22 structure and morphology the xrd spectra of the ht

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Unformatted text preview: 900°C. 3.2.2. Structure and morphology The XRD spectra of the HT precursors calcined at 900°C are presented in Figure 13 and the spectra of Ni10 calcined at various temperatures in Figure 14. The analysis 3. Results and discussion - catalyst preparation and characterisation 80 ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp was performed analogously to the coprecipitated solids. The spectra of the calcined catalysts were carefully compared to the complete diffraction patterns of the following compounds (again the JCPDS catalogue numbers are given in squared brackets): MgO (periclase) [04-0829] NiO (bunsenite) [04-0835] Mg0.4Ni0.6O [34-0410] MgNiO2 [03-0999] MgAl2O4 [21-1152] NiAl2O4 [10-3339] Al2O3 [13-0373] Al2O3 [34-0493] Mg6Al2(OH)16CO3· 4H2O (hydrotalcite) [41-1428] Ni6Al2(OH)16CO3· H2O (takovite) [15-0087] The comparison showed that the HTs calcined at 900°C consist of well crystallised divalent metal oxide and spinel phases. Depending on the composition various spinel phases (e.g. MgAl2O4, NiAl2O4) and various divalent metal oxide phases (MgxNi1-xO) with periclase or bunsenite structure and could be formed. As bunsenite is the Ni derivative of periclase these divalent metal oxide phases will be referred to in the following as divalent metal oxide phases with periclase structure. In case of Ni5C900 also hydrotalcite-type phase was detected, which is attributed to partially surfacial reconstruction. 81 3. Results and discussion - catalyst preparation and characterisation D D,S D H,T S H,T S S S S Ni72C900 intensity [a.u.] Ni50C900 Ni30C900 Ni15C900 Ni10C900 Ni5C900 Ni0C900 0 10 20 30 40 2Q 50 60 70 80 Fig. 13 XRD spectra of the catalysts calcined at 900°C (D = divalent metal oxide phase with periclase structure, S = spinel phase, H = hydrotalcite-type phase, T = takovite-type phase) 3. Results and discussion - catalyst preparation and characterisation 82 The XRD spectra of Ni10 calcined at the different temperatures reveal that at temperatures • ƒ& WKH FDWDO\VWV FRQVLVW RI ZHOO FU\VWDOOLVHG VSLQHO SKDVHV DQG divalent metal oxide phases with periclase structure. Upon...
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This document was uploaded on 10/07/2013.

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