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

Abstract

The invention relates to a method for preparing para-xylene and coproducing low-carbon olefin from toluene and a methylated reagent. The method comprises: a granular catalyst is continuously added from the top of a reactor by moving bed reaction technology, and gradually moved down along with the reaction, continuously flows out from the bottom to a regenerator, and is regenerated; the raw materials, namely the toluene and the methylated reagent, enter a vaporizer for mixing and gasification, enter the reactor, pass through a catalyst bed from the bottom up (or top down), and are subjected to contact reaction with the catalyst; and gaseous mixture products after reaction flow out from the top (or bottom) of the reactor and are separated. The selectivity of the para-xylene in the products in a xylene isomer is more than 99 weight percent, and the selectivity of ethylene and propylene in low-carbon hydrocarbon between C1 and C5 is more than 90 weight percent. The moving bed catalyst has stable activity and can be continuously regenerated; the residence time of solid and fluid in the moving bed reactor can be adjusted; back mixing of materials is small; the conversion rate of the raw materials is improved; and abrasion of the catalyst is small.

Description

technical field [0001] The invention relates to a moving-bed reaction process for the co-production of light olefins by reacting toluene with methylating reagents to produce p-xylene with high selectivity. Specifically, it relates to a moving 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 is huge, and th...

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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 drawback of fixed-bed reaction catalyst coking and deactivation, but it is limited to the production of p-xylene, and the fluidized catalyst is easy to wear, and the catalyst consumption is relatively high. Big

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