A deuterium-labeling study on the dehydrogenation of 2-propanol with Ru-Pt/carbon catalyst in the liquid-film state effective for the 2-propanol/acetone/hydrogen chemical heat-pump systems

A unique feature of the dehydrogenation of 2-propanol with Ru-Pt/carbon catalyst in the liquid-him state has been elucidated by means of various kinds of deuterium labeling. A quite large kinetic isotope effect for 2-propanold(8) (k(H)/k(D) = 14.6) suggests that fission of the methine C-H bond in the isopropoxy intermediate is rate-determining in the overall process. The dominant formation of Hz for 2-propanol-O-d(1) is explained in terms of rapid scrambling of deuterium together with a large kinetic isotope effect for fission of the methine C-D bond. This picture is supported by both the absence of an appreciable kinetic isotope effect for 2-propanol-O-d(1) and the deuterium distribution among the liquid-phase components. The extent of hydrogen transfer from 2-propanol to acetone-d(6) during the dehydrogenation reaction suggests suppression of the inhibitive adsorption of acetone, leading to a high catalytic activity in the region of high acetone concentration, which is essential for a 2-propanol/acetone/hydrogen chemical heat-pump system with high thermal efficiency.