Blueprint from the interior of a catalyst

Irregularities in industrial catalysts can inhibit the conversion of crude oil, Utrecht University chemists have concluded. They were the first to provide a detailed blueprint of the interior of a commercially used catalyst for e.g. the production of transportation fuels from crude oil. They discovered a large number of dead ends. Their findings can contribute to the development of new and improved catalytic materials for the chemical industry. The study has been online published in the scientific journal Nature Materials.

In collaboration with various international research groups, Professor Bert Weckhuysen and PhD students Lukasz Karwacki and Marianne Kox of Utrecht University have studied the internal architecture of zeolite materials in great detail.

These catalysts can be compared to Swiss cheeses, containing molecular-sized holes and channels. Zeolites play a crucial role as catalyst materials in the (petro-) chemical industry to convert crude oil into transportation fuels, such as kerosene, diesel and gasoline. In this process, which is called catalytic cracking, crude oil is forced through the Swiss cheese ‘channels’ where it is split into smaller fractions. In this way, long crude oil molecules are cut up, for example, into gasoline molecules. However, the researchers discovered that not all of the zeolite channels are equally accessible.

Using a combination of various advanced microscopic techniques, the researchers created a blueprint of the catalyst showing that the materials contain a regular pattern of different channel obstructions. They found for example that a large number of zeolite channels are not open-ended. This disruption of the channel layout means the catalyst does not function optimally.

‘The molecules reach ‘dead ends’ in the zeolite crystal and the only option is to turn back,’ says Professor Bert Weckhuysen. ‘But that’s not possible, because there’s already a queue of molecules behind them. From a practical point of view, this means that the advantages of zeolite catalysts are only partially exploited.’

More information: Nature Materials; doi:10.1038/NMAT2530