The Role of Catalysis

The generation of copious amounts of inorganic salts can similarly be largely circumvented by replacing stoichiometric mineral acids, such as H2S04, and Lewis acids and stoichiometric bases, such as NaOH, KOH, with recyclable solid acids and bases, preferably in catalytic amounts (see later). 

For example, the technologies used for the production of many substituted aromatic compounds (Fig. 1.4) have not changed in more than a century and are, therefore, ripe for substitution by catalytic, low-salt alternatives (Fig. 1.5). 

Biocatalysis has many advantages in the context of green chemistry, e.g. mild reaction conditions and often fewer steps than conventional chemical procedures because protection and deprotection of functional groups are often not required. Consequently, classical chemical procedures are increasingly being replaced by cleaner biocatalytic alternatives in the fine chemicals industry (see later). 

Once the major cause of the waste has been recognized, the solution to the waste problem is evident the general replacement of classical syntheses that use stoichiometric amounts of inorganic (or organic) reagents by cleaner, catalytic alternatives. If the solution is so simple, why are catalytic processes not as widely used in fine and specialty chemicals manufacture as they are in bulk chemicals. One reason is that the volumes involved are much smaller, and thus the need to minimize waste is less acute than in bulk chemicals manufacture. Secondly, the economics of bulk chemicals manufacture dictate the use of the least expensive reagent, which was generally the most atom economical, for example O2 for oxidation H 2 for reduction, and CO for C-C bond formation. 

A third reason is the pressure of time. In pharmaceutical manufacture time to market is crucial, and an advantage of many time-honored classical technologies is that they are well tried and broadly applicable and, hence, can be implemented rather quickly. In contrast, the development of a cleaner, catalytic alternative could be more time consuming. Consequently, environmentally (and economically) inferior technologies are often used to meet stringent market deadlines, and subsequent process changes can be prohibitive owing to problems associated with FDA approval. 

The desperate need for more catalytic methodologies in industrial organic synthesis is nowhere more apparent than in oxidation chemistry. For example, as any 

Obviously there is a definite need in the fine chemical and pharmaceutical industry for catalytic systems that are green and scalable and have broad utihty [10]. More recently, oxidations with the inexpensive household bleach (NaOCl) catalyzed by stable nitroxyl radicals, such as TEMPO [17] and PIPO [18], have emerged as more environmentally friendly methods. It is worth noting at this juncture that greenness is a relative description and there are many shades of green. Although the use of NaOCl as the terminal oxidant affords NaCl as the by-product and may lead to the formation of chlorinated impurities, it constitutes a dramatic improvement compared to the use of chromium(VI) and other 

Biocatalysis has many attractive features in the context of green chemistry and sustainable development  

The catalyst (an enzyme) is derived from renewable resources and is biocompatible (sometimes even edible), biodegradable, and essentially nonhazard-ous, that is, it fulfills the criteria of sustainability remarkably well. 

Biocatalysis avoids the use of, and contamination of products by, scarce precious metals such as palladium, platinum, and rhodium. The long-term commercial viability of many endangered elements, such as various noble metals, is questionable. Moreover, the costs of removing traces of noble metals, to an acceptable level, from end products can be substantial. 

Reactions are performed in an environmentally compatible solvent (water) under mild conditions (physiological pH and ambient temperature and pressure). 

As a direct result of the higher selectivities and milder reaction conditions, biocatalytic processes often afford products in higher purity than traditional chemical or chemo-catal5dic processes. 

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Allen, D. (1992). The Role of Catalysis in Industrial Waste Reduction. Industrial Environmental Chemistry, ed. D. T. Sawyer, and A. E. Martell, 89-98. New York Plenum Press. 

Environmental catalysis has its potential in improving innovations in the field of catalysis and highlighting the new directions for research driven by market, social, and environmental needs. Therefore, it can be concluded that environmental catalysis plays a key role in demonstrating the role of catalysis as a driver of sustainability by improving the quality of life and protecting human health and the environment... 

Explain the role of catalysis in fuel cell technology. 

The final chapter of this book is dedicated to solar energy as a source of hydrogen and for CO2 conversion. This chapter introduces the main concepts of the field and highlights the role of catalysis for using solar energy. 

In 1794, the English chemist Elizabeth Fulhame published a book called An Essay on Combustion. Her book included many of the first recorded ideas about the role of catalysis in chemical processes. 

Sheldon, R. A., Consider the environmental quotient, Chemtech, 1994, 24(3), 38-47 Sheldon, R. A., The role of catalysis in waste minimization, in Precision Process... 

Although a specific chapter dedicated to the role of catalysis in energy production is not included, because most of the aspects were already covered in the final chapter of the previous book, the reader can easily use the final sections of each chapter to identify priorities for research on catalysis for sustainable energy. 

The difficult task of examining the role of catalysis in coal liquefaction has been taken on by Mochida and Sakanishi. They show the catalytic requirements in various stages of coal conversion and the many complex interactions of the catalyst with coal constituents. They also point out directions for future catalysis research needed for more economical coal liquefaction, a commendable feature for processes requiring a long lead time. 

Applying the foregoing thermodynamic and kinetic information to manganese behavior in natural water systems is considerably limited because the manganese system exemplifies the difficulties discussed earlier. On the thermodynamic side, the kinds of oxide phases in natural waters may not correspond to those for which equilibrium data are available. Also, cation exchange reactions are probably important (21). On the kinetic side, the role of catalysis by various mineral surfaces in suspension or in sediments is not really known. Of considerable importance may be microbial catalysis of the oxidation or reduction processes, as described by Ehrlich (7). With respect to the real systems, relatively... 

The role of catalysis in membrane assembly is emphasized again by the above model since the N-terminal sequence of the nascent polypeptide chain of a spanning protein is released by proteolysis as soon as it reaches the cytosol. The N-terminal polypeptide chain extension may help the chain penetrate the hydrophobic bilayer and solubilize the resulting hydrophobic N-terminal part of the chain in the aqueous medium of the cytoplasm. However, the role of the protease-catalyzed hydrolysis of the polypeptide chain in membrane assembly is minimized in the membrane trigger hypothesis (99). According to this model, the essential role of the leader sequence would be to modify, in association with the lipid bilayer, the folding pathway of the protein in such a way that the polypeptide chain could span the membrane. 

Lastly a thermodynamically feasible reaction is not necessarily a commercially viable one, even if the feedstock costs are low. A second factor then comes into play, that of reaction kinetics. If a reaction is unfeasibly slow it will not be commercially viable. For example a very slow reaction may require a reactor so large it may not be economically practical. This is, of course, the role of catalysis, to speed up the rate of formation of a desired product, with a more selective catalyst speeding up the rate of formation of a desired product more than that of unwanted by-products. (We note however, that catalysis cannot change the equilibrium conversion for a reaction, as it is purely a kinetic phenomenon.)... 

Catalytica Associates, Inc. is conducting a study to produce a systematic assessment of the role of catalysis in thermochemical conversion via gasification and liquefaction. This study is also examining the potential impact of catalytic concepts under development in other areas, such as coal conversion, and new reactor technology on biomass conversion. 

We have discussed a series of examples and aspects, such as the problem of risk and sustainability assessment, tools and principles for a sustainable industrial development (in particular, the issue of scaling-down and intensification of chemical processes, and the role of catalysis), and problems and opportunities in substituting chemical and processes (also in the view of REACH legislation, and of the international chemicals policy on sustainability). These topics are expanded in the following chapters, while the final section on industrial case histories for sustainable chemical processes provides further hints on these aspects. 

From this definition, the role of catalysis to enable sustainable chemical processes... 

Catalysis is also one of the key enabling factors for the European Technology Platform of Sustainable Chemistry (www.suschem.org). A specific coordination of European innovation-driven research in the field of catalysis and sustainable chemistry has been made by the ACENET ERA-NET network (www.acenet.net) and a European N etwork of Excellence (ID EC AT, www.idecat.org) has been dedicated to the role of catalysis for sustainable production and energy. In Japan the Green and Sustainable Chemistry Network (www.gscn.net) dedicates much attention to catalysis. 

The examples shown here are industrial examples of the advantages brought about by catalysis to exploit more sustainable processes. These examples represents a real breakthrough in chemical processes, with a more than 100-fold reduction of effluents compared to the previous processes. The drastic simplification of the process (four less steps) allows a very competitive route. It is a nice example of the role of catalysis as a key for sustainability. 

This book is thus organized in three parts. The first five chapters discuss the principles and tools needed to realize a sustainable industrial chemistry. Chapter 1 discusses the general principles and emphasizes the differences between green and sustainable industrial chemistry approaches. It is also an introductory chapter to the topic. Chapter 2 discusses the role of catalysis as a main enabling factor to achieve sustainability through chemistry. Several examples of homogeneous, heterogeneous and biocatalysis are discussed, with emphasis on industrial aspects, to provide a comprehensive view of the possibilities offered by this tool. 

The role of catalysis in the petroleum industry has been equally revolutionary. Meta I-supported systems (e.g. of Topsoe and Shell) for catalytic reforming, hydrodesulfurization and hydrodenitrification, alkylation catalysts and shape selective systems (e.g. zeolites and pillared clays) for catalytic cracking (FCC) and production of gasoline from methanol (Mobil MTG) all represent significant technical and commercial achievements. 

Allen, D. T., The role of catalysis In industrial waste reduction. In Industrial Environmental Chemistry Waste Minimization in Industrial Processes and Remediation of Hazardous Wastes (A. E. Martell and D. Sawyer, eds.), p. 89. Plenum, New York, 1992. 

Chapter 1 Introduction and Structure of the Book, 3 Why Organic Synthesis Engineering, 3 The Organic Chemicals Ladder and the Role of Catalysis, 4 Process Intensification, 8 Structure of the Book, 9 Internal Organization of Chapters, 13... 

Enantioselective 1,3-dipolar cycloadditions employing azomethine ylides and asymmetric catalysis are discussed in the next chapter. The formation of chiral non-racemic pyrrolidine derivatives via dipolar cycloadditions presents an important challenge that has been successfully overcome. The role of catalysis involving different metals is also highUghted. 

Sheldon R (1993) The role of catalysis in waste minimization. In Weijnen MPC, Drinken-burg AAH (eds) Precision process technol, Kluwer, pp 125-138... 

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