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Meeting Report NOx REDUCTION SYMPOSIUM, 13-l 5 March 1994

ACS SPRING MEETING, San Diego, Caltfornla,

This interesting and lively symposium chaired by S K Agarwal, G M Marcelin and U S Ozkan and organised by the Petroleum DNislon of the ACS covered all the major current research topics in this field Professor AT Bell (Berkeley) introduced the topic wdh a lecture covering NO decomposition and reduction over metals, metal oxtdes and metal-exchanged zeolltes, principally Pt/A1203, V/TiOg and CU-ZSM-5, respectnrely Professor Bell addressed the problem of selectivity for Ni! versus N20 formatIon and this appeared as a recurring theme throughout the symposium Yasuda, Migamoto and Misono (Tokyo) presented an interesting comparison between Ce and C&exchanged ZSM-5 for NO reduction by propane in an oxygen rich (2%) environment In the experimental conditions employed, the Ce exchanged catalyst was more active than the Cu analog Jen, McCabe, Gotte and Parnllo (Dearborn and Philadelphia) presented a comparison of CU-ZSM5 catalysts at three drfferent copper loadings and emphasised the selective use of propene for NO reductton leadIng to Ni! as opposed to O2 reduction, leading to oxIdes of carbon LIU and Robota (Des Blaines) presented convincing evidence based on in sdu XANES characterization of CU-ZSM-5 during SCR of NO by a range of hydrocarbons, that Cu” IS a key surface intermediate and that propene IS capable of generating larger quantities of this species than propane or methane The authors presented a redox mechanism in which Cu+ acts as an active site for NO conversion Topslae, Dumesie and Topsrae (Lyngby) presented convincing evidence for the mode of interaction of NH3 wtth V/r10, catalysts These workers emphasised the role of Bransted acid sites on the supported vanadia phase for ammonia adsorption, which was much more ex-tensrve than NO adsorption Armor and LI (Allentown) presented an overview of thetr work on NO,, reduction by CHs, with particular emphasis on Cu, Co and Ga exchanged ZSM-5 catalysts An important point to emerge from this work ISthat NO IS converted catalytically to NOn by O2 as a first step in

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the mechanism, a pornt which was supported by some of the other studies presented at this symposium Burch, Mtlkngton and Walker (Reading) presented a TA P study of NO reduction by propene over Pt/AC03 wrth particular emphases on pump-probe expenments N2 production was independent of the pulse internal between the propene pump pulse and the NO probe pulse A simple redox mechanism was postulated in which NO decomposition occurs on the reduced metal leaving a Pt-0 residue, which in turn IS reduced back to the Pt metal by the hydrocarbon Overall 23 papers were presented at the 2 day symposium The general impression IS that a great deal of work, fundamental and applied, remains to be done to develop systems that are more versatile and robust than the standard V/TIO~ system This will continue as a rewarding research area for many years to come B K. HODNET-T

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