Methanol carbonylation catalyzed by polymer-supported rhodium complexes

Abstract

Various polymer-supported rodium complexes were prepared using commercially available cation-exchange resins and chelate resins and the catalytic behaviour with respect to methanol carbonylation in the presence of methyl iodide promoter was investigated. RhCl 3 was simply loaded on functionalized chelate resins such as a polyethyleneimine type (CR-20) and a pyrrolidine type (NR 2), and on sodium-form sulphonic resins (AMNa and HPNa) by a cation-exchange method in ethanol solution. The catalysts were treated with hydrogen and/or carbon monoxide before use. Low-pressure methanol carbonylation was studied at 373–473 K in a circulating system in the ranges 6.65–25.9 kPa for carbon monoxide and 2.66–11.3 kPa for methanol with methyl iodide. A sulphonic resin-supported rhodium, Rh/AMNa, showed the highest activity and methyl acetate was produced with a maximum selectivity of 82.5%. The reaction rate observed for the CR-20-supported rhodium is approximately first order with respect to methyl iodide and carbon monoxide and 0.5 order in methanol. An IR study of Rh/CR-20 suggests that the active species of rhodium (I) -carbon monoxide is formed after carbon monoxide treatment and an X-ray photo-electron spectroscopic study of Rh/CR-20 showed the formation of rhodium (II) species after hydrogen treatment.