An advanced process for producing structurally selective dimer acids to meet new industrial uses

Abstract

Dimer acids are a class of important intermediates that are widely used in many practical applications including polyamides, lubricants, paints, and coatings. They are typically produced through the polymerization (dimerization) of tall oil fatty acids (TOFA) using clays as catalysts. Although this technology is well developed and efficient, the drawback is that the clay catalysts cannot be recycled, generating considerable amounts of hazardous waste. In addition, these products consist of a complex mixture of dimer acids, trimer acids, and polymeric acids. This complexity has limited the ability to thoroughly evaluate their chemical structures. This study reports an advanced recycle zeolite catalysis process using plant-based soybean oil fatty acid (SOFA) which can selectively control the structure formation of the dimer acids and result in yields that are just as efficient as the TOFA technology. The detailed chemical structures of products were thoroughly verified by Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), gas chromatography–mass spectroscopy (GC–MS), and liquid chromatography-mass spectrometry (LC–MS). The reuse process was demonstrated by conducting ten recycle experiments and maintaining high yields, which shows great potential in replacing clay to produce dimer acids. These valuable insights into the structures of the dimer acid products and catalyst reuse results will improve the value and production of dimer acids to meet new industrial uses.