Panasonic Corporation announced today it has succeeded in the development of a new catalyst using an alkali metal compound to decompose and purify particulate matter in diesel engine exhaust gas[1], and has begun shipping its samples this month. As diesel emission regulations have become increasingly stringent, particularly in Japan, the US, and Europe, there are high expectations for this new catalyst as it presents a low-cost and energy-saving solution for diesel-powered vehicles.

This new alkali metal-based catalyst developed by Panasonic Ecology Systems Co. Ltd., a subsidiary of Panasonic Corporation, accelerates the oxidation of particulate matter and directly decomposes them without using platinum. It provides the same level of combustion performance as a conventional platinum-based catalyst but at a lower temperature (approximately 20% lower, in-house experiment). This means less energy is required to maintain the optimum temperature for catalytic reactions, thereby reducing CO2 emissions and contributing to energy conservation. When used at the same temperature required for the conventional platinum-based catalyst, this new catalyst even increases the combustion speed.

In comparison, the current mainstream diesel exhaust treatment equipment uses platinum as the purification catalyst, making its costs more expensive and susceptible to price fluctuations. In addition, conventional equipment consumes fuel in order to maintain the temperature for catalytic reaction at an optimum level during particulate treatment, reducing the overall effect of the equipment.

Standard diesel exhaust gas treatment equipment consists of a diesel oxidation converter (DOC)[2], which removes hydrocarbons (HC) and carbon monoxide (CO), and a catalyst-coated diesel particulate filter (DPF)[3] , which removes particulate matter. With a conventional catalyst, the DOC itself also requires platinum to produce nitrogen dioxide (NO2), as the conventional catalyst cannot decompose particulate matter without the oxidation action of NO2. However, since the newly developed catalyst can directly decompose particulate matter without using NO2, the amount of platinum used in the DOC can also be significantly reduced, thereby reducing the total cost of the equipment.

In addition to using a new metal compound in the catalyst, Panasonic has devised a new catalyst coating technology to maximize the performance of the catalyst on a variety of DPF types (cordierite[4], SiC[5], metal, etc.). A new additive was also developed to solve the durability issue associated with a catalyst using alkali metal, making this new technology possible. Panasonic currently has 84 patents in Japan and 7 patents overseas, including pending applications.

[Fig. 1] Principle of particulate matter (PM) combustion by the catalyst-coated DPF

Details of the features

Combust particulate matter without using platinum

The new catalyst is based on an alkali metal compound which produces active species of alkali metal in the reaction temperature range. The active species accelerate oxidation of particulate matter [mainly made of carbon (C)] and decompose them into CO2 (Fig. 1). Unlike the conventional type of catalyst, the new catalyst does not use platinum.

[Fig. 2] Changes in the catalyst-coated DPF treatment speed with temperature

Combust particulate matter at a low temperature

The new catalyst based on the alkali metal compound provides the same level of combustion performance as a conventional platinum-based catalyst at a lower temperature (Fig. 2). Therefore, the temperature of diesel exhaust gas treatment equipment can be lowered, reducing the amount of fuel used for maintaining the temperature and enhancing the energy efficiency of the equipment.

[Fig. 3] Structure of diesel exhaust gas treatment equipment

Reducing costs of diesel exhaust gas treatment equipment

Diesel exhaust gas treatment equipment consists of a DOC[2], which removes hydrocarbons (HC) and carbon monoxide (CO), and a catalyst-coated DPF[3], which removes particulate matter. With a conventional catalyst, the DOC needs platinum to produce nitrogen dioxide (NO2). Since the new catalyst can directly decompose particulate matter without using NO2, the amount of platinum used in the DOC can be significantly reduced, thereby reducing the total cost of the equipment.

Glossary
[1] Particulate matter in diesel engine exhaust gas - Fine substances based on carbon (C) contained in the exhaust gas from diesel engines. They are a major component of the black exhaust gas produced by diesel engines and pollute the air. Therefore, removal of particulate matter is required by regulations.
[2] DOC (Diesel Oxidation Converter) - One of the components of diesel exhaust gas treatment equipment. Its function is to decompose the hydrocarbons (HC) and carbon monoxide (CO) contained in diesel engine exhaust gas. When used in combination with a conventional platinum-based catalyst-coated DPF, platinum needs to be added to the DOC to produce NO2.
[3] Catalyst-coated DPF (Diesel Particulate Filter) - One of the components of diesel exhaust gas treatment equipment. Its function is to remove the particulate matter contained in diesel engine exhaust gas. DPF is made by coating a base material with a catalyst.
[4] Cordierite - One type of ceramic material used in catalyst to process engine exhaust gas. Its relative density is light and it excels in heat capacity.
[5] SiC - One type of ceramic material used in catalyst to process engine exhaust gas. It excels in heat resistance.