Mechanism of Deposit Formation: Deposit Tendency of Cracked Components by Boiling Range

In order to evaluate the deposit forming tendency produced by gasoline cracked components in vehicle intake systems, four cracked components of Venezuelan gasolines were separated into fractions by distillation ranges: IBP-55 °C, 55-110 °C, 110-150 °C, 150-190 °C and 190+ °C. A fifth low-boiling range cracked component was separated into fractions with the following distillation ranges: IBP-55 °C, 55-110 °C and 110+ °C. Sulfur, total and basic nitrogen and gum content, as well as the saturates, olefinic and aromatic contents were determined for each fraction. The fractions were also tested in an Induction System Deposit (ISD) apparatus for their deposit-forming tendency. Aromatic, sulfur, total and basic nitrogen and gum content increased with fraction distillation range for each component. Each of the total components evaluated showed a small tendency to form deposit by the ISD apparatus test method (<1.3 mg/100 ml). However, in all cases the fraction 190+ °C formed high deposit levels in ISD (>14 mg/100 ml). Contrary to the information found in the literature, comparison of the sulfur and total and basic nitrogen content with ISD deposit formation tendency for the 190+ °C fractions obtained from the different components, showed no direct correlation. The IBP-55 °C and 55-110 °C fractions did not show a deposit-forming tendency (<0.3 mg/100 ml) as measured by ISD in spite of high olefin contents (50-67% vol.) which have been reported in the literature as responsible for deposit formation. The fraction 110+ °C of the fifth cracked component (74.7% vol. olefins and 4260 ppm sulfur) showed a low tendency toward ISD formation (2.1 mg/ 100 ml).