Improved method for the determination of the organic chloride content in crude oil

The recent release of ASTM Method D-4929-17 offers users more flexibility in the measurement of the naphtha cut coming from the distillation of crude. The method operates on the assumption that all of the chloride present distils over in the naphtha cut. The chloride in the naphtha can be determined by several analytical techniques. This concentration can then be used to determine the amount in the crude by determining the percentage of the crude oil that came over during the distillation.

Historically, the chloride in the naphtha cut was determined by either a wet chemistry titration or a microcoulometric measurement. Since both of these methods have limitations, new or X-ray methods were investigated in this study. At the same time, three different X-ray technologies were simultaneously evaluated during the ILS Study. These included EDXRF technology, MWDXRF, and MEDXRF Technology.

The results of this study are documented in ASTM Research Report RR: D02-1875. The results of these tests are collected together as Analytical Method C of the newly approved method. The results of method C showed improved repeatability (r) relative to methods A and B. The MEDXRF technology as represented by Horiba Scientific’s MESA-7220 proved to be superior to the less expensive technology and as good as the more expensive technology.

The very affordable MESA-7220 offers great low level sulphur measurement capability as evidenced by ASTM D7220. It is also capable of doing higher level sulphur measurements as a part of D4294. This makes it a very versatile instrument for doing sulphur and chloride in crude oil as well as low sulphur levels in fuels.