A composition, a process for producing the composition, and a hydrocarbon conversion process for converting a hydrocarbon stream such as, for example, gasoline, to olefins and C.sub.6 to C.sub.8 aromatic hydrocarbons such as toluene and xylenes are disclosed. The composition comprises a silylated catalyst which comprises a zeolite, a clay or silica, and a promoter. The process for producing the composition comprises the steps: (1) combining a zeolite with a clay or silica and a promoter under a condition sufficient to bind the clay to the zeolite to produce a clay-bound zeolite; (2) heating the clay-bound zeolite to produce a modified zeolite; and (3) silylating the modified zeolite with a silylating agent. The hydrocarbon conversion process comprises contacting a hydrocarbon stream with the catalyst composition under a condition sufficient to effect the conversion of a hydrocarbon to an olefin and a C.sub.6 to C.sub.8 aromatic hydrocarbon.