The increasing price of liquid fuels and an increased focus on fuel efficiency has driven vehicle engine manufacturers toward diesel and other lean burn engines at the cost of increased emissions of nitrogen oxides (NOX), which contribute to pollution such as smog, ground level ozone, and acid deposition. Within the past thirty years, increasingly stringent NOX emission standards have forced engine manufacturers to develop novel ways to reduce these emissions. With the implementation of the latest American and European NOX emission standards, Selective Catalytic Reduction (SCR) has become the most prominent NOX reduction method in lean-burn engines.In the present work, a method is developed to test the performance of commercial SCR catalyst coated monoliths and probe the deactivation mechanisms. A monolith testing apparatus is constructed for these purposes. Necessary design features included a programmable gas mixing system, a steam generator, a temperature control system, and an analysis system based upon Fourier-transformed infrared spectroscopy. It is found that a high flow rate of carrier gas as well as a method to generate a water mist and prevent dripping is essential to ensure a stable supply of steam and repeatable results.Important SCR reactions, namely the standard, fast, and slow SCR reactions as well as NH3 adsorption and performance of a zeolite catalyst coated monolith were investigated at three temperatures -- 250 and 300 °C representing engine operation at normal operating conditions and 400 °C representing engine operation at high load. The amount of NH3 adsorbed decreased with temperature in line with previous studies while NOX reduction performance increased with higher temperatures at all inlet compositions tested. A transient drop in NO conversion performance was observed upon introduction of NH3 without the presence of NO2 consistent with previous studies suggesting an NH3 inhibition mechanism. When supplied with 1:1 and 1:3 ratios of NO:NO2 at 250 °C, the catalyst reduced more NOX than NH3 suggesting that part of the NOX reduction was proceeding through an ammonium nitrate intermediate and generating nitric acid. In addition, NH3 oxidation into N2O was prevalent at 300°C in an excess of NO2. The SCR reaction results indicate that both transient effects and side reactions play an important role in an NH3 SCR system, particularly one that is designed to operate under continuously changing conditions.Catalyst aging mechanisms were investigated by comparing catalytic performance, material structure, and surface composition of a new and a used zeolite catalyst monolith for the fast SCR reaction. Physical analysis of the catalyst monoliths through X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS) indicated four aging mechanisms. Both the new and used catalyst monoliths performed at least 95% NOX reduction in the fast reaction at all temperatures tested. Despite the similar NOX reduction performance, the used catalyst monolith exhibited lower NO oxidation performance, increased NH3 oxidation, and a lower quantity of adsorbed NH3 compared to the new catalyst monolith. Dealumination is likely the primary cause of the used catalyst monolith's lower NOX reduction performance with promoter metal deactivation, poisoning by sulfur and phosphorous, and mechanical failure of the catalyst coating on the monolith also contributing to the decreased performance. The results do not find evidence of carbon coking. This investigation into catalyst aging mechanisms confirms the efficacy of the commercial SCR catalyst monolith over long time periods.

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.

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.

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

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

Pincer complexes are formed by the binding of a chemical structure to a metal atom with at least one carbon-metal bond. Usually the metal atom has three bonds to a chemical backbone, enclosing the atom like a pincer. The resulting structure protects the metal atom and gives it unique properties.The last decade has witnessed the continuous growth in the development of pincer complexes. These species have passed from being curiosity compounds to chemical chameleons able to perform a wide variety of applications. Their unique metal bound structures provide some of the most active catalysts yet known for organic transformations involving the activation of bonds. The Chemistry of Pincer Compounds details use of pincer compounds including homogeneous catalysis, enantioselective organic transformations, the activation of strong bonds, the biological importance of pincer compounds as potential therapeutic or pharmaceutical agents, dendrimeric and supported materials.* Describes the chemistry and applications of this important class of organometallic and coordination compounds* Covers the areas in which pincer complexes have had an impact* Includes information on more recent and interesting pincer compounds not just those that are well-known