A catalyst comprising A) a stationary acid component selected from the group consisting of a perfluorinated ion exchange polymer on an inert support, a silane modified perfluorosulfonic acid, and a sulfated metal oxide; and B) a mobile acid component selected from the group consisting of chlorosulfonic acid, fluorosulfonic acid, a fluorinated monosulfonic acid, a fluorinated sulfonimide, a fluorinated disulfonic acid, and an adjunct acid mixture is disclosed.