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12 neW or improved proCesses Category
To ensure safe scale-up and obtain
important infor mation on the activity
of the catalyst, the range of byproducts,
and aging behavior, the catalyst was
tested in pilot reactors
333 Because the purity of the isobutene was a central requirement
of the customer, developers focused particular attention
on the byproducts: What quantities of what byproducts does the
process generate? What currently unknown impurities could
form? How does the catalyst react to the impurities? Are byproducts
enriched, for example, in the separation columns of the return
circuit, or do they actually disturb the entire process? Very
difficult separation steps were piloted and optimized in individual
columns in the lab.
The energy balance has to fit
Today, new processes hardly have a chance in the chemical industry
if they cannot promise resource and energy efficiency.
Sophisticated energy integration was therefore a high priority
to the engineers who designed the commercial isobutene production
plants. Normally, hot and cold material streams are connected
to minimize overall consumption of cooling water and
steam. If consumption of cooling water and steam is reduced,
energy costs and energy­related carbon dioxide emissions are
also reduced. Engineers also intervened in the process—for
example, by increasing the pressure level in the columns and
reactors—to maximize internal heat exchange.
elements34 Issue 1|2011
The new isobutene process is energy­saving from beginning to
end: for instance, the process consumes only half as much superheated
steam as a comparable process without energy recoils,
or like competing processes that produce isobutene by other
chemical processes. The savings amount to several million euros
per year. For example, Evonik invested about 10 percent of the
total cost of building the commercial plants in energy integration—an
investment that will pay off in only a few years, given
the inexorable rise in energy costs.
Two plants on two continents
completed in one year
One special and unprecedented challenge for everyone involved
was developing the process for two completely different plants
on two continents: in the C4 integrated production network in
Antwerp for production of isobutene, and in Shanghai, where
Evonik operates an MMA production network that produces not
only methyl methacrylate and polymethyl methacrylate, a
granulate widely used as PLEXIGLAS®, but also a number of
specialty monomers for the Asian market that are used in adhesives,
in contact lenses, and in various products of the paper
and rubber industries as well as in wastewater treatment. Unlike