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Tom Stoppard, the legendary British playwright, and Petrochemical Process Technology?
19 April 2021Dr. Jeffrey S. Plotkin
Tom Stoppard wrote the following: "Skill without imagination
results in useful products such as wicker baskets while imagination
without skill gives us modern art." But what about skill and
imagination? In my view, this combination gives us petrochemical
process technology (admittedly I am biased)! Why do I say this?
Think about it. The petrochemical industry literally takes fire,
earth, air, and water and produces all of the plastics, rubbers,
and fibers that allow modern living. Surely, that takes both skill
and imagination, in large measures.
As just one example of the skill and imagination inherent in the
petrochemical industry, one of my favorite topics is the absolute
beautiful development of process technology to make propylene
oxide. Propylene oxide (PO) is a relatively simple molecule, but
not easy to make. Unlike ethylene oxide, which can be made by
direct oxidation of ethylene using silver-based catalysts, PO
cannot be made by direct oxidation as the "third" carbon is too
sensitive to oxidation and is too easily burned to
CO2.
Thus, indirect means "had to be developed". The historical
route, and by the way still the predominant route to PO, is via
chlorohydrin technology. Interestingly, Dow Chemical, the biggest
producer of PO only used chlorohydrin technology up until 2009.
In the 1969-1972 timeframe, there were two breakthrough
peroxidation technologies developed for making PO. Both approaches
make co-products, either t-butyl alcohol (TBA) which is used as an
intermediate for making MTBE or, in the other approach, styrene
monomer. Currently, LyondellBasell and their partners Covestro,
Shell Chemical, Repsol, Indorama Ventures, Huntsman, and SK
Chemical operate one or both of the co-product technologies.
Another round of process innovation occurred with the
development of two so-called co-product free routes. Sumitomo
Chemical developed the first of the co-product free technologies in
2003 with their cumene recycle route. In 2008-2009, the Dow/BASF
partnership resulted in a route based on using hydrogen peroxide as
the oxidant and, at almost the same time, Evonik independently
developed a similar approach.
As shown on the chart below, all five of the PO technologies are
still employed. The first-generation chlorohydrin route is still in
use but is considered to be high cost with only chain integrated
chlor-alkali producers participating. It is unlikely that
chlorohydrin technology will be selected for future projects,
especially as China in now pursuing stricter environmental
policies.
The co-product routes combined comprise over 40% of global PO
capacity with styrene co-product being the larger of the approaches
and is projected to be the favored approach going forward as MTBE
demand is being negatively impacted by the Chinese mandate to use
ethanol in gasoline.
The hydrogen peroxide route (HPPO) is the newest of all the
routes but has grown quickly since 2009 and now comprises 20% of
capacity share. HPPO has the advantage of not being tied to the
market ups and downs of any co-product but requires a co-located
hydrogen peroxide plant as long distance transport of hydrogen
peroxide is not feasible as it is highly perishable.
The cumene recycle process is the least employed of all of the
PO technologies. This route, like the HPPO process, also enjoys the
advantage of making no co-product but suffers from higher variable
and fixed costs than the co-product routes, excluding the credit
for the co-products.
The key use of PO is in the manufacture of polyether polyols
used in polyurethane production. The value chain associated with
polyurethanes is also another great example of skill and
imagination. I am sure this area will be covered in a future
blog.
For additional Petrochemical information, check out some
of our training courses on the IHS Markit's Learning Center
at: