SCR catalytic converters

An SCR catalytic converter is one of the two main components in an SCR system.

A catalytic converter consists of a structure called a ‘substrate’ which looks a bit like a honeycomb, together with some chemicals which act as catalysts.

SCR systems may utilise catalytic converters for several different purposes, but the most important of these is to promote the reaction between oxides of nitrogen and ammonia. These are often referred to as ‘denox’ catalysts, and can reduce NOx by 95% or more.

There are three main types of catalytic material which are used in denox catalysts, and the advantages and disadvantages of these are summarised in this table:

Advantages Disadvantages
Vanadium pentoxide Resistant to poisoning by sulphur Toxicity
Iron-exchanged zeolite Good activity at high temperatures Sensitive to poisoning by sulphur
Copper-exchange zeolite Good activity at low temperatures Sensitive to poisoning by sulphur


There are also two main types of substrate, as follows:

Advantages Disadvantages
Ceramic Inherent porosity leads to a high surface area if coated carefully Only available in small sizes. Large engines require multiple substrates
Metallic Large round substrates are available Multiple stages required to obtain a good quality coating

There have been major changes in the field of SCR catalytic converters in recent years, both in terms of the coating technology and the supply chain, and Blackthorn has updated its product portfolio so that we can offer our customers class-leading products.

Blackthorn can recommend the most appropriate combination of substrate and catalytic material for a particular application, and also calculate the dimensions required to achieve the reduction in NOx which is stipulated.