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首页> 外文期刊>ACS catalysis >Structural Changes in Deactivated Fluid Catalytic Cracking Catalysts Determined by Electron Microscopy
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Structural Changes in Deactivated Fluid Catalytic Cracking Catalysts Determined by Electron Microscopy

机译：通过电子显微镜测定的失活流体催化裂化催化剂的结构变化

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摘要

Fluid catalytic cracking, an important process in the chemical industry, uses porous composite particles to convert the heavy fractions of crude oil into transportation fuels and chemical feedstocks. The employed particles, a spherical composite of zeolite and clay, decrease in catalytic activity during long-term operation, which demands their continuous replacement. To extend the lifetime of these catalysts, it is essential to understand the structural changes that cause the observed decrease in activity. By using a range of electron microscopy and elemental mapping techniques, the structural and chemical makeup of pristine and progressively deactivated catalyst particles were characterized from the micro- to the nanometer scale. Independent of the deactivation degree, the catalyst particles are found to maintain a porous interior structure similar to that of the pristine catalyst. An increasingly dense amorphous silicaalumina envelope enwrapping individual catalyst particles is formed during operation. Regions that contain calcium compounds and spinel-type iron oxide particles are present. While the porosity of this envelope apparently decreases with deactivation, its thickness reaches a plateau at about 2 mu m. Not only does this process happen independently of the detected impurity levels but also the uptake of impurities appears to be physically halted by the forming envelope.
机译：流体催化裂化是化学工业中的重要过程，使用多孔复合颗粒将原油重馏分转化为运输燃料和化学原料。所用颗粒，沸石和粘土的球形复合物，长期运行期间催化活性降低，需要它们的连续替代品。为了延长这些催化剂的寿命，必须了解导致观察到的活性降低的结构变化。通过使用一系列电子显微镜和元素映射技术，原始和逐渐失活的催化剂颗粒的结构和化学构成从微量到纳米级表征。独立于失活度，发现催化剂颗粒保持与原始催化剂类似的多孔内部结构。在操作期间形成越来越致密的无定形二氧化硅烷包膜包裹单独的催化剂颗粒。存在含有钙化合物和尖晶石型氧化铁颗粒的区域。虽然这种信封的孔隙率明显随着停用而降低，但其厚度在大约2μm的厚度达到高原。该过程不仅独立于检测到的杂质水平而发生，而且杂质的摄取似乎被形成的封套物理地停止。

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