Process for manufacturing olefins

I. Field of the Invention A catalyst and an improved process for producing olefins by catalytic naphtha cracking are described. The process provides relatively higher yields over a commercially important range of naphtha conversion, while providing about the same or lower yields of aromatics and methane over the range. In the process, a hydrocarbon naphtha feedstock including a hydrocarbon having about three to about twenty carbon atoms per molecule is passed into a reactor containing a pentasil zeolite catalyst. The catalyst includes about 0.1 to about 10 weight percent phosphorus and about 0.1 to about 10 weight percent of a promoter metal selected from the group consisting of gallium, germanium, tin and mixtures thereof. The hydrocarbon may be passed into the reactor together with a diluent selected from the group consisting of steam, nitrogen, methane, and ethane and mixtures thereof. Alternatively, the hydrocarbon may be passed into the reactor together with additional propane.