The term “oxo-alcohols” is used to describe alcohols obtained from the “oxo process,” which involves reaction of olefins and synthesis gas (a mixture of hydrogen & carbon monoxide), to produce aldehydes, which are converted to alcohols. Since a major application of oxo-alcohols is for making plasticisers, they are also referred to as plasticiser alcohols. The list includes:
• n-Butanol (NBA) • Isobutanol(IBA) • 2-Ethylhexanol (2-EHA) • 2-Propylheptanol (2-PH) • Isononyl alcohol (INA) • Isodecyl alcohol (IDA).
In addition, several higher alcohols are also produced from different olefins using the oxo process.
IBA, a low boiling alcohol,is a clear and colourless liquid with a sweet musty odour. It is miscible with light mineral oils and partly miscible with heavy mineral oils.
IBA is similar in property to NBA and may be used as a supplement or replacement for IBA in some applications. It is useful in organic synthesis, as a chemical intermediate and as a solvent in coating applications. As a relatively slow evaporating latent solvent in lacquers and ambient-cured enamels, IBA is effective in reducing the viscosities of many formulations, while simultaneously promoting flow and retarding blush. IBA finds its application in the manufacture of plasticisers, amino resins, isobutyl acetate, and as a solvent.
The precursor of IBA in the oxo process is isobutyraldehyde, which is used to produce other commercially important chemicals like neopentyl glycol (NPG). IBA is a flammable liquid with a flash point of about 28°C. Under EU classification, it is classified as flammable and irritant.In March 2009, the Canadian government announced a ban on IBA use in cosmetics.
It is shipped under hazard class 3 (flammable liquid) and UN packing group III.
Typical specifications of IBA
Oxo-alcohols, in general, are produced by the oxo-process, more formally known as hydroformylation. This is the reaction of an olefin with mixture of carbon monoxide (CO) and hydrogen(H2) (synthesis gas or syngas) to give an aldehyde. Subsequent hydrogenation of the aldehydes leads to oxo-alcohols.
The oxo-process is used to produce different alcohols via the respective aldehydes using different olefin feedstock. Although there are several versions of processes to produce aldehydes from olefins, using different catalysts, the hydrogenation steps to produce oxo-alcohols from aldehydes, are similar for most manufacturers.
Propylene is used as raw material to produce NBA, 2-EHA and IBA by reaction with synthesis gas. The first step – hydroformylation to convert propylene to a mixture of aldehydes – is common to all three oxo-alcohols. Further processing to obtain the individual alcohols, differs slightly.
During hydroformylation step, a mixture of two aldehydes – n-butyraldehyde&isobutyraldehyde – is obtained. This mixture is either separated initially, and the individual aldehydes isomers hydrogenated to the respective alcohols; or the mixture of isomeric aldehydes is hydrogenated directly and the NBA and IBA product mix separated by distillation.
The technology can also be used to produce higher alcohols such as C11 to C14 from olefins produced from Fischer-Tropsch synthesis.
There are several other commercial processes for manufacture of NBA, which have been used historically or are still in use in some geographies, due to local availability of the required raw materials.
NBA has been produced from ethanol by successive dehydrogenation to acetaldehyde; condensation to crotonaldehyde and hydrogenation. Alternatively, the intermediate acetaldehyde for this process was obtained from ethylene by the Wacker process.
Zeigler-Natta chain growth reaction has also been employed using ethylene as a raw material to produce NBA. Sasol uses a Ziegler process, which dimerises ethylene, followed by oxidation and hydrolysis to give NBA.
In the late 1990s, BASF patented the butadiene route to NBA and butyraldehyde. Butadiene is catalytically converted into a mixture of linear and branched butenyl ethers. These are isomerised to linear butenyl ether, and subsequently converted into linear butyraland finally hydrogenated to NBA. Alternatively, the intermediate acetal can be hydrolysed to n-butyraldehyde. High overall efficiencies to NBA and n-butyraldehyde have been claimed.
The feedstocks used for the production of bio-NBA are the same as those used for the production of bio-ethanol – sugar beets, sugarcane, corn, wheat, cassava etc. Non-food items like agricultural waste and grasses can also be used. Also, it is reported that existing bio-ethanol plants can be cost-effectively retrofitted for bio-NBA production.
The earliest commercial process to produce bio-NBA employs fermentation of molasses or corn products with Clostridium acetobutylicum. Acetone and methanol are obtained as co-products (the process is termed as acetone, butanol, ethanol or ABE fermentation). This process has been used on industrial scale (multi-tonnes per day per facility) in the USA in early 20th century, in South Africa until the early 1980s, in Russia until the late 1980s, and is currently performed industrially in China.
IBA may be used as a supplement or replacement for NBA in many applications. Although, historically, IBA was an undesired by-product of the oxo process, it has replaced NBA in some applications where the branched alcohol appears to have preferred properties and structure. However, IBA is the least-valued derivative of isobutyraldehyde, the oxo process intermediate, after neopentyl glycol, methyl isoamyl ketone and other condensation products. The price of IBA vis-à-vis NBA decides the use of IBA as a replacement of NBA in many applications, especially as a solvent.
IBA is used to produce a wide variety of derivatives. It is converted to various esters, like isobutyl acetate, diisobutyl phthalate, isobutyl acrylate, isobutyl methacrylate, etc. which are useful in various applications. Isobutyl acetate is used in the production of lacquers and coatings, as well as a flavouring agent in foods. Diisobutyl phthalate (DIBP) is used as a plasticiser in plastics, rubbers and dispersions. Isobutyl acrylate and methacrylate are used as monomers for the manufacture of various acrylic polymers. It is used for the manufacture of zinc dialkyldithiophosphate (ZDPP), which are used as lube oil additives. IBA also finds use in the manufacture of isobutylamines and amino resins.
The principal industrial application of IBA is as a direct solvent replacement for NBA. IBA is used a solvent for paints & coatings, inks and automotive polishes. It is a component of paint and varnish removers and automotive paint cleaners. In paints & coatings, IBA, as a slow evaporating solvent, reduces viscosity, improves brushing and retards formation of oil residues (blush) on painted surfaces.
Andhra Petrochemicals Ltd. (APL) is the only producer of oxo-alcohols in India and accounts for just 32% of the market. It produces NBA, IBA and 2-EHA. As on today, the company has 73,000-tpa of capacity at its facility in Visakhapatnam, in the state of Andhra Pradesh. The facility began its operations in 1994 with an initial capacity of 30,000-tpa. The plant uses oxo process technology provided by Davy Process Technology. Over the years, the company enhanced its production capacity to 73,000-tpa. APL invested about $65-mn (Rs. 320-crore) in the expansion. Table 2 below provides details on Production, Imports and Consumption of IBA in India (in Tons)
Table 2: Production, Imports and Consumption of IBA in India (in Tons)
The production of IBA has been ranging between 1000 to 2,700 tons during the period of last eight years. Most of the requirement of IBA is being met through imports, which constitute 85 to 90% of the total consumption.
The market for IBA is driven by use for making plasticisers and solvent use. The key application is in the manufacture of di-isobutyl phthalate (DIBP). DIBP is used as a plasticiser in cables, shoe soles, PVA, etc. Other applications include solvent usage in pharma, paints & inks, and as a lube additive.
As regards pattern of consumption is concerned, 70% of the total consumption is consumed by Plasticisers segment, followed by solvents 10%, pharma segment 5%, Lube additives and Iosbutyl acetate 4% each and dyes, amino resins and others consuming the balance 7%. Table 3 provides data on consumption pattern of IBA in India.
Table 3: IBA demand by applications, 2017-18 [Tonnes]
Future demand for IBA
Demand for IBA is expected to grow by 5% per annum from 2018-19 to 2022-23 and thereafter at 7% per annum to reach about 72-kt by 2026-27. Demand will be driven by above average growth for making plasticisers and for making esters, but will be dragged down by solvent usage, which will be at a more moderate 5% for the five-year periods.
Plasticiser use will continue to account for a bulk of major demand – about 74% – by 2022-23, from about 70% in 2017-18.
Global Isobutanol Market: Snapshot
Isobutanol is a primary alcohol and an organic compound with a molecular formula of (CH3)2CHCH2OH. It is a colourless, flammable liquid used predominantly as solvent and chemical intermediate to manufacture wide range of chemical formulations. Although it has limited miscibility in water, it is easily soluble in a wide range of regular solvents such as ketones, alcohols, ether, gycols, aromatic hydrocarbons, and aldehydes. Isobutanol also performs a number of functionalities, including playing the role of extractant, additive, humectant, dehydrating agent, and starting material.
According to Transperancy Market Research Agency, the global market for isobutanol has witnessed a steady pace of expansion in the past few years owing to high demand from a number of industries. The market continues to expand at a steady pace and is expected to exhibit a healthy CAGR of 5.2% over the period between 2017 and 2025.
Increased Demand for Bio-based Products to Compel Isobutanol Manufacturers to Turn to Renewable Feedstock
On the basis of type, isobutanol is classified as synthetic isobutanol and bio-based isobutanol. Synthetic isobutanol is majorly produced by the carbonylation of propylene. The industry uses two methods to produced synthetic isobutanol namely - hydroformylation and Reppe carbonylation. Among these two hydroformylation is more common. However, due to environmental concerns, isobutanol manufacturers are shifting their focus on producing bio-based isobutanol, which is manufactured with the use of renewable feedstocks. Bio-based isobutanol is a cost effective alternative to isobutanol derived from fossil feedstock. Bio-based isobutanol serves as an excellent bio-based fuels which helps to lower carbon alternative. As a fuel, it can be blended with gasoline in higher concentration than ethanol without compromising compatibility and performance. On the basis of end user segment isobutanol is segmented into paints and coatings, oil and gas, pharmaceuticals, chemicals, and textiles. Isobutanol in the form of colorless, oily liquid is used as an industrial solvent that can be used in paints and coatings. When used in paints, isobutanol contributes in reducing viscosity and removes the brush flow of the end product. Isobutanol also helps to reduce the formation of oil residue. The paints and coatings industry is likely to remain one of the key consumers of isobutanol in the next few years as demand for paints and coatings has substantially increased from the construction and automotive sectors.
North America to emerge as leading regional market for Isobutanol
Asia-Pacific is one of the prominent consumers of isobutanol in the global market and is likely to remain a key force over the forecast period as well. The isobutanol market in Asia-Pacific is anticipated to expand at a fast pace during the forecast period due to the steady expansion of the paints and coatings and chemicals industries in the region.
North America followed Asia Pacific in terms of consumption of isobutanol in 2016, with thriving demand for a variety of chemicals, bio-fuels, and paints and coatings from countries such U.S and Canada driving the market. Various small players that offer isobutanol operate in U.S.; hence, the market is fragmented in the region. North America is also key chemical producer, consuming high volumes of isobutanol across a number of applications in the industry. Therefore, the region is likely to be a leading market for isobutanol in the years to come. The isobutanol market in Middle East and Africa and Latin America held meagre shares in 2016. The isobutanol market in these regions is estimated to anticipate expand at a sluggish pace during the forecast period.
Key players operating in the isobutanol market are The Dow Chemical Company, Mistsubishi Chemical Company, BASF SE, Eastman Chemical Company, Gevo, Grupa Azoty S.A., Saudi Butanol Company, Andra Petrochemicals Limited, Oxea GmbH.
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