X-ray Method Unveils How Oil Refinery Catalysts Get Clogged

Catalyst particles used to make gasoline industrially become inactive because of metal contamination that clogs pores at the particles’ surface, according to a high-resolution imaging study (Sci. Adv. 2015, DOI: 10.1126/sciadv.1400199). The findings showcase the analytical power of a new X-ray nanotomography method and suggest ways for extending lifetimes of catalysts used globally for petroleum refining. Worldwide, some 450 refineries employ fluid catalytic cracking (FCC) to convert long-chain molecules in crude oil to shorter, more valuable compounds, including ones used for formulating gasoline. During FCC, the catalyst particles—which typically consist of microporous zeolites, clays, and a binder—accumulate metals from crude oil and refinery equipment and undergo irreversible deactivation. By analyzing fresh samples and ones of various ages collected from commercial FCC units, a team led by Bert M. Weckhuysen of Utrecht University, in the Netherlands, found that iron and nickel accumulate at the entrances to “wide” nanometer-sized pores at the particle surfaces. The metals thus block feedstock molecules’ access to the catalytic sites, which are located in narrower interior pores and remain uncontaminated. Coating the zeolites with a macroporous layer may slow deactivation, the team suggests.