Extrudate versus powder silica alumina as support for Re₂O₇ catalyst in the metathesis of seed oil-derivatives - a comparison

Self- and cross-metathesis of fatty acid methyl esters (FAMEs) was investigated using a silica alumina supported Re(2)O(7) catalyst. Although a 3 wt% Re(2)O(7)/SiO(2)-Al(2)O(3)/SnBu(4) is already active for the metathesis of unsaturated FAMEs, the results have shown that particle size of silica alumina support has a profound influence on its activity and selectivity. Consequently, high substrate conversions coupled with improved product yields (for mono- and diesters) and reaction rates were obtained upon using powder, as opposed to extrudate silica alumina as the support material. Diesters are platform compounds for the synthesis of polymers and fragrances. In this paper a comparative outline of the influence of particle size of silica alumina (extrudate versus powder) on catalytic performance of a 3 wt% Re(2)O(7)/SiO(2)-Al(2)O(3)/SnBu(4) for self- and cross-metathesis of FAMEs is made. Low surface area and diffusion constraints associated with extrudates were identified as some of the factors leading to low catalytic activity and selectivity.