2020 REFINING PROCESSES HANDBOOK PROCESS CATEGORIES COMPANY INDEX AROMATICS PxMaxSM Application: Selective conversion of toluene to high-purity (90%+) paraxylene-rich (PX) xylenes and benzene. Description: Dry toluene feed and hydrogen-rich recycle gas are pumped through feed/effluent exchangers and the charge heater and into the reactor (1). Selective toluene disproportionation (STDP) occurs in the vapor phase to produce the PX-rich xylene and benzene co-product. Byproduct yields are small. Reactor effluent is cooled by heat exchange and liquid products are separated from the recycle gas. Hydrogenrich gas from the separator (2) is recycled back to the reactor together with makeup hydrogen. Liquid product is stripped of remaining light gas in the stabilizer (3) and sent to product fractionation. Unconverted toluene is recycled to extinction. The PxMax technology uses catalyst, which is permanently selectivated by ex-situ pretreatment during catalyst manufacture. PxMax technology provides significantly higher selectivity and longer operating cycles than other STDP technologies. Operating costs associated with downstream recovery are also reduced by the high paraxylene purity from the process. Recycle toluene C5- 99.9+% benzene H2 Stabilizer Toluene PxMAX process Benzene column Paraxylene Paraxylene-enriched xylenes Paraxylene recovery Toluene column Xylene column Paraxylene-depleted mixed xylenes C9+ aromatics Products: Paraxylene and benzene Advantages: The PxMax process operates at lower start-of cycle temperature and lower hydrogen to hydrocarbon recycle ratios than other STDP technologies, resulting in longer cycles and lower utilities. By eliminating the in-situ selectivation step, the PxMax technology results in simplified operation and lower capital costs. The catalyst offers long operating cycles and is regenerable. Development/delivery: The first two units running the PxMax process started up in 1996 and 1997 at Chalmette Refining's Louisiana refinery and Mobil Chemical's Beaumont, Texas, plant, respectively. ExxonMobil has led the development and application of technologies for xylenes and benzene production since the discovery of ZSM-5 in the late 1960s. As part of our license, we provide full support from initial consultation through technology transfer and ongoing improvements to ensure operators achieve full value. Installations: There are two MSTDP units (predecessor technology to PxMax) and 12 PxMax units in operation. Licensor: ExxonMobil Catalysts and Licensing LLC or Axens. Website: www.catalysts-licensing.com Contact: https://www.exxonmobilchemical.com/en/resources/contact-us Copyright © 2020 Gulf Energy Information. All rights reserved.http://www.hydrocarbonprocessing.com/ http://www.catalysts-licensing.com https://www.exxonmobilchemical.com/en/resources/contact-us