Butyraldehyde from Propylene and Syngas (N/Iso Ratio of 30:1)

The process under analysis comprises the following major sections: (1) hydroformylation; (2) catalyst recovery and (3) purification.

* Hydroformylation. Fresh propylene and syngas are treated to remove impurities that could poison the rhodium catalyst employed in the hydroformylation reaction. The purified raw materials, recycled reactants and recycled catalyst solution are fed to the first of two reactors operating in series. In both reactors, the propylene reacts with carbon monoxide and hydrogen at mild temperatures and low pressures, and in the presence of a homogeneous rhodium-based catalyst with an organophosphite ligand, yielding n-Butyraldehyde as main product and isobutyraldehyde by-product. The catalyst is dissolved in the high-boiling reaction by-products.

* Catalyst recovery. The liquid effluent from the hydroformylation, containing catalyst components, reaction products, unreacted propylene, as well as aldehyde products with some dissolved gases, is depressurized and fed to a falling-film evaporator. The concentrated catalyst solution obtained from evaporator is recycled to the hydroformylation area, with a small portion directed to a catalyst regeneration step. The vapor from evaporator is partially condensed and the uncondensed gas is recycled to the reactor through a compressor. The condensed liquid stream is sent to the purification steps.

* Purification. The condensed liquid stream containing the aldehydes from the catalyst recovery is directed to the first of three distillation columns for the purification of n-Butyraldehyde product. In the first column, the stabilizer column, remaining traces of dissolved gases are removed (propylene, propane, and other inert gases) and recycled to the hydroformylation. The bottom stream from the stabilizer column is fed to a second distillation column, where isobutyraldehyde is separated. In the third column, the heavy-ends column, heavies impurities are separated from the n-Butyraldehyde product (with 99 wt% purity), which is finally routed to storage facilities located outside battery limits.