Comparative Multi-Objective Genetic Algorithm Optimization of Hydrogen Production from Biomethane and Bioethanol in a Non-Isothermal Membrane Reactor

Abstract

This study comparatively investigates hydrogen production from biomethane and bioethanol in a Pd–Ag membrane reactor under identical reactor geometry, catalyst basis, membrane characteristics, and operating conditions. A one-dimensional non-isothermal model was developed in MATLAB, incorporating species balances, an axial energy balance, temperature-dependent reaction kinetics, and selective hydrogen permeation. A Ni/Al₂O₃ catalyst was considered for both fuels, and the feeds were normalized on an equal-carbon basis. The effects of inlet temperature and retentate pressure on fuel conversion, permeated hydrogen production, hydrogen recovery, and carbon-normalized hydrogen production were evaluated. A multi-objective Genetic Algorithm was then applied using inlet temperature, wall-temperature increment, steam-to-carbon ratio, and carbon molar feed rate as decision variables. Under baseline conditions, bioethanol achieved nearly complete conversion compared with approximately 40% for biomethane. Permeated hydrogen production increased from about 1.5 mmol s⁻¹ for biomethane to 4.3 mmol s⁻¹ for bioethanol, while hydrogen recovery increased from about 10% to 14%. Carbon-normalized hydrogen production was approximately 0.15 and 0.43 mol H₂ mol⁻¹ C, respectively. Increasing inlet temperature improved the performance of both fuels, particularly biomethane conversion, whereas pressure mainly enhanced hydrogen permeation and recovery. The Pareto-optimal solutions indicated that bioethanol generally occupied the more favorable performance region, while biomethane exhibited a stronger trade-off between fuel conversion and hydrogen-separation performance.

Keywords

• Hydrogen production
• Membrane reactor
• Biomethane
• Bioethanol
• Genetic Algorithm
• Non-isothermal model

Ethical Statement

Ethics committee approval was not required for this study because of there was no study on animals or humans.

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