流化床反应器中甲醇制烯烃反应性能分析

Performance analysis of methanol to olefins process in fluidized bed reactor

关键词:  甲醇制烯烃  流化床  SAPO-34  温度  水醇比 

Key words:  methanol to olefins  fluidized bed reactor  SAPO-34  temperature  water/methanol

摘要:

对传统固定流化床反应器进行了必要的改进,将固定流化床反应器拓展应用到甲醇制烯烃反应研究中。通过调整预热温度及更换下行进料管材质,使甲醇在与催化剂接触前的分解几率降到最低。装置平行性及物料平衡考察结果表明,该反应器数据重复性良好,物料平衡可达到97％。采用SAPO-34分子筛催化剂,在固定流化床反应器中分别考察了反应温度和水醇比(质量比)对甲醇制烯烃主要反应产物分布的影响。温度实验结果表明:甲醇转化率接近于100％,反应温度的提高可大大提高乙烯的选择性,C=₂～C=₄选择性可达到90％以上；同时温度的升高使得催化剂上积炭速率增快；对于以乙烯为主要目的产物的甲醇制烯烃工艺,建议将反应温度选择为500 ℃,C=₂/C=₃摩尔比可稳定在1.5左右；若以丙烯为主要目的产物,建议将反应温度选择在450～470 ℃之间,C=₂/C=₃摩尔比可稳定在0.9～1.1之间。水醇比实验结果表明:水不但可以延缓催化剂的积炭速率,而且还可以大大增加乙烯的选择性,较大的水醇比可以将C=₂/C=₃摩尔比提高到2.0以上；无论是期望乙烯为主要目的产物还是丙烯为主要目的产物,太大的水醇比会增加能耗,增大反应器及产物分离器的负荷,所以,建议将水醇比都选择在0.25～0.5之间。 

Abstract:

The flow fluidized bed reactor was applied to methanol-to-olefins research after some necessary improvements of traditional fixed flow bed reactor. Methanol decomposition probability before contacting the catalysts could be decreased to the lowest level by adjusting the pre-heater temperature and changing the material of descending feed pipe. The results of device repeatability and material balance investigation showed this reactor had good data repeatability and could achieve 97% of mass balance. The experiments about the effect of reaction temperature and water/methanol mass ratio on main products distribution were carried out based on the SAPO-34 molecular sieve catalysts. The results of temperature experiments showed the temperature increase improved the ethylene selectivity greatly. As well as speed up the coke formation, the methanol conversion was almost 100%, and the C=₂~C=₄ selectivity could be over 90%. For ethylene as main product, the reaction temperature was suggested to choose 500 ℃ with C=₂/C=_3molar ratio of 1.5. For propylene as main product, the reaction temperature of 450~470 ℃should be chosen with C=₂/C=₃ molar ratio of 0.9~1.1. The results of water/methanol mass ratio experiment showed that increasing the water content could not only delay the coke formation rate, but also increase the ethylene selectivity remarkably, which could put the C=₂/C=_3molar ratio up to more than 2.0. Too much water would increase the energy consume and the load of reactor and products separator unavoidably no matter for ethylene or propylene as main products. Therefore, water/methanol mass ratio of 0.25~0.5 was advocated.