Page "Catalytic converter" Paragraph 41

Regulations of fuel quality vary across jurisdictions.

In North America, Europe, Japan and Hong Kong, gasoline and diesel fuel are highly regulated, and compressed natural gas and LPG ( Autogas ) are being reviewed for regulation.

In most of Asia and Africa, the regulations are often lax: in some places sulfur content of the fuel can reach 20, 000 parts per million ( 2 %).

Any sulfur in the fuel can be oxidized to SO < sub > 2 </ sub > ( sulfur dioxide ) or even SO < sub > 3 </ sub > ( sulfur trioxide ) in the combustion chamber.

If sulfur passes over a catalyst, it may be further oxidized in the catalyst, i. e., SO < sub > 2 </ sub > may be further oxidized to SO < sub > 3 </ sub >.

Sulfur oxides are precursors to sulfuric acid, a major component of acid rain.

While it is possible to add substances such as vanadium to the catalyst washcoat to combat sulfur-oxide formation, such addition will reduce the effectiveness of the catalyst.

The most effective solution is to further refine fuel at the refinery to produce ultra-low sulfur diesel.

Regulations in Japan, Europe and North America tightly restrict the amount of sulfur permitted in motor fuels.

However, the expense of producing such clean fuel may make it impractical for use in developing countries.

As a result, cities in these countries with high levels of vehicular traffic suffer from acid rain, which damages stone and woodwork of buildings, poisons humans and other animals, and damages local ecosystems.