Polymeric and Hybrid Membranes for Achieving Ultra-Low Sulfur Fuel Requirements

Abstract

This review aims to explore membrane-based alternative methods for removing harmful sulfur compounds in fuels to replace the inefficient conventional techniques. Membrane-based methods provide an efficient route to achieve very low sulfur content in fuels (< 10 ppm), as required by international environmental policies. A systematic review of 42 experimental studies reported over the period from 2005 to 2025, being the timeframe that would most likely encompass an actual paradigm change in membrane-based technologies. The data were retrieved from scientific databases, including Scopus, Web of Science, ScienceDirect, and ACS, to evaluate the performance of polymer and composite membranes for desulfurization. Innovative membrane systems like polydimethylsiloxane (PDMS), polyethylene glycol (PEG), polyimide, and mixed-layer membranes (MMMs) were found to be highly effective in both evaporation- and permeability-based desulfurization processes. PEG-PI MMMs reinforced with metal organic frameworks (MOFs) demonstrated removal efficiencies as high as 80% and a permeability of > 200 g/m2·h, which were significantly higher compared to that for neat polymeric membranes. The key separation principles include diffusion-dissolution, facilitated transport with π complexes (Ag+, Cu2+, MOFs), and molecular sieving. Finally, in spite of challenges such as polymer swelling and stability remaining, polyethylene glycol (PEG) and polyimide (PI)- MMMs, especially those enhanced with metal-organic frameworks (MOFs), stand out as strategic industrial candidates due to the best balance of flow, selectivity, and stability. The future direction must urgently focus on long-term stability testing using real fuel streams rather than model fuels to confirm the practical viability of these integrated membranes.