【作者】 吕金钊；

【导师】 王新平；

【作者基本信息】 大连理工大学 ， 物理化学， 2009， 硕士

【摘要】 甲醇制低碳烯烃（methanol to olefins,简称MTO）解决了由于石油短缺而导致的低碳烯烃缺乏的难题,因而引起了世界各国的广泛关注。对于MTO反应,性能优异的催化剂是该项研究的核心。SAPO-34分子筛以其高甲醇转化率和高乙烯、丙烯的生成选择性成为目前MTO反应最好的催化剂。但是,做为一种微孔沸石材料,SAPO-34在反应过程中极易因积碳堵塞孔道而造成催化剂的快速失活。因此,如何提高MTO反应过程中催化剂抗积炭失活的能力,从而延长催化剂的寿命以降低催化剂的再生频度,是MTO反应亟待解决的问题。为此,本论文进行了以下几个方面的研究,所得的结果为:（1）分别采用固态离子交换法和液态离子交换法将稀土金属镧（La）和钇（Y）引入到SAPO-34中,制得了La、Y改性的SAPO-34催化剂,并将其用于MTO催化反应。结果发现,液态离子交换改性后的SAPO-34与母体分子筛相比,其催化性能没有明显改变,而固态离子交换改性后的SAPO-34上催化剂的寿命和低碳烯烃的选择性得到了显著改善。在评价的反应条件下,固态离子交换法改性的3%Y-SAPO-34-S催化剂上,因甲烷的生成得到了更好的抑制,催化剂的寿命达到了185分钟（比母体SAPO-34延长了近30分钟）;C₂⁼-C₄⁼的选择性达到了95%（比在SAPO-34提高了近5个百分点）。（2）借助于XRD、FT-IR、N₂等温吸附/脱附、UV-Vis-DRS、XRF以及ICP表征手段对改性后SAPO-34的结构进行了研究。结果表明,在固态离子改性后的SAPO-34中,稀土离子取代了骨架AlO₄四面体中的Al进入了分子筛的骨架,而在液态离子交换的SAPO-34中,稀土离子很少存在。因此,可以认为,上述固态离子交换法改性的SAPO-34所给出的优越的催化性能,是由于稀土离子进入了分子筛骨架所致。（3）在连续流动固定床反应系统,考察了反应温度、甲醇进料空速、水醇比和稀土离子的含量等因素对固态离子交换法改性催化剂抗积炭失活能力的影响,优化了反应条件。得出了下述最佳反应条件:反应温度为450℃,甲醇的质量空速是2h^-1,水醇摩尔比为5:1。（4）本论文还考察了用固态离子交换法改性所得3%Y-SAPO-34-S催化剂的再生性能。结果表明,催化剂经三次再生后,无论是催化剂的寿命还是甲醇的转化率都与相应新鲜的催化剂非常接近。这说明该改性催化剂具有良好的再生性能。更多还原

【Abstract】 Catalytic conversion of methanol to olefins （called MTO reaction） has been the subject that received a global particular concern, as it may resolve the problem of the deficiency of light olefins caused by the shortage of petroleum. The key issue for the MTO reaction is to develop a new catalyst with excellent catalytic performance. SAPO-34 molecular sieve has turned out to be a superior catalyst for the MTO reaction, due to its high activity for the reaction and high selectivity to ethylene and propylene. Nevertheless, as a micropore zeolite material, SAPO-34 is known to suffer rapid deactivation due to coke deposition during the MTO reaction, which leads to the serious decrease in activity and selectivity of the zeolite towards the aimed reaction. Consequently, how to reduce the coke formation over the zeolite so as to reduce the regeneration frequency of the catalyst is a subject that is urgently required to be solved for the practical application of MTO reaction. Thus, the following research work in our investigations was carried out and the obtained results were described below:（1） SAPO-34 was successfully modified by rare earth metals （La or Y） in solid state ion exchange or liquid-phase ion exchange methods. The MTO reaction results indicated that the Re-SAPO-34-L catalysts, which were prepared by the modification of SAPO-34 with the rare earth metals in liquid-phase ion exchange method, behaved no different catalytic performance from that of SAPO-34. However, the Re-SAPO-34-S catalysts, which were prepared by the modification of SAPO-34 with the rare earth metals in solid state ion exchange method, gave substantially improved catalytic performance compared with that of the parent SAPO-34. Under the reaction conditions, the lifetime of the Re-SAPO-34-S catalysts was significantly prolonged and the selectivity to the aimed products was largely increased. For example, the lifetime of the 3%Y-SAPO-34-S catalyst reached 185 minutes that was ca. 30 minutes longer than that of the parent SAPO-34, and the selectivity to C₂⁼-C₄⁼ over the catalyst increased to 95 % that was absolutely ca. 5% higher than that over SAPO-34. The improved catalytic performance over the 3%Y-SAPO-34-S catalyst can be correlated well with the distinct suppression of methane production in the reaction.（2） The structures of modified SAPO-34 catalysts were studied by means of XRD, FT-IR, BET, UV-vis-DRS, XRF and ICP. The results confirmed that rare earth metal ions in the solid-state ion exchanged samples had incorporated into the zeolite framework （substituted Al in the AlO₄ tetrahedron）, whereas they rarely existed there for the liquid-phase ion exchanged samples. Therefore, the modified catalytic performance for the Re-SAPO-34-S catalysts can be reasonably attributed to the incorporation of rare earth metal ions into the zeolite framework.（3） The lifetime of the Re-SAPO-34-S catalysts, which was influenced by the reaction temperature, methanol weight hourly space velocity, molar ratio of methanol to water in the feed as well as the amount of rare earth metal in the catalyst, was investigated in the continuous flowing fixed bed reaction system. In terms of the lifetime of the catalyst, the optimum reaction conditions proposed in this paper are as follows: the reaction temperature is 450℃,the methanol weight hourly space velocity is 2 h^-1 and the molar ratio of methanol to water is 1:5.（4） The reproducibility of the 3%Y-SAPO-34-S catalyst for catalyzing the MTO reaction was also studied. It showed that the catalytic performance of the regenerated catalyst after 3 times changed little compared with the fresh one in terms of the lifetime and the conversion of methanol obtained over the catalyst.更多还原