Oct-2016

Maximising the diesel yield from hydrocracking (TIA)

The hydrocracker is one of the most profitable units in refineries, partly due to the volume swell, and partly because it converts heavy feedstocks into naphtha, jet fuel, diesel, and other high-value products.

Kiki larsen
Haldor Topsoe

Article Summary

Even unconverted oil can serve as a high-quality feedstock for FCC units or steam crackers.

Unique solutions
The following targets may apply for a hydrocracker unit: improving the cold flow properties or cetane number of diesel, improving the quality of jet fuel, reducing hydrogen consumption, improving hydrogenation, making unconverted oil for lube oil production or ethylene crackers, or improving the diesel yield. Choosing the optimal catalyst depends on the unit objective and compliance with the specific product properties. Meeting parameters at typical pressures in the 60–200 bar range can be challenging, and the cycle lengths are often determined, not by conversion rates, but by a failure to comply with specifications. Topsoe has developed three series of hydrocracking catalysts (see Figure 1) for optimal unit performance.
 
The changing market
In the refinery business, market shifts are expected. Changing objective or specification requirements open up for a more optimal choice of catalyst. The key is providing the refineries with new technology, equipping them to adapt to and take advantage of the ever-changing conditions.

In order to be able to sell unconverted oil product for lube oil production, a European refinery had a product specification for the viscosity index. However, due to market shifts, the specification was removed. Even though the refinery was satisfied with the performance of their previously installed catalyst, Topsoe advised the refinery to initiate a ramp-up towards greater middle distillate yields. The refiner did so by choosing the TK-939 D-sel catalyst. This catalyst met the refinery’s KPIs for increasing middle distillate yield and improved the unit’s margin contribution consistently over time.

Selecting TK-939 D-sel resulted in a significantly higher middle distillate yield, without compromising the activity. The net diesel yield vs true conversion from the previous cycle vs current cycle at the refinery is illustrated in Figure 2. Besides increasing the middle distillate yield by 4 wt% for a minimum cycle of 18 months, the cloud point was also improved by 5-8°C.

The increased net diesel yield corresponds to an additional 450 000 barrels of diesel for a unit cycle of 18 months.

TK-939 D-sel and TK-949 D-sel are part of Topsoe’s hydrocracking D-sel series for maximum diesel yields. They are both catalysts with high selectivity for middle distillates and, as a result of novel production technology, they provide an excellent middle distillate yield with low yield of light ends.

For more information: kikl@topsoe.dk