Monitoring Tall Oil Distillation with NIR

In the last two years the supply of sustainable and alternative feedstocks to produce basic materials has come into the focus of many traditional producers of petrochemicals, fine chemicals and other basic materials. One such alternative feedstock is tall oil, which can be distilled into economically very valuable fractions, including Tall Oil Fatty Acids (TOFA), rosin soaps and others.

Tall oil is a viscous resin derived from coniferous trees such as pine. It is most often produced as a by-product of the Kraft process for manufacturing wood pulp, in which the cellulosic components of wood are separated from the rest through a combination of chemical bleaching and mechanical separation.

Depending on the purity the tall oil components can then be utilized as a feedstock to produce adhesives, paints, pharmaceuticals and as a substitute for animal-based fats in soaps and lubricants. As a natural feedstock variability of the tall oil composition is higher than in fossil-based ones, making it even more important to monitor the refining process accurately. This can be achieved using FT-NIR spectroscopy in combination with our robust NIR process cells at strategic locations of the distillation column, allowing you to control the process more effectively.

Using NIR to monitor distillation products

Online Near-Infrared analysis can be used to return real-time information on the chemical composition on the refined tall oil products at various stages, with the feed lines for each column being monitored along with the take-off lines for the distilled products.

Traditional process analytics require samples to be removed from the process line for testing by chromatographic or wet chemistry techniques. The length of time between sampling and analysis, delays the taking of corrective action if the process has drifted out of specified bounds. This can cause costly production delays and result in wasted material and effort. With on-line near-infrared sampling, instantaneous feedback is possible.

The near-infrared region of the spectrum contains overtones of the fundamental molecular vibrations seen in mid-infrared spectroscopy. These spectral features fluctuate and shift position as changes in composition occur and can be used to monitor deviation from the expected content of the process line at a given place.

Potential location of an NIR cell for on-line monitoring of a distillation process

Some might say that using the temperature set-points for the ideal location of the take-off points, but by using NIR spectroscopy an advantage is gained as it provides more accurate compositional information rather than just using the boiling points of the components. On top of this, as tall oil quality can vary a lot a detailed analysis is crucial.

Using appropriate pathlengths good quality spectra can be acquired using our process cell with a high transmission, please see below an example of a tall oil spectrum acquired in our laboratory.