Miscibility temperature

If the third substance dissolves in both liquids (and the solubility in each of the liquids is of the same order), the mutual solubility of the liquids will be increased and an upper C.S.T. will be lowered, as is the case when succinic acid or sodium oleate is added to the phenol - water system. A 0 083 molar solution of sodium oleate lowers the C.S.T. by 56 -7° this large effect has been applied industrially in the preparation of the disinfectant sold under the name of Lysol. Mixtures of tar acids (phenol cresols) do not mix completely with water at the ordinary temperature, but the addition of a small amount of soap ( = sodium oleate) lowers the miscibility temperature so that Lysol exists as a clear liquid at the ordinary temperature. 

In summary, what we have found is that the combination of a thermomorphic system and a surfactant is very effective for the hydroformylation of 1-octene and 1-dodecene. We believe that although a 90 10 ethanol/water and heptane system becomes miscible at 70°C, the additional water in a 50 50 ethanol/water and heptane system raises the miscibility temperature to >100°C. When a surfactant is added, the miscibility temperature is lowered and the biphasic solution becomes monophasic below the reaction temperature, resulting in good reaction rates. In addition, the presence of the surfactant also enhances the selectivity compared to the completely homogeneous system from 1.8 to 5.3 L/B... 

Some potential limitations associated with this protocol merit note. For example, with sequence A in Fig. 1, insoluble by-products will interfere with catalyst recovery. With sequence B, interference will depend upon the type of support. For instance, the Teflon tape in Fig. 8 should be easily separable from another solid material, as would a mesh or reactor liner. Also, since heating is required to achieve homogeneity, the method is best suited for reactions conducted at elevated temperatures. However, there are many reactions which proceed rapidly under fluorous/organic liquid/liquid biphase conditions (i.e., before the miscibility temperature is reached) [55-57,70]. Therefore, it is not unreasonable to expect that sohd fluorous catalysts with little or no solubility can also efficiently promote certain reactions, as represented by sequence A-1 in Fig. 1 [29]. 

It is clear that the Flory-temperature is the critical miscibility temperature in the limit of infinite molar weight. Fox (1962) succeeded in correlating 0F-temperatures of polymer-solvent systems with the solubility parameter 5S of the solvent. Plots of 8S as a function of 0F are shown in Fig. 7.8. 

The precipitation behavior of the polymer is intapreted by a photostimulated change of the critical miscibility temperature T. For polystyrene dissolved in cyclohexane, the polymer precipitates at temperature below T. According Fox and Flory [65], T depends on the molecular weight M as... 

Fig. 32. Molecutar weight (M) depmdence of critical miscible temperature, T. T Q and Te(T) indicate the values of T, for polystyrene with cis and trans azobenzene groups at M = oo, respectively. See text for M, t, t Tm, and T ...

Theory thus predicts that the reciprocal of the critical temperature (in °K ) for the onset of opalescence should vary linearly with the reciprocal of the square root of the molecular weight in a given polymer-solvent system. Furthermore, 9 may now be identified as the critical miscibility temperature in the limit of infinite molecular weight. 

Polar aliphatic plasticizers mis less well with polymers than do polar aromatics and, consequently, may exude (bloom) from the plasticized polymer more easily. Their polymer miscibility temperature is higher than that for the first group. These plasticizers are called oil-type plasticizers, and their kerosene extraction index is high. Their plasticization action is, however, more pronounced than that of polar aromatic plasticizers at the same molar concentration. Moreover, since the aliphatic portions of the molecules retain their flexibility over a large temperature range, these plasticizers give a better elasticity to finished products at low temperature, as compared to polar aromatic plasticizers, and allow the production of better cold-resistant materials. In PVC they also cause less coloration under heat exposure. 

MEK is an antisolvent for the wax and helps to reduce its solubility. If the MEK content is too high the Basestock may become insoluble and a phase separation will occur. MIBK or Toluene is added to help solubilize the oil. Both of these prosolvents have a higher affinity for wax molecules than MEK. The higher the concentration of prosolvent the more wax stays in solution, and ends up in the filtrate. This raises the pour point of the dewaxed oil and since the manufacturer must meet dewaxed oil pour point specification the manufacturer is forced to reduce the filtration temperature to remove more wax. The reduction in filtration temperature increases the viscosity of the slurry and filtration rates are slower and oil removal from the wax cake becomes more difficult. Thus the objective is to use the maximum amount of MEK without having a phase separation. A plot of the phase separation temperature or miscibility temperatures vs. solvent composition may be used to help set the optimum solvent composition. 

Two or more liquids which mix to form one homogeneous phase. Usually preferred in solvent dewaxing. Refers to oil and solvent mixture Miscibility temperature Temperature at which solvent and feed are completely miscible - all feed dissolved in solvent -and there is no phase separation in treater tower or in dewaxer slurry. 

The theta temperature may also be phenomenologically defined as the critical miscibility temperature at the limit of infinite molar mass (110). Since a solution may exhibit two... 

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