2024 AIChE Annual Meeting

(73g) Advanced Catalytic Process for Monetizing Heavy Aromatics Stream in Aromatics Complex to Increase Paraxylene Production

Authors

Xu, Q. - Presenter, Saudi Aramco
Alabdullah, M., Saudi Aramco
Hodgkins, R., Research and Development Center
A sustained growth in demand for petrochemicals has provided impetus to the on-going energy transition to alleviate the forecast erosion of gasoline value in the refining industry. Benzene and paraxylenes are among the valuable petrochemical products produced in a refinery aromatics recovery complex which typically also produces a reject heavy aromatics stream containing alkyl-bridged non-condensed multi-aromatics. The use of this heavy aromatics reject stream is limited to gasoline blending due to its composition, density, dark color, and high boiling point. In this context, Saudi Aramco has developed an advanced hydro-dearylation process, so called BTX-MaxTM process, to upgrade this low-value reject stream over a zeolite-containing hydrocracking catalyst to significantly enhance high value mono-aromatics content.

The technological advantages of the BTX-MaxTM process are multiple-fold: (1) dealkylate the di-aromatics into mono-aromatics; (2) lower the density of the stream; (3) improve the dark color to a much lighter one; (4) lower the average boiling point of the stream; and (5) process at relatively mild reactor conditions. Experiments have been carried out in a pilot plant testing unit with 72 grams catalyst under temperatures ranging from 200 °C to 400 °C and 15 bar pressure. Two-dimensional gas chromatography (2D-GC) data of the heavy aromatics reject stream and the product stream have been obtained to facilitate the hydrocarbon analysis. Simulation of the reactor effluent has been carried out to quantify the compositions and physical properties for the light aromatics and the unconverted heavy aromatics stream. Results have shown that the optimum temperature for the conversion of the multi-aromatics into mono-aromatics achieves is around 350 °C and the process yields a 21% increase in mono-aromatics. Results further confirm that mono-aromatic formation comes at the expense of biphenyl/di-aromatics conversion, with a 75% decrease observed. In addition to the technological advantages, the BTX-MaxTM requires very few conventional equipment without hydrogen recycling, leading to very low CAPEX and OPEX.

In conclusion, a novel catalytic process, BTX-MaxTM, has been developed to monetize the low-value heavy aromatics reject stream in a refinery aromatics recovery complex. This process, under relatively mild conditions in the presence of a zeolitic catalyst and hydrogen, targets the alkyl bridge of the non-condensed alkyl-bridged multi-aromatics to form high-value mono-aromatics. The operation can recycle the mono-aromatics product stream back to the aromatics recovery complex to increase the production of benzene and para-xylene, and in so doing, capture the value created by this novel process.