TM systems

This is part of the Gaussian 94(TM) system of programs. It is based on the Gaussian 92(TM) system (copyright 1992 Gaussian, Inc.), the Gaussian 90(TM) system (copyright 1990... 

Multiphase Catalysis in Temperature-Dependent Multi-Component Solvent (TMS) Systems... 

Fig. 1 Principle of temperature-dependent multi-component solvent systems (TMS systems)...

With the product mixture it was found that a much smaller amount of the mediator s3 is required to obtain a homogeneous solution than in the pure solvent mixture or the reaction mixture at the beginning of the reaction at the same temperature. For example the ratio in the TMS system si toluene DMF decreases at 60 °C from 1 5 2.9 to 1 5 2.1 and in the solvent system si toluene acetonitrile from 1 5 4.6 to 1 5 3.1. With DMSO as s3 the composition decreases from 1 3 2.4 to 1 3 3.9. 

The catalyst system Pd(acac)2/TPPTS (TPPTS = trisulfonated triphenylphos-phine) was used in the experiments in which the telomerization of butadiene with ethylene glycol in TMS systems was investigated. However, the catalyst precipitates from many solvent mixtures as a yellow oil or solid, as soon as a homogenous phase is obtained. For this reason the solubihty of the catalyst was determined in various solvent systems. A solution of the catalyst in the mixture of ethylene glycol and water (si) and toluene (s2) was used in a weight ratio of 1 3. The various mediators s3 were added until a clear solution was formed or the catalyst precipitated. Only with DMF or DMSO can a clear solution be obtained. The addition of the catalyst to the polar phase causes an increase in the amount of s3 required to achieve a homogeneous system in the solvent system si toluene DMF the ratio increases from 1 5 4 to 1 5 4.4. 

One possibility to raise the solubility of the polar catalyst in the solvent mixtures is to use a higher water content. In the TMS system si toluene DMF a larger amount of the semi-polar solvent is required to obtain a homogeneous solution, if more water is added. If the amount of water is doubled the amount of s3 increases from 1 5 4.4 to 1.35 5 6.1 and a ratio of 2 5 8.9 is needed, if the water content is four times higher. The same tendency is observed if different non-polar solvents s2 or different mediators s3 are used the higher the water content the more of the mediator s3 is required. The temperature dependency is almost not affected when more water is added to the solvent systems. 

Telomerization of Butadiene with Ethylene Glycol in TMS Systems... 

Catalysis experiments were performed to investigate the telomerization of butadiene with ethylene glycol in selected TMS systems (e.g. si toluene DMF 1 5 4 or sl 2-octanol DMSO 1.35 3 5.2). With Pd/TPPTS as the catalyst a maximum yield of only 10% of the desired products could be achieved. With Pd/TPPMS the yield increased up to 43% in the TMS system si toluene isopropyl alcohol, but additional water had to be added to obtain a phase split after the reaction. The catalyst leaching is very high and 29% of the palladium used is lost to the product phase. 

A yield of up to 30% is achieved by use of PETPPO in the TMS system si toluene acetonitrile and with MDPP as the ligand the yield reaches a level of 20%. Again, however, too much of the palladium catalyst is lost to the product phase in both cases with about 40% to 50% (Table 1). 

Table 1 Telomerization of butadiene with ethylene glycol in TMS systems. Reaction conditions 0.06 mol % Pd(acac)2 based on ethylene glycol, Pd/P =1 3 butadiene/ethylene glycol = 2.5 1, si = ethylene glycol water 2 1, 80 °C 4 h 1200 rpm...

The palladium leaching to the product phase was investigated via ICP-OES measurements. In all cases about 5% of the metal catalyst is lost. This palladium loss is in the same range as in the biphasic reaction in water with subsequent extraction with cyclohexane. Therefore, one can conclude that the use of cyclodextrins has almost no influence on the palladiiun leaching. For the reaction described in this work, this makes the use of cyclodextrins as PCT catalysts more attractive than the TMS systems to overcome mass transfer limitations. 

To elucidate the use of TMS systems for the isomerizing hydroformylation, PC was chosen as the solvent for the rhodium catalyst, because the best selectivity to n-nonanal of 95% with a conversion on trans-4-octene of also 95% was achieved in this solvent under single-phase conditions. Dodecane was used as a non-polar solvent for the extraction of the product and p-xylene served as the mediator between the catalyst and the product phase [24]. Appropriate operation points for the reaction within this solvent system were determined by cloud titrations. 

The TMS system PC/dodecane/p-xylene shows the phase behaviour depicted in Fig. 6 representing a system with a closed miscibility gap, which shows a strong temperature dependence. Possible solvent compositions are defined by the area between the two binodal curves at the temperatures of 25 °C and 80 °C. 

The conversion of trans-4-octene is very high in this TMS-system and reaches a level of 99%. The selectivity to the desired linear aldehyde amounts... 

However, the TMS-system PC/dodecane/p-xylene has still some severe limitations. Via ICP-investigations a strong rhodium leaching of 47% of the rhodium catalyst was detected. Furthermore, we observed a correlation between the amount of the mediator p-xylene and the amoimt of leaching. The more p-xylene used, the more rhodium is transferred into the non-polar do-decane phase. Therefore, catalyst recycling in these systems is impossible at the moment. 

N-octylpyrroHdone (NOP) imites polar and non-polar properties and was used as a mediator between the cycHc carbonates and n-dodecane as the extraction agent. Figure 8 shows the mixing behaviour of some TMS systems for the different cyclic carbonates. Obviously the miscibility gap increases with decreasing length of the carbonate s carbon chain. 

In general, more NMP than NOP is needed to close the miscibility gap between the cyclic carbonate and the extraction agent. In addition, a higher temperature dependency of the mixing behaviour can be recognized upon use of NMP at room temperature the NMP-TMS systems pass from closed to open systems. This effect results in an almost complete immiscibihty of the mediator and the cycHc carbonate with the extraction agent at separation temperature. In this way the catalyst leaching into the product phase can be suppressed. 

The hydroformylation was investigated at various compositions of the TMS system propylene carbonate/n-dodecane/N-octyl-2-pyrrohdone (16/63/21, 24/50/26, 36/36/28, 50/23/27, 63/13/24 wt. %). With increasing mass fraction of propylene carbonate the conversion of frans-4-octene can be increased from 92 to 98% while the selectivity to -nonanal decreases from 81 to 72%. In the same way the rhodium loss is reduced from 21 to 1% and the loss of phosphorous from 15 to 7% as compared to similar conditions with NOP. 

TMS systems, which were used in the isomerizing hydroformylation of frans-4-octene, should be apphcable to hydroaminomethylation as well because the hydroformylation is the first step of the reaction. For this reason similar TMS systems were apphed in a first series of investigations [40]. Propylene carbonate (PC) was chosen as the polar solvent si for the catalyst and alkanes (an isomeric mixture of dodecane or n-hexane) were used as non-polar component s2. 1.4-Dioxane, different pyrrohdones [N-methylpyr-rolidone (NMP), JV-ethylpyrrohdone (NEP), M-cyclohexylpyrrolidone (NCP) AT-benzylpyrrolidone (NBP) and N-octylpyrrohdone (NOP)] or esters of lactic acid (ethyllactate and butyllactate) served as mediator s3. As a test reaction the hydroaminomethylation of 1-octene with morphohne was investigated (Scheme 7). 

To determine appropriate TMS systems cloud titrations were performed at different temperatures from 25 °C to 100 °C. To a mixture of PC and s2 the mediator s3 was added dropwise imtil a homogeneous solution was formed. The phase behaviour of the TMS system PC/dodecane/NEP is shown in Fig. 12. 

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