This paper presents a feasibility study on the development of a gas preconcentrator based on micro-reactor technology on silicon. The objectives are to select a gas adsorbent material, to produce a silicon micro-reactor with an integrated heater, and finally to introduce the most suitableadsorbent into the micro-channels of the device. Preliminary results related to the characterization of a carbon adsorbent for the development of adevice for the preconcentration of benzene are reported. Carbon nano-powders have been tested as adsorbent material by the determination of the breakthrough time on a dedicated test bench consisting of gas sensors and a non-selective photoionization detector (micro-PID) analyzer. A fluidic deposition process allows filling up the silicon micro-channels with the carbon nano-powder. The interest in using porous silicon to enhance the binding of the carbon nano-particles in the micro-channels was also investigated. A silicon micromachined preconcentrator filled with 0.30 mg of commercial activated charcoal powder (Aldrich, 30-100 nm) was designed and built up. The total capacity of adsorption was determined by using the breakthrough time, which is of 2.2 min under a gas flow of 100 ppm of benzene at 1 l/h. Preliminary tests of preconcentration with 100 and 1.3 ppm benzene in dry air were performed.