Researchers reveal new process for making anhydride chemical compounds

Currently in the chemical industry, compounds such as methanol and methyl esters are converted to acetic acid or acetic anhydrides that are eventually incorporated into plastics, fabrics, medicines and other products. Millions of tons of these chemical building blocks are prepared by carbonylation reactions in which a carbon monoxide unit is added to a compound. However, these reactions traditionally rely on expensive and scarce precious metal catalysts such as rhodium and iridium to accelerate the reaction. A new reaction process developed by the team offers a potential alternative.

A new research paper published on Nov. 17 in Science reveals that nickel, when paired with organic imidazole derivatives, is an excellent compound system for carbonylation reactions. Nickel is a much more affordable, abundant and environmentally responsible metal source than rhodium. In previous studies of nickel carbonylation catalysis -- which employed phosphine ligands -- the rate of product formation was low even when large amounts of catalyst and promoters were used.

This combination of nickel with organic imidazole derivatives proved to be an extraordinary catalyst system, with high activity even at low loadings of nickel, ligand and additives. The catalyst system is tolerant to air and can be recharged with carbon monoxide without major losses in activity. Another significant benefit is that nickel costs significantly less than rhodium. For reference, a troy ounce of rhodium can cost as much as a metric ton of nickel. The rates of the new nickel system invite comparisons to current state-of-the-art precious metal catalysts currently used in industry, which opens the door for further exploration and optimization.

The research was supported by funding through a longstanding partnership between UNC-Chapel Hill and Eastman that was established in 2013. Over the past 10 years, Eastman has funded 38 sponsored research projects, totaling over $7 million and spanning five departments at Carolina.