La2O3协同增强SAPO-34的二甲醚制烯烃催化性能

La₂O₃不需要与SAPO-34接触，便可显著延长SAPO-34的二甲醚制烯烃（DTO）反应寿命，并且La₂O₃与SAPO-34比例越大，SAPO-34的反应寿命越长。当La₂O₃和SAPO-34的质量比为1：1时，SAPO-34寿命提高了约1倍。进一步的研究表明，只有当La₂O₃层夹在SAPO-34层中间时，才能提高SAPO-34的寿命，La₂O₃无论是处于SAPO-34上游还是下游，均不能提高SAPO-34的寿命。动力学和催化剂的积炭量研究表明，La₂O₃是通过降低SAPO-34的积炭速度提高其反应寿命的。初步提出了La₂O₃提高SAPO-34寿命的机理：在DTO反应过程中，二甲醚在SAPO-34分子筛上形成一种积炭前体，这种积炭前体转移到La₂O₃的表面上，反应生成不能积炭的化合物（CO、CO₂和H₂等），从而降低了SAPO-34的积炭失活速度，提高了其寿命。

La2O3synergetic effect to improve catalytic performance of SAPO-34 molecular sieve used for dimethyl ether to olefins reaction

The working lifetime of SAPO-34 for dimethyl ether to olefins (DTO) reaction was increased by non-contact La₂O₃. Increasing ratio of La₂O₃ to SAPO-34 prolonged working lifetime of SAPO-34. When the mass ratio of La₂O₃ to SAPO-34 was 1:1, the working lifetime of SAPO-34 was almost twice as much as that of SAPO-34 alone. La₂O₃ sandwiched in SAPO-34 had improvement, whereas La₂O₃ in upstream and downstream of SAPO-34 did not. Reaction kinetics and coke amount on SAPO-34 indicated that La₂O₃ decreased coking rate of SAPO-34. A synergetic mechanism for SAPO-34 and La₂O₃ was proposed that a coke precursor created on SAPO-34 during DTO was converted to non-coke forming species (such as CO, CO₂ and H₂) upon traveling onto La₂O₃ surface such that SAPO-34 coking rate was decreased and its working lifetime was increased.