Sustainable catalysis

No catalyst has an infinite lifetime. The accepted view of a catalytic cycle is that it proceeds via a series of reactive species, be they transient transition state type structures or relatively more stable intermediates. Reaction of such intermediates with either excess ligand or substrate can give rise to very stable complexes that are kinetically incompetent of sustaining catalysis. The textbook example of this is triphenylphosphine modified rhodium hydroformylation, where a plot of activity versus ligand metal ratio shows the classical volcano plot whereby activity reaches a peak at a certain ratio but then falls off rapidly in the presence of excess phosphine, see Figure... 

In order to sustain catalysis, the P450 enzymes require a reductase to supply two additional electrons from NAD(P)H needed for dioxygen activation. The nature of the reductase varies depending on the specific P450, ranging from self-contained redox cofactors such as FAD and FMN present in the same protein as the iron-heme cofactor to multi-protein systems in which separate proteins containing redox cofactors such as FAD and iron-sulfur clusters perform the electron-transfer function [12]. 

Sustainable Catalysis Without Metals or Other Endangered Elements, Part 1... 

Ionic Liquids in the Biorefinery Concept Challenges and Perspectives 37 Starch-based Blends, Composites and Nanocomposites 38 Sustainable Catalysis With Non-endangered Metals, Part 1 39 Sustainable Catalysis With Non-endangered Metals, Part 2 40 Sustainable Catalysis Without Metals or Other Endangered Elements, Part 1... 

The availability of chemical elements depends on many factors as discussed in Chapter 1 of Sustainable Catalysis With Non-endangered Metals, Part 1. With the exeeption of helium, which is too light to be held by the Earth s gravity and so is lost to spaee, ehemieal elements are not aetually being lost to planet Earth, rather they are being transferred from relatively rich ores to mueh more diluted waste sites from where, in most... 

Sustainable Catalysis Without Metals or Other Endangered Elements, Parts 1 and 2 deal with catalysts that do not possess a metal centre as part of their structure. After an introductory chapter. Chapters 2-4 cover non-asymmetric acid and base catalysis. The subsequent chapters (5-24) deal with asymmetric organocatalysis as this area has exploded in importance over the last 20 years. Again, catalysts that contain endangered elements e.g. phosphorus) have been excluded and authors were asked to highlight any examples that have other sustainable features (use of green solvent, high atom economy, etc.). 

It is vital that we seek to maximise the metals catalytic activity and recover 100% of elements from catalytic processes at both the end of reaction and end of life (the only exception may be carbon that can be burnt for energy production at end of life). Development and application of Earth-abundant catalysts for a wider range of catalytic applications is possible in the midterm. However, the long-term and ideal scenario would be that even critical elements can be used as sustainable catalysts if total recoveiy from anthropogenic cycles is guaranteed. The concept of elemental sustainability for catalysis is likely to become increasingly important in the future. Now is the time for producers and users alike to progress to circular economies and embrace sustainable catalysis. 

Contained within this book are various chapters that review the possibilities for the sustainable use of catalysts in our chemical industiy. Earth abundant metals are discussed in Sustainable Catalysis With Non-endangered Metals, Parts 1 and 2, while the options for organocatalysis are discussed in Sustainable Catalysis Without Metals or Other Endangered Elements, Parts 1 and 2. The future chemical industiy cannot survive by the use of just one of the above catalyst classes, but will require the flexibility and versatility of both. An important aspect of sustainable catalysis that is also vital for the long-term security of elements is ensuring that we establish improved methods of catalyst recovery and reuse. 

Sustainable Catalysis by Manganese Compounds From Heterogeneous Molecular Complexes to Manganese-based (NanojMaterials... 

---