Catalytic Performance of Nanoscopic, Aluminium Trifluoride- Based Catalysts in the Synthesis of (all-rac)-α-Tocopherol

摘要

A novel nanoscopic, partly hydroxylated aluminium fluoride was prepared in a sol-gel fluori-nation synthesis and characterised by IR probe molecules. It was shown that this material has, in contrast to high surface area aluminium fluoride (HS-AlF3) which is one of the strongest Lewis acids, a low amount of strong Lewis acid sites combined with weak and medium strength Bronsted sites. Both materials were tested in the synthesis of (all-rac)-α-tocopherol through the condensation of 2,3,6-trimethylhydroquinone (TMHQ) with isophy-tol (IP). The activity data indicate the partly hydroxylated aluminium fluoride to be a very efficient and highly selective catalyst for (all-rac)-α-toco-pherol (>99.9%, for an IP conversion of 100%) whereas high surface area aluminium fluoride is a poor catalyst for this reaction.