Next-Generation Catalytic Converter for Diesel Engines Reduces Toxic Emissions by up to 70 Percent

1 December 1997

           Pass Car System Under Development by Siemens Automotive
           Could be Benchmark in Diesel Exhaust-Gas After-Treatment

    AUBURN HILLS, Mich., Dec. 1 -- Siemens Automotive is
developing an advanced catalytic-converter module for passenger car diesel
engines that reduces nitrogen oxide (NOx) and hydrocarbon (HC) emissions up to
70 percent.
    Known as SINOx, the system uses electronics, sensors and injection
technology along with a reducing agent to trigger a chemical reaction that
converts NOx and HC into non-toxic levels of nitrogen and water.
    "SINOx is currently the most effective exhaust-gas after-treatment system
for reducing NOx and HC emissions on diesel engines -- and we're adapting it
for diesel passenger car applications," said George Perry, president and CEO
of Siemens Automotive Corporation, and senior vice president and general
manager of the company's global Powertrain Division.
    Diesel engines are attractive to automakers due to their fuel efficiency
-- especially in Europe where the price of fuel is significantly higher than
in North America.
    In addition, "lean-burn" diesel engines -- powerplants that use less fuel
and more air in the combustion chamber -- are being considered around the
world for the next generation of fuel-efficient vehicles.
    However, NOx and HC emissions have remained the diesel engine's greatest
drawback, Perry said, and medium-term solutions to such challenges will only
be found in the use of exhaust-gas after-treatment systems.
    Urea -- sometimes called carbamide -- is an odorless, water-soluble,
nitrogenous compound.  It is often used as an environmentally friendly base
material in pharmacy and cosmetic products.
    When used as an emissions-reducing agent in diesel exhaust-gas management,
a quantity of urea equal to approximately 3 percent of the diesel fuel
consumed by the engine can result in significant emissions reductions in NOx
(up to 70 percent) and HC (between 50 and 70 percent).
    The SINOX system's electronic control system processes temperature and
emission level information fed from sensors, and then meters and injects
appropriate amounts of urea into the system.
    "The system uses a urea-water solution and injects it into the mixing
chamber," Perry explained.  "This results in a chemical reaction that releases
ammonia, which in turn converts NOx and HC into non-toxic quantities of
nitrogen and water."
    This process -- known as Selective Catalytic Reduction (SCR) -- is
currently the best available for reducing NOx in diesel exhaust emissions,
according to Perry.
    The system's converter module is a sheet-metal jacket housing a ceramic
block with a high-titanium and tungsten oxide content, which Perry says makes
chemically inert metals and coatings unnecessary.

SOURCE  Siemens Automotive Corporation