SAPO-34和SAPO-44分子筛上吸附甲醇的TPSR-MS研究

 采用程序升温表面反应-质谱(TPSR-MS)和程序升温脱附(TPD)技术考察了SAPO-34和SAPO-44分子筛表面的酸性与其催化甲醇转化为低碳烯烃性能的关系. 结果表明,SAPO分子筛表面存在两种活性中心,这两种活性中心与分子筛表面不同的酸性中心相对应. 表面吸附的甲醇在不同强度的酸性中心上进行不同的反应,在弱酸中心上主要进行甲醇脱水生成二甲醚的反应,在强酸中心上主要进行二甲醚进一步转化为低碳烯烃的反应. 同时,探讨了SAPO分子筛表面的酸强度对低碳烯烃生成温度的影响.

TPSR-MS Study of Adsorbed Methanol over SAPO-34 and SAPO-44 Molecular Sieves

Temperature-programmed surface reaction-mass spectrometry (TPSR-MS) and temperature-programmed desorption (TPD) techniques were used to study the relationship between the catalytic activity of SAPO-34 and SAPO-44 molecular sieves for methanol to olefin (MTO) reaction and their acidity. The result showed that there were two kinds of active sites on SAPO-34 and SAPO-44 molecular sieves, which were corresponding to the acidic sites with different strength on the molecular sieves. The adsorbed methanol underwent different reactions on different acidic sites. Methanol converted to dimethyl ether on the weak acidic sites, and light olefins were formed mainly from the adsorbed dimethyl ether on the strong acidic sites. The effect of the acid site strength on the light olefin formation temperature was also elucidated.