Abstract: Isomerization of normal paraffins to form branched paraffins may be complicated by significant cracking of C7+ paraffins under isomerization reaction conditions. This issue may complicate upgrading of hydrocarbon feeds having significant quantities of heavier normal paraffins. Cracking selectivity may be decreased by combining one or more naphthenic compounds with a feed mixture comprising at least one C7+ normal paraffin and/or by utilizing tungstated zirconium catalysts having decreased tungsten loading. Further, C5 and C6 normal paraffins may undergo isomerization in the presence of C7+ normal paraffins.