Synthesis Of Hierarchically Porous Zeolite ZSM-5 And Investigation Of Its Catalytic Performance

Hierarchically porous ZSM-5 zeolite has the particular three-dimensional channels,high specific surface area,strong acidity and good shape-selective property.Meanwhile,it overcomes the intracrystalline diffusion limitation in the conventional microporous ZSM-5 zeolite.And the mesopores in the hierarchically porous zeolite may greatly improve the performance in catalytic reactions,especially in which large molecules are involved,due to the shortened diffusion distance.Hierarchically porous ZSM-5 zeolite has been widely used in the petrochemical industry.In this thesis,we firstly synthesized a series of microporous ZSM-5 zeolites using different methods.Then,a hierarchically porous zeolite ZSM-5(MZMS-5)was successfully and cost-effectively synthesized using the soft temple method,and employed as a support for preparation of high efficient Ni catalysts used in hydrodeoxygenation of phenol as model compound.And,the relationship of the catalytic performance with catalyst properties was investigated.Firstly,we synthesized a series of microporous ZSM-5 zeolite using less template or without template and researched the influence of different template on crystallinity,morphology and size of ZSM-5 zeolite.It is found that the ZSM-5 zeolite synthesized by adding no template is a coffin shape with low crystallinity and small particle size.Using TPAOH as template agent,synthesized ZSM-5 zeolite presents a flower shape formed by the accumulation of many 2-3 ?m cube particles,and its size is about 15-18 ?m.And the particle size of ZSM-5 zeolite synthesized by using n-butyl amine as template is about 18-25 ?m with a spherical shape.Besides,ZSM-5 zeolite could contain SiO2 mixed phase when the silica alumina ratio is too low,it will lead to poor crystallinity and even armorphous phase when the ratio is too high.Secondly,we got hierarchically porous ZSM-5 zeolites synthesized by low-cost waterglass as silicon sources,n-butylamine as template and cationic polymer quaternary ammonium salt(CCQA)as soft template.And we also explored the influence of synthetic conditions on the zeolite properties.Results show that with the increase of the dosage of the mesoporous template agent,the size of the mesoporous also increases.Comprehensive consideration of specific surface area,the hierarchically porous ZSM-5 achieves the best effect when the mesoporous template agent was 2.5 mL with a 398 m2/g specific surface area and 19 nm mesoporous size.With the increase of crystallization temperature,the synthesis induction period of hierarchically porous ZSM-5 zeolite is shorter and the crystal growth rate of zeolite is faster and consequently the crystallization time is shortened.Finally,a Ni catalyst supported on hierarchically porous ZSM-5 zeolite and a mixture of MZSM-5 and ?-Al2O3(Al-HMZSM-5)' was designed for hydrodeoxygenation of phenol as model compound.It was found that almost complete phenol conversion(99.6%)was achieved over the Ni/Al-HMZSM-5 catalyst along with a high cyclohexane selectivity(98.3%)under a mild condition(170 ?,4 MPa H2).In addition,the catalytic performances of Ni/HMZSM-5 is more active compared to conventional Ni/HZSM-5.