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Project: design of a reactor for the aniline production

PROJECT: DESIGN OF A REACTOR FOR THE ANILINE PRODUCTION.

Jairo Arango Urueña1, Juan Camilo Tirado Varela1, Luis Esteban Vásquez Castañeda1.
1
Estudiantes de ingeniería química, Facultad de Ingeniería Universidad de Antioquia, Medellín,
Colombia, 7th September 2018.

1. ABSTRACT:

An investigation was made about the main parameters for the implementation of an aniline
production plant in Colombia. It was started with the definition of the chemical route: catalytic
hydrogenation in vapor phase, due to its fixed bed configuration; use of palladium catalyst
supported on oxidic support and its phase, which avoids product-catalyst separation, extending the
life of it; these characteristics allow yields higher than 99% in addition to high activity and
selectivity. The selection was made based on the evaluation of certain parameters of a selection
matrix that could easily be grouped into four broad groups: environment, efficiency, costs and
safety; being the latter the one that gained more relevance in the choice of the route. Likewise, all
the information related to the properties of the substances involved was extracted from the
literature, as well as the kinetics of the reaction. Finally, knowing the chemical and physical nature
of the substances, and the conditions of operations, the type of reactor to be used and the capacity
of the plant were selected.

Keywords: Aniline, Fixed bed reactor, Catalyst, Catalytic hydrogenation in vapor phase, kinetics

2. INTRODUCCIÓN:

Green chemical synthesis has been of signifi cant interest for the development of safe and efficient
reaction processes that reduce the generation of hazardous products and for economic benefi ts in
the chemical industry. One process that has widely attracted the attention is the direct synthesis of
aniline. Aniline (C6H5NH2 ) is an important building block in the chemical industry as it can
undergo numerous reactions involving either the amino group or the aromatic ring. These reactions
can be extended for various industrial applications including the production of dyes, the production
of polyurethane, use in the rubber industry, and in the manufacturing of pharmaceuticals, to name
a few [1][2].
In 2013, the global annual production of aniline was approximately 5 million tons and was
anticipated to reach 6.2 million tons by 2015[2]. Eighty percentage of aniline goes to the production
of methylene diphenylene isocyanate, which is usedin the manufacturing of polyurethane [1].
At present the mass production of aniline demands a safe, efficient and economically viable process
and although the first technically applicable process for the production of aniline (Bechamp
process) was developed in 1854, from the reduction of nitrobenzene, the process is still in force,
being the most used around the world, due to the research and development that has managed to
implement small improvements that maintain it as a process with high performance, activity and
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Project: design of a reactor for the aniline production

selectivity.
Now the most commonly used aniline synthesis commercially starts with benzene. There is a
bibliography on the direct amination of the benzene, but the high temperatures and pressures
required as well as the requirement to use a large excess of ammonium has not allowed the
development of an economic process. Until now, all the techniques applied in the synthesis of
aniline use an indirect way to produce it from benzene. In all cases, a derivation class is included
as an intermediate step. In this stage one of the two direct precursor of the aniline is formed:
nitrobenzene or phenol [3].
In the vapor phase process, the nitrobenzene is hydrogenated to aniline with a yield, usually of
more than 99%, using a fixed or fluidized bed. The most effective catalyst in this case seems to be
copper or palladium on activated carbon or an oxidic support, combined with other metals (Pb, V,
P, Cr) as promoters to achieve high activity and selectivity [3].

3. PARAMETERS FOR SELECTION OF CHEMICAL ROUTE AND CONDITIONS OF

OPERATION:

3.1 Chemical routes of obtaining the product of interest:

Nitrobenzene is used as raw material to obtain aniline, by all the world producers, with the
exception of Mitsui Petrochemicals Ind. (Japan) which also uses phenol and Aristech Chemical
Corp. (U.S) that only use phenol [3].

3.1.1 Catalytic hydrogenation of nitrobenzene:

The catalytic hydrogenation of nitrobenzene is a highly exothermic reaction (ΔH = -544 KJ/mol at
200 °C) that can be carried out both in the vapor phase and in the liquid phase, in commercially
used processes.

The exchange and use of heat of reaction is a crucial point for all processes that use nitrobenzene
as raw material.

3.1.1.1. Catalytic hydrogenation in vapor phase

In the vapor phase process, nitrobenzene is hydrogenated to aniline with a yield, normally, of more
than 99%, using a fixed or fluidized bed. The most effective catalyst in this case seems to be copper
or palladium on activated carbon or an oxidic support, combined with other metals (Pb, V, P, Cr)
as promoters to achieve high activity and selectivity.

In the Lonza process a homogeneous feed of hydrogen and nitrobenzene is passed over a fixed bed
of copper catalyst with an inlet temperature of about 200 °C. The molar ratio between the fed
nitrobenzene and the total hydrogen is 1:1000 at the reactor inlet. The reaction products leave the
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Project: design of a reactor for the aniline production

reactor at a temperature above 300 °C. The heat of the hydrogenation is used to produce steam and
to heat the recirculated gas stream. The reactor outlet is cooled in a condenser; then, excess
hydrogen, crude aniline and water are separated. Finally, the aniline is purified by distillation.

Bayer operates with conventional fixed-bed reactors using a palladium catalyst on an aluminum
support, whose activity is modified by the addition of vanadium. In a recent improvement, the
hydrogenation of nitrobenzene is sought on a fixed catalyst bed of 1.5 to 4% by weight of palladium
in coke with 0.1 to 2% by weight as a modifier to reduce the aromatic ring. At the pressure of 100-
700 kPa a mixture of vaporized nitrobenzene and hydrogen in a ratio of 1:120 to 1:200 is fed to the
adiabatic reactor with an inlet temperature of 250-350 ° C. The height of the catalyst bed in the
reactor is 0.1 to 1 m. The reaction products leave the reactor without cooling at a maximum
temperature of 460 °C. Next, the heat of reaction is used to produce high pressure steam. The
production unit can be built by means of several adiabatic reactors in series or in parallel. After
cooling to 140 or 180 °C, the outlet of the last reactor is fed to a separation unit where again the
crude aniline, the waste water and the recirculated hydrogen are separated under pressure. The
aniline is purified by distillation.

3.1.1.2. Catalytic hydrogenation in liquid phase:

The industrial processes ICI and Dupont for the manufacture of anilines involve the hydrogenation
of nitrobenzene in the liquid phase. This hydrogenation process operates at 90-200 ºC and 100-600
kPa. The reaction in liquid phase must be carried out in fluidized bed reactors. Normally a
conversion of 98 to 99% is achieved.
In 1960, ICI a continuous process of hydrogenation in liquid phase, which uses aniline as a solvent
in a proportion greater than 95% by weight of the liquid phase. Operating in the conditions close
to the boiling point of the solvent, all or almost the heat of the reaction dissipates the evaporation
of the reaction mixture. The water is removed with the effluent vapors and the aniline necessary to
obtain the reaction to maintain the conditions of the steady state.

Dupont hydrogenates the nitrobenzene in the liquid phase using a platinum-palladium catalyst on
a carbon support with iron as a modifier. This provides the catalyst with a long life, high activity
and protection against the hydrogenation of the aromatic rings. The continuous process uses a
piston flow reactor that allows a good performance to be achieved and the product obtained is
practically free of nitrobenzene.

3.1.1.3 Comparison between Catalytic hydrogenation in liquid and vapor phase:

The comparison between the hydrogenation of nitrobenzene in the liquid phase and the vapor phase
shows almost no differences in performance and product quality for both processes. But, the liquid
phase process has the advantage of high space-time performance and also does not need a loop of
recirculated gas due to the low energy requirement. While, the steam phase process has the
advantage of good use of the heat produced by steam produced, the product has a longer life.
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3.1.1.4 Reduction of nitrobenzene with iron and iron salts:

A historical variation of the nitrobenzene route is the Bechamp process, which uses iron and iron
(II) chloride for its reduction:

This process is over one hundred years old, but is still used in two Bayer aniline plants. Nowadays
the product of interest is not so much the aniline as the colored iron pigments that are formed as
by-products. In the Bechamp process the nitrobenzene is reduced in a stirred tank reactor with a
solution of iron (II) chloride. The reactor is filled with the total amount of water required for the
reaction, 20% iron, the total amount of catalyst needed and 5% to 10% of the nitrobenzene fed.
Under intense agitation the contents of the reactor are heated. After the reduction has begun, the
remaining nitrobenzene and iron are added slowly to avoid an excessive increase in temperature
and pressure. To complete the reduction the container is heated to 100 ° C for two more hours after
the addition of nitrobenzene and iron. The reaction is completed in approximately 8 or 10 hours.
The reaction mixture is neutralized with lime, then passed to a separator and the organic phase
containing the aniline is removed. The aniline is recovered by stripping with water and distillation.
The residual aniline of the remaining material is recovered in the separator before the iron oxide is
converted to fine particles, to a colored pigment. The color of the by-product can be controlled by
adding additives in the reaction medium, with the use of different types of iron and with the
appropriate calcining conditions.

3.1.1.5 Phenol Amination:

In the commercial route of phenol developed by Halcon, phenol is aminated in steam phase using
ammonium in the presence of a silica-alumina catalyst:

The reaction is moderately exothermic and reversible so that high conversion is only obtained with
the use of an excess of ammonium (molar ratio 20:1) and a low reaction temperature, which also
reduces the dissociation of ammonium. The impurities produced include diphenylamine,
triphenylamine and carbazole. It can also be inhibited with the use of an excess of ammonium. The
yield with respect to phenol and ammonium is 96% and 80% respectively.

The fresh and recirculated phenol and ammonium are separately vaporized and mixed in a fixed
bed reactor, which contains the catalyst. After the reaction at 370 °C and 1.7 MPa, the gas is cooled.
Part is condensed and the excess air is passed to a separation column, where it is recovered,
compressed and recirculated. The condensation product is passed through a drying column to
remove the water and then through another column to remove the aniline from the residual phenol
and the impurities, under vacuum conditions. The phenol containing aniline residues is
recirculated.

3.1.1.6 Comparison of previous methods:

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The comparison between the route of phenol and that of nitrobenzene for obtaining the sample of
aniline, although in both parts of benzene, for the first case four stages are needed (the passage of
a second path involves two intermediate steps) while in for the second, only two are required. The
nitrobenzene route presents a great advantage in terms of performance and low energy requirement.
On the other way, the phenol pathway has an advantage in the long life of the catalyst and the
quality of the final product. This method is preferred as long as the cost of phenol makes it
economically viable.

3.2 Particular information of each chemical route with its respective process flow diagram:

The information of each chemical route with its respective process flow diagram is disaggregated
in annexes 1,2,3 and 4 corresponding to each chemical route analyzed.

3.3 Justification of the chemical route to be used for the production of the compound
assigned chemical and Process Selection Matrix:

As a first step for the construction of the Process Selection Matrix, four large families were formed
to collect the items to be studied and the importance of each of the families for the viability of the
project was evaluated. In this order of ideas, Safety was considered as the most important factor,
since an incident in the plant can trigger not only the damage of equipment or the physical plant,
but irremediable consequences such as damage or loss of human lives and irreversible effects on
the environment; As a second factor in importance, the environment was considered, firstly by the
conscience that the chemical engineer must possess with the care and preservation of natural
resources, always trying to make the least impact after each action he takes and secondly to comply
with all the environmental standard of the place where the plant is located; Finally and due to their
similarities, the families' costs and efficiency were assigned the same importance since one is
subordinated to the other.
As a second step, it was assigned the relevance that each of the items studied had in the family to
which it belongs, evaluating what percentage it would occupy in the general qualification for the
selection of the chemical route, as shown in Table 2.

Table 2. Percentage of each parameter in their respective group

% Safety (35p) % Environment (30p) % Cost (25p) % Efficiency (10p)
100 Security aspect 50 Factor E 40 Process economics 40 Obsolescence
25 Disposal of waste 30 Value added 30 State of process
25 Use of energy 20 Complexity process 20 Integration
10 Raw material costs 10 Process efficiency
*Values in parentheses correspond to the points that the group occupies in the total rating.
** The total rating is in the range of 0 to 100 points

Once assigned the percentage of importance of each parameter within each group, through the eq.
01 was calculated the percentage that would be occupied in the global qualification of each
technology. For practical purposes, should be displayed for the Disposal of waste parameter.
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% 𝐺𝑙𝑜𝑏𝑎𝑙 𝑝𝑎𝑟𝑎𝑚𝑒𝑡𝑒𝑟 𝑟𝑎𝑡𝑖𝑛𝑔 = (𝑃𝑜𝑖𝑛𝑡𝑠 𝐺𝑟𝑜𝑢𝑝) · (% 𝐴𝑠𝑠𝑖𝑔𝑛𝑒𝑑 𝑡𝑜 𝑡ℎ𝑒 𝑝𝑎𝑟𝑎𝑚𝑒𝑡𝑒𝑟 𝑖𝑛 𝑡ℎ𝑒 𝑔𝑟𝑜𝑢𝑝) Eq. 01

Example with Disposal of waste:

% 𝐺𝑙𝑜𝑏𝑎𝑙 disposal of waste 𝑟𝑎𝑡𝑖𝑛𝑔 = (30 𝑝𝑜𝑖𝑛𝑡𝑠 ) · (0,25) = 7,5% Eq. 02

As shown in Table 3. the waste disposal occupies 7.5% of the total rating.

Table 3. Matrix of selection of process technology for the production of aniline.

Technology
Parameter % A B C D
Escale Score Escale Score Escale Score Escale Score
1 Obsolescence 4,0 9,0 0,4 8,0 0,3 2,0 0,1 5,0 0,2
2 Raw material costs 2,5 5,0 0,1 3,0 0,1 4,0 0,1 2,0 0,1
3 Complexity of process 5,0 8,0 0,4 6,0 0,3 5,0 0,3 4,0 0,2
4 Efficiency of Process 1,0 10,0 0,1 9,0 0,1 8,0 0,1 7,0 0,1
5 Integration with industry 2,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0
6 Process development status 3,0 8,0 0,2 8,0 0,2 8,0 0,2 8,0 0,2
7 Disposal of waste 7,5 7,0 0,5 7,0 0,5 9,0 0,7 4,0 0,3
8 Process economics 10,0 6,0 0,6 5,0 0,5 3,0 0,3 3,0 0,3
9 Use of energy 7,5 8,0 0,6 7,0 0,5 4,0 0,3 6,0 0,5
10 Security aspects 35,0 7,0 2,5 8,0 2,8 5,0 1,8 4,0 1,4
11 Value added 7,5 10,0 0,8 10,0 0,8 0,0 0,0 0,0 0,0
12 Factor E 15,0 6,0 0,9 6,0 0,9 7,0 1,1 10,0 1,5
Total 100 7,1 7,0 4,8 4,7
*The highlighted letters correspond to each of the technologies as follows:
A: Catalytic hydrogenation in vapor phase.
B: Catalytic hydrogenation in liquid phase.
C: Reduction of nitrobenzene with iron and iron salts.
D: Phenol Amination.
** The scale is in the range 0 to 10.
*** The "Score" was calculated with score =% parameter · scale.

Analysis by parameter:

Obsolescence:

Firstly, we started by evaluating the performance of each technology according to the product of
interest, but high and approximately equal returns were found for the four technologies. Therefore,
it was decided to look in the literature for the technologies used by the main world producers and
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it was found that nitrobenzene is used as a raw material by almost all the world producers with the
exception of Mitsui Petrochemicals Ind. (Japan), that also uses phenol and Aristech Chemical Corp.
(US) that only uses phenol [3]. Likewise, the technology Reduction of nitrobenzene with iron and
iron salts, is more than a hundred years old and is still used in two aniline plants of Bayer, but
whose products of interest are the colored pigments of iron that are formed as by-products. Based
on the above, the process of Reduction of nitrobenzene with iron and iron salts has not as its main
product the aniline, but the use of the byproducts obtained, so it is assigned a rating of (2/10); the
process of Phenol Amination, is almost in disuse, currently only takes place in Japan, so it is
assigned a rating of (5/10); The processes of Catalytic hydrogenation in vapor and liquid phase,
are frequently used at world level and have characteristics that achieve high yields, decrease in the
emission of waste (recirculation operations) as well as extension of the useful life of the catalysts
used , However, Catalytic hydrogenation in vapor phase does not use high pressures to carry out
the process, so it is safer than Catalytic hydrogenation in liquid phase and assigned a rating of
(9/10) and (8/10) respectively.

Availability and raw material costs:

It was found that Colombia (geographical area where the aniline production plant will be located)
does not produce any of the raw materials necessary for the production of aniline, so the following
shows the countries from which the supplies currently imported into the country are imported and
the price of each reagent for January 2018 in FOB US $ (Free On Board) and € / mt respectively.

Imported raw material:

Figure 1. Import of phenol [4]. Figure 2. Import of Hydrogen [4].

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Figure 3. Import of Iron chloride [4]. Figure 4. Import of nitrobenzene [4].

Figure 5. Import of ammonia [4].

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Cost of raw materials:

Figure 6. Price of phenol in the global market [5].

Figure 7. Price of hydrogen in the global market [5].

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Figure 8. Price of iron chloride in the global market [5].

Figure 9. Price of benzene in the global market [5].

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Figure 10. Price of ammonia in the global market [5].

Because all the raw materials must be imported, this will not be a valid criticism, but if there is a
difference in the prices of each and it has to:

Price phenol Amination > Price Reduction of nitrobenzene with iron and iron salts > Price Catalytic
hydrogenation in vapor phase = Catalytic hydrogenation in liquid phase.

Therefore, scores are assigned in Table 3. for this parameter.

Complexity of the process:

For the selection, each of the stages used during each route was studied, for which the processes
involved and their complexity were evaluated:

for the process of catalytic hydrogenation in liquid phase requires a packed bed reactor also does
not need a loop of recirculated gas due to low energy requirement but since it is in liquid phase is
necessary a process of separation of the product with the catalyst and a drying process to remove
the water which is also obtained in the process, the operating temperatures are of 90-200 ° C but
need high pressures around 600Kpa, on the other hand the process in vapor phase does not need
the separation product-catalyst in which the catalyst has a longer useful life but a gas recirculation
system.

On the other hand, the route of iron salts the reaction mixture is neutralized with lime and later
passes to a separator where the organic phase (aniline) is separated, then it is recovered by stripping
with water and a distillation process which it makes it a more complex and less efficient process
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than the previous ones.

Finally, the route from phenol also uses a packed bed reactor in addition to having a variety of
processes due to the amount of impurities necessary to separate with the product such as
diphenylamine, triphenylamine and carbazole, in addition to having resirculation processes,
condensation and drying, which makes it the most complex process for obtaining aniline.

Efficiency of the Process:

As far as efficiency is concerned, both, catalytic hydrogenation in vapor and liquid phase, there are
not differences in the obtained yield or the quality of the product, the only thing that can be
differentiated between these technologies is that the vapor phase process has the advantage of high
space-time performance.
As for the amination of phenol although with a high yield of 96%, it is inferior to the catalytic
hydrogenation processes and finally the technology of Reduction of nitrobenzene with iron and
iron salts has reaction times of between 8 hours and 10 hours. Therefore, the processes will be more
efficient in this order: catalytic hydrogenation in vapor phase, catalytic hydrogenation in liquid
phase, phenol amination and finally reduction of nitrobenzene with iron and iron salts.

Integration with the industry:

For all technologies, a value of 0 was assigned, because all raw materials must be imported,
regardless of the geographical area of the country where the plant is located, it is worth noting that
it is recommended that the location of the plant be made close to ports, main airports, or road
complexes with adequate infrastructure. It should also be noted that the use that could be given to
byproducts was not considered, as is the case of the process of reduction of nitrobenzene with iron
and iron salts, in which dyes of iron oxide are obtained.

Process development status:

Because the four processes are still used by the big world producers, and that these industries have
areas of research and development, it can be affirmed that these four, despite the time that is being
carried out, are still mature, with the possibility of transformations and developments.

Disposal of waste:

Regarding the processes of catalytic hydrogenation, although a part of the products is recirculated,
for the use of hydrogen added in excess, the water may contain traces of aniline, a highly toxic
substance, with serious implications for health and the environment , so it has a higher degree of
difficulty for the final disposal of its by-products.
The process of amination of phenol, does not have recirculation and usually always has a high
content of phenol in its byproducts, so its final disposal also requires strict treatment.
Finally, the process of Reduction of nitrobenzene with iron and iron salts, is the only one of the
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four that makes full use of the byproducts generated, not only dealing with commercial value to
the aniline, but also take advantage of the pigments produced by the mixture of water and iron
oxide produced.

Process economics:

For the start-up of the process, the number of units required was analyzed, which were mentioned
in the complexity parameter of the process, these same criteria being the basis for the weighting of
the routes. In this case, it was also taken into account that on the route of hydrogenation in gaseous
phase it is possible a good use of the heat of reaction in the heating of the inlet currents to the
reactor, as well as for the production of steam, which facilitates the start-up compared with the
liquid phase and because in the route of phenol and iron salts are needed a greater number of units
and process equipment.

Use of energy

The route of nitrobenzene has a great advantage in terms of performance and low energy
requirement where in the liquid phase hydrogenation has as characteristic the high space-time
performance while in the vapor phase as mentioned above a good use of the heat of the reaction,
generating steam from this. On the other hand, the phenol route has an advantage in the long life
of the catalyst and the quality of the final product but greater number of units.

Security aspects

For the analysis of safety aspects, two critical design variables were considered: temperature and
pressure. The operating conditions of each process are shown below in Table 4:

Tabla 4. Critical design variables for each process.

Process Pressure (Kpa) Temperature (ºC)
Catalytic hydrogenation in vapor phase 100 - 700 250 - 350
Catalytic hydrogenation in liquid phase 100 - 600 90 -200
Phenol Amination 1700 370
The addition of reagents should be done very
slowly, since the nature of the reaction
Reduction of nitrobenzene with iron and iron salts
generates very rapid increases in pressure
and temperature.

From Table 4. it can be evidenced that the process Reduction of nitrobenzene with iron and iron
salts, requires strict control in the addition of the reagents, in order to avoid sudden increases in
pressure and temperature; the process of Phenol Amination, operates at high pressures (P> 10 atm);
Catalytic hydrogenation in both phases has variables to which they can be given adequate control.
It should be noted that these variables, pressure and temperatures are not the only determinants in
the design of the reactor, it is also of great importance to know the corrosive nature of each
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substance to make a correct selection of the material of the pressure vessel.

Value added:

Figure 11. Price of aniline in the global market [5].

From Figure 6. It has:

1370 € 𝑚𝑡 1,37 €
𝑃𝑟𝑖𝑐𝑒 𝑝ℎ𝑒𝑛𝑜𝑙 = · = Eq. 03
𝑚𝑡 103 𝐾𝑔 𝐾𝑔

From Figure 7. It has:

0,174 € 𝑚3 2,08 €
𝑃𝑟𝑖𝑐𝑒 ℎ𝑦𝑑𝑟𝑜𝑔𝑒𝑛 = · = Eq. 04
𝑚3 0,0838 𝐾𝑔 𝐾𝑔

From Figure 8. It has:

135 € 𝑚𝑡 0,135 €
𝑃𝑟𝑖𝑐𝑒 𝑖𝑟𝑜𝑛 𝑐ℎ𝑙𝑜𝑟𝑖𝑑𝑒 = · = Eq. 05
𝑚𝑡 103 𝐾𝑔 𝐾𝑔

From Figure 9. It has:

770 € 𝑚𝑡 0,77 €
𝑃𝑟𝑖𝑐𝑒 𝑛𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 = · = Eq. 06
𝑚𝑡 103 𝐾𝑔 𝐾𝑔

From Figure 10. It has:

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266,4 € 𝑚𝑡 00,266 €
𝑃𝑟𝑖𝑐𝑒 𝑎𝑚𝑚𝑜𝑛𝑖𝑎 = · = Eq. 07
𝑚𝑡 103 𝐾𝑔 𝐾𝑔

From Figure 11. It has:

1180 € 𝑚𝑡 1,18 €
𝑃𝑟𝑖𝑐𝑒 𝐴𝑛𝑖𝑙𝑖𝑛𝑒 = · = Eq. 08
𝑚𝑡 103 𝐾𝑔 𝐾𝑔

Applying the value added equation in:

𝑉𝑎𝑙𝑜𝑟 𝐴𝑔𝑟𝑒𝑔𝑎𝑑𝑜 (𝑉. 𝐴) = (𝐼𝑛𝑔𝑟𝑒𝑠𝑜𝑠 𝑝𝑜𝑟 𝑣𝑒𝑛𝑡𝑎𝑠) − (𝐶𝑜𝑠𝑡𝑜 𝑑𝑒 𝑟𝑒𝑎𝑐𝑡𝑖𝑣𝑜𝑠) Eq. 09

Catalytic hydrogenation in vapor and liquid phase:

Taking a base of 1000 Kg nitrobenzene →

𝑅𝑒𝑎𝑙 𝑎𝑚𝑜𝑢𝑛𝑡
%𝑅𝐴𝑛𝑖𝑙𝑖𝑛𝑒 = · 100% Eq. 10
𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑎𝑚𝑜𝑢𝑛𝑡

The limit reagent is nitrobenzene.

1 𝑚𝑜𝑙𝑒𝐴𝑛𝑖𝑙𝑖𝑛𝑒 𝑚𝑜𝑙𝑒𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 103 𝑔𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 93.13 𝑔𝐴𝑛𝑖𝑙𝑖𝑛𝑒 𝐾𝑔𝐴𝑛𝑖𝑙𝑖𝑛𝑒

· 103 𝐾𝑔𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 · · · · →
1 𝑚𝑜𝑙𝑒𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 123.06 𝑔𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 𝐾𝑔𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 𝑚𝑜𝑙𝑒𝐴𝑛𝑖𝑙𝑖𝑛𝑒 103 𝑔𝐴𝑛𝑖𝑙𝑖𝑛𝑒

𝑚𝐴𝑛𝑖𝑙𝑖𝑛𝑒 = 756.78 𝐾𝑔𝐴𝑛𝑖𝑙𝑖𝑛𝑒 Eq. 11

Replacing the Eq. 11 in Eq. 10:

%𝑅𝐴𝑛𝑖𝑙𝑖𝑛𝑒
𝑅𝑒𝑎𝑙 𝑎𝑚𝑜𝑢𝑛𝑡 = · 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑎𝑚𝑜𝑢𝑛𝑡 →
100%

99%
𝑅𝑒𝑎𝑙 𝑎𝑚𝑜𝑢𝑛𝑡 = · 756.78 𝐾𝑔𝐴𝑛𝑖𝑙𝑖𝑛𝑒 = 749.21 𝐾𝑔𝐴𝑛𝑖𝑙𝑖𝑛𝑒
100%
3 𝑚𝑜𝑙𝑒𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 𝑚𝑜𝑙𝑒𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 103 𝑔𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 2.016 𝑔𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 𝐾𝑔𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛
· 103 𝐾𝑔𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 · · · · →
1 𝑚𝑜𝑙𝑒𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 123.06 𝑔𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 𝐾𝑔𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 𝑚𝑜𝑙𝑒𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 103 𝑔𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛

𝑚𝐴𝑛𝑖𝑙𝑖𝑛𝑒 = 49.146 𝐾𝑔𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 Eq. 12

Replacing Eq 11, Eq 12, Eq. 04, Eq 06 and Eq. 08 in Eq. 09:

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1,18 € 2,08 € 0,77 €

(𝑉. 𝐴) = · 749.21 𝐾𝑔𝐴𝑛𝑖𝑙𝑖𝑛𝑒 − · 49.146 𝐾𝑔𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 − · 103 𝐾𝑔𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒 →
𝐾𝑔𝐴𝑛𝑖𝑙𝑖𝑛𝑒 𝐾𝑔𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 𝐾𝑔𝑁𝑖𝑡𝑟𝑜𝑏𝑒𝑛𝑧𝑒𝑛𝑒

(𝑉. 𝐴) = 11.84 € Eq. 13

The above represents the calculation model to find the added value of each proces.

Factor E:

The highest score was assigned to Reduction of nitrobenzene with iron and iron salts, whose by-
product is marketed, so waste byproducts are minimal and therefore have a high E factor.

3.4 Equation of reaction rate for the selected process with constants as a function of
temperature:

As will be explained, the selected process was the catalytic vapor phase hydrogenation of
nitrobenzene to produce aniline. In this type of reaction, hydrogenation, a first-order dependence
on hydrogen concentration and order zero for nitrobenzene has been manifested. In the literature,
several experiments can be found in which the results confirm this trend [10,11] in the gas phase.
In the liquid phase there are also many experiments that show that the reaction has this tendency.
From the literature found [Anitron I], it is proposed that the reaction rate equation will be:

The kinetics of the reaction is of first order with respect to the partial pressure of hydrogen and
with respect to the concentration of nitrobenzene varies between 0 and 1, depending on the
concentration of catalyst. In this case, zero order kinetics has been assumed:

r = K * Pb (atm / min)

K = K0 * exp (-Ea / R * T) (min-1)

Pb = XPb * PT (atm)

Where:

Pb: partial pressure of hydrogen (atm)

PT: total pressure in a differential of reactor length (atm). It is variable with the length.
Xi: mole fraction of component i
R: constant of the ideal gases = 1.987 cal / mol * ºK
T: temperature in a differential of reactor length (ºK). It is variable with the length.
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3.5 Type of reactor for aniline production plant:

Because of the operating conditions of the reagents, the efficiency that this type of reactor
generates, the use of a fixed bed catalyst that avoids the contamination of the desired products, the
possibility of having a reflux of reagents that have not fully participated in the reaction, the capacity
of utilization of the heat generated by the reaction in the generation of steam to reduce the costs of
any other process in the plant, for this type of production a PBR packed bed reactor has been
selected.

3.6 Select and justify:

3.6.1 The capacity (annual production) of the reactor to be designed.

The capacity for the annual production of aniline in the reactor was taken based on a grade work
[anitron] which produces around 8 tons per hour of aniline. For the design of the plant, it was
decided to work at 40% of this production, on the other hand, an annual operation of 335 days per
year was selected, taking a week to maintain the process quarterly.

From this information mentioned above we have that the reactor works with a production capacity
of 3512.72 Kg / h of aniline, for an annual production of 28242.26 Tons of aniline, for this it is
necessary to enter the reactor 4680.346Kg / h of nitrobenzene and 221.208 Kg / h of hydrogen.

3.6.2(8%) Determine the operating conditions (pressure, temperature, flows,

concentrations, conversion):

Bayer Process:
Use of conventional fixed-bed reactors using a palladium catalyst on an aluminum support,
catalyst of 1.5 to 4% by weight palladium in coke with 0.1 to 2% by weight as modifier to reduce
the aromatic ring. At the pressure of 100-700 kPa a mixture of vaporized nitrobenzene and
hydrogen in a ratio of 1: 120 to 1: 200 is fed to the adiabatic reactor with an inlet temperature of
250-350 ° C. The height of the catalyst bed in the reactor is 0.1 to 1 m. The reaction products
leave the reactor without cooling at a maximum temperature of 460 ° C. Next, the heat of
reaction is used to produce high pressure steam. The production unit can be built by means of
several adiabatic reactors in series or in parallel. After cooling to 140 or 180 ° C, the outlet of the
last reactor is fed to a separation unit where again the crude aniline, the waste water and the
recirculated hydrogen are separated under pressure. The aniline is purified by distillation.
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BIBLIOGRAFÍA.

[1] Aniline. In Ullmann’s Encyclopedia of Industrial Chemistry; Wiley- VCH Verlag GmbH &
Co. KGaA: Weinheim, Germany, 2011; Vol. 3, pp 465−478.

[2]Saha, B.; De, S.; Dutta, S. Recent Advancements of Replacing Existing Aniline Production
Process With Environmentally Friendly One-Pot Process: An Overview. Crit. Rev. Environ. Sci.
Technol. 2013, 43, 84−120.

[3] Redondo, P. et al. (2007) Planta de producción de anilina. Escola tecnica superior d'enginyeria.

[4] https://www.trade.nosis.com/es

[5] https://commoprices.com

[6] Yaws, Carl L.. (2012; 2013; 2014). Yaws' Critical Property Data for Chemical Engineers and
Chemists. Knovel. Retrieved from
https://app.knovel.com/hotlink/toc/id:kpYCPDCECD/yaws-critical-property/yaws-critical-
property

[7] Yaws, Carl L.. (2010). Yaws' Thermophysical Properties of Chemicals and Hydrocarbons
(Electronic Edition). Knovel. Retrieved from
https://app.knovel.com/hotlink/toc/id:kpYTPCHE02/yaws-thermophysical-properties/yaws-
thermophysical-properties

[8] Mannan, Sam. (2005). Lees' Loss Prevention in the Process Industries, Volumes 1-3 (3rd
Edition). Elsevier. Retrieved from
https://app.knovel.com/hotlink/toc/id:kpLLPPIVE3/lees-loss-prevention/lees-loss-prevention

[9] (2008). Knovel Critical Tables (2nd Edition). Knovel. Retrieved from
https://app.knovel.com/hotlink/toc/id:kpKCTE000X/knovel-critical-tables/knovel-critical-tables

[10] Reaction Kinetics of Nitrobenzene Hydrogenation on a Palladium Catalyst Supported on

Nanodiamonds

[11] Three-Phase Nitrobenzene Hydrogenation over Supported Glass Fiber Catalysts: Reaction
Kinetics Study

[12] T. Kahl et al., “Aniline,” in Ullmann’s Encyclopedia of Industrial Chemistry, Weinheim,

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Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2000, pp. 465–478.