Selective synthesis of camphene from isomerization of α- and β-pinene over heterogeneous catalysts

The selective synthesis of fine chemicals from wasted derived biomass is one of the main challenges for the industry for valorizing and transforming these products into valuable substances. In this work, several materials based on zeolites, titanium dioxide, titanates and molybdenum were tested in the isomerization reaction of biomass derived alpha- and beta-pinene for obtaining camphene, a very high-added value chemical. Liquid phase reaction of alpha- and beta-pinene revealed that zeolites and titanates materials are capable to isomerize both monoterpenes at benign conditions (1 h, 90 degrees C, cyclohexane as solvent); nevertheless, the catalyst based on titanates is suitable for obtaining camphene in the highest yield from both terpenes (77% from alpha-pinene and 67% from beta-pinene). Density of acid sites, Bronsted acid sites and the typical architecture of each catalyst gave significant differences in the catalytic activity. An increase of the Bronsted sites with medium strength favored the yield to camphene. An excess of acidity respect to other materials (e.g. zeolites) increases the formation of secondary products (limonene, pinenes, beta-phellandrene, among others) over camphene, in comparison with titanate catalyst, which shape and acidity is considerably lower. Catalytic isomerization was also explored in essential oils extracted from crude biomass. Camphene weight composition increased in turpentine and Rosmarinus essential oils from 3% to 61% and from 7% to 31%, respectively, in presence of titanates-based material. In addition, this material was also capable to isomerize camphene and limonene into added value chemicals in good to excellent yields. Finally, titanate-based material was reused until 5 times for the selective synthesis of camphene from alpha- and beta-pinene.

Automated summary

Selective synthesis of fine chemicals from wasted derived biomass is a major challenge for the industry, and in this study, materials based on titanates proved to be effective catalysts for isomerization reactions of biomass derived alpha- and beta-pinene to obtain camphene. The density of acid sites, Bronsted acid sites, and catalyst architecture significantly influenced the catalytic activity, with titanate catalyst showing the highest yield for camphene. Furthermore, titanate-based materials were also capable of isomerizing camphene and limonene into valuable chemicals with good to excellent yields.