MOTOR GASOLINE GUIDE
Gasoline was initially discarded
Edwin Drake dug the first oil well in Pennsylvania in 1859 and distilled the oil to produce kerosene for lighting. Although other petroleum products, including gasoline, were also produced in the distillation process, Drake had no use for the gasoline and other products, so he discarded them. It wasn’t until 1892, with the invention of the automobile, that gasoline was recognized as a valuable fuel. By 1920, 9 million vehicles powered by gasoline were on the road, and service stations selling gasoline were opening around the country. Today, gasoline is the fuel for nearly all light-duty vehicles in the United States. Gasoline is a fuel made from crude oil and other petroleum liquids. Gasoline is mainly used as an engine fuel in vehicles. Petroleum refineries and blending facilities produce motor gasoline for sale at retail gasoline fueling stations. Most of the gasoline that petroleum refineries produce is actually unfinished gasoline (or gasoline blendstocks). Gasoline blendstocks require blending with other liquids to make finished motor gasoline, which meets the basic requirements for fuel that is suitable for use in spark ignition engines.
Gasoline is a complex mixture of hydrocarbons and other chemical compounds used as fuel for spark-ignition internal combustion engines, primarily in light duty transportation vehicles (LDV).
The gasoline octane rating measures its ability to withstand pre-ignition during compression in an engine cylinder. Gasoline octane is a critical factor in engine design. Engine performance and efficiency increase with increasing compression ratio. Engines with higher compression ratios require gasolines with higher octane ratings. In the United States, the posted gasoline octane rating is the average of two different testing methods, the Research Octane Number (RON) and the Motor Octane Number (MON). The average is referred to as the Anti-Knock Index (AKI). Most U.S. LDV are designed for regular, 87 AKI gasoline. Approximately 10% of vehicles require or recommend premium gasoline (91 AKI or higher).
To burn, liquid gasoline must be vaporized and mixed with oxygen (air). Since gasoline is a blend of hundreds of molecules with different characteristics, gasoline boils (vaporizes) over a range of temperatures and must be blended in a way that vaporization will occur over the entire
range of engine operating temperatures. Several specifications measure and control the vaporization performance of gasoline:
- Reid Vapor Pressure (RVP)
Drivability Index (DI)
Vapor-Liquid Ratio (V/L)
The EPA also sets limits on the sulfur and benzene content of finished gasoline. Other industry specifications limit the tendency and ability of the gasoline blend to foul, damage, or corrode gasoline storage facilities as well as components of the vehicles combustion and exhaust systems. These specifications include Gum, Oxidation Stability, Color, NACE Corrosion, and Phosphorous.
U.S. petroleum refineries produce some finished motor gasoline. However, most finished motor gasoline sold in the United States is actually produced at blending terminals, where gasoline blendstocks, finished gasoline, and fuel ethanol are blended to produce finished motor gasoline in different grades and formulations for consumer use. Some companies also have detergents and other additives blended into gasoline before delivery to retail outlets. Blending terminals are more numerous and widely dispersed than petroleum refineries, and they have equipment for filling tanker trucks that transport finished motor gasoline to retail outlets. Most of the finished motor gasoline now sold in the United States contains about 10% fuel ethanol by volume. Ethanol is added to gasoline mainly to meet the requirements of the Renewable Fuel Standard, which is intended to reduce greenhouse gas emissions and the amount of oil that the United States imports from other countries.
Gasoline varies by grade – Three main grades of gasoline are sold at retail gasoline refueling stations:
Some companies have different names for these grades of gasoline, such as unleaded, super, or super premium, but they all indicate the octane rating, which reflects the antiknock properties of gasoline. Higher octane ratings result in higher prices. Before 1996, lead was added to gasoline as a lubricant to reduce wear on engine valves. Leaded gasoline was completely phased out of the U.S. fuel system by 1996. Manufacturers recommend the grade of gasoline for use in each model of a vehicle.
Gasoline also varies by formulation
In addition to the different grades of motor gasoline, the formulation of gasoline may differ depending on the location where it is sold or the season of the year. Federal and state air pollution control programs that aim to reduce carbon monoxide, smog, and air toxins require oxygenated, reformulated, and low-volatility gasoline. Some areas of the country are required to use specially formulated gasoline to reduce certain emissions, and the formulation may change during winter and summer months. These area-specific requirements mean that gasoline is not a homogenous product nationwide. Gasoline produced for sale in one area of the United States might not be authorized for sale in another area. The characteristics of the gasoline depend on the type of crude oil that is used and the setup of the refinery where the gasoline is produced. Gasoline characteristics are also affected by other ingredients that may be included in the blend, such as ethanol. Most motor gasoline sold in the United States contains some fuel ethanol.
Gasoline octane and lead levels increased over time
By the 1950s, cars were becoming bigger and faster. Gasoline octane increased, and lead was added to improve engine performance.
Leaded gasoline was eventually taken off the U.S. market
Unleaded gasoline was introduced in the 1970s when health problems from lead became apparent. In the United States, leaded gasoline for use in on-road vehicles was completely phased out as of January 1, 1996. Most other countries have also stopped using leaded gasoline in vehicles. Retail gasoline is now usually sold in three grades of gasoline.
Ethanol is added to gasoline
In 2005, the U.S. Congress enacted a Renewable Fuel Standard (RFS) that set minimum requirements for the use of renewable fuels, including ethanol, in motor fuels. In 2007, the RFS targets were set to rise steadily to 36 billion gallons by 2022. In 2018, about 14.4 billion gallons of fuel ethanol were consumed in the United States. In most areas of the country, retail motor gasoline is about 10% ethanol by volume.
The worldwide refining industry has undergone a major transformation in the last decade due to changes in regulatory and market forces, such as fluctuating crude prices, tighter regulation on product quality and refinery emissions, shifting crude quality and fundamental changes in fuel demands. These forces can be seen clearly in the North American market, where crude quality has become heavier due to increasing amounts of lower-cost heavy, sour Canadian bitumen and where regulations have become more severe by limiting the sulphur level in fuels to 15 wppm in diesel and 30 wppm in gasoline. In addition to these feed and product quality changes, the overall demand for transportation fuels is shifting from a traditionally gasoline-oriented to an increasingly diesel-oriented market.
Regulatory specifications for the gasoline and diesel pool, which are constantly evolving, have been in the forefront of refiners’ challenges in the last 10 years. In particular, the gasoline sulphur and benzene regulations have been the main drivers for the recent remodelling of the refinery configuration. This transformation has been seen all around the world, but particularly in Europe, Asia and North America. Other countries are following the trend and a common worldwide gasoline sulphur specification is on the horizon. Indeed, the overall gasoline sulphur content is likely to level off at 10 ppm across the globe. As a consequence, most refiners will face renewed challenges to be able to meet the new ultra-low-sulphur gasoline (ULSG) specifications. However, in view of other market forces, there may also be new opportunities for refiners.
Gasoline sulphur regulation
There has been a steady downward trend in the sulphur content of fuels to reduce emissions from cars and trucks. Many countries mandated the production of low-sulphur gasoline (LSG) some time ago, but in recent years regulations in Western Europe, some Asian countries and California in the US have brought in even tighter specifications to lower the gasoline sulphur to 10 ppm.
The different regional approaches to the gasoline sulphur specification set out in Table 1 show a clear trend towards ULSG. Other countries are following the same path to either meet their domestic regulatory specifications or be able to export and sell on the international ULSG market (see Figure 1).
Although the majority of countries still have gasoline sulphur specifications well above 10 ppm, the overall trend clearly shows that in the near future ULSG production will become the norm worldwide.
Current refinery configuration
Refinery configurations vary widely, depending on crude availability, local demand, export markets and regulatory constraints. In the same way, each market has its own set of dynamics and means of complying with the new fuel regulations.
In Europe, regulations for ULSG were adopted early and somewhat influenced by a market demand, which is more heavily skewed toward diesel than gasoline. The options for ULSG compliance were influenced by:
• Processing of relatively light and low-sulphur crude oil
• Relatively good-quality FCC feed (little cracked gas oil such as heavy coker gas oil)
• Undercutting of FCC gasoline to maximise diesel production.
The EU’s 10 ppm ULSG is produced mainly by using moderate severity FCC post-treatment.
Many catalytic feed hydrotreater (CFHT) units installed in Asian refineries were designed to meet modern fuels and emission regulations. As such, many are designed for high desulphurisation levels to meet refinery and SOx regulations from the FCC flue gas, resulting in low-sulphur FCC gasoline. Consequently, most refineries in Japan have met the new ULSG limit of 10 ppm by adding low-severity post-treatment units.
In the US, the refinery configuration was influenced by a large demand for gasoline coupled with limited fuel oil outlets, resulting in the installation of bottom-of-the barrel conversion units and high FCC feed sulphur. The US Tier 2 gasoline sulphur and California Air Resources Board (CARB) regulations led to a sharp increase in the number of FCC feed pretreatment and FCC gasoline post-treatment units over a short period of time (see Figure 2). Essentially, all of the US refineries now have pre- and/or post-treatment units to ensure compliance with gasoline sulphur regulations.
FCC pretreatment vs post-treatment
When the Tier 2 regulations were proposed, many were convinced that CFHT would be the solution of choice due to the resulting large improvement in FCC performance. However, the high capital cost requirement for the FCC pretreatment option coupled with low refinery margins resulted in the wide application of FCC post-treatment to reduce gasoline sulphur.
Another factor that can influence the decision between pretreatment and post-treatment is FCC flue gas emissions. Limits on refinery emissions and in particular those from the FCC have led to refinery-specific regulation via consent decrees with the EPA, resulting in much lower SOx and NOx emissions. The “preferred” refinery configuration may well have been different had the limits on emissions and product sulphur been regulated in concert.
More recently, there has been an important trend towards the processing of increasingly heavier crudes, in particular heavy Canadian crude or bitumen. By 2015, there is an expected increase of about 2 million b/d of Canadian bitumen, which will be largely exported to the US as raw bitumen (DilBit) or synthetic bitumen (SynBit) after partial upgrading at the production site. These very heavy crudes are a challenge for processing in existing refinery assets due to a high acid content (TAN), high aromaticity and low hydrogen content, along with very high contaminant content: sulphur, nitrogen, Conradson carbon and metals.