic mesoporous organosilica with yolk-shell structure (YS-MPMO/pr-NH2) are developed. The magnetic periodic mesoporous organosilica nanocomposite was synthesized through surfactant-directed co-condensation of bis(triethoxysilyl)methane (BTEM) and tetraethoxysilane around Fe3O4 nanoparticles. After Soxhlet extraction, the surface of YS-MPMO nanocomposite was modified with 3-aminopropyl trimethoxysilane to deliver YS-MPMO-pr-NH2 nanocatalyst. This catalyst was characterized by using EDX, FT-IR, VSM, TGA, XRD, nitrogen-sorption, and SEM analyses. The catalytic activity of YS-MPMO/pr-NH2 was studied in the Knoevenagel reaction giving the corresponding products in a high yield and selectivity. The YS-MPMO/pr-NH2 nanocatalyst was recovered and reused at least four times without a significant decrease in efficiency and activity. A leaching test was performed to study the nature of the catalyst during reaction conditions Also, the catalytic performance of our designed nanocomposite was compared with some of the previous catalysts used in the Knoevenagel reaction.

Gas permeation properties of bridged-type organosilica membranes at extremely low temperatures and the application to oxygen separation

A bridged-type organosilica, bis(triethoxysilyl)methane (BTESM) membrane was evaluated in detail for single-gas permeation at temperatures ranging from −130 to −200 °C, and for binary (O2/He, O2/N2) separation at 30 and -115 °C, respectively. The permeance of He, Ar, and N2 demonstrated a trend of activated diffusion as permeance increased with an increase in the temperature; O2 permeance, however, reached its maximum value at about −80 °C. O2 permeance increased with a decrease in the temperature (30 to −80 °C), and permeance then gradually decreased (−80 to −130 °C), which demonstrates surface diffusion. In the case of O2/He binary separation, both O2 and He permeated according to molecular sieving at 30 °C, but at −115 °C, O2/He selectivity was enhanced approximately 10-fold due to permeation blockage by adsorbed O2. On the other hand, in the case of O2/N2 binary separation at −115 °C, the effect of permeation blocking by adsorbed O2 permeance was lessened due to the effect of competitive adsorption, which translated to a level of O2/N2 selectivity that was only 1.5-fold higher than that at 30 °C.

Inorganic Chemistry in Dalian University of Technology: Fundamental Science and Solution for Renewable Energy, Environment, Health, and Materials

Inorganic Chemistry in Dalian University of Technology: Fundamental Science and Solution for Renewable Energy, Environment, Health, and Materials

The Effect of C/Si Ratio and Fluorine Doping on the Gas Permeation Properties of Pendant-Type and Bridged-Type Organosilica Membranes.

A series of pendant–type alkoxysilane structures with various carbon numbers (C1–C8) were used to fabricate sol–gel derived organosilica membranes to evaluate the effects of the C/Si ratio and fluorine doping. Initially, this investigation was focused on the effect that carbon-linking (pendant–type) units exert on a microporous structure and how this affects the gas-permeation properties of pendant–type organosilica membranes. Gas permeation results were compared with those of bridged–type organosilica membranes (C1–C8). Network pore size evaluation was conducted based on the selectivity of H2/N2 and the activation energy (Ep) of H2 permeation. Consequently, Ep (H2) was increased as the C/Si ratio increased from C1 to C8, which could have been due to the aggregation of pendant side chains that occupied the available micropore channel space and resulted in the reduced pore size. By comparison, these permeation results indicate that pendant–type organosilica membranes showed a somewhat loose network structure in comparison with bridged–type organosilica membranes by following the lower values of activation energies (Ep). Subsequently, we also evaluated the effect that fluorine doping (NH4F) exerts on pendant−type [methytriethoxysilane (MTES), propyltrimethoxysilane (PTMS)] and bridged-type [1,2–bis(triethoxysilyl)methane (BTESM) bis(triethoxysilyl)propane (BTESP)] organosilica structures with similar carbon numbers (C1 and C3). The gas-permeation properties of F–doped pendant network structures revealed values for pore size, H2/N2 selectivity, and Ep (H2) that were comparable to those of pristine organosilica membranes. This could be ascribed to the pendant side chains, which might have hindered the effectiveness of fluorine in pendant–type organosilica structures. The F–doped bridged–type organosilica (BTESM and BTESP) membranes, on the other hand, exhibited a looser network formation as the fluorine concentration increased.

Synthesis and Characterization of High Surface Area Transparent SiOC Aerogels from Hybrid Silicon Alkoxide: A Comparison between Ambient Pressure and Supercritical Drying.

In this article, highly porous and transparent silicon oxycarbide (SiOC) gels are synthesized from Bis(Triethoxysilyl) methane (BTEM). The gels are synthesized by the sol-gel technique followed by both ambient pressure and supercritical drying. Then, the portion of wet gels have been pyrolyzed in a hydrogen atmosphere at 800 and 1100 °C. The FT-IR spectroscopy analysis and nitrogen sorption results indicate the successful synthesis of Si-O-Si bonds and the formation of mesopores. From a hysteresis loop, the SiOC ceramics showed the H1 type characteristic with well-defined cylindrical pore channels for the aerogel and the H2 type for the ambigel samples, indicating that the pores are distorted due to the capillary stress. The produced gels are mesoporous materials having high surface areas with a maximum of 1140 m2/g and pore volume of 2.522 cm3/g obtained from BTEM aerogels. The pyrolysis of BTEM aerogels at 800 °C results in the production of a bulk and transparent sample with a slightly pale white color, while BTEM xerogels are totally transparent and colorless at the same temperature. At 1100 °C, all the aerogels become opaque brown, confirming the formation of free carbon and crystalline silicon.

Nanoscale tailoring on thin bimetallic organo-oxide membranes for H2/CO2 separation

The design of tailored novel membrane networks with excellent hydrothermal stability allowing gas sieving is highly desired to take them a step closer to large scale commercialization for energy efficient separation. Bistriethoxysilylmethane (BTESM) containing SiCSi bonds was used as a precursor for the fabrication of Ti-incorporated BTESM organosilica membranes on a macroporous ceramic support with a mesoporous intermediate layer. The precise engineering on the sol-gel parameters allowed the formation of bimetallic clusters with 2–4 nm size range in the clear organo-oxide sols. XPS analyses indicated the development of SiOTi connections in the organo-oxide membrane network. A high H2 permeance of 6.3 × 10−7 mol/m2sPa and attractive ideal selectivities of 10, 10, 119 and 222 for H2/N2, H2/CH4, H2/C3H6 and H2/C3H8, respectively are attained from an exceptionally thin BTESM membrane. H2/CO2 ideal selectivity increases from 4 to 8 upon incorporation of 15 mol% Ti into membrane network while selectivities increase to 32 for H2/N2, 44 for H2/CH4, and 246 for H2/C3H8 with 1.25-fold increase in H2 permeance. H2/CO2 ideal selectivity of 24 was achieved with moderate H2 permeance of 1.7 × 10−7 mol/m2sPa after hydrothermal treatment for 45 h for BTESM15 membrane as thin as 65 nm. This is the one of the thinnest ceramic supported organosilica membrane reported having acceptable H2 permeance after hydrothermal treatment.

Magnetic yolk-shell structured methylene and propylamine based mesoporous organosilica nanocomposite: A highly recoverable and durable nanocatalyst with improved efficiency

A yolk–shell (YS) structured nanocomposite with magnetite core and methylene- and propylamine-based bifunctional periodic mesoporous organosilica (BPMO) shell (YS-Fe3O4@Am-PMO) was synthesized and employed as a powerful nanocatalyst for Knoevenagel condensation. The YS-Fe3O4@Am-PMO was synthesized via cetyltrimethylammonium bromide (CTAB) directed co-condensation of bis[(3-trimethoxysilyl)propyl]amine (BTMSPA) and bis(triethoxysilyl)methane (BTESM) around Fe3O4@SiO2 nanoparticles under basic conditions. The Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), thermal gravimetric (TG), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses were used to characterize this nanocomposite. The catalytic activity of YS-Fe3O4@Am-PMO was successfully studied in the Knoevenagel condensation under both thermal and ultrasonic conditions. The YS-Fe3O4@Am-PMO nanocatalyst could be magnetically recovered and reused several times with no important decrease in its performance.

Hydrocarbon permeation properties through microporous fluorine-doped organosilica membranes with controlled pore sizes

F-BTESM membranes were fabricated by doping a fluorine source into bis(triethoxysilyl)methane (BTESM), which is an organosilica precursor composed of Si–CH2–Si bonds. Pore size controllability and C3–C4 hydrocarbon permeation properties for F-BTESM membranes with different concentrations of fluorine were evaluated using single-gas permeation and N2/C3–C4 hydrocarbon binary separation. The pore size of an organosilica membrane can be precisely controlled via doping with the correct concentration of fluorine. The molecular sieving properties for C3/C4 hydrocarbon separation such as that for C3H6/iso-C4H8 was dramatically enhanced with the addition of a fluorine concentration of F/Si = 0.05, and this membrane showed a C3H6/iso-C4H8 permeance ratio of 388 at 50 °C. The permeance of hydrocarbon gases was increased with an expansion of the pore size, and F-BTESM (F/Si = 0.15) showed a high level of C3H6 permeance (>5.0 × 10−7 mol m−2 s−1 Pa−1). The results of hydrocarbon adsorption and single permeation properties showed that the carbon number of the hydrocarbons and the presence of unsaturated bonds enhanced the adsorption affinity to silica-derived materials. In the binary separation of N2/C3–C4 hydrocarbons, N2 permeance was remarkably decreased by comparison with single-gas permeation, which was due to a blocking effect by the hydrocarbons adsorbed inside the pores. Hydrocarbon gases with a stronger affinity tended to inhibit the permeation of N2.

On-Line NIR to Regulate Pervaporation Process: Application for Dehydration.

The regeneration of volatile organic solvents via dehydration tests, from 90 wt %, was evaluated by pervaporation using an on-line near-infrared (NIR) spectrometer. Experiments were performed using a bis(triethoxysilyl)methane (BTESM)-based ceramic HybSi® membrane at temperatures of 20, 30 and 40 °C. The presence of an on-line NIR allows continuous monitoring of the process without sampling, and quickly estimates mass fractions of species in the retentate. Dehydration tests were performed at 30 °C in order to confirm the on-line NIR reproducibility, and closely matched results obtained with an off-line densimeter. These results validated the usefulness of the on-line NIR and provided the same precision whatever the mass fraction in the retentate. A good on-line reproducibility was found, with an agreement between the on-line NIR and off-line densimeter, obtaining an average deviation of ±0.058 wt %, ±0.17 wt % and ±0.049 wt %, respectively, at 20, 30 and 40 °C.

Fluorine Doping of Microporous Organosilica Membranes for Pore Size Control and Enhanced Hydrophobic Properties.

Fluorine-doped organosilica membranes for gas and pervaporation (PV) separation were fabricated using a sol–gel method. NH4F and bis(triethoxysilyl)methane (BTESM) were selected as the dopant and Si precursor, respectively, for the fabrication of fluorine-doped organosilica membranes. Doping with fluorine was evaluated for its effect on the physicochemical properties of organosilica (hydrophobicity/hydrophilicity and network size). Fluorine doping dramatically eliminated the formation of Si–OH groups in the sol, so that the condensation of Si–OH groups during the calcination process was suppressed. It is possible that fluorine doping enlarged the network pore sizes in organosilica, because the F-BTESM (F/Si = 1/9) membrane showed superior He and H2 permeance with a low H2/N2 permeance ratio that corresponded to the network pore size by comparison with an undoped BTESM membrane. The F-BTESM (F/Si = 1/9) membranes clearly showed a high level of C3H6 permeance (>3.0 × 10–7 mol m–2 s–1 Pa–1) with a high C3H6/SF6 permeance ratio (∼250), which suggests that the network pore size of F-BTESM is suitable for the separation of large molecules such as hydrocarbon gases (C3/C4, C4 isomer, etc.). Organosilica membranes both with and without fluorine doping showed stable PV performance because of the fact that H2O permeance and each permeance ratio under different separation systems was approximately constant over 10 h at 70 °C. Fluorine doping enhanced the hydrophobic nature of the organosilica, which was confirmed by the H2O adsorption and PV properties.

Gas permeation properties for organosilica membranes with different Si/C ratios and evaluation of microporous structures

Organosilica membranes were fabricated using bridged organoalkoxysilanes (bis(triethoxysilyl)methane (BTESM), bis(triethoxysilyl)ethane (BTESE), bis(triethoxysilyl)propane (BTESP), bis(trimethoxysilyl)hexane (BTMSH), bis(triethoxysilyl)benzene (BTESB), and bis(triethoxysilyl)octane (BTESO)) to produce highly permeable molecular sieving membranes. The effect of the organoalkoxysilanes on network pore size and microporous structure was evaluated by examining the molecular size and temperature dependence of gas permeance across a wide range of temperatures. Organosilica membranes showed H2/N2 and H2/CH4 permeance ratios that ranged from 10 to 150, corresponding to network pore size, and both H2 selectivity decreased with an increase in the carbon number between 2 Si atoms. Organosilica membranes showed activated diffusion for He and H2, and a slope of temperature dependence that increased approximate to the increase in the carbon number between 2 Si atoms. The relationship between activation energy and He/H2 permeance ratio for SiO2 and organosilica membranes suggested that the molecular sieving can dominate He and H2 permeation properties via the rigid microporous structure, which was constructed by BTESM and BTESE. With increased in the carbon concentration in silica, polymer chain vibration in organic bridges, which is a kind of solution/diffusion mechanism, can dominate the permeation properties. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4491–4498, 2017

Gas permeation properties through Al-doped organosilica membranes with controlled network size

The sol–gel method was applied to the fabrication of Al-doped bis (triethoxysilyl) methane (BTESM)-derived membranes. The single-gas permeation properties for Al-doped BTESM-derived membranes were examined to evaluate the effect of aluminum concentration on amorphous silica network sizes. Each permeance was decreased with an increase in the Al concentration, and the H2/CH4 and H2/C3H8 permeance ratios increased with an increase in Al concentration. For example, an Al-doped BTESM (Si/Al=8/2) membrane fabricated at 200°C showed a H2 permeance of 4.4×10−7molm−2s−1Pa−1, which was approximately 1/10th that of a BTESM membrane fabricated at 200°C. The H2/CH4 and H2/C3H8 permeance ratios were 60 and 2700 with Al doping, but 30 and 1000 without Al-doping, respectively. The activation energy of He, H2, N2, and CH4 permeation was increased with an increase in the Al concentration, indicating that the pore size of BTESM-derived networks was decreased with an increase in Al concentration. The decrease in BTESM-derived network sizes that resulted from an increase in the Al concentration can be ascribed to the absolute amount of Al incorporated into BTESM-derived networks and/or coordinated with Si-OH groups, as suggested by 27Al MAS NMR. High C3H6/C3H8 permeance ratios of approximately 40 for Al-doped BTESM (Si/Al=9/1) membranes fabricated at 200°C were achieved through the precise control of the silica network size via a spacer method using Si–C–Si units as well as the incorporation of Al in BTESM-derived networks.

Pore size control of Al-doping into bis (triethoxysilyl) methane (BTESM)-derived membranes for improved gas permeation properties

The sol–gel method was applied to Al-doped bis (triethoxysilyl) methane (BTESM, Si–C–Si unit) membranes. High C3H6 : C3H8 permeance ratios of approximately 40 at 200 °C were achieved through the precise control of the silica network size via a spacer method using Si–C–Si units as well as the incorporation of Al in BTESM-derived networks.

Separation of propylene/propane binary mixtures by bis(triethoxysilyl) methane (BTESM)-derived silica membranes fabricated at different calcination temperatures

Abstract Bis(triethoxysilyl) methane (BTESM), which consists of Si–C–Si bonds, was used as a membrane precursor in the control of amorphous silica network size for separation of C 3 H 6 and C 3 H 8 molecules. Single and binary-component gas permeation/separation characteristics were examined at temperatures ranging from 50 to 200 °C for BTESM-derived silica membranes fabricated at various temperatures. Normalized Knudsen-based Permeance (NKP) was applied to evaluate the effect of calcination temperatures on amorphous silica network size. Pore size distribution, as determined by single gas permeation as well as by NKP plotting, suggested that average pore size was successfully tuned by changing the calcination temperatures. BTESM-derived silica membranes showed C 3 H 6 permeance (0.28–6.3×10 −7 mol m −2 s −1 Pa −1 ) and a C 3 H 6 /C 3 H 8 permeance ratio (6.9–33) at 50 °C. For binary-component gas separation at 50 °C, preferentially adsorbed C 3 H 6 molecules could efficiently block the permeation of C 3 H 8 molecules, resulting in C 3 H 6 /C 3 H 8 permeance ratios that were higher than those obtained by single-gas permeation. The ratios of α (separation)/ α (ideal) for BTESM-derived membranes fired at 200 °C were higher than those for membranes fired at 350 °C, due to the higher density of silanol groups, that can interact with the π-bond (C=C double bond) of C 3 H 6 molecules.

Organic–Inorganic Hybrid Silica Membranes with Controlled Silica Network Size for Propylene/Propane Separation

Bis(triethoxysilyl)methane (BTESM), which consists of Si–C–Si bonds, was used as a membrane precursor to control the size of amorphous silica networks. The single gas permeation characteristics of hybrid silica membranes were examined to determine the effect of silica precursors on amorphous networks. Pore size distribution, as determined by single gas permeation, suggested that average pore size was in the following order: bis(triethoxysilyl)ethane (BTESE)-derived silica > BTESM-derived silica > tetraethoxysilane (TEOS)-derived silica, due to differences in the minimum units of the silica precursor. The high C3H6/C3H8 separation performance of BTESM-derived silica membranes in a wide temperature range (50–200 °C) can be due to the control of silica network size by the “spacer” method using a Si–C–Si unit. For example, a BTESM-derived silica membrane showed a high C3H6 permeance of 6.32 × 10–7 mol m–2 s–1 Pa–1 with a C3H6/C3H8 permeance ratio of 8.8 at 50 °C. The order of C3H6 and C3H8 permeances of BTESM...

Molecular Bonding Structure of Alkylene-Bridged Organosilicate Glass Films

A quantitative and systematic investigation about the molecular nature of the dielectric and mechanical properties of organic/inorganic hybrid glass film with alkylene bridges was performed. The hybrid glass film was prepared from a sol precursor solution of the mixture of tetraethoxysilane (TEOS) and bis(triethoxysilyl)methane (BTM). The mole fraction of BTM and TEOS was changed in order to control the amount of ≡Si—(CH2)—Si≡. Then, the dielectric constant decreased monotonically from 4.35 to 3.65 with the full replacement of ≡Si—O—Si≡ with ≡Si—(CH2)—Si≡. Young’s modulus also decreased from 48.2 to 36.5 GPa. The same study was also performed about the organosilicate hybrid glass prepared from the mixture of bis(triethoxysilyl)ethane (BTE) and TEOS. Then, the further decreases in the dielectric constant and the Young’s modulus were measured. Molecular bonding structures were analyzed by investigating the atomic composition from Rutherford backscattering spectrometry and complex dielectric function concern...

Porous silicon oxycarbide glasses from hybrid ambigels

Highly porous ambigels (aerogel-like materials dried at ambient pressure) have been employed for the synthesis of porous siliconoxycarbide (SiOC) glass. Ambigels were synthesized from methyltriethoxysilane (MTES), (bistriethoxysilyl)methane (BTEM) and 1,2(bistriethoxysilyl)ethane (BTEE) as the starting precursors which were later pyrolysed yielding porous SiOC glass. The synthesized ambigels possess very high surface area and pore volumes and a maximum surface area of 1131 m 2/g with a pore volume of 1.29 cm 3/g could be achieved for the gels derived from BTEE. After pyrolysing the ambigels in inert atmosphere, the porosity has been retained and a surface area as high as 430 m 2/g could be attained. Solid state NMR studies have been employed to verify the retention of Si–C bond in the pyrolysed glass.

Methylene-functionalized saponite: A new type of organoclay with CH 2 groups substituting for bridging oxygen centers in the tetrahedral sheet

The synthesis of saponite in the presence of bis(triethoxysilyl)methane (BTESM) as an organosilicon reagent results in the replacement of up to 33.3% of the oxygen atoms in the tetrahedral sheet by bridging methylene groups. The methylene-functionalized saponites represent a new form of covalently bonded organoclay that truly is isomorphic with purely inorganic saponite made under equivalent reaction conditions from sodium silicate as the silicon source. The isoelectronic and isolobal relationship between methylene and bridging oxygen centers is essential for methylene saponite formation. Bridging ethylene groups are not incorporated into the Kagome net of the basal surfaces due to a mismatch in bridging group size. The textural properties of the methylene saponites are similar to those for purely inorganic magnesium saponite made under equivalent synthetic conditions in the absence of BTESM. Layer stacking disorders afford large surface areas (∼ 550 to 650 m 2/g), making the methylene saponites attractive candidates for use as adsorbents and functional fillers for polymer composites.

Organic group-bridged hybrid materials with a Faujasite X zeolite structure (ZOF-X)

Abstract Zeolites with organic group-bridged inorganic frameworks (ZOFs) with a Faujasite X zeolite structure (ZOF-X) and a Si/Al ratio around 1.3 have been synthesized for the first time, where oxygen atoms in the zeolite frameworks are partially replaced by methylene groups using methylene-bridged bis[triethoxysilyl]methane (BTESM) as a unique silicon source. The phases were examined by powder X-ray diffraction and the presence of ∼1.5 wt.% carbon within the framework has been disclosed through 29 Si magic-angle spinning (MAS) NMR, FTIR and C elemental analysis. Another indirect proof of the insertion of organic groups in the framework is provided by the more pronounced hydrophobic character of ZOF-X compared to the conventional LSX zeolite, as revealed by thermogravimetry. The ZOF-X materials present the conventional morphology and microporous textural properties of zeolitic materials. Some terminal Si–CH 3 groups were revealed by FTIR spectroscopy. The present study showed that the synthesis of methylene-bridged zeolite framework is quite sensitive to many parameters such as the crystallization conditions (temperature and time), the ageing conditions (time, temperature, static or stirring and open or closed system) as well as the batch composition, in particular to the water content. The formation of the organozeolite structure ZOF-X takes much longer time compared with that of their inorganic counterparts.

Synthesis of periodic mesoporous organosilica from bis(triethoxysilyl)methane and their pyrolytic conversion into porous SiCO glasses

Periodic mesoporous organosilica (PMO) have been prepared from bis(triethoxysilyl)methane (BTM) and cetyltrimethylammonium chloride (C 16TAC). A large range of synthesis conditions (pH, C 16TAC/BTM ratio, post-treatment and concentration) were used to study their effects on the structure of the as-prepared meso-structured samples. The sample obtained with the optimised composition presents a 2D-hexagonal structure with a large surface area of about 950 m 2/g. This material has been pyrolysed under Argon up to 1000 °C. Conversion into a silicon oxycarbide glass has been followed by X-ray diffraction. The organised structure can be retained until 800 °C. Further characterisations were performed by 29Si MAS NMR, 13C CP MAS NMR and N 2 adsorption–desorption experiments to follow the structural changes occurring during the pyrolysis.