Unpromoted and Mn‐Promoted Cobalt Catalyst Supported on Carbon Nanotubes for Fischer‐Tropsch Synthesis

Abstract

Langmuir‐Hinselwood (LH) and power rate equations were applied to describe the kinetics of the Fischer‐Tropsch reaction on cobalt catalysts and manganese‐doped cobalt catalysts supported on carbon nanotubes (CNTs). LH‐based kinetics characterize the activity behavior of the unpromoted Co/CNT system satisfactorily, but fail with respect to the manganese‐promoted Co/CNT catalyst. An alternative LH equation is able to fit the experimental data, but the fitting parameters are out of the range of usual values and underrate the activity at ambient pressure regardless of manganese promotion. Application of power law rate expressions results in satisfying characterization of the kinetics in the whole CO pressure range in the promoted case and within a defined range of CO pressure in the unpromoted case.

Cobalt catalysts on carbon-based materials for Fischer-Tropsch synthesis: a review

“…From an engineering and industrial point of view, it is important to establish kinetic rate equations integrating the performance and the scale-up of the process e.g., reactor modeling and process modeling [59]. Kinetic rate equations are most of the time described by empirical power law models based on Langmuir-Hinshelwood-type equations [60].…”

“…Based on the power law model, they concluded that CO is strongly adsorbed dissociatively on the catalyst surface, and the reaction rate is significantly influenced by the partial pressure of H2. In another study, Rose et al [59] used Langmuir-Hinshelwood and power rate equations (Eq.5) to describe the kinetics of FTS reaction on cobalt catalysts and manganese-doped cobalt catalysts supported on CNTox. This study was carried out in a wide range of pressure and temperature, since the FTS activity and selectivity strongly depend on the syngas pressure and temperature.…”

“…This study was carried out in a wide range of pressure and temperature, since the FTS activity and selectivity strongly depend on the syngas pressure and temperature. In order to better predict the evolution of the activity as a function of the CO concentration over Co/CNTox catalysts three kinetic expressions including power law rate expressions (Eqs.6-7), rate expressions by Yates and Satterfield (Eq.8), and rate expressions by Rautavuoma and Van der Baan (Eq.9) were applied [59]. It was found that the activity at 1 bar of H2/CO was significantly higher than that predicted by the models (Figure 3).…”

“…In Eqs. 5-9, denotes the molar flow of reactant, 1 the apparent (first-order) rate constant, the rate expression, the mass of active metal in the cobalt catalyst, c the respective concentration of CO and H2, is the equilibrium constant, and are the order of carbon monoxide and hydrogen, respectively, RB is the Rautavuoma and Van der Baan, and YS is the Yates and Satterfield constants , ̇ is the molar flow [59]. 6) and ( 7)) and both Langmuir-Hinshelwood models (Yates and Satterfield (Eq.…”

Heterogeneous Catalysis on Nanostructured Carbon Material Supported Catalysts

“…Langmuir-Hinshelwood (LH) and power rate equations were applied to describe the kinetics of the FT reaction on cobalt catalysts and manganese-doped cobalt catalysts supported on CNTs. 190 LH-based kinetics characterize the activity behavior of the unpromoted Co/CNT system satisfactorily, but fail with respect to the Mn-promoted Co/CNT catalyst. An extensive study of FTS on CNT supported and γ-alumina-supported cobalt catalysts with different amounts of cobalt was reported.…”