Abstract: A method for dimerizing an olefin, which comprises dimerizing an olefin in the presence of a catalyst, wherein a nickel compound, an organic aluminum compound and a phosphite compound of the formula (I): ##STR1## wherein each of R.sup.1 and R.sup.2 which may be the same or different, is a hydrocarbon group, each of R.sup.3 to R.sup.8 which may be the same or different, is a substituent containing no oxygen atom, or a hydrogen atom, W is a substituted or unsubstituted aromatic hydrocarbon group, and x is 0 or 1, are used as the catalyst.

Abstract: The present invention is directed to a method of dimerizing lower olefins which comprises dimerizing a lower olefins in the presence of a catalyst, wherein the catalyst used comprises a nickel compound, an organic aluminum compound, and a phosphite compound having the general formula (I): ##STR1## wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are phenyl groups optionally substituted by substituents and may be different from each other, at least two of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 have a hydrocarbon group as a substituent in the ortho position; A is a divalent aliphatic, alicyclic or aromatic hydrocarbon group which optionally has a substituent; and n is 0 or 1. The present invention is also directed a method of producing alcohol by means of hydroformylating and hydrogenating the newly formed olefins obtained through the said dimerization method of the lower olefins.

Abstract: A method for dimerizing an n-butene wherein a catalyst system is used which is produced in situ from an organonickel compound having no nickel-halogen bond, a triarylphosphine and/or a monoalkyldiarylphosphine, an organoaluminum compound and hydrogen. The resulting octenes are excellent as a raw material of alcohols for a plasticizer, and an excellent plasticizer can be obtained from alcohols having 9 carbon atoms produced by using the octenes.