substantially all of the oligomer product is less than c 8 with nonenes and higher olefins being negligible n butenes are not detrimental to the present process and are relatively unreactive at the preferred temperature of 90 u00b0 100 u00b0 c further isobutene is preferred because a cut can be made incorporating the isobutene with propylene while leaving the n butenes with the pentenes for alkylation feedstock the pressure of the present reaction system is not critical however it must be sufficient to maintain the reactants in liquid phase during the reaction and as set out above the presence of the isobutene and other c 4 39 s reduces the pressure required to maintain the liquid phase the catalysts useful for the present invention are preferably in the macroreticular form which has surface areas of from 20 to 600 square meters per gram catalysts suitable for the present process preferably are cation exchangers which contain sulfonic acid groups and which have been obtained by polymerization or copolymerization of aromatic vinyl compounds followed by sulfonation examples of aromatic vinyl compounds suitable for preparing polymers or copolymers are styrene vinyl toluene vinyl naphthalene vinyl ethylbenzene methyl styrene vinyl chlorobenzene and vinyl xylene a variety of methods may be used for preparing these polymers for example polymerization alone or in admixture with other monovinyl compounds or by crosslinking with polyvinyl compounds for example with divinyl benzenes divinyl toluenes divinylphenylethers and others the polymers may be prepared in the presence or absence of solvents or dispersing agents and various polymerization initiators may be used e g inorganic or organic peroxides persulfates etc the sulfonic acid group may be introduced into these vinyl aromatic polymers.