Synthesis And Characterization The Lamellar SAPO-34 Molecular Sieve And Its Catalytic Performance In The MTO Reaction

With the rapid development of petrochemical industry,the demand of basic chemical raw materials(ethylene,propylene)has a substantial increasing.The source of ethylene and propylene mainly rely on naphtha cracking technology at home and abroad,this route relies too much on oil.As the shortage of oil resources and prices rise,the production of ethylene and propylene will be severely limited.Methanol to olefin process is converting methanol which is synthetic by coal to low carbon olefin.This technology can solve the problem of shortage of ethylene and propylene,and conforms to the situation of energy distribution in China.The MTO process has good economic benefit,and is a key development projects at home.As the MTO catalyst,SAPO-34 molecular sieves may inactivate rapidly because of the carbon deposition,and it has obvious induction period in the MTO reaction.In the MTO reaction,the lamellar SAPO-34 molecular sieve has a shorter diffusion path.The carbon deposit formation rate was reduced,because of the low carbon hydrocarbons can spread out quickly.Thus it has a longer lifetime.When produce the molecular sieve,it will produce a lot of mother liquors.Many unreacted raw materials were contained in mother liquor.It will cause not only the waste of raw materials-increase the cost of production,also cause a series of environmental problems when discharged the liquid directly.In this paper,SAPO-34 molecular sieve was synthesized by using the mother liquor.This method not only solves the using of mother liquor,also obtain the lamellar SAPO-34 molecular sieve.Although the SAPO-34 molecular sieve is considered to be the best catalyst for MTO reaction,but the poor mechanical strength and small particle size,which make it do not suitable for circulating fluidized bed technology.This paper adopted SAPO-34 molecular sieve with different morphology to spray drying.The study found that the lamellar SAPO-34 molecular sieve has a longer lifetime than the cubic one,and the low carbon olefin selectivity increase quickly,thus the olefin yield is higher also.This paper mainly does the following work:1.The particle size and the morphology ware inspected when synthesis SAPO-34 molecular sieve using different composite template.The quantity of seed solution was inspected to research the influence to the morphology of SAPO-34.The lamellar SAPO-34 molecular sieve with different SiO2/Al2O3 ratio was synthesized by adding seed solution.The crystallization process of SAPO-34 molecular sieve with seed solution was studied.The result shows that the samples with layered structure are more likely to obtain the lamellar SAPO-34 molecular sieve after adding seed solution,the amount of acid and the acid strength are enhanced.With the increase of SiO2/Al2O3 molar ratio,the weak acid hasn't changed obviously,but the strong acid increased visibly.The MTO reaction result shows that the suitable SiO2/Al2O3 ratio is in the range of 0.15?0.2.2.The mother liquor of SAPO-34 molecular sieve was used for synthesis of SAPO-34 molecular sieve,and explored the recycle of mother liquor.The result shows that the lamellar SAPO-34 molecular sieves were synthesized by using the microcrystalline in mother liquor as seed.The MTO reaction result shows that the carbon deposition rate of the lamellar SAPO-34 molecular sieve is lower than the cubic one.The mother liquor can be used within the limited numbers.3.Finally,MTO catalyst was prepared by the SAPO-34 molecular sieve with different morphology,and the physical properties,hydrothermal stability,MTO reaction performance were investigated.The result shows that the physical property indexes are the same.The catalyst prepared by the lamellar SAPO-34 molecular sieve has a longer lifetime.The lifetime and the low carbon olefin selectivity were reduced after hydrothermal aging.