CHM 585 / 490

1. CHM 585 / 490 Chapter 4

2. Chapter 4 • Benzene / Toluene / Xylene • Terephthalic Acid • Cumene • Phenol / Acetone / Bisphenol A

3. BTX • Benzene / Toluene / Xylene • Predominantly ( about 90%) from oil • From reformate gasoline and pyrolysis gasoline • BTX Content • Reformate: 3/13/18 • Pyrolysis gasoline: 40/20/5

4. Reformate Gasoline • Distillation of crude oil gives low octane fractions which must be “reformed” before using as gasoline. • The fractions are mainly branched and unbranched alkanes and cycloalkanes • Reforming involves heating at 500ºC with acidic isomerization catalysts (e.g. Al2O3. SiO2) and Pt followed by distillation

5. Pyrolysis gasoline • From the cracking of naptha for the production of ethylene, propylene, and other olefins.

6. Isolation of Aromatics from Reformate and Pyrolysis Gas • Problems with fractional distillation • Cyclohexane, n-heptane, and other alkanes form azeotropes with benzene and toluene • Minor difference between boiling points of the C8 components. e.g.: • Ethylbenzene 136.2 ºC p-xylene 138.3 ºC • m-xylene 139.1 ºC o-xylene 144.4 ºC • Separation requires special processes

7. Separation Techniques • Azeotropic distillation • Extractive distillation • Liquid-liquid extraction • Crystallization • Adsorption Let’s review azeotropes before continuing

8. Fractional Distillation • Begin at a1 and heat to T2. • a2 is the liquid composition. • a2’ is the vapor composition. • Vapor is richer in A than the liquid. • Cool the vapor until condenses at T3. • a3 is the liquid composition. • a3’ is the vapor composition. • Vapor is even richer in A • Repeat until pure A is obtained.

9. Fractionating Column and Efficiency • The number of theoretical plates is the number of effective vaporization and condensation steps required to achieve a condensation of given composition from a given distillate.

10. Azeotropes • In some real systems, the temperature / composition curve is far from ideal. A maximum or minimum in the curve is possible; this is an azeotrope. • At the azeotrope, the liquid and vapor have the same composition

11. Low boiling azeotrope High boiling azeotrope • Makes physical separation of the two components impossible.

12. Distillation of Ethanol • Azeotrope is around 95 % ethanol. .

13. Impossible to distill ethanol to greater than 95%.

14. Azeotropic Distillation to Isolate Aromatics • Best when high aromatic content • The addition of strongly polar agents (amines, alcohols, ketones, water) facilitates the removal of alkanes and cycloalkanes as lower boiling azeotropes • For example, add acetone to remove nonaromatics from the benzene fraction and then extract the acetone from the benzene with water.

15. Extractive Distillation • An additive is used to increase the differences in boiling points • For example, add NMP (N-methylpyrrolidone) • This increases the boiling point of the aromatics by “complexation” of the  electrons in the aromatic ring with the NMP and therefore facilitates separation

16. Liquid-liquid extraction • Same principle as the separatory funnel, but continuous. Based upon countercurrent flow. • The mixture is added to the middle of a column. The extraction liquid is added to the top. The non aromatics leave the column at the top and the aromatics with solvent exits from the lower part of the column • Most extraction processes provide a mixing zone followed by a settling zone.  

18. Crystallization • Mainly to separate xylene isomers • p –xylene can be separated from a mixture by cooling to -20 ºC to -75ºC.

19. Adsorption • Depends upon selective adsorption on a column, followed by desorption • Molecular sieves = zeolites = alumino-silicates having different pore size • UOP process involves selective adsorption of p-xylene ( from a C8 stream) followed by desorption

20. p-Xylene • 7 billion pounds • BP-Amoco the biggest with 4.6 billion pounds of U.S. capacity • Virtually all goes to production of terephthalic acid and dimethyl terephthalate

21. Air oxidation. Common catalysts are: CoBr2, MoBr2 or HBr

22. By esterification with methanol.

23. TA & DMT • Dupont Cape Fear plant makes terephthalic acid ( sold to Alpek, a Mexican petrochemicals group) • Kosa ( Wilmington plant) makes terephthalic acid and dimethyl terephthalate • Kosa makes about 1.5 billion pounds per year of dimethylterephthalate – largest in North America

24. Cumene 8 billion pounds used in U.S. Essentially all used for phenol production

25. Cumene Capacity (million pounds) 8.7 Billion total • Chevron Port Arthur, Tex. 1,000 • Citgo Petroleum, Corpus Christi, Tex. 1,100 • Coastal Eagle Point, Westville, N.J. 140 • Georgia Gulf, Pasadena, Tex. 1,500 • JLM Chemicals, Blue Island, Ill. 145 • Koch Petroleum, Corpus Christi, Tex. 1,500 • Marathon Ashland, Catlettsburg, Ky. 800 • Shell Chemical, Deer Park, Tex. 1,100 • Sun, Philadelphia, Pa. 1,200

26. Phenol from Cumene

28. Sunoco Phenol PlantHaverhill, Ohio

29. Kellogg Phenol Plants

30. Phenol Uses • 41 %: Bisphenol-A • 28 % phenolic resins • 13 % caprolactam

31. Major Phenol Producers • Sun, Shell, Dow, GE, and Georgia Gulf are major producers • GE plant at 700 million pounds • JLM has a 95 million pound plant in Illinois (same JLM that operates shipping in Wilmington) • Current demand about 5 billion pounds • 0.62 pounds acetone per pound phenol

32. Bisphenol-A Cumene gives 1 mole of phenol per mole of acetone BPA uses 2 moles of phenol per mole of acetone Typically, phenol is in demand and acetone is a glut on the market

33. On to bigger things!