Olefin oligomerization

A process for producing a hydrocarbon composition, said process consisting essentially of:

• a. contacting a feed stream and an olefinic recycle stream with a molecular sieve catalyst in a reaction zone under olefin oligomerization conditions to produce an oligomerization effluent stream, wherein said feed stream comprises at least one C3 to C8 olefin and said olefinic recycle stream comprises a first olefinic recycle stream and no more than about 10 wt % of C10+ non-normal olefins;
• b. separating said oligomerization effluent stream to produce a first olefinic stream and a first hydrocarbon product stream comprising jet fuel and diesel fuel, wherein said first hydrocarbon product stream comprises at least about 1 wt % and no more than about 30 wt % of C9 non-normal olefin and said first olefinic stream has a weight ratio of C4−/(C5-C8) molecules from about 0.8 to about 1.2 times the weight ratio of C4−(C5-C8) molecules found in said oligomerization effluent stream;
• and
• c. splitting said first olefinic stream to produce said first olefinic recycle stream and a first purge stream.