TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Process: The naphtha feed has initial and final boiling points of 0-230 degreesC and a sulfur content of less than 1 ppm.Ring opening is carried out at 150-400 (225-350)degreesC, 0-3,000 (100-800) psig, liquid hourly space velocity (LHSV) 0.1-10 (0.5-5) v/v/hour and hydrogen treat gas rate 500-10,000 (500-3,000) standard cubic feet per barrel (scf/b).The product preferably contains at least 90 wt.% normal paraffins which may then be contacted with a catalytic cracking catalyst to form a product containing olefins.Cracking is performed at 400-750 (500-750)degreesC, 0-45 psig and catalyst-to-oil ratio 4-9:1.The product contains about 10-25 wt.% each of ethylene and propylene and 0-20 wt.% of aromatics.The ethylene and propylene may be separated and polymerized.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The ring-opening catalyst contains ruthenium, rhodium, iridium and/or platinum and may be supported on an inorganic refractory oxide (e.g. alumina). It preferably contains 0.3-2.0 wt.% Ir and 0.001-2.0 wt.% of Pt (especially), Ru and/or Rh.The ring-opening catalyst also includes alkali or alkaline earth metal(s), especially barium.The cracking catalyst is a large or medium pore zeolite (e.g. ZSM-5). EXAMPLE - A 3/8 inch diameter stainless steel reactor was charged with (i) 4 g of a 0.9 wt.% Ir/Al2O3 catalyst and (ii) a guard bed comprising a mixture of 0.5 g of a Pt/Al2O3 catalyst (0.6 Pt:Al2O3) and 1 g of a ZnO sorbent. A light virgin naphtha feed containing 0.5 ppm S was passed though the reactor (guard bed first) operating at 240 degreesC, 400 psig, 2000 scf/b H2 and 0.5 w/h/w. The feed contained 30 wt.% isoparaffins, 44 wt.% n-paraffins, 22.5 wt.% naphthenes and 2.7 wt.% aromatics. The ring-opened product contained 45.8 wt.% isoparaffins, 53.6 wt.% n-paraffins, 0.6 wt.% naphthenes and 0.0 wt.% aromatics. The C4+ yield was 95 wt.%, the methane yield was 0.7 wt.% and the ring conversion was more than 95%.