| Popis: |
The tridecameric aluminum polymer [AlO4Al12(OH)24(H2O)12]7+ is prepared by forced hydrolysis of an Al(NO3)3 solution by NaOH up to an OH:Al mol ratio of 2.2. Upon addition of sulfate the tridecamer crystallizes into macroscopic crystallites of the basic aluminum sulfate Na0.1[Al13O4(OH)24(H2O)12](SO4)3.55, which is characterized structurally by means of X-ray diffraction, 27Al solid-state magic angle spinning NMR, IR and chemically by inductively coupled plasma atomic emission Spectroscopy. The basic aluminum sulfate has a monoclinic unit cell with a = 20.188±0.045 A, b = 11.489±0.026A, c = 24.980±0.056 A, and β= 102.957±0.022°. With TG analysis, DTA and heating stage X-ray diffraction the thermal decomposition is studied. The tridecamer persists as a stable unit in the sulfate structure to temperatures of 80°C. Approximately 9 mol H2O are adsorbed in excess per one mol basic aluminum sulfate; these are easily lost by heating to 80°C. From 80 to 360°C the tridecamer unit will gradually decompose losing its 12 water and 24 hydroxyl groups, to finally become X-ray amorphous. From 360 to 950°C, with a maximum between 880 and 950°C, SO3 is removed, leaving behind primary aluminum oxide. |
