May-2020

It’s all in the pores

Since Standard Oil first demonstrated that mysterious materials called catalysts can deliver a lot more bucks from a barrel of crude, catalysis has played a key role in the development of petroleum refining as an efficient producer of fuels and much more besides.

Chris Cunningham
PTQ Editor

Article Summary

As this issue of PTQ Catalysis demonstrates, the level of innovation in the development of refining catalysts never slackens, whether the goal is to glean more – and more valuable – products from deeper and stickier post-distillation fractions, to achieve more efficient production of light olefins as petrochemicals feedstocks, or to achieve faster and more in-depth understanding of catalysts’ performance.

But for petroleum refiners there are always challenges to overcome other than more value and higher margin. Foremost and for the foreseeable future, one of the biggest of these is external pressure to reduce carbon dioxide emissions from refinery processes.

Perhaps catalysis also has a major role to play in tackling these emissions. For instance, a consortium of academic researchers from Europe and Australia has attracted some attention recently. The researchers reckon that they have developed a catalyst that will “significantly reduce” the amount of CO2 produced by refiners. To sum up briefly, they have developed a type of aluminium silicate, the basis of zeolite structures, with acid activity that is stronger than any other silica-alumina material created. This, they reckon, could cut CO2 emissions in refineries by 20%.

This is all well and good, but taking the academics’ work to commercial usefulness will be a much bigger step than simply devising a novel material.
Experts from the leading catalyst developers explain the issues with far greater eloquence in the pages of PTQ publications, but a summary of catalyst performance is this: all depends on pore structure and active sites. For a zeolite catalyst to be as effective as possible in its chosen role, access to its active sites and passage of feed and product through the catalyst must be as efficient as possible. Zeolites have a basic structure of micropores; appropriately designed with ‘mesopore’ or other inclusions, they can act more efficiently in the selective transport of feed and product.
The acid sites which catalyst feed encounters are important early stages in catalytic cracking reactions. Hence, their accessibility and location are fundamental to how useful a zeolite is as a catalytic performer. If the sites are on the outside surfaces of a zeolite, access to them is simple. Inside the zeolite, the pore structure is crucial to determining access. The chemical structure of the zeolite then comes into play. The distribution and function of acid sites can be altered by, for instance, changing the aluminum to silicon ratio, or by introducing alkaline earth metals.

The aluminium silicate material developed by the academics introduced earlier features high activity involving Brønsted acid sites which have been shown to be important if you want to avoid secondary reactions leading to unwanted products, CO2 for instance.

This short article was the editorial forward in the Catalysis 2020 issue of PTQ.

You can view the issue HERE