Installation of a Multiplexed Raman System in a Chemical Process

Abstract

A 785 nm laser dispersive Raman system was installed in a hazardous chemical production plant to monitor two reactors, a still, and a holding tank with measurement directly through sight glasses. Compositional information for several raw materials, intermediates, and products was obtained using partial least squares (PLS) calibrations. Discriminate analysis was used to exclude extremely poor spectra while including usable ones. Derivative/standard normal variate (SNV) treatment was found to be effective for correcting for background fluorescence and for large differences in spectral intensity. Final regression equations incorporated temperature fluctuations, occasional fluorescence, some sunlight effects, large intensity variations, and large compositional changes. Various installation problems were solved via data treatment or mechanical changes. The Raman system provides information for control of the process, resulting in cost savings and improved safety.

Influence of temperature on the measurement of NaCl content of aqueous solution by short-wavelength near infrared spectroscopy (SW-NIR)

“…The prominent water band at about 970 nm arises from the 2m 1 + m 3 combination transition where m 1 is the symmetric O-H stretch, m 3 the antisymmetric O-H stretch, and m 2 the O-H bending mode [17]. Weak absorption bands arising from 2m 1 + m 2 + m 3 and 3m 1 + m 3 are observed near 840 and 750 nm, respectively [18]. After subtracting the point (value of absorbance) at 594 nm (Fig.…”

Raman Spectroscopy

“…In the production of monochloroacetic acid from acetic acid and acetic anhydride, the concentration of the reaction intermediate, acetyl chloride, which also serves as a catalyst, must be controlled to minimize dichloroacetic acid by -product formation [88] . Recycled process streams are fed back into the process.…”

204 Years of near Infrared Technology: 1800–2003

“…Weyer published a review of NIR spectroscopy of organic substances in 1985. 15 That review covered instrumentation and techniques, and applications (both industrial and agricultural). A total of 164 references were included at the end.…”