Maleic Anhydride is a highly versatile chemical intermediate used in the production of a multitude of products. Its largest single application is unsaturated polyester resins for use in housing, automotive and marine industries.
Maleic Anhydride is also used in motor oil additives, artificial sweeteners, flavor enhancers, paper sizing, water treatment chemicals, epoxy curing agents, hair sprays, pharmaceuticals, agricultural chemicals and co-polymers.
Maleic anhydride occurs as colourless or white crystalline flakes with strong acrid (pungent) odour. MA is toxic and an irritant to the skin and mucous membranes leading to burning and ulceration. Care must be taken to avoid inhalation.
CAS NO.: 108-31-6
EINECS NO.: 203-571-6
Mol Wt.: 98.06
H.S. Code: 2917.14
Synonyms: cis-Butenedioic acid anhydride; Toxilic anhydride; 2,5-dihydro-2,5-dioxofuran; 2,5-furandione; 2,5-Furanedione; Maleic Acid Anhydride; Maleic anhydride;
Table 1: Physical & Chemical Properties
The main outlet for maleic anhydride (MA) is in the manufacture of unsaturated polyester resins (UPR), which are used in a wide range of applications such as pleasure boats, bathroom fixtures, automobiles, tanks and pipes. The second most important use for MA is the production of 1,4-butanediol (BDO), tetrahydrofuran (THF) and gamma-butyrolactone. Table 2 summarises some of the major applications areas of MAN.
Table 2: Applications of MAN
Commercially, maleic anhydride is produced by the catalytic oxidation of a hydrocarbon (benzene or butane), at 350°C-420°C and of 7-10 kg/cm2, using air/oxygen as the oxidising agent. Some modern processes use a synthesis pressure of 0.5 - 1.5 kg/cm2. The catalyst generally is V2O5 or V2O5 - MnO2, coated on a base of A12O3 or Al2O3-SiO2. The exothermic heat of the reaction is removed by circulating molten salt or by generating steam in the shell side of the reactor. In the process using benzene as feedstock, vaporised benzene is mixed with hot air and passed through a tubular reactor. The effluent maleic anhydride gas is, partially, condensed. The gas is, further, scrubbed with water. Pure maleic anhydride is produced through a series of thin film evaporators, dehydrator and a distillation column.
Manufacturing process in India
Benzene or butane is used as raw material for making MAN. The manufacturing process of MAN using benzene is divided into two steps — reaction step and recovery step.
Around 1.2 tonnes benzene is required to make a tonne of MAN.
A typical process using benzene as feedstock involves passing of a pre-heated vapour mixture of air and benzene over a catalyst in a reactor. Generally, the reactor consists of a multi-tube fixed-bed reactor with relatively small tubes with a diameter of around 2 cm. The reaction is highly exothermic and a molten salt mixture cools the reactor. The reaction occurs at 350°C at a pressure level that is marginally higher than the atmospheric pressure. The effluent is then cooled to 150°C - 160°C, in order to prevent the condensation of MAN and water.
Partial condensation is used to remove 40-60 per cent of MAN as liquid from the gas stream. The partial condenser cools the gas to the melting point of MAN at around 55°C. The separation temperature for water in the gases has to be maintained below dew-point, to prevent MAN from hydrating to form maleic acid. (The formation of maleic acid limits the recovery of MAN in the partial condenser.) The remaining MAN is converted from the maleic acid in the gas. (A solution of maleic acid and water could contain up to 50 per cent maleic acid.) MAN is recovered from the acid and water solution by drying the solution and then dehydrating the maleic acid. The crude MAN formed in the recovery stage is then purified by distillation to produce a 99.5 per cent pure product. However, maleic acid has to be dehydrated quickly, as there is a danger of it getting isomerised to form fumaric acid.
The catalyst for the reaction comprises vanadium pentoxide (V2O5), molybdenum trioxide (MoO3), and sodium oxide (Na2O). V2O5 and MoO3 are used in the ratio of 2:1. Other elements such as phosphorous, tin, boron and alkaline earth metals are added to the vanadium catalyst.
Domestic producer, Thirumalai Chemicals uses benzene to make MAN. (Mysore Petrochemicals recovers MAN from phthalic waste.) Alusuisse (Italy) and Scientific Design (USA) are the two licensors of MAN technology. Both licensors have technologies to manufacture MAN from feedstock - benzene or butane. MAN is produced in the form of flakes, briquettes, or molten. MAN produced in the domestic market is colourless with good quality and minimum maleic acid content, thereby ensuring low corrosiveness.
Developments in process
Scientific Design has developed chloride-free catalysts for MA production in fixed bed reactors. The catalysts are being toll manufactured by Lonza.
High growth rates for the derivative BDO have driven butane-to-BDO integrated technologies, with projects being developed by BP and Lurgi, Huntsman and Kvaerner, and BASF and Kvaerner.
BOC Gases and Mitsubishi Chemical have developed a new technology, Petrox, which has been operated on a large-scale pilot plant in Japan. The process uses a selective hydrocarbon separation system to recover and recycle unreacted butane and allows MA to be produced at low butane conversion to maximise selectivity and yield. BOC claims reductions of 10% in capital costs and 20% in raw material costs.
Major producers in India
Mysore Petrochemicals Ltd. was the only manufacturer of MAN in India with capacity of 5,400 tpa at Taloja in Maharashtra. The MAN plant of Mysore Petrochemicals was acquired by IG Petrochemiclas Ltd. since 1st April 2017. Thirumalai ChemicalsLtd. makes MAN through its subsidiary Optimistic Organic Sdn Bhd. (OOSD) in Malaysia. The plant of OOSD in Malasia has capacity of 40,000 tpa.
Table 3: Production of MAN in India
Source: Ministry of Chemicals & Petrochemicals
Huge quantities of MAN are imported into the country. Table 4 provides the data on imports of MAN into India. Imports have grown from around 38,000 tons in 2010-11 valued at Rs. 25 crores to 52.62 thousand tons in 2017-18 valued at Rs. 35 crores. The unit CIF value went up from Rs. 65 per kg in 2010-11 to Rs. 108 per kg in 2013-14 but declined thereafter to low of Rs. 66 per kg in 2015-16 to rise again in 2017-18 to high of Rs. 85 per kg.
Table 4: Imports of MAN into India Quantity in Tons; Value in Rs. Lakhs; Unit Value in Rs./Kg
Table 5 provides sourcewise imports of MAN during last two years
Imports are mainly sourced from Malaysia, Korea, Taiwan, Indonesia and China. Imports from these countries constitute 98% of the total imports. (Table 6)
Table 6: Major suppliers of MAN into India
Consumption Pattern & Demand
Consumption of MAN in India has grown from nearly 41,000 tons in 2010-11 to 56,173 tons in 2017-18 registering CARG of 4.7% during this period.
Table 7: Consumption Trend of MAN in India
Around 44 percent of the total consumption of MAN is in the manufacture of unsaturated polyester resins, followed by 18 percent in surface coatings and alkyd resins; 10 percent in plasticizers, 6 percent in lube additives, 12 percent in food acids; 5 percent in agrochemicals and balance 5 percent in other miscellaneous applications.
The total demand for MAN in 2017-18 is estimated at 56,000 tons. The MAN demand in the next five years is expected to rise to 71,600-tons by 2022-23 at CARG of 5 percent.
Table 8: Approx. Pattern of consumption of MAN
The unsaturated polyester resins (UPR) market in India is likely to post good growth in the future. due to anticipated good potential for its growth from the construction, automotive and marine sectors.
The markets for the value added products like Food Acids, Fumaric Acid, Phthalate Esters etc in the past had been restricted to some extent due to restricted availability, however, as they are quite remunerative, these are expected to post higher growth in coming years. Thirumalai Chemicals’ JV company in Malaysia TCL Industries (Malaysia )SDN BHD is reported to be investing in the downstream MAN derivatives in the near future.
With current capacity of MAN in India at only 5,400-tons, and Thirumalai Chemicals catering to around 45% of the total current demand, there is huge scope for putting up another unit for making MAN.
The maleic anhydride market was estimated at USD 2,4 bn (in terms of revenue) and 17.92 lakh tons (in terms of volume) in 2017. The market is projected to reach USD 3.2 bn and 21.50 lakh tons by 2023, at an estimated CAGR of 5.96% and 3.69%, respectively, during the forecast period, 2018-2023. Copolymers based on Maleic anhydride enable the use of more sustainable raw materials, binding wood fibers into plastic, corrosion inhibitors, and protective coatings for wire and water repellants in screens. Through conversion to fumaric and malic acids, maleic anhydride is a vital component of gelling agents, flavor enhancers, and food preservatives.
Unsaturated Polyester Resin is expected to dominate the Market
The increasing global demand for unsaturated polyester resins (UPR) in the lubricant & automotive industry is likely to have a positive impact in the market. The market is driven primarily by the high demand of the polyester resin industry, and the increase of production capacity in China. Over half of the global maleic anhydride produced is used to manufacture unsaturated polyester resins, which in turn, are used in the production of sheet molding compounds, bulk molding compounds and fiberglass reinforced plastics that are used in a diverse range of consumer products, including boats, automobiles, buildings, piping, and electrical goods.
Asia-Pacific to Lead the Market
Asia-Pacific is the largest market for maleic anhydride. The second largest market is Europe, followed closely by North America. The growing automotive and construction industries in Asia-Pacific is anticipated to drive the demand for reinforced glasses and polymers in the region, which is expected to drive the demand for maleic acid in Asia-Pacific. This region is also expected to be the fastest-growing region, during the forecast period.
The maleic anhydride market is classified on the basis of raw material into – n-butane and benzene. Maleic anhydride is produced by the oxidation of N-Butane or Benzene in the presence of specific catalyst. The maleic anhydride market is dominated by n-butane because of its low production cost, and environmentally friendly nature. Earlier benzene was the primary feedstock used to produce maleic anhydride using oxidation process.
However, the increasing government regulations, high production cost, complex operation, and awareness about toxicity of benzene, manufacturers preferred n-butane for the production of maleic anhydride. N-Butane accounts for a share of about 90% of the maleic anhydride market, by value, in 2017. It is expected to dominate the market in the next five years.
The major factor restraining the growth of the maleic anhydride market is increasing use of green chemicals as an alternative for maleic anhydride. Maleic anhydride is petroleum derived organic chemical intermediate, which is both, costly and environmentally unfriendly. Hence, the use of bio based succinic acid as an alternative for the maleic anhydride is increasing in the industries. Additionally, the increasing regulations for maleic anhydride at federal state as well as local level are responsible for the reducing global market share of maleic anhydride.
Major Global Palyers: Huntsman International LLC. (U.S.), Changzhou Yabang Chemical Co. Ltd. (China), Zibo Qixiang Tengda Chemical (China), Ningbo Jiangning Chemical (China), Lanxess AG (U.S.), Polynt (Italy), Thirumalai Chemicals Ltd. (India), Ashland Inc. (U.S.), Flint Hills Resources (U.S.), Nippon Shokubai Co., Ltd. (Japan), Mitsubishi Chemical Corporation (Japan), Bartek Ingredients Inc. (Japan), Bluestar Harbin Petrochemical Corp (China), and others.