Developing game-changing catalysts

The invention of a second-generation Fischer–Tropsch (FT) catalyst was key to Shell’s new world-scale Pearl GTL plant in Ras Laffan, Qatar, as it significantly enhanced the plant’s economic viability. Impact explores the catalyst’s development cycle and the outlook for further innovations in this area.

“The first-generation FT catalyst enabled Shell to build and operate its first commercial GTL plant, Bintulu, Malaysia, which was a critical milestone on the path to the Pearl plant,” says Alan Del Paggio, Vice President, Upstream and Renewables, CRI Catalyst Company (CRI). “It was a good catalyst but it lacked the necessary activity, selectivity and stability for it to be used in a larger plant because it would have required exceptionally large – and costly – reactors.”

The key to cost efficiency for any industrial operation is scale, and GTL technology is no exception. In 1999, when Shell was planning the enormous 140,000-barrels-a-day Pearl plant, the research and development teams at Shell’s petrochemical catalyst company, CRI, and the Shell Technology Centre Amsterdam, the Netherlands, were tasked with the commercialisation of a research and development prototype of a next-generation FT catalyst. The principal objective was to achieve greater reactor productivity at equal or improved selectivity to liquid products, as this would help to extract the maximum value from the Pearl plant’s economies of scale.

An FT catalyst is used at the heart of the GTL process. It is distributed throughout tens of thousands of tubes inside all 24 of the plant’s fixed-bed reactors, where it converts synthesis gas, a mixture of carbon monoxide and hydrogen, into high-value synthetic paraffins. After several years of dedicated scientific investigation, the research and development teams had created a proprietary advanced synthesis catalyst with a different formulation, chemistry, base material and manufacturing process to the first-generation catalyst. Crucially, its activity was almost twice that of its predecessor, which doubled the amount of liquid that the reactors could output.

“The new catalyst, called the second-generation catalyst, was, in essence, a step change in FT fixed-bed technology,” says Del Paggio. “The teams’ scientific rigour had unlocked a greater understanding of catalysts at the atomic level.”  

A key part of the development process was scaling up the process. As Del Paggio explains: “We use various tools to scale things up. For instance, we first evaluated the new catalyst in the Amsterdam laboratory’s micro-reactors before moving on to larger pilot plant tests. Eventually, in 2000, it was commercially demonstrated in the Bintulu plant.”

In fact, the new catalyst helped to significantly debottleneck the Bintulu plant with relatively minor capital modifications. Because it now has higher productivity per reactor volume and a better selectivity for liquid products, the plant’s capacity has increased from 12,500 to 14,700 barrels a day of high-quality GTL products. This commercial demonstration was key to the improvement cycle because it provided a highly valuable opportunity for Shell to gain operational experience of the catalyst’s performance under industrial conditions.

Following the success at the Bintulu plant, the decision was made to design the Pearl plant’s FT section on the basis of the second-generation catalyst. Even then, however, it took some four years for sufficient catalyst volumes to be manufactured for the giant Pearl plant; in fact, it was the world’s largest ever catalyst supply contract. CRI used dedicated facilities in Europe at full-time production to provide the thousands of tonnes of catalysts needed. 

A new, larger plant started up in 2011 and the catalyst produced from it is performing as anticipated. Nevertheless, Del Paggio reveals that third- and fourth-generation catalysts are in different stages of development in Amsterdam and at CRI. “We are exploring many potential leads for next-generation catalysts to retrofit in the Pearl and Bintulu plants. We are going through the scale-up process right now – from laboratory-scale tests to micro-reactors to pilot plant tests, and then the new catalyst could enter service at either plant.

Operational feedback is a key input to the research and development teams, who have regular meetings with representatives from the Bintulu and Pearl plants. Of course, activity is just one aspect of a catalyst’s performance and the research and development teams are also considering various different approaches that may offer, for instance, enhanced conversion, higher selectivity, better stability, improved resistance to contaminants or longer life.

With each new variant, Shell is extending its knowledge and understanding of the chemical reaction at the heart of the GTL process and getting progressively higher yields and longer service life.
The catalysts will be replaced periodically, one reactor at a time to minimise the impact on production. CRI is responsible for the reclamation of the valuable metals in the used catalysts to make fresh catalyst, which contributes to a more sustainable and economically attractive catalyst life cycle.

“There will always be a very heavy emphasis on catalyst research and development because the potential economic rewards are so compelling,” says Del Paggio. “The catalyst has an enormous impact on the economic and commercial success of a project such as the Pearl plant, as it determines the efficiency of the conversion process. The more efficient the catalyst, the better the productivity of the project and the greater the financial return.

"Moreover, once you have spent the capital to build a plant like Pearl, the most cost-effective operational enhancements are most likely to be achieved through catalyst improvements; hardware changes are typically much more capital intensive. A next-generation catalyst is usually designed to drop in without substantial capital modification.”

For more information contact Alan Del Paggio.

^{*CRI Catalyst Company is part of CRI/Criterion Inc.}