Fabrication and characterisation of microporous activated carbon-based pre-concentrators for benzene vapours

During the last years, the use of gas pre-concentrators coupled to gas sensors became more important due to the difficulty of fabricating gas sensors with sensitivities in the range of tens of ppb (or lower). Among the different adsorbents used in pre-concentrators, carbons are the most usual, since they are very common materials in chemistry, and because their adsorption performances are very high. In the present work, a family of microporous activated carbons prepared from chemical activation of Kraft lignin was used as adsorbents, and compared with a commercial material. The carbonaceous adsorbents were sprinkled onto self-heated alumina substrates using a binding layer deposited by screen-printing. Their characterisation was performed by means of a GC–MS with a 6-way valve injection system. Concentration factors higher than 1000 for benzene have been achieved with some particular adsorbents. In the present work, the microporous activated carbons and Carbopack have been adhered over the self-heated surface of pre-concentrators. The performances obtained for all the microporous activated carbons are much higher than those obtained with the commercial carbon black Carbopack X, so these lab-made materials are very promising adsorbents for micro pre-concentrators, which could be used in conjunction with sensors in gas detection systems.