Formation and Properties of Ni–Ce–La–O Catalysts of Reforming

Abstract

In order to stabilize in the support matrix highly dispersed nickel forms of the active component, which are characterized by thermal stability and high resistance to carbonization under conditions of hydrocarbon raw material reforming, the synthesis of Ni–Ce–La–O catalysts was carried out with varying composition (La/Ce = 0, 0.25, 1, 4), the preparation technique (the method of polymer ester precursors and incipient-wetness impregnation) and the calcination temperature (300–900°C) of the samples. The patterns in the formation of materials are studied and a comparative study of the physicochemical properties of materials by a complex of methods (low-temperature nitrogen adsorption, X-ray phase analysis, Raman spectroscopy, transmission electron microscopy, and temperature-programmed reduction with hydrogen) is carried out. It is shown that at La : Ce = 0–4, the materials after calcination at 300–500°C are solid solutions based on ceria (Ni–Ce–La–O, Ce–La–O) with deposited nickel oxide particles. Compared with impregnation, the method of polymer ester precursors provides a higher specific surface area and the defect structure of material, a smaller average crystallite size of the solid solution, and nickel stabilization mainly in the composition of a ceria-based solid solution. After high-temperature calcination at 700–900°C, the differences in the textural and structural characteristics of the catalysts prepared by different methods become less pronounced, which is due to the partial destruction of the Ni–Ce–La–O solid solution. It is found that an increase in the dispersion and thermal stability of the Ni-containing phase and a decrease in the degree of carbonization of the Ni–Ce–La–O catalysts in the ethanol autothermal reforming is achieved by increasing the La : Ce molar ratio and using the method of polymer ester precursors for the synthesis.