The presently disclosed subject matter relates to methods of producing ethylene and propylene by the catalytic steam cracking of naphtha using an HZSM-5 catalyst. An example method can include providing a naphtha feedstock, providing steam, and providing an HZSM-5 catalyst. The method can further include preparing the HZSM-5 catalyst by titanium modification or alkaline treatment, followed by phosphorus modification. The method can further include feeding the naphtha feedstock and steam to a reactor containing the catalyst and removing an effluent from the reactor having a combined yield of ethylene and propylene of greater than about 45 wt-%.