Al-Shafei Emad N, Masudi Ahmad, Yamani Zain H, Muraza Oki
Research and Development Center, Saudi Aramco, Dhahran 31311, Saudi Arabia.
Interdisciplinary Research Center for Hydrogen and Energy Storage and Chemical Engineering Department King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia.
ACS Omega. 2022 Aug 23;7(35):30807-30815. doi: 10.1021/acsomega.2c02119. eCollection 2022 Sep 6.
Nanozeolite Y was synthesized without a template and modified with phosphorous (P) and metals. P was introduced via impregnation with different weight loadings (0.5, 1, and 2 wt %), while ion exchange was developed to introduce zirconium (Zr) and cobalt (Co). The physicochemical properties of the catalysts were characterized with X-ray diffraction (XRD), N adsorption-desorption, temperature-programmed desorption of ammonia (NH-TPD), and Al and P solid-state nuclear magnetic resonance (NMR). The parent nanozeolite Y showed an identical XRD pattern to that of a previous study, and the modified nanozeolite Y showed a lower crystallinity. The introduction of P altered tetrahedral Al to an octahedral coordination, which affected the catalyst acidity. Then, the catalyst was evaluated to produce olefins from -dodecane at 550, 575, and 600 °C. The conversion, gas yield, and olefin yield increased with increasing temperature. The maximum olefin yield (63%) was achieved with the introduction of 1 wt % P with the highest selectivity to ethylene. The Co-modified nanozeolite altered the zeolite structure and exhibited similar activity to the P-modified one. Meanwhile, Zr-modified nanozeolite Y caused excessive metal distribution, blocked the porous structure of the zeolite, and then reduced the catalytic activity.
无模板合成了纳米Y型沸石，并对其进行了磷（P）和金属改性。通过不同重量负载量（0.5、1和2 wt%）的浸渍引入P，同时通过离子交换引入锆（Zr）和钴（Co）。采用X射线衍射（XRD）、N吸附-脱附、氨程序升温脱附（NH-TPD）以及Al和P的固态核磁共振（NMR）对催化剂的物理化学性质进行了表征。母体纳米Y型沸石的XRD图谱与先前研究的图谱相同，而改性纳米Y型沸石的结晶度较低。P的引入将四面体Al转变为八面体配位，这影响了催化剂的酸度。然后，对该催化剂在550、575和600℃下由正十二烷生产烯烃的性能进行了评估。转化率、气体产率和烯烃产率随温度升高而增加。引入1 wt%的P时实现了最大烯烃产率（63%），且对乙烯的选择性最高。Co改性的纳米沸石改变了沸石结构，表现出与P改性沸石相似的活性。同时，Zr改性的纳米Y型沸石导致金属分布过多，堵塞了沸石的多孔结构，进而降低了催化活性。
