Catalysis 2023 Issue

catalyst application, and location. Optimised process designs are just one aspect of the overall solution, with biofeed sup- ply logistics very often being the overall controlling factor determining the most attractive co-processing opportunity. A Joris Mertens, Principal Consultant, KBC, joris. mertens@kbc.global Renewable feeds are either lipids (vegetable oils and ani- mal fats) or lignocellulosic material. The main strategic challenge around processing these renewable feeds is feed procurement. The first HVO/HEFA plants were mainly processing palm oil. However, the EU and, to a lesser extent, the US are nar - rowing the possibility to process such controversial feeds that pose substantial land-change issues. At the same time, REDIII, ReFuelEU legislation in Europe, and similar initia - tives in the US and elsewhere have further incentivised the demand for lipid-based mid-distillate production from HEFA technology, and specifically SAF. In about five years, only a limited amount of waste oils and fats is expected to be available for new projects. Despite its attractive lower cost and fewer feed sup - ply challenges, co-processing in existing units does not address the long-term (post-2030) decarbonisation chal- lenge, which will require a deeper cut in the carbon inten- sity of fuel than co-processing can deliver. Theoretically, technologies using lignocellulosic wastes should pose less of a concern with feed availability. However, raw lignocellulosic stock is much less energy dense. Therefore, they must be sourced from shorter dis- tances, typically less than 200km, which brings feed supply assurance to the forefront of strategic considerations. Pre- processing lignocellulosic material, for example pelletising or pyrolysis, can largely address the energy density issues but may add complexity to the feed supply chain. In addi - tion, technological maturity and required capital cost are more challenging for processes using lignocellulosic feeds. In addition to feed and technology readiness and cost, an optimised strategy needs to consider the product yield structure, which varies widely depending on feed type and technology, including catalyst technology. While the catalyst type impacts HVO yields significantly, with potential differ - ences up to 5%, unit configuration and catalyst type will dra - matically affect the SAF yield of Fischer-Tropsch complexes. A Stefan Brandt, Market Development Director, Energy Transition, W.R. Grace & Co., stefan.brandt@grace.com The terms second- and third-generation renewable feedstocks are not defined globally. In a briefing of the European Parliament in 2017, second-generation biofuels were “derived from waste and agricultural residues (such as wheat straw and municipal waste) or non-food crops (such as miscanthus and short-rotation coppice).” 1 Third- generation renewable feedstocks are often referred to as being related to algal biomass, for example. While there are several process units capable of process- ing second- and third-generation feedstocks, the flexibil - ity of the FCC unit is well suited for the co-processing of unconventional feedstocks. However, challenges exist in

Figure 1 Testing the miscibility of second-generation renewable feedstock in VGO

the industry to establish a continuous supply of renewable feedstock components, especially for second- and third- generation renewable components. Availability of some of these is expected to grow over the coming years. Therefore, any strategy for co-processing these feedstocks needs to start with a reliable sourcing plan. The optimal strategy for co-processing renewable feed- stocks in an FCC unit is always related to a deep under - standing of the properties of the feedstock component in terms of storage, miscibility, physical and chemical proper- ties and its impact on the operation and yield structure of the FCC unit. Thorough characterisation and catalytic pilot plant testing are recommended to identify the opportuni- ties and challenges. Second-generation renewable feedstocks typically exhibit higher variation in quality compared to first-gener - ation renewable feedstocks derived from edible oil sources. Additionally, miscibility with conventional feedstock can be challenging (see Figure 1 ). The FCC unit can cope with feedstock quality variation because of its flexibility in oper - ation and catalyst design adaptability. Nevertheless, the variability of the renewable feedstock component might put additional emphasis on the regular FCC unit monitoring. Depending on the nature of the renewable feedstock, hardware modifications might be required to prevent reli - ability risks from co-processing. Technology licensors have developed hardware solutions to minimise these risks and optimise the catalytic conversion of the combined feed. The FCC unit, with its flexibility in catalyst formulation and replacement, is able to adjust to challenges coming in with various feedstock contaminants. Renewable feedstocks bring other contaminants to the FCC unit than crude-derived feedstocks. At low co-processing percentages, depending on the operation, the effect on catalyst deactivation is often unnoticed. However, increased co-processing rates will ultimately put more emphasis on the risks associated with new contaminants in the FCC unit. FCC catalyst suppliers can provide solutions and recommendations based on the individual refinery strategy, operation, and objective.

Catalysis 2023