Identification of amorphous and crystalline phases in alumina entity and their contribution to the properties of the palladium catalyst

Abstract

© 2019 Elsevier B.V. The purpose of this paper is to identify the phase inhomogeneity, undetectable by X-ray method, and the reason for its occurrence in the composition of aluminum oxide. It is shown that even a trace amount of carbon (0.23 wt%) in the precursor of aluminum oxide can cause a high content of amorphous phase (38%). Carbon is present due to the products of incomplete hydrolysis of the aluminum alkoxides (alumoxanes) in the commercial sample of boehmite. The fact that the amorphous and crystalline phases in the composition of aluminum oxide differ in reactivity under hydrothermal treatment is first described. It is shown in a split endothermic peak on the differential scanning calorimetry curve. It is investigated that the brief hydrothermal treatment of the phase-inhomogeneous aluminum oxide and its subsequent calcination lead to formation of a defective structure with greater acidity in the composition of the aluminum oxide. This aluminum oxide was used as a support of the palladium catalyst in the 1,3-butadiene hydrogenation. This catalyst showed higher selectivity to 1-butene and low selectivity to butane, compared to the catalyst on alumina with amorphous phase.