Catalysis 2025 Issue

Isodewaxing catalyst. In addition, the trademarked ReadiJet and ReadiDiesel, produced from the biofuels Isoconversion technology, contain a uniform distribution of all hydrocar- bon types observed in petroleum fuels, including aromatic, cycloparaffin, isoparaffin, and normal paraffin compounds, and can be directly blended with petroleum fuels. The pro- cess is differentiated from a pure hydroprocessing approach by the production of glycerine rather than propane as a side product. The Isoterra process is an all-hydroprocessing route that can be operated to maximise yields of ASTM-approved RD or SAF. The two-step process involves hydrodeoxygena- tion of the feed followed by dewaxing to meet final cold flow property specifications. The dewaxing step likewise uses CLG’s Isodewaxing catalyst. The Isoterra process is suited for revamping existing hydrotreaters to renewables service as the process can be implemented in either one or two-stage configurations. CLG and Grace’s proprietary Hydroprocessing (ART) have introduced catalysts to the marketplace branded as Endeavor systems, which will include the proprietary EnRich HDO catalysts and the pro- prietary EnHance dewaxing and hydrocracking catalysts for general application to renewable feedstock applications. Figure 1, other than the upflow reactor (UFR) component, is illustrative for most two-stage HEFA processes and clearly indicates recycle liquid flows for quench and selectivity purposes.² Shell Catalysts & Technologies licenses the Shell Renewable Refining Process, incorporating the Shell SRC portfolio of renewables hydroprocessing catalysts. The pro- cess is a two-stage process, which Shell maintains offers multiple benefits over single-stage units, including higher diesel and SAF yields, longer cycles and slower yield decline, and the ability to produce a range of cloud points that qual- ify for any RD market in any season, plus the flexibility to swing between diesel and SAF. ExxonMobil Catalysts & Licensing offers its proprietary ExxonMobil Renewable Diesel (EMRD) two-stage pro- cess for RD production. It can produce jet if fractionation is added. The process was introduced in September 2021 and incorporates ExxonMobil’s Bio-Isomerization Dewaxing (BIDW) dewaxing catalyst suite. ExxonMobil notes that its BIDW dewaxing catalyst suite provides solutions that meet cold-flow specifications for RD to improve yield in either two-stage or single-stage service applications. Alcohol-to-jet technology Ethanol-to-jet processes are seeing more imminent com- mercialisation. The technologies involved, including ethanol dehydration, olefin oligomerisation, and olefin hydrogena - tion, are all mature catalytic technologies. Solid phosphoric acid catalyst (SPA) was developed in the 1930s for the UOP CatPoly oligomerisation process, and homogeneous Ziegler-type catalysts for oligomerisation were developed in the early 1950s. A variety of solid acidic catalysts can be used for dehy- dration, ranging from g -alumina and silica-aluminas to mixed oxides and zeolites. Oligomerisation can either be carried out in heterogeneous systems utilising SPA-based, acid ion

exchange resin-based catalysts or zeolite-based catalysts or conversely in homogeneous systems employing nickel and aluminum alkyl-based catalysts. Hydrogenation of the linear and branched oligomer olefin products is straightforward, basic hydroprocessing. Technology providers for the dehy- dration step include: • Axens * : Atol ATO-201 catalyst (ZSM-5 based). • Lummus-Braskem: SynDol catalyst (Al 2 O 3 -MgO/SiO 2 ). • Technip: Hummingbird (supported heteropoly acid catalyst). • KBR-Petron: K-SEET (likely g -alumina-based catalyst) • Honeywell UOP. Oligomerisation technology providers include: • Axens * : Dimersol, Polynaphtha (homogeneous Ziegler- type nickel hydride and aluminum alkyl system, heterogene- ous amorphous silica-alumina IP 811 catalyst). • UOP: CatPoly, InAlk, Catolene components (SPA or acid resin catalyst). • Lummus: Dimer Process, Light Olefins Oligomerisation (homogeneous butenes production, subsequent oligomeri- sation not specified). * Axens refers to its combined process as Jetanol. The first small commercial-scale ethanol-to-jet operation is the LanzaJet facility in Soperton, Georgia, which started up early in 2024, benefiting from funding from the US DOE. It has a capacity of 10 million gal/year (38 million litres/ year, 660 bbl/day) SAF produced from low-carbon inten- sity ethanol. Ethanol from sugarcane is approved by the US EPA for the facility and is being sourced from Brazil. It employs the Technip Hummingbird dehydration process and a two-component oligomerisation process developed at the Pacific Northwest National Laboratory (PNNL). The first step utilises a mixed Zn-Zr oxide catalyst developed at PNNL, and the second likely employs either a zeolite catalyst or an acid resin catalyst. LanzaJet has SAF offtake agreements with British Airways and ANA. Ethanol-to-jet facilities will generally require a greenfield or brownfield site owing to limited opportunities to repur - pose existing infrastructure and equipment. Processes for SAF via FT-SPK The starting point will typically be the conversion of ligno- cellulosic material, such as biomass waste from agricultural or forestry production or municipal solid waste (MSW) by gasification, a mature technology. The resultant syngas (CO + H₂) will have significant impurities and typically a low H₂/CO ratio (~0.5 vs >2 desired), requiring appreciable pretreatment efforts to remove impurities prior to catalytic steps. Adjustment of the H₂/CO ratio is affected through high- temperature and low-temperature water gas shift (WGS) reactors using catalyst technologies that have been proven for decades in the hydrogen and ammonia production industries. The high-temperature shift catalyst is typically a promoted Fe-Cr oxide-based catalyst, and the low-temper- ature shift catalyst is typically a Cu-Zn-Al oxide formulation. The FT process dates back to 1925 and, therefore, has a century of catalyst development and reactor technology improvements to tailor product selectivity and accommo- date the highly exothermic FT reactions. For SAF purposes,

Catalysis 2025