Utilization of DSC, NIR, and NMR for wax appearance temperature and chemical additive performance characterization Yansong Zhao • Kristofer Paso • Jens Norrman • Hassan Ali • Geir Sørland • Johan Sjo ¨blom Received: 11 August 2014 / Accepted: 18 January 2015 Ó Akade ´miai Kiado ´, Budapest, Hungary 2015 Abstract Wax crystallization processes are investigated using differential scanning calorimetry, near-infrared spectroscopy, and nuclear magnetic resonance spectros- copy. The performance of a chemical additive is assessed using calorimetry and NMR. Heat flows of model waxy oils are obtained using differential scanning calorimetry, providing the wax appearance temperature and crystalli- zation profiles. The effect of cooling rate, wax content, asphaltene, and chemical additive on the wax appearance temperature is investigated. The wax appearance temper- ature increases with increasing wax contents. The wax appearance temperature decreases in the presence of chemical additive, effectively increasing the instantaneous supersaturation. Furthermore, near-infrared spectroscopy and nuclear magnetic resonance spectroscopy are utilized to determine wax appearance temperature. The NMR experiments quantify liquid and solid fractions at thermal equilibrium conditions, effectively circumventing the need for dynamic thermal techniques. Keywords DSC  NIR  NMR  Wax appearance temperature  Wax crystallization List of symbols h Planck’s constant 6.626 9 10 -34 (m 2 kg s -1 ) D Diffusion coefficient (m 2 s) E Energy level (m 2 kg s -2 ) H o External magnetic field strength (A m -1 ) I Spin (dimensionless) I o Integration constant (A m -1 ) M Magnetization (A m -1 ) M 0 ? Integration constant (A m -1 ) T Characteristic relaxation time (s) c Magnetogyric ratio (A s kg -1 ) v Velocity (m s -1 ) x Frequency (s -1 ) 5 Del operator Subscripts x, y, z Cartesian coordinates Introduction Flow assurance associated with waxy oil pipeline transport is essential for the petroleum production industry. Paraffin wax may precipitate in the bulk oil when the temperature drops below wax appearance temperature (WAT), and the precip- itated wax will hinder flow. Therefore, WAT is an important flow assurance parameter for the petroleum production industry, and it is necessary to develop accurate and precise methods to determine WAT. Various methods have been developed, and are used, to measure WAT, such as rheom- etry [1–3], densitometry [4, 5], cross-polarized microscopy [6, 7], differential scanning calorimetry (DSC) [8–10], and Y. Zhao  K. Paso (&)  J. Norrman  H. Ali  J. Sjo ¨blom Ugelstad Laboratory, Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway e-mail: kristofer.paso@chemeng.ntnu.no; kristofer.g.paso@ntnu.no Present Address: Y. Zhao Energy and Climate Group, Department of Physics and Technology, UiT The Arctic University of Norway, 9037 Tromsø, Norway G. Sørland Anvendt Teknologi AS, 7022 Trondheim, Norway 123 J Therm Anal Calorim DOI 10.1007/s10973-015-4451-1