Disclosed is a method for forming HFO-1234ze, and for forming compositions comprising HFO-1234ze, by (a) converting, preferably by dehydrofluorination, pentafluorpropane (HFC-245), preferably 1,1,1,3,3-pentafluorpropane (HFC-245fa), preferably by contact with a caustic solution, to a reaction product comprising cis-HFO-1234ze and trans-HFO-1234ze; and (b) contacting at least a portion, preferably substantially portion, and in certain embodiments substantially all of said reaction product with at least one isomerization catalyst to convert at least a portion, and preferably at least a substantial portion, of cis-HFO-1234ze in said reaction product to trans-HFO-1234ze.