FORM 2 The Patents Acts, 1970
(39 of 1970) The Patents Rules, 2003
COMPLETE SPECIFICATION
(See Sectionl0;rule l3)
TITLE OF THE INVENTION "NITRATION OF SUBSTITUTED AROMATICS"
APPLICANT
Indian Institute of Technology, Bombay
Powai, Mumbai 400 076
Maharashtra, India
INVENTORS
Prof. Vinaykumar Anant Juvekar, Prof. Sanjay Mahajani and
piwan Ameya Pramod of Department of Chemical Engineering,
Indian Institute of Technology, Bombay, Powai,
Mumbai-400 076, Maharashtra, India;
all Indian Nationals
PREAMBLE OF THE INVENTION
The following specification particularly describes the invention and the manner in which it is to
be performed.

FIELD OF THE INVENTION
The present invention relates to a continuous process for the production of nitrated aromatic compounds by reacting substituted aromatic compounds with a nitrating mixture; wherein the substituted aromatic compounds are soluble in the nitrating mixture i.e. mixture of sulfuric and nitric acid. The instant invention describes a process by which it is possible to reduce the extent of stacking of substituted aromatic molecules by achieving conditions under which the substituted aromatic molecules can be made to react with nitronium ions in nitrating mixture before they undergo stack formation.
BACKGROUND OF THE INVENTION
The process for the production of nitrated aromatics has been a subject of multitude of publications. It is generally known that aromatic compounds can be converted to the corresponding nitro-aromatic compounds with a mixture of sulfuric acid and nitric acid (so called mixed acid or nitrating acid).
Currently, poly-nitration of aromatics is commercially practiced in batch mode and involves severe reaction conditions such as high concentrations of sulfuric acid and high temperatures. This process is inherently unsafe and may lead to explosions. Hence, there is a need to develop a safe and preferably continuous process for poly-nitration.
The inventors of the present invention have identified that many substituted aromatics in sulfuric acid, form stacks due to electron interactions. These stacks have considerably lower reactivity towards nitration compared to un-stacked or free molecules. During the course of the reaction, conditions (e.g. high local temperatures) may arise which can inadvertently destabilize the stacks, thereby causing catastrophic rise in the reactivity leading to explosion. On the other hand, if the reaction is deliberately performed under controlled conditions such that stack formation is either partially or completely suppressed, then it is possible to achieve high rates and still conduct the reaction in safe manner.

Stacking interactions in aromatic compounds have been studied well in the past (e.g. Martin, 1995). In a stack, the electrons of several aromatic rings are shared through resonance thereby leading to enhanced stabilization and hence less reactivity compared to un-stacked molecules. Nitrations are conducted in concentrated sulfuric acid. Nitration rates are dependent on the concentration of nitronium ions which are generated by dissociation of nitric acid. This dissociation is facilitated by sulfuric acid and greater the concentration of sulfuric acid higher is the concentration of nitronium ions and higher is the rate of reaction. However, it has been found that with increase in the concentration of sulfuric acid, the tendency of stacking of substituted aromatics is enhanced. Thus, the increase in the rate due to increased nitronium ions is counterbalanced by the decrease in the reactivity of substituted aromatics due to stacking thereby providing self-regulation of the reaction. This self-regulation is evident from the example of nitration of nitroaromatics, which is very slow and the batch times of the order of hours are needed. However, if the self-regulation is disturbed due to some inadvertent changes in the process parameters (e.g. temperature excursion) which lead to destacking of nitroaromatics, then reaction can become runaway.
US5313009 discloses a continuous process to nitrate an aromatic compound in a nitronium ion. Reactants are brought into intimate contact in a plug-flow type of reactor that contains mixing elements. The process comprises feeding into the reactor the nitronium ion solution of a composition within an area defined by connecting three points in a ternary phase diagram of nitric acid, sulfuric acid and water. The three points correspond to first about 82% of sulfuric acid and 18% nitric acid, secondly about 55% sulfuric acid and about 45% water and, thirdly, 100% sulfuric acid, with the nitric acid preferably being below about 3%. The nitratable aromatic compound is introduced in a manner such that a fine emulsion of hydrocarbon in the nitronium ion solution is formed with the hydrocarbon evenly distributed in the acid phase. The process described here, refer to aromatic compounds which are immiscible in nitrating mixture. Hence, the mixing process described here is to enhance the degree of emulsion, which is essentially an immiscible mixture of hydrocarbon and mixed acid.

US5616818 discloses a continuous process for polynitration of an aromatic compound in a single apparatus under adiabatic conditions in an emulsion as the reaction medium. From 1.3 to 3.5 mol of HNO3 per mol of aromatic compound are introduced in the form of a nitronium ion solution into the reactor with the aromatic compound under conditions such that an emulsion forms. The emulsion, which has a tendency to coalesce, is maintained by repeated dispersion. The first dispersion of the liquid streams to produce the emulsion takes place in less than one second. At least 20% of the total amount of HNO3 to be used should generally be present during this first dispersion. It is preferred, however, that the total amount of nitronium ion solution to be used be present at the time the aromatic compound and nitronium ion solution are first dispersed.
In both the above patents, the reaction is performed in heterogeneous mode (two liquid phases) and are applicable to nitration of aromatic hydrocarbons, which are immiscible with nitrating mixture.
Accordingly, the inventors of the present invention have endeavoured to provide a rapid and robust method for nitration of substituted aromatics, which are soluble in the nitrating mixture, wherein, high intensity of turbulence at the point of dissolution of aromatic compound in the mixed acid results in very low local concentration of aromatic compound which slows down the stack formation process and thereby substantially enhances the rate of nitration.
Accordingly, the present inventors report a convenient and safe method of nitrating substituted aromatics, which are soluble in mixed acid, as described in the instant invention which is economical, efficient and easily scalable.
SUMMARY OF THE INVENTION
In an aspect, the present invention provides a continuous process for nitration of a substituted aromatic compound comprising:
a. providing the substituted aromatic compound which is soluble in a nitrating mixture;
b. intensively mixing and reacting the substituted aromatic compound with the nitrating
mixture in a mixing apparatus for a mixing time of 0.001-100 milliseconds, wherein a
high intensity of turbulence at the point of dissolution of the substituted aromatic

compound in the nitrating mixture results in very low local concentration of the substituted aromatic compound which slows down the stack formation process and thereby enhancing the rate of nitration.
OBJECT OF THE INVENTION
It is an object of the present invention to provide a process for the nitration of substituted aromatic compounds, which are soluble in the nitrating mixture, in a continuous mode by achieving conditions under which the substituted aromatic molecules can be made to react with nitronium ion before they undergo stack formation.
It is the particular object of the present invention to either partially or completely suppress stack formation so as to achieve high rates, yet conduct the reaction in a safe manner.
It is also an object of the present invention to provide a process that is inherently safe and devoid of the risks of explosion hazards.
These and other objects which will be apparent to those skilled in the art are accomplished by reacting a substituted aromatic compound with a nitronium ion solution such that high intensity of turbulence at the point of dissolution of the substituted aromatic compound in the nitrating mixture results in a very low local concentration of the substituted aromatic compound which slows down the stack formation process. Also, because of the high reactivity of unstacked molecules, reaction can be completed in extremely short time (of the order of seconds). By conducting the reaction in a continuous mode and efficiently removing the heat of reaction, it is possible to completely avoid runaway conditions.
BRIEF DESCRIPTION OF DRAWINGS
The foregoing summary, as well as the following detailed description of the invention will be better understood when read in conjunction with the appended drawings. For the purpose of assisting in the explanation of the invention, there are shown in the drawings embodiments

which are presently preferred and considered illustrative. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown therein. In the drawings:
Figure 1: Schematic representation of the reaction setup
Figure 2: Effect of mixing time on the rate constant, showing the effect of intensity of mixing. Temperature: 25± 1 °C; H2S04 - 90%, CNBj = 0.24 mol/L, CHN03i= 2.2 to 2.5 mol/L
DETAILED DESCRIPTION OF THE INVENTION
In describing and claiming the invention, the following terminology will be used in accordance with the definitions set forth below. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein. As used herein, each of the following terms has the meaning associated with it in this section. Specific and preferred values listed below for individual process parameters, substituents, and ranges are for illustration only; they do not exclude other defined values or other values falling within the preferred defined ranges.
As used herein, the singular forms "a," "an," and "the" include plural reference unless the context clearly dictates otherwise.
The terms "preferred" and "preferably" refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

When the term "about" is used in describing a value or an endpoint of a range, the disclosure should be understood to include both the specific value or end-point referred to.
As used herein, the terms "comprises", "comprising", "includes", "including", "containing", "characterized by", "having" or any other variation thereof, are intended to cover a non-exclusive inclusion.
As used herein, the term "aromatic compound" or "aromatic molecule" refers to a compound or a molecule comprising an aromatic ring system which may be mono-, bi- or tricyclic as well as heterocyclic. Examples of such ring systems include phenyl, naphthalenyl, anthracenyl, pyridinyl, quinolyl and phenanthrenyl. The aromatic compound to be nitrated according to the process of the present invention may be substituted with one or more substituents such as but not limited to alkyl, aryl, nitro, halo, carboxy, carboxyalkyl, carbonyl, and should be soluble with the nitrating mixture under the conditions of interest.
As used herein, the term "substituted aromatic" refers to an aromatic compound containing one or more functional groups such as but not limited to alkyl, aryl, nitro, halo, carboxy, carboxyalkyl, carbonyl in place of hydrogen atom or atoms of the aromatic ring. For example, "nitroaromatic" refers to an aromatic compound containing one or more nitro groups (-NO2) in place of a hydrogen atom or atoms of the aromatic ring.
As used herein, the term "alkyl" refers to a saturated straight or branched chain consisting of 1-10 carbon atoms; preferably, 1-6 carbon atoms. Examples of the "alkyl" group may include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, iso-amyl, hexyl or decyl.
As used herein, the term "aryl" refers to monocyclic or bicyclic aromatic hydrocarbon groups having 6 to 12 carbon atoms in the ring portion, such as phenyl, naphthyl, biphenyl and diphenyl groups.

As used herein, the term "heterocyclic" or "heteroaryl" refers to an aromatic group, for example, which is a 4 to 7 membered monocyclic, 7 to 11 membered bicyclic, or 10 to 15 membered tricyclic ring system, which has at least one heteroatom in at least one carbon atom-containing ring. Each ring of the heterocyclic group containing a heteroatom may have 1, 2 or 3 heteroatoms selected from nitrogen atoms, oxygen atoms and sulfur atoms, where the nitrogen and sulfur heteroatoms, for example, pyridine, quinoline. The heterocyclic compound to be nitrated according to the process of the present invention may be substituted with one or more substituents such as but not limited to alkyl, aryl, nitro, halo,, carboxy, carboxyalkyl, carbonyl, and should be soluble with the nitrating mixture under the conditions of interest.
As used herein, the term "heteroatoms" shall include oxygen, sulfur and nitrogen.
As used herein, the term "halogen" or "halo" refers to fluorine, chlorine, bromine and iodine.
As used herein, the term "carboxy" refers to -COO group.
As used herein, the term "carbonyl" refers to -C=0 group.
As used herein, the term "carboxyalkyl" refers to -COO(alkyl) group wherein the term "alkyl" is as defined above.
As used herein, the term "nitration" refers to a chemical process for the introduction/inclusion of a nitro group (-NO2) into an aromatic compound.
As used herein, the terms "mixed acid" or "nitrating acid" or "nitrating mixture" refers to a mixture of concentrated nitric acid (HNO3) and sulfuric acid (H2SO4) with water content of 0% to 15% by weight as well as oleum (mixture of sulphuric acid and sulphur trioxide). This mixture produces the nitronium ion (-NO24), which is the active species in aromatic nitration reaction.
As used herein, the terms "stack formation" or "stacking interaction" refers to the favourable non-covalent attractive interactions between two aromatic ring systems, wherein the two rings

are juxtaposed such that they are oriented either face-to-face (parallel), perpendicular or at an intermediate angle to each other.
As used herein, the terms "turbulent" or "turbulence" broadly denotes a very efficient mixing of the reaction mixture.
As used herein, the term "mixing time" refers to the time required for complete mixing of two or more fluids which are miscible (soluble) with each other to form a mixture having spatially uniform composition.
As used herein, the term "non-isothermal condition" refers to a condition under which temperature varies along the length of the reactor.
The present invention provides a continuous process for nitration of a substituted aromatic compound comprising:
a. providing the substituted aromatic compound which is soluble in a nitrating mixture;
b. intensively mixing and reacting the substituted aromatic compound with the nitrating
mixture in a mixing apparatus for a mixing time of 0.001-100 milliseconds, wherein a
high intensity of turbulence at the point of dissolution of the substituted aromatic
compound in the nitrating mixture results in very low local concentration of the
substituted aromatic compound which slows down the stack formation process.
The substituted aromatic compounds of the present invention are soluble in the nitrating mixture. Non limiting examples of the substituted aromatic compound which can undergo nitration reaction include nitrobenzene, nitrotoluene, benzoic acid, phenyl acetic acid, o- and p-nitrobenzoic acid, p-benzoyl diphenyl, pyridine, alkylpyridine, quinoline, alkylquinoline or derivatives thereof.
The nitrating mixture used in the process of the present invention is prepared according to the following steps:

a. providing a mixture of 85% to 100% by weight sulfuric acid and 0% to 15% by weight
water or oleum which is a mixture of sulfuric acid and sulfur trioxide comprising 0% to
65% w/w of free sulfur trioxide;
b. providing either a pure nitric acid or a mixture of water and nitric acid comprising water
from 0% to 99% by weight; and
c. mixing the mixture of step (a) with step (b) in a ratio of 100:1 to 1:1.
In an embodiment of the present invention, the nitrating mixture (mixed acid) comprises sulfuric acid, water, sulphur trioxide and nitric acid such that ratio of water to sulphuric acid 0 to 0.2 (w/w) and ratio of nitric acid to sulphuric acid 10-6 to 10 (w/w) and ratio of sulphur trioxide to sulphuric acid 0 to 10 (w/w).
Preferably, the mixed acid has a composition of 81.7% sulfuric acid, 8.92% nitric acid and rest water on weight basis.
The molar ratio between the aromatic compound (substituted aromatic compound) and nitric acid in the mixed acid is selected on the basis of the desired degree of nitration. The molar ratio of nitric acid to aromatic compound (substituted aromatic compound) in this solution may be maintained at from about 1 to about 15, preferably from about 1.5 to about 12 and most preferably from about 1.7 to about 10.
The temperature of the mixing apparatus is determined by the mixing temperature and by the rise in temperature of the highly exothermic reaction. In the process of the present invention, the temperature is generally between 20°C and 100°C. In a preferred embodiment, the mixing temperature of the reactants in the mixing apparatus is between 25°C and 90°C, preferably between 30°C and 80°C.
In an embodiment of the present invention, the aromatic compounds are polynitrated (i.e., dinitrated or nitrated to a higher degree). Trinitrated aromatic compounds may also be produced by the process of the present invention.

In an embodiment of the present invention, the process of the present invention can be operated under both isothermal as well as non-isothermal conditions.
In an embodiment of the present invention, the process of the present invention is carried out continuously.
The mixing apparatus used in the process of the present invention may be selected from a group consisting of T-mixer, Y-mixer, nozzle mixer, serpentine mixer, venturi mixer, micro jet mixer, collision mixer, in-line mixer, static mixer, pump mixer, high shear in-line mixer, jet mixer and micro-mixer. The mixing apparatus used in the process of the present invention are those which offer substantially high intensity of mixing so that the mixing time is in the range of 0.001 to 100 milliseconds, preferably 1 millisecond.
In an embodiment of the present invention, the mixing apparatus used in the process of the present invention are those which offer substantially a high Peclet number of 10 to 1000, preferably 100-1000 and a Strouhal number of 0.1 to 10, preferably 8-10.
The process according to the present invention results in shorter reaction times and higher yields of the desired nitration compound. The higher yields are associated with partial or complete suppression of stack formation. Also, because of the high reactivity of unstacked molecules, the reaction can be completed in extremely short time (of the order of seconds). By conducting the reaction in a continuous mode and efficiently removing the heat of reaction, it is possible to completely avoid runaway conditions. Furthermore, the process of the present invention is inherently safe and devoid of the risks of explosion hazards.
In an embodiment of the present invention, the mixing time in mixing apparatus is in a range of 0.001-100 milliseconds. At the mixing time of 10 milliseconds the rate is 100 times that observed in a conventional batch reactor wherein, stacking cannot be avoided.
Mixing time is calculated as the ratio of total volume of the mixing apparatus to the total volumetric flow rate of the liquid (mixed acid stream + aromatic compound stream). The rate

constant is calculated by the following equation assuming that the flow follows plug flow behaviour.

k = -— In
(M - x)
CArH{M-Y) \M{\-x)

wherein, k is the second order rate constant in lit/mols/min, M is the mole ratio of nitric acid to aromatic compound in the feed, CACH is the molar concentration of the aromatic compound in the feed and x is the fractional conversion of aromatic compound.
In an embodiment of the present invention, the intensity of mixing can be enhanced by increasing the flow rate of the mixed acid. Higher the flow rate greater is the intensity of mixing.
In an embodiment of the present invention, the final conversion of the substituted aromatic compound varies with the increase in the temperature for a given mixing time.
In an embodiment of the present invention, the resultant reaction mixture obtained from step (b) may optionally be quenched in a cooling water bath; wherein the temperature of the cooling water bath is maintained at 25±1°C.
In an embodiment of the present invention, the process comprises isolating a desired nitration product from the resultant reaction mixture.
In a preferred embodiment, the substituted aromatic compound is a nitroaromatic compound. The process for the nitration of nitroaromatic compounds in carried out in a continuous mode by achieving conditions under which the nitroaromatic molecules can be made to react with nitronium ion before they undergo stack formation.
The reaction chemistry for the nitration of nitroaromatic compound is as follows: Stoichiometrv:
N02ArH + HN03 ► ArH(N02)2 + H20

wherein, N02ArH - Nitro-aromatic compound
Generation of nitronium ion
HN03 + H+ << ► H2N03+ < * H20 + N02+ (extremely fast)
Attack ofN02+ ion on aromatic hydrocarbon
N02ArH + N02+ —► N02 Ar—H+ —► ArH(N02)2 + H+
(slow) I (fast)
N02+
The nitroaromatic compounds of the present invention are soluble in the nitrating mixture. Non limiting examples of the nitroaromatic compound which can undergo nitration reaction include nitrobenzene, nitrotoluene, 0- and p-nitrobenzoic acid, or derivatives thereof.
The process of the present invention is inherently safe and explosion hazards are eliminated. Extremely large reaction rates encompassed by the present invention bring down the total reactor volume and the plant size by orders of magnitude. All the benefits of the continuous process such as consistent product quality, large production rates etc. are realized by the process of the present invention.
The following examples are provided to better illustrate the claimed invention and are not to be interpreted in any way as limiting the scope of the invention. All specific materials and methods described below, in whole or in part, fall within the scope of the invention. These specific compositions, materials, and methods are not intended to limit the invention, but merely to illustrate specific embodiments falling within the scope of the invention. One skilled in the art may develop equivalent materials, and methods without the exercise of inventive capacity and without departing from the scope of the invention. It will be understood that many variations can be made in the procedures herein described while still remaining within the bounds of the invention. It is the intention of the inventors that such variations are included within the scope of the invention.

EXAMPLE 1:
Nitration of Nitrobenzene
As a representative example of the present invention the nitration of nitrobenzene by mixed acid is conducted in a continuous mode using a T-mixer followed by rapid quenching (Refer Figure
I).
Nitrobenzene and mixed acid stored in separate bottles are pumped with the help of peristaltic
pumps through the T-mixer immersed in a well-mixed cooling water bath. The nitration reaction
occurs in the T-mixer. The effluent of the T-mixer is quenched in ice wherein, organic phase
containing unreacted nitrobenzene and the product, dinitrobenzene (mainly meta-dinitrobenzene
and small amounts of ortho- and para-dinitrobenzene) separates out. The organic phase is
analyzed on HPLC to determine concentration of all the species, from which the conversion is
determined.
NO.

Temperature of the cooling bath is maintained at 25±1°C. The T-mixer is made up of stainless steel and has a volume of 7.5 µL and the internal diameters of the arms of the T are 1/32 inch each. The flow rates of both nitrobenzene and mixed acid streams are varied over 0.3-3.6 g/min and 5 x 10'3 - 7.5 x 10"2 g/min, respectively. The mixed acid has a composition of 81.7% sulfuric acid, 8.92% nitric acid and rest water on weight basis. Conversion of nitrobenzene is varied from 0.75% to 15%.
The intensity of mixing can be enhanced by increasing the flow rate of the mixed acid. Higher the flow rate greater is the intensity of mixing. The mixing time in the T-mixer is in a range of 0.001-100, preferably in the range of 10-100 milliseconds. At the lowest mixing time of 10

milliseconds the rate is 100 times that observed in a conventional batch reactor wherein, stacking cannot be avoided.
Mixing time is calculated as the ratio of total volume of the T-mixer to the total volumetric flow rate of the liquid (mixed acid stream + nitrobenzene stream). The rate constant is calculated by the following equation assuming that the flow follows plug flow behaviour.
■ 1 , KM-*)"
CNBQ(M-l)n[M(l-x)wherein, k is the second order rate constant in lit/mols/min, M is the mole ratio of nitric acid to nitrobenzene, CNBO IS the molar concentration of nitrobenzene in the feed and x is the fractional conversion of nitrobenzene.
The circles in the figure 2 below show the variation in the rate constant with respect to the mixing time in the reactor. In this case, the nitrobenzene used is neat. Low mixing time is achieved by using high flow rate of fluid, which enhances the mixing and hence the rate of the reaction, at given concentrations of nitric acid, sulfuric acid and nitrobenzene. The enhanced mixing reduces stacking, and is thus responsible for high rates. If nitrobenzene is mixed with sulfuric acid and allowed to stand for sufficient time (process of aging) then it undergoes stacking. If this stacked nitrobenzene is used for the reaction, then the rate constant is very low as seen in the figure 2 (see squares).

We Claim:
1. A continuous process for nitration of a substituted aromatic compound comprising:
a. providing the substituted aromatic compound which is soluble in a nitrating
mixture;
b. intensively mixing and reacting the substituted aromatic compound with the
nitrating mixture in a mixing apparatus for a mixing time of 0.001-100
milliseconds, wherein a high intensity ofturbulen.ee at the point of dissolution of
the substituted aromatic compound in the nitrating mixture results in very low
local concentration of the substituted aromatic compound which slows down the
stack formation process.
2. The process as claimed in claim 1, wherein a process for the preparation of the nitrating
mixtures comprises:
a. providing a mixture of 85% to 100% by weight sulfuric acid and 0% to 15% by
weight water or oleum which is a mixture of sulfuric acid and sulfur trioxide
comprising 0% to 65% w/w of free sulfur trioxide;
b. providing either a pure nitric acid or a mixture of water and nitric acid comprising
water from 0% to 99% by weight; and
c. mixing the mixture of step (a) with step (b) in a ratio of 100:1 to 1:1.
3. The process as claimed in claim 1, wherein the substituted aromatic compound is selected
from a group consisting of nitrobenzene, nitrotoluene, benzoic acid, phenyl acetic acid,
o- and p-nitrobenzoic acid, p-benzoyl diphenyl, pyridine, alkylpyridine, quinoline,
alkylquinoline or derivatives thereof.
4. The process as claimed in claim 1, wherein the mixing apparatus is selected from a group consisting of T-mixer, Y-mixer, nozzle mixer, serpentine mixer, venturi mixer, micro jet mixer, collision mixer, in-line mixer, static mixer, pump mixer, high shear in-line mixer, jet mixer, micro-mixer.

5. The process as claimed in claim 1, wherein the mixing apparatus exhibits mixing time of 0.001-100 milliseconds.
6. The process as claimed in claim 1, wherein the molar ratio of nitric acid to substituted aromatic compound is from 1 to 15.
7. The process as claimed in claim 1, wherein temperature of the mixing apparatus is between 20°C and 100°C.
8. The process as claimed in claim 1, wherein the reaction is carried out under isothermal and non-isothermal conditions.
9. The process as claimed in claim 1, comprises isolating a desired nitration product.