The Studies On Oil/Aqueous Biphasic Catalytic Hydroformylation Of Long-Chain Olefins Catalyzed By Rhodium-Phosphine Complexes

Hydroformylation of 1-dodecene catalyzed by water-soluble rhodium-phosphine complex, RhCl(CO)(TPPTS)2 [TPPTS:P(m-C6H4SO3Na)], in the presence of mixed micelles was investigated. When anionic surfactant SDS or DBS [dodecylbenzonesulphonate], nonionic surfactant Triton x-100 or Brij-35, or alcohol was added into cationic surfactant CPB [cetyl pyrindium bromide] or CTAB (cetyl trimethyl ammonium bromide) solution, a mixed micelle formed. The decrease of critical micelle concentration (CMC) and the increase of 1-dodecene solubilization in the mixed micelle were observed. Hydroformylation of 1-dodecene exhibited higher conversion and higher regioselectivity in the mixed micellar solution than that in the solution of CTAB or CPB. The synergistic mechanism of two different surfactants was discussed.Nineteen gemini surfactants with flexible or rigid spacer have been synthesized, among them ten surfactants with rigid spacer of aromatic group were new compounds. The determining values of CMC and solubilization of laurylbenzene or 1-dodecene in gemini surfactant solutions showed that CMC of gemini surfactants were lower than CTAB but their solubilization abilities were higher than that of CTAB. The influences of the concentration of gemini surfactants and the stirring rates on 1-dodecene hydroformylation wereinvestigated. The results showed that in the biphasic catalytic system of RhCl(CO)(TPPTS)2-TPPTS, the hydroformylation of long chain olefins in the prescribe of gemini surfactants occurred with higher turn over frequency (TOF) and higher regioselectivity for linear aldehyde (L/B) than that using CTAB as surfactant. These phenomena could be attribute to that the lower CMC and greater surface tension reduction ability of gemini surfactant, which would be favorable for the decrease of phase transfer energy barrier, and thereby the reaction rates was greatly accelerated. The more compact structure of the spherocylindrical micelle forming from gemini surfactant with flexible spacer group could construct a favorable microenvironments for the formation of linear aldehyde, thus the higher regioselectivities were observed. However, the regioselectivities for linear aldehyde in the solution of gemini surfactants solutions with rigid group spacer were the same as in CTAB solution. A benzene ring could be approximated as being equivalent to 3-3.5 methylene units in length, the larger head group would lead to low selectivity for linear aldehyde.The double-chain surfactants containing one cationic head group and two long hydrophobic chains with the formula CnH2n+iN(CH3)2CmH2m+tBr have been synthesized and used in hydroformylation of long chain olefins in aqueous/organic biphasic system. It was found that the the double-chain surfactant could greatly accelerated the reaction even without stirring the solution. The TOF achieved 2290h-1 in the hydroformylation of 1-dodecene without stirring, while under the same reaction condition the conversion was no more than 4% if CTAB was used instead of double-chain surfactant solution. The hydroformylation of other olefins with various chain length have been studied without stirring. High conversions were also obtained even for 1-hexadecene and 1-octadecene. The investigation of effect of the surfactant structure on the reaction rate of various olefins indicated that there was a subtle matching relationship between the length of hydrophobic chain and olefin. In the other aqueous/organic biphasic catalytic reactions such as hydrogenation of 1-dodecene, hydroaminomethylation of 1-dodecene and regioselective hydrogenation of avermectin to ivermectin were studied withoutstirring and the obvious accelerations in the double-chain surfactant solutions were also observed.