Abstract:
We report the synthesis of W-doped biopolymer aerogels with potential applications to catalysis. The
biopolymers were based on alginate, a cost-efficient natural material, and were prepared in environmentally
friendly water/ethanol solutions. Gelation of alginate was induced by crosslinking with Ca2+. The
resulting wet-gels were impregnated with an ethanolic solution of the ditungsten complex
[W2(μ-OEt)2(OEt)2(EtOH)2Cl4] ({W =W}8+) and were dried with supercritical fluid (SCF) CO2 to yield
W-doped alginate aerogels containing 10% w/w tungsten. Dry materials were characterized with FTIR,
SEM/EDS, TGA, N2 porosimetry and He pycnometry. The bulk densities were low (<0.1 g cm-3), porosities
were high (96% v/v), as well as the BET surface areas (380 m2/g). Pyrolysis of those aerogels at 800 oC
under Ar yielded carbon along with a mixture of calcium tungstates, i.e., CaWO4 and Ca3WO6 (weight
ratio: 70:30), while pyrolysis under O2 yielded the same tungstates, but with a different weight ratio
(10:90). This can be a new process for Ca3WO6, which, due to its ordered double perovskite structure,
is ideal for doping with metal ions, at relatively low temperature (800 oC versus >1000 oC in the
literature).
Keywords:
Aerogel, Alginate, Metal–metal bond, Tungstates, Tungsten
Project information:
Deutscher Akademischer AustauschDienst (DAAD) for funding under the Research Stays for University Academics and Scientists, 2017 program (57314019).
Special Account of Research Grants of the National and Kapodistrian University of Athens for partial support.
