The global demand for diesel is projected to increase significantly in the coming years, fueled primarily by economic growth in developing countries. At the same time, tighter specifications in cold climates (for “winter” or “arctic” diesel) and the increasing use of waxy crudes are causing refiners to look for technologies to maximize the production of high-quality diesel with good low temperature properties.
ExxonMobil’s MIDW™ process provides the highest yields of low cloud point diesel through selective catalytic hydroisomerization of paraffins. The technology was commercialized at ExxonMobil’s Jurong Refinery in 1990 and today there are 11 operating units, with another six under design.
The MIDW process uses a proprietary catalyst that lowers the cloud point of diesel through isomerization of paraffins, as compared with older technologies that relied on cracking. This results in a much higher diesel yield, particularly for deep reductions in cloud point.
In addition to cloud point reduction, the MIDW process can also be used for endpoint extension in a hydrocracker operation using a small unit to process the heavy cut, placing a bed of MIDW in an existing ULSD unit or spare reactor in series, a two-stage operation.
The MIDW catalyst has very good dewaxing performance at low pressures and can operate at high space velocities. An example of this is shown below, where a refiner deployed MIDW catalyst in a spare hydrotreating unit to treat hydrocrackate to make -35°C cloud point diesel at a yield of 94 to 97 percent. The catalyst has been operating for nearly three years on stream and has shown few signs of aging — the refiner was able to recover their investment in only a few months of operation.
In many instances, a refiner has a need to make winter diesel for only a few months of the year. Installing a separate reactor for the MIDW catalyst would not be justified – instead, the catalyst can be “dropped in” to an existing hydrotreater, typically in the last bed, as shown below. During summer operation, the MIDW catalyst can be quenched to lower its operating temperature to avoid reducing the cloud point.
Integrated process configurations
The EMRE-UOP alliance brings together complementary technologies that are designed to make clean diesel with superior low-temperature properties. The MIDW catalyst can operate in both sweet and sour environments, with the sweet environment providing a greater reduction in cold-flow properties and at lower operating pressures.
The success of MIDW technology is based on continuous innovation at ExxonMobil. New materials and processes generated by the Catalyst and Process Technology groups are then further refined and rigorously tested for commercial applicability by Process Engineering, which also provides the technical support for unit commissioning. The MIDW catalyst has undergone several improvements since its first deployment, with the most recent one the introduction of a base metal MIDW catalyst designed especially for sour environments. The comparison with hydrotreating only and a cracking dewaxing type process is shown below — the use of the MIDW catalyst provides the best combination of cloud point reduction and yield retention.
Growing commercial deployment
Currently, 11 MIDW units are operating around the world, with six under design. While many MIDW units are located in cold climates (Russia, North America, Northern Europe), where there is a clear need for winter diesel, there are units in the Middle East, India and Singapore that produce Euro V diesel for export. The ability to retrofit an existing unit with MIDW to capture significant value makes this one of the most sought-after fuels technologies in the world today.
The BenzOUT process is a commercially proven technology for benzene reduction in gasoline. BenzOUT converts benzene typically in a light reformate stream to higher alkylaromatic blending components by reacting a benzene rich stream with light olefins, such as refinery grade propylene stream.
BenzOUT can be a grassroots unit or it can be retrofitted into an existing facility, such as a polygas unit. This technology avoids the octane loss and hydrogen consumption associated with benzene saturation alternatives. BenzOUT technology developed by ExxonMobil Research and Engineering Company (EMRE) and licensed through Badger Licensing LLC provides a unique process advantage to help refiners meet benzene regulations while at the same time achieving an attractive economic return on their investment.
Key features of the process are:
- Fixed bed catalyst technology
The process uses a fixed bed liquid-phase reactor resulting in low utility requirements.
The process utilizes an EMRE proprietary zeolite catalyst.
Propane fed to the unit with propylene is removed from the BenzOUT product in a product stabilizer. This can produce a propane product of HD-5 quality. The product from the BenzOUT technology is a light reformate with a reduced RVP.
BenzOUT economical benefits
- Meet MSAT Regulations
Reduction of benzene content in gasoline pool. Highly selective and stable catalyst enabling the process to run at a very high benzene conversion.
- Increase gasoline volume
Upgrading of light olefins and benzene into high octane alkylaromatic blendstock would also result in a volume swell of the gasoline pool.
- Increase octane
2-5 numbers of (R+M)/2 gain in a full reformate depending on the feed composition.
- Maintain hydrogen balance
Refineries could feed all the C6 components (low blending octane values) to the reformer unit to achieve increased hydrogen production and octane gain.
BenzOUT technology process configuration advantages:
- Conversion of 95+ percent of the benzene in a reformate stream
- Low temperature liquid phase process
- Octane increase
- No hydrogen consumption
- Gasoline volume swell
ExxonMobil’s SCANfining™ hydroprocessing technology offers a cost-effective solution for meeting the low-sulfur requirements of reformulated gasoline. The technology employs a unique proprietary catalyst system to selectively remove sulfur. With this proven, low-cost approach to reducing gasoline pool sulfur available from a single source, a customized system can be designed to meet the individual needs of each refiner.
- Commercially proven performance
- Demonstrated reliability
- Operating flexibility
- Options for low capital investment
- Customized solutions engineered to variety of configurations
Innovation and reliability
The approach each process takes to reducing gasoline sulfur is different.
SCANfining (Selective Cat Naphtha hydrofining) is a catalytic hydro-desulfurization process that is based on a proprietary catalyst. This robust catalyst system was developed specifically for selective removal of sulfur from FCC naphtha with minimum hydrogenation of olefins, thus preserving octane.
SCANfining can be retrofitted using existing equipment. The technology has been developed with different configurations to provide refiners the flexibility to choosing the lowest investment cost approach. ExxonMobil’s continued focus on gasoline hydrofining technology through process improvements and catalyst developments are geared towards cost-efficient investment approach to meeting the stringent gasoline sulfur specifications while minimizing octane loss.
SCANfining has been proven worldwide in successful commercial use since the 1990’s. There are 43 units operating within ExxonMobil and licensees refineries worldwide with over 1.3 Million barrels per day of capacity.
Sulfuric Acid Alkylation
Achieving more value from every cut of the crude barrel is a major refining objective. Upgrading light olefins and isobutane to alkylate offers refiners an opportunity to increase their crude barrel value. Alkylate is one of the best refinery products for gasoline blending because of its high octane and low vapor pressure. ExxonMobil’s well-proven Sulfuric Acid Alkylation technology combines propylene, butylene and pentylene with isobutane to form high value alkylate that is ready for gasoline blending.
- Lower power costs for refrigeration and mixing compared to competitive systems
- No heat exchanger inside reactor means a lower investment
- Ideal blendstock meets tough mogas specs: < 3ppm sulfur, low RVP, no aromatics and no olefins
- High octane product ready for gasoline blending
Under low pressure conditions, sulfuric acid catalyst reacts liquid isobutane with olefins (including C5’s). This efficient system removes the heat of reaction by vaporizing C4’s rather than using a heat exchanger bundle in the reactor. ExxonMobil’s economy-of-scale design allows a single reactor / settler to produce up to 11,000 barrels per day of alkylate. Due to the system’s low operating pressure, and the fact that the mixer seals are in vapor space, low maintenance mechanical seals can be used for significant cost savings. This reliable system has demonstrated run lengths greater than 4 years between turnarounds.
ExxonMobil’s Sulfuric Acid Alkylation process is operating in 16 units spanning nearly 60 years of commercial experience with over 230,000 barrels per day of capacity. The installed capacity ranges from 3,000 barrels per day to the largest alkylation unit in the world at 83,000 barrels per day. This vast experience has resulted in cost and reliability improvements that are incorporated in new plant designs.