Modified Catalysts and Their Fractal Properties

Gianina Dobrescu,Florica Papa,Daniela Berger,Monica Raciulete,Razvan State,Niculae I Ionescu,Ioan Balint

doi:10.3390/catal11121518

Gianina Dobrescu, Florica Papa + Show 5 more

Open Access

https://doi.org/10.3390/catal11121518

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Journal: Catalysts	Publication Date: Dec 14, 2021
Citations: 6	License type: CC BY 4.0

Affiliation: Romanian Academy, Polytechnic University of Bucharest

Abstract

Obtaining high-area catalysts is in demand in heterogeneous catalysis as it influences the ratio between the number of active surface sites and the number of total surface sites of the catalysts. From this point of view, fractal theory seems to be a suitable instrument to characterize catalysts’ surfaces. Moreover, catalysts with higher fractal dimensions will perform better in catalytic reactions. Modifying catalysts to increase their fractal dimension is a constant concern in heterogeneous catalysis. In this paper, scientific results related to oxide catalysts, such as lanthanum cobaltites and ferrites with perovskite structure, and nanoparticle catalysts (such as Pt, Rh, Pt-Cu, etc.) will be reviewed, emphasizing their fractal properties and the influence of their modification on both fractal and catalytic properties. Some of the methods used to compute the fractal dimension of the catalysts (micrograph fractal analysis and the adsorption isotherm method) and the computed fractal dimensions will be presented and discussed.

Highlights

The power of self-similarity as a fractal property was first emphasized in 1975 by B.BMandelbort [1,2]
The experimental results revealed that the synthesis method of catalysts influences the fractal dimension
Both the nature of the precursor as well as the introduction of dopants changes the fractal dimension for mixed oxide perovskite-type catalysts

Summary

Introduction

The power of self-similarity as a fractal property was first emphasized in 1975 by B.B. Mandelbort [1,2]. In 1984, David Avnir, Dina Farin and Peter Pfeifer [11] reported that, at the molecular scale, the surfaces of most materials are fractal. This property leads to scaling laws of great interest in the description of various processes specific to heterogeneous chemistry: physical adsorption, chemisorption, and catalytic processes. We shall focus only on the influence of fractal behavior self-similarity on catalytic properties

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Discussion

Conclusion