3 H
+
HDO Hydrodeoxygenation
R-CH + 2 H O
O R C
Fatty acids reactions to n-para ns
R-H + CO + H O R-H + CO
DCX Decarboxylation DCN Decarbonylation
Loss of 1 C-atom
+ H
OH
Figure 6 Fatty acid reaction pathways to n-paraffins
Typical reactions In a hydrotreater, triglycerides undergo saturation and crack - ing to form FFA. Then the FFA are converted to n-paraffins by three different mechanisms (see Figure 6 ): HDO, decar - boxylation (DCX), and decarbonylation (DCN). HDO is the preferred mechanism, which returns maximum distillate yield. DCX and DCN produce undesired gas yields in the form of COâ‚‚ and CO, which reduce distillate yields. Additionally, CO is detrimental to cycle lengths because it inhibits HDS reactions in co-processing. This inhibition can be up to 10°C in weight average bed temperature (WABT) with only 5% renewable feed. Other heavy molecules such as sterols, or tocopherols present processing challenges like pressure drop issues. In addition to these organic contaminants there are also mul - tiple non-organic contaminants like phosphorus, chloride, silica, and metals like iron that can block active site. Of these, phospholipids have the highest impact on the catalyst from the phosphate group, which deposits at cata - lyst pores mouths, causing severe pressure build-up and catalyst deactivation. Contaminant management Selective optimisation of the guard section of the reactor is required to mitigate the impacts of these impurities. Ketjen has introduced more proficient guard and HDO catalysts for these tasks to support refiners in this manner. KG 56 is the latest introduction in the KG portfolio. KG 56 is an inert, mac - roporous guard grade designed to pick up particulates, scale, and gums formed by condensing unsaturated compounds in renewables feedstocks. ReNewFine catalysts are guard and HDO grades for processing renewables, including 100% vegetable oil hydrotreating. The ReNewFine 100 series consists of guard
hydrodemetallisation (HDM) catalysts with the main purpose of trapping phosphorous and alkaline metals (Mg, K, Na, and Ca). Their design mitigates pressure drop risks and protects the HDO and hydrotreating catalysts from metals poisoning. Scanning electron microscope (SEM) analysis of ReNewFine 101 reveals the very deep penetration of phos - phorous in the catalyst pores compared to a conventional phosphorous guard grade (see Figure 7 ), setting a new stan - dard for protection from phosphorous. The ReNewFine 200 series catalysts are dedicated to HDO. They selectively remove oxygen from the fatty acid chains in bio-feeds while minimising the formation of CO and CO2, which results in improved cycle length and liquid product yield. Existing hydrotreater conversion without revamps The ReNewFine catalysts and ReNewSTAX loading strategy have made it possible to maximise renewables processing without the need for major revamps. A refinery was rapidly forming a coke crust at the reactor top, resulting in rapid pressure drop build-up before talking to Ketjen. However, an optimised ReNewSTAX loading was proposed. With the ReNewSTAX solution, the refinery managed to co-process renewable feeds with a high content of polyolefins and miti - gated their pressure drop issues (see Figure 8 ), thus avoid - ing a new guard bed in the capital project. Clean fuels solutions – pyrolysis oils We are also busy applying our experience in mineral and renewable oils to research circularity topics like waste plas- tics recycling. The environmental impact of waste plastics has been a cause of concern since the 1970s. In particular, the durability of plastics is an attribute that has proven valu - able for society but problematic for waste management.
Figure 7 SEM imaging of phosphorous trapping – conventional guard (a) vs ReNewFine 101 (b)
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