Molecular sieve manufacturer explains the optimization of transfer performance in molecular sieve crystals
The limitations of restricted entry, chronic transmission, and diffusion energy barriers result in inefficient catalyst utilization. In many cases, molecular sieves are victimized and apoptotic. When size selectivity becomes the key to the process, it is generally preferred to choose large molecular sieve crystals in order to reduce the contribution of external surface reactions. The methylation process of toluene on ZSM-5 molecular sieve is a clear example, which can improve the overall selectivity of the process under severe diffusion restrictions. This fact poses accessibility challenges for industrial devices at the limit and limit levels, to the extent that they operate far below saturation production capacity, although they are also used to improve process selectivity.
The classical method of testing efficiency factors in porous media may not be accurate when applied to molecular sieves. However, from a qualitative perspective, their application will be beneficial for understanding the performance and limitations of molecular sieve catalytic reactions, and thus for selecting molecular sieve types with less diffusion restriction obstacles in design. If a small Teal modulus is required, two different strategies need to be followed: reducing the diffusion length L in the pores of the molecular sieve and/or increasing the effective diffusion coefficient Deff. The second strategy led to the development of ordered mesoporous materials, where diffusion is controlled by Knudsen or ontology modes. This method is effective when the bulk molecules exceed the pore and cage sizes in the molecular sieve, or when size selectivity is not a priority. However, mesoporous materials have poor thermal stability due to their thin walls. More importantly, the performance of their active centers is usually much lower than that of molecular sieves because of the amorphous characteristics of their wall surfaces.
In sync with the development of mesoporous materials, researchers have made great efforts to improve the diffusion performance of molecular sieves while maintaining other intrinsic properties of the materials. The most commonly used methods include: synthesizing new structures through macropores and macropores; Create mesopores through synthesis or post synthesis methods to modify the structural characteristics of known frameworks; Small molecular sieve crystals with appropriate inner to outer surface ratio; Synthesis of micro mesoporous composite materials using a mixed template system or a re structured product method; Layered crystal structure delamination.
The evolution of molecular sieve materials for improving transmission is an important research field, and some principles have been confirmed. Molecular sieve is a material that can be further developed and utilized. A detailed analysis of the characteristic time of various phenomena related to diffusion in catalyst particles (reactions, diffusion in molecular sieves, micropores, mesopores, and macropores, transfer energy barriers) will guide the optimization of layered structure composition of catalyst particles in practical applications. This means combining molecular modeling with careful experimentation and interpretation of all these aspects, including diffusion. Hunan Providence New Materials Co., Ltd is a professional molecular sieve manufacturer
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