Operando EPR study of automotive catalysts for NOx removal

Selective catalytic reduction (SCR) is a reaction that used in every diesel vehicle to reduce the emission of harmful NOx gas. The EU 6 emission standard calls for efficient and selective SCR catalysts that reduce the NOx emission to less than 0.080 mg/km. Though commercial catalysts for vehicle SCR have been used for a decade, the actual active site and the reaction mechanism are still not understood and under debate. Operando spectroscopy, a methodology wherein the spectroscopic characterization of materials undergoing reaction is coupled simultaneously with measurement of catalytic activity and selectivity, can probe the active site behaviours and help understand the active site behaviours. This research program aims to apply operando Electron Paramagnetic Resonance (EPR) technique in order to study and understand the Cu2+ active site for SCR. The operando EPR facility that will be developed in this research program will be one of few around world and unique in the UK. It directly probes the active sites and can quantitatively measure the status/changes of the oxidation state and coordination environment, while recording the reaction kinetics simultaneously. In this way, a structure-activity relationship of the catalysts will be established. Such facility will not only be important for catalysis, but also crucial for materials discovery in the UK. Together with operando X-ray absorption spectroscopy (XAS) and IR, the success of this program will provide fundamental understanding of the reaction and help develop more selective SCR catalysts. It is expected that operando EPR, together with other operando spectroscopies, will provide deep understanding of catalysis mechanisms in many industrially important reactions, and thus optimize the design and development of future catalysts.

The research program aims at developing operando EPR technique for optimizing SCR catalysts and reducing NOx gas emission. The potential stakeholders that can benefit from this research are: academics in catalysis/EPR/materials around world, the catalysts industry/ car industry, the transportation sector, and also the general public. This program provides deep understanding in reaction mechanisms and materials property/structure relationship for the academics in catalysis and materials. It will stimulate new characterization methodology in the EPR field.
The study of SCR reactions will provide guidance in optimizing and developing new SCR catalysts with high selectivity and stability. In particular, it helps develop SCR catalysts that work at low temperatures, which is one of the main problems with the state of art SCR technique. This will help industry to upgrade their products and gain bigger market share. By designing efficient catalysts, the use of noble metals such as Cu will also be reduced. It is an effective way to reduce the price of the SCR technique, and make it affordable to all diesel cars. Potentially, events such as the Volkswagen's emission scandal will never happen again.
JM, a UK based company, is one of the biggest company supplying SCR catalysts. JM is also the industrial collaborator of this program. It is expected that the success of this program will help their performance in the future, and therefore provide more jobs in the UK.
Efficient SCR catalysts also have huge impact in the transportation sector. Diesel has more power per volume than that of petrol, so in general the use of diesel is a more economic than the use of petrol. However, for historical reasons, emission standards for diesel are much stricter than that of petrol, e.g. USA, EU, China and Japan. By applying efficient and low cost SCR catalysts, the diesel cars in future can meet those strict standards and can compete with petrol cars in the market. This will help increase the energy utilization efficiency in the transportation sectors.
The success of this research program will also benefit the general public in the terms of better environment and improved transportation experience. The emission control catalysis aims at reducing the harmful gases, such as CO and NOx in the exhaust gas. The NOx gas not only has negative health effects but also attacks the ozone layer in the atmosphere. The low cost SCR technique will provide better transportation experience and lower charges and fees on the car emission. In the long term, this research program can also stimulate new technique that not only deal with car exhaust control, but also be applied in stationary exhaust control, such as technique for flue gas in the power plants.
In summary, the impact of this research program lies in both the economic benefits to the UK and the well-being of the people living in the country and around world.