Copper exchanged zeolites for ammonia reduction of NOx from biogas gas engines

The motivation for this study arises from the opportunity to gasify renewable sources of biomass (e.g. forestry and farming residue, municipal waste), to obtain biogas (H2, CO, CO2, N2, HCs) which can be used as a fuel in gas engines. A major challenge is to develop appropriate catalytic technology for the treatment of exhaust gases from the engine, to meet the new European Waste Incineration Directive (WID) for this type of a process. So called structured reactors based on metallic short channel structures with enhanced mass and heat transport [ ], are able to considerably shorten the reactor length and combat issues experienced with current DeNOx technology, namely ammonia-selective catalytic reduction (SCR), including the size of the cleaning installation and ammonia slip. In line with the requirements stated by the structured reactors and the NH3-SCR process are copper-exchanged zeolites, which are known for their remarkable activity in the reduction of nitrogen oxides [ ] (Figure 1). Use of the steamed form of zeolite Y as a matrix for the copper cations should lead to the active catalyst having both Cu+ and H+ cations acting as active centres in the DeNOx process. Additionally, the steaming process should form mesopores facilitating reagents transport, and should stabilize existing acidic centres, protecting them from further decomposition under the harsh conditions of the catalytic reaction. The catalyst was examined by XRD and the types of active centres present within the zeolite structure were checked by in situ FTIR adsorption and desorption measurements using pyridine, NO and CO as probe molecules. The surface of the deposited catalysts was analysed with the standard SEM/EDX method, to verify the distribution of the material, and the coupled system of AFM and confocal Raman microscope to investigate the structure and dispersion of the material. The catalysts were tested in the reduction of NO and NO2 with ammonia in a gradientless reactor to derive kinetic parameters. The results allowed for the advanced correlations of the catalyst to establish fundamental structure-performance relationships.

1. A. Kolodziej and J. Lojewska, Catalysis Today, 2009, 147, S120-S124.
2. P. Pietrzyk, B. Gil and Z. Sojka, Catalysis Today, 2007, 126, 103-111.