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Separation by extraction of benzoic acid and nitrotoluene

A typical mixture comprises phthalic anhydride, maleic anhydride and adiponitrile. The extractive agent is introduced near the top of the column and flows downward until it reaches the stillpot or reboiler. Its presence on each plate of the rectification column alters the relative volatility of the close boiling compounds in a direction to make the separation by extraction of benzoic acid and nitrotoluene on each plate greater and thus require either fewer plates to effect the same separation or make possible a greater degree of separation with the same number of plates.

The extractive agent should boil higher than any of the close boiling liquids being separated and not form minimum boiling azeotropes with them. Usually the extractive agent is introduced a few plates from the top of the column to insure that none of the extractive agent is carried over with the lowest boiling component. This usually requires that the extractive agent boil twenty Centigrade degrees or more higher than the lowest boiling component.

At the bottom of a continuous column, the less volatile components of the close boiling mixtures and the extractive agent are continuously removed from the column. The usual methods of separation of these two components are the use of another recification column, cooling and phase separation, or solvent extraction. The operation of an extractive distillation system has been well described by Butler, U.

He suggests a large number of pure compounds including alcohols, glycol ethers and sulfolanes to separate both benzene and toluene. No information is given here on the relative volatility and thus relative performance of these compounds as extractive distillation agents. Atlani et al, French Pat. Asselinieau in German Pat. Mueller in German Pat. Heuwels in German Pat. Improved equipment for this separation was presented by E.

John in German Pat. It should be noted that all the work reported to date deals with the use of a single compound as the extractive distillation agent. The advantage of using extractive distillation in this separation can be seen from Table I below. RelativeVolatility for Benzene-Cyclohexane Separation.

Separating Mixture Of Benzoic Acid And Nitrotoluene

To separate these two by conventional rectification requires a minimum of 750 theoretical plates. This however is at total reflux. At a specific reflux, it will be more. The theoretical plates have to be converted to actual plates.

Thus more than 1000 actual plates are required, clearly an impossible separation. Several extractive distillation agents that I have discovered push the relative volatility as high as 4. Converting from total reflux to an actual reflux will increase the plate requirement somewhat but still make for a very attractive separation.

Extractive distillation typically requires the addition of an equal amount to twice as much extractive agent as close boiling compounds on each plate of the rectification column. The extractive distillation agent should be heated to about the same temperature as the plate into which it is introduced.

Thus extractive distillation imposes an additional heat requirement on the column as well as somewhat larger plates for the same product output. To be economically attractive, the extractive distillation system must save more in the reduction of separation by extraction of benzoic acid and nitrotoluene number of theoretical plates and the size of the column than it adds in the cost of larger plates and the additional heat requirement.

This will vary depending on the difficulty of the separation and the cost of heat. I found that in the separation of benzene from cyclohexane, the extractive agent should increase the relative volatility to about 1. Another consideration in the selection of the extractive distillation agent is its recovery from the bottoms product. The usual method is by rectification in another column. In order to keep the cost of this operation to a minimum, an appreciable boiling point difference between the compound being separated and the extractive agent is desirable.

I recommend twenty Centigrade degrees or more difference. Benzene is the major precursor to many processes for making plastics and dyes. In these uses it is absolutely essential that the benzene be very pure. It is the presence of impurities that make it a poor polymerizing agent as a plastic or render it inconsistent as a dye intermediate.

More than half of the benzene of commerce originates in or is converted from petroleum. It is a particular object of this invention to identify suitable mixtures of organic compounds which will increase the apparent relative volatility of benzene to close boiling non-aromatic hydrocarbons to values higher than that attained by single compounds.

It is a further object of this invention to identify mixtures of organic compounds which, in addition to the above constraints, are stable, can be separated from the benzene by rectification with relatively few actual plates and can be recycled to the extractive distillation column and reused with little decomposition.

In order to demonstrate this invention, I evaluated extractive agents with benzene b. The relatively volatility of benzene to cyclohexane is 1. Table II shows the relative volatility of benzene to cyclohexane and benzene to 2,4-diemthylpentane with a number of solvents mixed with phthalic anhydride, maleic anhydride or both. Table III shows the relative volatility of benzene to cyclohexane and benzene to 2,4-dimethylpentane with a number of solvents mixed with benzoic acid, maleic anhydride or both.

I have found that this is the preferred ratio of extractive distillation agent to hydrocarbon in this separation. The amount of phthalic anhydride, maleic anhydride, benzoic acid and solvent in the ternarys shown in Tables II, III and IV was approximately equal to each other as were the binarys also.

The exact ratio does not appear to be critical. Likewise the relative volatilities shown in Tables II, III and IV do not change appreciably when the ratio of benzene to non-aromatic hydrocarbon is varied. Table II shows that a mixture of phthalic anhydride, maleic anhydride and adiponitrile changes the relative volatility to 4.

Separating Mixture Of Benzoic Acid And Nitrotoluene Biology Essay

Table II also shows that this mixture will change the relative volatility of benzene-2,4-dimethylpentane to 4. Thus extractive distillation by rectification in columns of ten to twelve actual plates will easily separate benzene from any other hyrdocarbon. Samples of the vapor and liquid were removed and analysed by gas chromatography. The vapor contained 40.

This indicates a relative volatility of cyclohexane to benzene of 1. This has been confirmed by other investigators. Example 2 A mixture comprising 35 grams of benzene and 65 grams of 2,4-dimethylpentane was charged to the vapor-liquid equilibrium still and refluxed for six hours.

Analysis indicated a vapor composition of 35. This indicates a relative volatility of 1.

  1. Sulphuric acid, with the evolution of heat or change of colour. The purified products obtained were not allowed to dry completely before their mass was taken.
  2. Heat and pour the mixture into dil NaOH solution taken in a beaker.
  3. Usually the extractive agent is introduced a few plates from the top of the column to insure that none of the extractive agent is carried over with the lowest boiling component. Capillary electrophoretic analysis of classical organic pollutants p-toluic acid, benzoic acid capillary electrophoretic analysis of classical organic.

Example 3 A mixture comprising 25 grams benzene, 25 grams cyclohexane and 50 grams of adiponitrile was charged to the vapor-liquid equilibrium still and refluxed for twelve hours. Analysis gave a vapor composition of 73. This indicates a relative volatility of 3. Ten grams of adiponitrile were added and refluxing continued for another eleven hours.

Analysis gave a vapor composition of 76.

  • Example 6 A mixture comprising 25 grams benzene, 25 grams cyclohexane, 17 grams phthalic anhydride, 17 grams maleic anhydride and 17 grams adiponitrile was charged to the vapor-liquid equilibrium still and refluxed for 14 hours;
  • Pour the mixture into ice water.

This indicates a relative volatility of 2. Example 4 A mixture comprising 25 grams benzene, 25 grams cyclohexane, 25 grams maleic anhydride and 25 grams adiponitrile was charged to the vapor-liquid equilibrium still and refluxed for twelve hours.

Analysis gave a vapor composition of 80. Five grams of maleic anhydride and 5 grams of adiponitrile were added and refluxing continued for another 13 hours. This indicates a relative volatility of 4. Example 5 A mixture comprising 25 grams benzene, 25 grams cyclohexane, 25 grams phthalic anhydride and 25 grams adiponitrile was charged to the vapor-liquid equilibrium still and refluxed for thirteen hours.

Two grams of phthalic anhydride and eight grams of adiponitrile were added and refluxing continued for another ten hours. Analysis gave a vapor composition of 87. Example 6 A mixture comprising 25 grams benzene, 25 grams cyclohexane, 17 grams phthalic anhydride, 17 grams maleic anhydride and 17 grams adiponitrile was charged to the vapor-liquid equilibrium still and refluxed for 14 hours. Three grams each of phthalic anhydride, maleic anhydride and adiponitrile were added and refluxing continued for another ten hours.

Analysis gave a vapor composition of 68. Example 7 A mixture comprising 25 grams benzene, 25 grams 2,4-dimethylpentane, 17 grams phthalic anhydride, 17 grams maleic anhydride and 17 grams adiponitrile was charged to the vapor-liquid equilibrium still and refluxed for eleven hours.

Analysis gave a vapor composition of 77. Three grams each of phthalic anhydride, maleic anhydride and adiponitrile were added and refluxing continued for another twelve hours. Analysis gave a vapor composition of 78. Each of the solvent combinations separation by extraction of benzoic acid and nitrotoluene there was determined in this manner.

Example 8 A column consisting of one ten-plate section of one-inch diameter glass perforated plates equipped with a vacuum jacket was employed.

Separation by extraction of benzoic acid and nitrotoluene

The column was fitted with a Corad constant reflux ratio distilling head. Between the Corad head and the top of the column, a feed line from a constant flow bellows pump was introduced. The column had been calibrated with a test mixture of ethylbenzene and p-xylene, which mixture possesses a relative volatility of 1. The column calibrated 4. The column was operated at total reflux for about an hour and then the pump started at a rate to deliver about one part of extractive agent to one part of cyclohexane-benzene being boiled up.

  • Benzene is the major precursor to many processes for making plastics and dyes;
  • The hot mixture is filtered;
  • The purpose of this test is to find out the presence or absence of nitrogen, sulphur and halogens in the given organic compound;
  • I recommend twenty Centigrade degrees or more difference;
  • In order to conclude one could discuss a modification which could be done to the above protocol for the separation of a mixture of benzoic acid and 4-nitrophenol;
  • Heat the solution and add about 15ml of saturated solution of potassium permanganate slowly till a light pink colour remains.

The extractive agent in this example was 33. The following data were obtained: Without the extractive agent it would have been 1. The total effect of the mixture far exceeds the sum of the parts. Claims 5 The nature of the present invention having been described and illustrated by examples, what I wish to claim as new and useful and secure by Letters Patent is: A method for separating benzene from close boiling non-aromatic hydrocarbons which comprises distilling a mixture of benzene and close boiling non-aromatic hydrocarbons in a rectification column in the presence of a sufficient amount of an extractive agent to provide a relative volatility of 2.

The method of claim 1 in which the extractive agent comprises phthalic anhydride, maleic anhydride and a at least one of said solvents. The method of claim 3 in which the extractive agent comprises benzoic acid, maleic anhydride and one of said solvents.