Entrainer isopropanol

For heterogeneous batch distillation a new double column configuration operating in closed system is suggested. This configuration is investigated by feasibility studies based on the assumption of maximal separation and is compared with the traditional batch rectifier. The calculations are performed for a binary (n-butanol - water) and for a ternary heteroazeotropic mixture (isopropanol - water + benzene as entrainer). Keywords heteroazeotrope, batch distillation, feasibility studies. 

The separation of a homoazeotropic isopropanol ( 4) - water (5) mixture is considered. Addition of an entrainer, in a small amount, is needed. The steps of a production cycle... 

Separation of the ternary mixture (isopropanol (A) - water (B) + benzene (E)) Binary azeotropic charge ( xbaz = [0.674,0.326,0]) is separated by the application of an entrainer ( ). The composition of the ternary IPA - water - benzene heteroazeotrope and those of its it-rich and 5-rich phases ... 

In the conventional reactive distillation combined with azeotropic distillation an azeotropic distillation takes place in the second column. An entrainer is fed in order to obtain pure isopropanol at the bottom and a water/entrainer mixture at the top. The entrainer is chosen such that it forms an... 

The entrainer-based reactive distillation column consists of a reactive section with a distillation section placed on top, in where the entrainer is responsible for removing the water out of the reactive section. The top vapour, which consists of entrainer, water and isopropanol, is condensed and two phases are obtained through decantation an aqueous... 

In the case of a still less reactive halide, or one with a tendency to undergo dehydrohalogenation, it is advantageous to add a reactive halide such as 1-bromo-naphthalene or n-butyl bromide for entrainment. Thus the reaction of 0.05 mole of eyclohexyl chloride and 0.05 mole of 1-bromonaphthalene with 0.33 g. atom of magnesium and isopropanol (0.3 mole) in 50 + 20 ml. of decalin afforded a mixture of 83% of cyclohexane and 10% of cyclohexene (removable with sulfuric acid). By this procedure cyclohexyl fluoride gives cyclohexane (33%) and benzotrifluoride gives toluene (10%). Fluorobenzene is inert. 

These developments will have a wide impact. Reaction enhancement will be a major beneficiary, but a look at the simpler field of solvent dehydration shows that the innovation process is very application dependant. Pervaporation (with vapor permeation) is progressively displacing other techniques in solvent dehydration. Replacing entrainer distillation for drying ethanol and isopropanol, pervaporation at initial stages is always now preferred to techniques, where a third component must be added to shift equlibria. The handling of entrainers and/or calcium chloride or caustic with the attendant environmental risks and costs is no longer a viable option. 

The reactor output is first cooled and then scrubbed with water to rid the hydrogen of entrained reactants and products, followed by light and heavy ends separation in a series of three distillation columns, the second producing. acetone specifications at the top, with the third column designeB to recover unconverted isopropanol to be recycled. If the feed consists of the azeotrope containing 87 per cent weight alcohol, three additional columns are required for the purification of the acetone and the recycling of isopropanol in a sufficient concentration. 

Isopropanol, ethanol Standard applications for pervaporation, typically dehydrated from their azeotropes to fractions of a percent of water. De-bottlenecking of entrainer plants. 

In a few cases, this does not present a problem. DMF forms low-boiling azeotropes with heptane and xylenes. The addition of water in the fractionation system as an entrainer allows the formation of azeotropes with these hydrocarbons, but not with DMF. The hydrocarbon/water azeotrope at the column top splits into two liquid phases, so that the hydrocarbon can be removed and the water recycled. Similarly, in drying ethanol and isopropanol the unwanted water forms a separate phase which can be removed while the entrainer is recycled to pick up more water. 

Entrainers such as benzene, chloroform and carbon tetrachloride were used in the 1930s. Such materials, despite the fact that their other properties may be attractive, would be considered too toxic to be introduced into use today. A TLV of less than 10 ppm would be disqualified unless the solvent to be dried required handling precautions of the same level. Ethanol with a TLV of 1000 ppm or isopropanol (IPA) of 400 would not justify a highly toxic entrainer. 

The alcohols isopropanol, ferf-butanol and n-propanol all display this phenomenon with some potential azeotropic entrainers (Fig. 16.4). The barrier of about 17% n-propanol in water represents only a... 

While it is therefore more like ethanol and isopropanol, which require the addition of an entrainer to dry them by distillation, sec-butanol is not very hydrophilic and LLE can be linked to distillation in water removal processes. 

Table 16.13 shows the effectiveness of entrainers similar to those used for drying ethanol and isopropanol. In all three cases the MEK content of the water phase separating at the column top is low enough to consider sending it to effluent treatment rather than recycling it to try to improve the yield of the process. 

Figure 6.16b shows j oint usage of a distillation column and a decanter, when one of two liquid phases is brought in to the reflux of the column from the decanter or some amount of the second phase is added to the first phase. The example is separation of the mixture isopropanol(2)-water(3) using benzene(l) as an entrainer (Bril et al., 1977). Figure 6.16c shows another variant of distillation column for this separation, with one bottom section. 

Figure 6.16. Trajectories of heteroazeotropic distiUation (a) distillate from azeocolumn to decanter for separation toluene(l)-ethanol(2)-water(3) mixture (b) distillate from azeocolumn to decanter and a recycle stream of the entrainer from decanter to azeocolumn for separation benzene(l)-isopropanol(2)-water(3) mixture (c) distillate from azeostripping to decanter and a recycle stream of the entrainer from decanter to azeostripping for separation benzene(l)-isopropanol(2)-water(3) mixture (d) distillate from azeocolumn to decanter and a recycle stream of the entrainer from decanter to azeocolumn for separation acetic add(l)-n-butyl acetate (2)-water(3) mixture (e) bottom from azeocolumn to decanter for separation butanol(l)-acetone(2)-water(3) mixture and (f) side product from azeocolumn to decanter for separation butanol(l)-acetone(2)-water(3) mixture. Regions of two liquid phases Regi,i 1,2 are shaded.

There are many important industrial applications of azeotropic separations, which employ a variety of methods. In this book we discuss several of these chemical systems and demonstrate the application of alternative methods of separation. The methods presented include pressure-swing distillation, azeotropic distillation with a light entrainer, extractive distillation with a heavy entrainer (solvent), and pervaporation. The chemical systems used in the numerical case studies included ethanol-water tetrahydrofuran (THF)-water, isopropanol-water, acetone-methanol, isopentane-methanol, n-butanol-water, acetone-chloroform, and acetic acid-water. Economic and dynamic comparisons between alternative methods are presented for some of the chemical systems, for example azeotropic distillation versus extractive distillation for the isopropanol-water system. 

In Part 3 of this book an extrainer is added to the system so that liquid-liquid sphtting can appear in the top decanter and also maybe in the top few stages of the azeotropic column. The LLE behavior in the decanter, or the VLLE behavior in the top stages of flie azeotropic column, can be predicted by Aspen Plus. The system of separating an isopropanol-water mixture using cyclohexane as the entrainer will be used as an example to demonstrate the way to generate a LLE envelope in Aspen Plus. 

---