Sk Corporation

Sijoon Lee

Jeong-Soo Kim

Heui-Young Cheong

Byong-Sung Kwak

Young-Seek Yoon

Myung-Jun Kim

Jun-Tae Choi

Disclosed is a method for preparing DL-&agr;-tocopherol through the condensation of isophytol or phytol derivatives and trimethylhydroquinone (TMHQ) using a catalyst system comprising a divalent metal halogen compound, silica gel and/or silica-alumina, and a Br&ouml;nsted acid. Isophytol or phytol derivatives are slowly added to trimethylhydroquinone for the condensation thereof at 80 to 135&deg; C. over 30 to 60 min in the presence of the metal halogen and the silica gel and/or silica-alumina. In the presence of the Br&ouml;nsted acid, the intermediates are converted into the product. The silica gel and/or silica-alumina is washed with a polar solvent for recovery. The catalyst system can remarkably reduce side-reactions upon the condensation of isophytol or phytol derivatives and TMHQ, thus producing DL-&agr;-tocopherol with a high purity at a high yield. Also, the catalyst system can be regenerated in succession because of its being able to avoid the decrease of catalytic activity attributed to the adsorption of organic materials; thus reducing the production cost of DL-&agr;-tocopherol and the quantity of industrial wastes generated. With these advantages, the catalyst system can be effectively used in preparing highly pure DL-&agr;-tocopherol at a high yield on a commercial scale.

Method for preparing DL-&agr;-tocopherol with a high yield and high purity

Disclosed is a method for preparing DL-&agr;-tocopherol with a high yield through the condensation of isophytol or phytol derivatives with trimethylhydroquinone (TMHQ) in the presence of a Zn&mdash;Al heterogeneous catalyst system. At 80 to 120&deg; C., the condensation is carried out for 2 to 7 hours in the presence of a Zn(II) ion-coated alumina-silica catalyst in an n-heptane solvent. The synthetic Zn(II) ion-coated silica-alumina synthetic catalyst system can remarkably reduce side-reactions upon the condensation of isophytol or phytol derivatives and TMHQ, thus producing DL-&agr;-tocopherol with a high purity at a high yield. In addition, the catalyst system is greatly convenient to handle and therefore apply for continuous reactions for the preparation of DL-&agr;-tocopherol. With these advantages, the catalyst system can be effectively used in preparing highly pure DL-&agr;-tocopherol at a high yield on a commercial scale.

Method for preparing DL-&agr;-tocopherol with high yield

The present invention relates to novel alpha-tocopherol cyclopropylates, represented by the following formula I: ##STR1## wherein R.sub.1, R.sub.2, R.sub.2', R.sub.3 and R.sub.3', which may be the same or different, each is a hydrogen atom, a linear or branched C.sub.1 -C.sub.10 alkyl chain, phenyl, acetyl or halogen.

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Taejon, South Korea

Sijoon Lee