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2025

Determination of crude oil moisture by Karl Fischer Coulometric method

I. Preface

The Karl Fischer coulometric method is often used to detect samples with trace moisture. The common samples are liquid samples, which are usually convenient to directly add to the electrolytic cell and cause relatively little pollution to the electrolytic cell. However, for some solid samples that are difficult to dissolve in the electrolytic cell solution, this method is not suitable for this detection. To solve such problems, We chose to heat it in a gas furnace and use dry gas to blow the vaporized moisture into the electrolytic cell to achieve the purpose of detecting its moisture content.

This method uses the JH-C3 fully automatic coulometric moisture meter to determine the moisture content of solid samples and detect the moisture content in their products.

Ii. Instruments and Reagents

2.1 Instruments

JH-C3 Karl Fischer moisture analyzer (Coulomb method), analytical balance, etc

2.2 Reagents

Karl Fischer titrant, pure water.

Iii. Experimental Methods

3.1 Sample Testing

Turn on the Coulomb moisture meter, enter the system interface, establish the method in the editing method interface, then enter the test interface, input the sample information, select the established method, click Start, and wait for the pre-electrolysis of the instrument to be completed. Set the preset temperature of the gas furnace to 120℃ and the heating time to 5 minutes. Wait until the moisture in the sample is completely vaporized. Click on the system injection on the Coulomb moisture meter, insert the gas needle into the sample bottle, turn on the gas pump on the gas stove, blow the moisture in the sample into the electrolytic cell, click Start Test, and after the instrument's test is completed, input the sample mass, and the moisture content of the sample can be calculated.

The parameters of the titrator are set as shown in Table 1:

Table 1.1 Parameter Settings of Coulomb Moisture Instrument:

Stirring speed：30%	destination： 100mv
Control area：400mv	Control area：25ug/min
Mixing time： 30s	Termination type: Cessation of relative drift
Electrolysis mode: Automatic	Start electrolysis current: Normal
Maximum electrolysis rate: 4.67ug/s	Minimum electrolytic rate: 0.93ug/s

Table 1.1 Parameter Settings of the Gas Stove:

Preset temperature： 120℃

Preset time： 5min

Iv. Results and Discussion

4.1 Experimental Results

The experimental results are as shown in Table 2:

Table 2 Test Results

Sample Name	Serial number	Serial number	Moisture (%)
Heavy oil	1	0.3790	0.105
Heavy oil	2	0.6940	0.099
Light oil	1	0.6143	0.150
Light oil	2	0.8040	0.132

4.2. Conclusion

The moisture content of solid crude oil samples was determined by the JH-C3 Karl Fischer moisture analyzer (Coulomb method). The data repeatability was good, met the detection standards, and could satisfy the requirements of sample detection.

References

[1] GB/T 6283-2008 Determination of Moisture Content in Chemical Products - Karl Fischer Method (General Method)

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