Liquid phase xylenes isomerization (LPI)  

The LPI process is the latest generation of liquid phase isomerization technology and is available for license by ExxonMobil directly, as well as by Axens as part of the ParamaX® technology suite for grassroots aromatics complexes.

LPI process: Significant energy savings, ultra-low xylenes losses, inexpensive debottlenecking

The LPI process is the latest addition to ExxonMobil’s portfolio of xylenes isomerization processes available for license. The technology operates at low temperature with xylene losses less than the best performing vapor phase isomerization technology, the XyMax^SM-2 process. The LPI process can be deployed in parallel with vapor phase isomerization units in existing plants, yielding both energy savings and debottlenecking opportunities. Because of its very low EB conversion per pass, the LPI process is often operated in combination with a vapor phase isomerization process, where most EB removal is achieved. However, in situations where the C₈ aromatics stream to be isomerized contains very low EB, xylenes isomerization can be carried out via the LPI process only, and EB purge is managed by other means.

The following simplified flowscheme shows the LPI process in a typical fractionation and recovery section of an aromatics complex.

• Significant energy savings
 - Low temperature operation
 - Elimination of two costly steps - (1) raffinate vaporization and (2) isomerate condensing
 - Reduced traffic through the high temperature vapor phase isomerization unit

• Ultra-low xylene losses
• Low catalyst costs
• Low metallurgy costs
• Debottlenecking opportunity for existing plants or significant reduction of the vapor phase isomerization unit size in grassroots facilities
• High paraxylene selectivity
• Long cycles consistent with modern aromatics complexes turnaround schedule

• Initial discussions to confirm client objectives and tailor the solution
• Detailed yield estimate
• Feasibility study
• Commercial proposal
• Process design package
• Technology transfer, training, catalyst loading and start-up support
• Technology improvement
• Performance monitoring and technical assistance throughout the life of the catalyst