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以HZSM-5沸石分子筛为载体,尿素为沉淀剂,采用常压沉积-沉淀法和负压沉积-沉淀法制备了系列Au/HZSM-5沸石催化剂并采用常规催化剂表征方法对其进行了表征.用脉冲微反装置评价了纯正丁烷(99.9%)在氢型和金改性的纳米HZSM-5催化剂上的反应活性和烯烃选择性.结果表明,在550℃下,负压沉积-沉淀法制备的不同金负载量的纳米HZSM-5催化剂上的转化率和烯烃选择性都远高于常压沉积沉淀法制备的催化剂.改性量为2.0%的Au/HZSM-5-A(负压)催化剂正丁烷转化率达到了58.0%、烯烃选择性为57.2%.脱氢和脱甲基活化是正丁烷的重要活化方式,也是影响其烯烃选择性的主要因素.金改性在提高正丁烷转化率的同时,也促进了正丁烷的脱氢和脱甲基活化.纳米HZSM-5因晶粒度小,孔道短和微孔扩散阻力低而有利于正丁烷转化.负压有利于清除HZSM-5内部的无定型杂质和脱气净化处理,有利于金的负载量和分散度.
A series of Au / HZSM-5 zeolite catalysts were prepared by atmospheric pressure deposition-precipitation method and vacuum deposition-precipitation method using HZSM-5 zeolite as carrier and urea as precipitating agent. The catalysts were characterized by conventional catalyst characterization. The reactivity and olefin selectivity of pure n-butane (99.9%) on hydrogen-modified and gold-modified nano-HZSM-5 catalysts were evaluated by means of pulsed micro-reactor. The results show that at 550 ℃, negative pressure deposition- The conversion and olefin selectivity of the nano-sized HZSM-5 catalysts with different gold loadings were much higher than that of the catalysts prepared by the atmospheric deposition deposition method. The modified Au / HZSM-5-A with 2.0% ) Conversion of n-butane reached 58.0% and olefin selectivity was 57.2% .Dehydrogenation and demethylation were the main activation ways of n-butane and the main factors influencing their olefin selectivity. Butane conversion, but also promote the dehydrogenation and demethylation of n-butane.HZSM-5 nanomaterial is conducive to n-butane conversion due to its small grain size, short pore size and low micropore diffusion resistance. Help to clear the HZSM-5 internal amorphous impurities and degassing purification, is conducive to gold Load and dispersion.