Limitations of the Pour Point Measurement and the Influence of the Oil Composition on Its Detection Using Principal Component Analysis

A method for maximum and minimum pour point determination in crude oil was applied, and the chemical composition of 80 samples, American Petroleum Institute (API) gravity, total acid number (TAN), density, kinematic viscosity, and sulfur, asphaltene, and wax contents were analyzed in association with chemometric methods. The results of the 80 analyzed samples showed maximum pour point temperatures from 9 to -36 degrees C and minimum pour point temperatures from 12 to -36 degrees C. Heavy oils with asphaltenic chemical composition showed more positive values of pour point (5-8 degrees C) and showed no significant difference between the maximum and minimum pour points considering the repeatability of the method (3 degrees C for maximum and 6 degrees C for minimum). However, the oils with chemical composition with higher wax content and higher API gravity showed lower pour point values from -24 to -6 degrees C (maximum) and from -30 to -18 degrees C (minimum), respectively. The principal component analysis (PCA) explained 92% of data variability, showing that the differences among the properties of the samples allowed for their separation by groups and some properties are closely correlated to the pour point.