Iron poisoning is a well-known problem for fluid catalytic cracking catalysts. To better understand this issue, several characterization techniques were used to examine a catalyst sample from a commercial unit. Under SEM-EDX, most cross sections of the catalyst particles exhibited iron nodule rims enriched with Fe, other contaminant metals, and Si. Scanning TEM X-ray mapping further confirmed that, compared to the inside of a catalyst particle, the surface layer was enriched in Si and contaminant metals, while depleted in Al. This catalyst had high frequency-dependent magnetic susceptibility, suggesting that some or all of the iron-bearing species should be in the nanometer size range. In TEM, the nodules were found to consist of Fe-bearing nanoparticles, imbedded in an amorphous matrix. The nanoparticles were also enriched in Mg, Ni or Ca, while the matrix was dominated by Si and minor Al. Selected area electron diffraction pattern indicated that these iron enriched nanoparticles had the spinel structure. These results should shed light on iron poisoning issues in FCC units.

对于流化催化裂化催化剂，铁中毒是众所周知的问题。为了更好地理解这个问题，使用了几种表征技术来检查来自商业单位的催化剂样品。在SEM-EDX下，催化剂颗粒的大多数横截面都显示出富含铁，其他污染物金属和Si的铁结核边缘。扫描TEM X射线作图进一步证实，与催化剂颗粒的内部相比，该表面层富含Si和杂质金属，而贫有Al。该催化剂具有高频率依赖性的磁化率，表明某些或所有含铁物质应在纳米尺寸范围内。在TEM中，发现结核由嵌入非晶态基质中的含铁纳米颗粒组成。纳米粒子还富含Mg，Ni或Ca，而基体则以Si和次要Al为主。选定区域的电子衍射图表明这些富铁纳米颗粒具有尖晶石结构。这些结果应有助于阐明FCC装置中的铁中毒问题。