Oxidative desulfurization of fuels using alcohol-based DESs

Area of Science:

• Environmental Chemistry
• Green Chemistry
• Petroleum Engineering

Background:

• Sulfur compounds in fuel oil release toxic sulfur dioxide, a major global environmental concern.
• Conventional hydrodesulfurization (HDS) is insufficient for removing refractory sulfur compounds like benzothiophene (BT), dibenzothiophene (DBT), and 4-methyldibenzothiophene (4-MDBT).
• Development of advanced desulfurization techniques is crucial for cleaner fuel production.

Purpose of the Study:

• To synthesize and characterize novel deep eutectic solvents (DES) for enhanced fuel desulfurization.
• To evaluate the efficiency of synthesized DESs in extracting refractory sulfur compounds from model and diesel fuels.
• To investigate the combined effect of DES extraction and oxidative desulfurization for deep sulfur removal.

Main Methods:

• Synthesis of various DESs using different hydrogen bond acceptors (e.g., citric acid, adipic acid) and donors (e.g., triethylene glycol - TEG).
• Characterization of DES properties including density, viscosity, refractive index, and FTIR spectra.
• Extraction of sulfur compounds from model oil and diesel fuel using selected DESs, followed by oxidative desulfurization using hydrogen peroxide.

Main Results:

• The DES formulations [citric acid: TEG] [1:7] and [adipic acid: TEG] [1:8] demonstrated significant sulfur removal efficiencies.
• Single-stage extraction at 30°C removed up to 44.07% and 42.53% sulfur from model oil, respectively.
• Successive extraction increased removal to over 85%, while oxidative extraction achieved efficiencies up to 98.98% for [citric acid: TEG] [1:7] and 96.96% for [adipic acid: TEG] [1:8] from model oil containing DBT.

Conclusions:

• Deep eutectic solvents, particularly [citric acid: TEG] [1:7], show superior performance in deep desulfurization of fuels.
• The combination of DES extraction and oxidative desulfurization offers a highly efficient and promising method for removing refractory sulfur compounds.
• These findings present a viable, eco-friendly alternative to conventional HDS for producing ultra-low sulfur fuels.