Hydroformylation Of Olefin In Biphasic Catalytic System- Effect Of OTPPTS And Gemini Surfactant On The Reaction

Hydroformylation is a typical atomic economic reaction. In order to study the influence of TPPTS oxide (OTPPTS), which formed by the oxidation of TPPTS in the reaction course, OTPPTS was synthesized and characterized by 31P NMR. The hydroformylation of 1-hexene, 1-octene and 1-dodecene catalyzed by water-soluble rhodium complex [RhCl(CO)(TPPTS)2]〔TPPTS : P(m-C6H4SO3Na)3〕in the presence of OTPPTS〔O=P(m-C6H4SO3Na)3〕and cationic surfactant CTAB (cetyltrimethyl ammonium bromide) was studied. The results indicated that when TPPTS was oxidized and formed OTPPTS, the catalytic activity and selectivity for aldehyde would decrease owing to the content of TPPTS in aqueous solution decreased because the molar ratio of TPPTS/Rh was too low. If the molar ratio of TPPTS/Rh was kept a constant and the ratio was higher than 18, the molar ratio of OTPPTS/TPPTS was lower than 1:1, the performance of rhodium catalyst would not obviously change with the increase of OTPPTS/Rh ratio up to 18. It is proved that: 1. OTPPTS is not a poison for rhodium catalyst, 2. The increase of OTPPTS content in the aqueous solution would make the decrease of catalytic activity and selectivity for aldehyde if the molar ratio of TPPTS/Rh is too low. The change of TPPTS/Rh molar ratio would influence on the balance of catalytic active species in catalytic cycle and decrease the stability of rhdoium complex. If the molar ratio of TPPTS/Rh were kept a higher ratio, OTPPTS would improve the selectivity for aldehyde and inhibite the hydrogenation and isomerization of alkene.Biphasic catalytic system with water-soluble rhodium complexes has been successfully applied in lower olefin hydroformylation, however, the reaction rate of higher olefin is too slow due to it,s low solubility in water. One way to increase the solubility of the substrates in water is to add surfactant to the system, the strategy has been used in the hydroformylation of olefins with rhodium-TPPTS system. New cationic gemini surfactants with rigid and flexible spacer group were synthesized. The values of critical micelle concentration (CMC) and the solubilizations of 1-dodecene in micellar solution were determined by surface tension method and ultraviolet-visible spectrometry, respectively. The capacity of surface tension reduction of new gemini surfactants are better than CTAB, but the solubilizations of 1-dodecene in gemini surfactants solution are higher than that in CTAB solution. The promotion effect of cationic gemini surfactants on 1-dodecene hydroformylation in biphasic catalytic system was studied. The results indicated that in the biphasic system containing the catalyst RhCl(CO)(TPPTS)2 and TPPTS, the hydroformylation of 1-dodecene in the presence of gemini surfactants occurred with higher reaction rate than using conventional monomeric surfactant CTAB. The greater acceleration of gemini surfactants for 1-dodecene hydroformylation could be attributed to that cationic gemini surfactants had lower surface tension and better solubilization for the substrate. The lower surface tension was favorable for increasing the interfacial area of two phases, breaking phase barrier and promoting the substrate transfer to interface where the substrate coordinated with the active rhodium complex anion species. The regioselectivity for linear aldehyde in the solution of gemini surfactants with rigid spacer group was similar to that in CTAB solution, but the regioselectivity for linear aldehyde in the solution of gemini surfactants with flexible spacer group was higher than that in CTAB solution.