CO2 - METHANOL REFORMING REACTION OVER ALUMINA-SUPPORTED an‎d UNSUPPORTED KEGGIN-TYPE HETEROPOLY COMPOUNDS

The prepared alumina-supported and unsupported Keggin-type heteropoly compounds (HPC), H3 PW12O40and Na3PW12O40, were characterized by means of IR, XRD and TGA. The effect of alumina as a supporton the catalytic behaviour of these compounds was tested in the carbon dioxide-methanol reaction. The unsupported heteropoly compounds were also tests for comparison reasons. Results showed that the unsupported and the alumina-supported H3PW12O40.13H2O are more active than their sodium salts. Forthe alumina-supported heteropoly compounds (HPC), it has been observed that, besides methyl formate(MF), formaldehyde (HCHO) and dimethyl ether (DME), the formation of dimethyle carbonate (DMC) was noticed. It was found that increasing the loading of heteropolyacid increases the conversion and varies the selectivities, whereas increasing the loading of the alkali salt decreases the conversion but novariations in selectivities were observed. The DMC formation observed only on the supported catalysts,seems to indicate that the formation of this later, requires both Lewis-acid and redox sites. Bronsted-sitesreduce the DMC formation in favour of DME.