Acetone recycling: Do molecular sieves cause acetone breakdown to acetaldehyde?

Abstract

Plastination is a process that is used to preserve biological tissue. In the plastination process, one of the major steps involves dehydrating the tissue with acetone. During this process, large amounts of acetone are used. In order to reduce lab costs, acetone is routinely recycled. This process uses a commercial acetone recycler to remove the majority of impurities that are present in acetone after the dehydration process. Once recycled, the acetone is exposed to molecular sieves in order to remove the water from the acetone. Molecular sieves work by binding to the smaller molecules (water) as the acetone molecules are exposed to them. When exposed to the sieves, the recycled acetone can reach a purity level approaching 100%. The use of molecular sieves in acetone recycling is thought to change the chemical makeup of acetone to acetaldehyde. Acetaldehyde is more reactive than acetone because it has less steric hindrance with the hydrogen compared to the methyl group. Acetaldehyde has a lower melting point (-120℃) and boiling point (20℃) than acetone (Mp -95℃ and Bp 56℃). Because of this phenomenon, it has been recommended that molecular sieves should not be used to recycle acetone. In order to observe the veracity of this assertion, we utilized NMR (nuclear magnetic resonance) to analyze the recycled acetone for the presence of acetaldehyde. The samples used included pure (new) acetone, used acetone before recycling, used acetone after recycling, and used acetone after molecular sieves. From the preliminary and subsequent NMR spectra studies, there were no aldehyde groups present in any of the sample groups. Based on our NMR results, the use of molecular sieves does not appear to alter the chemical makeup of the acetone during the recycling and purification process. Since acetone is not affected by this process, we conclude that the use of molecular sieves is an effective and cost-saving method of acetone recycling for its use in the plastination process.