Recovery of rhodium from hydroformylation reaction product

Claim 1

In a process for hydroformylating an alkene of 2 to about 10 carbon atoms having a double bond in the alpha position by (a) reacting said alkene at about 80° C. to 150° C. with carbon monoxide and hydrogen in the presence of a liquid reaction medium containing as hydroformylation catalyst a complex of rhodium with triphenylphosphine and carbon monoxide to produce a liquid reaction mixture comprising triphenylphosphine, an aldehyde derivative of said alkene having one carbon atom more than said alkene, and reaction by-products; (b) stripping said liquid reaction mixture by gas stripping, distillation, or evaporation during the course of said hydroformylation reaction to remove overhead from said reaction mixture a vapor stream comprising said aldehyde derivative, (c) recovering a crude product condensate comprising said aldehyde derivative from said vapor stream, and (d) distilling the bulk of the aldehyde out of said condensate leaving behind a crude reaction heavy ends mixture, the improvement which comprises: separating said crude reaction heavy ends mixture by distillation into an aldehyde product distillate comprising said aldehyde derivative and a first distillation residue comprising substantially the entirety of those components of said reaction heavy ends mixture which are less volatile than said aldehyde derivative; and redistilling said first distillation residue to separate said first distillation residue into (1) a redistillation overhead stream comprising those components of the crude reaction heavy ends mixture which are more volatile than triphenylphosphine and (2) a redistillation residue stream comprising those components of the crude reaction heavy ends mixture which are equal to or lower than triphenylphosphine in volatility and including any rhodium moiety initially contained in said vapor stream.