© 2015 Cardiff Scientific Society


Since the late 1960s there has been concern about the deterioration of urban air quality due to emissions from car engines.  The main pollutants are hydrocarbons, carbon monoxide and nitrogen oxides.  These can be removed using catalysts in processes which are controlled by powerful computers   

Recently, advances with high performance diesel engines have made them very popular. In these, treatment of nitrogen oxide emissions by converting them to nitrogen, as is the case in petrol engines, is impossible.  Two processes are used: “NOx-trapping” which involves periodic catalytic regeneration and  selective catalytic reduction with ammonia derived from urea.  Diesel engine combustion produces more soot than petrol engines and filters are fitted so that it does not enter the environment.  These must be cleaned periodically by burning, controlled by computers so that ignition of the soot is achieved (550oC is needed) without any high temperature events.  How this is done and other aspects of how emissions from both petrol and diesel engines have been reduced will be discussed.    

7 October 2009 Large Chemistry Lecture Theatre, Cardiff University

Cleaning the Air we Breathe – Controlling Emissions from Passenger Cars

Dr Martyn V. Twigg
Chief Scientist, Johnson Matthey