2012 Corporate Capabilities - Spectroscopy

www.spectroscopyonline.com
December 2011 Spectroscopy 26(12) 21
Temporary Online FT-IR
Spectroscopy for Process
Characterization in the
Chemical Industry
The focus of this paper will be on the use of temporary online Fourier-transform infrared
(FT-IR) spectroscopy in the chemical industry including two case-study applications involving
fouling and product quality. These case studies will be followed by a discussion of the use of
temporary online FT-IR analysis enabling process optimization.
Serena Stephenson, Lamar Dewald, Esteban Baquero, Wendy Flory, Liane Mikolajczyk,
and J.D. Tate
The Dow Chemical Company (Midland, Michigan)
is the world’s largest integrated chemical company
utilizing a wide variety of unique chemistries in
the production of both basic and specialty chemicals.
The diversity of chemical processes and the interrelationships
of production facilities in the integrated chemical
complex provide significant opportunities for process
optimization. Fouling, corrosion, plugging, or out-ofspecification
product occurrences in one manufacturing
plant can have negative effects on the operation of one
or more downstream facilities. Accurate and representative
data for process characterization is a key factor in
making informed decisions regarding the resolution of
process problems. The information-rich nature of optical
spectroscopy and, in particular, Fourier-transform infrared
(FT-IR) spectroscopy is uniquely suited for rapid and
continuous online process characterization.
Sometimes grab samples of the process that are analyzed
in the laboratory provide sufficient data for process
characterization. However, the nature of a process
stream frequently makes collecting representative grab
samples difficult. Gas-phase samples, reactive samples,
and samples under elevated (or depressed) temperature
or pressure are a few examples of samples that are particularly
difficult to collect and analyze by laboratory
analysis. Streams where trace (for example, low parts per
million) levels of water or carbon dioxide are the analytes
of interest are also a particular challenge for grab
sample laboratory analysis because concentration levels
are easily influenced by atmospheric composition. Safety
issues must also be considered when collecting samples
of highly toxic or explosive materials such as phosgene,
acrylates, ethylene oxide, hydrogen chloride, or isocyanates.
Depending on the duration and extent of required
toxic material analyses, properly designed continuous
online analysis can help mitigate associated safety issues.
Additionally, when the process event of interest is
transient occurring over a short time-frame, occurring
at unknown intervals, or if the process is not at steadystate,
a continuous online analysis of a representative
sample provides a richness of insight into the process
that would not be achievable by the infrequent glimpses
into the process that is attainable by grab sample analysis.
Lastly, continuous analyses are an invaluable tool
during new process development and process scale-up
due to the ability to thoroughly characterize the process.
Of the available analytical tools for temporary online
process characterization, FT-IR is among the most powerful.
FT-IR is a fast technique providing fundamental
vibrational information for the components in the stream
and allowing the capture and retention of informationrich
spectra. The raw data obtained from FT-IR are often