Abstract: Acid number of petroleum and petroleum products was determined by catalytic thermometric titration, and various factors that might affect the test results were investigated, including particle size of paraformaldehyde, amount of paraformaldehyde, titration rate, filter factor, ambient temperature, solvent blank and so on. The results show that when particle size of paraformaldehyde is less than 75 μm, titration rate is 2 mL/min, filter factor is 45, the data precision is better when the blank value of solvent is taken into account. The environmental temperature and amount of paraformaldehyde have little influence on the results of titration analysis. In addition, a simple and feasible method for determine solvent blank value was developed.

Key words: catalytic thermometric titration, acid number, petroleum product, paraformaldehyde