Crude oil is a term for unrefined petroleum, a naturally occurring liquid found in geological formations beneath the earth’s surface. Crude oil can be refined into several valuable types of fuel including petrol, jet, and diesel fuels. Crude oil is ideal for the production of these high-energy fuels, as it contains a large quantity of hydrocarbons. The combustion of these hydrocarbons with oxygen produce the energy needed to operate boilers, engines and other machinery.
While crude oil contains high amounts of hydrocarbons, it also contains water, chloride salts and other impurities. A desalting process can remove many of the impurities. This process involves the addition of water to dissolve the salts and other impurities from the crude oil feedstock. The mixture is then separated; the water goes to an industrial wastewater treatment facility and the refined petroleum is developed into different petroleum products. The desalting process removes the majority of chloride salts, which if present in the oil at high temperatures can form hydrochloric acid. The hydrochloric acid formed can readily corrode equipment throughout the refining process. As a result, the desalting process is crucial to crude oil refining.
Organic chlorides are compounds which contain a carbon-chlorine bond. Examples of these compounds include chloroform and chlorobenzene. Organic chlorides present a more significant problem in crude oil refineries as compared to inorganic chlorides since they are not removed through the desalting process. While these compounds are generally not present naturally, the oil can be adulterated when additives, cleaning solutions or chemicals for oil recovery are used.
As a result, refineries typically do not accept crude oil that contains more than 5 parts per million (μg/g) of organic chloride. Organic chlorides are determined through potentiometric titration per Standard Method ASTM D4929. This method utilizes a sodium biphenyl reduction of the organic chlorides to yield inorganic chlorides. The chlorides are then extracted from the petroleum sample into an aqueous phase and titrated with silver nitrate.
An oil refinery contacted Hanna to determine the organic chloride content of incoming crude oil. The customer required that the titrator conformed specifically to the specifications outlined in the their standard operating procedure, based on ASTM D4929. Hanna offered the Automatic Potentiometric Titration System - HI902C.
In order to accommodate the standard method, the 5mL burette was supplied in place of the 25mL burette. The ORP Half-Cell Electrode with BNC Connector - HI5110B and the Glass Body General Purpose Reference Electrode - HI5311 with HI7072L Electrolyte Fill Solution 1M KNO3 were used since the method specified a silver billet-type half-cell electrode and reference electrode.
The customer appreciated the support offered by Hanna Instruments to ensure that all materials would be supplied for their titration to take place. Although the titrator was supplied with only one burette, the customer was considering expanding their testing to include methods such as acid number (AN), so the option for a second pump and burette to be attached was appreciated. The customer also appreciated the potential for an autosampler expansion on the titrator in the event that their in-house testing needs grew. Overall, the HI902C provided a comprehensive solution to the customer’s current and future testing needs.
