Particle Characterization
Catalysts are widely used as an important auxiliary material in the chemical and petrochemical industry. They are able to accelerate chemical reactions by lowering the activation energy, i.e. they change reaction kinetics. Thus, using catalysts in industrial processes has the advantage of higher productivity combined with less energy consumption.
In many processes a mixture of liquid or gaseous raw materials (e.g. petroleum) is transformed in a reactor with solid catalyst material. Depending on the desired reaction, catalysts of different materials such as ceramics, alumina, metal or alloys are used. To save costs, inexpensive substrates can be coated with the actual catalyst (e.g. platinum or molybdenum).
The active surface as well as the form of the catalysts is crucial for their efficiency. It is important that sufficient free volume is available for the reactants. Moreover, the counter pressure built up by the catalyst must not be too high. Spherical, comb-shaped or rod-shaped geometries have proven to be especially suitable. The rod-shaped catalysts have different shapes; their profiles can have an ellipsoid, trilobe or quadrulobe shape.
The following parameters are crucial for effective and controlled catalytic reactions with a high yield:
- A large active surface
- A large free volume in the reactor to have enough space for the mixing of the reactants
- A high and evenly distributed permeability in the reactor
- A defined ratio of active surface and reactant
The analysis of size and shape plays an important role for the quality control of catalysts. Sieve analysis is often used; however, it only provides the required size information for spherical particles. Rods, for example, pass the mesh with a particular orientation which makes it impossible to clearly separate breadth and length values. Another method is to measure catalysts with calipers which is time-consuming and hardly representative as it can only be done for small quantities.
The CAMSIZER from the German company Retsch Technology is an ideal tool for particle size and shape analysis of dry, flowable bulk goods with dynamic image analysis. Due to its wide measuring range of 30 µm to 30 mm and the excellent compatibility to sieve analysis, this is a highly efficient alternative to traditional sieving. The main areas where this instrument is used are quality control, research and production monitoring. In combination with solutions for the partial or complete measurement automation, continuous sample analysis can also be realized cost-effectively. The instrument's patented measuring setup of two digital cameras as the adaptive measuring unit improves and optimises particle analysis with digital image processing. Thus it is possible to cover the complete measuring range without any adjustments of the instrument.
The benefits of using this instrument for the quality control of catalysts are quite obvious: a large quantity of particles can be measured in a very short time. The resolution and reproducibility of the measurements are much higher than those obtained by sieve analysis or measurements with calipers. The possibility of obtaining other shape parameters apart from length and diameter is very important as these allow conclusions about the geometry of the catalyst. Thus it is possible to determine, for example, the quantity of defective particles.
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The ANALYSETTE 22 MicroTec plus makes particle size measurement to the simplest thing in the world 