Porous silicon-carbide carrier surface gradient pore molecular sieve coating and preparation method thereof

Abstract

The invention belongs to the field of catalysts and an application of the catalysts, and in particular relates to a porous silicon-carbide carrier surface gradient pore molecular sieve coating and a preparation method thereof. The porous silicon-carbide carrier surface gradient pore molecular sieve coating has the intercrystal porosity with continuous gradient change, the porosity among molecular sieve crystals in an inner molecular sieve coating is low, and the porosity among molecular sieve crystals in an outer molecular sieve coating is high. The coating is realized through two-step coating combined with steam treatment: a colloidal state molecular sieve precursor is coated on the surface of a foamed silicon-carbide carrier; a mixer of the colloidal state molecular sieve precursor, the molecular sieve crystals and a pore forming agent is coated; and finally, the molecular sieve precursor is converted into the molecular sieve crystals through steam treatment so as to realize the firm bonding between the coating and the carrier. The proportion of the colloidal state molecular sieve precursor to the molecular sieve crystals is controlled, the pore forming agent is added, and the intercrystal porosity of the coating can be regulated. The gradient coating and the carrier are firmly bonded, and the coating is high in mass transfer capacity and suitable for large-scale preparation.

Description

technical field [0001] The invention belongs to the field of catalysts and applications thereof, in particular to a gradient pore molecular sieve coating on the surface of a porous silicon carbide carrier and a preparation method thereof. Background technique [0002] Zeolite crystals have unique structures and properties, and have been widely used as catalysts, catalyst supports or adsorbents in petrochemical, environmental protection and other fields. Traditional zeolite crystal catalysts are applied in the fixed bed in the form of particles, which not only leads to a waste of energy due to the increase of bed pressure drop, but also produces a large concentration and temperature gradient in the production process, which reduces the catalytic performance of the catalyst. efficiency. At the same time, the separation and recovery of zeolite crystal catalysts are difficult, resulting in catalyst loss and environmental pollution. [0003] Loading molecular sieves on the surf...

AI Technical Summary

Problems solved by technology

In this way, the diffusion of reactants and reaction products in the zeolite crystal and zeolite coating is limited. As a result, only the inner surface of the zeolite near the outside of the catalyst particle is used, while the inner surface of the micropore center and inside cannot be used. , which reduces the utilization of the catalyst

The reaction product cannot be separated from the zeolite crystal in time, which increases the probability of secondary reactions and reduces the selectivity to the target product

At the same time, due to the large zeolite crystal size or thick zeolite coating, the heat transfer between the zeolite coating and the carrier is limited, which easily causes local overheating in the zeolite coating and deactivates the catalyst.

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