Extruded SAPO-34 Catalyst For Methanol-to-olefin Reaction-synthesis And Catalytic Performance

Based on the laboratory-made SAPO-34 molecular sieve powder,the article studied the influence of extrusion molding conditions on the performance of granular catalysts,in order to obtain the most suitable SAPO-34 molecular sieve forming conditions,using means that MTO reaction,catalyst strength,NH3-TPD,BET,and so on.In this paper,single-factor experiments were used to study the effect of conditions on SAPO-34 catalyst performance,such as the ratio of water/powder,the kind and content of binder,peptizer,extrusion aid,pore-enlarging agent,and baking temperature.The results are as follows:(1)SAPO-34 shaped catalyst generally has strong acid and weak acid,and there are multi-level pore structures of micropores and mesopores.(2)The ratio of water/powder and the content of SB powder had great influence on the extrusion process.When the ratio of water/powder is less than 0.6,the extrusion is difficult;when it is greater than 0.9,the material holding rod is serious.When the content of SB powder is small,the material is easy to hold the rod;when it is more than 85%,the material extrusion is difficult.(3)For the catalyst strength.The kinds of binders and peptizers had great influence,about binders:SB powder>silica sol;about peptizers:inorganic acid>organic acid>polyols;the kind of extrusion aids had little effect(oxalic acid>Sesbania + oxalic acid>Sesbania);with the increase of the ratio of water/powder,nitric acid,and calcination temperature,the catalyst trength first increases and then decreases;with the increase of SB powder content,the catalyst strength monotonously increases;the content of sesbania powder is almost no impact;The addition of pore-enlarging agent reduces the catalyst trength in a certain extent.(4)For the catalytic performance.The nitric acid in the peptizers is the best,and the sesbania in the extrusion aids is optimal;when 0.8>water/powder>0.6,The larger of the ratio of water/powder,the better of the catalytic performance;when the content of SB powder is small,the difference of catalytic performance is not significant,but when it increased to a certain extent,the catalytic performance decreased significantly;there is an optimal value of the content of nitric acid,sesbania and the calcination temperature;the addition of the pore-enlarging agent fails to improve the catalytic performance.(5)Suitable molding conditions:the ratio of water/powder is 0.8,the content of SB is 65%,the content of nitric acid is 7%,the content of sesbania is 2%,calcination temperature is 550 ?.Under this condition,the life time is 4h(The methanol conversion hold 100%),the C2 +C3-yield is 88.82%,the ethylene yield is 54.95%,among that,the propylene yield is 33.87%,and the ratio of ethylene/propylene is 1.622.Under the same conditions,the evaluation result of SAPO-34 powder catalyst is:the life time is 8.5 h(The methanol conversion hold 100%),the C2=+C3= yield is 89.09%,and the ratio of ethylene/propylene is 1.683;the C2=+C3= yield and the ratio of ethylene/propylene of the molded catalyst are similar to those of the powder,but the lifetime is significantly lower than that of the powder catalyst.The main reason is attributed to the decrease of the active center of particle catalyst caused by carbon deposition inactivation faster than that of powder catalyst,and suitable pore matching will be an important work for subsequent molding research.Based on the SAPO-34 molded catalyst made under the suitable molding conditions,the article get the optimum MTO process conditions:normal pressure,450? and water/alcohol ratio 2:1.