Disclosed are processes for the conversion of isomerizable halogenated C2-C6 olefins from one geometric form to a more preferred geometric form. Preferred process aspects involve converting C2-C6 olefin in a cis-form to a trans-form under conditions effective to convert at least about 50 percent, and even more preferably at least about 70 percent, of the cis-form compound to the trans-form compound. In preferred embodiments the C2-C6 olefin comprises tetrafluoropropene, with cis-1,3,3,3 tetrafluoropropene (cis-HFO-1234ze) being converted, preferably at high conversion rates and high selectivity, to trans-1,3,3,3 tetrafluoropropene (trans-HFO-1234ze). In preferred embodiments the conditions effective to achieve the desired high levels of conversion and selectivity include exposing the feed to a metal based catalyst selected from the group consisting of halogentated metal oxides, Lewis acid metal halides, zero-valent metals, and combinations of these, preferably under reaction conditions, including reaction temperature and residence time, effective to convert at least about 5% of the cis-form of the compound to other compounds and to further achieve a selectivity to the trans-form of the compound of at least about 70%.