Synthesis Of ZSM-5/KIT-6 Micro-Mesoporous Materials And Their Catalytic Performance For The Cracking Of N-heptane

Naphtha catalytic cracking,as a potential alternative process for steam cracking,has many advantages such as high value-added product selectivity,mild operating conditions and adjustable product distribution.Alkanes such as C5-C7,an important component of naphtha,are difficult to achieve the desired results under mild conditions of cracking operation.Therefore,it has become a difficult problem to restrict the development of naphtha catalytic cracking.In this study,several multi-stage porous composite catalysts were designed and applied to the catalytic cracking of n-heptane,taking n-heptane as a model compound.In this thesis work,we started with the following aspects: preparation of carriers,doping modification of Fe and Cr active components to design and prepare new and efficient catalysts.The support materials,catalysts and their physicochemical properties were characterized and analyzed by means of XRD,BET,UV-Vis DRS,SEM and TEM.The catalytic performance for the cracking of n-heptane,a model compound,over composite ZK zeolite materials and Fe and Cr-doped zeolite catalysts was evaluatedIn this thesis work,a novel composite mesoporous molecular sieve material was firstly prepared.After determining the preparation process of ZSM-5 molecular sieve,the composite ZK molecular sieve material with ZSM-5 and KIT-6 skeleton structure was successfully synthesized by using ZSM-5 microcrystalline emulsion precursor as raw material and P123 as template,and it was confirmed that when the amount of ZSM-5 microcrystalline emulsion was 10%,the composite ZK molecular sieve carrier had the best catalytic performance.The effect of ZK zeolites doped with Fe and Cr active components on the catalytic performance for the cracking of n-heptane was investigated.The doping ratio of active component Fe and Cr was determined,.When the doping mass percentage of active component Fe was 0.75%,and the doping content of active component Cr was 0.4%,the catalytic cracking activity of the catalyst was the highest,and the conversion rate reached 99.9% at 625?.