Arnold Hershman

Kinetics of the catalytic vapor phase carbonylation of methanol to acetic acid

Abstract The reaction kinetics have been established for the low pressure vapor phase catalytic carbonylation of methanol to acetic acid using a solid supported rhodium complex catalyst. The catalyst is a heterogeneous analog of a previously developed homogeneous liquid phase catalyst system based upon a rhodium complex and an iodide promoter. Significantly, the reaction order dependencies are identical to those established for the liquid phase reaction (i.e., first order in iodide and independent of methanol and carbon monoxide concentrations). This suggests that in spite of the obvious physical differences between these heterogeneous and homogeneous catalysts, a similar chemical reaction mechanism is probably operative.

Mechanistic Pathways in the Catalysis of Olefin Hydrocarboxylation by Rhodium, Iridium, and Cobalt Complexes

Abstract Carboxylic acids can be synthesized by reacting olefins with carbon monoxide and water in the presence of a variety of transition transition metal catalysts: (1) Metals which have been employed as catalysts for this reaction include nickel, as first reported [1] by Reppe for the synthesis of acrylic and propionic acids from acetylene and ethylene, cobalt, iron, rhodium, ruthenium, palladium, and platinum [2]. The earlier studies of this reaction employed nickel, cobalt, and iron catalysts and required rather severe operating conditions, viz., 200-300 atm and 200-300°C. More recently the use of rhodium [3], iridium [4], platinum [5], palladium [6], and pyridine-promoted cobalt [7] catalysts has been reported. These latter systems all function at relatively mild reaction conditions (see Table 1).

Catalytic vapor phase hydroformylation of propylene over supported rhodium complexes

Abstract Recently, it has been shown that transition metal compounds such as phosphine and arsine complexes of rhodium promote hydroformylation catalysis homogenously in the liquid phase. In the present investigation, these organometallic complexes were impregnated on carbon and alumina supports and employed as solid phase catalysts for the heterogeneous vapor phase hydroformylation of propylene to butyraldehyde. Both the supported phosphine and arsine complexes exhibited good activity (30% conversion of propylene to butyraldehyde), with the phosphine complex also displaying good long-term stability as a heterogeneous catalyst. These results demonstrate that organometallic complexes can be employed as catalysts either homogeneously or heterogeneously and may, in either case, exhibit similar catalytic properties.