New uses needed to absorb C 4 olefins glut

Despite significant growth in demand for C₄ olefins in the coming years, increased supplies from ethylene plants will likely create a market glut, says Chem Systems Inc., Tarrytown, N.Y.

Creative schemes for integrating C₄ olefin use in refinery and petrochemical processes will be needed to absorb this excess supply. New derivatives and alternative processing routes will be key in balancing the market for these chemicals.

Supply/demand

Global demand for butadiene, isobutylene, and butene-1 will climb to 11.2 million metric tons, 18.8 million tons, and 1.7 million tons, respectively, by 2010, says Chem Systems. But, because the rate of butadiene demand growth will continue to be outstripped by ethylene demand, more hydrogenation capacity will be needed to absorb the surplus of mixed C₄ streams, according to the firm.

Chem Systems analysts say global demand for butadiene over the long term will grow 3.3%/year on average, compared with 4.9%/year growth for ethylene.

Western Europe is the largest butadiene exporter, and the U.S. the largest importer (see map). Over the medium to long term, the U.S. may be able to supply domestic butadiene demand from its own resources, provided heavy-feedstock cracker projects come on stream as scheduled, says Chem Systems.

New investment in ethylene capacity worldwide, combined with the trend toward cracking heavier feedstocks, will result in a large surplus of mixed C₄s. In order to maintain price stability, these surplus C₄s are likely to be hydrogenated.

Selective hydrogenation will be used to convert butadiene to butenes, where there is adequate downstream C₄ olefin upgrading capability, Chem Systems said. Continued investment in new naphtha-based ethylene capacity in Asia and the potential for the U.S. to crack heavier feedstocks may result in investment in more localized C₄ processing capacity and a regionalization of C₄ markets, which will affect C₄ exporting regions such as Europe.

Derivative schemes

Increased demand for propylene will encourage more refiners to consider modifying the operation of their fluid catalytic cracking units to produce more propylene for extraction. "This, too, will produce more butylenes to add to those derived from steam cracking," said Chem Systems.

"While MTBE, despite current concerns in the U.S., will still dominate global isobutylene demand, chemical derivatives such as polyisobutylene and methyl methacrylate, will continue to grow rapidly." Chemical demand for isobutylene will remain a fraction of refinery consumption.

Demand for butene-1 as a comonomer for producing linear low-density polyethylene (Lldpe), however, will come under increased pressure from hexene-1 in most markets. A number butene-1 projects are planned worldwide, based on ethylene dimerization and extraction technologies.

While Lldpe and high-density polyethylene will continue to dominate butene-1 demand, emerging derivatives such as butene oxide will become more significant.

While normal butenes are used for some chemical derivatives such as methyl ethyl ketone, most find use in the refinery or LPG pools. The need for more propylene is encouraging investment in metathesis technology to react butene-2 and ethylene to produce propylene in both cracker and refinery operations.

Integration key

Chem Systems stresses that integration and assessing value-added options is the key to C₄ upgrading.

"Prior to the introduction of selective hydrogenation in Europe, the surplus of mixed C₄s and butadiene in the late 1980s and early 1990s resulted in excessive co-cracking in Europe, thus lowering C₄ values. The introduction of hydrogenation technology has helped to stabilize the market.

"However, there is still emphasis on adding value to C₄s throughout the chain by judicious integration of C₄ processes and also enhanced cracker-refinery integration. While new technologies for C₄ processing have been developed, including skeletal isomerization and olefin-paraffin separation-as well as new derivatives-there remains a need to develop new processes to consume the ever-growing C₄ surplus while continuing to add value," said Chem Systems.