Fuel Instability Studies: The Chemical Validation of Astm Method D5304

Abstract

The current ASTM (D5304) procedure for determining storage stability involves rather drastic conditions, namely, 16 hours at 90 C and under 100 psig of oxygen. These mandated test conditions give rise to the question, ''Does the reaction conditions induce chemical instability, or is it an accurate measure of the true instability process?'' Several organo-sulfur functional groups are known to be present in petroleum derived fuels. Thiophenes, benzothiophenes, sulfides, disulfides, and trace amounts of thiols are the organosulfur compounds most prevalent. The reaction of organosulfur compounds under the ASTM reaction conditions have not been investigated. The purpose of the present research is to determine if the ASTM reaction conditions induce a reaction in an otherwise stable fuel matrix.

Physicochemical Characterization of Commercial Biodiesel/Diesel Blends and Evaluation of Unconventional Spectroscopic Vibrational Techniques in the Monitoring of Their Oxidation and Hydrolysis during Storage

“…The 43 °C temperature and storage time of 24 weeks were chosen based on ASTM D4625, which simulates a less stressful fuel storage. A more stressful condition, on the other hand, would be at the temperature of 90 °C, suitable to simulate situations of interest to the automotive industry …”

“…A more stressful condition, on the other hand, would be at the temperature of 90 °C, suitable to simulate situations of interest to the automotive industry. 43 The following analyses were carried out in the studied mixtures at all times, in order to evaluate the degree of sample degradation: oxidative stability by Rancimat (DIN EN 15751 44 ), water content by Karl Fischer (ASTM D6304 45 ), and Raman and HATR mid-infrared spectroscopies. On the other hand, the acid value tests (ASTM D664 46 ), biodiesel content (DIN EN 14078 35 ), and elemental analysis by ICP-AES (ASTM D7111 47 and NBR 15553 48 ) were only analyzed at the beginning and end of the experiments (points 0 and 24 weeks, respectively).…”