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    丙酮热催化常用分子筛缩合路径与积碳行为研究

    Study on condensation pathways and coking behavior of acetone over conventional zeolites in thermal catalysis

    • 摘要: 本研究针对催化领域常用的4种分子筛材料(NaY,NaZSM-5,NaMCM-22和S-1),结合丙酮热催化的实际需求,从酸性质及程序升温过程中间产物演变等角度展开理论研究,系统考察了其结构特性、催化性能、中间产物生成规律及积碳行为。实验结果表明,丙酮在纯分子筛上的催化转化主要依赖于其固有酸性,但该酸性也易促使丙酮转化为难降解中间产物,进而引发积碳。NaY、NaMCM-22和NaZSM-5因其酸性结构及Na+离子的修饰作用,生成了乙酸酐、异佛尔酮和异亚丙基丙酮等缩合副产物。当温度升至360 ℃时,丙酮及其副产物可逐步降解为乙酸、甲酸,最终以水和CO2形式脱附。相比之下,S-1分子筛骨架以Si─O─Si结构为主且无酸性位点,在程序升温过程中几乎无法催化降解丙酮,除极少量丙酮脱附外,未检测到任何缩合或裂解产物。在3种含钠分子筛中,NaMCM-22生成的缩合副产物最多,丙酮降解效率最低;NaZSM-5对丙酮的矿化效率最高,NaY次之。最后,本研究详细列出了各材料上丙酮的降解与缩合路径,为分子筛材料热催化降解丙酮提供新的理论依据。

       

      Abstract: This work conducted a theoretical study on four commonly used zeolite materials (NaY, NaZSM-5, NaMCM-22, and S-1), combining the practical requirements of acetone thermal catalysis. The structural characteristics, catalytic performance, evolution of intermediate products during temperature-programmed processes were evaluated, and coke behavior from the perspectives of acid properties and intermediate product evolution were investigated. Experimental results showed that the catalytic conversion of acetone on pure zeolites primarily depends on their inherent acidity. However, the acidity also promoted the transformation of acetone into refractory intermediates, subsequently triggering coke formation. Due to their acidic structures and modification by Na+ ions, NaY, NaMCM-22, and NaZSM-5 generated condensation by-products such as acetic anhydride, isophorone, and mesityl oxide. As the temperature increased to 360℃, acetone and its by-products could be progressively degraded into acetic acid and formic acid, ultimately desorbing as H2O and CO2. In contrast, the S-1 zeolite framework consists mainly of Si─O─Si structures and lacks acidic sites. It showed no catalytic activity for acetone degradation during the temperature-programmed process. Aparting from the desorption of trace amounts of acetone, no condensation or cracking products were detected. Among the three sodium-containing zeolites, NaMCM-22 generated the most condensation by-products and exhibited the lowest acetone degradation efficiency. NaZSM-5 achieved the highest mineralization efficiency for acetone, followed by NaY. This study details the degradation and condensation pathways of acetone on each material, providing new theoretical insights for improving the thermal catalytic degradation of acetone using zeolite materials.

       

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