Hydroformylation Of High Olefin--Influence Of Electronic And Steric Effects Of Phosphine Ligand

The influence of electronic and steric effects of phosphine ligand on hydroformylation have been extensively studied since 1970. The electron-donating substituent at the ortho- or para-positions of the aromatic rings affect greatly the behaviour of phosphine ligand. Three oil-soluble phosphines : tri(p-methoxylphenyl)phosphine (4-MOTPP), tri(o-methoxylphenyl) -phosphine ( 2-MOTPP), P(p-PhOC8H17)3 and two water-soluble phosphines were synthesized and characterized, and their effect on hydroformylation was investigated in homogeneous and biphasic system.In homogeneous catalytic system, the catalytic properties of three oil-soluble phosphines as ligand on hydorformylation of 1-dodecene were studied with Rh(acac)(CO)2 as catalytic precursor. The effect of the molar ratio of phosphine to Rh and reaction temperature as well as reaction pressure on hydroformylation were investigated in detail. The results indicated that the donated methoxyl of aromatic ring induced the lower catalytic activities compared with triphenylphosphine. The better activities were observed at lower P/Rh molar ratio in the case because of the more strong coordinated ability of the alkoxyl substituted phosphines with rhodium.In aqueous-organic two phase catalytic system, the catalytic properties of two catalyst system RhCl(CO)(TPPTS)2+4-MOTPPTS, RhCl(CO)(TPPTS)2 + 2-MOTPPTS for 1-dodecene hydroformylation were investigated in the presence of cetyltrimethylammonium bromide(CTAB). The results indicated that the donatedmethoxyl of aromatic ring induced the decrease of the activity and the selectivity to the formation of aldehyde and the more steric 2-MOTPPTS showed lower activity and less selectivity than 4-MOTPPTS. The addition of cationic surfactant CTAB could accelerate the reaction rate, and no catalytic activity was odserved in the absence of surfactant. The gemini and double long-chain alkyl surfactants could facititate the hydroformylation in two phase catalytic system more efficiently than CTAB.