29Si CP MAS Research Articles

3-Arm PEG Based Amphiphilic Polymer Sorbents for Polar and Non-Polar Liquids

Crosslinked polymer gels are gaining technological and industrial attention due to their sophisticated application features. Herein, a highly effective amphiphilic polymeric network capable of absorbing polar and nonpolar solvents was produced using hydrophilic glycerol ethoxylate, a member of star type polyethylene glycol (s-PEG), and different hydrophobic organosilane monomers by bulk polymerization as utilized under an inert atmosphere. In this context, the preparation of amphiphilic polymeric networks was achieved by the reaction between hydroxyl terminated s-PEG and ethoxysilane terminated organosilane without using any initiator, activator or a catalyst. SEM, FTIR, 13C and 29Si CPMAS NMR and TGA are used for morphological, structural and thermal characterization of the prepared materials. Likewise, the absorption behavior of amphiphilic polymeric networks was determined by measuring their swelling ratios in polar and nonpolar solvents. Because of having a hydrophobic and hydrophilic structure in their 3D polymeric structure, the obtained polymeric networks behave as an organogel in oil medium, while they can prepared as a hydrogel in aqueous medium. The effect of crosslinker’s difference on the swelling capacity of sorbent were researched by comparing different molecular weight of monomers, and it was found that the molecular structure of organosilane monomers had significant influence on the swelling ability of obtained amphiphilic sorbents. By the use of easy preparations, not needing extra agents for the synthesis, having high and quick absorption abilities in organic solvents showed that the resulting amphiphilic sorbent have potential as absorbents for different organic solvents. Also, the degradable features of amphiphilic polymer networks in water open up optimum application opportunities for additional uses, such as with drug delivery agents.

Recyclable Mesoporous Organosilica Nanoparticles Derived from Proline-Valinol Amides for Asymmetric Organocatalysis

Going a step further from bulk organosilicas to nanosized materials, we describe herein the preparation of mesoporous organosilica nanoparticles derived from mono- and bis-silylated proline-valinol amides, both by grafting on preformed mesoporous silica nanoparticles (MSN) and by a co-condensation method in neutral medium using Brij-56/CTAB as templates. This is the first report on the obtention of functionalized MSN by a co-condensation procedure with a structurally complex chiral precursor. The functionalized MSN have been characterized by elemental analysis, 29Si and 13C CP MAS NMR, transmission electron microscopy, scanning electron microscopy, N2-sorption measurements, dynamic light scattering, ζ-potential, and powder X-ray diffraction. We have evaluated the activity of these materials as recyclable catalysts in the asymmetric aldol reaction. The best organocatalysts are those derived from the monosilylated precursor, observing good diastereo- and enantiomeric ratios with a simple and environmentally friendly optimized protocol (water, 0 °C, absence of cocatalyst). The nanocatalyst was easily recovered by centrifugation and recycled up to five runs without loss of activity and selectivity. The use of organosilica nanoparticles reduces the problems of diffusion and low reaction rates encountered with bulk organosilicas.

Pd-chelated 1,3,5-triazine organosilica as an active catalyst for Suzuki and Heck reactions

Design of novel functional periodic mesoporous organosilica with molecular level control finds applications in several fields of energy and environmental research including adsorption, catalysis, nanotechnology, and energy harvesting. Herein we present a melamine (1,3,5-triazine) functionalized periodic mesoporous silica (MPMO) by self-assembly of N2,N4,N6-tris(3-(triethoxysilyl)propyl)-1,3,5-triazine-2,4,6-triamine (TTET) with tetraethylorthosilicate (TEOS) via cocondensation strategy. The TTET silsesquioxane precursor was synthesized by the condensation reaction between cyanuric chloride and 3-aminopropyl triethoxysilane. The resultant MPMO material serves as an effective solid chelating agent through amine and triazine functionalities for Pd(II) to provide Pd-MPMO. The Pd-MPMO material was thoroughly characterized by a small-angle XRD, HRTEM, N2 sorption, 13C CP-MAS NMR, 29Si CP-MAS NMR, and ICP analyses. The Pd-MPMO serves as an active catalyst for CC bond formation reactions by Suzuki- and Heck cross-coupling methodologies under ligand- and cocatalyst-free conditions. Notably, the present catalytic protocol demonstrates a wide spectrum of substrate scope towards Suzuki coupling between aryl halides (I−, Br−, Cl−) and aryl boronic acids with high turn-over-number (TON) in aqueous phase under air ambience. Whereas for Heck-coupling reaction, the phenyl iodides furnished high TON than the other aryl halides. Investigation of Pd-leaching by a hot filtration test as well as reusability experiments confirms the true heterogeneous nature of present Pd-MPMO and its robustness in terms of substrate scope, catalyst stability, and durability.

Ionic Liquid Dispersed Ti/SBA-15 for Double-Bond Cleavage Oxidation of α-Methylstyrene into Acetophenone

A composite material Ti/SIL was prepared by Ti(OC4H9)4 coordinating to imidazolium ionic liquid grafted on SBA-15 and characterized by FT-IR, XRD, TEM, XPS, NH3-TPD and N2 adsorption–desorption technique. The catalytic performance of the prepared Ti/SIL for solvent-free oxidation of α-methylstyrene (AMS) to acetophenone using H2O2 oxidant was evaluated, achieving high TOF (23.2 h−1). The adsorption behavior of AMS via interaction with Ti4+ and Si–O active sites on the catalyst surface was measured by in situ DRIFTS, 29Si CP MAS NMR spectroscopy and analyzed by DFT theoretical calculation. Based on these analysis results, the reaction mechanism, involving the activation, consecutive conversion of AMS and homolytic decomposition of H2O2 on the catalyst surface to generate the product was proposed.

Reactive extrusion of sol-gel silica as fire retardant synergistic additive in ethylene-vinyl acetate copolymer (EVA) composites

Silica derived from sol-gel approach was used as co-filler in aluminium hydroxide (ATH) or hydromagnesite (HM) ethylene-vinyl acetate (EVA) formulations. In this bottom-up approach, the silica network is formed inside the extruder in a first process step. The 3D silica structure is investigated by solid-state nuclear magnetic resonance (ssNMR) spectroscopy and a combined TGA-FTIR analysis revealing a partially incomplete reaction to form silica particles. In addition, 29Si CPMAS NMR showed the formation of chemical Si–C bonds between EVA and silica networks. The performance enhancement of the fire retardant properties was established by comparing with composites prepared by a top-down approach, i.e by adding preformed silica. It is confirmed that the preformed silica acts as a synergistic agent with both ATH or HM, increasing the flame retardant properties (limiting oxygen index, UL-94 and cone calorimeter tests) of EVA composites, however, the sol-gel silica shows the best performances in reducing both heat release and smoke production. The role of the sol-gel structure was deeply investigated in correlation with combustion test.

Functionalization of porous siliceous materials, Part 2: Surface characterization by inverse gas chromatography

Surface modification of porous glass beads by ethanol-based 3-mercaptopropyltrimethoxysilane (MPTMS) grafting solutions is directly evidenced by nitrogen adsorption, elemental analysis, thermogravimetry, infrared and 29Si CP MAS NMR spectroscopy. Furthermore, the energetic characterization of the surface is essential to understand comprehensively the physico-chemical interactions between the pristine and MPTMS-modified surface and its gas/liquid-phase environment. In this study, inverse gas chromatography (IGC) is used to characterize the surface properties of porous glass (PG). By means of IGC at infinite dilution (IGC-ID), the dispersive component of the surface energy (γsd), the enthalpy and entropy of adsorption of C6-C10 hydrocarbon probes were determined at temperatures between 30 and 120 °C. The specific component of the surface energy (γssp) at the temperature of 120 °C has been obtained via the Van Oss theory and a least-squares procedure evaluating the IGC data of 8 polar probe molecules collectively. After surface silylation, the total surface energy (γst) decreased from 402 to 255 mJ/m² indicating both a reduced wettability and an increased hydrophobicity of the MPTMS-modified PG. Moreover, the acidity/basicity parameters according to the Van Oss and the Gutmann approach indicated that the acidity of the PG surface decreases by MPTMS grafting.Using n-octane and isopropanol probes, IGC at finite concentration (IGC-FC) was applied to obtain their adsorption isotherms and subsequently the BET specific surface areas. In addition, the surface heterogeneity of the studied PGs was also computed. The energy distribution functions of adsorption sites were monomodal (peak maximum at about 22 kJ/mol) for the n-octane probe, while isopropanol revealed a bimodal distribution function (maxima at about 18 and 25 kJ/mol) on both pristine and MPTMS-modified PG. Furthermore, the proportion of high energy sites (apparently assigned to SiOH groups) has been reduced by surface modification from 65% to only 35% despite a high surface coverage of ˜10 MPTMS species/nm2. These findings are in agreement with the results of 29Si CP MAS NMR measurements and are supported by DFT calculations on the adsorption of isopropanol and n-octane on the surface of a silica cluster model.

Nonordered porous silica-based pure inorganic and hybrid organic-inorganic materials prepared by a nonaqueous, nonthermal sol-gel process

Abstract Herein is reported the synthesis and characterization of nonordered porous silica-based materials, University of Guanajuato Materials (UGM), which were obtained from a mixture of alkoxysilanes by using a nonaqueous, nonthermal sol-gel methodology without the addition of any directing agent and using wet acetone (1% water content) as a hydrolytic agent. The textural properties of specific surface area, pore volume and pore size were determined by means of N2 physisorption at 77 K. The UGM silicas are described to be microporous, mesoporous and mixture of micro/mesoporous materials that may have Brunauer-Emmett-Teller (BET) surface areas of up to 300 and 600 m2/g, respectively. Some of these materials were organofunctionalized by a co-condensation route. On the one hand, the silica UGM-111-OP(OH)2 corresponds to a nonordered mixture of micro and mesoporous material with a surface area of 500 m2/g, and a Nafion®-[UGM-111-OP(OH)2] composite membrane was electrochemically characterized by cyclic voltammetry; the results indicated that the composite has promising potential for use as a proton-conductive material in proton-exchange membrane (PEM)-type fuel cells. On the other hand, the UGM-111-triamine silica is a mesoporous material with monomodal porosity (average pore diameter 3.75 nm) and a BET surface area of 570 m2/g; this material may have potential applications in the adsorption of metal ions such as copper (II). All materials were characterized in the solid state by 13C and 29Si CP-MAS, and UGM-111-OP(OH)2 was also characterized by 31P CP-MAS. Scanning electron microscopy (SEM) at 15000X magnification showed that both pure and hybrid organic-inorganic UGM silicas may be present as agglomerated spheres and that mesoporous pure UGM silicas may appear as nonuniform granular powders.

Effectiveness of novel xerogels adsorbents for cadmium uptake from aqueous solution in batch and column modes: Synthesis, characterization, equilibrium, and mechanism analysis

In the present study, new organic–inorganic mesoporous materials are prepared. The FTIR, SEM, 29Si CP MAS NMR and nitrogen adsorption–desorption experiments are utilized to portray the novel xerogels. Application for the cadmium(II) uptake from aqueous solution using the as-synthesized hybrid materials as adsorbent is explored. Operating parameters influencing the adsorption procedure, for instance, solution pH, contact time and temperature are contemplated. The adsorption kinetic analysis abides by pseudo-second-order model and the intra-particle diffusion model display that the rate-controlled step is directed by film-diffusion before all else and afterward is taken by intra-particle diffusion. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models are assigned to portray the adsorption isotherms. Experimental data seem to be adequate with Langmuir model showing high monolayer adsorption capacities of Cd(II) onto both novel adsorbents (507–493 mg g−1). Mean free energy values assessed from d–R isotherm prescribe that cadmium sequestration by the two hybrid materials eventuated by chemisorption. Besides, the dynamic process exposed relatively high breakthrough capacity for both xerogels and the column data are well validated by Thomas model. Computed thermodynamic parameters depict that the adsorption of Cd(II) ions onto the two adsorbents is favorable and exothermic in nature. FTIR and XPS analysis, uncover that the fundamental mechanism of the cadmium removal is the chelation of metal ions with the ligating nitrogen atoms (N) of amino functionalized xerogel (M1). Though, onto sulfhydryl-functionalized xerogel (M2) it is presumably through the ion-exchange reaction between Cd2+ ions and (SH) groups. The desorption investigation show that the synthesized hybrid materials possess a remarkable reusability. Prior tests produced on electroplating effluents reveal that the as-prepared xerogel could be strongly used for the cadmium uptake from real wastewater.

Biofunctionalization of Nano Channels by Direct In-Pore Solid-Phase Peptide Synthesis.

Diatom biosilica are highly complex inorganic/organic hybrid materials. To get deeper insights on their structure at a molecular level, model systems that mimic the complex natural compounds were synthesized and characterized. A simple and efficient peptide immobilization strategy was developed, which uses a well-ordered porous silica material as a support and commercially available Fmoc-amino acids, similar to the known solid-phase peptide synthesis. As an example, Fmoc-glycine and Fmoc-phenylalanine are immobilized on the silica support. The success of functionalization was investigated by 13 C CP MAS and 29 Si CP MAS solid-state NMR. Thermogravimetric analysis (TGA) and elemental analysis (EA) were performed to quantify the functionalization. Changes of the specific surface area, pore volume, and pore diameters in all modification steps were studied by Brunauer-Emmett-Teller based nitrogen adsorption-desorption measurements (BET). The combination of the analytical methods provided high grafting densities of 2.1±0.2 molecules/nm2 on the surface. Furthermore, they allowed for monitoring chemical changes on the pore surface and changes of the pore properties of the material during the different functionalization steps. This universal approach is suitable for the selective synthesis of pores with tunable surface-peptide functionalization, with applications to the synthesis of a big variety of silica-peptide model systems, which in the future may lead to a deeper understanding of complex biological systems.

Phosphate glass matrix composites incorporating trisilanol phenyl polyhedral oligomeric silsesquioxane prepared by viscous flow sintering method with enhanced benefits

The effect of mixing and sintering processes to prepare tin fluorophosphate glass (Pglass) matrix composites incorporating trisilanol phenyl polyhedral oligomeric silsesquioxane (TSP-POSS) was investigated by comparing manual and suspension mixing, one-step and stepwise sintering processes to explore the structure dynamics and physical properties in the composites as a function of the different process conditions used. Energy Dispersive X-ray analysis confirmed optimal homogeneous dispersion of the TSP-POSS molecules in the composites prepared by the suspension method. The observed increase of glass transition temperature and the reduction of non-bridging bonds in the composites are believed to be the reason for the effective dispersion of TSP-POSS molecules in the composites. The chemical reaction between the TSP-POSS and Pglass was strongly influenced by the mixing/dispersion and sintering processes investigated. 13C cross polarized magic angle spinning (CP MAS) solid state nuclear magnetic resonance (NMR) spectroscopy confirmed the chemical stability of the TSP-POSS during the sintering process at elevated temperatures. In addition, a chemical reaction between the TSP-POSS and Pglass was evidenced by 29Si CP MAS NMR analysis. This study will provide a better fundamental understanding of the effective dispersion mechanism of the TSP-POSS molecules in the Pglass matrix that will facilitate tailoring the physicochemical properties of the composites with addition of various small concentrations of TSP-POSS for a number of applications where the pure Pglass is not applicable due to the intrinsic properties of the Pglass.

Design, synthesis and characterization of polysiloxane and polyetherdiamine based comb-shaped hybrid solid polymer electrolytes for applications in electrochemical devices

In this study, polysiloxane and polyetherdiamine based comb-shaped solid polymer electrolytes (SPEs) are developed by hydrosilylation and sol-gel reactions of polymethylhydrosiloxane, allyltriethoxysilane, bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol and (3-glycidoxypropyl)trimethoxysilane followed by LiClO4 doping. The absence of residual Si‒H functionality in FTIR and 29Si CPMAS NMR spectra confirms the completion of hydrosilylation reaction. The formation of comb-shaped SPEs with silicate backbones is confirmed by 13C and 29Si solid-state NMR spectroscopy. The maximum ionic conductivity value of 5.8 × 10−4 S cm−1 is obtained for the SPE with [O]/[Li] ratio of 16 at 80 °C with electrochemical stability window reaching up to 4.8 V. The fabricated electrochromic device with the hybrid SPE of [O]/[Li] = 16 demonstrates good electrochromic contrast and optical density change values of 49.3% and 0.39, respectively, at wavelength of 550 nm. The results show that the present comb-shaped SPEs have potential to be used in various electrochemical devices.

Star PEG-based amphiphilic polymers: synthesis, characterization and swelling behaviors

This paper describes the preparation, characterization and application of pentaerythritol ethoxylate-based crosslinked polymers as sorbent materials for a variety of liquids. A bulk polymerization method has been employed to produce amphiphilic polymeric sorbents in a solvent-free medium at moderately high temperature that does not require any initiator, catalyst or an activator. The morphological, structural and thermal properties of amphiphilic polymeric sorbents were determined by means of Fourier transform infrared spectroscopy, 13C and 29Si CPMAS nuclear magnetic resonance, scanning electron microscope and thermal gravimetric analysis. Having hydrophobic and hydrophilic portions in the polymeric structure, the obtained sorbents have affinity toward both water and organic liquids. The effect of molecular weight of monomers on absorption ability was examined via swelling test. The swelling ability in binary mixtures was also studied to determine the absorption capacity of polymers in organic solvent–water mixtures. Absorption studies, absorption–desorption kinetics and reusability tests were also operated, and the experimental outcomes showed that the obtained polymers have high and quick absorption abilities and also can be reusable with no capacity loss in oils.

Oligomerization of light olefins in the presence of a supported Brønsted acidic ionic liquid catalyst

Oligomerization of C4-C5 olefins and olefin mixtures has been investigated in the presence of a supported ionic liquid phase (SILP) catalyst, obtained by the physisorption of 1-(4-sulfobutyl)-3-methylimidazolium trifluoromethanesulfonate on silica. Surface properties of the SILP phase were determined from the experimental data of their nitrogen adsorption/desorption isotherms. Fresh and spent catalyst were characterised by 13C- and 29Si-CP MAS NMR spectroscopy and thermogravimetric analysis. Reactivity of alkenes followed the awaited order of isobutene>but-1-ene>pent-1-ene. The main products of oligomerization of hydrocarbon mixtures, modelling the C4-C5 fraction of waste polyethylene cracking products, were isoolefins in the boiling point range corresponding to kerosene fraction components, which is applicable as jet fuel after hydrotreatment. Stability and recyclability of the catalyst could greatly be enhanced by a pretreatment of the fresh catalyst, carrying out an oligomerization experiment with pure isobutene.

Synthesis of new silica xerogels based on bi-functional 1,3,4-thiadiazole and 1,2,4-triazole adducts

ABSTRACTNew transparent Silica-based hybrid materials were synthesized by reaction of polymethylhydrosiloxane (PMHS) and organic compounds: 1,3,4-thiadiazole-2,5-diamine (1), 1,3,4-thiadiazole-2,5-dithiol (2) and 1H-1,2,4-triazole-3-thiol (3), in tetrahydrofuran as solvant using hexachloroplatinic acid (H2PtCl6.6H2O) as a catalyst. PMHS was used as a principal network forming agent, it has been cross-linked via hydrosilylation reaction with bi-functional heterocyclic compounds, leading to the formation of colored gels. These later dried (xerogels) were characterized by numerous techniques, including spectroscopy of (FT–IR) and 13C and 29Si CP MAS NMR. The xerogels morphology and texture were studied by scanning electron microscopy and Brunauer–Emmet–Teller method. According to N2-physisorption results, isotherms are classified as type IV with H2 type hysteresis loop; then, the xerogels are mesoporous materials. The optic and magnetic properties of the obtained materials were studied by UV–VIS and EPR spectroscopies, respectively. This study showed that all materials are paramagnetic semiconductors.

Additive-free continuous synthesis of silica and ORMOSIL micro- and nanoparticles applying a microjet reactor

The continuous wet chemical preparation of micro- and nanoparticles is a major challenge for the large-scale production of functional colloids. Here we present a general synthetic strategy for sol–gel-based materials via an additive free homogenous approach avoiding emulsion-based systems. A variety of different silica and organically-modified silica (ORMOSIL) spherical particles were prepared applying a condensation of prehydrolyzed alcoholic solution of organotrialkoxysilanes in a microjet reactor. This method presents a unique wet chemical production method for nano- and microscale materials. Methyl-, ethyl-, propyl-, vinyl-, phenyl-, and mixed ORMOSIL particles in the range of 75 nm–2 µm were successfully synthesized without the addition of stabilizing surfactants. The method was also investigated for the continuous preparation of pure silica particles, and we succeeded to produce continuously up to 23 g particles per minute. The influence of different organic groups on the crosslinking of the siloxane network was systematically studied applying various spectroscopic and thermoanalytical methods. The degree of condensation of the obtained particles depends on the organic rests of the trialkoxysilanes, which was studied with 29Si CP-MAS NMR. We were able to show that phenyl silsesquioxanes show less condensation in the particles than smaller alkyl or vinyl groups. In addition, the silane concentration has a significant influence on the particle size. Generally, smaller particle diameters are obtained after decreasing the silane concentration. The described process delivers a fast and large scale wet chemical production of various silsesquioxane and silica particles without the use of additives and is therefore suited for a variety of potential applications where high purity of the particles is necessary.

Effect of SiO2 amount on heterogeneous base catalysis of SiO2@Mg-Al layered double hydroxide.

The effects of SiO2 amount on the base catalysis of highly active finely crystallized Mg–Al type layered double hydroxides prepared by the co-precipitation method with coexistence of SiO2 spheres, denoted as SiO2@LDHs, were investigated. With the Si/(Mg + Al) atomic ratios of 0–0.50, the highest activity for the Knoevenagel condensation was observed in the case of Si/(Mg + Al) = 0.17, as the reaction rate of 171.1 mmol g(cat)−1 h−1. The base activity increased concomitantly with decreasing LDH crystallite size up to Si/(Mg + Al) atomic ratio of 0.17. However, above the Si/(Mg + Al) atomic ratio of 0.17, the reaction rate and TOFbase were decreased although the total base amount was increased. Results of TEM-EDS and 29Si CP-MAS NMR suggest that the co-existing SiO2 causes advantages for dispersion and reduction of the LDH crystallite to improve the base catalysis of SiO2@Mg–Al LDH, whereas the excess SiO2 species unfortunately poisons the highly active sites on the finely crystallized LDH crystals above a Si/(Mg + Al) atomic ratio of 0.17. According to these results, we inferred that the amount of spherical SiO2 seeds in the co-precipitation method is an important factor to increase the base catalysis of SiO2@LDHs; i.e. the control of Si/(Mg + Al) atomic ratio is necessary to avoid the poisoning of highly active base sites on the LDH crystal.

Comprehensive characteristic and potential application of POSS-coated MgO-SiO2 binary oxide system

This study concerns the possibility of functionalization of a binary oxide system with an organic agent in order to change its physicochemical properties and surface activity. The binary oxide material – MgO-SiO2–was obtained via a sol-gel route using organic precursors of magnesium oxide and silica, ammonia as catalyst and methanol as a solvent. The powder material prepared according to the proposed method of synthesis was functionalized with a commercial POSS compound – AminoethylaminopropylIsobutyl POSS®. The efficiency of immobilization of the modifying agent onto MgO-SiO2 material was evaluated by the FTIR, 29Si and 13C CP MAS NMR methods. Moreover, detailed physicochemical and structural characteristics of the resulting materials, including morphology, parameters of the porous structure, hydrophobic/hydrophilic nature and thermal stability, were determined. As a result of this functionalization, a novel group of oxide systems with defined physicochemical properties dedicated to specific applications was created. The functionalized form of the synthesized MgO-SiO2 material was successfully applied as a bond/stabilizer in polyol mixtures and as a flame retardant for polyurethane foams.

Diradicaloid or Zwitterionic Character: The Non-Tetrahedral Unsaturated Compound [Si4 {N(SiMe3 )Dipp}4 ] with a Butterfly-type Si4 Substructure.

The reduction of the tribromoamidosilane {N(SiMe3 )Dipp}SiBr3 (Dipp=2,6-iPr2 C6 H3 ) with potassium graphite or magnesium resulted in the formation of [Si4 {N(SiMe3 )Dipp}4 ] (1), a bicyclo[1.1.0]tetrasilatetraamide. The Si4 motif in 1 does not adopt a tetrahedral substructure and exhibits two three-coordinate and two four-coordinate silicon atoms. The electronic situation on the three-coordinate silicon atoms is rationalized with positive and negative polarization based on EPR analysis, magnetization measurements, and DFT calculations as well as 29 Si CP MAS NMR and multinuclear NMR spectroscopy in solution. Reactivity studies with 1 and radical scavengers confirmed the partial charge separation. Compound 1 reacts with sulfur to give a novel type of silicon sulfur cage compound substituted with an amido ligand, [Si4 S3 {N(SiMe3 )Dipp}4 ] (2).

Microwave-assisted etherification of glycerol with tert-butyl alcohol over amorphous organosilica-aluminum phosphates

The synthesis of organosilica-aluminum phosphates by a simple and cheap sol-gel method was carried out with varying amounts of two different silica precursors, 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane (C) and (3-mercaptopropyl)trimethoxysilane (MPTMS); and several Al/P molar ratios. The solids were calcined in air, at different temperatures. The etherification of glycerol with tert-butyl alcohol was carried out in the liquid-phase under microwave irradiation and also by conventional heating. The incorporation of organosilica in the final solids took place in a 50–60%, as verified by TGA, ICP-MS, XPS and 1H–29Si CP MAS NMR. The highest yield to h-GTBE (21%) was obtained at autogenous pressure, 85°C and 15min of reaction time under microwave, on the solid prepared with 10mmol of C; Al/P=1.5 and calcined at 250°C. This material, with a balanced percentage of mesopores and macropores, also exhibited the highest number of acid sites determined by acid-base titration, as well as by results from TGA and by elemental analysis. The acidity and the hydrophilic character of the solids have been found to be key parameters for the catalytic activity, whereas porosity seems to be advantageous for the reusability of the solids, avoiding deactivation.

Oil loving hydrophobic gels made from glycerol propoxylate: Efficient and reusable sorbents for oil spill clean-up

Glycerol propoxylate based oil loving sorbents were prepared through bulk polymerization, without using of an activator, initiator, or catalyst. Fourier transform infrared spectroscopy (FTIR), 13C and 29Si CPMAS nuclear magnetic resonance (NMR), as well as elemental analysis and thermal gravimetric analysis (TGA) were operated in order to identify the structural and thermal features of sorbents. The synthesized gels were employed as absorbents for various organic solvents and oils. The swelling capacity, absorption-desorption kinetics, reusability, and selective removal from an oil/water mixture were also examined. To explore the effects of a crosslinker's concentration on oil absorption capacity, star type propoxylate monomers were reacted at different concentration of tris[3-(trimethoxysilyl)propyl]isocyanurate (ICS) crosslinker; swelling capacity was calculated using dichloromethane as an organic solvent. Oil removal ability from the water surface is another important section contained within this article.