Hydrogen Bonds in Disulfonic-Functionalized Acid Ionic Liquids for Efficient Biodiesel Synthesis

Area of Science:

• Green Chemistry and Catalysis
• Materials Science
• Chemical Engineering

Background:

• Optimizing hydrogen bond states in ionic liquids (ILs) is crucial for enhancing their catalytic efficiency.
• Disulfonic-functionalized acidic ionic liquids (DSFAILs) represent a promising class of catalysts for various chemical transformations.

Purpose of the Study:

• To synthesize novel disulfonic-functionalized acidic ionic liquids (DSFAILs) and evaluate their catalytic performance in biodiesel synthesis.
• To investigate the structure-activity relationship of DSFAILs, focusing on the role of hydrogen bonding and acidity.
• To explore the potential of DSFAILs as efficient and recyclable catalysts for methyl oleate production.

Main Methods:

• Synthesis of novel SO3H-functionalized binuclear IL (bis[3-(CH2)3SO3H-1-(CH2)2-Im][HSO4]2) and other DSFAILs.
• Catalytic evaluation of DSFAILs for methyl oleate synthesis under mild reaction conditions.
• Density Functional Theory (DFT) calculations to elucidate the role of hydrogen bonds and active sites.
• Analysis of catalyst recyclability and stability.

Main Results:

• DSFAILs, particularly [Im(N(CH2)3SO3H)2][HSO4], exhibited higher catalytic activity than traditional ILs for biodiesel synthesis.
• DFT studies revealed that hydrogen bond states and deep ionization significantly influence the acidity and catalytic performance of DSFAILs.
• The optimal catalyst ([Im(N(CH2)3SO3H)2][HSO4]) achieved a 93% methyl oleate yield at 353 K with 6 wt% catalyst loading and retained 90% yield after six recycles.

Conclusions:

• The structure-activity relationship between DSFAILs and methyl oleate synthesis was established, highlighting the importance of acidity and steric hindrance.
• The catalyst bis[3-(CH2)3SO3H-1-(CH2)2-Im][HSO4]2 demonstrated ease of separation due to its higher molecular weight.
• [Im(N(CH2)3SO3H)2][HSO4] proved to be the optimal catalyst, offering superior activity and recyclability for efficient methyl oleate synthesis.