Significance of integration of normal butane isomerization with alkylation for gasoline blending

In an overseas refinery where MTBE is forbidden to be blended into gasoline and some gasoline specifications are more stringent than Euro-Ⅴ specifications in target market,the gasoline octane number,aromatics and RVP are off-specifications. Therefore,the clean blending components of high octane and low RVP are required to improve the gasoline quality,and alkylate is a satisfactory selection based upon experience.The study by the designers has found that the operation of a large alkylation unit can improve the gasoline quality. As the MTBE is forbidden in the project and MTBE is in surplus supply an integration process of normal butane isomerization and alkylation is recommended to increase the production of high-octane alkylate. The mixed C4s and unreacted normal butanes from alkylation unit are sent to isomerization unit for treatment to increase the iso-butane production so as to raise the paraffin to olefin ratio. The implementation of this process has greatly improved the product gasoline quality. The octane number of gasoline is increased by 0. 59,aromatic content is decreased by 7. 23% and vapor pressure is lowered by 1. 86 kPa.