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Benzene, a critical organic compound in petrochemical and chemical industries, requires efficient separation and purification due to its high volatility and potential environmental impact. Adsorption, as a cost-effective and energy-saving method, relies on adsorbents with tailored structures to selectively capture benzene molecules. Among various adsorbents, 13X molecular sieves, with their uniform pore structure and excellent ion-exchange capacity, have emerged as promising candidates for benzene adsorption applications. 13X molecular sieves, characterized by a framework structure of 4 A-type zeolite with a nominal pore size of 10 A (0.1 nm) and a high Si/Al ratio, exhibit unique adsorption properties. The large pore diameter and well-defined channels allow for selective inclusion of molecules with kinetic diameters less than 10 A, making benzene (kinetic diameter ~5.9 A) a suitable target for adsorption. Additionally, the cation-exchange sites in 13X (typically Na+ ions) enhance adsorption affinity by forming dipole interactions with benzene, improving both capacity and selectivity. The adsorption performance of 13X molecular sieve for benzene is influenced by several key factors. Temperature plays a dual role: lower temperatures favor physical adsorption, increasing benzene uptake, but excessively low temperatures may reduce mass transfer rates. Pressure also impacts adsorption, with higher pressures generally promoting more benzene molecules to be adsorbed onto the sieve surface. The initial concentration of benzene in the feed mixture affects the adsorption capacity; at low concentrations, monolayer adsorption dominates, while at high concentrations, multilayer adsorption occurs, reaching saturation. Coexisting components, such as water vapor or other hydrocarbons, can compete for active sites, necessitating pre-purification steps in industrial applications. Numerous studies have demonstrated the superior performance of 13X molecular sieve in benzene adsorption. For instance, in fixed-bed adsorption columns, 13X packing achieves high benzene removal efficiency (>99%) from model mixtures, with a breakthrough capacity of 15-20 mg/g, outperforming traditional activated carbon in terms of selectivity and regeneration stability. The regenerability of 13X is another key advantage; by heating the saturated adsorbent to 100-150 °C, benzene can be desorbed, allowing repeated use for multiple cycles without significant loss of adsorption capacity. In industrial settings, 13X molecular sieve is widely used in benzene separation processes. It is employed in solvent recovery systems to capture benzene from exhaust gases in chemical plants, reducing environmental pollution and recovering valuable resources. In the petrochemical industry, 13X-based tower internals, such as structured packing or packed beds, are integrated into distillation or absorption towers to enhance benzene purification, improving product quality and reducing energy consumption compared to conventional separation methods. Looking ahead, ongoing research focuses on modifying 13X molecular sieves (e.g., through doping with metal ions or adjusting pore size) to further enhance benzene adsorption capacity and selectivity. These advancements will expand the applications of 13X molecular sieve in environmental protection, energy conservation, and sustainable chemical production.
