The composition of the solids matches well with the

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Unformatted text preview: n and phase composition is presented in Table 9. The composition of the solids matches well with the idealised formula found in the literature for synthetic Ni/Mg/Al solids of hydrotalcite-type structure [6, 33, 42, 43, 46]: [(Ni+Mg)1-xAlx(OH)2][(NO3)y(CO3)(x-y)/2]· 0.5H2O, with x = 0.25-0.33 and y ≤ x 77 3. Results and discussion - catalyst preparation and characterisation Ni72 Ni50 weight loss [a.u.] Ni30 Ni15 Ni10 Ni5 Ni0 0 200 400 600 temperature [°C] 800 Fig. 11 TG profiles (black) and DTG profiles (grey) of the coprecipitated solids 1000 1200 78 3. Results and discussion - catalyst preparation and characterisation Ni72 -dq/dt [a.u.] ENDO Ni50 Ni30 Ni15 Ni10 Ni5 Ni0 0 200 Fig. 12 DSC thermograms of the coprecipitated solids 400 temperature 600 79 3. Results and discussion - catalyst preparation and characterisation Tab. 9: Formula and structure of the coprecipitated solids Sample Chemical composition Structure Ni0 [Mg0.720Al0.280(OH)2][(NO3)0.121(CO3)0.079] 0.52 H2O hydrotalcite Ni5 [Ni0.050Mg0.660Al0.290(OH)2][(NO3)0.131(CO3)0.080]· 0.61 H2O hydrotalcite Ni10 [Ni0.094Mg0.616Al0.291(OH)2][(NO3)0.149(CO3)0.071]· 0.50 H2O hydrotalcite Ni15 [Ni0.157Mg0.558Al0.285(OH)2][(NO3)0.141(CO3)0.072]· 0.57 H2O hydrotalcite Ni30 [Ni0.301Mg0.418Al0.281(OH)2][(NO3)0.109(CO3)0.086]· 0.44 H2O hydrotalcite Ni50 [Ni0.503Mg0.214Al0.283(OH)2][(NO3)0.164(CO3)0.059]· 0.52 H2O hydrotalcite, takovite Ni72 [Ni0.732Al0.268(OH)2][(NO3)0.121(CO3)0.073]· 0.36 H2O takovite 3.2. Catalysts 3.2.1. Preparation For the use as catalysts the prepared HTs were transformed into mixed metal oxide catalysts by calcination at 900°C. The HT Ni10 was also calcined at different temperatures (700, 800, 900 and 1000°C) to study the influence of the calcination temperature on the catalytic behaviour of the final catalyst. In the following the catalysts will be denoted according to their metal atom percentage of Ni and their calcination temperature, e.g. Ni10C900: catalyst precursor Ni10 calcined at...
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This document was uploaded on 10/07/2013.

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