1 research outputs found
Hydrogenation of Naturally-Derived Nepetalactone as a Topical Insect Repellent
Dihydronepetalactone
(DHN) is a safe and effective topical insect
repellent,,, comparable
in efficacy to that of <i>N</i>,<i>N</i>-diethyl-<i>m</i>-toluamide (DEET). The latter is the most commonly used
active ingredient, found in many commercial insect repellents for
a broad range of biting insects. DHN can be produced by hydrogenating
nepetalactone (NL), which is the primary ingredient of the essential
oil obtained from the renewably sourced catmint plant, <i>Nepeta
cataria</i>. Optimizing the hydrogenation reaction to produce
DHN from catmint oil is a key economic driver for the process. Prior
to the study described here, Six Sigma methodologies were used to
select palladium on carbon (5% Pd/C) as the catalyst of choice. The
hydrogenation step was studied as a function of critical process variables
and the composition of the oil. As described in this article, a robust,
two-step hydrogenation process was developed to maximize the yield
of the desired DHNs from treated catmint oil. It was observed that
the composition of the catmint oil, vis-à-vis, the relative
amounts of <i>trans–cis</i> and <i>cis–trans</i>-nepetalactone isomers, had a major impact on the activity and selectivity
of the catalyst. This study also focused on minimizing the formation
of a less desirable byproduct, puleganic acid. On the basis of the
process variables tested in this study, temperature was found to have
a strong effect on the activity and selectivity of the catalyst. Higher
pressure enhanced the activity of the catalyst but it did not significantly
impact the formation of undesired byproducts, such as puleganic and
nepetalic acids. Spiking experiments with suspected catalyst poisons,
such as dimethyl sulfide, dimethyl sulfoxide, nepetalic acid, and
puleganic acid were also performed to study catalyst deactivation.
Sulfur was identified as the main factor for the catalyst deactivation.
Possible reaction mechanisms for the formation of less desirable puleganic
and nepetalic acids have been suggested