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2025

Determination of the alkalinity of vehicle urea by fully automatic potentiometric titration

I. Preface

At present, with the increasing requirements for the environment, environmental protection departments in various countries have proposed to further reduce nitrogen oxide pollutants emitted by diesel engines. Engine manufacturers have begun to use SCR technology, and vehicle urea is a necessary consumable for this technology. The function of vehicle urea is to reduce nitrogen oxides in vehicle exhaust and lower emission pollution. To enhance the environmental friendliness of vehicles, the market for vehicle urea has emerged accordingly. In this experiment, the JH-T7 fully automatic potentiometric titrator of Shanghai Jiahang was used. According to the national standard GB/T 29518-2013 "Determination Method of Alkalinity in Urea Water Solution of Nitrogen Oxide Reducing Agent for Diesel Engine", the alkalinity of the urea water solution produced by a certain manufacturer was detected to determine whether it met the standard.

Ii. Instruments and Reagents

2.1 Instruments

JH-T7 fully automatic potentiometric titrator, composite PH electrode, analytical balance, etc

2.2 Reagents

0.1mol/L hydrochloric acid standard titration solution, deionized water, buffer solutions with PH values of 4.01, 6.86 and 9.18

Iii. Experimental Methods

3.1 Experimental Process

1) Preparation: Preparation process: Calibrate the PH electrode with buffer solutions of PH=4.01, 6.86, and 9.18.

2) Accurately weigh 2g of the sample (accurate to 0.0001g) into the titration cup using the weight loss weighing method, and add 100mL of deionized water. Place it on the titration table, start the pre-edited method, titrate with the calibrated hydrochloric acid titrant until PH=5.7, and conduct a blank experiment at the same time.

3.2 Instrument Parameters

The parameter Settings of the JH-T7 fully automatic potentiometric titrator are shown in Table 1:

Table 1 Parameter Settings of Titrator

Iv.

Titration type: Endpoint Titration		method name: Determination of alkalinity of Vehicle urea
Burette volume: 10mL		Sample measurement unit: g
Working electrode: Composite PH electrode		Reference electrode: None
Stirring speed: 50%		. Pre-stirring time: 5 seconds
Fast drop volume: 0.02mL		slow drop volume: 0.02mL
Fast drop equilibrium time: 2 seconds		Fast drop equilibrium potential: 1mv
Slow drop equilibrium time: 4		4 Slow drop equilibrium potential: 1mv
Each addition volume: 0.02mL		Final volume: 20mL
Potential leap: 500		Correlation coefficient: 1
Titrant name: Hydrochloric acid		Titrant name: Hydrochloric acid \ n
Endpoint value: PH < 5.7.		Delay time: 10 seconds

4.1 Experimental Results

The samples were tested and the experimental results are shown in Table 2:

Table 2 Alkalinity Test Results

Sample name	sampling quantity (g)	c(HCl)/mo l/L	sample volume V1/mL	Alkalinity (%)	Average value (%)	RSD(%)
1#	2.04809	0.10042	0.320	0.0267	0.0266	0.2669
	2.18898		0.340	0.0266
	2.18898		0.340	0.0266
2#	2.08242		0.379	0.0311	0.0311	2.7363
2#	2.08709		0.370	0.0303	0.0311	2.7363

	2.08970	0.369	0.0320
3#	2.05486	0.320	0.0266	0.0269	1.316
	2.0680	0.330	0.0273
	2.0352	0.320	0.0269
4#	2.3808	0.268	0.0193	0.0191	1.047
	2.0638	0.228	0.0189
	2.0354	0.227	0.0191

4.3. Conclusion

In this test, the content of alkalinity in the urea aqueous solution was determined by the automatic potentiometric titrator. The test result was less than 0.2%, which met the requirements of the national standard GB/T 29518-2013 for the alkalinity of urea aqueous solution as a nitrogen oxide reducing agent for diesel engines. Moreover, the use of instruments for judgment reduces human errors and greatly improves the accuracy of the experiment. Potentiometric titration is a good choice for detecting the content of this type of samples.

Keyword:

fully automatic potentiometric titration

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