Multistage nano-reactor catalyst for direct preparation of aromatic compounds from synthetic gas, and preparation method and application thereof

Abstract

The invention discloses a multistage nano-reactor catalyst for one-step direct preparation of aromatic hydrocarbons from synthetic gas, and a preparation method and an application thereof. The catalyst comprises a core layer iron-based Fischer-Tropsch catalyst, a porous oxide or porous carbon material transition layer and a molecular sieve shell layer having an aromatization function, wherein the shell layer molecular sieve can be further modified with a metal element or a nonmetal element, and the external surface of the molecular sieve is further modified with a silicon-oxygen compound to adjust the acidic site of the external surface and the aperture of the molecular sieve in order to inhibit the formation of heavy aromatic hydrocarbons. The preparation method of the multistage nano-reactor catalyst is characterized in that the transition shell layer can be prepared from the Fischer-Tropsch catalyst through multiple steps, the shell layer contains or does not contain an assistant, and the shell layer molecular sieve undergoes or does not undergo surface modification. The catalyst can be used for the direct preparation of the aromatic compounds, especially lightweight aromatic hydrocarbons, from the synthetic gas; the selectivity of the lightweight aromatic hydrocarbons in the hydrocarbons can reach 75% or more, and the content of the aromatic hydrocarbons aromatic hydrocarbons in a liquid phase product is not less than 95%; and the catalyst has a good stability and has a very good industrial application prospect.

Description

technical field [0001] The invention belongs to the technical field of synthesis gas conversion, and relates to a catalyst for directly producing aromatic compounds from synthesis gas through a Fischer-Tropsch synthesis route, as well as its preparation and application. Background technique [0002] Aromatic compounds including benzene, toluene and xylene (BTX) are important chemical basic raw materials, which are mainly derived from petroleum-based production processes, such as naphtha steam cracking for ethylene production and catalysis for gasoline and diesel production reforming or cracking. With the lightening of olefin raw materials, the reduction of crude oil resources and the increasingly prominent environmental problems, it is challenging and unsustainable to obtain aromatic compounds from petroleum routes. Therefore, more and more attention has been paid to the production of aromatics from non-petroleum routes. Based on my country's energy structure rich in coal ...

AI Technical Summary

Problems solved by technology

[0004] However, the use of direct composite catalysts for the direct production of aromatics from syngas still has certain limitations. For example, for intermediate products that are easy to undergo aromatization reactions, such as C2-C5, they still need to undergo several diffusions before entering the aromatization catalyst. At the same time, these intermediate products have the opportunity to escape; at the same time, after CO passes through the CO conversion catalyst, CO often cannot continue to activate and react on the second catalyst; in addition, the physical mixing method is easy to cause two The uneven distribution of active site concentration in the reaction system will affect the aromatization reaction of intermediate products to varying degrees

Due to the existence of these problems, the selectivity and yield of final aromatics are generally not high, especially light aromatics such as benzene, toluene and xylene

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