BACKGROUND: 2-ethylhexanol (2EHO) is an important organic chemical, which is mainly used in the manufacture of plasticizers. At present, the industrial manufacture of 2EHO is generally carried out by gas-phase hydrogenation of 2-ethyl-2-hexenal, which has high energy consumption. So it is of significance to study liquid-phase hydrogenation of 2-ethyl-2-hexenal. RESULTS: Several byproducts were found such as 3-methylheptane, 2-ethylhexyl butyrate, 2,4-diethyloctanol, 2,4-diethyloctanal, 5,7-diethylundecane and 2-ethylhexyl-2-ethylhexanoate in the reaction system of 2-ethyl-2-hexenal liquid-phase hydrogenation catalyzed by Ni/gamma-Al2O3 and a reaction network was proposed. The C=C bond of 2-ethyl-2-hexenal molecule was hydrogenated prior to the C=O bond hydrogenation and furthermore the C=O bond was hardly hydrogenated until the C=C bond hydrogenation finished. The kinetics of liquid-phase hydrogenation of 2-ethyl-2-hexenal catalyzed by Ni/gamma-Al2O3 was studied and the result demonstrated that both 2-ethyl-2-hexenal hydrogenation to 2-ethylhexanal (C=C bond hydrogenation) and 2-ethylhexanal hydrogenation to 2-ethylhexanol (C=O bond hydrogenation) were first-order irreversible reactions. CONCLUSIONS: It is made clear by means of online infrared analysis that the hydrogenation of C=O bond is difficult to achieve before C=Ompletion of the hydrogenation of C=C bond. The 2-ethylhexanal hydrogenation reaction, whose activation energy is higher, is the rate-determining step in the entire hydrogenation process. (C) 2017 Society of Chemical Industry