project on nitrobenzene

PROJECT ON NITROBENZENE

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ACKNOWLEDGEMENT

We here by place our sincere thanks to Dr.R.KARHIKEYAN, Head of the Department of Chemical Engineering , S.R.M Engineering College affiliated to S.R.M University and the faculty members of Chemical Engineering Department for their full hearted co-operation and encouragement for the successful completion of this project. We extend out thanks to Project guide D.BALAJI for the Motivation, encouragement and guidance provided by him. We would also like to extend our thanks to each and everyone who have helped us in completing this project successfully.

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ABSTRACT

The project deals extensively with the manufacture of nitrobenzene from mixed acid and benzene .Since the demand for aniline has been increasing day by day manufacture of benzene is more important. Nitrobenzene is obtained by treating mixed acid and benzene. A detailed process flow sheet, material balance, energy balance, have been done. A detailed design of equipments, cost estimation of plant, plant layout and safety aspects have been discussed.

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CONTENTS

Chapter No

Topic

Page NO.

1.

INTRODUCTION

5

2.

PHYSICAL PROPERTIES

7

3.

CHEMICAL PROPERTIES

9

4.

USES

12

5.

PROCESS DESCRIPTION

14

6.

MATERIAL BALANCE

19

7.

ENERGY BALANCE

25

8.

REACTOR DESIGN

29

9.

DISTILLATION COLUMN DESIGN

35

10.

COST ESTIMATION

44

11.

HEALTH AND SAFTEY FACTORS

51

12.

PLANT LAYOUT

55

13

CONCLUSION

62

14.

BIBLIOGRAPHY

64

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1.INTRODUCTION

5

1.CHAPTER

Nitrobenzene was first synthesized in 1834 by treating Benzene with Fuming Nitric Acid, and it was produced commercially in England in 1856. The relative case of aromatic nitration has contributed significantly to the large and varied industrial application of nitrobenzene and its derivative.

Nitrobenzene (oil of Mir bane) is a pale yellow liquid with an odor of bitter almonds. Depending upon the compound impurity , its color varies from pale yellow to yellowish brown. Nitrobenzene is one of the important raw materials for the dye manufacture and most nitrobenzene produced is used directly or indirectly in dye manufacture. It is manufactured on large scale only by aniline manufactures. Ref[1]

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2.PHYSICAL PROPERTIES

7

2.CHAPTER 2.Physical Properties of Nitrobenzene :ref[4] Molecular Weight

123.11

Boiling Point

210 - 211 °C

Melting Point

6 °C

Flash Point

88 °C (closed cup)

Vapor Density

4.3 (air = 1)

Vapor Pressure

1 mm Hg at 44.4 °C

Density/Specific Gravity

1.205 at 15/4 °C (water = 1)

Log Octanol/Water Partition Coefficient

1.85

Henry's Law Constant

2.44 x 105 atm-m3/mole

Conversion Factor

1 ppm = 5.04 mg/m3

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3.CHEMICAL PROPERTIES

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3.CHAPTER CHEMICAL PROPERTIES 1.

Nitrobenzene reactions involve substitution on the aromatic ring and reactions involving the nitro group.

2.

Under electrophilic conditions, the substitution occurs at a slower rate than for benzene and the nitro group promotes met substitution

3.

Nitrobenzene can undergo halogination,sulfonation and nitration, but it does not undergo Friedel-crafts reactions.

4.

Under nucleophilic conditions, the nitro group promotes ortho and para substitution.

5.

The reaction of nitro group to yield aniline is the most commercially important reaction of nitrobenzene.

6.

Depending on the conditions, the reduction of nitrobenzene can lead to a variety of products.

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Reduction Products Of Nitrobenzene Reagent

Product

Fe,Zn or Sn+HCl

Aniline

H2+metal catalyst+ heat (gas phase or solution)

Aniline

SnCl2+acetic acid

Aniline

Zn+NaOH

Hydrazobenzene, azobenzene

Zn + H2O

N-Phenylhydroxylamine Azoxybenzene

Na3ASO3

Azoxybenzene

LiAIH4

Azobenzene

Na2S2O3 + Na3PO4

Sodium Phenylsulfamate,C6H5NHSO3NA

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4.USES

12

4.CHAPTER

The largest end use of nitrobenzene is in the production of aniline.approximtely 95-98% of nitrobenzene is converted to aniline the demand for nitrobenzene fluctuates with the demand for aniline production grew at an average annual rate of almost 5% from 1984 to1988 but dropped by over 4% during the 1989-1990 economic downturn. For 1990,96% of the 532972 metric tons of nitrobenzene left were used to produce variety of other products, such as para-aminiphenol and nigrosine dyes. The U.S. producers of PAP are MALLINCHRODT,INC., RHONEPOULENC, and Hoechst cleanse with combined production capacities >35000 metric tons. Mallinckrodt is the largest producer, with over 50% of capacity PAP primarily is used as an intermediate for acetaminophen. Ref[4]

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5.PROCESS DESCRIPTION

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5.CHAPTER Nitrobenzene is prepared by direct nitration of benzene, using a nitric acid-sulphuric acid mixture. The reaction vessel or nitrator is a specially built cast-iron or steel kettle fitted with an efficient agitator. The kettle is jacketed and generally contains internal cooling coils for proper control of the exothermic reaction. Nitrobenzene can be produced by either a batch or a continuous process with a typical batch, the reactor is charged with benzene, and the nitrating acid (5660% H2SO4,27-32wt% HNO3 and 8-17%wt% H2O) is added slowly below the surface of the benzene. The temperature of the mixture is maintained at 55-55°C by adjusting the feed rate of the mixed acid and the amount of cooling. the temperature can be raised to 90°C towards the end of the reaction to promote completion of reaction. The reaction mixture is fed into separator where the spent acid settles to the bottom and is drawn off to be refortified. The crude nitrobenzene is drawn from the top to the separator and washed in several steps. depending on the desired purity of the nitrobenzene the product can be distilled. Usually a slight excess of the benzene is used to ensure that little or no nitric acid remains in spent acid. Yield is about 98%. Because of a continuous nitration process generally offers lower capital cost and more efficient labor usage than a batch, most if not all of the nitrobenzene produce use continuous process. Benzene nitrating acid (56-65 wt% H2SO4,20-26%HNO3 & 15-18wt% water) are fed into the nitrator, which can be a stirred cylindrical reactor with internal cooling coils and external heat exchangers or cascade of such reactors. The nitator also can be designed as a tubular reactor e.g. tube and shell heat exchangers with appropriate cooling coils involving turbulent flow. Generally, with a tubular reactor the reaction mixture is pumped through the reactor cycle loop and a portion of the mixture is withdrawn and fed into the separator.

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A slight excess of benzene usually is fed into the nitrator to ensure that the nitric acids in the nitrating mixture is consumed to maximum possible extent and to minimize the formation of di-nitrobenzene. the temperature of the nitrator is maintained at 50-100°C by varying the amount of cooling. The reaction mixture flows from the nitrator into separator are centrifuged here is separated into two phases. The aqueous phase or spent acid is drawn from the bottom and concentrated in a sulfuric acid reconcentrated step or recycled to the nitrator where it is mixed with nitric and sulfuric acid immediately prior to being fed into the nitrator. The

crude nitrobenzene is washed and distilled to remove water and

benzene and if required nitrobenzene can be refined by vacuum distillation. ref[3]

SPECIFICATION AND TEST METHODS Specification and test Methods: Specification for double-distilled nitrobenzene are give in table below, Property

Value

Purity ,%

> 99.8

Color

Clear, light yellow to brown

Freezing Point, 0C

> 5.13

Distillation range (First drop), 0C

> 207

Dry point 0C

212

Moisture,%