The present research work is focused on the kinetic and mechanistic studies of the Fischer-Tropsch synthesis in a fixed bed micro reactor; over the nano-structured iron-cobalt-manganese catalyst prepared by hydrothermal procedure. Experimental conditions within the reactor were varied as follows: T = 265-330 degrees C, P = 1.2-10 bar, H-2/CO feed ratio = 0.5-2 and GHSV = 4200 h(-1). Based on Langmuir-Hins helwood-Hogan-Watson and Eley-Rideal adsorption theories in catalytic processes, 18 kinetic models for CO consumption were tested and interaction between dissociative adsorbed carbon monoxide and dissociative adsorbed hydrogen as the rate-determining step gave the best fitted kinetic model (-r(co) (=) k(p)b(co)P(co) (bH(2)PH(2))(2) / (1+2(b(co)P(co))(0.5)+(bH(2)PH(2))(0.5))(6) ) The Levenberg-Marquardt algorithm was used to estimate the kinetic parameters and the obtained activation energy was 85.1814/n1 1 for the optimal kinetic model. Characterization of catalysts was performed using XRD, FESEM, EDS, TEM and the N2 adsorption-desorption measurements such as BET and BJH methods. (C) 2017 Elsevier Ltd. All rights reserved.