This proposal looks at the reactivity of propene in a commercial ZSM-5 zeolite catalyst. It builds on a previous INS study (on TOSCA) which showed that propene in this catalyst at room temperature forms long chain oligomeric carbenium cations. We will examine what happens to these oligomers when heated to higher temperatures, and what happens when propene is directly admitted to the catalyst at higher temperatures. The measurements will provide understanding of the role of olefin oligomers in the catalytic conversion of methanol to hydrocarbons, and in the conversion of olefins to middle distillate, which are both commercial processes utilising this catalyst.