|  | MTDP-3 (Toluene Disproportionation)
A Highly Selective and Stable Catalyst
A new ZSM-5 catalyst formulation is the heart of MTDP-3 process. It was designed to process toluene and limited amounts of C9 aromatics and can allow for inexpensive debottlenecks of existing TDP facilities. It also allows for production of more, high-value mixed xylenes and benzene. MTDP-3 services provide full support for licensees from initial consultation through technology transfer and on-going improvements.
- Potential cost advantage
- Two decades of experience
- Simple fixed bed process
- Retrofits into existing reactors
- High purity benzene co-product
| Potential Cost Advantage
MTDP-3 can debottleneck operations and lower costs of producing mixed xylenes. Its high space velocity and low H2/hydrocarbon mole ratio can permit increases in throughput without reactor and/or compressor replacement. And it reduces operating costs by requiring less hydrogen than competitor technologies.
Other Advantages include:
- Easy retrofit into existing equipment
- Easy operation
- Third generation catalyst: regenerable, long operating cycle
Since the introduction of MTDP-3 in 1996, four companies -- one in the U.S., one in Japan and two in Europe -- have licensed this leading-edge conventional toluene disproportionation technology for retrofit into toluene hydrodealkylation units. Typical MTDP-3 units are generally able to operate for more than 5 years before requiring regeneration.
Backed by Two Decades of TDP Experience
The first generation MTDP process was commercialized in 1975 in ExxonMobil Chemical's Naples, Italy plant. Four companies have licensed the MTDP-3 process. Three of the applications were conversions of toluene hydrodealkylation units. The fourth was a retrofit into an existing TDP unit. Two units, one in the U.S. and one in Japan, started up in 1996; the third and fourth, both in Europe, started up in 1997 and 2001.
| Simple Fixed Bed Process
Process flow is typical for a vapor phase reaction in a fixed bed reactor. Toluene feed along with a limited amount of C9 aromatics is combined with a hydrogen rich recycle gas. It is preheated and passed through a catalyst bed. Here disproportionation occurs at moderate temperature and pressure to produce equilibrium mixed xylenes and benzene. By-product yields are small.
The reactor effluent is cooled by heat exchange and the liquid products are separated from the recycle gas. The separated liquid is stripped to remove the light ends and then fractionated to recover the benzene product and the mixed xylenes. Unreacted toluene is recycled to extinction.
| Retrofits into Existing Reactors
MTDP-3, the state-of-the-art conventional toluene disproportionation process, incorporates ExxonMobil's expertise in ZSM-5 technology and is readily adaptable into existing radial-flow and conventional-flow reactors.
| High Purity Benzene Co-Product
Another advantage of the MTDP-3 process is that benzene co-product does not have to be extracted to meet commercial benzene specifications. The MTDP-3 benzene co-product purity exceeds 99.90 wt% via simple fractionation.
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