Abstract: In order to improve the reproducibility of using conventional process to synthesize sulphonate detergents and to reduce the consumption of carbon dioxide during synthesis, a new quantitative carbon dioxide method was introduced to synthesize calcium sulphonate detergent and magnesium sulphonate detergent in laboratory. Experimental results showed the new method was not suitable for the synthesis of calcium sulphonate, but it was feasible to synthesize magnesium sulphonate. Under the conditions of an alkyl benzene sulphonate amount of 3.5 g, a xylene amount of 50 mL, a methanol amount of 3 mL, an ammonia solution amount of 1.5 mL, a carbon dioxide partial pressure of 3 MPa and a carbonation reaction time of 1 h, when the amount of active-60 magnesium oxide was 2.5 g and 3.5 g, medium alkaline magnesium sulphonate detergent with total base number (TBN) of 283 mgKOH/g and high alkaline magnesium sulphonate detergent with TBN of 339 mgKOH/g was obtained, respectively. Some amorphous magnesium carbonate existed in the detergent product as shown by FT-IR analysis.

Key words: lubricant detergent, calcium sulphonate, magnesium sulphonate, quantitative carbon dioxide