Yaozhong Li

Micellar effect in high olefin hydroformylation catalyzed by water-soluble rhodium complex

Abstract 1-Dodecene hydroformylation catalyzed by water-soluble rhodium complex, RhCl(CO)(TPPTS) 2 [TPPTS: P( m -C 6 H 4 SO 3 Na) 3 ], in the presence of surfactants and alcoholic solvents was studied. The results indicated that the hydroformylation in biphasic catalytic system occurred in the interface of aqueous/organic phases. 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 static electricity attraction between active rhodium anion species and cationic end of surfactant.

Studies on 1-dodecene hydroformylation in biphasic catalytic system containing mixed micelle

Abstract Hydroformylation of 1-dodecene catalyzed by water-soluble rhodium-phosphine complex, RhCl(CO)(TPPTS) 2 (TPPTS: P( m -C 6 H 4 SO 3 Na)), in the presence of various mixed micelles was investigated. When either an anionic surfactant sodium dodecyl sulfate (SDS) or dodecylbenzonesulphonate (DBS), a nonionic surfactant Triton X-100 or Brij 35, or alcohol was added into cationic surfactant cetyl pyrindium bromide (CPB) solution, a mixed micelle formed. The decrease in critical micelle concentration (CMC) and the increase in solubilization of 1-dodecene in the mixed micelle were observed. Hydroformylation of 1-dodecene exhibited higher conversion and higher regioselectivity in the mixed micellar solution than in the single micelle of CPB. The synergistic mechanism of two different surfactants was discussed.

Long chain olefin hydroformylation in biphasic catalytic system—how the reaction is accelerated

Abstract The effect of TPPTS [ p ( m -C 6 H 4 SO 3 Na) 3 ], RhCl(CO)(TPPTS) 2 and olefin on CMC (critical micelle concentration) of the aqueous solution containing cationic surfactant cetyltrimethylammonium bromide (CTAB) was studied by the maximum bubble pressure method. The apparent molar mass of micelle was determined by a light scattering method. The results showed that the addition of TPPTS and RhCl(CO)(TPPTS) 2 into aqueous solutions of CTAB caused the decrease of CMC and the increase of the apparent molar mass of micelle. The data supported the suggestions about enrichment of rhodium catalyst in micelle interface layer and about the solubilization of olefin in micelle. This explanation was confirmed by the measurements of rhodium concentration in the interface layer using ICP method. The acceleration mechanism of long chain olefin hydroformylation in a biphasic catalytic system containing a cationic surfactant was provided.

Synergistic effect of TPPTS and TPPDS on the regioselectivity of olefin hydroformylation in two-phase catalytic system

Abstract The hydroformylation of long-chain olefins catalyzed by the water soluble rhodium complex, RhCl(CO)(TPPTS)2, were studied in aqueous/organic biphasic system containing cationic surfactants. The addition of TPPDS as a modifier dramatically increased the regioselectivity of olefin hydroformylation. A synergistic effect of TPPTS and TPPDS on the regioselectivity was observed. The ratio of linear/branched aldehyde rose from 6.5 (without TPPDS) to 22.3 ([TPPTS]/[TPPDS]=2:1). The steric structure of hydrophilic group in the cationic surfactants exhibited an important influence on the regioselectivity. The hydrophilic group with a small steric volume was favorable for the formation of linear aldehyde. It was found that when the alkyl chain length of the higher olefin and that of the cationic surfactant were comparable (matching size), the regioselectivity for linear aldehyde was outstandingly high.

Studies on catalytic hydrogenation of citral by water-soluble palladium complex

Abstract The hydrogenation of citral has been studied in biphasic system using water-soluble PdCl 2 (TPPTS) 2 as catalyst. The selectivity to form citronellal increased with increasing pH values of the aqueous phase. At the same pH value, the selectivity was higher when the hydrogenation was carried out in the presence of Na 2 CO 3 than in the presence of NaOH. The main product was citronellal and a maximum yield of 93% had been obtained using Na 2 CO 3 solution at pH 11.6. The CC bond in citronellal could be further hydrogenated to form dihydrocitronellal when the hydrogenation was carried out in distilled water at pH 6.0. The yield of dihydrocitronellal could reach 93% with prolonged reaction time to 6 h. Therefore, high yields of either citronellal or dihydrocitronellal could be obtained from citral by selecting the corresponding reaction conditions.

Hydrogenation of crotonaldehyde and cinnamaldehyde catalyzed by water-soluble palladium complex

Abstract The selective hydrogenations of crotonaldehyde and cinnamaldehyde in the aqueous-benzene biphasic system were investigated using water-soluble palladium complex PdCl 2 (TPPTS) 2 as catalyst. The hydrogenation rate of crotonaldehyde was higher than that of cinnamaldehyde under similar reaction conditions. The palladium complex selectively catalyzed the hydrogenation of CC bond in crotonaldehyde to form butanal (100%). On the contrary, hydrogenation of both CC and CO bonds in cinnamaldehyde occurred simultaneously, with the amount of phenylpropanal only slightly higher than that of phenylpropanol. However, the reduction of CO bond of cinnamaldehyde could be inhibited by the addition of Na 2 CO 3 solution. Therefore, high selectivity to form phenylpropanal (91%) could be obtained by using Na 2 CO 3 solution at pH 12.2. Other factors affecting the hydrogenation conversion and selectivity of crotonaldehyde and cinnamaldehyde were also discussed.

Novel effect of additional metal ion on hydroformylation of hexene-1 in biphasic system

The hydroformylation of hexene-1 is carried out in the biphasic system with RhCl(CO)(TPPTS)2 (TPPTS = P(C6H4-m-SO3 Na)3), TPPTS and CTAB (cetyltrimethylammonium bromide). The rhodium catalyst concentration in interface has a drastic effect on reaction rate, and additional salts make reaction rate decrease obviously because they influence the distribution of catalyst in the biphasic system. Inorganic salts also have influence on the turnover frequency in the order: TOF (M 3+ )< TOF(M 2+ )< TOF(M + ) (M n+ is a metal cation with a charge of +n). However, additional inorganic salts do not change the regioselectivity obviously in this hydroformylation.