Menthol is a leading ingredient for the oral care industry, but is also used extensively in skin care products to soothe and cool the skin. However, due to very high demand, supplies of naturally-sourced menthol are not sustainable.
BASF notes that production of L-Menthol fills this demand, but said it wanted to incorporate a more efficient and sustainable means of manufacturing the ingredient through the design of the its manufacturing facility.
Better manufacturing efficiencies should also help to meet increasing world demand, which is currently estimated at between 25,000 and 35,000 metric tons per year – a figure which already exceeds current supply.
Demand for menthol continues to exceed supply
BASF says that it wanted to increase its production to stay in touch with this demand, which is projected to grow yet further as more and more cosmetic and personal care products incorporate the ingredient into formulations.
Menthol has been manufactured synthetically as L-menthol for around 40 years now, but previous production methods have had their disadvantages, mainly because the processing is a complex multi-step procedure to get the desired flavour and properties.
Likewise, this process also produces a by-product called D-menthol, which for certain derivatives, has to be laboriously separated.
BASF conducted research into this by-product, discovering that it was a variant of the same molecule as L-Menthol, being a mirror image variant that has difference effects on the body, with D-menthol most notably not having the pronounced cooling effect of L-Menthol.
New manufacturing process is based on that of citral
Working on this information, BASF says it has now developed a new process for making synthetic menthol which is based on the aroma chemical citral, which the company already manufactures.
"One of the key steps in the new process is called asymmetric hydrogenation," said BASF research scientist Dr. Rocco Paciello. "For this purpose we have developed a special, highly efficient catalyst system which ensures that mainly just a certain enantiomer is synthesized from the citral."
BASF says that two other synthesis steps are used to produce L-menthol, in a constant process whereby substances can be added and removed without downtime, allowing for a far more simple, and efficient process.
The company also claims that this more resource-efficient process leads to an L-menthol with a purity of at least 99.7 per cent using the same amount of starting materials.
The result is the world’s largest production facility for nature-identical menthol, which will be incorporated into its massive existing facility in Ludwigshafen and is scheduled to be up and running this summer.