PTQ Q4 2025 Issue

105

100

Avg. mass balance (wt%)

TOS (day)

Figure 2 Mass balance

choosing this reactor setup was hte’s ability to run the test with a reactor configuration as depicted in Figure 1 and to do so for eight systems in parallel. To accurately simulate commercial operation, a recycle of unconverted oil was sim - ulated between the hydrotreating (HT) and hydrocracking (HC) reactors using a ‘bleed oil’ feed provided by the refin - ery. In order to exclude any possible hydrogen starvation of the catalysts, extra hydrogen was added to match the exact gas-to-oil ratio (GTO) provided in the commercial unit. The testing campaign was conducted using a 24-fold trickle bed unit at hte’s laboratories in Heidelberg. This type of unit can be used for any hydroprocessing application from naphtha hydrotreating to atmospheric residue desulphuri - sation, as well as hydrocracking and hydrotreating renewa - ble feeds. This unit features two feed pumps, each placed in separate ovens, and two independent hydrogen mass flow meters. Each liquid feed is pumped through its own set of stainless-steel capillaries and split into 16 streams. Similarly, each hydrogen mass flow controller directs the gas through its own set of glass capillaries, dividing the hydrogen flow into 16 different channels. For the test, each catalyst vendor provided a pretreatment and a hydro - cracking catalyst set, which were loaded into two different reactors connected in series. To control the nitrogen (N) slip, a third reactor was loaded with the pretreatment catalyst set. The two reactors loaded with the same pretreatment catalysts shared the same heater for each vendor, ensuring consistent system behaviour. The test was run with a time-on-stream (TOS) of 50 days. The first five days following catalyst activation were used to line out all the catalysts at the same temperature. Afterwards, all the pretreatment reactors were set to the same temperature to directly compare the different N slip among all the options. The hydrocracking reactors were also working at the same temperature for the first condi - tion, and the temperature was then increased or decreased by 10°F according to the conversion observed. The last

two conditions had a variable temperature that depended on the activity of the catalysts. Each condition targeted a conversion level at a constant N slip (200 ppm). Additional economical evaluation that ultimately led to the catalyst choice is outside the scope of this publication. Results: mass balance The mass balance, which indicates how well the unit is run - ning, is reported in Figure 2 . It can be observed that the average mass balance (black solid line in both panels) was oscillating around 100% for the whole experiment. The other coloured solid lines represent the mass balance for each individual reactor, where the HT reactors are shown in the left panel and the HC reactors are shown in the right one. After the first 10 days of operation, the mass balance was optimised and oscillated steadily between 98% and 102%. The first few days are needed to fine-tune the unit in terms of flows and temperatures upstream and downstream of the reactors. While the mass balance is 100 ±2% for all reactors, it can be observed that the HT mass balance is, in general, higher than the HC mass balance. This can be due to the lighter product obtained at the outlet of the HC reac - tors. A small fraction of the light end may have evaporated, thereby causing this systematic effect. Another less likely possibility could be connected to the different pressure drop caused by only one reactor (HT) and two reactors in series (HT + HC) (reactor configura - tion report in Figure 1). The difference in pressure drops between the two sets of reactors (on the order of 0.1 to 0.5 bar) is, however, negligible with respect to the pressure drop that both liquid and gas flows experience in the capil - laries (20 to 30 bar). N Slip and hydrocracking-conversion In the Figures 3 , 4 and 5 , the catalyst sets are named with a letter from A to H. The respective pretreatment reactor

PTQ Q4 2025