Abstract
The sintering of a coprecipitated nickel alumina catalyst, calcined at 450, 600 and 900°C, was studied in a 70hydrogen/30% steam gas flow at a temperature of 700°C and a pressure of 1 bar. The phase composition of the fresh and sintered catalysts was determined by X-ray diffraction. Hydrogen chemisorption, X-ray line broadening, methanation activity determinations and BET surface area measurements were used to monitor the sintering of the catalysts. The results indicate a rather high sinter stability of the catalyst. During the initial sintering stage there is a parallel decrease of nickel surface area and total surface area. After 60 hours of sintering the nickel crystallite size reaches a constant level, while the total surface area decreases still further. There is no influence of the calcination temperature up to 900°C on the equilibrium nickel crystallite sizes of the sintered catalysts. To explain these results a new model of coprecipitated nickel alumina catalysts is proposed.
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