Cis-2-Butene-1,4-Diol as Probe for Studying Hydrogenation, Hydrogenolysis and Isomerization Reactions

In this chapter a review on the hydrogenation of cis-2-butene-1,4-diol over supported metal catalysts, with particular emphasis on the different reaction mechanisms is proposed. cis-2-Butene-1,4-diol is an interesting multifunctional substrate, chosen as a probe molecule to study liquid phase hydrogenation of unsaturated diols, due its versatility to give different valuable products. Its reduction with hydrogen over supported metal catalysts, in fact, occurs through a complex reaction network, involving cis-trans and double bond isomerization, hydrogenation and hydrogenolysis reactions. The extent of formation of different products depends on the catalyst used as well as the reaction conditions. Therefore it appears of great importance to tailor a particular heterogeneous catalyst in order to address, with high selectivity, the reaction towards a desired product. Furthermore, a detailed knowledge of intrinsic kinetics of the different reactions involved is an important goal in order to understand the selectivity behaviour. The study reported is focused on understanding the effect of some parameters, like as the metal particle size, the chemical nature of the support, the partial hydrogen pressure, the role of the reaction solvent, the electronic and/or geometric peculiarities of metal, the addition of alkali and alkali earth promoters. Furthermore, an accurate kinetic investigation on the possible intimate reaction mechanism is presented.