Effects of ammonium salts as additives in Rh-Ph₃PO catalytic system on hydroformylation of mixed octenes

The effects of ammonium salts as the additives in the [Rh(CH₃COO)₂]₂-Ph₃PO catalytic system on the hydroformylation of mixed octenes have been studied. The yield of isononyl aldehydes increased when an ammonium salt such as (NH₄)₆Mo₇O₂₄·4H₂O, (NH₄)₂Cr₂O₇, (NH₄)₂CrO₄ or (NH₄)₅H₅[H₂(WO₄) ₆]·H₂O was added to [Rh(CH₃COO)₂]₂-Ph₃PO-catalyzed hydroformylation of mixed octenes. The loss of rhodium in the distillation process for separating the products and the catalyst was reduced and the concentration of Rh in the distillate decreased from 0.115 to 0.057 ppm, when an ammonium salt such as (NH₄)₂CrO₄ was added into [Rh(CH₃COO)₂]₂-Ph₃PO-catalyzed hydroformylation. The stretching vibration (2040 cm^-1) of the Rh-H bond of the active species was observed in the spectra of in situ IR. The investigation of in situ IR showed that the peak intensity of Rh-H vibration increased and the temperature range at which the Rh-H vibration peak could be observed in IR was widened when (NH₄)₆Mo₇O₂₄·4H₂O was used as additive in the system [Rh(CH₃COO)₂]₂-Ph₃PO.