Catalysts for renewable fuels production Catalysts play an essential role in renewable fuels production and can help to overcome the challenges associated with processing renewable feedstocks
Henrik Rasmussen Topsoe
T he global energy landscape is undergoing constant change as energy security and diversification shape the future of fuel. Among the most promising avenues in this transition is the production of renewable fuels, which offer a viable alternative and supplement to traditional fossil fuels. Hydrotreating is a ubiquitous technology present in every refinery in the world. It is commonplace for a refinery to have several different hydrotreating units, each designed and optimised to treat different fractions from the initial distillation of crude oil, including naphtha hydrotreaters, diesel hydrotreaters, and FCC pretreat units. The process conditions and catalyst systems are tailored to the specific requirements of the different feed streams while meeting the required specifications for each product stream. At one level, adapting hydrotreating technology to process renewable feedstocks to produce hydrotreated esters and fatty acids (HEFAs) represents one of the lowest-cost, easiest-to-implement options in the transition from fossil to renewable-based products. However, the production of renewable fuels for both existing refiners and new producers is not without its challenges when it comes to the catalytic processes involved. The catalyst system must be designed to manage the specific characteristics of renewable feedstocks and produce high-quality fuels. This article explores the critical role of catalysts in renewable fuels production, the challenges associated with processing renewable feedstocks, and the innovative solutions that are driving the industry forwards.
Complexities of renewable feedstock processing Hydrotreating catalyst systems have evolved over the years such that most units today are loaded in layers of catalysts, each with different catalytic functions. The top layer comprises guard bed catalysts specifically designed to remove contaminants such as nickel and vanadium metals from fossil feed streams while minimising the build-up of pressure drop to ensure this function does not limit the operating cycle of the unit. The next layers comprise catalyst developed for maximum hydrogenation efficiency to remove sulphur and, if needed, also saturate aromatics. The system may include catalysts to remove nitrogen if this is required (for example, for hydrocracking units). At the bottom of the hydrogenation unit is a catalyst layer designed to minimise sulphur recombination. Renewable feedstocks, such as vegetable oils, animal fats, and waste oils, pose unique challenges compared to traditional fossil- based feedstocks. The complex reaction mechanisms involved in hydrotreating renewable materials differ significantly from those of conventional petroleum refining. If catalysts are not specifically designed to handle hydrotreating renewable materials differ significantly from those of conventional petroleum refining ” “ The complex reaction mechanisms involved in
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