Selective toluene disproportionation (PxMax℠)
ExxonMobil’s PxMax℠ process is the industry benchmark Selective Toluene Disproportionation (STDP) process. The technology, based on the ex-situ selectivated EM-2300 catalyst, offers unmatched paraxylene selectivity and product yields, as well as exceptionally long and stable cycles. The PxMax℠ process is also licensed by our alliance partner, Axens, as part of the ParamaX® technology suite for grassroots aromatics complexes. ExxonMobil’s Dividing-Wall Column (DWC) technology is also available for licensing in combination with the PxMax℠ process.
Key benefits
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- Ultra-high PX selectivity
- Higher total xylene yields
- Superior xylenes/benzene ratio
- Benzene product with greater than 99.9% purity
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- No in-situ regeneration need (cycles > 15 years)
- Performance improves over the catalyst cycle
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- Reduced size of reactor and PX recovery unit
- Lower metallurgy cost
- Lower operating costs
Ultra-high paraxylene selectivity, superior yields, extremely long catalyst cycles
The EM-2300 catalyst is at the heart of the unique performance and superior yields of the PxMax℠ process. The catalyst is manufactured using a proprietary ex-situ selectivation technique which increases the relative diffusivity rate of paraxylene versus those of the larger isomers. As a result, the PxMax℠ process yields ultra-high paraxylene selectivity at SOC (> 96%). Paraxylene selectivity further increases as the cycle progresses making the PxMax℠ process by far the most paraxylene selective STDP process on the market.
Life cycle support
- 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 startup support
- Technology improvement
- Performance monitoring and technical assistance throughout the life of the catalyst
Compared with traditional STDP processes requiring in-situ coke selectivation, the PxMax process offers the following advantages:
- Ultra-high paraxylene selectivity (>96%) which increases throughout the cycle
- Higher total xylenes yield
- Superior xylenes/benzene ratio
- Benzene product with greater than 99.9% purity
- Very stable catalyst yielding extremely long cycles (more than 15 years)
- No in-situ selectivation requirement, resulting in:
- - Simplified operation (no lost time for selectivation)
- - Easier retrofit into existing equipment
- - Lower metallurgy investment cost and operating cost
- High weight hourly space velocity (WHSV)
- Very low H₂ consumption
- Reduced size for associated paraxylene separation unit resulting in lower investment and operating costs due to the very high paraxylene content in the C₈ aromatic product
PxMax flowscheme
Featured resources
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A Particle of Difference
How ExxonMobil Catalysts and Technology Licensing solves shared challenges through expertise, specialty catalysts, technology licensing and collaboration.
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ExxonMobil Catalysts and Technology Licensing – summary of technologies offered
Learn about the cutting-edge, proprietary catalysts and advantaged process technologies that ExxonMobil provides for refining, gas and chemical needs.