ZnAPO -11 分子筛的合成及催化裂解反应性能研究

采用静态水热法, 在活性胶液中各组分摩尔比为n(R)/ n(ZnO)/ n(Al2O3)/ n(P2O5)/ n(H2O)=1 ∶ x ∶y ∶1.1∶80 (0.5x +y =1)的条件下合成了具有不同锌含量的锌铝磷酸盐分子筛(ZnAPO -11), 利用XRD, SEM , N2 吸附, MAS -NMR 及ICP-AES 等方法对合成的ZnAPO -11 分子筛进行了表征。结果表明, 当0 ≤n (ZnO)/n(Al2O3) ≤0 .04 时, 可以合成出具有AEL 结构类型的ZnAPO -11 分子筛, 样品具有较高的结晶度和纯 度;晶体形貌均匀, 呈长条形;锌同晶取代了AlPO4 -11 分子筛上的骨架铝。以正己烷为模型底物, 评价了合成的 ZnAPO-11 分子筛的催化裂解反应活性, 研究结果显示ZnAPO -11 在475 ～ 550 ℃具有反应活性, 其中正己烷的转 化率随接触时间的增加而增加, 反应的表观速率常数随反应温度的升高而增加;正己烷在ZnAPO -11 分子筛上的 催化裂解反应的速率方程中的正己烷浓度项反应级数为1, 表观速率常数与反应温度间的关系可用Arr henius 公式 表示。

Synthesis and Catalytic Cracking Performance of ZnAPO-11 Molecular Sieves

Zinc- substituted aluminophosphate molecular sieves （ZnAPO- 11） containing different zinc contents were synthesized using the gel composition n（R）/n（ZnO）/n（Al2O3）/n（P2O5）/n（H2O）=1： x ： y ： 1.1 ： 80 （0.5x＋y=l） by static hydrothermal method. As- synthesized ZnAPO- 11 molecular sieves were characterized by XRD, SEM, N2- adsorption, MAS NMR and ICP--AES techniques. The results show that ZnAPO--11 molecular sieves with AEL topology are prepared in the range of 0≤n（ZnO）/n（Al2O3 ）≤0.04. And resultant ZnAPO-11 molecular sieves are of high crystallinity and purity. A regular platelet morphology is observed for the as--synthesized ZnAPO--11 molecular sieves. Experimental data show that Zn as heteroatom is successfully incorporated into the framework of AlPO4 -- 11 and substituted for Al. The n- hexane cracking over ZnAPO--11 was examined under different reaction conditions. It is found that ZnAPO--11 molecular sieves exhibited a significant activity for the n--hexane cracking at 475-550 ℃. Conversion level of n--hexane increased with increasing contact time, and the apparent rates increased with increasing reaction temperature. The first order was determined of the n--hexane concentration. In addition, the dependence of the rates on reaction temperature can be expressed in terms of Arrhenius formula in the whole cracking temperature range.