|  | XyMax (Xylene Isomerization)
ExxonMobil Chemical's XyMax and Advanced MHAI Processes
ExxonMobil offers two highly selective xylene isomerization processes - XyMax and Advanced MHAI - for commercial licensing to produce paraxylene and/or orthoxylene from feedstocks rich in C8 aromatics. These technologies can be easily retrofitted into your existing equipment, where they can debottleneck operations, boost product yields, increase profits, and provide more flexibility than competitive processes. XyMax (sm) services provide full support for licensees from initial consultation through technology transfer and on-going improvements.
- High Ethylbenzene Conversion with Low Xylenes Losses
- Advanced Catalyst Technology
- Over 35 years of commercial experience
- A Simple Fixed-Bed Process
| High Ethylbenzene Conversion with Low Xylene Losses
Designed to meet specific plant needs, the XyMax and Advanced MHAI processes can debottleneck operations by maximizing ethylbenzene (EB) conversion while minimizing xylene losses. For sites with lower reactor temperature limitations, and for those that utilize crystallization for paraxylene separation, the Advanced MHAI Process offers optimum operation. For sites with higher reactor temperature capability, and for those that utilize adsorptive paraxylene separation technology, the XyMax Process is the best choice. The XyMax and Advanced MHAI processes each can offer significant advantages over competitive processes, such as:
- Higher throughput and paraxylene production
- 100% plus paraxylene approach to equilibrium throughout the operating cycle
- Lower operating costs - up to 25%
- Lower catalyst requirement
- Long operating cycles and ultimate catalyst life
| Advanced Catalyst Technology
The XyMax and Advanced MHAI processes incorporate the latest advances in ExxonMobil's zeolite catalyst technology. Using a unique dual-bed catalyst system with each bed tailored to perform specific functions, these processes optimize EB conversion, non-aromatics cracking, and the isomerization of metaxylene and orthoxylene to paraxylene. Users may take advantage of these features to increase the capacity of an existing unit by up to 30%. This plus the superb stability of ExxonMobil catalysts could result in remarkable long-term benefits.
| Over 35 Years of Commercial Experience
Since their introduction in 1973, ExxonMobil xylene isomerization technologies have been licensed for use throughout the Americas, Europe, Middle East, and Asia in 23 different plants. Many of our licensees have used earlier generations of our isomerization technologies, and then upgraded to the latest technology as improvements have been developed. More than one third of the world's paraxylene capacity uses ExxonMobil technology. Most of this capacity was low-cost conversions of other processes. Excellent catalyst stability has been demonstrated by a number of different licensees in a variety of retrofit and grass-roots units. One plant operated more than twelve years without regeneration.
The Advanced MHAI Process was introduced in 1999 at Chalmette Refining L.L.C.'s Louisiana refinery. Rapid acceptance in the marketplace has resulted in ExxonMobil already having over thirty cumulative years of commercial experience with Advanced MHAI. In addition to the Chalmette unit, there are four Advanced MHAI units in Asia and two more units in North America. Customers have taken full advantage of Advanced MHAI by operating over a wide range of EB conversion.
In 2000, just one year after the introduction of Advanced MHAI, the first commercial application of the XyMax Process took place at ExxonMobil's Jurong Refinery in Singapore. This unit currently pushes the limit in EB conversion to maximize unit capacity, while maintaining low xylene losses and excellent catalyst stability. Since Jurong started-up, eight additional XyMax units have started up and are operating successfully and five more grassroots units have been licensed.
| A Simple Fixed-Bed Process
The following process flow is typical for a vapor phase reaction in a fixed-bed reactor. In the XyMax and Advanced MHAI processes, feed is a mixture of fresh and recycled C8 aromatics in which the paraxylene (and orthoxylene, if desired) concentrations are less than equilibrium. The mixed xylene feed combined with hydrogen-rich recycle gas is preheated and passed through the reactor, where EB is dealkylated to produce benzene and ethane, and xylene isomerization occurs to produce a paraxylene concentration in excess of 100% of equilibrium. Reactor effluent is cooled by heat exchange and the liquid products are separated from the recycle gas, stripped to remove light ends and fractionated to remove benzene and toluene. Bottoms from the fractionation section are then recycled to the paraxylene recovery section.
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