Professor Chris Hardacre

Professor C.Hardacre
BA (University of Cambridge), 1990
MA (University of Cambridge), 1994
PhD (University of Cambridge), 1994

Head of School
Chair of Physical Chemistry
Tel:     + 44 (0) 28 9097 4592
Fax:    + 44 (0) 28 9097 6524
E-mail: c.hardacre@qub.ac.uk

 

Research Keywords

Heterogeneous Catalysis
Synchrotron Radiation
Catalytic Organic Transformations
Structure-reactivity correlations
Ionic Liquids

Publications

 

Research

Our research is broadly centred on the use of catalysts in both liquid and gas phase reactions, the structure of materials and the use of ionic liquids for chemical processing. The group has strong industrial collaborations through CenTACat and QUILL and with a number of external academic groups including Richard Compton (University of Oxford), Alan Soper/Daniel Bowron (RAL), Ray Allen/Jordan MacInnes (University of Sheffield), Simon Doherty (University of Newcastle), Margarida Costa-Gomes (Université Blaise Pascal (Clermont-Ferrand II)), Lynn Gladden (University of Cambridge) and Vasile Parvelscu (University of Bucharest).

Understanding Gas Phase Heterogeneous Catalysis.

One of the biggest challenges in any type of catalysis is a true understanding of the catalytic process and the nature of the active site. Transient or time resolved techniques can aid this process by studying the catalyst under real conditions by using small gas pulses to probe the surface without altering it. Using transient kinetics allows detailed mechanistic information to be obtained. We use TAP techniques coupled with in-situ studies using IR and diffraction techniques to understand a range of reactions including water gas shift, selective oxidative dehydrogenation and isomerisations. A typical TAP experiment is shown below.

Schematic of a time resolved gas pulse over a catalyst bed.

Structure of materials

It is not only important to study the reactive chemistry of catalysts but also understand their adsorption /electronic/ structural properties as well. In many cases the structure of the catalyst surface for example has at least as great effect on the reaction as the specific chemical composition of the material. Our research investigates not only the reactions but how the material properties change the reactivity. The adsorption/electronic properties are investigated using a range of techniques including XPS and thermal desorption spectroscopies. Much of the structural investigations involve the use of synchrotron radiation. We have concentrated on the use of EXAFS to investigate the local structure of a variety of materials both in-situ transformations in a reactive medium and ex-situ. Many of the experiments require the designing and building of in-situ reaction cells and we have developed a new cell for the study of ionic liquids using EXAFS (SRS annual report.pdf). Studies have been performed on conducting polymers, adsorbed aqueous organic and metal species on hydroxide surfaces, catalysts (see below) and organometallic compounds.

Schematic of the transformation of a Au/CeZrO4 catalyst during the water gas shift reaction.

Ionic Liquids

These are liquids comprised solely of ions but are liquid at room temperature.  Why are they interesting?  The chemistry within them is nearly always distinct from organic solvents, for example higher selectivity or activity.  They have no vapour pressure and so direct distillation is easy and there is no waste from VOC emissions.  These systems are easy to recycle and have the advantage that they retain the catalyst used in its active state without leaching into the product phase.  Most importantly, there are an infinite number of ionic liquid systems and with an understanding of their properties become designer solvents.  Being able to tailor the solvent properties to the reaction means that they have the potential to revolutionise the chemical industry.  This has led to the formation of the Queen’s University Ionic Liquid Laboratory (QUILL) which is a University-Industry multidisciplinary research centre, supported by a range of national and multinational companies.  A wide range of catalysed and uncatalysed-reactions have been performed in our laboratory in ionic liquids including hydrogenation, oxidations, Friedel-Crafts, Heck and oligomerisations/polymerisations, phosphorylations.  The ionic liquid provides an ionic environment for solutes as opposed to molecular solvents and this can control the activity and selectivity of reactions.  For example, water can be deactivated in ionic liquids compared with conventional solvents leading to increased stabilisation with respect to hydrolysis of sensitive reagents such as PCl3 – play movie

In addition, we have been examining the structure of the liquids and solute-solvent interactions (see insert) using neutron and X-ray diffraction at the Rutherford Appleton Laboratory (RAL annual report.pdf) and Daresbury Laboratory (SRS annual report.pdf), respectively.  For example, using neutron diffraction comparisons of the anion distribution around the central cation can be obtained and related to the anion size and hydrogen bonding capability.  This information allows us to predict solvation behaviour and understand reaction properties (selectivity and reactivity).

(a) Dimethylimidazolium cation and (b) Hexafluorophosphate anion probability distribution around the hexafluorophosphate anion in 1,3 dimethylimidazolium hexafluorophosphate.

Chemistry/Chemical Engineering

In the chemical industry chemistry and chemical engineering are equally important and yet few chemists have any knowledge of engineering and vice versa. We study chemistry in both conventional and novel media and develop systems which may be easily scaled up. This has included the understanding of gas-liquid-solid and liquid-solid reactions using online spectroscopy, calorimetry and a range of reactor designs such as microchannel reactors, CSTR, plug flow systems and a rotating disc reactor. This combined approach has led to significant progress to be made in the hydrogenation of sulfur containing molecules, see below, using heterogeneous palladium catalysts which had previously been thought to be impossible.

Reaction pathways for the hydrogenation/hydrogenolysis of 2,2´-, 3,3´- and 4,4´-
dinitrodiphenyldisulfides using heterogeneous palladium catalysts.