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Introduction The topical conference series Catalysis and Automotive Pollution Control, generally known by the acronym ‘CAPoC’, has taken place periodically at the Université Libre de Bruxelles, Belgium, since the first one in 1986. The late Professor Alfred (Freddy) Frennet was central in establishing these conferences and for many years he was their guiding force. The first four...
Recent concerns over the health effects of particulate emissions from vehicles have focused on diesel engines. While European legislation to limit their emissions is now in place it is expected that future legislation will be more demanding. Using a platinum catalyst it has been possible to demonstrate in various trials the practical application of a novel system for the removal of both the soot and hydrocarbon components from diesel powered vehicle exhaust. The background to the development of this successful technology is described here.
The development of gasoline direct injection (GDI) engines has provided a strong alternative to port fuel injection engines as they offer increased power output and better fuel economy and carbon dioxide emissions. However, particulate matter (PM) emission reduction from GDI still remains a challenge that needs to be addressed in order to fulfil the increasingly stricter environmental...
Driven by concerns on deteriorating ambient air quality, measures are being taken across the world to adopt and enforce tighter vehicular emission regulations to minimise tailpipe unburned hydrocarbons, nitrogen oxides (NOx) and particulate matter (PM). In regions with advanced regulations, the focus is on limiting the pollutants under real-world or in-use driving conditions. Given the intensified effort to curb global warming and limit fossil fuel use in the transportation sector, several countries have adopted targets on tailpipe carbon dioxide emissions. This confluence of stringent regulations for both criteria pollutant and greenhouse gas (GHG) emissions is leading to a rapid adoption of advanced powertrains and aftertreatment technologies. This is a review of some of these recent advances pertinent to reducing vehicular emissions and developing improved aftertreatment solutions. The scope is limited to gasoline vehicles where the adoption of gasoline direct injection (GDI) and hybrid powertrain technologies is leading to significant shifts in the aftertreatment solutions. There is significant work being done to improve diesel aftertreatment systems especially in light of real-world driving emission (RDE) regulations. These are not covered here, rather the reader is referred to a previous article in this journal’s archive (1), and to a more recent review (2).
Increasingly demanding exhaust emissions regulations require that automotive three-way catalysts (TWC) must exhibit excellent catalytic activity and durability. Thus, developing TWC based on an accurate understanding of deactivation mechanisms is critical. This work briefly reviews thermally induced deactivation mechanisms, which are the major contributor to deactivation, and provides an overview of the common strategies for improving durability and preventing deactivation. It highlights the interaction of metals with supports and the diffusion inhibition of atoms and crystallites in both washcoats and metal nanoparticles and concludes with some recommendations for future research directions towards ever more challenging catalyst manufacture to meet increasing durability requirements both now and in the future.
The pollution problem known as acid rain has focused attention on the need to control all major sources of contributing emissions. The use of platinum metal catalysts to control automobile exhaust gases is now well developed but in fact over half the man-made nitrogen oxides exhausted into the atmosphere are emitted from sources other than vehicles, and include power station boilers, industrial boilers and stationary internal combustion engines. Several methods may be used to prevent these emissions, and platinum catalysts, either alone or in combination with one or more of the base metal catalysts currently used, appear to have considerable potential for this application.
One of the more evocative cases of disruptive innovation is how steam powered vessels displaced sailing ships in the 19th century. Independent of wind and currents, shipping entered a new age. Faster shipping enabled more efficient trading and easier international travel. It fuelled economic growth and wealth creation. This transition was not rapid, taking half a century to evolve, a period in which hybrid vessels, those using sails and steam generated power were a common sight. The age of steam brought a period of change which affected many aspects of shipping, not only its appearance and practices but also its environmental impact. It facilitated further disruption and the emergence of what has become the industry standard for a ‘prime mover’: the diesel engine. Achieving the decarbonisation of the shipping fleet as soon as possible this century will be one of the most significant disruptions the shipping sector has had to manage. Meaningful change by 2050 requires strategic development and decisive action today, made all the more complicated by the immediate demands that the sector manages both the current and longer term impact that the COVID-19 pandemic will have on the shipping industry. This paper looks briefly at the transition from wind power to carbon based fuel power to gain insight into how the shipping sector manages disruptive change. It also reviews some technology options the shipping sector could adopt to reduce its environmental impact to meet a timetable of international requirements on ship emissions limits. The paper will focus on how the engine room might evolve with changes in: (i) energy conversion, how power is generated on board, i.e. the engine; and (ii) energy storage, i.e. choice of fuel.
The annual SAE Congress is the vehicle industry's largest conference and covers all aspects of automotive engineering. The 2012 congress took place in Detroit, USA, from 24th–26th April 2012. There were upwards of a dozen sessions focused on vehicle emissions technology, with most of these on diesel emissions. More than 70 papers were presented on this topic. In addition, there were two...
The control of oxides of nitrogen (NOx) emissions to meet more stringent motor vehicle emission legislation has been enabled by the development of various exhaust gas aftertreatment technologies, notably those that employ platinum group metals (pgms). Technology Developments For gasoline engines the most common aftertreatment for the control of NOx, as well as the other major regulated...
Gasoline particulate filters (GPFs) are being developed to enable compliance with future particulate number (PN) limits for passenger cars equipped with gasoline direct injection (GDI) engines. A PN emissions limit of 6 × 1011 km–1 over the New European Drive Cycle (NEDC) will apply for new GDI vehicles from September 2017. (A three year derogation allowing a higher PN limit of 6 × 1012...
Many industrial processes produce hydrocarbon vapours which, if released to the atmosphere, contribute to the general pollution of the environment. The discharge of such vapours is now, not unnaturally, being subject to legislative control in many places as the extent of the damage resulting from such pollution is more fully realised. Platinum catalyst control systems are being increasingly employed to prevent air pollution as the cost benefits of employing such systems, are becoming more generally known. This paper describes the system one enterprising organisation has successfully employed to comply with the strict pollution control regulations in Los Angeles, a region where topography and climatic conditions result in particularly difficult pollution problems, while at the same time making substantial savings in fuel.
On-road tailpipe volatile organic compounds (VOCs) were sampled from light-duty diesel trucks (LDDTs) compliant with Euro III to V, and a total of 102 VOC species were quantified. The composition characteristics and carbon number distributions were investigated, and the contribution of individual VOC to ozone formation potentials (OFPs) was weighted. Results showed that alkanes were the major VOC species, accounting for approximately 65.5%. VOC emissions decreased significantly as the standards became stricter, especially for alkanes and aromatics; and the VOC emissions on highway were much lower than those on urban roads. Carbon number distribution of VOCs was mainly concentrated in C3–C4 and C10–C12. Aromatics were the major contributors to ozone formation, taking up 49.3–57.6% of the total OFPs, and naphthalene, 1-butene, dodecane, 1,2,3-trimethylbenzene and 2-propenal were the top five species. The information provided insight into the tailpipe VOC emission characteristics and may help decision makers drafting related emission policies.
A catalyst support is often used to disperse a catalyst material to enhance the contact area for reaction. In catalytic converters, a coating called the catalyst layer contains both the catalyst support and catalytically active material. Given the role of the catalyst layer in catalytic converters, its mechanical strength is of great importance as it determines the service life of catalytic converters. This review paper therefore summarises a number of methods which are currently used in the literature to measure the strength of a catalyst layer. It was identified that the methods applied at present could be divided into two groups. All methods regardless of the group have been successfully used to investigate the effect of a range of formulation and process parameters on the strength of a catalyst layer. In terms of measurement principles, Group 1 methods measure the strength based on mass loss after the layer sample is subjected to a destructive environment of choice. Group 2 methods tend to give more direct measurements on the strength of bonding between particles in a catalyst layer. Therefore, strength data generated by Group 2 methods are more reproducible between different researchers as the results are less dependent on the testing environment. However, methods in both groups still suffer from the fact that they are not designed to separately measure the cohesive and the adhesive strength of a catalyst layer. Two new methods have been recently proposed to solve this problem; with these methods, the cohesive and adhesive strength of a catalyst layer can be measured separately.
The price differential between platinum and palladium has driven the industry to adopt emissions control catalyst formulations for gasoline engines that contain higher levels of Pd than Pt, and in most cases no Pt. In addition fluctuations in the price of rhodium have led to thrifting of this metal. This study compares the performance of ten different catalyst compositions with varying ratios of Pt, Pd and Rh for a Euro 5 vehicle and under bench test conditions. The results show that a system with low Rh loading can readily be improved by increasing the Rh loading and there is a relatively large effect of doing this by a small amount. Increasing the Pd or Pt loading also improves emissions performance but by a significantly smaller amount than the effect of changing the Rh loading. Conversely it may be possible to decrease the Pt or Pd loading with only a small effect on emissions. Furthermore it was found that Pd outperforms Pt under most conditions, although not significantly. The difference appears greater under more stressful conditions such as high-speed driving or wide perturbation amplitude.
Natural gas is of increasing interest as an alternative fuel for vehicles and stationary engines that traditionally use gasoline and diesel fuels. Drivers for the adoption of natural gas include high abundance, lower price and reduced greenhouse gas emissions compared to other fossil fuels. Biogas is an option which could reduce such emissions further. The regulations which cap emissions from these engines currently include Euro VI and the US Environmental Protection Agency (EPA) greenhouse gas legislation. The regulated emissions limits for methane, nitrogen oxides (NOx) and particulate matter (PM) for both stoichiometric and lean burn compressed natural gas engines can be met by the application of either palladium-rhodium three-way catalyst (TWC) or platinum-palladium oxidation catalyst respectively. The drivers, policy and growth of this Pd based catalyst technology and its remaining challenges to be overcome in terms of cost and catalyst deactivation due to sulfur, water and thermal ageing are described in this short review.
China has continuously upgraded the emission standards for non-road diesel mobile machinery since they were first issued in 2007. This paper reviews the Chinese non-road diesel mobile machinery emission standards, analyses the change in the environmental situation and management policy and puts forward some principles and suggestions for developing emission standards for non-road mobile machinery in the future. It will have a positive effect on improving the theory and methods for developing mobile source emission standards, as well as boosting the level of environmental management and emission control in China.
The design of catalyst products to reduce harmful emissions is currently an intensive process of expert-driven discovery, taking several years to develop a product. Machine learning can accelerate this timescale, leveraging historic experimental data from related products to guide which new formulations and experiments will enable a project to most directly reach its targets. We used machine learning to accurately model 16 key performance targets for catalyst products, enabling detailed understanding of the factors governing catalyst performance and realistic suggestions of future experiments to rapidly develop more effective products. The proposed formulations are currently undergoing experimental validation.
Innovative Emissions Measurement and Perspective on Future Tailpipe Regulation[67, (2), 130 ]
The Euro 7 exhaust emissions regulation will be important both from the perspective of how it further improves air quality, but also of certain greenhouse gas emissions and the economics of the internal combustion engine. This paper sets out the ongoing importance of ozone to urban air quality, and how tailpipe volatile organic compound (VOC) emissions contribute to that as well as having direct human health effects through inhalation. The paper then sets out a novel method for the measurement of speciated VOCs and nitrous oxide (N2O) at the tailpipe in real-world conditions, and presents initial results across a range of modern light-duty vehicles. Based on the results, it may be the case that VOCs should be a higher priority for future regulation than N2O, although more research is required to achieve a consensus on typical real-world N2O emissions.
Advanced Catalytic Technologies for Compressed Natural Gas–Gasoline Fuelled Engines[67, (2), 171 ]
The main challenges of compressed natural gas (CNG) engine fuelling in terms of methane abatement in the aftertreatment system are addressed in this study using differently loaded platinum group metal (pgm) catalysts. A dual-fuel injection strategy of methane-gasoline was implemented where methane gas was port-injected into the intake in stoichiometric conditions at levels corresponding to 20% and 40% energy density replacement of gasoline fuel. High, medium and low loaded palladium-rhodium catalysts were used and compared to study the effect of pgm loading on the catalyst light-off activity for methane. Results indicate that increasing the palladium loading led to significantly earlier light-off temperatures achieved at relatively lower temperatures of 340°C, 350°C and 395°C respectively. However, the benefit diminishes above palladium loading >142.5 g ft–3. The study has also demonstrated that ammonia is formed over the CNG catalyst due to steam-reforming reactions from the increased levels of methane in the exhaust with dual-fuelling. Hence aftertreatment technologies such as selective catalytic reduction (SCR) should be adopted to remove them. This further highlights the need to regulate the harmful ammonia emissions from future passenger cars fuelled with CNG. In addition, the benefits of the dual-fuel system in terms of lower engine output carbon dioxide, non-methane hydrocarbon (NMHC) and particulate matter (PM) emissions compared to the gasoline direct injection (GDI) mode alone are presented.