Air Pollutants

CO is a colorless, odorless gas composed of one carbon atom bonded to one oxygen atom. It is emitted into the atmosphere as a result of incomplete combustion of fuels by power generating sources such as gas turbines, stationary diesel engines and stationary gas engines. CO can also be a byproduct of chemical manufacturing, food processing and many other applications. Once in the atmosphere, CO can cause harmful health effects to humans by reducing oxygen delivery to the body’s organs and tissues, and can even cause death at high levels. As a result, many countries and local governments have implemented strict emissions standards that regulate CO, such as the EPA’s National Ambient Air Quality Standards for CO.

To enable our customers to meet these CO emissions standards, Johnson Matthey has developed several advanced catalyst technologies, such as our Oxidation Catalysts (2-way) and our Three-way Catalysts, which convert CO to inert carbon dioxide. These catalyst technologies can also be coupled with system solutions such as our Modulex™ and DualOx™ catalytic converters.

NOx is actually composed of two oxides of nitrogen: nitric oxide (NO) and nitrogen dioxide (NO2). Nitric oxide consists of one nitrogen atom bonded to an oxygen atom, while nitrogen dioxide has one nitrogen atom bonded to two oxygen atoms. NOx is formed from the nitrogen in air during high-temperature combustion in excess oxygen. The two species exist in equilibrium. The formation of NO is favored at high temperature and NO2 is favored at low temperature. Sources of NOx include stationary diesel engines and stationary gas engines for power generation, coal and gas turbines for electric utilities, and other industrial, commercial, and residential sources that burn fuels.

Nitrogen oxides have several adverse effects on the human body such as inflammation of the respiratory system. Additionally, they help contribute to the formation of ground level ozone, which also causes health issues.  For this reason, NOx emissions from combustion sources are regulated by several local and national governments around the world. One of the most effective technologies for reducing NOx emissions is the Selective Catalytic Reduction (SCR) of NOx with ammonia. Johnson Matthey supplies SCR systems as well as SINOx® honeycomb SCR catalysts and plate SCR catalysts that nearly eliminate NOx emissions from industrial and power generating sources.

Nitrous oxide, or laughing gas as it is commonly called, consists of two nitrogen atoms bonded to an oxygen atom in a linear configuration. At room temperature it is a colorless, odorless gas that is a strong oxidizer. It is emitted into the atmosphere through industrial, power generating and agricultural processes. Common sources of N₂O include nitric acid manufacturing, the combustion of fuels in stationary diesel engines and stationary gas engines, and the application of fertilizers.

Although nitrous oxide is considered non-toxic, it is a very powerful greenhouse gas (GHG) with a Global Warming Potential (GWP) of 298 (100 years) compared to a GWP value of 1 for Carbon Dioxide [1]. Thus, in order to slow the effects of global warming, N₂O emissions must be limited. Some regulations are already in place to accomplish this such as the EPA’s Regulations for Greenhouse Gas Emissions from Passenger Cars and Trucks [2]. More regulations that will affect both mobile and stationary sources of emissions are expected to follow in the coming years.

Although N₂O can be created by emission control catalysts operating under specific conditions, Johnson Matthey has spent years developing advanced emission control catalyst formulations that minimize the amount of N₂O produced.  For example, our advanced Ammonia Slip Catalysts (ASC) operating over a wide temperature range exhibit very little N₂O formation. The ASC technology has been incorporated in many of our advanced SCR system designs for applications such as Stationary Diesel Engines and Stationary Gas Engines. 

[1] EPA Website - https://www.epa.gov/ghgemissions/overview-greenhouse-gases
[2] EPA Website - https://www.epa.gov/regulations-emissions-vehicles-and-engines/regulations-greenhouse-gas-emissions-passenger-cars-and

Dioxin is actually a general term used to describe a large group of aromatic (ring-containing) hydrocarbon compounds known to be environmental pollutants. Dioxins are persistent organic pollutants because they take a long time to break down in the environment and therefore accumulate in the food chain. Dioxins are formed as by-products in industrial processes which incorporate chlorine, such as the manufacture of chemical, pesticides, PVC plastics and paper products.  Another very common source of dioxins is the burning of municipal waste at waste incineration facilities. Dioxins are highly toxic and carcinogenic, affecting many parts of the human body, including the reproductive and immune systems.

Many local and national governments already have regulations in place to limit the emissions of dioxins from facilities such as waste incinerators. Johnson Matthey honeycomb SCR catalyst and plate SCR catalyst that is installed at waste incinerating facilities to reduce NOx, also significantly reduce dioxins. Johnson Matthey also supplies mixed oxide pellet catalyst that are specially formulated to reduce dioxins and other chlorinated hydrocarbons from industrial exhaust streams.

Formaldehyde is a colorless, water-soluble gas that consists of one carbon atom bonded to two hydrogen atoms and one oxygen atom.  Because it is one of the most widely used commercial chemicals, CH₂O is often considered separately from other Volatile Organic Compounds (VOCs). CH₂O is used in the manufacture of resins and a wide variety of chemicals, as a binder for building materials and as a preservative. The majority of CH₂O emissions are from the production of CH₂O itself and from the chemical manufacturing processes for which CH₂O is a feedstock. CH₂O is also emitted as a byproduct from refineries and combustion processes. It is a known carcinogen that causes irritation of the skin, eyes, nose, and throat.

One way to eliminate CH₂O is to oxidize it to carbon dioxide and water over an oxidation catalyst. Johnson Matthey has several advanced oxidation catalyst products such as our mixed oxide catalysts, available as pellets or honeycombs, and our precious metal-based Oxidation Catalysts which are used to treat CH₂O emissions from stationary gas engines.

Mercury is a naturally occurring element found in air, water, and soil. It is one of only two metals that are liquid at room temperature.  Mercury is also one of the most volatile of all the heavy elements, which means Mercury can easily vaporize and be emitted into the atmosphere.  There are several human sources of mercury emissions such as small scale industrial gold mining, cement manufacturing, and coal-fired power generation plants.

Since Hg is so volatile, it eventually settles into water or onto land where microorganisms can change it into methyl mercury, a highly toxic form that bio accumulates in animals, particularly fish.  These animals are then eaten by humans exposing them to the effects of methyl mercury, which harms the brain, kidneys, lungs and immune system. Regulators have started to limit the amount of mercury emitted into the air from these sources. Legislation such as the Mercury Air Toxicity Standards (MATS) in the USA and the Large Combustion Plants Best Available Techniques Reference Document (BREF) in Europe have set limits on the Hg emissions from coal fired power plants.

Johnson Matthey has several solutions for helping utilities lower they Hg emissions, such as our SCR catalyst for Hg oxidation. Additionally, Johnson Matthey offers a full assessment of the catalyst’s Hg oxidation performance as part of our standard Catalyst Evaluation and Sampling Services.

Methane, a colorless and odorless gas, is the lightest and most stable hydrocarbon. It is composed of one carbon atom bonded to four oxygen atoms and is the main component of natural gas. Methane emissions result from many human activities such as agricultural and industrial processes.  These industrial processes include steam methane reforming, coal mining, oil and gas exploration and the incomplete combustion of fuels that power gas turbines and stationary gas engines.

Although methane is nontoxic, it is very flammable and can cause explosions when mixed with air. It is also an asphyxiant gas which displaces air in confined spaces. However, the biggest concern is methane’s potential to increase global warming because methane has a Global Warming Potential of 25 times that of Carbon Dioxide over a 100-year period.

Methane can be catalytically oxidized to carbon dioxide and water.  Johnson Matthey has several technologies to reduce methane emissions, such as our Ventilation Air Methane (VAM) catalyst system for active and abandoned coal mines. Other JM technologies for methane reduction include oxidation catalysts (2-way) for gas turbines and lean-burn stationary gas engines and three-way catalysts (TWCs) for rich-burn stationary engines.

Ammonia is a colorless gas and has a pungent smell.  It consists of one nitrogen atom bonded to three hydrogen atoms.  It occurs in nature from decaying organic matter and from smaller, man-made sources such as fertilizers, waste disposal, and industrial processes.  Ammonia is highly toxic. It is irritating to the eyes, nose, throat, and respiratory tract and if inhaled at high concentrations, can cause death.

Ammonia emissions are regulated for nearly every application and are limited from all emissions control technologies. Ammonia is used as the reductant in the Selective Catalytic Reduction (SCR) of NOx. Johnson Matthey SCR systems utilize dosing control strategies to ensure the precise amount of ammonia (or urea, which decomposes to ammonia) is delivered to the honeycomb SCR catalyst or plate SCR catalyst minimizing ammonia emissions to the atmosphere. Ammonia Slip Catalysts (ASCs) are often coupled with SCR catalyst when both NOx conversion requirements and limits on ammonia emissions are exceptionally stringent.