【摘要】 在小型固定床反应器上研究了水蒸气钝化及过渡金属(Ni,Co,Cu,Zn)改性对调变纳米HZSM-5沸石催化剂上C5~C8混合烷烃芳构化反应的作用.采用NH3-TPD和Py-FT-IR方法表征了改性催化剂的表面酸性质,并与其催化芳构化性能进行了关联.结果表明,在450℃下进行水蒸气钝化能显著提高催化剂的芳构化选择性,减少甲烷和乙烷等低碳烷烃的生成;催化剂进一步用锌盐或铜盐溶液浸渍改性,可以显著提高催化剂的抗积炭失活能力.这是由于水蒸气钝化能适当减少沸石表面的酸量,降低酸强度,而铜、锌改性可进一步减少B酸中心,增加L酸中心,并与B酸中心协同作用形成具有脱氢活性的催化中心,从而影响混合烷烃的活化方式与芳构化路径.更多还原

【Abstract】 The effects of steaming and impregnation with transition metal (Ni, Co, Cu, Zn) salt solution on the catalytic performance of nano-sized HZSM-5 zeolite catalysts for the aromatization of C5-C8 alkane mixture were studied in a small fixed-bed reactor. The surface acidity of the modified zeolite catalysts was characterized by NH3-TPD and Py-FT-IR, and the surface acidity was correlated to the aromatization performance. The results showed that steaming treatment at 450 ℃ could notably increase the selectivity for aromatization over the zeolite catalysts, and less methane and ethane were produced. The impregnation of the steamed nano-sized HZSM-5 zeolite with copper or zinc nitrate solution significantly strengthened its resistance to coking deactivation. It was because that steaming treatment decreased both the amount and strength of acid sites on the zeolite surface, while the impregnation with copper or zinc nitrate solution further decreased Brnsted acid sites, increased Lewis acid sites, and generated active dehydrogenation sites by cooperating with Brnsted acid sites, thereby made an impact on both the activation way and the aromatization path of the alkane mixture.更多还原