According to one embodiment described in this disclosure, a process for producing propylene may comprise at least partially metathesizing a first stream comprising at least about 10 wt. % butene to form a metathesis-reaction product, at least partially cracking the metathesis-reaction product to form a cracking-reaction product comprising propylene, and at least partially separating propylene from the cracking-reaction product to form a product stream comprising at least about 80 wt. % propylene.