Page 131 - CW E-Magazine (12-12-2023)

Point of View

The greening of olefi ns for the chemical industry

The chemical industry is amazing for the value addition it brings about by utilising a small number of feedstock and the deployment of a diverse
set of chemistries and technologies. For much of the recent past the feedstock base of the industry has been fossil fuels – in particular fractions
of crude oil and natural gas – but that is now changing, albeit slowly. Today, as the industry is attempting to transition to a more sustainable
growth path, feedstock choices are being re-examined. Conventional ones are being given a greener tinge through a variety of technological
approaches, and new feedstock, in particular bio-based ones, are seeing a resurgence.

Not all of the technologies that enable the greening of feedstock are ready for commercial deployment at a scale to make a recognisable
impact, but a few are.

The most important building blocks for the chemical industry are the olefins (ethylene and propylene, in the main, but also the butenes) and
the aromatics (benzene, toluene and xylene). The technological approaches now being taken to green them are as varied as they are exciting.

Ethylene
Ethylene is currently mainly produced by steam cracking of ethane-rich gas, naphtha, and from coal through an elaborate process practiced
almost exclusively in China. Gas cracking provides ethylene with the lowest carbon footprint, and, as a bonus, cost, and this is the feedstock
used in much of North America and the Middle East. Naphtha cracking – widely practiced in Europe and South East Asia – operates higher in
the ethylene cost curve, and has a heftier carbon footprint than gas cracking, but some of this disadvantage is mitigated by the wider product
slate. Not surprisingly, coal-based ethylene has the highest carbon footprint, though it is cost-competitive with other routes particularly in a
high oil price environment.
Electrification of crackers
Irrespective of the feedstock (ethane or naphtha), steam crackers are energy-intensive, as they operate at high temperatures and pressures.
The most significant development currently ongoing to lower their energy footprint is through electrification – using renewable power (solar,
wind) and even nuclear energy, instead of high pressure steam, as the energy source.

Several collaborative efforts are ongoing to develop and scale up electrification technology. In one, SABIC, Linde and BASF have teamed up
and selected two options for a large-scale demonstration unit at BASF’s site in Ludwigshafen, Germany. Linde will act as future licensor of the
technology, and the consortium is aiming for first full adoption at a SABIC site sometime in 2027. Another collaboration, involving five European
companies (Borealis, BP, Total Energies, Repsol and Versalis), accounting for about a third of total steam cracking capacity in Europe, is also
working towards an electrified ‘Cracker of the Future’, while in the US, LyondellBasell, Technip Energies, and Chevron Phillips Chemical have
signed a MoU to design, construct, and operate a demonstration unit using Technip’s electric furnace technology. In 2020, Dow and Shell also
announced a joint development agreement to accelerate technology to electrify steam crackers – both existing and new.
Wider deployment of electrification technology is some time away – possibly in the next decade – but industry participants are confident
this is an approach that can be scaled up rapidly once validated, and can even be retrofitted to existing crackers – which is important if a
material difference is to be made. The ethylene from them are expected to have carbon footprints up to 90% lower than from conventional
steam crackers – an advantage that can be passed down the value chain onto the many derivatives made.

Other technological initiatives to lower the carbon footprint of ethylene production centre on use of electric drives in crackers, roto dynamic
reactors, and catalytic cracking of ethane (akin to propane), instead of thermal cracking as practiced now.

Ethanol
Ethanol – produced from bio-based raw materials – is also being used as a feedstock for ethylene manufacture, though the volumes now
made pale in comparison to the classical petro-routes. The bio-based raw material could be starches, sugars (sugarcane, corn) or even biomass
(including agricultural wastes), but the complexity of the process and the costs of manufacture are very different for each. The economics of
biomass utilisation are in particular far more challenging, in large measure due to its recalcitrant nature; so while the technology is more or
less well established, the cost of the ethanol so-produced is daunting. In India, for instance, several 2G ethanol plants using agricultural wastes
such as sugarcane bagasse or wheat straw are being built, but the ethanol is to be mainly used for blending into gasoline, not for chemical
manufacture. Companies making them – mostly set up by the Oil Marketing Companies – will need to realise between Rs. 80-100 per litre of
ethanol, if they are to fully recover costs. This is near-double the cost of the first generation (1G) ethanol produced from sugarcane molasses,
sugarcane juice or food grains.

Chemical Weekly December 12, 2023 131

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