later switched to the lowest temperature (T), and effluent was again collected over time. Incomplete hydrotreating at lower temperatures led to increased concentrations of S, N, and O in the effluent. This implies the need for regular effluent analysis, temperature management, and guard concepts when planning long commercial cycles with oxygenated feeds to avoid over-exposure of downstream catalysts to heteroatoms. • DW/HC was performed in four reactors with catalyst
-15
40
Feed: Stabilisation HVO
Feed: HDO product (high T)
Feed: HDO product (low T)
-20
-25
30
-30
75% DW / 25% HC 75% DW / 25% HC 60% DW / 40% HC 50% DW / 50% HC
-35
20
-40
-45
10
-50
-55
0
-60
0
2
4
6
8
10
12
14
Time-on-stream (day)
Figure 4 Relative reactor temperatures of the DW/HC reactor (circles, right axis) and cloud points (crosses, left axis) of liquid effluent during DW/HC. HVO was used as stabilisation feed until time on stream (TOS) = 3.5 days, after which HDO product (obtained at the highest temperature, T + 30°C) was fed. Subsequently, DW/HC reactor temperatures were adjusted at TOS = 8 days. From TOS = 10.5 days onwards, HDO product obtained at the lowest temperature (T) was fed
stacks of DW and HC catalyst, where the total catalyst volume was kept constant. However, different ratios of DW and HC catalyst were loaded. Two reactors were filled with DW/ HC ratios of 75/25, one with 60/40 and one with 50/50. The goal of the second stage was to reach a target cloud point of ≤-26°C from a feed cloud point of +27°C while minimising gas phase loss due to excessive cracking activity. After stabilisation of the reactors, stage 1 HDO product obtained at the highest temperature (T + 30°C) was fed, leading to stable cloud points over several days (see Figure 4 ). As expected, reactors with more DW catalyst produced a lower cloud point product. Dewaxing activity was also confirmed via simulated distillation, since the sharp signals for n-paraffins disappeared in favour of a more random pattern indicative of iso- paraffins (Figure 3B). In addition, simulated distillation showed that reactors with more HC catalyst reduced the heavy tail of the boiling fraction significantly (Figure 3B inset). To approach defined target cloud points, reactor temperatures were adjusted and the resulting cloud points were close to the desired
-26°C and stable over time. To investigate the role of HDO quality on the DW/HC step, the feed was switched to HDO product obtained at the lowest temperature (T), which contained higher amounts of heteroatoms due to the lower HDO efficiency. This change in feed and HDO efficiency led to an increase in cloud points due to the inhibition of HC and DW catalysts, likely due to the presence of heteroatom species. These results highlight the need for close monitoring of HDO performance to protect downstream noble metal catalysts. More broadly, the strong influence of first-stage performance on second-stage product properties illustrates that both stages must be assessed as an integrated system, and high throughput technology provides an effective way to do so. Conclusion This study shows that field cress oil can be converted into mainly diesel-range hydrocarbons when mixed with rapeseed oil by hydrotreatment and subsequent DW/HC. This is also the case when a higher cracking degree was applied during the second step.
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