The evolution continues

23 July 2004 17:01  [Source: ICB]

Demand for BDO is still strong as commercial developers continue to identify new process technologies, writes Mark Morgan. But if the structure of global supply changed back in the 1990s as new technologies were commercialised, what will the picture look like in another ten years?

Butanediol (1,4-butanediol, BDO) continues to be a fertile field for technical innovation and process development. Global consumption of BDO was nearly 0.82m tonne in 2003. Approximately 304 000 tonne of BDO was consumed in tetrahydrofuran (THF) production, corresponding to about 37% of the market. Some 234 000 tonne of BDO was consumed in polybutadiene terephthalate (PBT) production. BDO for PBT is mostly a merchant market, with the exception of Western Europe. In contrast, -butyrolactone (GBL) production now accounts for 16% of the virtually captive BDO market.

Demand for BDO, for THF and GBL, will only show modest growth as new investments in BDO, for example via Davy technology, will co-produce these intermediates. But in countries like China, where new investments in acetylene-based processes are under way, THF will be made from BDO. Indeed, even in North America in recent years, Penn Chemical closed its furfural THF plants in favour of investing in BDO dehydration. In future Lyondell plans to build additional BDO derivative capacity in Europe such as THF, GBL and polytetramethylene ether glycol (PTMEG). The new acetylene units in China will probably follow a similar strategy.

North America consumed nearly 333 000 tonne of BDO in 2003, about 40% of total demand. Western Europe was the next largest consumer, while East Asia accounted for 142 000 tonne, less than 20% of demand. North America and Europe will remain the largest BDO consumers, accounting for 67% of the global total of 1.26m tonne in 2015. East Asia has already overtaken Japan as the next largest consumer after western Europe and strong growth is anticipated. The average annual growth rate for BDO over the medium to long term will be 4.0%/year. However, a number of factors could drive this number much higher.

For example, putting new capacity for BDO and derivatives in China could stimulate the market and encourage new investment in derivatives. India has a strong history of polyester fibre production, with Reliance a major global producer. India could, potentially, emerge as a major PBT and spandex producer in future. Another factor is how fast the global spandex industry rationalises capacity and relocates production to Asia. And further major investments in new PBT capacity could also drive growth.

A number of consortia have been planning massive worldscale PBT plants in western Europe and East Asia, with the DuBay project now onstream. Worldscale PBT plants in Asia could drive BDO demand, because at full operation an 80 000 tonne/year PBT plant needs around 41 000 tonne of BDO. Although BASF and Toray have announced a major Malayan PBT investment, others may follow and radically change the face of BDO demand.

BDO production

This was the first commercial BDO process (Reppe process) and required careful handling of acetylene. BDO made in this way provided one of the chemical routes to butadiene developed during World War II to support synthetic rubber production.

The chemistry is straightforward, using a copper/bismuth catalyst. The reaction of formaldehyde with acetylene produces 1,4-butynediol via propargyl alcohol and subsequent stages of hydrogenation provide 1,4-butenediol and finally BDO. Butynediol and butenediol have their own commercial end-uses as well as being intermediates in BDO synthesis.

It is ironic that Mitsubishi developed a butadiene process to make BDO when BDO was originally made to make butadiene.

This was the first non-acetylene process to be commercialised and proceeds via
acetoxylation followed by hydrogenation and hydrolysis. The process can be designed to make BDO, THF or both.

Propylene Oxide:
Lyondell (formerly Arco Chemical), using technology originally developed by Kuraray, produces 1,4butanediol using propylene oxide as a feedstock.

The first step in the Arco process is the isomerisation of propylene oxide to allyl alcohol. The second step is the hydroformylation of allyl alcohol to 4-hydroxy-
butyraldehyde. The third and final step is the hydrogenation of the 4hydroxybutyr-aldehyde to BDO.

Analogous to this process is the Dairen process operated in Taiwan. However, in this case, allyl alcohol is derived from propylene via allyl acetate. The chemistry is similar to vinyl acetate production using propylene acetoxylation. Allyl acetate is converted to allyl alcohol via dehydration, with the recovered co-product acetic acid recycled.

n-Butane/Maleic Anhydride:
During the 1990s a number of butane-based processes were commercialised proceeding via maleic anhydride and maleic ester, maleic acid and such.

The first units built used the Davy (ex- Kvaerner) process concept where maleic anhydride is converted to the ester which then undergoes fixed-bed hydrogenolysis to make a mixture of BDO, THF and GBL. The first licences used ethanol, but later generations use methanol.

The Davy process can, in principle, be integrated with any commercial maleic anhydride process. In recent projects, for example BASF/Petronas in Kuantan, Malaysia, the Davy process has been integrated with Huntsman Mars V/VI maleic anhydride technology.

The BP/Lurgi Geminox process, however, uses a fluid n-butane oxidation process to manufacture maleic acid. Hydrogenolysis of maleic acid produces a mixture of BDO, THF and GBL.

The DuPont transport bed concept has been used to make THF from n-butane in Gijon, Spain. Rather than reacting n-butane with free oxygen in air, the transport bed catalyst ‘fixes’ oxygen in a regeneration system and becomes an oxygen carrier/catalyst for the conversion of n-butane to maleic acid.

The structure of global BDO supply changed in the 1990s as new technologies were commercialised and existing plants expanded. But what will the picture look like in another ten years?

BDO improvements

Several process improvements have been made over the years.

There have been limited enhancements to acetylene processes, although patents to BASF (WO 98/15513) and Linde (DE 19624850) indicate attempts to improve product quality and in, the case of Linde, attempts to commercialise a new acetylene-based BDO process.

New acetylene-based capacity is considered by many commentators to be uncompetitive in the BDO world of today. However, in China, coal is competitively priced, labour costs are low and acetylene-based BDO is a commercial reality. An acetylene-based VCM/PVC plant makes reasonable returns serving the domestic market.

In North America acetylene-based BDO plants using calcium carbide-based acetylene have closed, but China is another matter. Coal provides the power for calcium carbide production from the electrolysis of coke and lime. Methanol can be imported, or made from coal-based synthesis gas if necessary, to make formaldehyde and so forth.

Apart from some process improvements in Mitsubishi technology, Eastman developed a route to THF via butadiene epoxidation using a supported silver catalyst.

The product of epoxidation is 3,4-epoxy-1-butene, which finds commercial use as a versatile intermediate for a variety of fine chemicals for agrochemicals and pharmaceuticals. The second step in a THF process is the isomerisation of the 3,4-epoxy-1-butene to 2,5dihydrofuran. Hydrogenation of 2,5-dihydrofuran affords tetrahydrofuran.

n-Butane/Maleic Anhydride:
Davy continues to simplify its esterification/hydrogenolysis process reducing complexity, equipment items and capital costs. It is now possible to manufacture large amounts of THF in the Davy process. The hydrogenolysis step proceeds with the conversion of dimethyl maleate into GBL. The hydrogenation of GBL yields BDO. Admixing a dehydration catalyst with the hydrogenation catalyst affords instantaneous conversion of BDO to THF. An n-butane to PTMEG process should, therefore, be feasible.

During the late 1990s BASF bought the rights to the Kvaerner Mk 3 BDO process. BASF is currently building a worldscale 80 000 tonne/ year THF unit at Caojing in the Shanghai industrial park in China supporting captive 60 000 tonne/year PTMEG (Poly-THF) production. According to press reports, BASF has developed proprietary technology for the direct conversion of
n-butane into THF. However, if BASF has Kvaerner (now Davy Process) technology, then a THF process without BDO production is probably more likely.

There is probably still the need for a maleic anhydride intermediate. Patents awarded to BASF (US 6,350,924, Fischer et al) describe integrating maleic anhydride purification with esterification, which would be a big cost-saving. Combining this with hydrogenolysis could be possible, but there are many technical challenges.

Several companies have recently developed a biotransformation process for BDO. In North America, a consortium involving Argonne National Laboratory, Oak Ridge National Laboratory, Pacific Northwest National Laboratory and the National Renewable Energy Laboratory, has been supported by the United States Department of Energy’s (US DoE) Alternative Feedstocks Programme. The consortium aims to commercialise the process with Applied Carbochemicals and Arkenol, respectively.

Mitsubishi is collaborating with Ajinomoto to commercialise a biotransformation succinic acid plant in East Asia, to produce the biodegradable polymer Bionelle.

Meanwhile, the chemistry of the joint DuPont-Genencor biotransformation process for 1,3-propanediol manufacture is well known. DuPont and Tate & Lyle plan to commercialise this anaerobic process, and will need to overcome some unique challenges, especially to make costs competitive with petrochemically derived PDO.

Applied Carbochemicals plans to build a 45 000 tonne/year glucose to succinic acid facility in North America in the short to medium term. Some of the succinic acid produced could also be used to manufacture methyl, ethyl and butyl esters for solvent applications and more specialised products like itaconic acid.

Using corn-derived ethanol would maintain a complete chain of products derived via biotransformation of raw materials from renewable resources. To date Applied Carbochemicals has undertaken fermentation trials at the 150 000 litre pilot scale and new second-generation micro-organisms are being developed.

The patent literature is replete with organisms besides Escherichia coli to facilitate glucose conversion to succinic acid (US5,723,322/US5,504,004, etc). For example, bacterium 130Z (ATTC 55618), derived from the rumen contents of cattle, and Anaerobiospirillum succiniproducens both show good activity.

Relatively high yields reported by Applied Carbochemicals suggest that many of the challenges of anaerobic fermentation have been overcome. In later work DuPont and Genencor were able to genetically engineer new micro-organisms, curiously based on E.coli with inserted cloned genes, with much higher PDO production rates. In time, PDO production could realise world-scale capacities of over 100 000 tonne/ year.

Fermentation poses many challenges, because the activity of the micro-organisms will determine reactor size, cycle times, and have a major impact on process economics. pH control is also a challenge, because the lower the pH the greater the chance of killing the microbial catalyst.

Succinic acid is converted to the salt in situ. Succinic acid must be recovered using novel techniques such as electrodialysis. Companies like Ameridia specialise in these kinds of separation processes.

Obtaining succinic acid solution is only part of the process, but it is possible to conceive of a succinic acid to BDO process similar the maleic acid hydrogenolysis component of the Geminox process.

Early indications are that the cost of producing BDO by biotransformation processes should be comparable with selected commercial processes. Production capacities are as follows:

- Biotransformation, 50 000 tonne/year,

- Reppe, 200 000 tonne/year, fully integrated Reppe with partial oxidation acetylene,

- Davy, 110 000 tonne/ year, Mk II,

- Geminox, 60 000 tonne/ year.

BDO and THF technology has come some way since the first acetylene-based process developed by IG Farben in the 1930s. Today, many cost competitive technologies are employed in different regions of the world.

However, technology and commercial development have not always been in harmony, leading to dislocations in the market. As the industry looks to the future, with the potential now to commercialise a biotransformation process, it may prove difficult to avoid resisting further capacity increases.

Mark Morgan is a senior consultant, Nexant ChemSystems, based in London and EMEA director of the Nexant ChemSystems Process Evaluation and Research Planning Programme (PERP)

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