Catalysis for Fine Chemicals

Werner Bonrath, Jonathan Medlock, Marc-André Müller, Jan Schütz

• Publisher: De Gruyter
• Year: 2021
• Print ISBN: 9783110571158
• eBook ISBN: 9783110571257
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Chemistry
• Index: Chemistry

A wide range of chemical products (especially fine chemicals) are important for a healthy and enjoyable modern life; therefore efficient syntheses of these materials are essential. Traditional stoichiometric processes need to be replaced by modern catalytical methods in the change to sustainable chemistry and the production of lower amounts of waste.

This book summarizes the wide variety of catalytic methods that have been developed and applied on an industrial scale in recent years to fulfill this goal. The synthesis of compound classes such as pharmaceuticals, agrochemicals, flavoring, and fragrance compounds as well as food additives such as vitamins exemplify the use of these modern catalytic methods in the modern chemical industry.

1 Introduction and fundamental aspects

Today, the application of catalysts is fundamental for efficient synthetic methods and production processes. During the last decades in the fine chemicals industry, and partly in the pharmaceutical industry, many chemical conversions which require stoichiometric amounts of reagents have been replaced by catalytic processes. In the bulk chemical industry, the application of catalytic methods is already well established. This difference can be partly explained by the higher complexity of pharmaceuticals and fine chemicals which makes catalysis more demanding and process development more expensive and complex.

In this chapter, we review some of the general concepts, techniques and principles that are important for the discussion of the examples in the later chapters. It is not supposed to be a comprehensive introduction to these topics, rather a refresher/reminder of important points to remember. For more detailed information and discussion of the points in this chapter, please refer to a standard textbook on catalysis, for example, [1, 2, 3, 4, 5, 6].

The definition of the term catalyst is based on the fundamental work of Wilhelm Ostwald (Nobel Prize, 1909).

“A catalyst is a compound which influences the reaction rate of a chemical reaction without being consumed and without the ability to influence the thermodynamic equilibrium of the catalysed reaction [7, 8, 9, 10, 11, 12].”

Catalysts influence reactions that are thermodynamically possible (see also Hess’ law); the function of a catalyst is to decrease the activation energy (E_A) of the reaction by providing an alternative pathway or mechanism for the reaction to follow (Figure 1.1).

Figure 1.1: Energy–reaction coordinate of catalysed and non-catalysed reactions.

Wilhelm Ostwald had a tremendous influence on the field of physical chemistry and catalytic concepts. His work was world-leading for decades and resulted in various industrial applications. For instance, the Ostwald process for nitric acid later became the basis of the work of Haber, Bosch and Mittasch for the ammonia process from hydrogen and nitrogen. Nowadays, catalysts have significant impact on industrial production processes. It is assumed that 90% of all chemically obtained industrial goods come in contact with at least one catalytical production step during their manufacture [13].

The main targets of catalytic reactions are:

1. Mild reaction conditions,
2. Decreased waste formation,
3. Increased selectivity,
4. Increased efficiency.

From a physical chemistry point of view, catalytic reactions can be divided into homogeneous and heterogeneous reactions. In heterogeneous catalysis, the catalyst and the substrate are in separate phases, for example liquid/solid, solid/gas. In homogeneous catalysis, the catalyst and substrate are in one phase. The general advantages and disadvantages of homo- and heterogeneous catalysed reactions are summarised in Table 1.1. In particular, because of their easy separation and recovery, heterogeneous catalysts are more frequently found with increasing product volumes and decreasing product prices. In contrast, for asymmetric reactions, homogeneous catalysts are clearly superior to heterogeneous systems.

Table 1.1:Advantages and disadvantages of heterogeneous and homogeneous catalysed reactions....

Table of contents

• Title Page
• Copyright
• Contents
• Preface
• 1 Introduction and fundamental aspects
• 2 Heterogeneous hydrogenations
• 3 Homogeneous hydrogenations
• 4 Oxidations
• 5 Gas-phase reactions
• 6 C–C-bond and C–N-bond forming reactions (metal-catalysed)
• 7 Rearrangement reactions
• 8 Acid–base-catalysed reactions
• 9 Phase transfer catalysis (PTC)
• 10 Biocatalysis
• 11 New trends
• Index