Study On The Manufacture Of SAPO-n Molecule Sieve And Its Use In MTO Process

Methanol-to-Olefins (abbr. MTO) is the most hopeful technology that substitute for the way of petroleum-to-olefins. The core is the catalyst. In this article, it was analyzed that the current domestic and overseas researches of MTO catalyst. Several kinds of different zeolite molecule sieve catalyst, such as the SAPO-34, etc, were studied. Finally, we detect a homologous series catalyst SAPO-n with SAPO-34.Using the same raw materials, manufacture method as SAPO-34, we replicated the SAPO molecule sieve catalyst in the high-pressure autoclave without polytetrafluoroethylene lining. Then they were compared with SAPO-34. Their catalysis performances were tested in the fixed bed reactor. In 19 samples being tested, 12 kinds could catalyze the react. These 12 samples were characterized adopting XRD diffraction, specific surface area, differential thermal analysis, etc. Through the comparison with other kinds of molecular sieve catalyst, their uniqueness was confirmed and they were temporarily named SAPO-n.In the investigation of the process conditions, the influence of reaction temperature, feed mode, WHSV, raw materials ratio were discussed. The optimum process condition selected are as follows: reaction temperature 380℃, molar feed ratio:CH₃OH:H₂O=1 :5, WHSV=3.5hr^-1, intermittence feed, washing the reactor with nitrogen after taking a gas product and before feed again each time. Under the optimum process conditions, using SAPO-n, in gas product, the content of ethylene is 83.07%, propylene is 3.33%, the sum is 86.40%.This article has also described the life-span experiment. The result demonstrated that the life span of SAPO-n is very short too. It is only about one hour. And the good performance of the fresh catalyst could not be got after regeneration.In brief, the development of SAPO-n is still at primary stage. It remains to improve in some aspects, such as course, process conditions, life span, etc.