The effect of selective product removal in the equilibrium limited metathesis of propene was studied in a membrane enclosed catalytic reactor. Propene is converted into ethene and a-butene, the latter component is formed in cis and trans geometry. The silicalite-l membrane used in this study is able to separate trans-2-butene from propene (sel. similar to 5) and of cis-2-butene (sel. similar to 1.6). Under optimal operating conditions of the membrane enclosed catalytic reactor, the propene conversion was 13 % higher than the thermodynamic equilibrium conversion. A 34% increase in the ratio in which trans-2-butene and cis-2-butene are formed was observed. The performance of the membrane reactor was clearly a balance between the rates of reactant loss and product removal was clearly shown.