NOVELTY - Separating and purifying isobutene, butane and butylenes, comprises passing mixed 4C raw material into a decarbonization tower (13), selecting out 3C elements (14) from a top part of the tower, passing 5C elements into the tower and followed by passing the mixed 4C component into an isobutene tower, adding recycling solvent in the isobutene tower, extracting isobutene from a top part of the isobutene tower and followed by obtaining the recycled solvent from the stripper kettle, splitting the recycled solvent, and passing the obtained recycled solvent into the isobutene and butane towers.    USE - The method is useful for separating and purifying isobutene, butane and butylenes.    ADVANTAGE - The method separates and purifies the isobutene, butane and butylenes with reduced energy consumption in a cost-effective manner.    DETAILED DESCRIPTION - Separating and purifying isobutene, butane and butylenes, comprises: (a) passing mixed 4C raw material into a decarbonization tower (13), and selecting out 3C elements (14) from a top part of the decarbonization tower; (b) passing the 5C elements into the decarbonization tower after performing the process in the decarbonization 3C tower, and selecting out 5C elements from a 5C tower kettle; (c) selecting out mixed 4C component from a top part of the 5C tower kettle, passing the mixed 4C component into an isobutene tower, adding recycling solvent in the isobutene tower, extracting isobutene from a top part of the isobutene tower, selecting out the produced isobutene in the kettle, and directly passing the isobutene into a middle part of a butane tower (1); (d) adding a recycled solvent into the butane tower, obtaining butane from a top part of the butane tower, selecting out the produced butane in the kettle, and passing the obtained butane into a stripper; and (e) obtaining butylenes from a top part of the stripper, obtaining the recycled solvent from the stripper kettle, splitting the recycled solvent, and passing the obtained recycled solvent into the isobutene tower and the butane tower.    DESCRIPTION OF DRAWING(S) - The figure shows a flow diagram of a method for separating and purifying isobutene, butane and butylenes.    Butane tower (1)    decarbonization tower (13)    3C elements (14)    Decarbonization 3C tower kettle (15)    Decarbonization 5C tower. (17)