Sulfuric acid, p-toluene sulfonic acid, siIica gel; alumina gel, aluminum oxide and powdered aluminum were used as catalyst for the preparation of dioctyl phtbafate .by direct esterification.The effect of these was carefulfy studied. When suIfuric acid or p-toIuene sulfonic acid was used as catalyst, benzene,. toluene, or' Iow boiling fraction of gasoline, was added to the reaction mixture for the removal of water, a yieId as high as 95% was attainad by using 2-3% of cataIyst and 1596 excess of octyl aIcohof.In the case of solid catdyst, powdered aluminum was most satisfactory, the amount of catalyst used being 59&, 92-93?? yield was attained.
No solvent was used.A =eat number of plasticizals have been developed in recent years for the rnmufacture of ptasfics. Among '&ase dioctyl pbthalate is the commonest and generally proved to be most satisfactoryc~s>. It is commercially prepared from phthalic anhydride and octyl alcohol.In the author's laboratory, p h b l i c anhydride has been succcssfully produced by the oxidation of nz@MtaleneC~)9 m d cmyl alcoholr by the Guerbet reactiop from butanoP. .In the esterification process, the successfulness depends largely on the rapidity of removal of water produced. It is also depeqdbgg on u e mtme of the cataIyst u~e d c s~~~> .The wata produced duripg the reaction can. be carried away by heating with berzzener't,, toXueneQ0), or xylem(z), previously added to the reaction mixture, in a specially co~,~tructed apparatus.Sulfuric acid is usually used as caalyst in the esterificationfaln), but it is not fecommended €or the estdfication of hi&er alco&ols,