Coprecipitated nickel–alumina catalysts for methanation at high temperature. Part 2.—Variation of total and metallic areas as a function of sample composition and method of pretreatment

Abstract

Resplts are presented for the total and metallic nickel areas of a series of coprecipitated nickel-alumina catalysts prepared and pretreated in different ways. The total areas of the samples decrease on reduction and with increasing reduction temperature, while the nickel area increases with reduction temperature. Increasing calcination temperature causes a decrease in total and nickel areas, this being particularly marked at high temperatures of calcination. A model for the catalyst system is proposed, based on these results and on complementary structural investigations. The high stability of the catalysts is attributed to the presence in the unreduced catalyst of nickel oxide rich phases containing dissolved aluminium ions; on reduction, alumina crystallises on the surface of the growing nickel crystallites, preventing sintering of the catalysts except under extreme conditions.

Ni–Al layered double hydroxides as catalyst precursors for CO2 removal by methanation

“…A general explanation of the obtained TPR results is searched in the models proposed for decomposition and reduction of the LDH compounds [60,[73][74][75].…”

“…In a series of articles [57][58][59][60][61] Kruissink et al have claimed that a thermal treatment of co-precipitated Ni-Al precursors of Ni 2? /Al 3?…”

Natural gas reforming and CO2 mitigation

“…In collaboration with the group of L.L. van Reijen in Delft (The Netherlands) [5][6][7], we examined factors determining the behaviour of the co-precipitated catalysts, showing that the nature of the precipitates formed (hydrotalcites, with characteristic and well-defined layer structures) determined the subsequent behaviours of the catalysts. We then went on to develop a novel catalyst that combined the advantages of the high activities of the CRG catalysts with the mechanical stabilities imparted by a-alumina [8,9].…”

Supported nickel catalyst from hydroxycarbonate of nickel and aluminium

“…1000 K), a series of metastable phases forms. The views on the nature of these phases, published in literature, differ; the NiA1CO3-HTlc, calcined at temperatures of up to 873 K, is most probably composed of two dispersed phases [2]. Consequently, the NiO phase contains dissolved aluminium ions while that of aluminium oxide has dissolved nickel ions.…”