Reinventing itself

08 February 1999 00:00  [Source: ICB]

Acetaldehyde producers are driven to look for new markets as modern acetic acid production routes abandon the old acetaldehyde technology. Is VAM production the way to mop up that excess capacity?

According to consultancy Tecnon (UK), world acetaldehyde capacity in 1998 stands at 3.07m tonne/year and with world production standing at 2.08m tonne/year there is utilisation of only 67.8%.

'Acetaldehyde is a mature, medium-volume petrochemical,' says Bill Tollett, the Tecnon consultant who monitors acetaldehyde. Nearly 75% of world consumption of acetaldehyde is for the production of acetic acid, acetic anhydride and acetate esters. 'While downstream demand for these materials is growing, unfortunately for acetaldehyde, the growth will be satisfied by modern production routes which do not use the old acetaldehyde technology,' says Tollett.

Capacity

In a new study, Tecnon estimates that world consumption of acetaldehyde between 2001 and 2007 will shrink by an average of 1.8%/year. Tecnon also predicts that capacity will close during the same period at an average of 2.3%/year. Some capacity is old and it is reasonable to expect that it be closed. Other capacity is new and, indeed, world acetaldehyde capacity is generally in good condition.

In Europe, Celanese is the largest acetaldehyde producer. Following the recent decision to close its 180 000 tonne/year acetic acid plant at Frankfurt in mid-2000, there must be a question mark over the future of the 120 000 tonne/year acetaldehyde unit there. Celanese produces acetic acid from purchased ethylene.

The acetaldehyde plants are located at Knapsack and Frankfurt in Germany, where Celanese has captive consumption for acetic acid manufacture, and at Lillebonne in France. There is no acetic acid production in Lillebonne, the newest of the Celanese acetaldehyde plants. Built in 1979-1980 it has 96000 tonne/year capacity.

Celanese is eventually expected to change the technology it uses for acetic acid production in Europe away from acetaldehyde-based technology to methanol carbonylation. It might then withdraw completely from acetaldehyde production, as it has in the US. It could seek acetaldehyde for resale and for its residual in-house consumption and leave the free market essentially for BP Amoco Chemicals and Svensk Etanolkemi AB (Sekab), the other significant free market suppliers. Tecnon would be surprised if this happened as it would put the remaining downstream Celanese business at risk. Further, consumers would probably not be happy with the situation. As Celanese has a need for acetaldehyde for purposes other than the manufacture of acetic acid, it could well be that the company will continue to run at least one of the European acetaldehyde plants.

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BP has had a long-term arrangement with EniChem in Italy over the acetaldehyde production at Priolo and the acetyls business at Porto Marghera, which is coming to an end. Some of the acetaldehyde is used at Porto Marghera to produce ethyl acetate for BP and some is sold by BP on the free market. BP has announced the termination of the toll manufacturing of ethyl acetate by EniChem in 2000. What has not been established is the future of its merchant market position, reselling EniChem acetaldehyde.

In the US the reduction in demand for acetaldehyde for downstream derivatives has led to a reduction in plant capacity. In 1991 Eastman shut down one of its two ethylene oxidation, 113 000 tonne/year acetaldehyde plants at Longview, Texas. Celanese withdrew from acetaldehyde production in the US in 1994 on the basis that the costs of meeting improvements required by environmental regulations were too great. This move left Eastman as the only domestic US producer.

Now Pemex supplies 50 000 tonne/year of acetaldehyde from Mexico to Celanese in North America. This material goes to Celanese in Texas and Canada for captive consumption (up to 25 000 tonne/year) and for resale (up to 25 000 tonne/year). Celanese uses acetaldehyde captively for pentaerythritol and 1,3-butanediol production.

In late 1995 Eastman announced the restart of the second Longview acetaldehyde unit to enable the company to meet what it described as 'an increased demand for US-based production of acetaldehyde'. Eastman now has both its 113 000 tonne/year trains for acetaldehyde in production. There is cracker capacity at Longview and Eastman now has a spur of the ethylene pipeline grid into Longview which, it claims, will increase security of supply of acetaldehyde.

Since the reopening of the second acetaldehyde train by Eastman, the US has been over-supplied and this over-availability is causing the market to reexamine opportunities for downstream product manufacture.

Many high value, small volume derivatives of acetaldehyde are possible. Acetaldehyde is used for the manufacture of poly-N-vinyl acetamide (PNVA), a new functional absorbent polymer developed by Showa Denko in Japan. PNVA requires acetic acid, acetaldehyde and ammonia as starting materials. Showa Denko has several different types of this polymer, from highly cross-linked to linear. The material is non-ionic and could be developed as a water absorbent material (although not for use in nappies) and as an additive for cement.

Technology

Showa Denko intends to commercialise the polymer and is planning to sell N-vinyl acetamide monomer. Another product being discussed is sorbic acid used in the manufacture of potassium sorbate for food preservation.

'Potassium sorbate is a significant product,' says Tollett, 'but not big enough to mop up the available acetaldehyde.

'In India there is technology in use for the production of vinyl acetate monomer (VAM) by the reaction of acetaldehyde and acetic anhydride, via an ethylidene diacetate intermediate which is hydrolysed,' he continues. 'VAM is a large volume product around the world and Tecnon estimates the current production as approaching 4m tonne/year. It is perhaps very significant that Eastman, the only US acetaldehyde producer and a major acetyls company without VAM production, has recently published International Patent Applications (WO 98/25879 and WO 98/25880) on the preparation of VAM from acetaldehyde. Is this the way forward for all that under-utilised acetaldehyde capacity?''Acetaldehyde & synthetic ethanol 1997-2007 world survey,' Tecnon (UK).'Acetic acid & vinyl acetate 1996-2006 world survey,' Tecnon (UK). Contact: Sandy Bennett, tel +44 171 924 3955, fax +44 171 978 5307.

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