Basic laboratory training in CRT - An Introduction to Chemical Reaction Technology

During the basic practical training in Chemical Reaction Engineering (CRT) that forms part of the bachelor’s degree programme in Applied Chemistry, students learn, among other things, how to balance reactors and determine the kinetics in different types of reactors. The following overview shows some contents of the practical course:

Reactors can be designed in different ways, e.g. as stirred tank (1st picture) or as stirred tank cascade reactors (2nd picture). 

In order to select suitable calculation models, the time response of such reactors must be determined, by means of a shock marker for example. 

Determining the kinetics of stirred tank reactions

The diagram (1st picture) shows the comparison between measured and calculated values in the laboratory cascade with almost 100% consistency.

If the calculation model is valid, the kinetics of the reaction can be determined by measuring the degree of conversion of a chemical reaction at different experimental settings (2nd picture).

Determining the kinetics in tubular reactors

Another type of reactor is the tubular reactor. In the experimental set-up, a reactor of that type is achieved using a coiled hose. The degree of conversion that can be achieved during a chemical reaction is influenced by the mixing behaviour of the tubular reactor, which can be determined by means of a shock marker, for example. A corresponding evaluation is shown in the figure below.

Determining the kinetics in batch reactors

Batch reactors are not just used for producing chemical products. In the laboratory, they are ideally suited for observing chemical reactions over time. The measured data are used to create a mathematical model to describe the reaction speed (kinetics). The picture on the right shows the laboratory apparatus and below it, you can see the evaluation and result of such an experiment.

Carbon monoxide conversion

Chemical reactions can either release heat (exothermic reactions) or require heat (endothermic reactions). If exothermic reactions are carried out at increasingly high temperatures, the chemical equilibrium shifts in the direction of the starting materials, reducing the degree of conversion that can be achieved. During the technically important “Carbon Monoxide Conversion” reaction, this behaviour can be observed during the experiment and compared with calculation models. The first picture shows the corresponding reactor set-up. The second picture shows the evaluation.

Overview of further laboratory courses and courses in Technical Chemistry

In the advanced module in Technical Chemistry, specialized laboratory courses in CRT are offered at later stages of the degree programme. Here, students will find information and interesting references to experiments from practical courses in technical chemistry that will enable them to gain a deeper insight into the contents of the course.

Heterogeneous catalytic reactions

Cinnamic acid hydrogenation

Based on the cinnamic acid hydrogenation in the liquid phase on a palladium-activated carbon catalyst, the interplay between mass transfer across two phase boundaries and chemical reaction can be studied. The results of the experiment will be used to determine parameters of a suitable macrokinetic model.

Methanol splitting

The splitting of methanol into hydrogen and carbon monoxide is carried out in the gas phase on a catalyst. The increase in pressure over time during the reaction at different temperatures provides information on the extent to which mass transfer within the catalyst hinders the reaction.

Catalytic exhaust gas purification

Catalytic exhaust gas purification is one of the most important chemical processes in environmental technology. The experimental set-up depicted here allows suitable catalysts to be tested and the catalytic purification process to be studied and optimized in accordance with the operating parameters.

Gradientless loop reactor

An ideal vessel is ideally suited for determining kinetic data of chemical reactions, since the conversion behaviour can be described using a simple model. This is the reason why such a reactor is also used for testing catalytic gas phase reactions. In this case, however, this ideal vessel is called a “gradientless loop reactor” and is a small technical marvel.

Selected chapters of the Chem. Reaction Technology

Kinetics of limestone dissolution

In flue gas cleaning downstream of power plants, limestone is generally used as a reactive absorbent from which, after reacting with sulphur dioxide and oxidation with oxygen, usable gypsum is produced.

An important partial step in this process is the dissolution rate of limestone, which depends on the pH value. The kinetics of limestone dissolution can be determined using simple titration apparatus.

Oxidation of sodium sulphite/precipitated calcium sulphite

A further important step in the flue gas cleaning process is the oxidation of the resulting calcium sulphite into calcium sulphate (gypsum). In two experiments into the oxidation of sodium sulphite and the pH-dependent oxidation of precipitated calcium sulphite, the influence of mass transport can be determined quantitatively and the parameters of a macrokinetic model can be determined.

Tubular reactor im Technikum

The tubular reactor im Technikum (left picture) differs significantly from a laboratory reactor in its time and reaction behaviour. Only complex mathematical operations can describe the effect of the relatively high degree of mixing in such a tube, caused by to the flow, on the chemical reaction.

The simulation programme “Reasim” (which was developed at the university as part of a Diplom thesis) calculates the course of the reaction at different degrees of mixing. From an ideal tubular reactor to an ideally mixed stirred tank, the achievable degree of conversion decreases steadily during a chemical reaction (second picture).

Stirred tank reactors

Very large stirred tank reactors, as often encountered in the chemical industry, are far from achieving “ideal” behaviour (Fig. 1). The mathematical description of such a reactor can be carried out using a “mixed model”. A model of that type is assembled from ideal reactor components. However, the model parameters must be determined by measuring the time behaviour.

In order to do that, a shock marking is carried out and evaluated using the “Reasim” simulation programme (Fig. 2). At this point we would like to thank Mr. Thomas Meyer for his outstanding Diplom thesis on the creation of the simulation programme “Reasim”!

Technical Electrochemistry/Electrochemical Process Engineering

Electrochemical Reaction Technology expands upon Chemical Reaction Technology to include charge transfers at the electrodes during a redox reaction. In the laboratory course, electrochemical methods such as potentiostatic and galvanic measurements, cyclic voltammetry, and impedance spectroscopy are carried out.

Basic chemical engineering operations

Determining the law governing the rate of reactions in liquid phase

Everything takes time! This also applies to chemical reactions. Investigating the time needed for a reaction to progress provides basic insights into the operation of a chemical reactor.

In this experimental set up, reactions are carried out in liquid phase. The change in the composition of a mixture over time is measured photometrically. After proper evaluation, a reaction rate law is ultimately obtained.

Phase equilibrium of a binary mixture

In this case, a basic understanding of the separation of substances by distillation is achieved here with a comparatively simple set-up in terms of apparatus. Students also engage “hands-on” so that they can see what happens!

The purpose of the exercise is to determine what is known as the phase equilibrium of a binary mixture experimentally.

Rectification column

Long and thin,
hot below
and cold at the top.

That is how a rectification column, in which a liquid mixture is separated into its components, appears to us.

This is how schnapps is distilled or crude oil is broken down into its fractions.

Pump and system characteristics of a centrifugal pump

What do a fountain, a Saturn 5 rocket, and the good old “Dullnraamer” have in common?

That’s right! They all pump liquids.

In one case, that liquid is water, while in another, it’s liquid hydrogen and oxygen. But the liquid pumped by the last of those three will only be revealed to those who study here!

The right pump for the right purpose!

A typical chemical pump – as shown in the picture – looks different from the injection pump of an internal combustion engine, even though the physics behind it is identical. Liquid flow, pressure loss, and pump and system characteristics are examined on a technical scale using this equipment.