Article

Catalytic activity in individual cracking catalyst particles imaged throughout different life stages by selective staining.

Inorganic Chemistry and Catalysis Group, Debye Institute for NanoMaterials Science, Faculty of Science, Utrecht University, 3584 CG Utrecht, The Netherlands.
Nature Chemistry (Impact Factor: 23.3). 11/2011; 3(11):862-7. DOI: 10.1038/nchem.1148
Source: PubMed

ABSTRACT Fluid catalytic cracking (FCC) is the major conversion process used in oil refineries to produce valuable hydrocarbons from crude oil fractions. Because the demand for oil-based products is ever increasing, research has been ongoing to improve the performance of FCC catalyst particles, which are complex mixtures of zeolite and binder materials. Unfortunately, there is limited insight into the distribution and activity of individual zeolitic domains at different life stages. Here we introduce a staining method to visualize the structure of zeolite particulates and other FCC components. Brønsted acidity maps have been constructed at the single particle level from fluorescence microscopy images. By applying a statistical methodology to a series of catalysts deactivated via industrial protocols, a correlation is established between Brønsted acidity and cracking activity. The generally applicable method has clear potential for catalyst diagnostics, as it determines intra- and interparticle Brønsted acidity distributions for industrial FCC materials.

Download full-text

Full-text

Available from: Bert M Weckhuysen, Aug 23, 2014
3 Followers
 · 
199 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Full-field transmission X-ray microscopy has been used to determine the 3D structure of a whole individual fluid catalytic cracking (FCC) particle at high spatial resolution and in a fast, noninvasive manner, maintaining the full integrity of the particle. Using X-ray absorption mosaic imaging to combine multiple fields of view, computed tomography was performed to visualize the macropore structure of the catalyst and its availability for mass transport. We mapped the relative spatial distributions of Ni and Fe using multiple-energy tomography at the respective X-ray absorption K-edges and correlated these distributions with porosity and permeability of an equilibrated catalyst (E-cat) particle. Both metals were found to accumulate in outer layers of the particle, effectively decreasing porosity by clogging of pores and eventually restricting access into the FCC particle.
    Journal of the American Chemical Society 01/2015; 137(1). DOI:10.1021/ja511503d · 11.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Optical absorption and confocal fluorescence micro-spectroscopy were applied to investigate Brønsted acidity in millimetre-sized extrudates of Na(H)-ZSM-5 and SiO2 with varying ZSM-5 content. Partially (residual Na present) and fully proton-exchanged extrudates were employed, using thiophene oligomerization as a probe reaction. Time-resolved in situ optical absorption spectra and time dependent DFT calculations revealed several initial reaction pathways during the oligomerization reaction. In particular, it was found that protonated thiophene monomers reacted by either oligomerization (via reaction with un-reacted thiophene monomers) or ring-opening, depending on the Brønsted acid site density in each sample. Moreover, fully-exchanged extrudates not only have significantly higher reactivity than partially-exchanged samples, but they also favour the formation of ring-opening products, that are not formed on the partially-exchanged samples. Confocal fluorescence microscopy was employed to visualise non-invasively in 3D, the heterogeneity and homogeneity of thiophene oligomers on partially- and fully-exchanged extrudates, respectively. Furthermore, it was observed that extrudates with high binder content produce a higher relative amount of conjugated species, related with a higher quantity of available monomer in the binder, which is able to react further with intermediates adsorbed on active sites. Moreover, these conjugated species appear to form near the external surface of ZSM-5 crystals/agglomerates.
    Physical Chemistry Chemical Physics 08/2014; 16(39). DOI:10.1039/C4CP03649B · 4.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A synchrotron-based infrared micro-spectroscopy study has been conducted to investigate the structure as well as the Brønsted and Lewis acidity of Fluid Catalytic Cracking (FCC) catalyst particles at the individual particle level. Both fresh and laboratory-deactivated catalyst particles have been studied. The applied deactivation protocols were steaming (ST), two-step cyclic deactivation (CD) and Mitchell impregnation-steam deactivation (MI). In addition, an equilibrium catalyst (Ecat) taken from a real cracking unit has been investigated. From the infrared spectra of the fresh and laboratory-deactivated samples it was clear that the zeolite component experiences partial collapse upon deactivation. Furthermore, it was found that characteristic bands, caused by the presence of clay material, are lost upon deactivation. After pyridine adsorption, the acidity of the samples could be monitored. Both Brønsted and Lewis acidity decreased in the following order: Fresh > ST > CD > MI. The Ecat sample was found to display acidity in between those of CD and MI samples. These findings are in line with earlier bulk transmission infrared as well as ammonia temperature programmed desorption measurements, which confirms the validity of acidity measurements at the single particle level. However, additional information about the distribution of Brønsted and Lewis acidity within individual catalyst particles becomes available. The developed approach reveals a larger variety in the amount of Brønsted acid sites for individual Ecat particles as compared to CD and MI particles. This observation can be attributed to the wide age distribution within industrial equilibrium catalysts and directly shows the added value of micro-spectroscopy approaches in the investigation of interparticle heterogeneities.
    Microporous and Mesoporous Materials 01/2013; 166:86–92. DOI:10.1016/j.micromeso.2012.08.007 · 3.21 Impact Factor