Method for producing propylene oligomer

A method for producing a propylene oligomer, comprising:

• isomerizing an oligomer comprising a propylene trimer, a propylene tetramer, or a mixture thereof at less than the critical pressure of propylene in the presence of at least one member selected from a group consisting of a catalyst comprising phosphoric acid.

A propylene oligomer, comprising a propylene tetramer having a 4,6,6-trimethyl-3-nonene concentration of 30% by mass or more.

A method for producing a propylene oligomer, comprising:

• oligomerizing propylene in the presence of a catalyst comprising a crystalline molecular sieve,
• wherein when a BET specific surface area of the crystalline molecular sieve, as obtained by a nitrogen adsorption method, is taken as “a” [m2/g], and a micropore specific surface area of the crystalline molecular sieve, as obtained by subjecting an adsorption isotherm measured by a nitrogen adsorption method to analysis in accordance with a t-plot method, is taken as “b” [m2/g], a/b is 1.8 or less.