Synthesis of Sandwich-Structured Zeolite Molecular Sieves and Their Adsorption Performance for Volatile Hydrocarbons

To address the issue of volatile organic compound (VOC) emissions during crude oil storage and transportation, this study proposes a sandwich-structured zeolite molecular sieve (SMZ) fabricated via a pressing-sintering process integrating ZSM-5 powder and granules. The resulting monolithic zeolite exhibits enhanced mechanical strength and optimized pore architecture. Systematic investigations revealed that sintering at 600 °C with 10% carboxymethyl cellulose (CMC) yielded SMZ with a specific surface area of 349.51 m²/g and pore volume of 0.37 cm³/g. Its hierarchical pore system-micropores (0.495 nm) coupled with mesopores (2-10 nm)-significantly improved adsorption kinetics. Dynamic adsorption tests demonstrated superior performance: SMZ achieved saturation capacities of 127.6 mg/g for propane and 118.2 mg/g for n-butane in liquefied petroleum gas (LPG), with a breakthrough time of 41 min and a 106% increase in adsorption capacity compared to conventional monolithic zeolite (MZ) (90.2 mg/g vs. 43.8 mg/g). Regeneration studies confirmed that combined thermal desorption (250 °C) and nitrogen purging maintained > 95% capacity retention over five cycles, attributed to the high thermal stability of the MFI topology framework (≤600 °C) and crack-resistant ceramic-like interfaces. Additionally, SMZ exhibited exceptional hydrophobicity, with a selectivity coefficient of 20.9 for propane under 60% relative humidity. This work provides theoretical and technical foundations for developing efficient and durable adsorbents for industrial VOC mitigation.