A novel microreactor with structured catalytic wall (SCWMR) has been developed for highly exothermic, gas/solid reactions and tested for the selective acetylene hydrogenation. The reactor design is similar to the so-called "slit microreactor". The structured catalyst consisted of Pd-nanoparticie embedded in a thin ionic liquid layer supported on activated carbon fibres (ACF) cloths. It was placed between two aluminium plates forming an empty slit (thickness similar to 300 mu m). The gas mixture flows above the catalyst through the slit allowing a low pressure drop of 15 kPa/m for flows up to 3.3 x 10(-6) m(3)/s. The catalyst can be easily replaced on demand. The acetylene hydrogenation as a model of exothermic reaction was carried out in the SCWMR at conversions up to 100%. The reactor temperature between 150 and 210 degrees C was maintained by circulation of oil from a thermostat and remained constant confirming the efficient heat exchange without hot-spot formation. The reaction performance was optimized varying flow rates and temperatures. The selectivity of similar to 70% was obtained at conversion of 96.5% under steady-state at 200 degrees C without any catalyst deactivation over 10 h on stream. (C) 2010 Elsevier B.V. All rights reserved.