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XyMax (xylene isomerization)

ExxonMobil offers two highly selective xylene isomerization processes – XyMaxSM isomerization 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 existing equipment, where they can debottleneck operations, boost product yields, increase profits and provide more flexibility than competitive processes. XyMax and Advanced MHAI services provide full support for licensees from initial consultation through technology transfer and ongoing improvements.

With more than 35 years of commercial deployment, ExxonMobil xylene isomerization technologies have been licensed throughout the Americas, Europe, the Middle East and Asia. Approximately one-third of the world’s paraxylene capacity is produced using our technology.

Photo — With more than 35 years of commercial development, ExxonMobil xylene isomerization technologies have been licensed throughout the Americas, Europe, the Middle East and Asia.

XyMax (xylene isomerization) advantages

High ethylbenzene conversion with low xylene losses
Designed to meet specific plant needs, the XyMaxsm and Advanced MHAI isomerization processes can debottleneck operations by maximizing ethylbenzene (EB) conversion while minimizing xylene losses. For sites with lower reactor temperature limitations and those that use crystallization for paraxylene separation, the Advanced MHAI process offers optimum operation. For sites with higher reactor temperature capability and those that use adsorption-based paraxylene separation technology, the XyMax process is the right choice.

Both XyMax and Advanced MHAI can offer significant advantages over competing processes, such as:

  • higher throughput and paraxylene production
  • paraxylene approach to equilibrium of 100% or more throughout the operating cycle
  • lower operating costs - up to 25%
  • lower catalyst requirement
  • long operating cycles and optimal catalyst life

Advanced catalyst technology

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 as much as 30%.

Simple fixed-bed process

The process flow (shown) is typical for a vapor-phase reaction in a fixed-bed reactor. In 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.