Effect of morphology and acidity control of Ni-SAPO-34 zeolite on catalytic performance of dimethyl ether to olefins
SAPO-34 molecular sieve is one of the main catalysts for DMTO reaction and shows excellent catalytic performance. In this work, a series of Ni-SAPO-34 molecular sieve with different crystal morphologies , such as cubic, melting angle cube , spherical, polygon cube, were synthesized using Ni-DETA as a structure-directing agent. We explored the influence of Ni-DETA structure-directing agent on the formation of crystal morphology, and found that the different morphology is related to the amount of Ni-DETA introduced, and also had an impact on the acidity of the Ni-SAPO-34 molecular sieve. The properties of these samples were characterized by SEM, XRD , EDS, UV–Vis, FT-IR, NH 3 -TPD and N 2 physicalsorption. The synthesized polygonal cubic Ni-SAPO-34 molecular sieve has lower strong acidity due to the introduction of a small amount of nickel, which is beneficial to reduce the production of carbon deposits and improve the catalytic reaction activity. Moreover, the multi-edge morphology and hierarchical porous structure are also advantageous to the catalytic reaction. The polygon cube Ni-SAPO-34 catalysts display the highest DTO catalytic performance, and the total selectivity of ethylene and propylene can reach 83.76%.
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