Abstract
Poly( N-vinyl-2-pyrrolidone)(PVP) protected rhodium colloid (Rh-PVP) was used as a catalyst for methanol carbonylation under elevated temperature (140°C) and high pressure (5.4 MPa). The activity of Rh-PVP colloid catalyst increased while recycled for 6 times totally lasting 56.5 h. During the reaction, the catalyst was still in a colloidal state verified by TEM observation. XPS and IR studies of the catalyst demonstrated that colloidal rhodium metal particles partially changed to [Rh(CO) 2I 2] − under the reaction conditions. The rhodium ions in the reaction mixture amounted to 29% of the total charged rhodium after 13 h carbonylation. An additional XPS investigation of the catalyst was carried out; the results showed that oxidative addition of methyl iodide to rhodium colloid caused the transformation of rhodium species from Rh 0 to Rh 1+.
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