Systems and methods for producing propylene

A process for producing propylene, the process comprising:

• introducing a first portion of a first stream comprising butene to a first reactor, where the first reactor comprises a first metathesis catalyst and a cracking catalyst, the first metathesis catalyst positioned generally upstream of the cracking catalyst;
• at least partially metathesizing the first portion of the first stream with the first metathesis catalyst to form a first metathesis-reaction product;
• at least partially cracking the first metathesis-reaction product with the cracking catalyst to produce a cracking-reaction product comprising propylene and ethylene;
• passing the cracking-reaction product out of the first reactor in a cracking-reaction product stream;
• combining a first recycle stream with a second portion of the first stream to a form a mixed stream and introducing the mixed stream to a second reactor, the second reactor comprising a second metathesis catalyst;
• at least partially metathesizing the mixed stream with the second metathesis catalyst in the second reactor to produce a second metathesis-reaction product comprising propylene and passing the second metathesis-reaction product out of the second reactor in a second metathesis-reaction product stream;
• at least partially separating ethylene from the cracking-reaction product stream, the second metathesis-reaction product stream, or a stream comprising a mixture of both, to form the first recycle stream;
• and
• at least partially separating propylene from the cracking-reaction product stream, second metathesis-reaction product stream, or a stream comprising a mixture of both, to form a product stream comprising propylene.

A process for producing propylene, the process comprising:

• introducing a first portion of a first stream comprising butene to a first reactor, where the first reactor comprises a first metathesis catalyst;
• at least partially metathesizing the first portion of the first stream with the first metathesis catalyst to form a first metathesis-reaction product;
• passing the first metathesis-reaction product to a second reactor, where the first reactor comprises a cracking catalyst;
• at least partially cracking the first metathesis-reaction product with the cracking catalyst to produce a cracking-reaction product comprising propylene and ethylene;
• passing the cracking-reaction product out of the second reactor in a cracking-reaction product stream;
• combining an ethylene recycle stream with a second portion of the first stream comprising butene to a form a mixed stream and introducing the mixed stream to a third reactor, the third reactor comprising a second metathesis catalyst;
• at least partially metathesizing the mixed stream with the second metathesis catalyst in the third reactor to produce a second metathesis-reaction product comprising propylene and passing the second metathesis-reaction product out of the third reactor in a second metathesis-reaction product stream;
• at least partially separating ethylene from the cracking-reaction product stream, the second metathesis-reaction product stream, or a stream comprising a mixture of both, to form the ethylene recycle stream;
• and
• at least partially separating propylene from the cracking-reaction product stream, the second metathesis-reaction product stream, or a stream comprising a mixture of both, to form a product stream comprising propylene.