Mixtures of platinum complexes and tin(II) chloride are effective homogeneous catalysts for the hydrogenation of soybean oil methyl ester, reducing it to the monoene stage only. Hydrogenation and isomerization reactions have been examined under various conditions, using a solvent consisting of 60% benzene and 40% methanol.
The extent of hydrogenation depends upon the temperature (90C>60C>30C) but not upon the pressure (1075 psi as compared with 525 psi). It almost stops after 3 hr, although one double bond remains in the molecule.
After hydrogenation with a catalyst consisting of a mixture of dichloro-bis-triphenylphosphine-platinum(II) and tin(II) chloride, soybean oil methyl ester shows an increase in monoene, a decrease in diene and triene, and formation of conjugatedcis-trans andtrans-trans dienes, but no increase in stearate. Similarly, methyl oleate and methyl linoleate were converted to trans monoene, but not to stearate.
Hydrogenations with mixtures of tetrachloroplatinum(II) ion or hexachloro-platinum(IV) ion and tin(II) chloride were similar to those described above but they form some stearate.
Several other metal ions were studied as replacements for tin. None of them were effective.