Types of Catalytic Converters Used in Cooking Ovens and How They Differ

Catalytic converters are used in cooking ovens to reduce fumes and help keep the oven clean, but there are several different types, each with its own technology and benefits. The type of catalytic converter required depends on the oven design, operating temperature, fuel source, and the pollutants that need to be controlled. Understanding these differences makes it easier to choose the right technology for domestic or commercial cooking applications.

While some converters are intended to oxidise grease and food residues, others are designed to reduce harmful emissions such as carbon monoxide, hydrocarbons, or particulate matter. Understanding these differences helps explain why catalytic technology varies across domestic and commercial cooking appliances.

Catalytic Converters in Domestic Electric Ovens

Some domestic electric ovens are described as ‘catalytic self-cleaning ovens’. With this type of oven, the walls of the cooking chamber have a catalytic layer which helps to oxidise food spills and grease. This process occurs at temperatures above 200 oC and helps to keep the oven clean. Among the most commonly used catalytic converter materials is manganese dioxide which is deposited onto a material with a very high surface area, such as alumina or silica.

Another type of domestic electric oven is described as ‘pyrolytic self-cleaning’. These ovens have a special high temperature setting at around 500 oC, which is only used for burning off food spills and grease, using a process known as pyrolysis. Unfortunately, this process emits some unpleasant fumes, including carbon monoxide. Therefore, catalytic converters are normally installed to oxidise these fumes.

Unlike the catalytic self-cleaning oven, where catalytic material is coated directly onto the walls of the cooking chamber, a catalytic converter for a pyrolytic self-cleaning oven is based on a matrix which incorporates many small channels through which the fumes pass. The matrix, which may be made from ceramic, metal foil or wire, increases the surface area where gasses come into contact with catalytic converter materials.

Since domestic ovens are very price sensitive, the catalytic material is normally not precious metals because these are too expensive. Manganese dioxide, Hopcalite, ceria or Perovskites are suitable catalytic converter materials which will reduce fumes effectively at the high temperatures involved.

Catalytic Converters for Commercial Ovens

Commercial ovens have different requirements. Some are designed to operate in premises without traditional ventilation systems where there is a need to reduce both the smell of the cooking as well as the grease emissions. A particular type of oven known as ‘ventless’ is often used in food service outlets such as coffee shops and service stations, which, apart from not having traditional extraction systems, are also open-plan, meaning that, if there are any cooking fumes, the customers are exposed to them.

A catalytic converter is therefore installed in this type of oven to reduce cooking fumes. It must be able to operate at typical cooking temperatures and can handle a large throughput of fumes (since commercial ovens cook much faster than domestic ovens).

An important difference between commercial ovens and the domestic type is that commercial ovens are much more expensive, and therefore the cost of components can be more expensive too. Due to the need to operate effectively with high volumes of fumes at temperatures as low as 200 oC, most catalytic converters used in commercial ovens are based on precious metals. However, there are varying degrees of sophistication used in the coating process, and therefore some products can achieve the same results by using small amounts of precious metals more efficiently.

Catalytic Converters for Solid Fuel Ovens

Not all cooking ovens are powered by electricity however, and another popular option is to use solid fuel such as wood or charcoal. This changes the priority of the catalytic converter from dealing with the emissions from the food, to those from the fuel. Burning solid fuel releases toxic substances such as carbon monoxide, hydrocarbons and particulate matter which are problematic both in the confined space of a kitchen as well as detrimental to the air quality in the local area.

Burning charcoal is especially dangerous because this is usually done with a restricted air supply to prevent it burning too hot. As a result, it is quite common for charcoal ovens to emit flue gas containing up to 5% carbon monoxide whereas the safe limit is about 1000 times lower than this.

Converters for solid fuel ovens are always based on a matrix. The catalytic material for commercial solid fuel ovens, such as charcoal or pizza ovens, is usually precious metals. However, an interesting future development is to use catalytic technology to reduce emissions from domestic solid fuel ovens which are very common in low-income countries and contribute to many health problems. In this case it is very important to keep the price of the catalytic converter low, so using alternative catalytic converter materials to replace the expensive precious metals is essential.

Here is a useful summary of the different types: