• 1.What are the parameters determining Emissions from Vehicles?
  • 2.How do we meet the objective of reducing vehicular emissions in India?
  • 3.How are emissions from motor vehicles controlled?
  • 4.What is a catalyst and how does it perform in a Vehicle?
  • 5.Do catalytic converters reduce the drivability and performance of the vehicle and intern increase fuel consumption?
  • 6.Do modern catalytic converters perform on short journeys?
  • 7.In a modern catalyst–equipped vehicle can we use lead replacement additives or new lead replacement petrol (LRP)?
  • 8. Are catalytic converters fragile? Do they need frequent replacement?
  • 9. In case of an accident, if the catalytic converter is damaged would the replacement catalyst used on the vehicle function as effectively as the original converter?
  • 10. How can you avoid the catalytic converter getting damaged by dangerous particles emitted from the engine?
  • 11. What is the time span for a Diesel Particulate Filter to get plugged?
  • 12. Is the catalytic converter helpful to health and the environment?
  • 13.During mining and refining of precious metals, which form a part of the catalytic converter, is higher pollution emitted than what they help in removing from the engine exhaust?
  • 14.What is the effect of sulfur-free fuel on exhaust emissions?
  • 15. What are the differences in toxic emissions from diesel and petrol engines?
  • 16.How can toxic particles from engines be avoided?
  • 17.Do all filters have the same efficiency?
  • 18. Doesn't the DPF become plugged with particulate material after a while?
  • 19.Catalytic converters produce CO2. Is this adding to the greenhouse effect?
  • 20.Are there enough precious metals for catalytic converters?
  • 21.How are used catalytic converters recycled?
  • 22.How are pollutants regulated worldwide?

Vehicular Technology, Fuel Quality, Inspection & Maintenance of In-Use Vehicles and Road and Traffic Management are the major parameters, which determine emissions from Vehicles. While each one of the four factors have direct environmental implications, the vehicle and fuel systems have to be addressed as a whole and jointly optimized in order to achieve significant reduction in emissions.

Introducing vehicles designed to meet stricter emission standards, introducing retrofitting of motor vehicles to use other kinds of fuel modifications or fuels such as compressed natural gas (CNG) and propane. Enforcing higher maintenance standards on existing vehicles, in order to keep emissions closer to the design standards of the vehicles.

A wide range of measures are being under taken to control air pollution from motor vehicles. Major measures are as under:

  • Fitting of Catalytic Converter.
  • Improving combustion process and Fuel management.
  • Adding Air injection or exhaust gas recycling.
  • Changing composition of the fuel i.e. lead free.
  • Reducing the time required for the catalytic converter to reach its full efficiency.
  • Using catalysts and absorbers to destroy Nitrogen Oxides under lean operation.
  • Using particulate filters with efficient regeneration technologies.
  • Periodic mandatory inspection of vehicle emissions at Pollution Under Control (PUC) centers.
  • Enforcement against smoky vehicles by Pollution Control Department
  • Good quality of road surface will lead to not only reduced vehicle operation cost but also decreased pollution.

A catalyst helps substances react together while itself remaining unchanged in the process. In an automobile catalytic converter, the catalyst helps the pollutants i.e. unburned Hydrocarbons, Carbon Monoxide and Nitrogen Oxides react with each other and with Oxygen from the atmosphere to form less harmful compounds like Water, Carbon Dioxide and Nitrogen.

With modern technology, the catalytic converters are designed as an integral part of the exhaust system as such they do not “sap power”. In case fuel economy which is very vital in today’s stage and lower exhaust emissions were not very important to preserve our environment then the modern high speed engines could generate more power. However, with today’s fuel management and advanced electronics being applied the modern engine technology shows that the engine performs better both in fuel economy as well as power mode than its predecessors wherein catalytic converters were not being used.

Yes. Although modern catalytic converters need a moderately hot exhaust to start working with the available technology this happens within a short span of 30 seconds of the start of the engine. Thus it is a myth that catalytic converters do not work on short journeys.

The lead replacement additives as well as petrol have totally different chemistries, which would react negatively with the catalyst-equipped vehicle. As such this should be totally avoided, as it would damage the catalytic converter. These additives were particularly designed for vehicles that were not equipped with the modern catalytic converters.

The modern catalytic converter is one of the most reliable elements in the engine management system. It is very robust since it is normally placed in a metal housing and has a lifespan of over 100,000 Kms.

Catalytic converters obtained thru authorized vehicle dealers are the most authentic way to ensure that the replaced converter is functioning as effectively as the original. It is not recommended to use second-hand converters, even if dimensionally there is no difference as each converter is developed and designed keeping the engines power and exhaust gases in mind.

The use of a particulate filter is the best way to avoid damage to the catalytic system. This consist of positioning a filter in the exhaust line which is designed to collect both solid and liquid particulate matter (PM) emissions but allowing the exhaust gases to go through. A large number of Diesel vehicles are now being fitted with such Diesel Particulate Filters (DPF).

These filters primarily retain minute particles of soot, lube-oil ashes, engine wear products as well as fuel borne catalyst ashes. Further catalytic soot burning allows regeneration of its efficiency. Normally maintenance should be done every 100,000 Kms.

Yes, otherwise harmful polluting gases like Carbon Monoxide, Hydrocarbons and Nitrogen Oxides would get emitted into the atmosphere if the modern vehicles were not fitted with Catalytic Converters. In fact it has become mandatory to fit catalytic converters in order to remove such polluting gases.

Research has shown that after initial bedding in (approx. 5000 Kms.) catalytic converters certainly contribute to improve the environment. This is due to the acidification potential of Nitrogen Oxides (NOx) emissions removed from the exhausts by use of auto catalysts and the sulphur oxides (SOx) emitted during the refining of these precious metals.

Exhaust emissions will be lower - particularly from catalyst-equipped cars. Sulfur in petrol and diesel fuel has a major negative impact on catalyst performance, especially for NOx catalysts and adsorbers. The effect of sulfur on catalyst performance becomes more critical as lower tailpipe emissions are targeted for the very low emission levels now required. Sulfur strongly competes against pollutants for "space" on the catalyst surface limiting the efficiency of catalyst systems to convert pollutants at any sulfur concentration - so the lower the sulfur levels in fuels the better the catalyst performance that can be obtained. The conversion of sulfur to a sulphate aerosol can cause net increases in diesel particulate emission.

Because maximum power production from diesel engines is fuel and not air limited it is still the only engine that is "lean burn" across the full power/speed range. This brings real fuel and carbon dioxide emission savings - good for the global environment. But it challenges the catalyst chemist to control nitrogen oxide and particulate emissions at low exhaust temperatures with excess oxygen. In parallel to low sulfur diesel fuel introduction, Diesel Particulate Filters (DPF) are now fitted on passenger cars and Selective Catalytic Reduction (SCR) catalysts and NOx traps are being progressively introduced. This will help the diesel engine to reach the exhaust emission levels of the petrol engine.

The best way is to use a particulate filter. These systems consist of a filter positioned in the exhaust line and designed to collect solid and liquid particulate matter (PM) emissions while allowing the exhaust gases to pass through the system. Increasing numbers of diesel cars, trucks and buses are now being fitted with Diesel Particulate Filters (DPF).

No, based on engine technology and engine management, different filter technologies may be used to meet the prescribed emission standards. It is possible with advanced filter technology (wall-flow filters) to almost completely eliminate the carbon particulates, including fine particulates of less than 100 nanometres (nm) diameter with an efficiency of >95% in mass and >99% in number. The removal of ultra-fine particles is very important since health experts believe that they are carried deep into the lungs and are thought to be the most dangerous size of PM. Partial-flow filters operate with the bypass flow principle. The overall filtration efficiency of these partial-flow filters is 30-60% in mass depending on application and operating conditions.

Particulate filters retain all particles: soot, lube-oil ashes, engine wear products and, when applicable, Fuel Borne Catalyst (FBC) ashes. On-board catalytic soot burning allows automatic regeneration of the DPF's efficiency. Depending on the application, this can be done through passive regeneration (continuous oxidation of particulates by NO2), the use of a FBC which lowers the soot burning temperature, or, active engine control strategies periodically increasing the exhaust temperature. Any residual ash can be cleaned during maintenance if requested by the car manufacturer but most passenger car systems are now designed to last for the lifetime of the vehicle without maintenance.

All the carbon contained in fossil fuels is ultimately converted to CO2 in the atmosphere. By accelerating that conversion, and removing other dangerous pollutants in the process, catalytic converters do not increase overall CO2 levels. The only way to reduce CO2 emissions is to burn less fossil fuel.

The precious metals, including platinum (Pt), have been recycled since long before this became a necessity to conserve our resources. From the onset of their use in cars, catalytic converters have been removed from end-of-life (EOL) vehicles and the platinum, palladium (Pd) and rhodium (Rh) recovered. In Europe, autocatalysts platinum recycled share increased from 5 to 10% between 1997 and 2007 whilst that for palladium went from essentially zero to 33% over the same period. On a worldwide basis, 21% of Pt, Pd and Rh demand for automotive catalyst was met by recovered precious metals in 2007(2). The share of recycled precious metals continues to grow as the first generation of cars equipped with catalysts is reaching the end of their useful lives. Although highly efficient refining processes are available and used to recover PGMs from autocatalysts with more than 95% yield, significant inefficiencies still exist in the end-of-life phase of cars. Especially old European cars are increasingly exported to developing countries where for various reasons no proper recycling takes place at the final end-of-life. In total this leads to considerable losses from the autocatalyst lifecycle, thus a more sound management of EOL-cars as well as to create a global recycling infrastructure is needed. The current leakages in the autocatalyst lifecycle are not a real threat from the reserve base, but better recycling rates would mitigate price volatility and environmental impact of the PGM supply.

Modern car dismantlers scrap yards and workshops remove used catalytic converters from end-of-life vehicles according to the European End-of-Life Vehicle Directive which specifies minimum levels of recycling for scrapped vehicles. Specialist companies collect them and accumulate bigger lots at central warehouses. The converters are decanned; i.e. the ceramic or metallic catalyst is removed from the steel can by special cutting devices. The steel is sorted by quality and sold as secondary scrap to steel plants. The catalyst with the precious metals is delivered to precious metals refiners, specialized in the recovery of Platinum Group Metals (PGM) to generate high purity platinum, palladium and rhodium identical to newly extracted PGM from the mines.

European and American emission limits are used in other continents. For example, in India, passenger cars and commercial vehicles met Bharat stage I (equivalent to Euro 1) nation-wide in 2000 and Bharat stage II (equivalent to Euro 2) in 2005. In 11 Indian metropolitan areas, Bharat stage III (Euro 3) has to be met since 2005. This Bharat stage III is now planned nation-wide in 2010 except for 11 major cities where the tougher Bharat stage IV (Euro 4) limit will be required. For 2-3 wheelers, Bharat stage II norms are applicable from 2005 and Bharat stage III will come into force between 1st April 2008 and 1st April 2010.

In China, Euro 1-based legislation was introduced in 2000 (GB stage 1) followed by a Euro 2-type limits in 2003-2004 (GB stage 2), a Euro 3-type limits were introduced in 2007 (GB stage 3) and Euro 4 is planned for 2010 (GB stage 4). Specific emission limits are to be progressively introduced in big cities such as GB stage 4 in Beijing at the beginning of 2008.Fuel quality standards enhancement is now required to move to more stringent legislation on emissions.