Active centers of rare-earth zirconate catalysts for the vapor-phase dehydration of alkanediols

• Vapor-phase dehydration of seven alkanedions was catalyzed by rare-earth zirconate. • Active centers are base-acid pair sites induced by the oxygen vacancies. • Catalytic activity of zirconate was proportional to the pair site concentration. • The trend of reactivity of alkanediols was identical irrespective of RE type. • The C-chain, OH location, and methyl branching influence alkanediol reactivity. The active center of rare-earth (RE) zirconate catalysts for the dehydration of seven alkanediols, such as 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,4-pentanediol, 3-methyl-1,3-butanediol, and 2-methyl-2,4-pentanediol, was systematically unveiled. The correlation between the formation rate of dehydration products, i.e., unsaturated alcohols (UOLs), and their acid-base properties, corroborated by the poisoning experiments of the active centers, suggests that the active site for the dehydration of these alkanediols is a base-acid pair site. These sites were formed by the generation of oxygen vacancies resulting from the incorporation of RE into the ZrO 2 lattice structure. We also demonstrated that the same active site served as the active center for the dehydration of different alkanediols, regardless of the carbon chain length, the position of OH groups, or the presence or absence of methyl branching. Using the established active sites, it is also possible to calculate the turnover frequency for each alkanediol.