EXPLANATION
Organic chloride species are potentially damaging to refinery processes. Usually they are not known to be naturally present in crude oils and usually result from cleaning operations at producing sites, pipelines, or tanks. Hydrochloric acid can be produced in hydrotreating or reforming reactors and the acid accumulates in condensing regions of the refinery. Unexpected amounts of organic chlorides cannot be effectively neutralized and damage can result.
This test method determines organic chloride above 1 ppm levels in crude oils using distillation followed by either sodium biphenyl reduction and potentiometric titration, or microcoulometry.
TEST SUMMARY
Crude oil sample is distilled to obtain the naptha cut at 204° C (400° F). The naptha cut is washed successively with caustic and water to remove hydrogen sulfide and inorganic chlorides. This washed naptha fraction can be analyzed by two different procedures.
Method A - The washed naptha fraction is extracted with a solution of sodium biphenyl in toluene. The excess reagent is decomposed, the mixture acidified, and the phases separated. The aqueous phase is evaporated to a smaller volume and is potentiometrically titrated with standard silver nitrate solution.
Method B - The washed naptha fraction is injected into an oxidative furnace, and the resultant chlorides and oxychlorides are coulometrically titrated with silver nitrate.
Interferences - In Method A, HI and HBr will also titrate and give a positive response. In Method B, HI and HBr will also titrate and give a positive response. HOBr and HOI do not react in the titration cell, approximately 50 % microequivalent response is detected. In both methods total sulfur concentration of up to 10 000 times the chlorine level can be tolerated.
TEST PRECISION
