A facile synthesis route for modifying the catalytic performance of SAPO-18 in MTO process
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In present work, a crystalline hierarchical SAPO-18 was synthesized using polyethylene glycol (PEG) as a cheap mesopore-directing agent to improve the catalytic performance in the methanol-to-olefin (MTO) process. The samples were characterized by XRD, FESEM, BET and NH3-TPD analysis. The effect of PEG on the morphology, crystal size and crystallization time of catalyst was studied. The mesoporosity was tuned by varying the average molecular weight of PEG. Also, the influence of PEG MW on the textural and physicochemical properties of hierarchical SAPO-18 was investigated. Finally, the catalytic behavior of all the synthesized samples was evaluated for the MTO process at 698 K and atmospheric pressure with a feed WHSV of 2 h−1 in a fixed bed reactor. It was found that the presence of the multimodal pores in the SAPO-18 structure results in an increase of about 10 % in the light olefin selectivity. Micro-mesoporous SAPO-18 prepared by PEG4000 exhibited a high selectivity of 94 % to light olefins with a good stability of 12 h and the methanol conversion of 100 %.