(101c) Optimal Operation of Intensified Fluidized Bed Membrane Reactor for Oxidative Coupling of Methane

The catalytic oxidative coupling of methane (OCM) process has received intense interest in the literature due to the potential to directly convert natural gas or methane to value-added chemicals at a reduced cost, energy consumption and carbon emissions when compared to conventional processes. However, major challenges such as low yield, catalyst deactivation, and reactor scale-up still challenge the commercialization of this process (Galadima & Muraza, 2016; Onoja et al., 2019). A promising solution to address these challenges is to develop innovative OCM reactor designs leveraging the recent advances in modular process intensification, e.g. membrane reactors (Cruellas et.al 2020). While the investigation of OCM reaction systems has mostly been focused on catalyst development and steady-state conceptual designs, ignoring the process dynamics limits the applicability of evaluating the implementation for commercial use (Barteau, 2022). The aim of this work is to design a dynamic optimal OCM process at commercial scale leveraging the concept of modular process intensification.

In this work, we present the new optimal intensified fluidized bed membrane reactor (FBMR) design system for the simulation of oxidative coupling of methane. The conventional fluidized bed reactor was simulated and validated with a C₂+ yield, selectivity, and methane conversion of 15%, 54% and 26% respectively. A membrane was integrated with the conventional reactor by coupling a perovskite oxygen selective membrane along the axial direction to improve on the three key performance indicators mentioned above. The use of membrane for oxygen feed distribution has been reported to result in better C₂+ yield and selectivity by selectively enhancing the desired reactions (Spallina et al., 2015). The FBMR reactor’s design shows a noticeable improvement with a C₂+ yield of 35%, C₂+ selectivity of 67% and improved conversion of methane up to 50% with a reduced CO₂ production by almost 81% (Ali et.al, 2023). Although the new proposed intensified FBMR design solves some of the limitation for the OCM reaction to take place, it opened few research questions to uncover the role of membrane in achieving high C₂+ selectivity%, C₂+ yield% and CH₄ conversion%. The effect of these parameters (e.g. oxygen vacancy dilution coefficient (D_V), species diffusion coefficient (D_i) and perovskite membrane mass transfer coefficients (k_f & k_a)) are investigated to enhance the economics of the OCM reactions and the performance of FBMR. Finally, given the large-scale highly nonlinear nature of the high-fidelity model, a linearized surrogate model is built to balance the computational complexity for model-based control execution and the model accuracy for predictive optimization. The optimal design and operational policy for the FBMR is developed using the PAROC (PARametric Optimization and Control) framework (Pistikopoulos et al., 2015; Pappas et al., 2021). Then, the multi-parametric model predictive control (mp-MPC) problem is solved using the POP toolbox (Pistikopoulos et al., 2020), allowing to analytically derive the optimal explicit operation policy as an affine function of state variables, disturbances, design variables, etc. resulting in enhanced C₂+ yield, selectivity, and CH₄ conversion with guaranteed operational feasibility under disturbances

Keywords: OCM, Process Intensification, Fluidized Bed Membrane Reactors

References

Ali, M.; Tian, Y; Kenefake,D ; Pistikopoulos, E. N. Process Design and Intensification of Circulating Catalytic Fluidized Bed Membrane Reactor for Oxidative Coupling of Methane. ESCAPE-33

Barteau, M. A. (2022). Is it time to stop searching for better catalysts for oxidative coupling of methane? Journal of Catalysis, 408, 173–178.

Cruellas, A., Melchiori, T., Gallucci, F., & van Sint Annaland, M. (2020). Oxidative Coupling of Methane: A Comparison of Different Reactor Configurations. Energy Technology, 8(8), 1–15.

Galadima, A., & Muraza, O. (2016). Revisiting the oxidative coupling of methane to ethylene in the golden period of shale gas: A review. JIEC, 37, 1–13.

Onoja, O. P., Wang, X., & Kechagiopoulos, P. N. (2019). Influencing selectivity in the oxidative coupling of methane by modulating oxygen permeation in a variable thickness membrane reactor. Chem.Eng.Process, 135(2018), 156–167.

Pistikopoulos, E. N., Diangelakis, N. A., Oberdieck, R. (2020). Multi-Parametric Optimization and Control. Vol.1.

Pistikopoulos, E. N., Diangelakis, N. A., Oberdieck, R., Papathanasiou, M. M., Nascu, I., & Sun, M. (2015). PAROC -- An integrated framework and software platform for the optimisation and advanced model-based control of process systems. Chemical Engineering Science, 136, 115–138.

Pappas, I., Kenefake, D., Burnak, B., Avraamidou, S., Ganesh, H. S., Katz, J., Diangelakis, N. A., & Pistikopoulos, E. N. (2021). Multiparametric Programming in Process Systems Engineering: Recent Developments and Path Forward. Frontiers in Chemical Engineering, 2(January), 1–15.

Spallina, V., Melchiori, T., Gallucci, F., & Van Sint Annaland, M. (2015). Auto-thermal reforming using mixed ion-electronic conducting ceramic membranes for a small-scale H2 production plant. Molecules, 20(3), 4998–5023.