Moisture content and pH value in crude tall oil (CTO)

Significance of the Topic

The production of crude tall oil as a byproduct of kraft pulping is widespread and its quality parameters such as moisture content and pH are critical for downstream processing and product performance. Rapid and accurate determination of these parameters supports real time process control and reduces reliance on time consuming laboratory methods.

Objectives and Study Overview

This application note presents a feasibility study demonstrating simultaneous determination of moisture content and pH in crude tall oil using visible near infrared spectroscopy. The goal is to develop robust calibration models that enable rapid inspection of raw materials and control of final product quality.

Methodology and Instrumentation

A total of 20 crude tall oil samples covering moisture levels from 0.7 to 2.5 percent and pH values between 3.8 and 5.4 were analyzed. Spectra were recorded in transmission mode over the full wavelength range 400 to 2500 nm at room temperature. Calibration and validation sets were defined for each parameter. Multivariate regression models based on partial least squares and second derivative preprocessing with 10 nanometer segments were developed and validated via internal leave one out cross validation.

Used Instrumentation

• NIRS XDS RapidLiquid Analyzer
• 4 mm path length disposable glass vials
• Vision 4.03 software with PLS algorithm

Key Results and Discussion

• Moisture content determination relied on water absorption bands between 1850 and 1950 nanometers leading to a calibration model with R squared of approximately 0.83 and standard error of prediction near 0.03 percent.
• pH value prediction exploited spectral features in the 1475 to 1550 nanometer region achieving R squared around 0.84 and prediction error near 0.10 pH units.
• Both models exhibited strong correlation between NIR absorbance and reference laboratory values confirming the robustness of the approach.

Benefits and Practical Applications

• Enables rapid in line or at line measurement of key quality parameters
• Reduces analysis time compared to conventional titration and drying methods
• Supports real time decision making in raw material inspection and final product control

Future Trends and Opportunities

Near infrared spectroscopy combined with advanced chemometric techniques is expected to gain wider adoption for process analytical technology in the pulp and paper and biofuel industries Continuous improvements in sensor design and data analytics will further enhance accuracy and enable integration into automated control systems

Conclusion

The study confirms that Vis NIR spectroscopy provides a rapid and reliable alternative to traditional laboratory methods for assessing moisture content and pH in crude tall oil This approach can streamline quality control workflows and support efficient process management

References

• NIR Application Note NIR-36 Moisture content and pH value in crude tall oil