Butadiene Production from Butenes

The process under analysis comprises three major sections: (1) Reaction; (2) Crude Butadiene Recovery; and (3) Purification.

Reaction. Butenes feed is vaporized and mixed with steam and compressed air before being fed to the reactor. Butenes react with oxygen, forming Butadiene and water. The excess heat generated by the exothermic reaction is used to generate part of the steam fed to the reactor. The reaction product comprises Butadiene, unreacted C4s (saturated and unsaturated), reaction side products (e.g. aldehydes), as well as steam, nitrogen, unreacted oxygen and carbon dioxide.

Crude Butadiene Recovery. The Butadiene-rich mixture from the reactor is quenched with water in a quench tower. Part of the water collected from the bottom of this column (comprising the quench water and condensate) is recycled to the top of the tower. The balance is used in the aldehyde separator downstream. The overhead Butadiene-rich gas is compressed and fed to the aldehyde separator, where it is scrubbed with water from quench tower bottoms. The aldehyde-free overheads is injected in the bottom of an absorber column, where a lean oil stream absorbs hydrocarbons from the gaseous reaction product. The oil/hydrocarbon mixture is further fed to a degasser column, where light compounds are separated as overhead gas. A crude Butadiene stream is obtained after the oil is separated from the C4 mixture in a stripper column.

Purification. The crude Butadiene, which still contains butane and butenes, is then subjected to extractive distillation in the presence of N-methylpyrrolidinone (NMP) used as solvent, yielding high purity Butadiene as the final product. Butane and butenes separated from the Butadiene are sold as raffinate by-product.