The absorption of a gas in liquid filled porous particles in gas-solid reactors was studied both theoretically and experimentally. In the theoretical study a micro mode!, describing mass transport accompanied with reaction inside the particles, was implemented in the macro balance for several asymptotic operation modes. The theoretical study showed that the gas separation can be carried out very efficiently with the liquid filled porous particles, especially for the countercurrent mode of operation. The results of the simulations for the removal of H2S from a gas stream also containing CO2showed that a very selective absorption process can be obtained. For these kind of selective absorption processes the simulations showed that the residence time of the particles is a crucial parameter