Adsorption of VOCs by Molecular Sieves in Shipboard Operations: Water Competition Effect and Pore Size Matching Mechanism
Ship loading operations emit multi-component volatile organic compounds (VOCs) with complex composition, including methanol, dichloromethane, trichloroethylene, p-xylene, acrylonitrile, benzene, and acetonitrile. Under high-humidity marine conditions, treatment is challenging. This study systematically screened three molecular sieves with distinct pore sizes—ZSM-5, β-type, and HY—for selective adsorption of these seven VOCs at moisture contents of 0%, 2.5%, and 5%. Competitive adsorption in acrylonitrile/p-xylene mixtures was examined on ZSM-5-all-silica and HY-100. Results showed: (1) saturated adsorption capacity decreased with increasing moisture content, confirming water-VOC competition; higher Si/Al ratios enhanced hydrophobicity, with all-silica ZSM-5 exhibiting superior water resistance. (2) Selective adsorption followed pore size matching: ZSM-5 (0.54–0.56 nm) suited C1–C3 small molecules (10–50 mg/g); β-type (1.1–1.2 nm) showed best universality for C3–C6; HY (2.16–2.76 nm) favored C8 molecules like p-xylene (100–120 mg/g). (3) Optimizing molecular sieve proportion and layered arrangement balanced adsorption capacities across components, significantly prolonging breakthrough time. The optimal configuration placed ZSM-5 in the upper layer and HY in the lower layer. Molecular sieves also exhibited good thermal stability and regenerability. This study provides technical support for efficient treatment of multi-component VOCs from ship loading operations.