Method for producing of 2,3-dimethylbutene-1 and 2,3-dimethylbutene-2

A method for producing 2,3-dimethylbutene-1 and 2,3-dimethylbutene-2, comprising the steps of

• (a) dimerizing propylene in a propylene-dimerization step using a nickel complex catalyst as described below as a propylene-dimerization catalyst having propylene-dimerization activity and 2,3 dimethylbutene-1 selectivity,
• (b) rectifying the resulting reaction solution to obtain 2,3-dimethylbutene-1 as a distillate and a distillation residue containing 2,3-dimethylbutene-1 in a 2,3-dimethylbutene-1 distillation step,
• (c) allowing the distillation residue to contact with sulfuric acid, sulfonic acid or hetetopolyacid to isomerize 2,3-dimethylbutene-1 in said distillation residue into 2,3-dimethylbutene-2 in an isomerization step, and
• (d) rectifying the resulting isomerization reaction solution to obtain 2,3-dimethylbutene-2 in a 2,3-dimethylbutene-2 distillation step,
• wherein said nickel complex catalyst comprising
• (A) at least one nickel compound selected from a nickel salt of an organic or inorganic acid and a complex compound of nickel,
• (B) a trialkylaluminum,
• (C) a trivalent phosphorus compound of formula (1):
• PR1R2R3 (1)
• wherein, R1, R2 and R3 are the same or different and independently represent a phenyl group which may be substituted with an alkyl or alkoxy group, an alkyl group, a cycloalkyl group or an aralkyl group,
• (D) a fluorinated isopropanol or a halogenated phenol of formula (2):
• wherein X1 to X5 are the same or different and independently represent a halogen or hydrogen atom and at lease one of X1 to X5 is a halogen atom, and
• (E) at least one sulfur compound selected from a sulfonic acid and a dialkylsulfuric acid.