One-Pot Sequential Aldol Condensation and Hydrogenation of n-Butyraldehyde to 2-Ethylhexanol

2-Ethylhexanol (2EHO) is an important organic chemical. The industrial production of 2EHO comprises three units: propylene hydroformylation to n-butyraldehyde, n-butyraldehyde self-condensation to 2-ethyl-2-hexenal (2E2H), and 2E2H hydrogenation to 2EHO. In the present work, 2EHO was synthesized by one-pot sequential aldol Condensation and hydrogenation of n-butyraldehyde. Among a series of metal solid acid bifunctional catalysts, Ni/La-Al2O3 showed a better catalytic performance. The effect of reaction conditions on the one-pot sequential synthesis of 2EHO catalyzed by Ni/La-Al2O3 was investigated, and the suitable reaction conditions were obtained as follows: weight percentage of Ni/La-Al2O3 = 15%, self-condensation reaction conducted at 180 degrees C fot 8 h, and then hydrogenation reaction conducted at 180 degrees C fot 6 h under 4 MPa H-2 pressure. Under the above reaction conditions, n-butyraldehyde conversion attained 100% at a 2EHO selectivity of 67.0%. The inhibition of Ni to n-butyraldehyde self condensation reaction is responsible for the low selectivity of 2EHO. On the basis of the analysis of the reaction system, some side reactions in the one-pot sequential synthesis of 2EHO were proposed. The deactivation of Ni/La-Al2O3 was due to the agglomeration of Ni and La2O3 particles and the occurrence of gamma-Al2O3 hydration. Introduction of some hydrophobic groups on the surface of gamma-Al2O3 could effectively inhibit the hydration of gamma-Al2O3.