Joe Howard's Research Group

[Dr Joseph Howard took up a lectureship in inorganic chemistry at Durham in October 1978 and left in April 1986, declining a readership effective from October that year. He chose instead an industrial career, which began at Wilton with the New Science Group of Imperial Chemical Industries as a research manager. He lives in the USA.]

Group members, by year of joining (Each postgraduate listed obtained the qualification shown.)

1978 Douglas Graham Ph.D. (In 1977 on October 1, DG started a Ph.D. study period of 36 months full-time: 12 months' supervision by Tom Waddington Tom Waddington's Research Group, then joint supervision); 1979 Ian J. Braid and Z. AbdulKadir Ph.D.s (i.e. on October 1 started a Ph.D. study period of 36 months full-time); 1980 Asia L. AlNoaimi M.Sc. (i.e. on January 1 started an M.Sc. study period of 12 months full-time); 1981 Anthony Royston (Departmental graduate-level support in electronics from May, 60 months, shared with Departmental duties), Keith Robson (postdoctoral, transferred in May from Tom Waddington's group, 5 months), Keith P. Brierley (research assistant, transferred in May from Tom Waddington's group, 5 months); 1982 Jacqueline M. Nicol Ph.D.; 1983 Robert W. Jackson (postdoctoral for 30 months), Neil J. Everall Ph.D. [supervision transferred to Robin Harris Robin Harris' Research Group on 1 April 1986]; 1984 Kenneth Hutchinson (postdoctoral for 18 months).

Joe Howard, writing in 2013 (February-May) recalls his research activity at Durham.

Research is a cooperative activity. This article gives an opportunity to recognise the contributions of my scientific co-workers and collaborators. Their friendship, enthusiasm, creativity and sheer hard work are all deeply appreciated. Co-workers and collaborators who contributed in detail are named in the text; additionally I recall with gratitude the general advice, guidance and fruitful discussion in many contacts with David Clark, Jim Feast, Cliff Ludman, Tom Waddington, Ken Wade and Jack Yarwood.

My PhD thesis research had focused on vibrational spectroscopic studies of adsorbed molecules, mainly by inelastic neutron scattering (INS). The specific sensitivity of INS to the hydrogen atom enables this technique to readily differentiate hydrogen-related vibrational modes. This work was underpinned by studies of inorganic and organometallic complexes that served as models for the adsorbed species. As a staff member, I planned to extend this initial work to a broader range of physical systems, including catalytic systems of industrial importance, and to probe them more deeply by diversifying the range of physical methods used. I was also determined to continue with my own experimental and theoretical research programmes.

This was a terrific time to be involved in neutron scattering. Relatively few chemists were using inelastic techniques and several major new national facilities were becoming available or under construction (LINAC at Harwell, ILL at Grenoble, LANCE at Los Alamos, SNS at RAL - the Rutherford Appleton Laboratory, Chilton). The new facilities and their instruments hugely extended the resolution, energy range, S/N (signal-to-noise) ratio and beam intensities available, thus increasing the opportunities for new research. This was particularly important for our adsorbed-species work, which was marginally feasible on the older generation of facilities. My interest in instrument design and building grew from my extensive involvement in the specification and evaluation of some instruments for the new neutron sources and my responsibility for those instruments.

I collaborated extensively with Tom Waddington Tom Waddington's Research Group and his students - John Tomkinson, Chris Ratcliffe, Keith Brierley, Keith Robson - as well as with Cliff Ludman Cliff Ludman's Research Group on two main research areas. The first was low-wavenumber (0-600cm-1) infrared (IR), Raman (R) and INS studies of a range of organic, organometallic and inorganic molecules [such as anilinium halides, alkali-metal methanesulphonate salts, C2Cl6, Co2(CO)6C2H2, Cr(C6H6)2, C6H6Cr(CO)3], where the interest was in the torsional modes not visible in the IR and R spectra. The second main area was hydrogen-bonded systems [such as KHCO3, CsH(NO3)2, MH(CO2CX3)2 (where M=Na, K; X=F, Cl), MFHF (where M=Na, K)] in which the complexity of the IR and R data rendered definitive assignment of the hydrogen-bonded vibrational modes extremely difficult at best.

Ian Braid extended the INS work. We studied cyclo-C3H6 adsorbed on partially ion-exchanged Mn(II) and Co(II) type A zeolites; H2O, as a function of coverage, on Ca-A zeolite; and C2H2 on Ni(II)-exchanged Y zeolite. Applying his expertise in computing and his interest in theory, he completed an extremely detailed INS study and analysis of the dynamics of hydrogen and deuterium molecules adsorbed on partially Zn(II)-exchanged A zeolite. Ian utilized the increased energy range of the new facilities to study hydrogen molecules adsorbed on zinc oxide (Kadox 25) and “impure” palladium black.

Doug Graham, with enthusiasm and skill, synthesized significant quantities of numerous transition-metal hydridocarbonyls and studied them using IR and R spectroscopy and also over the equivalent of the whole far-IR and IR ranges using INS. Without the limitations of optical selection rules, we were able from INS spectra to characterize fully the vibrational modes of hydrogen in significantly different bonding environments. This was important for the INS study of the adsorption of hydrogen on powdered metals. Doug completed the INS work Keith Robson had started on benzene complexes and extended it to the adsorption of benzene on Ag-13X zeolite and on platinum black. Spectroscopic studies of a range of tropyllium complexes were also completed.

I was interested in extending our work on zeolites to practical catalytic regimes of temperature and pressure and to do time dependent studies with the objective of following catalytic reactions and structural changes within in the zeolite frameworks. IR was the technique chosen for this work. Zahrah Abdul Kadir initially focused on developing techniques and equipment for the study of unsupported zeolite catalysts using IR spectroscopy. She developed IR cells that enabled controlled dehydration of the thin self-supporting zeolite discs at temperatures up to 650 K as well as the in-situ adsorption of gases under well defined conditions of temperature and pressure. I want to acknowledge the tremendous support provided by the staff of the Science Laboratories Workshops in the design and fabrication of this equipment, and a lot more, while I was at Durham. Using these new facilities, we learned a huge amount about the structural changes that take place in zeolites on ion exchange and progressive dehydration. Zahrah extended these techniques to studying the adsorption of small molecules (C2H2, C2H4, NH3, CO, H2S) and characterized the several different potential adsorption sites within transition-metal exchanged zeolite frameworks. She was the first to follow the changes that occur in structure and reactions as sample temperature is increased.

Using the equipment Zarah had developed, Asia Nasser Al Naoimi , as an M.Sc. student, investigated the adsorption of hexene-1 and n-hexane and the dynamics of the poisoning, through coke formation, of some Y-zeolite catalysts at elevated temperatures. She also studied H2O and D2O adsorption and the structural effects of progressive hydration and dehydration on Co(II) A zeolite frameworks.

Jackie Nicol joined the group to focus on the study of reacting species using IR (although she ran INS projects too). All the IR work up to that time, including her initial studies, was carried out on a dispersive spectrometer. Jack YarwoodJack Yarwood's research group and I were extremely fortunate to have British Gas donate a new Nicolet 60SX FTIR spectrometer. Its terrific capabilities (S/N ratio, data collection and data analysis software) proved invaluable to Jackie and me in following the evolution with time of structural changes in zeolites (e.g. cation migration) and catalytic reactions within the frameworks as a function of temperature and pressure. With greater capability came much greater complexity and this time-resolved work demanded extremely careful planning, meticulous attention to detail and relentless data analysis. Jackie’s study of zeolites covered the following areas: dehydration and its effects on cation location, rates of cyclo-C3H6 isomerization and the identification of specific reaction sites, autoreduction in Cu(II) zeolites, Cu(I) carbonyl complex formation, NH3 adsorption and reactions of C2H2 at specific cation locations. The Nicolet allowed collaboration with Jack and his Ph.D student Peter Lux in a study of the reactions of CH3OH and C2H4 within the hydrogen-exchanged framework of ZSM-5-zeolite framework, which had been patented by the Mobil Oil Company because it oligomerises light olefins to high-octane gasoline.

The Raman spectra of most zeolites, especially transition-metal ion-exchanged zeolites, are swamped by fluorescence. However, the duration of a Raman signal is slightly shorter than that of its accompanying fluorescence signal. Three weeks at UCLA with Prof. M Nichol’s picosecond-pulsed laser system convinced me of the feasibility of utilizing that difference in duration to obtain a S/N ratio suitable for spectroscopic analysis. The difference could be exploited by fast electronic gating and time discrimination. That proof of concept led to a grant of £110,400 from the Science and Engineering Research Council (now EPSRC) to build and evaluate a time-resolved picosecond-pulsed laser Raman spectrometer for fluorescence discrimination. In 1 ps, light travels just 0.3 mm in vacuum; the project was going to be immensely challenging, particularly as every component from the laser to the fast-gating electronics was itself under development! Over time there were four key players. The challenge of assembling and operating the initial system was taken on enthusiastically by Bob Jackson, a postdoctoral research assistant (PDRA). Invaluable support on complex electronics issues was received from Tony Royston. Bob was joined by Ken Hutchinson (PDRA), who contributed his extensive Raman experience in several key areas, and by Neil Everall. In addition to his experimental work, Neil applied his skills in mathematics and critical thinking to develop a creative and sophisticated theoretical analysis of the complete system and a model for it. This proved invaluable for system optimization. He was then able to use the same approach for several alternative fluorescence discrimination systems and evaluate their potential effectiveness, pointing the route to further research. With a grant of £90,000 from the Ministry of Defence, the team was able to purchase additional equipment and develop a system that used an intensified multichannel diode array detector to replace the gated photomultiplier tube used in the original system. Once again pioneering work on the performance and operating characteristics of these multichannel detectors (at that time mainly used by astronomers to study very weak stars) surprised the experts in the field.

I was fortunate to collaborate on five separate projects involving theoretical calculations and experimental work on INS band intensities, including overtones. I worked variously with Andrew Taylor (RAL and LANCE), John Tomkinson (RAL), Brian Bolland (RAL), Juergen Eckert (LANCE), Joyce Goldstone (LANCE) and Jackie Nicol. This was important for enabling the identification and assignment of INS bands at the high wavenumber ranges newly available and to facilitate the application of normal coordinate analysis to INS spectra. This work was mainly done on solids, but included the first complete study of a liquid-phase system (CHCl3 in solution). A publication with Andrew Taylor (RAL) gave theory and practice for correlation of INS frequencies of bands in experiments using a beryllium filter detector spectrometer so that they corresponded with IR and Raman data.

Neutron scattering (such as quasi-elastic scattering or the observation of tunnelling transitions at very low wavenumbers) provides very sensitive methods for the detailed investigation of molecular dynamics. I collaborated with Rob Richardson (Bristol) in a study of NH4+ ion motion in NH4ReO4 to explain some highly anomalous NQR results. Rob and the Durham team also completed a longstanding project on the ring dynamics of ferrocene, nickelocene and ruthenocene.

Matrix isolation was of considerable scientific interest at the time. With an international team, headed by Jim Morrison (McMaster University, Canada) and including John Tomkinson, my group completed a definitive multi-technique study of the complex dynamics of the motion of the NH4+ ion when matrix-isolated in alkali-metal halide lattices at low dilution. We identified and characterised tunneling and torsional states. With Tom Waddington and his research assistant Keith Brierley, the group explored the dynamics of the BH4- ion, similarly isolated in alkali-metal halide lattices, over a range of dilutions.

Work with Jackie Nicol (by then in Maryland at the National Bureau of Standards) and Juergen Eckert successfully probed the detailed dynamics, including rotational and vibrational modes as low as 30 cm-1, of molecular hydrogen adsorbed on cobalt-exchanged sodium A zeolite. The same group, with contributions from Frans Trou (Argonne National Laboratory), completed related work on a calcium-exchanged zeolite. These studies complemented earlier inelastic studies in collaboration with Ian Braid and John Tomkinson.

Over several years John Tomkinson (Durham, RAL) and I became increasingly involved with research into hydrogen-bonded systems as new INS instrumentation increased the range of frequency attainable. For example, with T Brun (Argonne National Laboratory) we completed an inelastic scattering study of a single crystal of potassium hydrogen malonate; by changing the crystal’s orientation with respect to the incident neutron beam we identified the hydrogen-bond vibrational modes, as each change altered their intensity. Juergen Eckert, Joyce Goldstone and Andrew Taylor (all at LANCE) joined us to study a range of intramolecular hydrogen-bonded complexes; a new correlation between the out-of-plane bending mode γ(OHO) and the oxygen-oxygen distance R(OO) was determined.

A project that was incomplete when I left Durham was started with my Chemistry colleagues David Clark David Clark's Research Group and Graham Beamson (senior demonstrator), and with Brian Tanner (Physics). With funding from a major scientific equipment company we began to design a laboratory EXAFS spectrometer and evaluate its feasibility. The project was continued in industry.

(Joe Howard's appreciation of Tom Waddington is at Tom Waddington's Research Group and memories that are more general are at Decades under The 70's.)

research_groups/dr_joseph_howard.txt · Last modified: 2016/05/26 14:32 (external edit)
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