Enhanced catalytic performance of copper-exchanged SAPO-34 molecular sieve in methanol-to-olefin reaction.
Methanol-to-olefin (MTO) reaction over copper-exchanged SAPO-34 catalysts was investigated in order to extend their catalyst life. The exchange of copper ions into the cages of an SAPO-34 molecular sieve was confirmed by ESR, XPS, and 129Xe NMR techniques. Copper ions located in its cages considerably reduced its deactivation rate in the MTO reaction, while those dispersed on the external surface of the SAPO-34 molecular sieve accelerated the deactivation due to the limited mass transfer through the pore entrances. The 13C NMR and UV-VIS spectroscopy investigations of the materials occluded on the copper-exchanged SAPO-34 catalysts during the MTO reaction clearly showed that the copper ions exchanged in the cages suppressed the further condensation of alkyl aromatics to large, fused polycyclic aromatic hydrocarbons (PAHs). Theoretical calculations for the SAPO-34 and copper-exchanged SAPO-34 molecular sieves supported this observation because copper ions located in the cages stabilized the alkyl aromatics. Therefore, the exchange of copper ions into the SAPO-34 molecular sieve stabilized the reactive intermediates, alkyl aromatics, of the MTO reaction and suppressed their further condensation to PAHs, thereby slowing the deactivation.
Kim
Sun Jung
SJ
School of Applied Chemical Engineering and the Center for Functional Nano Fine Chemicals, Chonnam National University, Gwangju 500-757, Republic of Korea.
Park
Ji Won
JW
Lee
Kwang Young
KY
Seo
Gon
G
Song
Mee Kyung
MK
Jeong
Soon-Yong
SY
D000327:Adsorption; D000475:Alkenes / Q000737:chemistry*; D017607:Aluminum Compounds / Q000737:chemistry; D000641:Ammonia; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology / Q000379:methods*; D009584:Nitrogen; D010710:Phosphates / Q000737:chemistry; D056951:Photoelectron Spectroscopy; D017655:Silicon Compounds / Q000737:chemistry; D013696:Temperature; D013816:Thermodynamics; D017641:Zeolites / Q000737:chemistry*
D000475:Alkenes; D017607:Aluminum Compounds; D010710:Phosphates; D017655:Silicon Compounds; D017641:Zeolites; D000641:Ammonia; D003300:Copper; C012714:aluminum phosphate; D009584:Nitrogen; D000432:Methanol