Mesocellular Silica Foams (MCFs) with Tunable Pore Size as a Support for Lysozyme Immobilization: Adsorption Equilibrium and Kinetics, Biocomposite Properties

The effect of the porous structure of mesocellular silica foams (MCFs) on the lysozyme (LYS) adsorption capacity, as well as the rate, was studied to design the effective sorbent for potential applications as the carriers of biomolecules. The structural (N2 adsorption/desorption isotherms), textural (SEM, TEM), acid-base (potentiometric titration), adsorption properties, and thermal characteristics of the obtained lysozyme/silica composites were studied. The protein adsorption equilibrium and kinetics showed significant dependence on silica pore size. For instance, LYS adsorption uptake on MCF-6.4 support (pore diameter 6.4 nm) was about 0.29 g/g. The equilibrium loading amount of LYS on MCF-14.5 material (pore size 14.5 nm) increased to 0.55 g/g. However, when the pore diameter was larger than 14.5 nm, the LYS adsorption value systematically decreased with increasing pore size (e.g., for MCF-30.1 was only 0.27 g/g). The electrostatic attractive interactions between the positively charged lysozyme (at pH = 7.4) and the negatively charged silica played a significant role in the immobilization process. The differences in protein adsorption and surface morphology for the biocomposites of various pore sizes were found. The thermal behavior of the studied bio/systems was conducted by TG/DSC/FTIR/MS coupled method. It was found that the thermal degradation of lysozyme/silica composites was a double-stage process in the temperature range 165–420–830 °C.

Influence of synthesis parameters of mesocellular silica foams doped by nickel on methane reforming by CO2

New catalysts based on Ni(0) dispersed onto mesocellular silica foams (MCF) were prepared for Dry Reforming of Methane (DRM). Different synthesis methods of MCF supports (with and without using NH4F or n-butanol) were tested in order to study the influence of the textural properties of the support on the catalytic performances of the catalysts. In all cases, nickel was incorporated using the double solvents method. The resulting calcined materials were characterized by N2 sorption, X-Ray diffraction (XRD) and transmission electron microscopy. Their reducibility was tested by temperature-programmed reduction (TPR). Interestingly, particularly large specific surfaces, pores diameters and pores volumes were observed when NH4F was added to the synthesis gel (MCF(N) materials). The corresponding Ni-MCF(N) catalysts were shown to be the most attractive among other prepared samples with respect to their performances in DRM.