“Highly-selective síntesis of menthols from citral in a one-step process

TRASARTI, ANDRÉS; MARCHI, ALBERTO; APESTEGUÍA, CARLOS

París, Francia

Congreso; 13th International Congress on Catalysis; 2004

We report for the first time the selective síntesis of menthols from citral in a one-step process. Bifunctional metal/acid catalysts active and selective for menthol synthesis were developed by studying the individual steps involved in the reaction pathway leading to menthols from citral. The metallic component was selected by testing silica-supported metals (Cu, Co, Pt, Ir, Ni, Pd) for citral hydrogenation to citronelal. Acid site requirements to efficiently isomerize citronelal to isopulegols were investigated on different solid acids (ZnO/SiO2, Cs-HPA, Al-MCM-41, and zeolite Beta). Potential bifunctional metal/acid catalysts were then prepared and tested for the liquid phase citral conversion to menthols. Specifically, Pd or Ni were supported on one of the solid acids more active for converting citronelal to isopulegols (zeolite Beta or Al-MCM-41). The best catalyst was Ni/Al-MCM-41 which yielded 90% menthols and gave about 80% of racemic (±)-menthol into the menthol mixture.