Kinetics of CO₂ Hydrogenation on a K-Promoted Fe Catalyst

Abstract

CO 2 hydrogenation on a K-promoted Fe catalyst was studied in a fixed-bed microreactor between 300 and 400 °C, at 1 MPa, and with modified residence times in the range of 0.042-21.4 g‚s/ cm 3 . For temperatures below 360 °C, organic products almost identical with those found in the traditional Fischer-Tropsch reaction with H 2 /CO were found (paraffins and R-olefins). At 400 °C, 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 CO 2 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 CO 2 conversion and CO and total hydrocarbon selectivities agree with the experimental data within a range of error less than 15%.

Fischer‐Tropsch Catalysts for the Biomass‐to‐Liquid (BTL)‐Process

“…CO 2 can also be regarded as an inert in the feed for both cobalt-based FischerTropsch synthesis [8,9] and Fe-based Fischer-Tropsch synthe-sis operating at low temperatures [8,10], if sufficient CO is still present. There is some indication of direct conversion of CO 2 over an Fe-based catalyst at very low CO concentrations [11]. The resulting synthesis gas from biomass gasification upon steam reforming of methane and after removal of carbon dioxide (e.g.…”

Effect of support of Co-Na-Mo catalysts on the direct conversion of CO2 to hydrocarbons

“…7 However, they normally present poor activity in the first CO2 hydrogenation step. 8 Additionally, when CO2 is added to a CO/H2 stream, the hydrocarbon distribution is strongly affected with a shift in selectivity towards undesired products such as methane. 5,9 When the feed-gas is completely shifted to a CO2/H2 mixture, cobalt systems tend to act as methanation catalysts with almost exclusively (generally >90 %) methane formed.…”

The Virtuous CO2 Circle or the Three Cs: Capture, Cache, and Convert

“…The RWGS is an endothermic process, which requires high temperatures, and the conversion is equilibrium limited. The efforts on process development must focus on the optimization of active catalysts to contrast the slow kinetics and to ensure that the CO is produced at the maximum possible yield [94]. Recently, nickel supported on nanostructured oxides such as cerium oxides nanocubes [76] or mesophorous cerium oxide [77] (Figure 10) was studied as a promising material to overcome the previous problems, combining the good performance as hydrogenation catalyst of nickel with the oxygen coordination capability of ceria.…”