The deactivation of silico-aluminophosphate catalysts during methanol conversion reactions

[摘要] This dissertation focusses on the deactivation of SAP0-34 and modified SAPOsduring methanol conversion under various conditions, in comparison to H-ZSM-5.SAPO-34 was found to deactivate rapidly during methanol conversdon. This wasshown by the decrease in activity, surface area and pore volume of thecatalyst. The deposited coke was analysed by in situ diffuse reflectanceinfra-red Fourier Transform spectroscopy,solid-state magic angle spinningnuclear magnetic resonance, gas chromatography mass spectroscopy (GCMS) of theHF- and dichloromethane-extracted to coke; and GCMS of the organic specfesreleased during regeneration of the catalyst and trapped in resin capillaryinlet tubes.The coke consisted of alkylated aromatics and naphthaleneswhich probably formed on the surface or in the large cavities of SAPO-34.The amount of coke deposited during methanol conversion increased withreaction temperature, decreased with dilution of the methanol with water ornitrogen. and decreased with increased pressure, Incorporation of Ni into theSAPO framework did not decrease the rate of deactivation, but the coke thatHas deposited was less bulky than that deposited in SAPO-34. Modification ofthe SAPO-34 with trlmethyl silylchloride decreased the rate at deactivationof the catalyst.

[发布机构] University of the Witwatersrand