Low-Temperature Fischer – Tropsch Synthesis Multiphase Product Recovery through Reactive Distillation

The Fischer­–Tropsch (FT) process relies on a catalyzed chemical reaction to convert synthesis gas into paraffins, olefins, and an appreciable amount of oxygenates. The synthesized FT product slate is remarkable, ranging from C₁ (methane) up to C₇₀₊. The distribution of FT products varies based on reaction conditions (i.e., temperature, pressure, space velocity, and H2/CO ratio), reactor type, and catalyst formulation. We have developed an equation-oriented framework for optimal synthesis of integrated reactive distillation (RD) systems for FT processes in GAMS in which the phase equilibrium is given by a cubic equation of state, the reaction rate expressions are expressed in terms of fugacities, and the product selectivity of catalysts are based on the Anderson–Schulz–Flory distribution and experimental data [1].

In this work, we are expanding the model to consider a more comprehensive kinetic expression with a wider product selectivity to explore the potential of producing a predominantly wax product on a low-temperature FT process, with an expanded model to optimize tray numbers, feed tray location and catalyst loading on trays. We are also implementing the FT-RD optimization model within the PyOMO optimization framework.

The results show that exothermic heat of reaction is sufficient to provide enough vapor load which renders a reboiler unnecessary; and side-streams of high quality gasoline and diesel can be obtained. Thus demonstrating that novel reactive distillation processes are paving the way for a more sustainable chemical process industry that is profitable, safer and less polluting.

[1] Y. Zhang, C.M. Masuku, L.T. Biegler, Equation-oriented framework for optimal synthesis of integrated reactive distillation systems for the Fischer–Tropsch processes, Energy & Fuels 32 (2018) 7199–7209.