Lawson Shane, Farsad Alireza, Rezaei Fateme, Ludlow Douglas, Rownaghi Ali A
Department of Chemical & Biochemical Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409-1230, United States.
ACS Appl Mater Interfaces. 2021 Jan 13;13(1):781-794. doi: 10.1021/acsami.0c20752. Epub 2020 Dec 28.
Previously, 3D printing of porous materials and metal oxides was limited to low loading metal loadings, as increasing the nitrate salt concentrations, which are used to generate the oxide component, gave rise to poor rheological properties beyond 10 wt %. In this study, we addressed this problem by directly printing insoluble oxides alongside H-ZSM-5 zeolite, which allowed for increased oxide loadings. Various metal oxides such as VO, ZrO, CrO, and GaO were doped onto H-ZSM-5 through the additive manufacturing method. Characterization and correlation between the X-ray diffraction, NH-temperature-programmed desorption, O-temperature programmed oxidation, temperature-programmed reduction, scanning electron microscopy-energy dispersive spectroscopy, and CO DRIFTS experiments revealed that directly 3D printing metal oxides/H-ZSM-5 inks leads to significant modification in the surface properties and oxide bulk dispersion, thereby enhancing the composites' reducibility and giving rise to widely differing product distributions in -hexane cracking reaction. The obtained metal oxide/zeolite structured materials were used as bifunctional structured catalysts for the selective formation of light olefins from hexane at 550-600 °C and GHSV = 9000 mL/g·h in a packed-bed reactor. Among the various compositions of metal oxides/H-ZSM-5 examined (i.e., 15 wt % GaO, 15 wt % ZrO, 15 wt % VO, 15 wt % CrO, or 5 wt % Cr/10 wt % ZrO/10 wt % VO/10 wt % GaO balanced with H-ZSM-5), the 15 wt % Cr/ZSM-5 monolith displayed the best -hexane cracking performance, as it achieved 80-85% conversion of hexane with a 40% selectivity toward propylene, 30% selectivity toward ethylene, and 10% selectivity toward butene at 550 °C. The sample also showed zero benzene/toluene/xylene selectivity and no deactivation after 6 h. This study represents a proof-of-concept for tailoring customizable heterogeneous structured catalysts by directly 3D printing high loading of metal oxides/porous zeolite and is a breakthrough in material science.
此前，多孔材料和金属氧化物的3D打印仅限于低负载金属含量，因为增加用于生成氧化物成分的硝酸盐浓度会导致流变性能变差，超过10 wt%时尤为明显。在本研究中，我们通过将不溶性氧化物与H-ZSM-5沸石一起直接打印来解决这一问题，从而实现了更高的氧化物负载量。通过增材制造方法将各种金属氧化物（如VO、ZrO、CrO和GaO）掺杂到H-ZSM-5上。X射线衍射、NH3程序升温脱附、O2程序升温氧化、程序升温还原、扫描电子显微镜-能谱和CO漫反射红外傅里叶变换光谱实验之间的表征和相关性表明，直接3D打印金属氧化物/H-ZSM-5油墨会导致表面性质和氧化物体相分散性发生显著变化，从而提高复合材料的还原性，并在己烷裂解反应中产生差异很大的产物分布。所获得的金属氧化物/沸石结构材料用作双功能结构催化剂，用于在550-600°C和GHSV = 9000 mL/g·h的条件下，在填充床反应器中由己烷选择性生成轻质烯烃。在所研究的各种金属氧化物/H-ZSM-5组合物中（即15 wt% GaO、15 wt% ZrO、15 wt% VO、15 wt% CrO或5 wt% Cr/10 wt% ZrO/10 wt% VO/10 wt% GaO与H-ZSM-5平衡），15 wt% Cr/ZSM-5整体式催化剂表现出最佳的己烷裂解性能，在550°C时，己烷转化率达到80-85%，对丙烯的选择性为40%，对乙烯的选择性为30%，对丁烯的选择性为10%。该样品对苯/甲苯/二甲苯的选择性也为零，并在6小时后未失活。本研究代表了通过直接3D打印高负载量的金属氧化物/多孔沸石来定制可定制的多相结构催化剂的概念验证，是材料科学领域的一项突破。
