Hydrogenation and Hydrogenolysis. IX. The Hydrogenation of Benzyl Alcohol with Platinum Metal Catalysts

Abstract

The rate of the hydrogenation of benzyl alcohol with a rhodium catalyst decreases markedly in the course of the reaction, accompanied by the formation of an increasing amount of cyclohexanecarboxaldehyde with the conversion of the alcohol. The decrease in the rate is only slight with a platinum catalyst, however, and the formation of the aldehyde is much less than with the rhodium catalyst. It has been shown that cyclohexanecarboxaldehyde is an effective catalyst poison in the hydrogenation of benzyl alcohol, but that cyclohexylcarbinol is not. 1-Cyclohexenylcarbinol, an intermediate of the hydrogenation, isomerizes to cyclohexanecarboxaldehyde during the hydrogenation on rhodium and 7 : 3 rhodium-platinum catalysts to a greater extent than on the platinum catalyst. Cyclohexanecarboxaldehyde is hydrogenated only very slowly, but the rate with the platinum catalyst is about four times greater than that with the rhodium catalyst. These results may account for the different behaviors of the rhodium or 7 : 3 rhodium-platinum catalyst and the platinum catalyst observed in the hydrogenation of benzyl alcohol.

Effects of Solvents on the Hydrogenation of Mono-Aromatic Compounds Using Noble-Metal Catalysts

“…In route 1, four hydrogen atoms are introduced into benzyl alcohol, giving rise to 1-cyclohexenylmethanol. The resulting 1-cyclohexenylmethanol is then converted to cyclohexanecarbaldehyde …”

Aromatic hydrogenation of benzyl alcohol and its derivatives using compressed CO2/water as the solvent

“…It can be seen that in entry 1 in Table 1, the selectivity of cyclohexanemethanol was 94.8% at 323 K, which was significantly higher than several reported values in the previous studies. 2,3,10 This phenomenon may be explained by the less favored C-O bond cleavage, also known as hydrogenolysis, during mild temperature condition. Therefore, instead of mainly producing toluene and methylcyclohexane at high temperatures, the desired product cyclohexanemethanol could be obtained in high selectivity at mild temperatures.…”

“…Furthermore, Nishimura and Hama reported the main hydrogenation products of benzyl alcohol. 3 Their research showed that Rh catalysts could have been poisoned due to the formation of the byproduct, cyclohexanecarboxaldehyde. However, this product was not observed when using Pt catalysts.…”

Copper catalysts in the C-O hydrogenolysis of biorenewable compounds

“…Significant decarbonylation of benzaldehyde occurred, in addition to evidence of ring hydrogenation depending on the reaction conditions. 61,77 Nishimura et al used Pt and Pt-Rh catalysts in the condensed-phase hydrogenolysis and hydrogenation of benzyl alcohol at 25°C…”

“…with some additives such as acetic acid. 77 Hydrogenation of the aromatic ring followed by hydrogenolysis was the primary pathway in which several cyclohexane derivatives were formed.…”