110.0
16: PT3 1: PT1 14: PT1 + HC2 7: PT2 8: PT2 4: PT1 + HC1
5: PT1 + HC1 2: PT1 + HC1 12: PT1 + HC2 9: PT1 11: PT1 10: PT1 + HC2
3: PT1 13: PT1 + HC2 6: PT1 + HC1 15: PT3 Average mass balance
107.5
105.0
102.5
100.0
97.5
95.0
92.5
90.0
0
5
10
15
20
25
30
TOS (day)
Figure 2 Mass balance vs time on stream (TOS). The mass balance belonging to the same catalytic system is reported using the same colour but a different symbol. The nomenclature in the figure’s legend refers to the reactor and nature of the catalyst loaded, and reporting is as follows: ‘reactor number: catalyst label’ – this applies for all of the figures to follow
gas-to-oil ratio (GTO) are changed, it is also possible to retrieve kinetic data in several weeks rather than months. Finally, if the same catalyst is loaded in more than one reac- tor and exposed to the same conditions, statistical evalua- tion is then possible. Experimental design The study evaluates the reproducibility of both hydrotreat- ing and hydrocracking catalyst performance and ranks the different systems used. Three different hydrotreating (PT1, PT2, and PT3) and two different hydrocracking (HC1 and HC2) catalysts were tested in the conversion of vacuum gas oil (VGO) (see Figure 2 ). PT1 was used for pretreat- ment before both hydrocracking systems to ensure a fair comparison. The N slip targeted for this test was 10 ppm, aiming for conversion levels of 65%, 75%, and 85%. The reactor configuration shown in Figure 1 and the cata - lyst combination will be labelled in all subsequent graphics with the corresponding sampling position. The performance of PT1 is evaluated using positions 1, 3, 9, and 11. The other two pretreatment samples were loaded twice in the same heater. This article focuses on data reproducibility and errors associated with the measurement obtained for PT1, PT1+HC1, and PT1+HC2. The sampling position in Figure 1 corresponds to the reac- tor position. The gas phase is quantified with an online gas chromatographer equipped with a flame ionisation detec - tor (FID) to measure hydrocarbons up to C 18 . The amounts of H 2 S and NH 3 produced during hydrodesulphurisation (HDS) and hydrodenitrogenation (HDN) are measured by
subtracting the remaining S or N in the liquid phase from the total S or N present in the feed. The mass balance is then calculated by combining the gas with the liquid phase. Results The mass balance is the most important parameter for eval- uating the unit’s performance. The average mass balance (yellow line in Figure 2) of all 16 positions was between 99.5% and 100.4% once steady operation was reached. Typically, the mass balance is fine-tuned within the first week of the experiment. Position 9 had a mass balance lower than 98% for the first six days of time on stream (TOS), but this could be improved by individually heating the capillaries to the appropriate temperature, thereby ensuring equal distribution across all capillaries. The ability to heat each liquid capillary independently allowed for fine- tuning of the mass balance. This capability is particularly important when using feeds with different viscosities, giv- ing rise to a wide range of pressure drops across the capil- laries and/or when a capillary becomes partially clogged by tiny particles or crystals. The precision (expressed as repeatability) is reported in the ASTM D4629 and DIN EN15199-2 for N and simulated distillation (SIMDIST), respectively. hte’s analytical labo- ratories adhere to these quality standards through Round Robin validations, routine calibration, and maintenance of each instrument. Although the error due to repeatability of the analytical measurement is usually smaller than other experimental errors, a case-by-case interpretation of the analytical error is still required.
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PTQ Q3 2025
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