Experimental and computational studies of the methanol synthesis catalyst – where is the hydrogen?

The synthesis of methanol from CO, CO₂ and H₂ is an enormous business - 75 million tonnes in 2015. The process uses a Cu/ZnO/Al₂O₃ (65:25:10) catalyst that was originally developed by ICI in the 1960s and operates in the range 200–300 °C and 10–100 bar. In view of its industrial importance, the catalyst has been extensively studied. There is general agreement that at low temperature the reaction proceeds by hydrogenation of CO₂ to formate and then stepwise addition of hydrogen to methanol. At high temperature, CO hydrogenation also becomes important. While the roles of CO₂ and CO have been extensively investigated and are well-characterised, the hydrogen component has been much less studied. It is generally believed that hydrogen dissociates on the copper, but adsorbed hydrogen has not been detected. H₂ dissociates on ZnO to give hydroxyls and Zn-H species, but only the former have been observed on working catalysts. The aim of this project is a combined experimental and computational study to characterise the hydrogen present on a commercial, working methanol synthesis catalyst.

This project will have a computational aspect to be carried out at the University of Lincoln and an experimental aspect to be carried out at the ISIS Neutron and Muon Facility (Harwell Campus, Oxfordshire). The computational aspect will be to use density functional theory based quantum chemical simulations to investigate the state of hydrogen on the catalyst. Initial work to provide training in the methodology will be to study the adsorption of hydrogen on the low index faces of copper and on ZnO and the Zn-doped Cu surfaces. Subsequent work will investigate extended systems that include at least two of the three catalyst components on which the detailed reaction mechanism of the methanol conversion from CO₂ will be investigated. A range of computational methods will used including lattice dynamics, ab initio molecular dynamics and time-dependent density functional theory.

The experimental work will use a commercial Cu/ZnO/Al₂O₃ catalyst. Neutron scattering methods will be employed to investigate how the adsorbates and the catalyst change with different reaction conditions and time on stream. The emphasis will be to find and study adsorbed hydrogen, so where appropriate, hydrogen on model systems such as Raney Cu or pure ZnO will also be studied. As part of this work, we will improve our ability to produce samples at a particular point along a reaction coordinate by the implementation of UV-vis spectroscopy on an existing preparation rig designed to produce the large (10-50 g) samples required for neutron scattering studies of catalysts. At a later stage in the project, we will also implement Raman spectroscopy on the same rig. We will also modify an existing system for simultaneous Raman/neutron scattering measurements to enable gas handling experiments. The upgrades to the catalyst preparation rig will be of value to other groups that also use ISIS and some collaboration with these will form part of the project.

Candidate requirements:

Applicants should hold, or expect to receive, an MSc in chemistry or an honours degree in chemistry (2.1 or higher), or the equivalent. The project will require an extended stay (12-18 months) at the Harwell campus. 

Informal enquiries are welcomed and should be directed to either Dr Arun Chutia ([Email Address Removed]) or Prof Stewart Parker ([Email Address Removed]).

More information about applying for a PhD at Lincoln may be found on our website (https://www.lincoln.ac.uk/home/course/chmchmrp/ ).

Anticipated start date: Monday 4^th October 2021.

Formal applications should be made via the University of Lincoln’s online application form for a PhD in Chemistry (https://uol.t1cloud.com/T1Default/CiAnywhere/Web/UOL/StudentCore/StudentApplicationRegistrationMyMaintenance?f=%24SC.STUAPPREG.MNT&suite=SM&ScholarshipCode=2CA-21-1).