Investigation on Avoiding High-Molecular Aging Products in Middle Distillates with Alternative Blend Components under Technical Conditions

During the aging of fuels, deposits can be formed which in turn can cause disruptions and failures in the application technologies. In this project, tests concerning deposit formation were conducted. A long-term storage test was combined with multiple test rigs. The aim of the project was to determine the prerequisites for the formation and the composition of the formed deposits, as well as to find approaches to avoid deposit formation. Different analytical methods were used on both the fuels and the deposits to document changes in the fuel and to determine the components of the deposits. During the tests using FAME-blends without additives, two different types of deposits were found. One type was found during the long-term storage at 8 °C in B20 and B100 after the first few months, and could be identified as side products of the production process of FAME. This deposit type consists mainly of saturated monoglycerides. It redissolved in the fuel at a room temperature of 20 °C. Used methods were primarily 2D-GC and NMR techniques. In the tests rigs, a different type of deposit was found. This type consisted primarily of oxygenated FAME, long alkane chains, as well as smaller amounts of polyaromatics and FAME. From the composition alone, it is not possible to deduct the actual development of the deposits. One theory is that components of FAME diffuse into deposits formed from polyaromatics and cause them to swell. This might also explain why no test rig failure was found with pure FAME. The deposits in the 18-months long-term storage could be prevented by small doses of additives. In the test rigs, the small additive doses could prolong the time until failures occurred, and did not cause changes of the deposit composition.

The IGF project 18951 N of the research association DGMK Deutsche Wissenschaftliche Gesellschaft für Erdöl, Erdgas und Kohle e.V., Überseering 40, 22297 Hamburg was funded via the AiF within the framework of the programme for the funding of joint industrial research (IGF) by the Federal Ministry of Economics and Energy on the basis of a resolution of the German Bundestag.