Fluidized Catalytic Cracking Catalyst Microstructure as Determined by A Scanning Ion Microprobe

We have used high spatial resolution imaging secondary ion mass spectrometry (SIMS) to differentiate mineralogical phases and to investigate chemical segregations in fluidized catalytic cracking (FCC) catalyst particles. The oil industry relies on heterogeneous catalysis using these catalysts to convert heavy hydrocarbon fractions into high quality gasoline and fuel oil components. Catalyst performance is strongly influenced by catalyst microstructure and composition, with different chemical reactions occurring at specific types of sites within the particle. The zeolitic portions of the particle, where the majority of the oil conversion occurs, can be clearly distinguished from the surrounding silica-alumina matrix in analytical SIMS images.The University of Chicago scanning ion microprobe (SIM) employed in this study has been described previously. For these analyses, the instrument was operated with a 40 keV, 10 pA Ga+ primary ion probe focused to a 30 nm FWHM spot. Elemental SIMS maps were obtained from 10×10 μm2 areas in times not exceeding 524s.

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Aspects of high-resolution imaging with a scanning ion microprobe

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010014511x ◽

1986 ◽

Vol 44 ◽

pp. 750-751

Author(s):

R. Levi-Setti ◽

J. M. Chabala ◽

Y. L. Wang

Keyword(s):

Metal Ion ◽

Secondary Ion Mass Spectrometry ◽

Chromatic Aberration ◽

Ion Source ◽

Ion Microprobe ◽

Emission Pattern ◽

Intrinsic Resolution ◽

Resolution Imaging ◽

20 Nm ◽

Secondary Ion

We have shown the feasibility of 20 nm lateral resolution in both topographic and elemental imaging using probes of this size from a liquid metal ion source (LMIS) scanning ion microprobe (SIM). This performance, which approaches the intrinsic resolution limits of secondary ion mass spectrometry (SIMS), was attained by limiting the size of the beam defining aperture (5μm) to subtend a semiangle at the source of 0.16 mr. The ensuing probe current, in our chromatic-aberration limited optical system, was 1.6 pA with Ga+ or In+ sources. Although unique applications of such low current probes have been demonstrated,) the stringent alignment requirements which they imposed made their routine use impractical. For instance, the occasional tendency of the LMIS to shift its emission pattern caused severe misalignment problems.

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Imaging of Al-Li-Cu alloys with a Scanning Ion Microprobe

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100135174 ◽

1990 ◽

Vol 48 (2) ◽

pp. 314-315

Author(s):

K.K. Soni ◽

D.B. Williams ◽

J.M. Chabala ◽

R. Levi-Setti ◽

D.E. Newbury

Keyword(s):

Mass Spectrometry ◽

Secondary Ion Mass Spectrometry ◽

Equilibrium Phase ◽

Icosahedral Symmetry ◽

Ion Microprobe ◽

X Ray ◽

Cu Alloys ◽

Two Phases ◽

The University ◽

Secondary Ion

In contrast to the inability of x-ray microanalysis to detect Li, secondary ion mass spectrometry (SIMS) generates a very strong Li+ signal. The latter’s potential was recently exploited by Williams et al. in the study of binary Al-Li alloys. The present study of Al-Li-Cu was done using the high resolution scanning ion microprobe (SIM) at the University of Chicago (UC). The UC SIM employs a 40 keV, ∼70 nm diameter Ga+ probe extracted from a liquid Ga source, which is scanned over areas smaller than 160×160 μm2 using a 512×512 raster. During this experiment, the sample was held at 2 × 10-8 torr.In the Al-Li-Cu system, two phases of major importance are T1 and T2, with nominal compositions of Al2LiCu and Al6Li3Cu respectively. In commercial alloys, T1 develops a plate-like structure with a thickness <∼2 nm and is therefore inaccessible to conventional microanalytical techniques. T2 is the equilibrium phase with apparent icosahedral symmetry and its presence is undesirable in industrial alloys.

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Microchemistry of ZnO Varistors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133102 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1694-1695

Author(s):

K. K. Soni ◽

J. Hwang ◽

V. P. Dravid ◽

T. O. Mason ◽

R. Levi-Setti

Keyword(s):

Grain Boundaries ◽

Multiple Roles ◽

Grain Boundary Engineering ◽

Ion Microprobe ◽

Dopant Distribution ◽

Important Ingredient ◽

Zno Varistor ◽

Zno Varistors ◽

Zno Powder ◽

The University

ZnO varistors are made by mixing semiconducting ZnO powder with powders of other metal oxides e.g. Bi2O3, Sb2O3, CoO, MnO2, NiO, Cr2O3, SiO2 etc., followed by conventional pressing and sintering. The non-linear I-V characteristics of ZnO varistors result from the unique properties that the grain boundaries acquire as a result of dopant distribution. Each dopant plays important and sometimes multiple roles in improving the properties. However, the chemical nature of interfaces in this material is formidable mainly because often trace amounts of dopants are involved. A knowledge of the interface microchemistry is an essential component in the ‘grain boundary engineering’ of materials. The most important ingredient in this varistor is Bi2O3 which envelopes the ZnO grains and imparts high resistance to the grain boundaries. The solubility of Bi in ZnO is very small but has not been experimentally determined as a function of temperature.In this study, the dopant distribution in a commercial ZnO varistor was characterized by a scanning ion microprobe (SIM) developed at The University of Chicago (UC) which offers adequate sensitivity and spatial resolution.

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Advances in imaging SIMS studies of stained and BrdU-labelled human metaphase chromosomes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100141032 ◽

1995 ◽

Vol 53 ◽

pp. 932-933

Author(s):

R. Levi-Setti ◽

J. M. Chabala ◽

R. Espinosa ◽

M. M. Le Beau

Keyword(s):

High Performance ◽

Secondary Ion Mass Spectrometry ◽

Analytical Sensitivity ◽

Metaphase Chromosomes ◽

Banding Patterns ◽

Sector Mass Spectrometer ◽

Staining Methods ◽

The University ◽

Secondary Ion ◽

Better Than

We have shown previously that isotope-labelled nucleotides in human metaphase chromosomes can be detected and mapped by imaging secondary ion mass spectrometry (SIMS), using the University of Chicago high resolution scanning ion microprobe (UC SIM). These early studies, conducted with BrdU- and 14C-thymidine-labelled chromosomes via detection of the Br and 28CN- (14C14N-> labelcarrying signals, provided some evidence for the condensation of the label into banding patterns along the chromatids (SIMS bands) reminiscent of the well known Q- and G-bands obtained by conventional staining methods for optical microscopy. The potential of this technique has been greatly enhanced by the recent upgrade of the UC SIM, now coupled to a high performance magnetic sector mass spectrometer in lieu of the previous RF quadrupole mass filter. The high transmission of the new spectrometer improves the SIMS analytical sensitivity of the microprobe better than a hundredfold, overcoming most of the previous imaging limitations resulting from low count statistics.

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An analytical microscopic study of metals in fluidized catalytic cracking catalyst

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100145613 ◽

1986 ◽

Vol 44 ◽

pp. 854-855

Author(s):

Clifford S. Rainey

Keyword(s):

Electron Microscopy ◽

Spatial Distribution ◽

Catalytic Cracking ◽

Catalyst Deactivation ◽

Coke Formation ◽

Acid Sites ◽

Y Zeolite ◽

Fcc Catalyst ◽

Fluidized Catalytic Cracking ◽

High Regeneration

The spatial distribution of V and Ni deposited within fluidized catalytic cracking (FCC) catalyst is studied because these metals contribute to catalyst deactivation. Y zeolite in FCC microspheres are high SiO2 aluminosilicates with molecular-sized channels that contain a mixture of lanthanoids. They must withstand high regeneration temperatures and retain acid sites needed for cracking of hydrocarbons, a process essential for efficient gasoline production. Zeolite in combination with V to form vanadates, or less diffusion in the channels due to coke formation, may deactivate catalyst. Other factors such as metal "skins", microsphere sintering, and attrition may also be involved. SEM of FCC fracture surfaces, AEM of Y zeolite, and electron microscopy of this work are developed to better understand and minimize catalyst deactivation.

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