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

Abstract

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 α- and β-pinene for obtaining camphene, a very high-added value chemical. Liquid phase reaction of α- and β-pinene revealed that zeolites and titanates materials are capable to isomerize both monoterpenes at benign conditions (1 h, 90 °C, cyclohexane as solvent); nevertheless, the catalyst based on titanates is suitable for obtaining camphene in the highest yield from both terpenes (77% from α-pinene and 67% from β-pinene). Density of acid sites, Brønsted acid sites and the typical architecture of each catalyst gave significant differences in the catalytic activity. An increase of the Brønsted 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, β-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 α- and β-pinene. • Acid curl sheets titanates capable to isomerize α- and β-pinene into camphene. • Selective production of camphene from Rosmarinus and Turpentine essential oils. • Medium Brönsted acid sites of titanates abled the isomerization. • Strong acid sites in zeolites produce a complex mixture of pinenes isomers. • Titanates also isomerize limonene and camphene into value products.