Chemical Analysis of Deposits Separated from Blocked Fuel Filters

<div>Biodiesel was found to be the best candidate to replace diesel fuel mainly due to being renewable, biodegradable, and non-toxic and reduce greenhouse gases, which cause global warming. Nowadays, biodiesel is blended with diesel fuel in different concentrations depending on the country of usage and is used in diesel engines. Concerns about biodiesel were raised after premature fouling of fuel filters were reported before meeting their mileage requirement. Three filters from Brazil were analyzed using different techniques (Energy Dispersive X-Ray [EDX], Fourier Transform Infrared Spectroscopy [FTIR], Thermogravimetric Analysis [TGA], Time of Flight-Secondary Ion Mass Spectrometry [ToF-SIMS], and Gas Chromatography/Mass Spectrometry [GC/MS]) to understand the chemical composition of the filter deposits and highlight the main compounds responsible for the blockage. EDX showed that the deposits are mainly composed of carbon (C) and oxygen (O) with traces of sodium (Na), calcium (Ca), iron (Fe), phosphorus (P), and other elements. FTIR showed that the dominant bands in the filter deposits spectra are attributed to C-O bonds with a broad OH peak always present. TGA showed that the deposits vaporize at three different regions with peak temperatures around 250°C, 350°C, and 480°C, which correspond to the vaporization of glycerol, sterol glucosides (SGs), and metal carboxylates, respectively. Combining the data from the previous techniques, it was concluded that the filter deposits are mainly organic in nature with glycerol and SGs as the main compounds forming the bulk of the filter deposits with metal carboxylates present in lower amounts. This conclusion was further confirmed by ToF-SIMS and GC/MS where all three compounds were detected. In addition, free sterols and monoglycerides (MGs) were also detected in the deposits with traces of diglycerides and triglycerides also present.</div>