Biopolymer-Based Carbon Aerogels in Catalysis
Porous carbon materials are widely used as catalyst supports in heterogeneous catalysis. The most common support is carbon black, which is produced by the catalytic cracking of petroleum fractions in refineries. Carbon black consists of non‑porous spherical particles with diameters ranging from 10 to 500 nm; its specific surface area increases as particle size decreases.
Carbon aerogels (CAs), derived from biopolymer aerogels, provide a greener alternative. Even when the particle size reaches the millimetre scale, CAs exhibit surface areas of 1 000–3 000 m² g⁻¹, comparable to those of activated carbons. Unlike activated carbons, which are predominantly microporous (< 2 nm), CAs contain a substantial fraction of mesopores (2–50 nm). The presence of mesoporosity facilitates mass transport within the material while still offering abundant anchoring sites for catalyst nanoparticles—typically metals.
Catalyst loading onto carbon aerogels can be achieved by several methods:
- Supercritical deposition – yields highly homogeneous loading and a narrow particle‑size distribution; however, it requires an autoclave operating at 155 bar.
- Wet impregnation – performed under ambient conditions in organic solvents; the resulting loading is less uniform and the particle size distribution broader.
- In‑situ formation – the catalyst precursor is incorporated during the hydrogel/alcogel stage and reduced to metal nanoparticles during pyrolysis, enabling a one‑pot synthesis. In this approach, the final CA structure and nanoparticle formation are coupled through the pyrolysis conditions.
These methods allow tailoring of catalyst loading characteristics for specific applications.
