Development of a Kinetic Model for Supercritical Fluids Fischer−Tropsch Synthesis

Abstract

Kinetic models for Fischer-Tropsch synthesis (FTS) were derived to express the reaction behavior in either conventional reaction media (gas-phase) or nonconventional media (near-critical and supercritical solvent media). These models we developed from experimental data generated from a commercial alumina supported cobalt catalyst (15% Co/Al 2 O 3 ) in a fixed bed reactor. Two models were developed: the first one assumes ideal gas phase behavior for the gas phase reaction and uses partial pressures to express reactant and product concentrations in rate expressions while the second model accounts for the nonideal behavior of the reaction mixture under elevated pressures via the utilization of fugacity parameters and fugacity coefficients. The fugacity coefficients were estimated from a modified Redlich-Kwong-Soave equation of state. A comparison was conducted between the estimated kinetic parameters from the fugacity-based kinetic model and the partial pressure based kinetic model. The heat of adsorption of carbon monoxide and hydrogen was calculated from the estimated kinetic parameters and an attempt was made for qualitative analysis of mechanistic details of the reaction in both near critical and supercritical FTS and gas-phase FTS. It was observed that the fugacity-based models more accurately predict the carbon monoxide consumption rates in the gas phase as well as in near critical and supercritical FTS conditions. Similarly, the fugacity-based model was found to successfully predict the methane formation rates for both gas phase FTS and the near critical and supercritical phase FTS.

Characterization of Modified Fischer–Tropsch Catalysts Promoted with Alkaline Metals for Higher Alcohol Synthesis

“…The highest selectivity towards hydrocarbons corresponds to CuCoCrZnLi at 300°C and to CuCoCrLi at 350°C. Sodium as promoter may contribute to the growth of saturated chain and also activate oxygen elimination via H 2 O followed oxygenates products [1][2][3][4][5][6][7]. This is confirmed by the low yields of CO 2 and the high amounts of methanol obtained at 300°C over CuCoCrNa and at 350°C over CuCoCrZnNa.…”

“…Fischer-Tropsch (F-T) hydrocarbon synthesis is an exothermic reaction over catalysts containing transition metals or their compounds consisting in adsorption of carbon monoxide (CO) on catalyst surface followed by its disproportionation in order to obtain an active form of carbon previous to its hydrogenation [1,2]. The excess of oxygen is removes from the catalyst surface via CO 2 or H 2 O [1][2][3][4][5][6][7].…”

“…The excess of oxygen is removes from the catalyst surface via CO 2 or H 2 O [1][2][3][4][5][6][7]. This mechanism works well within a narrow temperature range, 500-700K, producing low-molecular-weight hydrocarbons and small amounts of high-molecular-weight hydrocarbons as well as oxygenates [3].…”

Probabilistic assessment of the safety profile of the Fischer–Tropsch process with a supercritical solvent

“…Studies in the literature have supported the superior performance of SCS over the traditional routes. [32] Those studies have shown that SCSs offer high diffusivities, high solubilities, and better management of heat transfer properties than conventional processes. [7,9,30,33] Given the high operating conditions of the system, one special concern about FTS with the use of SCS (FTS-SCS) is the safety of the process.…”

Modeling Fischer-Tropsch Product Distribution of a Cobalt-based Catalyst in Different Reaction Media

“…is a challenge. Mogalicherla and Elbashir [36] developed kinetic models for FT in supercritical fluids. CO conversion and CH4 yield could be estimated from the isothermal plug flow reactor models.…”