Process for separating alkylation product, alkylation reaction and separation process, and related apparatus

A process for separating an alkylation product, comprising:

• introducing a liquid phase alkylation product from an alkylation reaction unit into a first heat-exchanger as a cold stream to exchange heat with a vapor phase stream from a column top of a high-pressure fractionating column, wherein the liquid phase alkylation product is pressurized using a pressure pump or not pressurized;
• introducing the liquid phase alkylation product exiting from the first heat-exchanger into a second heat-exchanger as a cold stream;
• heating the liquid phase alkylation product in the second heat-exchanger and further heated to 100° C.;
• introducing the liquid phase alkylation product exiting from the second heat-exchanger into the high-pressure fractionating column for fractionation under a condition of 2.0 MPa-6.0 MPa;
• introducing the vapor phase stream from the column top of the high-pressure fractionating column into the first heat-exchanger as a hot stream;
• introducing a liquid phase stream from a column bottom of the high-pressure fractionating column into a low-pressure fractionating column for fractionation under a condition of 0.2 MPa-1.0 MPa,
• obtaining a low-carbon alkane from the column top of the low-pressure fractionating column, and a liquid phase stream from the column bottom of the low-pressure fractionating column as an alkylation oil product, and
• heating a material stream from the low-pressure fractionating column as a cold stream in an inter-reboiler using at least a part of the vapor phase stream from the column top of the high-pressure fractionating column exiting from first heat-exchanger as a hot stream;
• and
• feeding the heated material stream from the inter-reboiler to the low-pressure fractionating column.