【作者】 刘斌；

【导师】 宋宝东；

【作者基本信息】 天津大学 ， 化学工程， 2014， 硕士

【摘要】 甲醇制汽油（MTG）是非石化法获得高辛烷值汽油的重要手段。MTG可部分消化我国现有甲醇过剩产能，又可减少对石油的依赖程度。提高ZSM-5分子筛在MTG反应中的甲醇转化率和汽油选择性、延长催化剂使用寿命是关键所在，对ZSM-5改性非常重要。分别用25、38、50、80四种不同硅铝比的ZSM-5分子筛催化MTG反应，实验结果表明，硅铝比为80的ZSM-5分子筛，汽油收率仅为15.8%，不适于作为反应催化剂。其余三种硅铝比的分子筛汽油收率基本相当，为46.2%-48.7%。从汽油组分中芳烃和均四甲苯含量分析，以硅铝比为50的分子筛为最优，在抗积碳失活能力方面，硅铝比越低，酸性越强，失活越快。用Fe₃O₄、CoO、CuO、ZnO四种过渡金属氧化物对硅铝比为25的ZSM-5负载改性，负载量3%。改性后的分子筛催化MTG结果表明，金属氧化物在ZSM-5表面形成L酸中心，用CuO改性后，L酸和B酸中心协同作用，汽油收率提高约10%，其中芳烃和均四甲苯含量同步提高约40%和60%。用ZnO改性后的分子筛表面分散性高，抗积碳失活能力强，反应24h，甲醇转化率由90%至65%（降幅25%），改性前为98%至54%（降幅44%）。以0.2M NaOH溶液对硅铝比为50的ZSM-5脱硅，制备了多级介孔分子筛。脱硅后比表面积、孔径、酸中心数量均增加。改性后，汽油收率提高37%，其中芳烃和均四甲苯分别提高12%和34%，汽油品质较低。抗积碳失活能力提高，反应24h，甲醇转化率由97%至91%（降幅6%），改性前为91%至78%（降幅13%）。用晶种诱导法合成了硅铝比为25的小晶粒ZSM-5，过程无模板剂，污染小、成本低，并用无定型硅铝酸盐改性，改性后分子筛比表面积大、酸性适中，催化MTG反应结果表明，适宜的反应条件为：温度380-420℃，压力1MPa，甲醇质量空速1-5h-1。改性后的小晶粒ZSM-5，相同条件下反应6h，汽油收率提高28%，其中芳烃和均四甲苯分别提高30%和11%，汽油品质较高。从抗积碳失活能力角度分析，反应24h，甲醇转化率由99%至70%（降幅29%），与负载ZnO改性的分子筛基本相当。更多还原

【Abstract】 Methanol to gasoline （MTG） is an important non-petrochemical route for producinghigh octane number gasoline. MTG can not only make good use of the over-producedmethanol but also reduce the dependence on oil for gasoline production. Increasingmethanol conversion, improving gasoline selectivity and prolonging life-span of thecatalyst zeolite ZSM-5are the key for commercialization. Therefore, modification ofzeolite ZSM-5to improve its catalytic performances is of great importance.Four ZSM-5zeolites with different Si/Al ratios （25,38,50and80） were used tocatalyze the MTG reaction, respectively. The gasoline yield reached only15.8%whenthe Si/Al ratio was80, indicating that this zeolite is not suitable for catalyzing theMTG reaction. The other three zeolites gave almost the same gasoline yields（46.2-48.7%）. Based on the aromatics and durene contents in the gasoline products,the optimal Si/Al ratio of the catalysts was found to be50. In terms of the anti-cokedeactivation capability, the zeolite with a lower Si/Al ratio has a stronger acidity anddeactivates faster.Four transition metal oxides （Fe₃O₄, CoO, CuO and ZnO） were loaded （3%） on thezeolite ZSM-5with a Si/Al ratio of25to modify the catalyst. The MTG reactionscatalyzed by the modified zeolites showed that metal oxides formed an L acid site onthe surface of ZSM-5. After modification with CuO, the L and B acid sitessynergistically acted increasing the gasoline yield by ca10%. The aromatics anddurene contents were also increased by ca40%and60%, respectively. The zeolitemodified by ZnO showed a high surface dispersion and strong capability ofanti-carbon deactivation. After24h’s MTG reaction, the methanol conversion reducedto from90%to65%（25%reduction）, compared to98%to54%（44%reduction）when the unmodified catalyst was used.Mesoporous multistage zeolite was prepared by desilication of ZSM-5with a Si/Alratio of50using0.2M NaOH. The specific surface area, pore size and number of acidsites of the modified zeolite were all increased. The gasoline yield was increased by37%, the aromatics and durene contents were increased by12%and34%, respectively,giving a lower quality of gasoline product. The anti-coke deactivation capability wasincreased. After24h’s reaction, the methanol conversion reduced from97%to91%（6%reduction）, compared to91%to78%（13%reduction） before the modification of the catalyst.Small crystal size of ZSM-5with a Si/Al ratio of25was prepared by the seedcrystal inducing method. This process has the advantages of no template agent, lowpollution and low cost. After further modification of the catalyst with amorphousaluminosilicate, large surface area and moderate acidity were achieved. The optimalreaction conditions for the MTG reaction catalyzed by the modified catalyst were:380-420℃,1MPa, WHSV of methanol1-5h-1. After6h’s MTG reaction catalyzed bythe modified small crystal size of ZSM-5, the gasoline yield was increased by28%,the aromatics and durene contents were increased by30%and11%, respectively,compared to those catalyzed by the unmodified catalyst, giving a higher quality ofgasoline product. In terms of the anti-coke deactivation capability, after24h’sreaction, the methanol conversion reduced from99%to70%（29%reduction）, whichis quite similar to that of the ZnO-loaded zeolite.更多还原