Gasoline composition

#This invention relates to gasoline compositions and their use.

#SAE Paper 922218, I. R. Galliard and J. R. F. Lillywhite, “Field Trial to Investigate the Effect of Fuel Composition and Fuel-Lubricant Interaction on Sludge Formation in Gasoline Engines”, SAE International Fuels and Lubricant Meeting and Exposition, San Francisco, Calif., USA, Oct. 19-22, 1992, describes vehicle tests on eight fuels, four of which were base fuels and four had detergent added. All of the fuels contained 0.15 g/l of lead. The four base fuels were characterised as follows:— (i) 45% v aromatics, 55% v saturates, final boiling point (FBP) 182° C., sulphur less than 50 ppmw, (ii) 53% v aromatics, 1% v olefins, 46% saturates, FBP 211° C., sulphur less than 50 ppmw, (iii) 38% v aromatics, 30% v olefins, 32% v saturates, FBP 174° C. sulphur 260 ppmw, and (iv) 31% v aromatics, 30% v olefins, 39% v saturates, FBP 208° C., sulphur 180 ppmw.

#Vehicle tests were carried out, using all eight fuels, and two different lubricants, one meeting API SF rating (low dispersant) and the other meeting API SG rating (high dispersant). In the conclusions, it is stated that there were significant fuel, lubricant and fuel-lubricant interaction effects on the propensity to form sludge in a modern gasoline engine; lubricant dispersant level is a significant parameter to control the onset of sludge formation; fuel end-point, the presence of fuel detergent, and the presence of heavy aromatic fuel components are all significant parameters in the control of sludge, with high end-point fuels having a large amount of heavy aromatic components and containing no gasoline detergent additives showing the most marked sludge formation tendencies. The trial showed no correlation between levels of sludge and levels of wear. It is also stated that no correlation was found between levels of cam wear or used oil iron levels and sludge control performance.

#Three hydrocarbon base fuel gasolines were tested. Comparative Example A was a base fuel as widely employed in fuels sold in The Netherlands in 2002. Comparative Example B corresponded to Comparative Example A with addition of heavy platformate (the higher boiling fraction of a refinery steam manufactured by reforming naphtha over a platinum catalyst), to increase aromatics. Example 1 corresponded to Comparative Example A, with addition of light cat-cracked gasoline (the lower boiling fraction of a refinery stream produced by catalytic cracking of heavier hydrocarbons), to increase olefins. Sulphur contents of the fuels were adjusted to 50 ppmw S by addition, where necessary, of dimethylsulphide, in order to eliminate possible effects arising from differences in sulphur levels.

#The resulting fuels had properties as given in Table 2:—

#TABLE 2 Comparative Comparative Base Fuel Example 1 Example A Example B Density at 15° C. 0.7216 0.7316 0.754 DIN 51757/V4 RVP (mbar) 561 512 672 Distillation (ISO 3405/88) IBP (° C.) 30 32.5 35 10% 46 49.5 54 50% 83.5 107.5 109.5 90% 143 147.5 168.5 FBP 168.5 173 205.5 S(ASTM D 2622-94) 50 50 50 (ppmw) Paraffins (% v) 52.86 64.19 53.79 Olefins (% v) 16.4 0.61 0.43 Olefins of C10 or 0.00 0.00 0.00 greater % v) Naphthenes (% v) 2.87 2.88 4.1 (saturated) Aromatics (% v) 27.01 31.41 40.74 Aromatics of C10 or 0.46 0.57 7.10 greater (% v) Oxygenates 0 0 0 RON 95.3 96.1 95.8 MON 85.3 87.7 86.6