Method for preparing p-xylene and co-producing light olefins by toluene and methylating reagent

Abstract

The invention relates to a fluidized bed reaction method for preparing para-xylene and coproducing low-carbon olefin with high selectivity by reacting toluene and a methylated reagent. The method adopts fluidized bed reaction technology and uses a catalyst to highly selectively produce the para-xylene and simultaneously highly selectively coproduce ethylene and propylene. The method is characterized in that the raw materials, namely the toluene and the methylated reagent enter a vaporizer for mixing and gasification, pass through a distribution plate, enter a fluidized bed reactor, and are taken as a fluidizing medium and subjected to catalysis with a fluidized catalyst; and gaseous mixture products after reaction are exhausted from the top of a tower and separated. The selectivity of the para-xylene in products in a xylene isomer is more than 99 weight percent, and the selectivity of the ethylene and the propylene in low-carbon hydrocarbon between C1 and C5 is more than 90 weight percent. The carbon deposit catalyst in the reactor continuously enters a regenerator for regeneration and activation and enters the reactor for recycling, can be continuously regenerated and has stable activity; and the method has simple technological flow and is easy to realize large-scale industrialization.

Description

technical field [0001] The invention relates to a fluidized-bed reaction process method for the high-selectivity preparation of p-xylene and co-production of light olefins by reacting toluene and a methylating reagent. Specifically, it relates to a fluidized bed reaction process, using a catalyst to produce p-xylene with high selectivity and co-produce ethylene and propylene with high selectivity in a reaction system. Background technique [0002] Paraxylene and ethylene are two basic raw materials for the synthesis of polyester (PET). At present, p-xylene production mainly uses toluene, C 9 Aromatic hydrocarbons and mixed xylenes are used as raw materials, and are produced through disproportionation, isomerization, adsorption separation or cryogenic separation. Since the p-xylene content in its products is thermodynamically controlled, p-xylene is at C 8 Mixed aromatics only account for about 20%. In the process, the amount of material circulation is large, the equipment...

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Problems solved by technology

[0004] The above-mentioned patents respectively disclose new ways to prepare p-xylene and low-carbon olefins. Since the two reaction processes are acid-catalyzed reactions, both require shape-selective catalysis, so modified ZSM-5 molecular sieves are used as catalysts for activity. components, but due to the different target products, the characteristics of the catalysts of the two processes are very different.

Any kind of catalyst cannot satisfy the process of producing p-xylene with high selectivity and producing light olefins with high selectivity at the same time

[0005] On the other hand, the above-mentioned toluene-methanol alkylation to p-xylene and methanol-to-low-carbon olefins reactions using ZSM-5 molecular sieves as catalysts both use fixed-bed reactions. The catalysts are deactivated due to reaction carbon deposition, so fixed-bed reactions must Frequent switching regeneration, complex operation

USP 5,939,597 discloses a fluidized bed reaction process for producing p-xylene, which overcomes the drawbacks of fixed-bed reaction catalyst coking and deactivation, but it is limited to the production of p-xylene

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