Exchanged lanthanum in InHMOR and its impact on the catalytic performance of InHMOR. Spectroscopic, volumetric and microscopic studies

Abstract

The incorporation of lanthanum by ion exchange into InHMordenite was studied in order to investigate the modification of the physicochemical properties of the InHM catalysts. The prepared solids, LaInHM and InHM, were treated under rigorous reaction conditions, i.e. 25 h of TOS with addition of 10% of water and 500 C. The structural changes of the catalysts were followed by spectroscopic, volumetric and microscopic studies. The presence of lanthanum in the InHM acts like a protection for the zeolite structure avoiding the formation of EFAl species, but the alteration of the indium environment into the matrix leads to a reduction of the catalytic yield of the InHM catalyst. In fact the XPS results revealed that the concentration of the indium active sites (InO)þ in LaInHM is lower than in the InHM catalyst, while the remaining indium species interact strongly with Lanthanum. After the reaction, a decrease of In active site in the LaInHM catalyst was observed, suggesting a closer interaction IneLa which was later corroborated by TEM microscopy. On the other hand, a steric factor between the side channels of the mordenite and the hydrated cation of La during the exchange process locates lanthanum in outer position, with the consequent loss of pore volume and area specific. The lanthanum exchanged ions protect the deactivation process by structure collapse, but negatively affect the activity of the InHM catalyst.