HFRR and SL-BOCLE Lubricity of Paraffinic Diesel Fuels Considering Different Origins and Final Formulations with Biodiesels and Additives

The lubricant characteristics of different paraffinic diesel fuel formulations, including biodiesel and lubricity improvers, were tested and compared with the characteristics of conventional middle distillates. The procedures to evaluate the ability to avoid seizure were the high-frequency reciprocating rig (HFRR) and scuffing load ball on cylinder essay (SL-BOCLE) test. The paraffinic fuels selected for this work were as follows: gas to liquid from gas reforming, coal to liquid from coal gasification, and two hydrotreated vegetable oils (isomerized and nonisomerized). Other key variables were analyzed including the following: the blending of fatty acid methyl esters (0.05-7% v/v), the use of lubricity improvers (50-500 mg/kg), and product aging. The correlation between the HFRR and SL-BOCLE tests for paraffinic fuels was similar to conventional middle distillates, resulting in HFRR being a more severe test than SL-BOCLE. No sample of paraffinic diesel showed good lubricant behavior in HFRR tests and poor performance in SL-BOCLE tests. The sensitivity of both tests evaluated is different with respect to the lightest components because SL-BOCLE purges volatiles during initial bubbling. The results demonstrated the effectiveness of the HFRR test to certify diesel fuel lubricity, as it is more restrictive than the SL-BOCLE test. The results show that HFRR is sufficient to control the lubricity of paraffinic fuels and it is not necessary to incorporate SL-BOCLE as an additional test to control such properties.