Rachida Hamacha

Assessment of the intrinsic interactions of mesoporous silica with carbon dioxide

Three mesoporous silica, SBA-16, SBA-15 and MCM-41, with different structures and porosities were synthesized via a hydrothermal method and their interactions with carbon dioxide (CO2) were investigated through thermal programmed desorption (TPD) and differential scanning calorimetry. TPD measurements provided precise assessments of the intrinsic affinity towards CO2, without the influence of moisture. All silica materials were found to exhibit intrinsic affinity towards carbon dioxide, but the surface basicity, expressed in terms of retained CO2 amount, is markedly influenced by increases in pore size and framework structures. SBA-15 displayed the highest CRC values, explained in terms of larger pore size, lower numbers of acidic out-of plane Si–OH and higher numbers of much less acidic in-plane silanols. These findings provide valuable information for a better understanding of the role of the silica structure in the intrinsic basicity, prior to further modifications for improving the affinity towards CO2 or merely for catalysis purposes involving CO2 as reagents, intermediates or products.

Enhanced hydrogen storage capacity of copper containing mesoporous silicas prepared using different methods

This paper focuses on the synthesis of mesoporous materials, Al-MCM-41, doped with copper using different methods. The results show that the method of synthesis affects the structural and textural properties of these solids. Their application in hydrogen storage shows that the adsorption is enhanced when using a solid containing Cu+2 ions, with an adsorption capacity around 1.8 wt% at 77 K, while the solids containing CuO particles present a medium adsorption capacity. Temperature variation plays a very important role in determining the adsorption capacity and the best results are obtained at 77 K.

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 Brønsted acid properties with an interesting activity leading to yields of ~90% of biodiesel.Graphical Abstract

CuCO3–CuO nanocomposite as a novel and environmentally friendly catalyst for triazole synthesis

This paper focuses on the use of natural sources for the preparation of efficient and low cost catalysts. CaCO3 is obtained from cuttlefish bone and was modified by the cation exchange of Ca2+ by Cu2+ in CaCO3 using solutions of copper (Cu(NO3)2) at different concentrations. The modification of the solids was investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and ultraviolet-visible (UV-vis) spectroscopy. The results show that the copper exchanged materials contain a CuCO3–CuO nanoparticle composite. The obtained solids were used as catalysts for the cycloaddition reaction of different azides with activated alkenes at room temperature under liquid phase conditions. The different parameters which affect the reaction were investigated such as reaction time, temperature of the reaction, effect of the copper content, catalyst mass, effect of the solvent and nature of the azide. High yields were obtained when the catalyst contained more copper. The best catalysts were calcined at different temperatures (200, 300, 400, 500 °C) in order to determine whether the active phase was CuCO3 or CuO in the catalytic reaction. The XRD analysis of the calcined composites shows that an increase in calcination temperature leads to the formation of the CuO phase. On the other hand, the use of these calcined materials as catalysts shows that the active phase is copper carbonate. Finally, a new method for preparing triazoles with short reaction times was developed by the use of a cheap environmentally friendly catalyst.