Kinetics of CO2 hydrogenation on a K-promoted Fe catalyst

CO2 hydrogenation on a K-promoted Fe catalyst was studied in a fixed-bed microreactor between 300 and 400 degreesC, at 1 MPa, and with modified residence times in the range of 0.042-21.4 g.s/cm(3). For temperatures below 360 degreesC, organic products almost identical with those found in the traditional Fischer-Tropsch reaction with H-2/CO were found (paraffins and alpha -olefins). At 400 degreesC, formation of carbon deposited on the catalyst became a major reaction. Concerning the mechanism of hydrocarbon formation, the effect of residence time resulted in catalyst particle selectivity values for hydrocarbons always higher than zero. This indicates that, besides the two-step reaction mechanism via CO, a direct hydrocarbon formation from CO2 can occur in principle. With a reaction scheme proposed from these experimental results, a kinetic model was developed using integration and regression features of ASPEN PLUS. Calculated values for CO2 conversion and CO and total hydrocarbon selectivities agree with the experimental data within a range of error less than 15%.