This book is a printed edition of the Special Issue "Selective Catalytic Reduction of NO_x" that was published in Catalysts

The First International Nitrogen Conference provided an opportunity for researchers and decision-makers to exchange information on environmental pollution by nitrogen compounds on three scales: global, continental/regional and local. The main topics were air, ground water and surface water pollution; emission sources, atmospheric chemistry, deposition processes and effects; disturbance of nitrogen cycles, critical loads and levels; assessments, policy development and evaluation; target groups and abatement techniques; and new approaches leading to an integrated abatement strategy.The peer-reviewed papers from the Conference presented in this volume will provide readers with a comprehensive review of the transport, deposition and impact on ecosystems of nitrogen.

The most efficient process to reduce NOx emissions from lean exhaust gases, selective catalytic reduction (SCR) with ammonia, has undergone tremendous development over the past decades. Originally only applied in stationary power plants and industrial installations, SCR systems are now installed in millions of mobile diesel engines, ranging from off-road machineries, to heavy-duty and light-duty trucks and passenger cars, to locomotives and ships. All of these applications involve specific challenges due to tighter emission limits, new internal combustion engine technologies, or alternative fuels. Three review articles and 14 research articles in this book describe recent results and research trends of various aspects of the SCR process. Reaction engineering aspects, such as the proper dosage of ammonia or urea, respectively, are as important as further developments of the different SCR catalysts, by deepening the understanding of their functionality or by systematic improvements of their properties, such as low-temperature activity, selectivity, or poisoning-resistance. Another covered aspect is cost reduction through the use of cheaper base materials for the production is active and stable SCR catalysts. Finally, research efforts are reported to develop SCR processes with different reducing agents, which would open doors to new applications in the future. The range of topics addressed in this book will stimulate the reader's interest as well as provide a valuable source of information for researchers in academia and industry.

Nitrogen oxides, NOx (NO+NO2), are considered significant air pollutants. Selective catalytic reduction of NOx with NH3 (NH3-SCR) is a leading technology candidate for NOx emissions control for diesel engine vehicles. Recently, the Cu-exchanged chabazite framework type zeolite with small pores, such as SAPO-34 and SSZ-13, has received a great deal of attention due to exceptional hydrothermal durability and enhanced SCR activity. I have carried out a systematic study over both Cu-SAPO-34 and Cu-SSZ-13 catalysts to elucidate the reaction mechanisms, acid properties, Cu structures, active centers and deactivation modes. First, the intrinsic mechanism of the SCR reaction over a Cu-exchanged SAPO-34 catalyst at low temperature was studied by in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), coupled with a mass spectrometer to measure inlet and outlet gas concentrations. The evolution of the surface intermediates, as well as the reactivity of NH3 with surface NOx species and NOx with surface NH3 species, was evaluated. Second, a series of SAPO-34 catalysts with various Cu loadings (ranging 0.7-3.0 wt%) was prepared by a solid state ion exchange method (SSIE). The acid properties as well as the Cu structures were characterized by XRD, NH3-TPD, UV-vis, DRIFTS and H2-TPR. Third, a SSIE method was developed to synthesize Cu-SSZ-13 catalysts with excellent NH3-SCR performance and durable hydrothermal stability. After the SSIE process, the SSZ framework structure and surface area was maintained. DRIFTS and NH3-TPD experiments provide evidence that Cu ions were successfully exchanged with Brønsted acid protons in the pores. Fourth, the hydrothermal stability of Cu-SAPO-34 and Cu-SSZ-13 was studied. Their different evolutions of zeolite framework, acidity and Cu structure during the hydrothermal aging were probed by XRD, DRIFTS and NH3-TPD. The results suggest that Cu-SAPO-34 is more resistant to hydrothermal aging in comparison to Cu-SSZ-13. Last, the SO2 poisoning effect over Cu-SAPO-34 catalyst was investigated by using in-situ DRIFTS combined with temperature programmed desorption (TPD) experiments. It was found that the low temperature deactivation mechanism involved the formation of ammonium sulfate species as well as the competitive adsorption SO2 with NOx.

Zeolite scientists, whether they are working in synthesis, catalysis, characterization or application development, use the Atlas of Zeolite Framework Types as a reference. It describes the main features of all of the confirmed zeolite framework structures, and gives references to the relevant primary structural literature. Since the last edition 34 more framwork types have been approved and are described in this new edition. A further new feature will be that characteristic building units will be listed for each of the framework types.Zeolites and their analogs are used as desiccants, as water softeners, as shape-selective acid catalysts, as molecular sieves, as concentrators of radioactive isotopes, as blood clotting agents, and even as additives to animal feeds. Recently, their suitability as hosts for nanometer spacing of atomic clusters has also been demonstrated. These diverse applications are a reflection of the fascinating structures of these microporous materials. Each time a new zeolite framework structure is reported, it is examined by the Structure Commission of the International Zeolite Association (IZA-SC), and if it is found to be unique and to conform to the IZA-SC's definition of a zeolite, it is assigned a 3-letter framework type code. This code is part of the official IUPAC nomenclature for microporous materials. The Atlas of Zeolite Framework Types is essentially a compilation of data for each of these confirmed framework types. These data include a stereo drawing showing the framework connectivity, features that characterize the idealized framework structure, a list of materials with this framework type, information on the type material that was used to establish the framework type, and stereo drawings of the pore openings of the type material. - Clear stereo drawings of each of the framework types - Description of the features of the framework type, allowing readers to quickly see if the framework type is suitable to their needs - References to isotypic materials, readers can quickly identify related materials and consult the appropriate reference

Urea-SCR Technology for deNOx After Treatment of Diesel Exhausts presents a complete overview of the selective catalytic reduction of NOx by ammonia/urea. The book starts with an illustration of the technology in the framework of the current context (legislation, market, system configurations), covers the fundamental aspects of the SCR process (catalysts, chemistry, mechanism, kinetics) and analyzes its application to useful topics such as modeling of full scale monolith catalysts, control aspects, ammonia injections systems and integration with other devices for combined removal of pollutants.