| 초록 |
Nanocrystalline SAPO-34 and TiAPSO-34 molecular sieves were successfully synthesized with an average crystallite size of 100 nm and with various Ti contents in the framework, using tetraethylammonium hydroxide as the sole organic structure-directing agent. When the Ti source was used as the tetravalent framework atom instead of Si under otherwise identical synthesis conditions, another cage-based, small-pore molecular sieve, TiAPO-18 was stabilized. The newly synthesized materials were characterized by powder XRD, SEM, elemental analysis, N2 sorption, diffuse reflectance infrared Fourier transform (DRIFT), 27Al and 29Si MAS NMR, and TGA/DTA techniques. The incorporation of Ti into the tetrahedral framework of TiAPSO-34s and TiAPO-18 was directly and/or indirectly confirmed by elemental analysis, DRIFT, and 29Si MAS NMR analyses. The NH3 TPD results for the H-SAPO-34 and H-TiAPSO-34s catalysts showed that incorporating Ti resulted in an increase in the concentration of Brönsted acid sites, which led to improved catalytic activity and stability of the methanol-to-olefin reaction. |
