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- Author or Editor: M. Selim x
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Abstract
The thermal decompositions of pure and mixed manganese carbonate and ammonium molybdate tetrahydrate in molar ratios of 3:1, 1:1 and1:3 were studied by DTA and TG techniques. The prepared mixed solid samples were calcined in air at 500, 750 or 1000C and then investigated by means of an XRD technique. The results revealed that manganese carbonate decomposed in the range 300–1000C, within termediate formation of MnO2, Mn2O3 andMn3O4. Ammonium molybdate tetrahydrate first lost its water of crystallization on heating, and then decomposed, yielding water and ammonia. At 340C,MoO3 was the final product, which melts at 790C. The thermal treatment of the mixed solids at 500, 750 or 1000C led to solid-solid interactions between the produced oxides, with the formation of manganese molybdate. At 1000C, Mn2O3 and MoO3 were detected, due to the mutual stabilization effect of these oxides at this temperature.
Abstract
Different Nd-zeolites were prepared from the original NaX and NaY zeolites by ion exchange. The hydrated and thermally activated (at 550 °C) samples obtained were irradiated with 
-rays of 1.5 and 10.0 Mrad. The unirradiated and irradiated samples were characterized mainly by X-ray diffraction and tested for catalytic activity in cumene cracking. The X-ray diffraction patterns indicated a slight decrease of crystallinity after irradiation. However, the irradiated samples exhibited higher catalytic activities than unirradiated ones. -Irradiated hydrated zeolites were found to possess comparable activities, whereas the irradiated dehydrated samples were more active. Higher irradiation doses resulted in more active dehydrated zeolites than those irradiated with a lower dose. The observed higher activity was attributed to the formation of tricoordinate aluminium atoms in the zeolite structure, leading to increase of the number of acidic sites and consequently to a catalytic activity.
