Special Report PRODUCT FOCUS
Aniline: A techno-commercial profile
A
niline (phenylamine or aminobenzene) is an organic compound with the formula C6H5NH2. Consisting of a phenyl group attached to an amino group, aniline is the prototypical aromatic amine. Although a precursor of many industrial chemicals, its main use is in the manufacture of methylene diphenyl diisocyanate (MDI) – a precursor to polyurethanes. Like most volatile amines, aniline possesses the somewhat unpleasant odour of rotten fish. It ignites readily, burning with a smoky flame characteristic of aromatic compounds. Aniline is colourless, but slowly oxidises and resinifies in air, giving a red-brown tint to aged samples. Table 1 Physical properties Parameter Physical state Melting point Boiling point Specific gravity Solubility in water pH Vapour density Flash point Stability
PANKAJ DUTIA
[email protected] H2SO4 mixture; and
Hydrogenation of nitrobenzene with metal catalysts (Raney Ni or Pt/Pd on carbon).
The chemistry of nitrobenzene production is relatively simple and mature. It proceeds by the formation of the nitronium ion, NO2+ which attacks the aromatic ring of benzene to give nitrobenzene. The reaction is exothermic, releasing about 80-kcal/mol.
Value Clear oily liquid -6°C 184°C 1.21-1.22 0.3 g/l at 20°C 8.1 3.2 70°C Stable under ordinary conditions. Air and light sensitive
Chemical synthesis Aniline is mainly produced in industry in two steps from benzene. First, benzene is nitrated using a concentrated mixture of nitric acid and sulphuric acid at 50-60°C, which gives nitrobenzene. In the second step, the nitrobenzene is hydrogenated, typically at 200-300°C in presence of various metal catalysts. Chemical Weekly January 24, 2012
Originally, the reduction was effected with a mixture of ferrous chloride and iron metal via the Bechamp reduction. As an alternative, aniline is also prepared from phenol and ammonia, the phenol being derived from the cumene process.
Nitration The two commercial nitration processes – isothermal and adiabatic – are different only in the nitration section, where the adiabatic process integrates nitration with sulphuric acid concentration, thus using the heat of nitration to reconcentrate the spent sulphuric acid. This is achieved by creating a large volume of sulphuric acid through the nitrators, adsorbing the heat of nitration without undue temperature rise. In the areas of nitrobenzene purification, effluent treatment and fume control, the two processes employ equivalent design concepts. HNO3 + 2H2SO4
NO2+ + H3O+ + 2HSO4-
NO2
+ NO2+
+ H+ Nitrobenzene
Nitrobenzene reduction The highly exothermic catalytic hydrogenation of nitrobenC6H5NH2 + 2 H2O zene is carried out commercially in C6H5NO2 + 3H2 the presence of excess hydrogen in both the vapour phase and in the liquid Manufacturing technology Current manufacturing practice of phase. Vapour phase processes may aniline production employs a three-step employ either fixed-bed or fluidizedbed reactors. Copper or palladium on process technology: activated carbon or an oxidic support,
Production of nitric acid;
Nitration of benzene with HNO3/ in combination with other metals (lead, C6H6 + NO2+
C6H5NO2
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Special Report vanadium, phosphorous, chromium) as modifiers/promoters has been shown to be an effective catalyst for vapourphase hydrogenation, achieving high activity and selectivity. NO2
NH2 + 2H2O
+ 3H2 Aniline
Yields of both nitrobenzene and aniline are impressive (>98%). However, dilution of sulphuric acid caused by water produced from the nitration step is an inhibiting factor of nitration reaction. Disposal of this large quantity of dilute acid poses environmental problems. Therefore, the dilute acid is reconcentrated and recycled, thereby making the nitration step energy intensive. Treatment of vent NOx gas and phenolic waste water are added cost factors to the current technology. Ammonolysis of phenol Another route, by SABIC/Sud-Chemie partnership Scientific Design, is the vapour phase ammonolysis of phenol using excess ammonia and a silicaalumina catalyst. But this is now only used by Mitsui. A fixed bed reactor is suitable, as the reaction exotherm is moderate. Use of excess ammonia (mole ratio 20:1) pushes the reversible reaction to the right and also inhibits formation of by-products diphenylamine, triphenylamine and carbazole. OH + NH3
NH2 + H2O
Alternative routes Despite growth in aniline demand, there has been relatively limited process improvement. Besides, any pro198
cess improvement has been centred on reduction in energy use and waste stream production. The most promising alternate route is the catalytic reaction between benzene and ammonia in a single vessel. Although several researchers have studied this one-pot synthetic approach in the presence of metal/metal oxide catalysts, maximum yield of aniline has been reported to be only 14%. One of the limiting factors of this reaction is the formation of hydrogen gas (H2), which pushes the equilibrium towards the backward direction. Technology licensors Kellogg, Brown & Root (KBR) announced a licensing agreement in December 2002 with DuPont Intellectual Assets Business (IAB) designed to offer DuPont’s nitration/hydrogenation process technology for new aniline plants and retrofits. Table 2 Trend in production of aniline [Tonnes] Year Production 2005-06 48,110 2006-07 47,370 2007-08 44,980 2008-09 29,670 2009-10 39,386 2010-11 41,729
The key benefits of this technology include high yields, constant high purity product, elimination of the sulphuric acid concentration system, a simple mononitrobenzene (MNB) hydrogenation system, low environmental emissions and high on-stream time. High yields This process has demonstrated its capability to consistently achieve 98% efficiency of raw materials utilization. Constant high purity product Aniline produced from this technology maintains a constant product purity without having a drop-off in product quality at the end-of-run catalyst cycles, typical in some hydrogenation technologies. The aniline product from this process is the highest quality in the industry, with less than 0.1-ppm (by weight) of MNB and less than 200-ppm of total organic impurities. Sulphuric acid concentration system eliminated The unique dehydrating nitration (DHN) technology accomplishes the nitration of benzene and the sulphuric acid concentration in a single step, thus eliminating the capital and energy intensive sulphuric acid concentration system typical of conventional isothermal nitration technology. Compared with the conventional
Table 3 Company-wise production of aniline [Quantity in Tonnes; Value in Rs. Mn] Company Years Production Sales Sales quantity value Gujarat Narmada Valley 2008-09 27,077 27,090 1,865 Fertilisers Ltd. 2009-10 33,848 33,825 2,167 2010-11 39,896 2009-10 5,538 5,231 309 Hindustan Organic Chemicals Ltd. 2010-11 1,833 1,826 135 Chemical Weekly January 24, 2012
Special Report Low environmental emissions Environmental Unit CIF value [Rs. per Kg] controls and pollution prevention sys61 tems are a critical 61 part of the MNB/ 58 aniline plant design. 65 The process includes waste minimiza52 tion features, which 66 reduce the total quantity of process wastewater. Furthermore, the quantity of biologically toxic aqueous discharge is reduced to a practical minimum. The process is designed to meet and exceed the most stringent environmental regulations.
Table 4 Imports of aniline into India Years 2005-06 2006-07 2007-08 2008-09 2009-10 2010-11
Quantity (Tonnes) 5,774 13,231 18,736 18,798 19,066 37,644
CIF Value (Rs. Mn) 351 801 1,095 1,231 990 2,490
Source: Chemical Weekly Database
adiabatic nitration technology, the DHN technology has comparable energy efficiency and has less processing equipment, resulting in a lower capital cost. Simple MNB hydrogenation system The liquid phase MNB hydrogenation catalyst system is very simple, efficient, compact and provides good catalyst life. This catalyst system avoids the complexity of a catalyst regeneration system typical of vapour phase technologies. The high activity catalyst system achieves essentially quantitative yields with minimal by-product formation. Single-pass, high conversion of hydrogen eliminates the need for a recycle hydrogen system.
High on-stream time Since the DHN technology has avoided a sulphuric acid concentration step that is prone to maintenance difficulties, the on-stream time of the MNB/ aniline plant is improved.
Gujarat Narmada Valley Fertilisers Ltd. (GNFC) (Bharuch, Gujarat) is the largest producer, with a capacity of 35,000-tpa;
Hindustan Organic Chemicals Ltd. (HOC) (Rasayani, Maharashtra) with 12,000-tpa capacity; and
Anirox Pigments Ltd. (Kolkata, West Bengal) with capacity of 4,000-tpa. Anirox Pigments uses most of its production for captive use, while HOC’s plant of is currently not operational. This leaves just one producer to meet the merchant requirements of the chemical. The overall capacity utilisation is only 82%, although the GNFC plant’s operating rate was 114% in 2010-11. Total production of aniline in 2005-06 was 48,110-tonnes, which has declined to 41,729-tonnes in 2010-11. International trade Since local production is insufficient to meet the requirements of the domestic industry, significant volumes of aniline are imported into the country.
Belgium
15,793
952
UK
12,250
744
USA
6,350
393
Portugal
1,466
92
Uses of aniline The largest application of aniline is for the preparation of methylene diphenyl diisocyanate (MDI). The majority of aniline serves this market. Other uses include:
Rubber processing chemicals (9%), such as p-phenylenediamine and diphenylamine (which are antioxidants);
Dyes & pigments (2%), including as precursor to indigo, the blue of blue jeans;
Pharmaceuticals, such as paracetamol; and
Herbicides (2%).
Germany
1,098
74
Czech
628
47
Indian scenario
Very small quantities of aniline are exported from India. Exports have declined from around 4,403-tonnes in 2006-07 to only around 683-tonnes in 2010-11.
Japan
58
3
Others
3,001
185
Total
37,644
2,490
Production In India, there are three producers with capacity to manufacture aniline, with a combined capacity of 51,000tpa.
Consumption Consumption of aniline has increased from around 51,000-tonnes in 2005-06 to 78,690-tonnes in 2010-11, registering a CAGR of 9%.
Table 5 Source of imports of aniline into India [2010-11] Country
Quantity CIF Value (Tonnes) (Rs. Mn)
Source: Chemical Weekly Database Chemical Weekly January 24, 2012
Imports have increased from 5,774 in 2005-06 to 37,644 tonnes in 201011 and now constitute 48% of total consumption. Majority of the imports (92%) is coming from three countries: Belgium (42%); UK (33%) and USA (17%).
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Year 2005-06 2006-07 2007-08 2008-09 2009-10 2010-11
Table 6 Exports of aniline from India Quantity CIF Value Unit FOB value (Tonnes) (Rs. Mn) [Rs. per Kg] 2,908 205 70.50 4,403 272 61.78 2,295 154 67.10 963 119 123.57 249 29 116.47 683 54 79.06
Unlike the consumption pattern of aniline across the world where majority of it is used in manufacture of MDI, in India aniline is mainly used in making dyes & dyes intermediates, pigments, chemical derivatives and rubber chemicals. Approximately 55% is consumed by the colorants industry comprising dyes, dyes intermediates & pigments, followed by pharmaceuticals (18%), derivatives (14%) and rubber chemicals (10%). In the dyes industry, aniline is used for manufacture of a number of acid, disperse, reactive and direct dyes, besides naphthols and optical brighteners. Pigments and intermediates like vinyl
sulphone, acetoacetanilide, sulphanilic acid etc. also require aniline.
Important chemical derivatives of aniline include ortho& para-chloroaniline, ortho- & para-nitroaniline, ortho-chloropara-nitroaniline, dimethylaniline etc.
In the pharma industry, aniline is used in making paracetamol, sulphamethoxazole, analgin, diclofenac sodium, trimethoprim, oxyphenbutazone, amongst other drugs. Future demand The dyes & pigments industry is expected to grow at around 6% per annum, while pharmaceuticals is expected to grow at 12% per annum. Overall demand for aniline is expected to increase at around 8% per annum. At this rate, demand is expected to reach to around 115,000-tonnes by 2015-16.
Others 3%
The current production capacity is only 51,000-tpa. With HOC not operational, effective capacity is only around 40,000-tpa. With no new capacities announced, growth in demand will have to be met through increased imports. Dependance on imports, which is around 48% now is likely to go upto 65% by 2015-16. Global scenario World consumption of aniline is estimated at 5.2-mt in 2010, according to SRI International. MDI has been the driving force behind world growth in aniline demand since 1982, and now accounts for over 75% of world consumption. MDI is consumed in PU foam – both rigid and flexible. Most rigid PU foam is used in construction and appliances, while flexible PU foam is used primarily in furniture and transportation. As a result, consumption of nitrobenzene/aniline/MDI largely follows patterns of the leading world economies and depends heavily on construction/ India
Central/Eastern Europe
Rubber chem 10%
Central/South America Other
Rep. of Korea
Western Europe
Derivatives 14% Japan
Pharma 18% Colorants 55%
United States
China Fig. 1: Aniline consumption pattern in India
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Fig. 2: World Consumption of aniline by region/country Chemical Weekly January 24, 2012
Special Report Table 7 Consumption of aniline in India Year 2005-06 2006-07 2007-08 2008-09 2009-10 2010-11
Production 48,110 47,370 44,980 29,670 39,386 41,729
Imports 5,774 13,231 18,736 18,798 19,066 37,644
Exports 2,908 4,403 2,295 963 249 683
[Tonnes] Consumption 50,976 56,198 61,483 47,505 58,203 78,690
Table 8 Major aniline producers in China Company Bayer MaterialScience Trading (Shanghai) Co Ltd. Sinopec Nanjing Chemical Industry Co. Shanghai Lianheng Isocyanate Co Ltd. Jilin Connell Chemical Industry Co Ltd. Shanxi Tianji Coal Chemical Industry Co Ltd. SP Chemicals (Taixing) Co Ltd. PetroChina Lanzhou Petrochemical Co Ltd. Shandong Jinling Chemical Co Ltd. Zhangqiu Riyue Chemical Co Ltd. Tianxiang Chemical Factory of Shandong Haihua Co Ltd. Jiangsu Leasty Chemical Co Ltd. Hebei Jiheng Group Co Ltd. Chongqing Changfeng Chemical Industry Co Ltd. Jiangsu Ruxiang Chemical Co Ltd. Jiangsu Meilan Group Jiangsu Dahe Chlor-Alkali Chemical Co Ltd. Jiangsu Anpon Electrochemical Co Ltd. Henan Kaipu Chemical Co Ltd. Jintian Enterprisese (Nanjing) Co Ltd. Yantai Wanhua Polyurethanes Co Ltd. Others Total Source: China Chemical Reporter
remodelling activity (residential & non-residential), automotive production and original equipment manufacture. MDI growth has also been driven by ‘green’ initiatives, the desire for sustainability and to lower CO2 emissions. Since most MDI producers are captive in aniline and its precursor Chemical Weekly January 24, 2012
Capacity [ktpa] 280 260 160 150 135 135 70 60 50 50 50 50 45 30 30 30 30 30 20 20 60 1,745
nitrobenzene, typically in integrated units, nearly all MDI expansions result in increased production and consumption of nitrobenzene/aniline. Other large applications of aniline include its use as a chemical intermediate for rubber-processing chemicals, dyes and pigments. World consumption of aniline grew at a CAGR of 3% during 2006-2010, the result of a growing global economy during 2001-2008, declines during the economic recession in 2009 and the recovery in 2010, and growth due to increased MDI capacity. Strong Asian demand for all applications of MDI boosted demand during 2006-2010. World consumption of aniline is forecast to grow at a CAGR of 3.8% during 2010-2015. Continuing rapid demand growth in some regions, particularly in China, other Asia and Europe, mainly the result of continued expansion of integrated nitrobenzene/aniline/ MDI units, will balance out moderate growth in markets such as the Americas. Annual consumption will rise by 10.5% in Asia-Pacific, 6.5% in Asia/ Middle East, 5.6% in Western Europe, 5.1% in the US, and 1.5% in Japan. Other regions will grow by 3-4%/year. The aniline industry is a concentrated one, with most producers integrated into MDI production. BASF, Huntsman, Bayer and DuPont are the four dominant players, with about 17%, 12%, 12% and 10% of the world’s capacity, respectively; only DuPont is not an MDI producer. BASF, Huntsman and Bayer each have plants in several world regions. China has around 28% of the global capacity for aniline – around 1.735mtpa [2010]. 201
