Aluminium oxynitride

Recently, amorphous high surface area vanadium aluminium oxynitrides have been reported as active catalysts for propane ammoxidation to yield acrylonitrile (AC) at atmospheric pressure. Optimal performance was achieved at 500°C using a C3Hg 02 NH3 molar ratio of 1.25 3 1 (see Tables 4 and 5). The space time yields of these catalysts have been reported to be much higher than for other catalysts reported in the literature. 

Silicon nitride, oxynitride and silicon aluminium oxynitride (SiAlON) compounds are of considerable technical interest as advanced ceramics because of their stability and chemical inertness at elevated temperatures, and their excellent mechanical properties. Si MAS NMR has proved to be useful in studying various aspects of these compounds, including their formation and structure, the processes by which they are... 

An Y NMR study has also been made of the effect of Y2O3 on the sintering of the silicon aluminium oxynitride 3-sialon, a compound structurally related to (3-Si3N4 but... 

McCauley JW, Corbin ND (1979) Phase-relations and reaction sintering of transparent cubic aluminium oxynitride spinel (AlON). J Am Ceram Soc 62 476 79... 

When shaped into crucibles AIN can be used as a container for molten aluminium. It is a good electrical insulator, the resistivity exceeding IO12 ohm. cm at 25 °C. Modulus of rupture, 250 MN/m2 at 25°C and 120 MN/m2 at 1400 °C. Hardness, 1230 (KlOO). Aluminium Oxynitride. AlON is an infrared transmitter in the wavelength range 1 to 4pm. 

Aluminium oxynitrides have been formed by reaction of aluminium tri-sec-butoxide with anhydrous hydrazine in a mixed acetonitrile/chloroform solvent. Al MAS NMR showed that the intermediate state contained AIO4, AIO5 and AlOe environments, with the final products ranging from single phase AIN to composites ofAl20s, AlON and AIN (Kim et al., 1997). 

SiAION (silicon aluminium oxynitride) ceramics for engineering applications can be synthesised from aluminosilicates by carbothermal reduction and nitridation (CRN), in which a mixture of the aluminosilicate with carbon is fired in nitrogen at 1400 C. Composites of potassium aluminosilicate geopolymers with graphite, when fired for lOhr under these conditions, have been found to produce predominantly p-SiAlON (Figure 10) by a reaction such as ... 

A novel basic support and catalyst have been prepared by activation of aluminium phosphate with ammonia. Fine control of time and temperature allows to adjust the 0/N ratio of these oxynitride solids and thus to tune the acid-base properties. The aluminophosphate oxynitrides are active in Knoevenagel condensation, but a basicity range can not yet determined. Supporting Pt or Pt/Sn on AlPONs allows to prepare catalysts that are highly active and selective in dehydrogenation reactions. 

The presence of nitrogen within the catalyst was argued to be important on the basis that the performance of a vanadium aluminium oxide catalyst was much worse (acrylonitrile per pass yield = 1.5%). The nitrogen content of the oxynitride catalyst was observed to increase with time on stream as shown in Table 5. ... 

It must also be pointed out that other basic materials have been synthesized which present no surface oxygens and hydroxyls, but other types of active sites whose exact nature remains controversial. These type of solids are, for example, impregnated imides and nitrides on zeolites and alumina, amorphous oxynitrides obtained by treatment with ammonia or aluminium orthophosphate, zirconium phosphate, aluminium vanadate or galloaluminophosphate, and KF supported on alumina/1,3,41 One of the main advantages of these solids with respect to basic oxides is their resistance to carbon dioxide or water. 

Liquid phase aldol condensation reaction between heptanal and benzaldehyde is studied over two series of oxynitride catalysts aluminium phosphate oxynitrides AlPON and mixed aluminium gallium phosphate oxynitrides AlGaPON , with increasing nitrogen contents (0-14 wt.% for AlPON and 0 - 16 wt. % for AlGaPON ). The main products are jasminaldehyde and 2-pentyl-2-nonenal. Jasminaldehyde is formed via the cross-aldol condensation reaction between heptanal and benzaldehyde and 2-pentyl-2-nonenal is formed via the self-condensation reaction of heptanal. 

The synthesis of aluminophosphate oxynitride (ALPON) was also reported (67,68). ALPONs are prepared by heating aluminium phosphate under flowing ammonia up to 1073 K. ALPONs are active for the Knoevenagel condensations of... 

Nitridation of aluminium phosphate with pure 1 3 at temperature up to 800 C allows the preparation of aluminium phosphate oxynitride AlPON. 

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