Hydroformylation Of Phenyl Olefins Catalyzed By Water-Soluble Rhodium Phosphine Complex

Hydroformylation is a typical atom economical reaction, to which great attention has been attached since Wilkinson catalyst was discovered in the 1960s. The idea of biphasic (aqueous/organic) catalysis, which simplifies the separation of catalyst from products by decantation and facilitates catalysts recycling, is progressing quickly recently. The replacement of organic solvents by water is also advantageous for environmental, safety and economical reasons. Biphasic catalysis relies on the transfer of organic substrates into the aqueous phase containing the catalyst or the interphase layer. In this paper, the hydroformylation of five phenyl olefins catalyzed by water-soluble rhodium complex was studied. The main works include:1: styrene hydroformylation catalyzed by water-soluble rhodium complex RliCl(CO)(TPPTS)2[TPPTS:P(m-C6H4SO3Na)3], in the presence of cationic surfactants TBAC [TBAC: Tetradecylbenzyldimethylammontum chloride] or other surfactant was studied. The effect of the reaction conditions, such as concentration of surfactant and rhodium complex, temperature, syngas pressure and the mole ratio of phosphine to rhodium on the activity and selectivity was investigated. The results indicated that the hydroformylation in biphsasic catalytic system occurred in the interface of aqueous/organic phase. The cationic surfactants could obviously accelerate the reaction rate in the several different surfactants but TBAC was better than others.The formation of micelle was not only favorable for the reaction acceleration, but also favorable for the increase of linear aldehyde ratio in products. The key factor of the enhancement of reaction rate was the richness of rhodium catalyst in the interlayer with the electrostatic attraction between active rhodium anion species and cationic end ofsurfactant.The mixed micelle formed by cationic surfactant TBAC and anion surfactant SDS [SDS: Sodium dodecyl sulfate] exhibited more excellent properties in the acceleration of the reaction rate and promoted the formation of normal phenyl propanal. In styrene hydroformylation Under the optimum reaction conditions: 90, P=2.0Mpa, TBAC/SDS=12 (mole ratio), Vaque0us/V0iefin=3, the conversion of styrene reached to 98.3% for two hours and the mole ratio of iso/normal aldehyde was 1.30 (normal phenyl propanal was 43.5%). When the temperature increased to 110 and the syngas pressure decreased to 0.5 Mpa (constant pressure), the content of normal phenyl propanal in the products could reached to 69%.The hydroformylation of five different phenyl olefins, such as styrene(l) , allylbenzene(2) , 4-allylanisole(3), safrole(4) and isosafrole(5), in the water/organic biphasic catalytic system, containing water-soluble rhodium-phosphine complex RhCl(CO)(TPPTS)2 [TPPTS:P(m-C6H4SO3Na)3], phosphine ligands TPPTS, and surfactant TBAC or 3 -cyclodextrin( B -CD) was studied .The results showed that the catalytic properties of the two kinds of surfactants was different .The cationic surfactant TBAC was the most efficient for promoting the reaction rate of all five olefins, owing to the solubilization of olefm in micelle and the electrostatic interaction between the positive charge of micelle and the negative charge of rhodium active intermediates. The addition of nonionic surfactant P -CD ,which had only the solubilization for olefin Just increased slightly the rate of the reactant 1-3 . But in safrole hydroformylation the conversion and liner aldehyde content in products increased obviously. It was demonstrated that the reaction activity order of the five olefins in the presence of -CD was : (2)>(3) >(1) >(4) >(5); under the condition of adding TBAC the order was: (2)>(1) >(3) >(4) >(5). The results showed that the steric effect of the reactant in phenyl olefin hydroformylation was the key factor to influence the reaction rate, and the electronic effect was secondary.