Sol–gel derived organic/inorganic hybrid gels based on poly(2-hydroxyethyl aspartamide) and silica

The sol–gel derived polymer/silicate hybrid materials have attracted considerable attention in recent years. The incorporation of silicate phase into polymeric materials may constitute an important tool to either enhance mechanical properties or provide more biocompatibility to the resulting hybrids. PHEA, α,β-poly(N-2-hydroxyethyl-dl-aspartamide), is a class of poly(amino acid)s that has been widely studied as a biodegradable functional polymer with potential biomedical and pharmaceutical applications. Hydrogels from PHEA are formed easily by a chemical or physical crosslinking reaction but the resulting gels are mechanically weak and less thermally stable. In this study, hybrid materials were prepared based on PHEA and silicate. A sol–gel process was employed using TEOS and modified PHEA to introduce inorganic silicate phase within the polymer gel matrix. FT-IR and NMR were used to analyze the chemical structure of the PHEA derivatives. In addition, the morphology, thermal and swelling properties of the hybrid gels were examined.     

Biodiesel production from soybean oil catalyzed by multifunctionalized Ta2O5/SiO2-[H3PW12O40/R] (R = Me or Ph) hybrid catalyst

Mesoporous Ta₂O₅ materials functionalized with both alkyl group and a Keggin-type heteropoly acid, Ta₂O₅/SiO₂-[H₃PW₁₂O₄₀/R] (R = Me or Ph), was prepared by a single step sol–gel co-condensation method followed by a hydrothermal treatment in the presence of a triblock copolymer surfactant. The catalytic performance of the resulting multifunctionalized organic–inorganic hybrid materials was evaluated by a direct use of soybean oil for biodiesel production in the presence of 20 wt% myristic acid under atmosphere refluxing, and the influences of the catalyst preparation approaches, functional component loadings, and molar ratios of oil to methanol on the catalytic activity of the Ta₂O₅/SiO₂-[H₃PW₁₂O₄₀/R] were studied. In addition, the recyclability of the hybrid materials was evaluated via four catalytic runs. Finally, the network structures of the hybrid materials and the functions of the incorporated alkyl groups on the catalytic activity of the materials were put forward.     

Influence of the Temperature for the Ethanol Oxidation Reaction (EOR) on Pt/C,Pt‐Rh/C and Pt‐Rh‐SnO2/C

The electrocatalytic activity of Pt/C, Pt‐Rh/C and Pt‐Rh‐SnO₂/C electrocatalysts toward the ethanol oxidation reaction (EOR) was investigated in a three‐electrode assembly at 25 °C, 40 °C and 70 °C in acidic medium. The 10 wt.% electrocatalysts were prepared with a modified polyol method and physically characterized by both X‐Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The CO‐stripping study revealed that CO_ad oxidation initiates at lower potential on Pt‐Rh/C and Pt‐Rh‐SnO₂/C than on Pt/C and shifts negatively when the temperature increases. The positive effect of the temperature is maintained for the EOR: the three electrocatalysts exhibit a higher activity and a negative shift of the EOR wave at higher temperature. Pt‐Rh‐SnO₂/C demonstrates the lowest EOR onset potential of the three electrocatalysts. The steady‐state Tafel slopes and apparent activation energies E_a were determined in 0.5 M H₂SO₄ + 0.1 M EtOH between E = 0.4 and 0.7 V vs. RHE in the temperature range 25–70 °C. The results show rather comparable rate determining steps (rds) for the ethanol electrooxidation on Pt/C and Pt‐Rh/C in the ranges of potential and temperature studied. The EOR on Pt‐Rh‐SnO₂/C seems less influenced by the potential than on Pt/C and Pt‐Rh/C electrocatalysts, but is more temperature sensitive.     

Recoverable Palladium Catalysts for Suzuki–Miyaura Cross‐ Coupling Reactions Based on Organic‐Inorganic Hybrid Silica Materials Containing Imidazolium and Dihydroimidazolium Salts

The systems formed by palladium acetate [Pd(OAc)₂] and hybrid silica materials prepared by sol‐gel from monosilylated imidazolium and disilylated dihydroimidazolium salts show catalytic activity in Suzuki–Miyaura cross‐couplings with challenging aryl bromides and chlorides. They are very efficient as recoverable catalysts with aryl bromides. Recycling is also possible with aryl chlorides, although with lower conversions. In situ formation of palladium nanoparticles has been observed in recycling experiments.