Feasibility of Reactive Distillation for Fischer−Tropsch Synthesis

Abstract

Fischer-Tropsch synthesis (FTS) is an area that is receiving revived interest worldwide as a technology alternative to produce transportation fuels as well as chemicals from syngas. SASOL and Shell are two of the major players who operate FT reactors on a commercial scale. To have a balance between gasoline and diesel production, one needs to have both the low temperature (LTFT) and high-temperature (HTFT) processes operating in parallel. Heat-removal from the exothermic FT reactions was the main driver in the development of conventional FT reactors (fixed-bed, fluidized bed, or slurry type). However, the focus has recently shifted toward the product distribution as well. Reactive distillation (RD) is a proven reactive separation method that can enhance yields as well as improve product selectivity in multiple reactant/product systems. This paper aims to check if FTS is feasible in RD from a theoretical viewpoint. In-built thermodynamic procedures and power-law kinetics of Aspen Plus, along with a simplified kinetic model that predicts product distribution, were used in performing the simulations. Simulation results of the conventional reactors are compared with RD, and it is seen that the performance of RD is at par or better than the conventional reactors in terms of conversion, yield, and product distribution. Within the RD mode for FTS, results of some of the alternate column configurations are presented. The results indicate that FTS can be a potential candidate to be implemented using RD.

Alcohol promoted methanol synthesis enhanced by adsorption of water and dual catalysts

“…Removal of methanol and water using membrane reactors [38,39] and by condensation at high pressures [40] or low temperatures [41] has been previously described for gas-phase methanol synthesis. Reactive distillation [42] provides a further possible approach for continuous product removal, particularly in liquid-phase processes, and has been proposed in literature for the methanol synthesis process [43] and for the Fischer-Tropsch process [44] operating at similar conditions. In addition, selective removal of water by adsorption on zeolite molecular sieves has also been suggested in sorption-enhanced methanol [45] and related dimethyl ether [46] synthesis operated in the gas-phase.…”

Influence of the Condensable Hydrocarbons on an Integrated Fischer–Tropsch Synthesis and Hydrocracking Process: Simulation and Experimental Validation

“…Caldwell and van Vuuren were the first to consider the importance of VLE in the FTS modeling . Both Raoult’s Law − and more complicated equations of state − were adopted to calculate the VLE. Ideal vapor and liquid phase behavior was proven to describe the FTS system with reasonable accuracy. − More recently, Jess and co-workers also studied the influence of the condensed phase on the reaction performance in FTS and in particular the phenomenon of pore filling by long-chain hydrocarbons. , They found that industrial-size FTS catalyst pellets operate under severe internal diffusion limitation .…”

Equation-Oriented Framework for Optimal Synthesis of Integrated Reactive Distillation Systems for Fischer–Tropsch Processes

“…Srinivas et al modified the kinetic parameters for FT reactions in the model proposed by Wang et al to conform to the Aspen Plus power-law formulation. Both Krishna et al and Srinivas et al fixed the chain growth parameter α in their simulations.…”

“…Similar to RD columns, Maretto and Krishna created a simulation model for a multi-stage bubble column for slurry reactor design and optimization, thus reducing the overall backmixing of the slurry phase; however, the separation process was not included. Srinivas et al − presented several simulation cases by using an Aspen RadFrac module, with built-in thermodynamic procedures, and gradually increased complexity in the kinetic model and column structure. Moreover, Srinivas et al showed that this RD model predicts performance on par with or better than conventional reactors.…”

“…Srinivas et al − presented several simulation cases by using an Aspen RadFrac module, with built-in thermodynamic procedures, and gradually increased complexity in the kinetic model and column structure. Moreover, Srinivas et al showed that this RD model predicts performance on par with or better than conventional reactors. Masuku et al developed a mathematical model to describe the behavior of an FT reactor, and considered the dynamic interaction between reaction and vapor–liquid equilibrium (VLE).…”