The effect of the acidity of HZSM-5/MCM-41 hierarchical zeolite on its catalytic performance in the supercritical catalytic cracking of n-dodecane was investigated by controlled ion exchange with NaCl solution under ultrasonic conditions. XRD and nitrogen adsorption–desorption results showed that the crystal and porous properties were not affected, while NH₃-TPD, the probe reaction of n-hexane cracking and temperature-programmed surface reaction (TPSR) of n-dodecane demonstrated that strong Brønsted acid sites were replaced by Na⁺ (weak Lewis acid sites) to different extents with varying concentrations of NaCl solution. Although the initial conversion of n-dodecane during the supercritical catalytic cracking was slightly reduced, its stability was greatly enhanced by ion exchange. An ultrastable catalyst with no obvious deactivation within 3 h of time on stream (TOS) was obtained by ion exchange with 0.8 M NaCl solution. A mechanism describing the role of the acid sites residing in both micropores and mesopores of the hierarchical catalyst was proposed based on coke analysis.

中文翻译：

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HZSM-5 / MCM-41分级沸石的酸度对其在正十二烷超临界催化裂化中催化性能的影响：实验和机理†

通过在超声条件下与NaCl溶液进行离子交换控制，研究了HZSM-5 / MCM-41分级沸石的酸度对其在正十二烷超临界催化裂化中催化性能的影响。XRD和氮吸附-解吸结果表明，晶体和多孔性能没有影响，而NH ₃ -TPD，的探针反应Ñ的己烷裂化和程序升温表面反应（TPSR）ñ -dodecane表明，强布朗斯台德酸用不同浓度的NaCl溶液以不同程度用Na ⁺（弱路易斯酸位点）取代这些位点。虽然n的初始转换超临界催化裂化过程中的十二碳烷略有减少，通过离子交换大大提高了其稳定性。通过与0.8 M NaCl溶液进行离子交换，获得了在运行3小时内没有明显失活的超稳定催化剂（TOS）。基于焦炭分析，提出了描述酸性位点同时存在于分级催化剂的微孔和中孔中的作用的机理。