Rhodium catalysed hydroformylation of higher alkenes using amphiphilic ligands: Part 2

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• 作者：Buhling ; A. ; Kamer ; P.C.J. ; Van Leeuwen ; P.W.N.M. ; Elgersma ; J.W.
• 关键词：Alkenes ; Hydroformylation ; Phosphine derivatives ; Rhodium ; Water-soluble triarylphosphines ; Catalyst recovery
• 刊名：Journal of Molecular Catalysis A: Chemical
• 出版年：1997
• 出版时间：February 24, 1997
• 年：1997
• 卷：116
• 期：1-2
• 页码：297-308
• 全文大小：867 K

文摘

The performance of a new rhodium recycling system is described using a series of amphiphilic ligands: Ph₂ArP (Ar=S-hydroxyphenyl, 4-carboxyphenyl), Ph_nAr_3−nP (Ar = 4-PhCH₂X, X = NEt₂, NMePh, NPh₂; n = 1-2) and Ph_nAr_3−nP (Ar = 3-pyridyl, 4-pyridyl; n = 1-2). The corresponding rhodium complexes are active in the hydroformylation of oct-1-ene and can be separated from the product aldehydes by acidic or basic extraction into water. After neutralisation of the aqueous phase the rhodium phosphine species can be extracted into a new batch of oct-1-ene, with toluene as organic solvent. The pH-depending distribution characteristics of the free ligands have been determined. PhAr₂P with Ar = 4-PhCH₂NEt₂ and Ar = 3-pyridyl were completely extracted from a solution in Et₂O or toluene into a H₂SO₄-solution of pH 3 and 2, respectively. Recycling experiments with the former ligand demonstrated that the catalytically active rhodium hydrides decompose during the acidic extraction step. The structure of the recovered rhodium complexes could not be elucidated by NMR- and IR-analysis. Rhodium measurements by ICP-AES established that rhodium was quantitatively recycled. Pressurising the recovered rhodium and excess ligand to 20 bar syngas at 80°C resulted in regeneration of the original, catalytically active species. A retention of catalytic activity up to 87 % was achieved.