Optimized Blending of Butane in Gasoline

Gasoline is composed of a mixture of different refinery process streams obtained from the FCC naphtha, catalytic reformate, alkylated, and isomerate. Each of these components is composed of the overall physical properties that are characteristic of gasoline. The physical properties of gasoline must comply with the required specification, according to the regulations and standards that are mandatory in the countries of consumption.

Seasonal Variations in Reid Vapor Pressure (RVP)

Most properties have constant values throughout the whole year, except the Reid Vapor Pressure (RVP), which depends on the environmental temperature and differs between summer and winter seasons. In the summer the RVP that is required for a car engine, has already achieved vapor pressure resulting from of partial pressure of each of the above gasoline components. However, in winter periods, and cold climates, the volatility of these components is insufficient to provide the requested RVP.

Role of Butane in Gasoline Blending

Butane is a low-valued product that is obtained from the distillation of crude oils.

This, in combination with its high vapor pressure, makes butane extremely attractive to increase the RVP, especially during the cold seasons. It is the target of each gasoline blender to maximize the amount of butane incorporated in the gasoline mixture, and by that to reduce the cost of the blend, without affecting other physical properties, such as knock properties.

The platform to achieve this goal lies in on-line process analyzers that measure continuously multiple physical properties such as the RVP, RON, and MON, preferably by one single analyzer, such as NIR process analyzers. The measured analytical data is processed to continuously calculate the ratio between butane and other gasoline components that will provide gasoline with the required specification.