The preparation of lignocellulosic aerogels from ionic liquid solutions

Nanofibrillar aerogels were prepared from cellulose, spruce wood and from mixtures of cellulose, lignin and xylan. The lignocellulosic polymers were first dissolved in an ionic liquid and coagulated from solution by adding aqueous ethanol. The obtained gel was washed with ethanol and liquid carbon dioxide and finally dried by releasing the carbon dioxide from the porous structure at supercritical temperature to obtain the aerogel. The bulk densities of the biopolymer aerogels ranged from 25 to 114 g/l and the internal surface areas (BET) from 108 to 539 m2/g depending on the biopolymer mix and on the polymer concentration in the ionic liquid solution. All aerogels were compressible and consisted of nanofibrillar biomaterial network with open-pore structure.