Oligomerization of olefins

A process for olefin oligomerization, the process comprising:

• contacting a feedstock comprising Cn and C2n olefins/paraffins under oligomerization conditions in a reactor in the presence of an oligomerization catalyst wherein the catalyst comprises a ZSM-23 catalyst having no amine treatment, wherein n is 4 and the feedstock comprises 45 wt % to 75 wt % C4 and 15 wt % to 50 wt % C8;
• forming an oligomeric product comprising C12 oligomers, wherein the C12 oligomers have a branching index of less than 2.1;
• and
• recycling at least a first portion of the oligomeric product to the reactor.