Hierarchically porous titanium silicalite molecular sieve coating, preparation method and application thereof

Abstract

The invention discloses a hierarchically porous titanium silicalite molecular sieve coating and a preparation method and application thereof, belonging to the technical field of catalytic materials. The preparation method for the hierarchically porous titanium silicalite molecular sieve coating comprises the following steps: with a titanium silicalite molecular sieve having a hierarchically porous structure as an active element, adding deionized water, preparing a coating slurry together with a binder and a plasticizer, coating the surface of a porous-structure carrier with the coating slurry, carrying out drying, then subjecting the carrier coated with a molecular sieve coating to crystal transformation treatment, converting the binder into a molecular sieve in the crystal transformation process, and meanwhile, allowing the coated titanium silicalite molecular sieve to undergo dissolving and recrystallizing to form a hierarchically porous titanium silicalite molecular sieve, thereby obtaining the hierarchically porous titanium silicalite molecular sieve coating. According to the preparation method disclosed by the invention, the binder in the coating is promoted to be dissolved, recrystallized and converted into the molecular sieve under high-temperature and high-pressure conditions by utilizing a mixed solution or steam of organic amine or inorganic alkali and organic amine, so chemical combination between pre-coated molecular sieve crystals and firm combination with the carrier are realized, and the hierarchically porous titanium silicalite molecular sieve coating is obtained.

Description

technical field [0001] The invention belongs to the technical field of catalytic materials, and in particular relates to a hierarchical porous titanium-silicon molecular sieve coating, a preparation method and an application thereof. Background technique [0002] Compared with conventional microporous molecular sieves, molecular sieves with hierarchical pore structure can reduce the diffusion resistance of macromolecules in the micropores of molecular sieves, improve the utilization rate of active sites of molecular sieves, and reduce the formation of coke substances, thus providing high utilization efficiency , extended catalytic life and improved catalytic performance of molecular sieve catalysts. So far, various methods such as nano-assembly, template method and post-treatment have been developed to synthesize molecular sieve catalysts with hierarchical pore structure. These synthetic strategies provide tunable hierarchical pore molecular sieve characteristics, for examp...

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Problems solved by technology

The above process brings a series of problems: 1. The addition of binder will cover the active site and block the secondary channels and micropores of the molecular sieve; 2. The diffusion distance of the molecular sieve catalyst will increase after molding, which will bring significant The internal diffusion of the shaped particle catalyst leads to low catalyst utilization, poor product selectivity, and the catalyst is easy to coke and deactivate

Third, the low thermal conductivity of molecular sieves leads to uneven distribution of the temperature field of the catalyst bed, resulting in localized hot spots, resulting in catalyst sintering deactivation (especially for metal-supported catalysts)

However, it was recently found that although structured catalysts can optimize flow field distribution, reduce bed pressure drop and eliminate external diffusion, the internal mass transfer of molecular sieve coatings is still limited by internal diffusion, and the effective utilization of this catalyst is high

Molecular sieve coatings need to be further improved. Preparation of molecular sieve coatings with graded pore molecular sieves as active units is an effective means to enhance mass transfer in coatings. However, the current preparation method of graded pore molecular sieves is limited to the preparation of molecular sieve powders. Molecular sieve coatings based on porous molecular sieves are still a challenging subject

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