Study On Synthesis Of ZSM-5 Zeolite With Low-cost By Green Mehods

ZSM-5 molecular sieves are widely used in petrochemical,environmental protection,fine chemical and many other fields due to their unique pore structure and excellent performance.Taking into account the country's strict requirements for environmental protection,practical production convenience,economic benefits and other factors,in this dissertation we propose a green,low-cost method for synthesizing ZSM-5molecular sieve.1.Generally speaking,template is needed to be added to synthetic molecular sieve,but template is like a double-edged sword,which can bring some negative effects while assisting molecular sieve synthesis.Therefore,it is necessary to study the preparation of ZSM-5 zeolite under the condition without a template due to the narrow phase of synthesis and the difficulty in industrialization.Therefore,the synthesis of ZSM-5 without template should be systematically studied to provide a feasible data basis for industrial production.In this paper,the influence of two kinds of silica gel on the synthesis of ZSM-5 was investigated,and then the influence of crystallization time,alkalinity and other factors on the synthesis of ZSM-5 molecular sieve was explored.On this basis,the amplification study was carried out.The main research contents are as follows:(1)The properties of silicon source will affect the preparation of molecular sieves.In this paper,the influence of two different silica gels on the synthesis of ZSM-5 was investigated.It found that in the range of Na2O/Si O2 = 0.05~0.07,although the hexagonal prisms of the sample prepared by Yuanxiang silica gel are obvious and the crystallinity is higher,but the SEM results shows that a small amount of mordenite is present;the product obtained by using Baishahe silica gel does not produce mordenite.Therefore,Baishahe silica gel is selected as the silicon source.(2)Crystallization time is the two key factors affecting the crystallinity and phase of the products.If the crystallization time is too short(10~15 h),the crystallinity of the product is low.If the time is too long(23~32 h),transcrystallization is likely to occur.(3)The pilot-scale study on the preparation of ZSM-5 of template-free system.The results show that: When Si O2/Al2O3 = 56,Na2O/Si O2 =0.09~0.11,the highest crystallinity of ZSM-5 product is only 72.60% in 1 L autoclave.Reducing the Si O2/Al2O3 ratio to 47.62,the product with good hexagonal prism morphology and relative crystallinity is increased to 90.40%.On this basis,an amplification experiment in 100 L autoclave was carried out,and ZSM-5 product with high crystallinity of 91.2% was obtained?2.As the silica gel production process not only consumes a large amount of water,but also generates a large amount of waste water,with the increasingly strict environmental protection requirements,some factories that are not environmentally friendly are closed,resulting in tight silicone products,in short supply,an unstable product performance.The process for producing white carbon black by precipitation method is stable,and the domestic production is large.Therefore,we consider the use of silica instead of silica gel to prepare ZSM-5 molecular sieve.In this paper,white carbon black was used as the silicon source.The effects of alkalinity and templating agent content on the synthesis of ZSM-5 molecular sieve were systematically investigated.The main research contents are as follows:(1)Induction effect of template dosage affects the formation of ZSM-5.It was found that when ZDA/Si O2 = 0.11,the morphology of the prepared product was circular and uniform,while ZDA/Si O2 = 0.14~0.20,the product showed a relatively stacked morphology.(2)The alkalinity of initial gel affects the morphology of ZSM-5products.The SEM results show that the particle size of ZSM-5 was non-uniform and aggregated when Na2O/Si O2 being 0.06 and 0.13.But the morphology of the prepared ZSM-5 molecular sieve was uniform when Na2O/Si O2 = 0.06~0.12.(3)The effect of the amplification effect on the synthesis of ZSM-5 wasinvestigated: when synthesized in a 1 L autoclave,it was found that the rotation speed of the reactor had an effect on the morphology of the prepared ZMS-5.When the rotation speed was 200 rpm,the resulting product was clustered and irregular.The prepared sample was uniform hexagonal shape,and the phenomenon of wall hanging can be suppressed when the rotation speed was increased to 300 rpm.