2024-03-28T22:46:27Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/1910682019-09-27T10:59:38Zcom_10261_101com_10261_5col_10261_480
Pinilla-Herrero, Irene
Márquez Álvarez, Carlos
Sastre, Enrique
2019-09-19T11:51:34Z
2019-09-19T11:51:34Z
2015-06-17
5th Early Stage Researchers Workshop in Nanoscience (2015)
http://hdl.handle.net/10261/191068
The increasing demand of light olefins in the industry has renewed interest of the methanol-to-olefins process (MTO) as a route to obtain these petrochemicals from sources alternative to petroleum1 • Sorne zeolitic nanoporous silicoaluminophosphates , such as SAP0-35 , are active catalysts in the MTO process, raising selectivities to light olefins up to 80%. The main drawback of this catalyst in the MTO process is its rapid deactivation caused by the deposition of bulky molecules in the pare entrances and the externa! surface , which blocks the accessibility of the reactants to the active acid siles and the diffusion of products out of the nanopores. However, the deactivation can be restrained by modifying properly the synthesis conditions of the catalysts in arder to obtain crystals with
improved properties. Textura! properties as well as crystal size are key parameters to enhance the stability of these kind of catalysts in the MTO process2·'.
In this sense , we have used glucosamine as additive in the synthesis of SAP0-35 (framework type LEV) and found that it provokes an importan! reduction of crystal size. 11 is postulated that the crystal growth modifier effect of the glucosa mine can be triggered by the -NH2 group of the glucosamine molecules present in the synthesis gel, that can interact with SAP0-35 nuclei, surrounding them and inhibiting their growth. The synthesis of SAP0-35 under controlled conditions also favours the formation of regular cuboid crystals instead of macle ones. Furthermore, it was found that the observed outcome was strongly dependen! on the percentage of glucosamine added to the synthesis gel. Crystal size decreased rapidly as glucosamine concentration increased up to 0.5% bu!, al higher concentrations , size reduction was progressively lower as the percentage of glucosamine added to the synthesis gel increased. Thus , it was possible to obtain SAP0-35 nanoporous catalysts with a directed crystal size. As it is well known that crystal size is a key factor determining the deactivation of these catalysts in the MTO process, this method allows to obtain catalysts with improved stability under reaction conditions (Test conditions:
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Crystal growth modifier effect shown by glucosamine in the synthesis of nanoporous silicoaluminophosphate SAPO-35
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