CLG's ISOCRACKING fixed bed hydrocracking technology converts naphthas, AGO, VGO, DAO, cracked oils from FCC units, delayed cokers and visbreakers, and intermediate products from residue hydroprocessing units into:
CLG introduced the ISOCRACKING process in 1959, making it one of the first low-pressure, low-temperature catalytic hydrocracking technologies. The technology has been continuously developed over more than 60 years, with CLG licensing over 60 units from 2000 to 2021.
Table 1 - ISOCRACKING produces a highly isomerized Product slate
| Heavy Naphtha |
high ring content |
>60 LV % |
| Diesel |
Low pour point
High cetane |
-30°F (-35°C)
50-62 |
| Jet/Kerosene |
Low freeze point
High smoke point |
-60°F (-51°C)
25 mm+ |
| Waxy Base Oil |
High VI |
>110 |
| Ethylene Cracker Feed |
Low BMCI |
6-16 |
| FCC Feed |
Low Sulfur
Low Nitrogen |
5-300
1-50 |
Process Description
A broad range of both amorphous/zeolite and zeolitic catalysts, including noble-metal zeolitic catalysts, are used to tailor the ISOCRACKING process to the refiner's objectives . In general, the process involves a staged reactor system with an initial stage of hydrotreating and partially hydrocracking the feed, and a subsequent stage continuing the conversion or product upgrade process in a more favorable environment .
The second-stage environment in two-stage configurations permits full conversion of difficult feeds with less than half the reactor volume needed compared to single-stage designs.
Figure 1 - Feed Conversion vs. Catalyst Character
Process Configurations
ISOCRACKING is offered in several designs for all types of configurations, including:
- Single-Stage Once-Through (SSOT)
- Single-Stage Recycle (SSREC)
- Two-Stage Recycle (TSREC)
ISOCRACKING SSOT configuration produces feedstocks with superior characteristics for FCC feeds, high VI lubes or ethylene plant feeds . Latest development for SSOT employs a moderately high-pressure design in conjunction with a tailored catalyst system that provides hydrodenitrification and high hydrocracking activity.
ISOCRACKING SSREC configuration is used for high conversion processing of light feeds and for low capacity units processing heavy feeds at low feed rates.
ISOCRACKING TSREC is optimized for maximum yields of premium products with minimum hydrogen consumption . The first stage removes feed impurities and converts 20-50% of the feed . The second stage cracks the cleaned feed at lower temperatures.
Figure 2 - ISOCRACKING Two-Stage Recycle Configuration (TSREC)
Most modern large-capacity flow schemes involving heavy sour gas oils require two reactors (1) & (4) and one high-pressure separation system (2) with an optional recycle gas scrubber (5) and one recycle-gas compressor (8). The low-pressure separators (3), product stripper (6) and fractionator (7) provide the flexibility to fractionate products either in between reaction stages or at the tail-end, depending on desired product slate and selectivity requirements.
ISOCRACKING for Lube Oil Base Stock Production
When applied to lube oil base stock production, ISOCRACKING hydrocracking boosts Viscosity Index (VI) by chemically converting low VI components to higher VI base oils. Unlike solvent refining processes that produce raffinate and a highly aromatic, low-value extract, the by-products of ISOCRACKING include valuable transportation fuels such as gasoline, jet and diesel.
For a given feedstock (typically VGO and/or DAO), the ISOCRACKING process creates higher VI components and preserves more molecules in the base oil boiling range than solvent refining. This gives refiners the flexibility to produce higher base oil yield for a target VI or higher product VI when processing to an equivalent yield level.
References
- Chevron Lummus Global. ISOCRACKING® Brochure (2021)
- Dahlberg A.J. et al. Improved Zeolitic Isocracking Catalysts. Conference paper (Sep 1, 1995). Office of Scientific and Technical Information (OSTI)
- Jack (17 Jun 2019). Hydrocracking Process by Chevron. Oil & Gas Process Engineering
- Chevron Lummus Global. CLEAN FUELS / ISOCRACKING
