Title: Tuning zeolitic parameters for the trapping and elimination of pollutants and toxic gases - application in automotive cold-start and nuclear safety

Bruno Azambre

University of Lorraine, France


Bruno Azambre is 45 years old and is Associate Professor (Hab.) at University of Lorraine – Institut Jean Barriol (France). After of a PhD thesis in Metz devoted to the catalytic/sorption properties of functionalized carbons (2000), he worked as post-doc at University of Reading (UK) on inorganic nanotubes. When in 2003 he became a permanent lecturer, he examined the reactivity of pollutants with sorbents/catalysts in numerous fields such as automotive depollution, AOP’s, nuclear safety and others. His works are devoted to the design, surface characterization, testing of reactive materials (zeolites, rare-earth oxides, carbons, mesoporous materials) and the elucidation of complex mechanisms by in situ/operando spectroscopies. He is co-author of about 60 publications and 100 communications.


The development of new trapping and abatement strategies is key in order to avoid the dissemination of harmful pollutants and toxic substances into the environment. By comparison with physisorption-related processes, irreversible trapping generally involves chemisorption or catalytic reactions of the targeted molecules on the active sites of specifically-designed materials. Well-known applications include for instance the trapping of NOx and SOx or the catalytic elimination of diesel soot in DPF. In these last years, new applications are emerging. A key target to reduce current hydrocarbon (HC) emissions from automotive exhausts is to improve their abatement under cold-start conditions, which mostly arise during the first two minutes of the driving cycle. One of the most promising after-treatment technology is to trap the HC at low temperatures on a sorbent, typically a zeolitic material, which can be combined with an oxidation or a deNOx catalyst, so that the desorbing HC can be easily burnt at higher temperatures or alternatively reduce nitrogen oxides. In that respect, the zeolitic material has to be not selective to the type of HC (i.e. propene, toluene and decane) and the HC desorption temperature has to be high enough to match with the light-off temperature of the oxidation or DeNOx catalyst. Another emerging application for zeolitic materials is their use as iodine trap in the context of a severe nuclear accident (Fukushima-like). In that respect, it has to be ensured that no radioactive iodine could be released from the filter under dynamic flowing conditions over a long period. Stable trapping could in principle be obtained using specifically-tailored silver zeolites thanks to the formation of AgI precipitates involving the catalytic transformation of CH3I and I2 on silver sites. In both applications, the zeolitic filter has to withstand the presence of inhibitors (H2O, COx, NOx…) and maintain its properties over a wide range of temperatures. 
In this presentation, we will see how it is possible to finely tune the zeolitic parameters, such as the pore size and connectivity, the Si/Al ratio, the nature and content of compensating cations in order to meet the above-mentioned requirements in both applications. A screening of several zeolitic sorbents will be presented thanks to a quantitative evaluation of multiple breakthrough curves, TPD and TPSR data. Characterization of the materials before and after test, as well as the use of in situ diffuse reflectance spectroscopies (DRIFTS and DRS-UV-Vis) will provide important insight on the nature of active sites and the complex network of reactions associated with the storage and decomposition of trapped molecules under representative conditions.

Audience Take Away:

•    From an application viewpoint, the audience will learn important aspects relevant to: (i) the removal of unburnt hydrocarbons emitted in the cold-start phase of light vehicles ; (ii)  the trapping of radioactive iodine in the context of a nuclear accident. From a methodological viewpoint, this talk will give insights into the tailored design an adsorbent/catalyst for a targeted application and the unravelling of surface mechanisms by after-test characterization and in situ spectroscopies.  
•    This presentation should help to unravel the effects of  the  zeolitic framework,  the nature of exchanged metal ion and the preparation method on the trapping of pollutants when present alone or in complex mixtures. General guidelines will be provided to understand the factors playing a role on the adsorption selectivity and/or catalytic decomposition to by-products, pore blocage etc...  A list of the more appropriate for the above-listed applications  will be given on a rational basis. Links to other relevant processes, such as catalytic oxidation, NOx-SCR for automotive cold-start and methanol to olefins (MTO) for CH3I trapping will be given.