Process for separating C5 cuts obtained from a petroleum cracking process

A process for separating a C5 cuts obtained from a petroleum cracking process, comprising:

• 1) a light fraction-removing step, wherein C5 cuts obtained from a petroleum cracking unit is fed into the middle section of a light fraction-removing rectification column 1 for rectification, with the light fractions having 4 or less carbon atoms being obtained at the top and C5 materials being obtained at the bottom;
• 2) a heavy fraction pre-removing step, wherein the bottoms from step 1) are fed into a thermal dimerization reactor 2A where a thermal dimerization is carried out at a temperature of 60-150° C. and a pressure of 1.0-1.5 MPa, and cyclopentadiene in C5 cuts is dimerized to form dicyclopentadiene, and then the materials are fed into a heavy fraction pre-removing rectification column 2B, with dicyclopentadiene, 1,3-pentadiene and other heavy materials being obtained at the bottom, and isoprene, mono-olefins, alkanes, alkynes and cyclopentadiene being obtained at the top;
• or
• the bottoms from step 1) are fed into a heavy fraction pre-removing reaction rectification column 2 where a process of dimerization reaction and rectification separation is carried out, and cyclopentadiene in C5 cuts is dimerized to form dicyclopentadiene, with dicyclopentadiene, 1,3-pentadiene and other heavy materials being obtained at the bottom, and isoprene, mono-olefins, alkanes, alkynes, cyclopentadiene and 1,3-pentadiene being obtained at the top;
• 3) a catalytic hydrogenation step, wherein the overhead materials from step 2) are fed into a hydrogenation reactor 3 where a selective hydrogenation is carried out in the presence of a selective hydrogenation catalyst for alkynes in order to remove alkynes;
• 4) an extractive rectification step, wherein the materials from step 3) are fed into the middle section of an extractive rectification column 4 where an extractive rectification is carried out in the presence of a solvent and a polymerization inhibitor, with mono-olefins and alkanes being obtained at the top and the isoprene-rich and solvent-based materials of C5 dienes being obtained at the bottom;
• 5) a stripping step, wherein the solvent-based materials from 4) are fed into a stripping column 5;
• and
• 6) a heavy fraction-removing step, wherein the materials obtained at the top of the stripping column 5 are fed into a heavy fraction-removing reaction rectification column 6 for reaction rectification, and wherein the unreacted cyclopentadiene is dimerized to form dicyclopentadiene, with dicyclopentadiene, 1,3-pentadiene and other heavy materials being obtained at the bottom and isoprene of a polymerization grade being obtained at the top.