Page 132 - CW E-Magazine (12-12-2023)

Point of View

Corn- and sugar-cane derived ethanol is now commercially used – in India, USA and Brazil, for instance – for making ethylene-derivatives
such as monoethylene glycol (MEG), ethoxylates, and polyethylene (PE). But, in the absence of a carbon tax, commercial success hinges around
the ability of producers to position these as niche products aimed at discerning customers willing to pay a price premium.

Carbon capture and storage (CCS)
An ‘end-of-pipe’ approach to lowering the carbon footprint of ethylene manufacture, involves carbon capture and storage (CCS). Just a
couple of weeks ago, Dow announced that it has taken a Final Investment Decision to build the world’s first net-zero (Scope 1 and 2) integrated
ethylene cracker and derivatives complex in Alberta, Canada. To achieve this, the project will deploy Linde’s air separation and autothermal
reformer technology to convert the site’s cracker off-gas to hydrogen, which will be used as a clean fuel to supply the site’s furnaces. In addition,
CO emissions will be captured and stored, reducing existing emissions by approximately 1-mtpa of CO e, while abating all emissions from the
2
2
addition of the site’s new capacity.
Propylene
Propane dehydrogenation (PDH) is the most sustainable route to propylene today, ranking better than fluid catalytic cracking in a refinery, or
naphtha cracking. PDH is now widely deployed across the world, though the vast majority of recent projects have been in China. The first PDH
plant in India is now under construction by Gail India Ltd. in Usar (Maharashtra), and a couple more are at planning stages.

Several industrial and academic research groups are collaborating to further develop, scale up, and demonstrate a toolbox of novel, efficient,
and flexible PDH technologies. But the key to lowering the carbon intensity of conventional PDH is to source and crack renewable-propane
(r-propane). The most common source of r-propane today is as a by-product of renewable diesel and sustainable aviation fuel (SAF) manufacture,
primarily from vegetable oils, animal fats, or used cooking oil. Today, only a fraction of this r-propane is captured for delivery to the market, and
most is consumed at the plant itself. But r-propane supply is expected to scale on the back of increased demand for renewable diesel and SAF
to meet mandates set by companies and governments for the automotive, industrial and aviation industries. According to data from the US
Environment Protection Agency, while only 4.6 million gallons of r-propane was produced in 2021, within a few years, as much as 100 million
gallons may be available annually, which may triple in the next decade.

To a very limited extent, r-propane is already being used as a PDH feedstock. Since December 2019, Borealis and its upstream partner,
Neste, have been collaborating for polypropylene (PP) production based on r-propane (supplied by Neste from its Rotterdam facility), cracked at
Borealis’ PDH plant in Kallo (Belgium) to produce r-propylene for conversion to r-PP at two of its polymerisation plants.
Methanol-to-propylene
Several methanol-to-propylene (MTP) plants have been built (again mainly in China), but the methanol is of petrochemical, not biological,
origin. Nevertheless, given the renewed interest in obtaining renewable methanol including by gasification of biomass, this is a route that does
offer a way to make greener propylene. Another option is direct catalytic pyrolysis of biomass, but this results in a complex mixture that also
contains propylene.

Metathesis
Bio-ethanol dehydration to ethylene, its dimerization and metathesis offers another route to bio-propylene. The petrochemical version of
this route (involving ethylene dimerization and metathesis) will be practiced for the first time in India to provide propylene for a phenol/acetone
project proposed to be set up by Haldia Petrochemicals Ltd. in Haldia (West Bengal).

While the direct use of bio-propylene to make chemicals and polymers is still limited, a few chemicals prepared from propylene are now
being made commercially from a bio-based raw material, glycerine. The main driver for this has been the availability of glycerine at scale, chiefly
as a by-product of the biodiesel industry. In Asia, the main sources of glycerine are the oil palm growing countries of Indonesia and Malaysia.
The two main propylene-based chemicals made this way are epichlorohydrin, and, to a much lesser extent, propylene glycol. India has one plant
that produces epichlorohydrin from glycerine, and two more are on the cards.

Collaborative effort
Given the size of the olefins industry, and the technological and commercial challenges, transitioning olefins production to a ‘greener’
more sustainable path, will be a slow and challenging process. It will require technology breakthroughs, strong & consistent policy support,
massive risk appetite and entrepreneurial zeal. It is no surprise, therefore, that the approaches are being made collaboratively, and even amongst
companies that compete in the marketplace.

Ravi Raghavan

132 Chemical Weekly December 12, 2023

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