Ruthenium carbonyl iodide catalysts esters

In a more detailed examination of the ruthenium-cobalt-iodide "melt" catalyst system, we have followed the generation of acetic acid and its acetate esters as a function of catalyst composition and certain operating parameters, and examined the spectral properties of these reaction products, particularly with regard to the presence of identifiable metal carbonyl species. 

Data in Table V illustrate the production of acetic acid from 1/1 syngas. A variety of ruthenium-containing precursors - coupled with cobalt halide, carbonate and carbonyl compounds - at different initial Co/Ru atomic ratios, have been found to yield the desired carboxylic acid when dispersed in tetrabutylphosphonium bromide. In a more detailed examination of the ruthenium-cobalt-iodide melt catalyst system, we have followed the generation of acetic acid and its acetate esters as a function of catalyst composition and certain operating parameters, and examined the spectral properties of these reaction products, particularly with regard to the presence of identifiable metal carbonyl species. 

Monometallic ruthenium, bimetallic cobalt-ruthenium and rhodium-ruthenium catalysts coupled with iodide promoters have been recognized as the most active and selective systems for the hydrogenation steps of homologation processes (carbonylation + hydrogenation) of oxygenated substrates alcohols, ethers, esters and carboxylic acids (1,2). 

Suitable catalysts for this type of process must be capable of hydrogenating both carboxylic acids and their esters to alcohols, but also of carbonylating these compounds to their homologous acids. The best catalytic systems known contain either Rh or Ru in the presence of iodide. Ruthenium iodide systems are the most active ones in the hydrogenation reaction, but suffer from low activity in the carbonylation step, whereas rhodium iodide systems are very active when carbonylating alcohols to their acids (cf. Section 2.1.2.1). 

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