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Abstract: We have investigated the preparation, in a direct one-step reaction, of mesoporous and/or macroporous silica materials from the RH 12A(EO)9 surfactant-based system. We have to look at the phase behavior of the RH 12A(EO)9 surfactant in water as well as the effect of the solubilization of various hydrocarbons in this system. The phase diagram proved that hexadecane, decane and cyclohexane can be incorporated into the micelles (L1). Results also show that whatever the liquid crystal phases [direct hexagonal (H1) and lamellar (Lα)] both the swelling and the penetration effects take place upon addition of decane, while only the swelling effect occurs with hexadecane. Moreover, for these two hydrocarbons, at high oil concentration, oil-in-water concentrated emulsion is formulated. The stability of the emulsion is enhanced from days to several weeks with the addition of oil. Starting from the various systems, porous silica materials were then synthesized. The present work shows that in contrary to cyclohexane, hexadecane and decane are effective expanders for the mesopore size enlargement. This suggests that in the micelles hexane and decane form a core of oil, whereas cyclohexane is incorporated between the hydrophobic chains of the surfactant. The variations of the pore diameter upon the addition of oil have been related to the solubilization properties of the oil in the surfactant. Our study also reveals that hydrogenated systems behave as the fluorinated ones, i.e., the formation of macroporous materials templated by emulsions is favored with systems, which exhibit a high value of the PIT. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the phase behavior of the C16(EO)10/decane/water system. Micellar phase (L1), direct hexagonal (H1), cubic (I1) and lamellar liquid crystals were identified. Phase behavior proved that only a weak fraction of oil can be incorporated into the hydrophobic core of micelles (L1). Results also show that whatever the liquid crystal phases both the swelling and the penetration effects take place upon addition of decane. Moreover, at high oil amount, oil-in-water emulsions are formulated. The stability of the emulsion is enhanced from few hours to several months with the addition of oil. Starting from this system, porous silica materials were then synthesized. The present work shows that as long as the decane loading is lower than 7wt.%, decane is an effective expander to enlarge the pore size of mesoporous materials obtained through a CTM-type mechanism. The pore size expansion occurs via the swelling of the surfactant-silica hybrid mesophase. If the concentration of oil is further increased no mesoporous material is recovered anymore, but hollow silica spheres, templated by the oil droplet, are obtained. However, if the amount of oil is too high (>70wt.%) the structure of the hollow spheres collapses and only their fingerprints is still observed. [Copyright &y& Elsevier]

Abstract: In this paper, we report the use of oil/water (O/W) fluorinated emulsions to design macroporous–mesoporous silica with a well-ordered array of mesopores. The emulsion is constituted of fluorocarbon droplets stabilized by the fluorinated surfactant molecules and dispersed in an O/W fluorinated microemulsion. A macroporous texture is clearly evidenced by SEM. The size of the macropores varies from 1.0 to 3.0μm. SAXS patterns of the materials and TEM experiments show that the mesoporous network adopts a hexagonal arrangement. A type IV isotherm is obtained by nitrogen adsorption–desorption analysis. The mesopore size distribution is narrow and centered on about 7.5nm. We also proposed a mechanism to explain the formation of these hierarchically structured macroporous–mesoporous silicas. [Copyright &y& Elsevier]

Abstract: Pore diameter of mesoporous materials has been tailored by adding fluorocarbons as organic auxiliaries. Characterization results show that perfluoroheptane and perfluorodecalin (PFD) can be effectively used as expander. The pore size is increased from 4.0 to 6.8nm. However a transition from a well ordered hexagonal arrangement to a wormhole like structure is detected when the oil loading is higher than 2.5wt.%. Neither the structure nor the pore sizes are influenced by the addition of perfluorooctane. To better understand the influence of these perfluorocarbons and to shed some light on the mechanism of pore size enlargement, we have studied the effect of this fluorocarbon addition on the surfactant phase behavior and the ternary systems have been investigated. Micellar phase (L1), direct hexagonal (H1), cubic (I1) and lamellar liquid crystals were identified. Phase behavior and SAXS measurements proved that only a weak fraction of oil can be incorporated into the hydrophobic core of micelles (L1). However, results also show that the swelling effect of H1 takes place with PFD, whereas the penetration effect occurs with perfluorooctane. [Copyright &y& Elsevier]

Ordered and disordered mesoporous silicas have been synthesized through an assembly of non-ionic decaoxyethylene cetyl ether [C16(EO)10] and a tetramethoxysilane silica source by variation of the pH value of the synthesis gel. The structure, texture and morphology of the mesoporous silicas, synthesized with concentrated and diluted surfactant solutions, have been discussed from the perspective of silica’s chemistry upon a variation of pH values of the synthesis gel (micellar solution). With concentrated surfactant solutions (50 wt%), disordered compounds are obtained in a range of pH from 2.0 to 7.0 (micellar solution). As the pH increases, however, the pore size distributions (PSD) become broader and bimodality appears due to the micelle-templated silica (MTS) mesopores and openings arising from silica dissolution–reprecipitation processes. Also, the MTS pores expand due to a change in conformation of the surfactant hydrophilic head upon pH increase. On the other hand, diluted surfactant solutions (10 wt%) lead to ordered materials in a pH range from 2.0 to 7.0 (synthesis gel). The PSD remain very narrow but interparticular porosity appears and the morphologies undergo deep changes from toroids, gyroids and ropes to aggregates of very small particles with increasing pH. [Copyright &y& Elsevier]

A supported biocatalyst was prepared by immobilization of Mucor miehei lipase onto mesoporous silica materials. This material was used for the synthesis of biodiesel through the transesterification of rapeseed oil with methanol. The process of biodiesel production was optimized by application of the factorial design methodology. Methanol to oil molar ratio, water addition, reaction temperature and biocatalyst content were chosen as the variables and the response selected was the yield of esterification. Oil/methanol ratio was found to have the strongest influence on conversion, a low ratio is more favorable. To increase the enzyme activity water has to be added. However excess of water favors the hydrolysis reaction. The temperature has a slight influence. The optimal conditions for the transesterification are: reaction temperature of 24 °C, alcohol/oil molar ratio of 1:1, and water content of 2.5% w/w. Under these reaction conditions the methanol is totally consumed and around a third of the triglycerides are converted. Nearly 100% of the oil was converted to methyl esters with incremental additions of methanol (three increments of methanol at regular time). [ABSTRACT FROM AUTHOR]

Abstract: In this study, we have investigated the influence of different synthesis parameters such as the pH of the micellar solution, the surfactant/silica precursor molar ratio and the hydrothermal conditions on the properties of mesostructured silica prepared from a nonionic fluorinated surfactant based-system. The recovered materials have been characterized by SAXS measurements, nitrogen adsorption–desorption analysis and scanning electron microscopy. Results clearly evidence that the pH of the micellar solution does not affect significantly the channel array. Nevertheless, a better pore ordering is obtained in very acidic conditions. Another parameter that affects the structure of the recovered material is the surfactant/silica molar ratio. Indeed, the mesopore ordering is detected only for ratios located in the range between 0.4 and 2.5. The optimal ratio has been found equal to 0.5. The last parameters that have been optimized are the hydrothermal temperature and duration. Higher the hydrothermal treatment temperature is lower the time required to obtain a hexagonal mesopore ordering is. The increase of both the duration and the temperature leads to an increase of the pore diameter of the recovered materials due to a thinning of the silica pore walls. A change of the conformation of the hydrophilic surfactant chains is considered to explain the variation of the mesopore diameter. A comparison of the characteristics of the materials obtained with both hydrogenated and fluorinated surfactants is also reported. [Copyright &y& Elsevier]

Aminoacylases (EC 3.5.1.1.4) of Streptomyces ambofaciens ATCC 23877 were immobilized by chemical and physical adsorption onto SBA-15 mesoporous silica materials. The activity of the immobilized aminoacylases was firstly evaluated by considering the hydrolysis reactions of N- α -acetyl-lysine, used as rapid method of screening. After chemical adsorption, a significant loss of activity was observed probably due to a conformational change of the aminoacylases structures upon immobilization. When the immobilization was performed by physisorption a higher amount of enzyme (0.20 against 0.05 mg per mg of support) can be adsorbed onto the mesoporous silica material. The physisorbed biocatalyst also presented a higher hydrolytic activity than the chemisorbed enzyme. Recycling of the supported biocatalysts was performed three times with no loss of the specific activity. Furthermore, a better thermostability was also noted in comparison with free enzyme upon aminoacylases physisorption. Finally, lauroyl-lysine synthesis was catalyzed for the first time by immobilized aminoacylases. The crude extract from S. ambofaciens exhibited the rare ability to catalyze the N-acylation on amino group in the α -position of the lysine whereas the lipase B of Candida antarctica catalyzed the acylation of lysine on its amino group in ε-position. This particular and original regioselectivity was maintained with immobilized enzymes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Physisorption of Mucor Miehei Lipase onto ordered mesoporous silica. [•] High wall thickness is required to protect the support upon enzyme adsorption. [•] Mucor Miehei Lipase adsorption follows Langmuir isotherm. [•] Biocatalyst used for the methanolysis of colza in the absence of nonpolar solvents. [•] Good transesterification yields obtained by the addition of small amounts of water. [ABSTRACT FROM AUTHOR]

Abstract: Herein, we have investigated the solubilization of decane into a novel nonionic gemini surfactant, myristoyl-end capped Jeffamine, synthesized from a polyoxyalkyleneamine (ED900). Starting from this system, porous silica materials have been prepared. Performing the hydrothermal treatment at low temperature, a slight increase of the mesopore diameter is observed in the presence of decane. Increasing the temperature of the hydrothermal treatment, no swelling effect of decane is detected. By contrast, the pore diameter decreases but better mesopore homogeneity and a larger wall thickness are obtained. At high decane concentration the new myristoyl-end capped Jeffamine/decane/water system forms oil-in-water emulsions, which are used as template for the formation of hierarchical porous silica materials. [Copyright &y& Elsevier]

Abstract: In this study, we have investigated the influence of the temperature during the synthesis on the hydrothermal stability of mesostructured silica prepared from a system based on nonionic fluorinated surfactant. Results obtained by SAXS, nitrogen adsorption–desorption analysis and infrared spectroscopy show that when the temperature is increased the hydrothermal stability of the recovered material is enhanced. Indeed, as soon as the treatment into boiling water begins, the structure of the sample synthesized at 80°C is altered, while the material synthesized at 100°C is very stable up to 24h. This behavior has been attributed to a higher degree of silica condensation and to a decrease of both the number of silanol groups and the microporosity. A comparison of the characteristics of the materials obtained with both hydrogenated and fluorinated surfactants also evidences that the lather are more stable when treated with boiling water. [Copyright &y& Elsevier]

In this study, several nanoporous silica of SBA-15 and Aerosil types were impregnated with branched polyethyleneimine (PEI) with the aim to evaluate their iodine adsorption performance. First, the influence of the PEI content of the sorbents on their textural, structural, thermal and chemical characteristics, was studied by different techniques including N 2 porosimetry at 77 K, SAXS, FTIR/ATR, elemental analysis, and TGA. Then, I 2 adsorption capacities were determined in liquid phase (cyclohexane) at 20 °C, or during static or dynamic gas-phase tests, performed at 60 and 100 °C, respectively. An exceptionally high adsorption capacity superior to 2 g/g in the 20–100 °C range was determined for the SBA-15 sorbent with 38 wt% PEI (corresponding to N content of 12.3 wt%). The adsorption capacities of the sorbents increase almost linearly with the N content below this threshold, whereas the presence of excess PEI in the pores or at the pore mouth reduces the accessibility of I 2 molecules to the most buried nitrogen sites. The interaction mechanisms of iodine with amine-containing molecules were investigated both from experiments carried out in solution and from the after-test characterization of the spent solids by DR-UV-Vis, FTIR/ATR, Raman spectroscopies and iodine desorption monitored by TGA. This allowed shedding light on the nature of charge-transfer complexes and the formation of ionic and neutral iodine ad-species during iodine adsorption. Image 1 • PEI/SBA-15 sorbents display very iodine adsorption capacities up to 2 g/g. • Iodine uptakes are correlated with the nitrogen content of PEI/nanosilicas. • Charge-transfer complexes are formed between amine groups and I 2. • Polyiodides formation was evidenced from spectroscopic techniques. [ABSTRACT FROM AUTHOR]