Abstract: The base number serves as a critical performance indicator for lubricants and additives. To address the limitations associated with current standard methods, a catalytic thermometric titration method was developed. Experimental results demonstrated that isobutyl vinyl ether significantly enhanced the sensitivity of endpoint indication. When xylene-acetic acid (at a volume ration of 2∶1) was employed as the solvent, 0.2 mL of catalytic indicator was used, and the titration rate was maintained at 1.0 mL/min, the recovery rates for calcium dodecylbenzenesulfonate ranged from 90.5% to 105.7%. The determination results for nine out of ten typical lubricants met the reproducibility requirements specified in the existing standard method. The established method enhances environmental compatibility, reduces maintenance operations, and shortens analysis time while ensuring analytical and is applicable to most lubricating oil samples, thereby offering a robust and efficient alternative for the determination of base number in lubricants.

Key words: base number, catalytic thermometric titration, lubricant, petroleum product