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Reformulated Gasoline
During late 1980s, in several large US cities the ambient air quality could not meet the prescribed limits for CO and ozone even after enforcement of the then stringent vehicle emission standards. The US Clean Air Act Amendments of 1990 therefore, legislated additional measures besides further tightening of the emission standards. Five organic compounds called ‘Air Toxics’ were identified for control through fuel quality modifications. These toxic substances emitted through exhaust and fuel evaporation are: benzene, formaldehyde, acetaldehyde, 1, 3 butadiene and ‘polycyclic organic matter’ (POM).
Gasoline quality was proposed to be modified for introduction in the big cities that did not meet the ambient air carbon monoxide and ozone standards. This modified gasoline was called ‘reformulated gasoline (RFG)’. The RFG programme in the USA was implemented in two phases as given in Table 8.7.
| Table 8.7 |
| Performance Targets of US Reformulated Gasoline Programme |
| RFG Programme |
Performance Target |
| Phase 1(Started on Jan 1, 1995) |
15 to 17% reduction in both the exhaust and evaporative emissions of volatile organic compounds (VOC) and air toxics compared to 1990 industry average gasoline. NOx however, must not increase above the 1990 gasoline. |
Phase 2(Started on Jan 1, 2000) |
25-29% reduction in VOC, 17-20% reduction in air toxic emissions and 5 to 7% reduction in NOx |
The RFG is basically a gasoline containing oxygenates for reduction in CO and through control of volatility and composition to reduce VOC and ‘Air toxics’. All the reformulated gasolines were required to contain a minimum of 2 % by mass (m/m) oxygen and a maximum of 1% by volume (v/v) benzene. The RFG must not contain heavy metals. Further, their average T90, sulphur, and olefins contents must not be higher than the 1990 average gasoline. Typical properties of Phase 1 and Phase 2 RFG are shown in Table 8.8
| Table 8.8 |
| Characteristics of Typical US Reformulated Gasoline |
| Properties |
Phase 1- RFG |
Phase 2- RFG |
| Aromatics, %v/v |
23.4 |
25.4 |
| Olefins, %v/v |
8.2 |
4.1 |
| Benzene, %v/v |
1.3 |
0.93 |
RVP, kPa, Summer |
50 |
46 |
| Winter |
79 |
- |
| T50, ºC |
94 |
94 |
| T90, ºC |
158 |
145 |
| Sulphur, mass ppm |
305 |
31 |
MTBE, %v/v |
11 |
11.2 |
Ethanol, % v/v |
4 |
0 |
Oxygen , % mass |
2.0 – 2.7 |
2.0 – 2.7 |
| Heavy metals |
Not permitted |
Not permitted |
| Detergent Additives |
Compulsory |
Compulsory |
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