Production of Industrially Useful and Renewable p‐Cymene by Catalytic Dehydration and Isomerization of Perillyl Alcohol

Abstract

We report the dehydration and isomerization of renewable perillyl alcohol to industrially useful p‐cymene in 91% yield utilizing 2.0 mol% para‐toluenesulfonic acid (pTsOH) catalyst at 110 °C as a 3.0 M solution in toluene. Lower reaction temperatures, catalyst loadings, and/or starting concentrations resulted in lower yields of p‐cymene as well as longer reaction times. Conversion of perillyl alcohol to p‐cymene yielded atom and carbon economies of 88.1% and 100% as well as an E‐factor of 2.7, thereby indicating that the process was both green and sustainable. A lower yield of 86% was observed when the reaction was performed neat, but a lower E‐factor of 0.4 indicated that neat conditions were more desirable from an environmental perspective. Application of the optimized parameters to 3.0 M solutions of dl‐limonene led predominantly to oligomerization (92%) as opposed to dehydroisomerization (5%), which was attributed to the strong Brønsted acidity of pTsOH. In addition, camphene (44%), terpinene isomers (15%), and limonene (14%) were obtained when dehydroisomerization was attempted on 3.0 M solutions of α‐ and β‐pinene, which was once again attributed to the acidity of the catalyst. Oligomerization was strongly favored when dehydroisomerization of dl‐limonene, α‐ and β‐pinene was attempted neat. In summary, synthesis of renewable p‐cymene was readily achieved from perillyl alcohol with catalytic pTsOH but competing side reactions suppressed yield when dehydroisomerization of dl‐limonene, α‐ and β‐pinene was attempted due to the strong Brønsted acidity of the catalyst.

Precipitation of Polypropylene and Polyethylene Terephthalate Powders Using Green Solvents via Temperature and Antisolvent-Induced Phase Separation

“…Additionally, most of the chosen solvents can be considered as green solvents. As it is directly available in a variety of plants, p-cymene has been shown to be producible via processing of α-limonene from citrus waste material [53][54][55] as well as other sources like eucalyptus oil [56] and perillyl alcohol [57]. Dibutoxymethane, a common additive for biodiesel, can be produced from butanol and formaldehyde [58,59].…”