ZSM-5分子筛碳氢燃料裂解催化剂抗积炭的研究进展

Research progress of ZSM-5 zeolite for hydrocarbon fuel catalytic cracking against carbon deposition

传统的ZSM-5分子筛仅具有单一的微孔结构以及较长的扩散路径,使其在催化碳氢化合物过程中非常容易产生积炭,进而会堵塞分子筛孔道或覆盖孔道内的酸性位点,致使分子筛失活,降低催化反应效率。本文对积炭的形成机理、影响积炭形成的因素以及ZSM-5分子筛失活机理进行了简要分析。对多级孔道分子筛的合成、中空分子筛的合成、复合分子筛的合成、分子筛的酸处理、纳米级分子筛的合成、纳米片型MFI分子筛的合成以及分子筛改性等常用的抑制ZSM-5分子筛积炭的方法进行总结,并对各种方法的优势和缺陷进行了对比和分析。着重对纳米分子筛的合成以及纳米片型MFI分子筛的合成两种抑制积炭形成的方法进行讨论。最后针对降低积炭的研究方向进行了展望:如何高效、低廉地合成出具有优良抗积炭性能的纳米或纳米片型分子筛是研究的重点,并在此基础上对其改性,以进一步降低积炭的产生。

Carbon deposition is easily generated on conventional ZSM-5 zeolite during the catalytic reactions due to its single microporous structure and long diffusion length.The carbon deposition can block the pore or cover the acid sites,resulting in deactivation of the zeolites and decrease of the reaction efficiency.This review has analyzed the formation mechanism of carbon deposition,the influence factors on carbon generation and the deactivation mechanism of ZSM-5 zeolites.Then,common methods against carbon deposition of ZSM-5 zeolite are summarized from the aspects of synthesis of hierarchical zeolite,hollow zeolite and complex zeolite,acid treatment of zeolite,synthesis of nano ZSM-5 zeolite and nanosheet MFI zeolites.The advantages and disadvantages of these methods are also compared and analyzed.Synthesis of nano ZSM-5 zeolite and nanosheet MFI zeolites are chosen particularly to discuss the effect on their anti-carbon deposition.Finally,some promising research directions on reducing the carbon deposition are prospected.Developing effective and cheap methods to prepare nano ZSM-5 zeolite or nanosheet MFI zeolites to decrease the amount of carbon deposition is still highly demanded.Besides,modification of these zeolites could decrease the amount of carbon deposition further.