1.Introduction & History :1.1 Introduction to aniline :Structure:- Aniline is an organic compound with chemical formula of C6H7N or C6H5NH2. Aniline has 6 Carbon atoms , 7 Hydrogen atoms & 1 Nitrogen atom. Aniline is made up of two groups :1. Phenyl group 2. Amino group As per above figure the phenyl group (boxed in blue) is attached to the amino group (boxed in red). Aniline has a Phenyl group, so we can say that it is an aromatic & it also contain Amino group, so it also means it is an Amine. Aniline is a prototypical Aromatic Amine. Aniline is a flammable liquid chemical having pungent unpleasant odour and is slightly soluble in water. It can be colourless to brown, and it is oily in nature 1.2 History of Aniline :- Aniline was first separated in 1826 by Otto Unverdorben by destructive distillation of Indigo and called it crystalline. In 1834, Friedlieb Runge separated Aniline from Coal tar. When it is treated with chloride of Lime it gives beautiful blue colour & named it ‘Kyanol' In 1840 Carl Julius Fritzsche (1808-1871) treated Indigo with caustic potash & obtained an oil and named it Aniline. In 1842 Nikolai Nikolaevid Zinin converted Nitro Aromatics like Nitrobenzene to amines by reduction with Sodium Sulfides & obtained Aniline. ARNO2 + 3H2S -------》 ARNH2 + 3S + 2H2O In 1843, August Wilhelm Von Hofmann showed that all these substance are same, known there after as Phenyl Amine or Aniline. In 1856, Sir William Henry Perkin, a student at Royal college of chemistry in London, partially transformed Aniline into a crude mixture which when extracted with Alcohol, produced a substance with an intense purple colour. Perkin further carried out trials with his friend and his brother and satisfied themselves that they might be able to scale up production of the purple substance and commercialise it as a dye which they called Mauveine. This process was to become one of the first commercial process to generate o synthetic organic chemical. During the last three decades, polyurethane plastics have emerged as a growth industry and aniline once again plays a key role as an industrial intermediate used in the manufacture of MDI, 4,4’-diphenylmethane diisocyanate, a key commercial monomer in the manufacture of polyurethane plastics. 2.properties of Aniline :2.1 Physical Properties :PROPERTY VALUE Molecular formula C6H7N Molecular weight Boiling point, 0C (@101.3 K pa) 93.129 184.4 Critical temperature 425.6*c Odour Aromatic. Amine like Physical state and appearance Oily liquid Freezing point -6.03*c Taste Burning Refractive Index 1.5863 Viscosity mpa.s(=cp) - 20*c 4.35 60*c 1.62 Enthalpy of dissociation, kj/mol 21.7 Heat of combustion, kj/mol 3394 Ionisation potential, Ev 7.70 Dielectric constant, at 25*c 6.89 Specific heat , at 25*c, j/(g.k) 2.06 Heat of vaporisation, j/g 478.5 Flash point (close cup) 70 2.2 Chemical Properties : Amines are bases because the lone pair of electrons on the nitrogen atom can accent a hydrogen ion –in other words, for exactly the same reason ammonia is a base. 2.2.1 The reaction of aniline with acids: Aniline reacts with acids like hydrochloric acid in exactly the same way as any other amine. Despite the fact that the aniline is only a very weak base, with a strong acid like HCL the reaction is completely straightforward. Aniline is only very slightly soluble in water but dissolved freely in dilute HCL. A solution of salt is formed aniline chloride salt. 2.1.3. Reaction of aniline with Halogen (CL, I, BR, F) group: The presence of the amino group activates the ortho and para positions of the aromatic ring and, as a result, aniline reacts readily with bromine or chlorine. Under mild conditions, bromination yie lds 2,4,6- Tribromo aniline. Recovery of aniline from aniline salt To get the aniline back from phenyl ammonium ion present in the salt, all you have to do is to take the hydrogen ion away again. You can do that by adding any strong base. Normally you would choose sodium hydroxide solution. 2.1.3 Condensation: - Depending on the reaction conditions, a variety of condensation products are obtained from the reaction of aromatic amines with aldehydes, ketones, acetyls, and orthoformate. Primary aromatic amines react with aldehydes to form Schiff bases. Schiff bases formed from the reaction of lower aliphatic aldehydes, such as formaldehyde and acetaldehyde, with primary aromatic amines are often unstable and polymerize readily. Aniline reacts with formaldehyde in aqueous acid solutions to yield mixtures of a crystalline timer of the Schiff base, methylenedianilines, and polymers. 2.1.4 Oxidation: - Aniline was selectively converted into the corresponding nitroso benzene and nitrobenzene by oxidation with 30% aqueous hydrogen peroxide. The reaction was catalysed by various heteropolyoxometalates, at room temperature, in dichloromethane under two-phase conditions. Findings show that H3PW12O40 is the best catalyst in the oxidation of aniline. 3.Use of Aniline: The largest application of aniline is for the preparation of methylene dianiline and related compounds by condensation with formaldehyde. Asadditives to rubber, aniline derivatives such as Phenylenediamines & Diphenylami4ne are antioxidants. Illustrative of the drugs prepared from aniline is paracetamol. The principal use of aniline in the dye industry is as a precursor to indigo, the blue of blue jeans. Some early American rockets, such as the Aerobee and WAC Corporal, used aniline with furfuryl alcohol as a fuel with nitric acid Anilines are used in the rubber industry for the processing of rubber chemicals and products such as car tyres, balloons, gloves, etc. It is used as a dyeing agent in the manufacture of clothes such as jeans, etc It is employed in the production of drugs such as paracetamol, Tylenol, acetaminophen. It is used as a pesticide and fungicides in the agricultural industry It is used for the manufacture of its some derivatives such as acetamide, sulphanilic acid and sulpha drugs, etc. It is used as an accelerator in vulcanizing rubber. Aniline, a primary aromatic amine, is a weak base and forms salts with mineral acids. 4. List of Manufacturing Process :- 4.1. From Nitrobenzene: Nitrobenzene is the classical feedstock for Aniline manufacture. Recently less Chlorobenzene and Phenol are being used in aniline manufacturing processes in several countries. The reduction of nitrobenzene with iron turnings and water in the presence of small amounts of hydrochloric acid is the oldest form of industrial aniline manufacture. It would certainly have been replaced much earlier by more economical reduction methods if it had not been possible to obtain valuable iron oxide pigments from the resulting iron oxide sludge. However, the increasing demand for aniline has far surpassed the market for the pigments, so that not only catalytic hydrogenation processes (both liquid- and gas-phase) but also other feed stocks have been used for aniline production. The modern catalytic gas-phase hydrogenation processes for nitrobenzene can be carried out using a fixed-bed or a fluidized-bed reactor: Rayer and Allied work with nickel sulfide catalysts at 300-475 °C in a fixed bed. The activation of the hydrogenation catalysts with Cu or NI, and the use of different supports and catalyst sulfidization methods with sulfide, H2S or CS2 all belong to the expertise of the corresponding firms. The selectivity to aniline is more than 99%. 4.2. From Chlorobenzene: An alternate manufacturing route for aniline is the ammonolysis of chlorobenzene or of phenol. For example, in the Kanto Electrochemical Co. process, chlorobenzene is ammonolyred to aniline with aqueous NH3 at 180-220 °C and 60-75 bar in the presence of Cucl and NH3Cl (Niewland catalyst). Aniline can be isolated with 91 % selectivity from the organic phase of the two-phasereaction product. 4.3. From Phenol: Dow stopped operation of a similar process for aniline in 1966. Phenol can also be subjected to gas-phase ammonolysis with the Halcon/Scientific Design process at 200 bar and 425 °C Al2O3.SiO2 (possible as zeolites) and oxide mixtures of Mg, B, Al, and Ti are used as catalysts; these can be combined with additional co catalysts such as Ce,V, or W. The catalyst regeneration required previously is not necessary with the newly developed catalyst. With a large excess of NH3, the selectivity to aniline is 87-90% at a phenol conversion of 98%. The byproducts are diphenylamine and carbazole. This process has been operated since 1970 by Mitsui Petrochemical in a plant which has since been expanded to 45 000 tonnes per year. A second plant with a capacity of 90000 tonnes per year was started up by US Steel Corp. (now Aristech) in 1982. 4.4. From Benzene: Du Pont has developed an interesting manufacturing process for aniline. Benzene and NH3 can be reacted over a NiO/Ni catalyst containing promoters including zirconium oxide at 350°C & 300 bar to give a 97% selectivity to aniline with benzene conversion of 13% Since the hydrogen formed in the reaction reduces the NiO part of the catalyst, a catalyst regeneration (partial oxidation) is necessary. Despite inexpensive feedstocks, industrial implementation is still thwarted by the low benzene conversion and the necessary catalyst reoxidation. 5. Most suitable process : The catalytic Hydrogenation of Nitrobenzene to Aniline gives selectivity more than 99%, better than other manufacturing processes. Nitrobenzene is the classical feedstock for Aniline manufacture. The method process is simple, inexpensive catalysts, long life, from product quality, After preheating the hydrogen and nitrobenzene, hydrogenation reaction occurs. Fixed bed gas phase catalytic hydrogenation process has a matured technology, the reaction temperature is lower, equipment has easy operation, low maintenance costs, less investment, without separation of catalyst, good product quality; deficiency is, the reaction pressure is more prone to occurrence of local side effects caused by overheating and catalyst deactivation, the catalyst must be periodically replaced. Currently, most foreign manufacturers of fixed-bed use gas phase aniline hydrogenation process. Flowsheet: - PROCESS DESCRIPTION: The main process for aniline production is the nitrobenzene hydrogenation reaction. First of all liquid nitrobenzene is vaporized into vaporizer to reach the required temperature for fluidized bed reactor. Then vaporized nitrobenzene is mixed with compressed hydrogen in 1:9 proportion and sent to fluidized bed reactor. In fluidized bed reactor the nitrobenzene is converted to Aniline in presence of copper catalyst at 270 c and 1.5 atm pressure. The reaction is highly exothermic so cooling jacket is provided to maintain the temperature of the reactor. The conversion of the nitrobenzene in reactor is 99.7% and the selectivity to aniline is 99%. The reactor product gas mixture (Aniline, hydrogen and water) is sent to condenser Hydrogen is recovered and sent to compressor for reuse. Moreover, the aqueous (water) and organic phase (crude aniline) is separated in decanter which separates the crude aniline from the aqueous phase solution. The organic phase (crude aniline) is consist of aniline up to 0.5% nitrobenzene, and 5% water which is purified by two stage distillation column. The crude aniline from decanter is sent to distillation column 1 where we get aniline and water from overhead while higher boiling organic impurities, such as nitrobenzene remains in the still which is recycled to decanter. The overhead product from the first column is purified in finishing still where water is obtains from overhead while aniline is withdrawn in a side stream near the bottom of the column. The bottom is recycled to decanter. We get 99.5% aniline from this process at the end of purification of crude aniline.