Advanced Temperature-Programmed Oxidation (TPO) of Coked Catalysts Using Integrated Methanation and FID Detection
Understanding Catalyst Coking
Heterogeneous catalysis plays a critical role across many industries, from energy production and chemical synthesis to petrochemicals, pharmaceuticals and consumer products. Manufacturers rely on solid and powdered catalysts to accelerate reactions and convert feedstocks, including hydrocarbons, into valuable products.
However, catalysts can lose activity over time. One of the most common causes is coking – the formation and accumulation of elemental carbon on the catalyst surface. As carbon builds up, it can cover active catalytic sites, restrict access to the catalyst surface and block pores within the catalyst structure. These deposits can reduce reaction rates, alter product selectivity and eventually lead to catalyst deactivation.
Understanding how and why coke forms therefore plays an important role in improving catalyst performance and extending catalyst lifetime.
Characterising Carbon Deposits
Researchers use a range of analytical techniques to investigate carbon deposits on catalysts. These include transmission electron microscopy (TEM), laser Raman spectroscopy, electron energy loss spectroscopy (EELS), solid-state ¹³C nuclear magnetic resonance (NMR) and temperature-programmed oxidation (TPO).
Each technique provides different information about the structure and properties of deposited carbon. TPO has become particularly popular because it offers a relatively simple and effective way to measure and characterise carbon deposits directly on a catalyst.
How TPO Analyses Coked Catalysts
During temperature-programmed oxidation of coked catalysts, the instrument heats the catalyst through a controlled temperature programme while passing an oxidising gas over the sample. As the temperature increases, the deposited carbon reacts with the oxidising gas and produces carbon-containing oxidation products.
Different types of carbon deposits can oxidise at different temperatures. By monitoring these changes throughout the temperature programme, researchers can gain valuable information about the quantity, nature and relative stability of the coke present on the catalyst.
Methanation and FID Detection
Advanced TPO systems can combine methanation with flame ionisation detection (FID) to achieve highly sensitive carbon measurement. The system converts carbon-containing oxidation products into methane, which the FID can then detect and quantify with high sensitivity.
This approach allows researchers to measure very small quantities of carbon while also examining differences in the oxidation behaviour of deposits.
Improving Catalyst Performance
The information generated through TPO analysis can help researchers understand coke formation, catalyst deactivation and regeneration behaviour. This supports the development of catalysts that remain active for longer, resist carbon formation and can be regenerated more effectively.
By combining controlled temperature-programmed oxidation with sensitive methanation and FID detection, researchers can gain a clearer understanding of carbon deposition and use that information to optimise catalyst design and improve the efficiency and longevity of industrial catalytic processes.
