SAPO-18分子筛上二甲醚制低碳烯烃的催化性能研究
Catalytic Performances of Dimethyl Ether to Olefins over SAPO-18 Molecular Sieves

在固定床反应器上考察了SAPO-18和金属改性的SAPO-18分子筛催化剂上二甲醚制低碳烯烃反应的催化性能。结果表明，金属改性的SAPO-18分子筛结晶度较高。催化反应的最佳反应温度为400℃，最佳空速为DME/N2为10/100 ml/min。在该反应条件下，SAPO-18和RE-SAPO-18上丙烯的选择性总是高于乙烯。金属镍和稀土镧改性的分子筛Ni-SAPO-18和La-SAPO-18的催化性能最好，而稀土铈的添加却降低了SAPO-18的催化活性。在最佳反应条件下，Y-SAPO-18催化剂上DME的转化率达到99.3%，乙烯的选择性达到26.8%，丙烯的选择性为35.0%。
The catalytic performance of pure-phase and rare-earth modified silicoaluminophosphate molecular sieves with AEI structures were investigated by dimethyl ether to olefins (DTO) reactions. It demonstrated that the crystallinity of metal modified SAPO-18 molecular sieves is high. For the catalytic reaction, the optimum space velocity is DME/N2 = 10/100 ml/min. Under these conditions, the selectivity toward propylene is always much higher than that of ethylene in both SAPO-18 and RE-SAPO-18 used as catalysts. Moreover, the modification of SAPO-18 by Ni and La improved the catalytic activity, while the modification by Ce has a reverse effect. The catalytic activity and stability were signify- cantly enhanced especially for RE-SAPO-18. The medium acid strength, which was attained in SAPO-18 catalyst, can catalyze DTO reaction more efficiently for improving catalyst lifetime and product selectivity. At the optimum condi- tions, Y-SAPO-18 catalyst gave a DME conversion of 99.3%, together with selectivity to ethylene of 26.8% and pro- pene of 35.0%.