Express Method of Determining the Softening Point of Petroleum Pitch

Abstract

A capillary method is proposed for determining the softening point of petroleum pitch. A pitch sample is heated in a glass capillary by an air flux and observed under a microscope. The softening point is measured at the instant when the pitch within the capillary shrinks and pulls away from the glass walls. The method is tested for two series of petroleum pitch samples: one is derived from heavy pyrolytic tar; and the other from decant oil (heavy gas oil from a catalytic cracking unit with microspherical catalyst). A broad range of softening point is found for these samples by the ring-and-ball method (90–200°C). Given the simplicity of the tests and the ability to determine the softening point over a broader range (up to 330–350°C) than in the traditional method, the capillary method may be recommended for use in determining the softening point of traditional binder and also of high-melting fiber-forming pitch.