Catalysis improving society

Catalysts from design to application

Professor Avelino Corma,

Abstract

It is possible to synthesize small, medium, large and extra-large pore zeolites by means of different organic (OSDA) and inorganic structure directing agents. In the case of small pore zeolites we will show the potential of some structures for gas separation, and catalytic applications in where reactant diffusion shape selectivity plays a major role. For a most relevant catalytic application of small pore zeolites, i.e. NOx abatement in diesel mobiles, Cu-zeolite catalysts will be prepared in a single step, with the Cu perfectly distributed within the cavities. OSDAS will be presented to prepare structures  with pore topologies formed by 8X10, 9X10, 8X12,12X18,12X14 Rings. The catalytic possibilities of these types of multipore systems will be presented for cracking, aromatic alkylations, alkyl aromatic transalkylation. We will show that there are acid catalyzed reactions for which the stabilization of intermediate carbocations does not depend preferentially on acid strength but on the presence of soft counteranions. In this case zeolites are extraordinary catalysts that can work at very mild conditions without catalyst deactivation. The concept will be illustrated for the synthesis of pharmaceuticals.

Reversible electrolysis by enzymes of relevance to renewable energy conversions

Professor Fraser Armstrong FRS, University of Oxford, UK

Abstract

Renewable energy needs excellent electrocatalysts, based upon inexpensive scalable technology, for splitting water and activating CO₂ to produce fuels as well as converting fuels and oxygen into electricity. The most efficient electrocatalysts operate ‘reversibly’, i.e. they catalyse an electrode reaction in either direction without a significant overpotential being required.  An outcome of recent research has been the realisation that many redox enzymes, despite being giant, unstable molecules for which most of the bulk interior is electronically insulating, come very close to exhibiting this very special characteristic yet contain abundant elements in place of platinum metals.   An important aim is therefore to establish the particular features of an active site that make it so effective in electrocatalysis, and what part of the greater mass of surrounding material could, at least in principle, be ‘trimmed off’.  It has long been known that active sites of enzymes have all the right groups positioned in all the right places, a factor that is impossible to achieve with small metal complexes or surfaces unless the appropriate second and outer coordination shells are built into the structure.  

Protein film electrochemistry has proved to be a valuable tool for studying redox enzymes, along with genetic engineering, spectroscopy and crystallography. This lecture will summarise a few of the most interesting and significant lessons learnt so far and address some new observations that are relevant for understanding enzyme mechanism and transferring the knowledge into the design of catalysts for renewable energy conversions.

 [1] Armstrong, F. A., Hirst, J.  Proc. Natl. Acad. Sci. USA 108 (2011)14049-14054.

[2] Hexter, S. V., Grey, F., Happe, T., Climent, V., Armstrong, F. A. Proc. Natl. Acad. Sci. USA 109 (2012) 11516-11521.

[3] Woolerton, T. W., Sheard, S., Chaudhary, Y. S., Armstrong, F. A.  Energy  Environ. Science 5 7470- 7490.

[4] Hexter, S. V., Esterle, T. F., Armstrong, F. A.  PhysChemChemPhys. 16 (2014) 11822 – 11833.

[5] Bachmeier, A., Armstrong, F. A.  Current Opinion in Chemical Biology 25 (2015) 141-151.

• Listen to the audio

Surface reactions: Informing catalyst design through fundamental studies

Professor Cynthia Friend, T.W. Richards Professor of Chemistry & Director of the Rowland Institute, Harvard University, USA

Abstract

Fundamental understanding of reaction mechanisms in catalytic processes enables the design of more energy-efficient processes.  The selective oxidation of alcohols using nanoporous Au catalysts activated with a small amount of Ag is used to illustrate how understanding reaction mechanism at a molecular scale provides insight into the design of highly selective catalytic processes.  The work described spans surface science studies on both single crystals and nanoporous Au under ultrahigh vacuum conditions to flow reactor studies at atmospheric pressure.   The single crystal studies use several vibrational and X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy and temperature programmed reaction to determine the elementary steps in these reactions.  Density functional theory is used to map out the important bonding considerations in determining selectivity and van der Waal’s interactions are found to be critical.  The nanoporous materials were investigated under reaction conditions in traditional flow reactors and using Temporal Analysis of Products (TAP), a transient method.   Environmental TEM and ambient pressure XPS were used to monitor materials changes under reactions conditions as a means of understanding catalyst function and durability.  These studies provide a roadmap for linking fundamental studies to the design of catalytic processes that have the potential to reduce energy consumption.

• Listen to the audio

Rational catalyst design using DFT calculations

Professor Peijunh Hu, Queen's University Belfast, UK

Abstract

Catalysts are commonly developed by experimental trial-and-error approaches. It is one of the ultimate goals in chemistry to design rationally catalysts theoretically. In this talk, I will use two examples to illustrate that DFT calculations are very powerful to understand catalytic processes at atomic level and it is possible to rationally design catalysts in heterogeneous catalysis. 

• Listen to the audio

Catalysis for biological fuel cells

Dr Petra Cameron, University of Bath, UK

Abstract

Photo-microbial fuel cells (p-MFC) are related devices that contain photosynthetic organisms (algae or cyanobacteria) in the anodic chamber. In p-MFC, light and essential trace elements are provided to the cells but it is not necessary to ‘feed’ them organic matter. p-MFC can produce power both when under illumination when CO₂ is being reduced and in the dark when the cells respire. Unlike the majority of MFC, p-MFC can operate in the presence of oxygen in the anode.

Catalysis is central to the operation of biological fuel cells. The cells themselves act as the biocatalyst to generate electrons that are collected in the anode. The anode material is also of key importance and is often modified to facilitate electron transfer from the cells. In the case of both MFC and p-MFC, protons generated in the anodic chamber react with oxygen to form water at the cathode. A catalyst is often used on the cathode surface to make sure that water production is not rate limiting.

In this presentation MFC and p-MFC will be introduced and the role of catalysis in every part of the devices will be discussed.

Micropore structure and catalytic activity of zeolites

Professor Joaquim Sauer, Humboldt University, Germany

Abstract

Atomistic understanding of heterogeneous catalysis requires knowledge about the active sites of the catalyst and the elementary steps of the catalytic conversion. A class of catalysts for which we know much about their nanoporous framework structure and the active sites are zeolites. The lecture describes the synergy of experiment and computation for understanding Brønsted acidity of zeolite catalysts. A prominent example for the activation of small molecules at zeolitic Brønsted sites is the synthesis of hydrocarbons (olefins, gasoline) from methanol, a reaction that is industrially used [1]. Recent progress on the computational side includes ab initio calculations that yield free energies for elementary steps with chemical accuracy (4 kJ/mol) [2]. This allows examining the interplay of local acidity and surface curvature which is key to understanding the shape selective properties of these porous material. For proton exchange reactions the conclusion is reached that variations of energy barriers across different frameworks and different Al positions are determined by heats of adsorption whereas the intrinsic barriers show little variation.

Calculations for thin film model zeolites that are studied with surface science techniques [3] provide information on the limiting case of a flat surface corresponding to an infinitely large pore diameter [4].

[1]           B. Vora, J.Q. Chen, A. Bozzano, B. Glover, P. Barger, Catal. Today 141 (2009) 77.

[2]           G. Piccini, M. Alessio, J. Sauer, Y. Zhi, Y. Liu, R. Kolvenbach, A. Jentys, J.A. Lercher, J. Phys. Chem. C 119 (2015) 6128.

[3]           J.A. Boscoboinik, X. Yu, B. Yang, F.D. Fischer, R. Włodarczyk, M. Sierka, S. Shaikhutdinov, J. Sauer, H.-J. Freund, Angew. Chem., Int. Ed. 51 (2012) 6005.

[4]           J.A. Boscoboinik, X. Yu, E. Emmez, B. Yang, S. Shaikhutdinov, F.D. Fischer, J. Sauer, H.-J. Freund, J. Phys. Chem. C 117 (2013) 13547

• Listen to the audio

Designing heterogeneous catalysts for biorefining

Professor Karen Wilson, Aston University, UK

Abstract

Catalytic technologies play a critical role in the economic development of both the chemicals industry and modern society, underpinning 90 % of chemical manufacturing processes and contributing to over 20% of all industrial products. Concerns over dwindling oil reserves, carbon dioxide emissions from fossil fuel sources and associated climate change is driving the urgent need for clean, renewable energy supplies. Biomass derived from waste agricultural/forestry materials or non-food crops, offers the most easily implemented and low cost solution for transportation fuels, and the only non-petroleum route to organic molecules for the manufacture of bulk, fine and speciality chemicals necessary to secure the future needs of society. However, to facilitate such a transition requires innovations in catalyst and process design for the selective conversion of these hydrophilic, bulky feedstocks into fuels or high-value chemicals. In a post-petroleum era, catalysis will underpin bio-refinery technology, and researchers will need to rise to the challenge of synthesising chemical intermediates and advanced functional materials and fuels from such non-petroleum based feedstocks.

This presentation will discuss the challenges faced in catalytic biomass processing, and highlight recent successes in catalyst design which have been facilitated by advances in nanotechnology and careful tuning of catalyst formulation. Specific case studies will explore how the effects of pore architecture and acid strength can impact upon process efficiency in free fatty acid esterification in biodiesel synthesis and the dehydration of glucose to the important platform chemicals 5-HMF and levulinic acid.

• Listen to the audio

Catalysis and Green Chemistry

Professor Walter Leitner, RWTH Aachen University, Germany

Abstract

The principle of Catalysis is of paramount importance for the development of environmentally benign and economically successful "green" chemical processes. It offers the possibility to create value from various feedstocks and to control the chemo-, regio-, and stereo-selectivity of their transformations with small amounts of a chemical "multiplicator".

The presentation highlights how the scientific advances in catalysis research at the interface of molecular and engineering sciences directly impact on the dynamic development of energetic and chemical supply chains. The use of CO₂ as carbon source, the valorization of biomass for tailor-made fuels and chemicals, and the development of continuous-flow processes for the production of pharmaceutical products will be used to illustrate these general aspects with examples from ongoing work in our laboratories.

• Listen to the audio

Catalysis for in situ repairs of structural composites

Professor Duncan Wass, University of Bristol, UK

Abstract

Carbon fibre-reinforced composite materials are increasingly replacing traditional materials in the aerospace and automotive industries. These materials are extremely stiff and lightweight - but can suffer from damage that is difficult to detect and repair. We have been exploring the use of catalysts embedded within composite structures to impart autonomous self-healing functionality. Our approach is centered on the use microcapsules containing a monomer that is ruptured after damage, leading to contact with the catalyst and polymerisation/healing. Recent progress, including catalysts that are activated by the damage event itself, and opportunities for application will be discussed.

• Listen to the audio

Emission control

Professor Louise Olsson, Chalmers University, Sweden

Abstract

This presentation will focus on results from combining experiments and kinetic modelling for reducing emissions from vehicles using catalysis. It is crucial to decrease the emissions of CO₂, since it is a greenhouse gas that may increase the global warming. When using oxygen excess during combustion the fuel economy is significantly improved and thereby reducing the CO₂ emissions. This is the case for diesel engines and lean burn gasoline engines. The catalytic system after a diesel engine is today very complex. One possible configuration is to start with a diesel oxidation catalyst (DOC), followed by a diesel particulate filter (DPF) for removing the particles. After this a NO_x removal system is added. There are different concepts for removing NO_x in oxygen excess, where selective catalytic reduction (SCR) is an important method. For this technique, urea is dosed into the exhaust system, where it decomposes and hydrolysis to form ammonia. The produced ammonia reacts selectively with NO_x over the catalyst. In this presentation results for hydro-carbon and NO_x removal using heterogeneous catalysis will be shown. It is critical for the automotive industry that these materials have high durability and therefore a special emphasis will be on deactivation and regeneration of these catalytic materials.

Design and evolution of biocatalysts for organic synthesis

Professor Nicholas Turner, University of Manchester, UK

Abstract

This lecture will describe recent work from our laboratory aimed at developing new biocatalysts for selective organic synthesis, with a particular emphasis on the application of engineered biocatalysts for the conversion of inexpensive starting materials to high-value products. By applying the principles of ‘biocatalytic retrosynthesis’ it is possible to design new synthetic routes to target molecules in which biocatalysts are used in the key bond forming steps. For example, monoamine oxidases (MAO-N) are a class of enzyme that catalyze the (S)-selective oxidation of amines to imines. MAO-N biocatalysts have been engineered to generate enantiomerically pure chiral amines by deracemisation or desymmetrisation of appropriate substrates. Recently, new variants of MAO-N have been developed via a combination of directed evolution and rational design in order to broaden the enzyme’s substrate specificity. These new variants have been used for the deracemisation of primary and secondary amines such as (R)-4-chlorobenzhydrylamine (building block for the synthesis of Levocetirizine), (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline (for the synthesis of Solifenacin) and the two alkaloids (R)-Harmicine and (R)-Eleagnine. The integration of several biocatalytic transformations into multi-enzyme cascade systems (systems biocatalysis) has also been a focus of recent studies. In this context various biocatalysts have been employed in combination with other bio-/chemo-catalysts in order to complete a cascade of catalytic reactions. Engineered biocatalysts that can be used in this context include -transaminases, phenylalanine ammonia lyases, amine dehydrogenases, imine reductases, carboxylic acid reductases and amine oxidases.

• Listen to the audio

Experiment and computation in the discovery of new catalysts

Professor Matthew Rosseinsky FRS, University of Liverpool, UK

Abstract

A high-throughput materials discovery approach to identify Fischer-Tropsch catalysts (Boldrin, Chemical Science 2015) that combines direct measurement of stability with proxy measurement of activity and selectivity is presented. Such approaches enable rapid hypothesis testing, but are reliant on the quality of the knowledge and understanding that generates these hypotheses. Computation offers a route to identify candidate functional materials for synthesis and thus inform library design. I will describe an approach that builds chemical knowledge into crystal structure prediction, and exemplify it in the identification of a new solid oxide fuel cell cathode where the key components for electrocatalytic activity are built in to the materials design (Dyer, Science 2013).

• Listen to the audio

Developing catalysts to prepare polymers from renewable sources

Professor Charlotte Williams, University of Oxford, UK

Abstract

The lecture will describe recent research into homogeneous metal catalysts for ring-opening polymerizations and ring-opening copolymerization reactions.  The development and application of a series of dinuclear metal complexes, focussed on Zn(II) and Mg(II),  as catalysts for carbon dioxide/epoxide copolymerization will be presented.¹ These catalysts show unexpectedly high activities, under low pressure conditions, to selectively produce polycarbonate polyols. The polymerization kinetics and detailed studies of the catalysts will be presented. Finally, the application of the dinuclear catalysts for a new type of sequence selective catalysis, whereby tailored block copolymers are prepared from mixtures of monomers, will be described. The principles (kinetics) which under-pin the monomer selectivity will be presented and opportunities to apply this catlaysis more broadly will be highlighted.

1. (a) Paul, S.; Zhu, Y. Q.; Romain, C.; Saini, P. K.; Brooks, R.; Williams, C. K. Chem. Commun. 2015, 6459-6479; (b) Saini, P. K.; Romain, C.; Williams, C. K. Chem. Commun. 2014, 50, 4164-4167; (c) Romain, C.; Williams, C. K. Angew. Chem. Int. Ed. 2014, 53, 1607-1610; (d) Bakewell, C.; White, A. J. P.; Long, N. J.; Williams, C. K. Angew. Chem. Int. Ed. 2014, 9226 –9230; (e) Kember, M. R.; Williams, C. K. J. Am. Chem. Soc. 2012, 134, 15676-15679.

Synthesis of new materials

Professor C N R Rao, Jawaharlal Nehru Centre for Advanced Scientific Research, India

Abstract

Artificial photosynthesis is a promising method for producing renewable energy by use of sun light. Artificial photosynthesis employing the modified Z-sheme of natural photosynthesis can be exploited both for the oxidation and reduction of water. Oxidation of water is successively achieved by the use of cobalt and manganese oxides with the cations in the 3+ state with one e_g electron.^1,2 Hydrogen can be produced by the dye-sensitized photochemical process3 or by the use of semiconductor heterostructures4. In this presentation, ways of splitting water will be presented, followed by recent results obtained on the photochemical generation of hydrogen by different strategies specially those involving semiconductor heterostructures of the type ZnO/Pt/CdS⁴ or nanosheets of chalcogenides ^3,5 such as MoS₂ and MoSe₂. Other novel strategies for hydrogen generation such as the solar-thermal route based on oxides⁶ will also be examined.

U. Maitra, B.S. Naidu, A. Govindaraj and C.N.R. Rao, PNAS, 110, 11704 (2013).

B.S. Naidu, U. Gupta, U. Maitra and C.N.R. Rao, Chem. Phys. Lett. 591, 277 (2014).

U. Maitra, U. Gupta, M. De, R. Datta, A. Govindaraj and C.N.R. Rao, Angew. Chem. Int. Ed. 52, 13057 (2013).

S.R. Lingampalli, U. Gautam and C.N.R. Rao, Energy Environ. Sci. 6, 3589 (2013).

U. Gupta, B.S. Naidu, U. Maitra, A. Singh, S. Shirodkar, U.V. Waghmare and C.N.R. Rao, Appl. Phys. Lett. (Materials), 2, 092802 (2014).

S. Dey, B.S. Naidu, A. Govindaraj and C.N.R. Rao, Phys. Chem. Chem. Phys. 17, 122 (2015).

• Listen to the audio